#!/bin/sh
# shellcheck source=/dev/null
#
# Simple package manager written in POSIX shell for https://kisslinux.xyz
#
# The MIT License (MIT)
#
# Copyright (c) 2019-2021 Dylan Araps
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

log() {
    printf '%b%s %b%s%b %s\n' \
        "$c1" "${3:-->}" "${c3}${2:+$c2}" "$1" "$c3" "$2" >&2
}

war() {
    log "$1" "$2" "${3:-WARNING}"
}

die() {
    log "$1" "$2" "${3:-ERROR}"
    exit 1
}

contains() {
    # Check if a "string list" contains a word.
    case " $1 " in *" $2 "*) return 0; esac; return 1
}

prompt() {
    [ "$1" ] && log "$1"

    log "Continue?: Press Enter to continue or Ctrl+C to abort"

    # korn-shell does not exit on interrupt of read.
    [ "$KISS_PROMPT" = 0 ] || read -r _ || exit 1
}

as_root() {
    case $uid/${user:=root}/${cmd_su##*/} in
        0/root/*)
            "$@"
        ;;

        */doas|*/sudo|*/ssu)
            log "Using '$cmd_su' (to become $user)"
            "$cmd_su" -u "$user" -- "$@"
        ;;

        */su)
            log "Using 'su' (to become $user)"
            printf 'Note: su will ask for password every time.\n%s\n' \
                   '      Use doas, sudo or ssu for more control.'
            "$cmd_su" -c "$* <&3" "$user" 3<&0 </dev/tty
        ;;

        *)
            die "Invalid KISS_SU value: '$cmd_su' (valid: doas, sudo, ssu, su)"
        ;;
    esac

    unset user
}

file_owner() {
    # Intentional, globbing disabled.
    # shellcheck disable=2046
    set -- $(ls -ld "$1")

    user=${3:-root}

    id -u "$user" >/dev/null 2>&1 || user=root
}

pkg_owner() {
    set +f

    [ "$3" ] || set -- "$1" "$2" "$sys_db"/*/manifest

    pkg_owner=$(grep "$@")
    pkg_owner=${pkg_owner%/*}
    pkg_owner=${pkg_owner##*/}

    set -f

    [ "$pkg_owner" ]
}

run_hook() {
    # Provide a default post-build hook to remove files and directories
    # for things we don't support out of the box. One can simply define
    # their own hook to override this behavior.
    case ${KISS_HOOK:--}$1 in
        -post-build)
            rm -rf "$3/usr/share/gettext" \
                   "$3/usr/share/polkit-1" \
                   "$3/usr/share/locale" \
                   "$3/usr/share/info"
        ;;

        [!-]*)
            TYPE=${1:-null} PKG=${2:-null} DEST=${3:-null} . "$KISS_HOOK"
        ;;
    esac
}

decompress() {
    case $1 in
        *.bz2)      bzip2 -d ;;
        *.lzma)     lzma -dc ;;
        *.lz)       lzip -dc ;;
        *.tar)      cat      ;;
        *.tgz|*.gz) gzip -d  ;;
        *.xz|*.txz) xz -dcT0 ;;
        *.zst)      zstd -dc ;;
    esac < "$1"
}

sh256() {
    # There's no standard utility to generate sha256 checksums.
    # This is a simple wrapper around sha256sum, sha256, shasum,
    # openssl, digest, ... which will use whatever is available.
    #
    # All utilities must match 'sha256sum' output.
    #
    # Example: '<checksum>  <file>'
    hash=

    if [ ! -d "$1" ] && [ -e "$1" ]; then
        hash=$(
            sha256sum               "$1" ||
            sha256 -r               "$1" ||
            openssl dgst -sha256 -r "$1" ||
            shasum -a 256           "$1" ||
            digest -a sha256        "$1"
        ) 2>/dev/null || die "Failed to generate checksums for '$1'"

        hash=${hash%% *}
        printf '%s\n' "$hash"
    fi
}

pkg_lint() {
    log "$1" "Checking repository files"

    pkg_find_version "$1"
    cd "$repo_dir"

    [ "$repo_rel" ] ||
        die "$1" "Release field not found in version file"

    [ -x build ] ||
        die "$1" "Build file not found or not executable"

    [ -f sources ] ||
        war "$1" "Sources file not found"
}

pkg_find_version() {
    pkg_find "$1"

    read -r repo_ver repo_rel < "$repo_dir/version" ||
        die "$1" "Failed to read version file ($repo_dir/version)"
}

pkg_find() {
    # Figure out which repository a package belongs to by searching for
    # directories matching the package name in $KISS_PATH/*.
    set -- "$1" "$2" "$3" "${4:-"$KISS_PATH"}"
    IFS=:

    # Iterate over KISS_PATH, grabbing all directories which match the query.
    # Intentional.
    # shellcheck disable=2086
    for _find_path in $4 "${3:-$sys_db}"; do set +f
        for _find_pkg in "$_find_path/"$1; do
            test "${3:--d}" "$_find_pkg" && set -f -- "$@" "$_find_pkg"
        done
    done

    unset IFS

    # A package may also not be found due to a repository not being readable
    # by the current user. Either way, we need to die here.
    [ "$5" ] || die "Package '$1' not in any repository"

    # Show all search results if called from 'kiss search', else store the
    # value in a variable.
    [ "$2" ] && { shift 4; printf '%s\n' "$@"; } || repo_dir=$5
}

pkg_list() {
    # List installed packages. As the format is files and directories, this
    # just involves a simple for loop and file read.

    # Optional arguments can be passed to check for specific packages. If no
    # arguments are passed, list all.
    [ "$1" ] || { set +f; set -f -- "$sys_db"/*; }

    # Loop over each package and print its name and version.
    for _list_pkg do
        _list_pkg=$sys_db/${_list_pkg##*/}

        [ -d "$_list_pkg" ] || {
            log "${_list_pkg##*/}" "not installed"
            return 1
        }

        read -r version 2>/dev/null < "$_list_pkg/version" || version=null
        printf '%s\n' "${_list_pkg##*/} $version"
    done
}

pkg_cache() {
    # Find the tarball of a package using a glob. Use the first found match
    # of '<pkg_name>@<pkg_version><pkg_release>.tar.*'.
    pkg_find_version "$1"

    set +f
    set -f -- "$bin_dir/$1@$repo_ver-$repo_rel.tar."*
    tar_file=$1

    [ -f "$1" ]
}

pkg_source_resolve() {
    # Given a line of input from the sources file, return an absolute
    # path to the source if it already exists, error if not.
    set -- "$1" "${2%"${2##*[!/]}"}" "${3%"${3##*[!/]}"}" "$4"

    if [ -z "${2##\#*}" ]; then
        _res=

    # Git repository.
    elif [ -z "${2##git+*}" ]; then
        _res=$2

    # Remote source (cached).
    elif [ -f "$src_dir/$1/${3:+"$3/"}${2##*/}" ]; then
        _res=$src_dir/$1/${3:+"$3/"}${2##*/}

    # Remote source.
    elif [ -z "${2##*://*}" ]; then
        _res=url+$2
        _des=$src_dir/$1/${3:+"$3/"}${2##*/}

    # Local relative dir.
    elif [ -d "$repo_dir/$2" ]; then
        _res=$repo_dir/$2/.

    # Local absolute dir.
    elif [ -d "/${2##/}" ]; then
        _res=/${2##/}/.

    # Local relative file.
    elif [ -f "$repo_dir/$2" ]; then
        _res=$repo_dir/$2

    # Local absolute file.
    elif [ -f "/${2##/}" ]; then
        _res=/${2##/}

    else
        die "$1" "No local file '$src'"
    fi

    [ "$4" ] || printf 'found %s\n' "$_res"
}

pkg_source() {
    # Download any remote package sources. The existence of local files is
    # also checked.
    pkg_find "$1"

    # Support packages without sources. Simply do nothing.
    [ -f "$repo_dir/sources" ] || return 0

    log "$1" "Checking sources"
    mkdir -p "$src_dir/$1" && cd "$src_dir/$1"

    while read -r src dest || [ "$src" ]; do
        pkg_source_resolve "$1" "$src" "$dest" "$2"

        case $_res in url+*)
            log "$1" "Downloading $src"
            mkdir -p "$PWD/$dest"

            curl -fLo "$_des" "$src" || {
                rm -f "$_des"
                die "$1" "Failed to download $src"
            }
        esac
    done < "$repo_dir/sources"
}

pkg_extract_tar_hack() {
    # This is a portable shell implementation of GNU tar's
    # '--strip-components 1'. Use of this function denotes a
    # performance penalty.
    decompress "$2" > "$tmp_dir/ktar" ||
        die "$1" "Failed to decompress $2"

    tar xf "$tmp_dir/ktar" ||
        die "$1" "Failed to extract $2"

    # Iterate over all directories in the first level of the
    # tarball's manifest.
    tar tf "$tmp_dir/ktar" | while IFS=/ read -r dir _; do
        # Some tarballs contain './' as the top-level directory,
        # we need to skip these occurances.
        [ -d "${dir#.}" ] || continue

        # Move the directory to prevent naming conflicts between
        # the child and parent.
        mv -f "$dir" "$pid-$dir"

        # First attempt to move all files up a directory level,
        # if any files/directories fail (due to mv's lack of
        # directory merge capability), simply do the exercise
        # again and copy-merge the remaining files/directories.
        #
        # We can't use '-exec {} +' with any arguments between
        # the '{}' and '+' as this is not POSIX. We must also
        # use '$0' and '$@' to reference all arguments.
        #
        # Using only '$@' causes a single file from each
        # invocation to be left out of the list. Weird, right?
        find "$pid-$dir/." ! -name . -prune \
            -exec sh -c 'mv -f "$0" "$@" .' {} + 2>/dev/null ||

        find "$pid-$dir/." ! -name . -prune \
            -exec sh -c 'cp -fRp "$0" "$@" .' {} +

        # Remove the directory now that all files have been
        # transferred out of it. This can't be a simple 'rmdir'
        # as we may leave files in here if any were copied.
        rm -rf "$pid-$dir"
    done
}

pkg_extract() {
    # Extract all source archives to the build directory and copy over any
    # local repository files.
    #
    # NOTE: repo_dir comes from caller.

    # Support packages without sources. Simply do nothing.
    [ -f "$repo_dir/sources" ] || return 0

    log "$1" "Extracting sources"

    while read -r src dest || [ "$src" ]; do
        mkdir -p "$mak_dir/$1/$dest" && cd "$mak_dir/$1/$dest"

        pkg_source_resolve "$1" "$src" "$dest" >/dev/null

        case $_res in
            git+*)
                # Split the source into URL + OBJECT (branch or commit).
                url=${src##git+} com=${url##*[@#]} com=${com#${url%[#@]*}}

                # This magic will shallow clone branches, commits or the
                # regular repository. It correctly handles cases where a
                # shallow clone is not possible.
                log "$1" "Cloning ${url%[#@]*}"
                git init
                git remote add origin "${url%[#@]*}"
                git fetch -t --filter=tree:0 origin "$com" || git fetch -t
                git -c advice.detachedHead=0 checkout "${com:-FETCH_HEAD}"
            ;;

            *.tar|*.tar.??|*.tar.???|*.tar.????|*.t?z)
                pkg_extract_tar_hack "$1" "$_res"
            ;;

            *.zip)
                unzip "$_res"
            ;;

            '')
                # Blank lines / Comments.
            ;;

            *)
                cp -Rf "$_res" .
            ;;
        esac
    done < "$repo_dir/sources" || die "$1" "Failed to extract $_res"
}

pkg_depends() {
    # Resolve all dependencies and generate an ordered list. The deepest
    # dependencies are listed first and then the parents in reverse order.
    contains "$deps" "$1" || {
        # Filter out non-explicit, aleady installed dependencies.
        if [ "$3" ] && [ -z "$2" ] && pkg_list "$1" >/dev/null 2>&1; then
            return
        fi

        # Detect circular dependencies and bail out.
        # Looks for multiple repeating patterns of (dep dep_parent) (5 is max).
        case " $4 " in
*" ${4##* } "*" $1 "\
*" ${4##* } "*" $1 "\
*" ${4##* } "*" $1 "\
*" ${4##* } "*" $1 "\
*" ${4##* } "*" $1 "\
*)
            die "Circular dependency detected $1 <> ${4##* }"
        esac

        pkg_find "$1"

        ! [ -e "$repo_dir/depends" ] ||

        # Recurse through the dependencies of the child packages.
        while read -r dep dep_type || [ "$dep" ]; do
            [ "${dep##\#*}" ] || continue

            pkg_depends "$dep" '' "$3" "$4 $1" "$dep_type"
        done < "$repo_dir/depends" || :

        # Add parent to dependencies list.
        if [ "$2" != expl ] || { [ "$5" = make ] && ! pkg_cache "$1"; }; then
            deps="$deps $1"
        fi
    }
}

pkg_order() {
    # Order a list of packages based on dependence and take into account
    # pre-built tarballs if this is to be called from 'kiss i'.
    unset order redro deps

    for pkg do case $pkg in
        /*.tar.*) deps="$deps $pkg" ;;
         *.tar.*) deps="$deps $ppwd/$pkg" ;;
             */*) die "Invalid argument: '/!*[]' ($pkg)" ;;
               *) pkg_depends "$pkg" raw
    esac done

    # Filter the list, only keeping explicit packages. The purpose of these
    # two loops is to order the argument list based on dependence.
    for pkg in $deps; do case " $* " in *" $pkg "* | *" ${pkg##"$ppwd/"} "*)
        order="$order $pkg"
        redro="$pkg $redro"
    esac done

    unset deps
}

pkg_strip() {
    # Strip package binaries and libraries. This saves space on the system as
    # well as on the tarballs we ship for installation.
    [ -f "$mak_dir/$pkg/nostrip" ] || [ "$KISS_STRIP" = 0 ] && return

    log "$1" "Stripping binaries and libraries"

    # Strip only files matching the below ELF types. This uses 'od' to print
    # the first 18 bytes of the file. This is the location of the ELF header
    # (up to the ELF type) and contains the type information we need.
    #
    # Static libraries (.a) are in reality AR archives which contain ELF
    # objects. We simply read from the same 18 bytes and assume that the AR
    # header equates to an archive containing objects (.o).
    #
    # Example ELF output ('003' is ELF type):
    # 0000000 177   E   L   F 002 001 001  \0  \0  \0  \0  \0  \0  \0  \0  \0
    # 0000020 003  \0
    # 0000022
    #
    # Example AR output (.a):
    # 0000000   !   <   a   r   c   h   >  \n   /
    # 0000020
    # 0000022
    find "$pkg_dir/$1" -type f | while read -r file; do
        case $(od -A o -t c -N 18 "$file") in
            # REL (object files (.o), static libraries (.a)).
            *177*E*L*F*0000020\ 001\ *|*\!*\<*a*r*c*h*\>*)
                strip -g -R .comment -R .note "$file"
            ;;

            # EXEC (binaries), DYN (shared libraries).
            # Shared libraries keep global symbols in a separate ELF section
            # called '.dynsym'. '--strip-all/-s' does not touch the dynamic
            # symbol entries which makes this safe to do.
            *177*E*L*F*0000020\ 00[23]\ *)
                strip -s -R .comment -R .note "$file"
            ;;
        esac
    done 2>/dev/null || :
}

pkg_fix_deps() {
    # Dynamically look for missing runtime dependencies by checking each
    # binary and library with 'ldd'. This catches any extra libraries and or
    # dependencies pulled in by the package's build suite.
    log "$1" "looking for dependencies (using ${cmd_elf##*/})"

    cd "$pkg_dir/$1/$pkg_db/$1"

    set +f
    set -f -- "$sys_db/"*/manifest

    : >> depends

    find "$pkg_dir/${PWD##*/}/" -type f 2>/dev/null |

    while read -r _fix_file; do
        ldd_buf=$(ldd -- "$_fix_file" 2>/dev/null) ||
            continue

        elf_buf=${cmd_elf:+"$("$cmd_elf" -d "$_fix_file" 2>/dev/null)"} ||
            continue

        while read -r line || [ "$line" ]; do
            case $line in *NEEDED*\[*\] | *'=>'*)
                # readelf: 0x0000 (NEEDED) Shared library: [libjson-c.so.5]
                line=${line##*\[}
                line=${line%%\]*}

                # Resolve library path.
                # ldd: libjson-c.so.5 => /lib/libjson-c.so.5 ...
                case $cmd_elf in
                    *readelf) line=${ldd_buf#*"	$line => "} ;;
                    *)        line=${line##*=> } ;;
                esac
                line=${line%% *}

                # Skip files owned by libc and POSIX.
                case ${line##*/} in
                    ld-*           |\
                    lib[cm].so*    |\
                    libdl.so*      |\
                    libpthread.so* |\
                    librt.so*      |\
                    libtrace.so*   |\
                    libxnet.so*    |\
                    ldd)
                        continue
                    ;;

                    *)
                        # Skip file if owned by current package
                        pkg_owner -l "/${line#/}\$" "$PWD/manifest" &&
                            continue

                        pkg_owner -l "/${line#/}\$" "$@" &&
                            printf '%s\n' "$pkg_owner"
                    ;;
                esac
            esac
        done <<EOF || :
${elf_buf:-"$ldd_buf"}
EOF
    done | sort -uk1,1 depends - > "$tmp_dir/.fixdeps"

    # If the depends file was modified, show a diff and replace it.
    if [ -s "$tmp_dir/.fixdeps" ]; then
        diff -U 3 depends - < "$tmp_dir/.fixdeps" 2>/dev/null || :
        mv -f "$tmp_dir/.fixdeps" depends
        pkg_manifest "${PWD##*/}"
    else
        rm -f depends
    fi
}

pkg_manifest() {
    # Generate the package's manifest file. This is a list of each file
    # and directory inside the package. The file is used when uninstalling
    # packages, checking for package conflicts and for general debugging.
    log "$1" "Generating manifest"

    cd "${2:-$pkg_dir}/$1"

    # find: Print all files and directories and append '/' to directories.
    {
        find . -type d -exec printf '%s/\n' {} +
        find . ! -type d -print
    } |

    # sort: Sort the output in *reverse*. Directories appear *after* their
    #       contents.
    # sed:  Remove the first character in each line (./dir -> /dir) and
    #       remove all lines which only contain '.'.
    sort -r | sed '/^\.\/$/d;ss.ss' > "$PWD/$pkg_db/$1/manifest"

    cd "$OLDPWD"
}

pkg_manifest_validate() {
    log "$1" "Checking if manifest valid"

    while read -r line; do
        [ -h "./$line" ] || [ -e "./$line" ] || {
            printf '%s\n' "$line"
            set -- "$@" "$line"
        }
    done < "$pkg_db/$1/manifest"

    case $# in [2-9]|[1-9][0-9]*)
        die "$1" "manifest contains $(($# - 1)) non-existent files"
    esac
}

pkg_etcsums() {
    # Generate checksums for each configuration file in the package's /etc/
    # directory for use in "smart" handling of these files.
    log "$1" "Generating etcsums"

    ! [ -d "$pkg_dir/$1/etc" ] ||

    # This can't be a simple 'find -exec' as 'sh256' is a shell function
    # and not a real command of any kind. This is the shell equivalent.
    find "$pkg_dir/$1/etc" ! -type d | sort | while read -r line; do
        sh256 "$line"
    done > "$pkg_dir/$1/$pkg_db/$1/etcsums"
}

pkg_tar() (
    # Create a tarball from the built package's files. This tarball also
    # contains the package's database entry.
    #
    # NOTE: repo_ comes from caller.
    log "$1" "Creating tarball"

    # Use 'cd' to avoid needing tar's '-C' flag which may not be portable
    # across implementations.
    cd "$pkg_dir/$1"

    # Create a tarball from the contents of the built package.
    tar cf - . | case ${KISS_COMPRESS:=gz} in
        bz2)  bzip2 -z ;;
        gz)   gzip -6  ;;
        lzma) lzma -z  ;;
        lz)   lzip -z  ;;
        xz)   xz -zT0  ;;
        zst)  zstd -z  ;;
    esac > "$bin_dir/$1@$repo_ver-$repo_rel.tar.${KISS_COMPRESS:=gz}"

    log "$1" "Successfully created tarball"
    run_hook post-package "$1"
)

pkg_build() {
    # Build packages and turn them into packaged tarballs.
    # Order the argument list and filter out duplicates.
    pkg_order "$@"

    # Intentional, globbing disabled.
    # shellcheck disable=2046,2086
    set -- $order

    log "Resolving dependencies"

    # Mark packages passed on the command-line separately from those
    # detected as dependencies. We need to treat explicitly passed packages
    # differently from those pulled in as dependencies.
    #
    # This also resolves all dependencies and stores the result in '$deps'.
    for pkg do
        pkg_depends "$pkg" expl filter
        explicit="$explicit $pkg "
    done

    # If this is an update, don't always build explicitly passsed packages
    # and instead install pre-built binaries if they exist.
    [ "$pkg_update" ] || explicit_build=$explicit

    set --

    # If an explicit package is a dependency of another explicit package,
    # remove it from the explicit list as it needs to be installed as a
    # dependency.
    for pkg in $explicit; do
        contains "$deps" "$pkg" || set -- "$@" "$pkg"
    done
    explicit_cnt=$#

    log "Building: explicit: $*${deps:+, implicit: ${deps## }}"

    # Intentional, globbing disabled.
    # shellcheck disable=2046,2086
    set -- $deps "$@"

    # Ask for confirmation if extra packages need to be built.
    [ "$#" -ne "$explicit_cnt" ] || [ "$pkg_update" ] && prompt

    for pkg do
        pkg_lint "$pkg"
    done

    log "Checking for pre-built dependencies"

    # Install any pre-built dependencies if they exist in the binary
    # directory and are up to date.
    for pkg in "$@"; do
        if ! contains "$explicit_build" "$pkg" && pkg_cache "$pkg"; then
            log "$pkg" "Found pre-built binary, installing"

            # Intended behavior.
            # shellcheck disable=2030,2031
            (export KISS_FORCE=1; args i "$tar_file")
        else
            set -- "$@" "$pkg"
        fi

        shift
    done

    for pkg do
        pkg_source "$pkg"
        pkg_verify "$pkg"
    done

    # Finally build and create tarballs for all passed packages and
    # dependencies.
    for pkg do
        log "$pkg" "Building package ($((in+=1))/$#)"

        pkg_find_version "$pkg"
        run_hook pre-extract "$pkg" "$pkg_dir/$pkg"
        pkg_extract "$pkg"

        # Install built packages to a directory under the package name to
        # avoid collisions with other packages.
        mkdir -p "$pkg_dir/$pkg/$pkg_db" "$mak_dir/$pkg"
        cd "$mak_dir/$pkg"

        log "$pkg" "Starting build"
        run_hook pre-build "$pkg" "$pkg_dir/$pkg"

        # Call the build script, log the output to the terminal and to a file.
        # There's no PIPEFAIL in POSIX shelll so we must resort to tricks like
        # killing the script ourselves.
        { "$repo_dir/build" "$pkg_dir/$pkg" "$repo_ver" 2>&1 || {
            log "$pkg" "Build failed"
            log "$pkg" "Log stored to $log_dir/$pkg-$time-$pid"
            run_hook build-fail "$pkg" "$pkg_dir/$pkg"
            pkg_clean
            kill 0
        } } | tee "$log_dir/$pkg-$time-$pid"

        # Delete the log file if the build succeeded to prevent the directory
        # from filling very quickly with useless logs.
        [ "$KISS_KEEPLOG" = 1 ] || rm -f "$log_dir/$pkg-$time-$pid"

        # Copy the repository files to the package directory. This acts as the
        # database entry.
        cp -LRf "$repo_dir" "$pkg_dir/$pkg/$pkg_db/"

        log "$pkg" "Successfully built package"
        run_hook post-build "$pkg" "$pkg_dir/$pkg"

        # Remove all .la files from the packages. They're unneeded and cause
        # issues when a package stops providing one.
        find "$pkg_dir/$pkg/usr/lib" \
            -name \*.la -exec rm -f {} + 2>/dev/null || :

        # Remove this unneeded file from all packages as it is an endless
        # source of conflicts. This is used with info pages we we do not support.
        rm -f "$pkg_dir/$pkg/usr/lib/charset.alias"

        # Create the manifest file early and make it empty. This ensures that
        # the manifest is added to the manifest.
        : > "$pkg_dir/$pkg/$pkg_db/$pkg/manifest"

        # If the package contains '/etc', add a file called 'etcsums' to the
        # manifest. See comment directly above.
        [ -d "$pkg_dir/$pkg/etc" ] && : > "$pkg_dir/$pkg/$pkg_db/$pkg/etcsums"

        pkg_strip    "$pkg"
        pkg_manifest "$pkg"
        pkg_fix_deps "$pkg"
        pkg_etcsums  "$pkg"
        pkg_tar      "$pkg"

        if [ "$pkg_update" ] || ! contains "$explicit" "$pkg"; then
            log "$pkg" "Needed as a dependency or has an update, installing"

            # Intended behavior.
            # shellcheck disable=2030,2031
            (export KISS_FORCE=1; args i "$pkg")
        fi
    done

    [ "$pkg_update" ] || {
        # Intentional, globbing disabled.
        # shellcheck disable=2046,2086
        set -- $explicit

        ! prompt "Install built packages? [$*]" || (args i "$@")
    }
}

pkg_checksums() {
    # Generate checksums for packages.
    #
    # NOTE: repo_dir comes from caller.
    while read -r src dest || [ "$src" ]; do
        pkg_source_resolve "$1" "$src" "$dest" >/dev/null

        case $_res in */*[!.])
            sh256 "$_res"
        esac
    done < "$repo_dir/sources" || die "$1" "Failed to generate checksums"
}

pkg_verify() {
    # Verify all package checksums. This is achieved by generating a new set
    # of checksums and then comparing those with the old set.
    log "$1" "Checking sources"

    pkg_find "$1"

    [ -f "$repo_dir/sources" ] || return 0

    # Read the repository checksums into a list.
    while read -r chk _ || [ "$chk" ]; do
        set -- "$@" "$chk"
    done < "$repo_dir/checksums"

    # Generate a new set of checksums to compare against.
    pkg_checksums "$1" > "$mak_dir/v"

    # Check that the first column (separated by whitespace) match in both
    # checksum files. If any part of either file differs, mismatch. Abort.
    while read -r new _; do shift
        printf 'old %s\nnew %s\n' "${1:-missing}" "$new"

        case $new-${1:-null} in
            "$1-$new"|"$new-SKIP") ;;

            *) die "${repo_dir##*/}" "Checksum mismatch"
        esac
    done < "$mak_dir/v"
}

pkg_conflicts() {
    # Check to see if a package conflicts with another.
    log "$1" "Checking for package conflicts"

    # Filter the tarball's manifest and select only files. Resolve all
    # symlinks in file paths as well.
    while read -r file; do
        file=$KISS_ROOT/${file#/}

        # Skip all directories.
        case $file in */) continue; esac

        # Attempt to resolve symlinks by using 'cd'.
        # If this fails, fallback to the file's parent
        # directory.
        cd -P "${file%/*}" 2>/dev/null || PWD=${file%/*}

        # Print the file with all symlinks in its path
        # resolved to their real locations.
        printf '%s\n' "${PWD#"$KISS_ROOT"}/${file##*/}"

        cd "$OLDPWD"
    done < "$tar_dir/$1/$pkg_db/$1/manifest" > "$mak_dir/cf_m"

    p_name=$1
    set +f
    set -f "$sys_db"/*/manifest

    # Generate a list of all installed package manifests and remove the
    # current package from the list. This is the simplest method of
    # dropping an item from the argument list. The one downside is that
    # it cannot live in a function due to scoping of arguments.
    for manifest do
        shift

        [ "$sys_db/$p_name/manifest" = "$manifest" ] && continue

        set -- "$@" "$manifest"
    done

    # Return here if there is nothing to check conflicts against.
    [ "$#" != 0 ] || return 0

    # Store the list of found conflicts in a file as we'll be using the
    # information multiple times. Storing things in the cache dir allows
    # us to be lazy as they'll be automatically removed on script end.
    grep -Fxf "$mak_dir/cf_m" -- "$@" 2>/dev/null > "$mak_dir/cf" || :

    # Enable alternatives automatically if it is safe to do so.
    # This checks to see that the package that is about to be installed
    # doesn't overwrite anything it shouldn't in '/var/db/kiss/installed'.
    grep -q ":/var/db/kiss/installed/" "$mak_dir/cf" || choice_auto=1

    if [ "$KISS_CHOICE" != 0  ] &&
       [ "$choice_auto"  = 1  ] &&
       [ -s "$mak_dir/cf" ]; then
        # This is a novel way of offering an "alternatives" system.
        # It is entirely dynamic and all "choices" are created and
        # destroyed on the fly.
        #
        # When a conflict is found between two packages, the file
        # is moved to a directory called "choices" and its name
        # changed to store its parent package and its intended
        # location.
        #
        # The package's manifest is then updated to reflect this
        # new location.
        #
        # The 'kiss alternatives' command parses this directory and
        # offers you the CHOICE of *swapping* entries in this
        # directory for those on the filesystem.
        #
        # The alternatives command does the same thing we do here,
        # it rewrites manifests and moves files around to make
        # this work.
        #
        # Pretty nifty huh?
        while IFS=: read -r _ con; do
            printf '%s\n' "Found conflict $con"

            # Create the "choices" directory inside of the tarball.
            # This directory will store the conflicting file.
            mkdir -p "$tar_dir/$p_name/${cho_dir:=var/db/kiss/choices}"

            # Construct the file name of the "db" entry of the
            # conflicting file. (pkg_name>usr>bin>ls)
            con_name=$(printf %s "$con" | sed 's|/|>|g')

            # Move the conflicting file to the choices directory
            # and name it according to the format above.
            mv -f "$tar_dir/$p_name/$con" \
                  "$tar_dir/$p_name/$cho_dir/$p_name$con_name" 2>/dev/null || {
                log "File must be in ${con%/*} and not a symlink to it"
                log "This usually occurs when a binary is installed to"
                log "/sbin instead of /usr/bin (example)"
                log "Before this package can be used as an alternative,"
                log "this must be fixed in $p_name. Contact the maintainer"
                die "by finding their details via 'kiss-maintainer'" "" "!>"
            }
        done < "$mak_dir/cf"

        log "$p_name" "Converted all conflicts to choices (kiss a)"

        # Rewrite the package's manifest to update its location
        # to its new spot (and name) in the choices directory.
        pkg_manifest "$p_name" "$tar_dir" 2>/dev/null

    elif [ -s "$mak_dir/cf" ]; then
        log "Package '$p_name' conflicts with another package" "" "!>"
        log "Run 'KISS_CHOICE=1 kiss i $p_name' to add conflicts" "" "!>"
        die "as alternatives." "" "!>"
    fi
}

pkg_swap() {
    # Swap between package alternatives.
    pkg_list "$1" >/dev/null

    alt=$(printf %s "$1$2" | sed 's|/|>|g')
    cd "$sys_db/../choices"

    [ -f "$alt" ] || [ -h "$alt" ] ||
        die "Alternative '$1 $2' doesn't exist"

    if [ -f "$2" ]; then
        # Figure out which package owns the file we are going to swap for
        # another package's. Print the full path to the manifest file which
        # contains the match to our search.
        pkg_owns=$(set +f; grep -lFx "$2" "$sys_db/"*/manifest) || :

        # Extract the package name from the path above.
        pkg_owns=${pkg_owns%/*}
        pkg_owns=${pkg_owns##*/}

        # Ensure that the file we're going to swap is actually owned by a
        # package. If it is not, we have to die here.
        [ "$pkg_owns" ] || die "File '$2' exists on filesystem but isn't owned"

        log "Swapping '$2' from '$pkg_owns' to '$1'"

        # Convert the current owner to an alternative and rewrite its manifest
        # file to reflect this.
        cp -Pf "$KISS_ROOT/$2" "$pkg_owns>${alt#*>}"

        # Replace the matching line in the manifest with the desired replacement.
        # This used to be a 'sed' call which turned out to be a little
        # error-prone in some cases. This new method is a tad slower but ensures
        # we never wipe the file due to a command error.
        while read -r line; do
            case $line in
                "$2") printf '%s\n' "${PWD#"$KISS_ROOT"}/$pkg_owns>${alt#*>}" ;;
                   *) printf '%s\n' "$line" ;;
            esac
        done < "../installed/$pkg_owns/manifest" | sort -r > "$mak_dir/.$1"

        mv -f "$mak_dir/.$1" "../installed/$pkg_owns/manifest"
    fi

    # Convert the desired alternative to a real file and rewrite the manifest
    # file to reflect this. The reverse of above.
    mv -f "$alt" "$KISS_ROOT/$2"

    # Replace the matching line in the manifest with the desired replacement.
    # This used to be a 'sed' call which turned out to be a little error-prone
    # in some cases. This new method is a tad slower but ensures we never wipe
    # the file due to a command error.
    while read -r line; do
        case $line in
            "${PWD#"$KISS_ROOT"}/$alt") printf '%s\n' "$2" ;;
                                     *) printf '%s\n' "$line" ;;
        esac
    done < "../installed/$1/manifest" | sort -r > "$mak_dir/.$1"

    mv -f "$mak_dir/.$1" "../installed/$1/manifest"
}

pkg_install_files() {
    # Reverse the manifest file so that we start shallow and go deeper as we
    # iterate over each item. This is needed so that directories are created
    # going down the tree.
    sort "$2/$pkg_db/${2##*/}/manifest" |

    while read -r file; do
        # Grab the octal permissions so that directory creation
        # preserves permissions.
        # See: [2] at top of script.
        rwx=$(ls -ld "$2/${file#/}") oct='' b='' o=0

        # Convert the output of 'ls' (rwxrwx---) to octal. This is simply
        # a 1-9 loop with the second digit being the value of the field.
        for c in 14 22 31 44 52 61 74 82 91; do
            rwx=${rwx#?}

            case $rwx in
                [rwx]*): "$((o+=${c#?}))" ;;
                 [st]*): "$((o+=1))" "$((b+=4 / (${c%?}/3)))" ;;
                 [ST]*): "$((b+=1))" ;;
            esac

            [ "$((${c%?} % 3))" = 0 ] && oct=$oct$o o=0
        done

        _file=$KISS_ROOT/${file#/}

        # Copy files and create directories (preserving permissions),
        # skipping anything located in /etc/.
        #
        # The 'test' will run with '-e' for no-overwrite and '-z'
        # for overwrite.
        case $file in /etc/*) ;;
            */)
                # Skip directories if they already exist in the file system.
                # (Think /usr/bin, /usr/lib, etc).
                [ -d "$_file" ] || mkdir -m "$oct" "$_file"
            ;;

            *)
                # Skip directories as they're likely symlinks in this case.
                # Pure directories in manifests have a suffix of '/'.
                [ -d "$_file" ] || test "$1" "$_file" || {
                    cp -fP "$2/${file#/}" "$_file"

                    # Skip changing permissions of symlinks. This prevents
                    # errors when the symlink exists prior to the target.
                    [ -h "$_file" ] || chmod "$b$oct" "$_file"
                }
        esac
    done || :
}

pkg_remove_files() {
    # Remove a file list from the system. This function runs during package
    # installation and package removal. Combining the removals in these two
    # functions allows us to stop duplicating code.
    while read -r file; do
        case $file in /etc/?*[!/])
            sh256 "$KISS_ROOT/$file" >/dev/null
            sum_old=$(grep -F "${hash:-null}" "$mak_dir/c")

            [ "${hash:-null}" = "$sum_old" ] || {
                printf 'Skipping %s (modified)\n' "$file"
                continue
            }
        esac 2>/dev/null || :

        _file=${KISS_ROOT:+"$KISS_ROOT/"}${file%%/}

        # Queue all directory symlinks for later removal.
        if [ -h "$_file" ] && [ -d "$_file" ]; then
            case $file in /*/*/)
                set -- "$@" "$_file"
            esac

        # Remove empty directories.
        elif [ -d "$_file" ]; then
            rmdir "$_file" 2>/dev/null || :

        # Remove everything else.
        else
            rm -f "$_file"
        fi
    done || :

    # Remove all broken directory symlinks.
    for sym do
        [ -e "$sym" ] || rm -f "$sym"
    done
}

pkg_etc() (
    [ -d "$tar_dir/$pkg_name/etc" ] || return 0

    cd "$tar_dir/$pkg_name"

    # Create all directories beforehand.
    find etc -type d | while read -r dir; do
        mkdir -p "$KISS_ROOT/$dir"
    done

    # Handle files in /etc/ based on a 3-way checksum check.
    find etc ! -type d | sort | while read -r file; do
        i=$((i + 1))

        { sh256 "$file";            sum_new=$hash
          sh256 "$KISS_ROOT/$file"; sum_sys=$hash
          sum_old=$(awk "NR == $i" "$mak_dir/c"); } >/dev/null 2>&1 || :

        log "$pkg_name" "Doing 3-way handshake for $file"
        printf '%s\n' "Previous: ${sum_old:-null}"
        printf '%s\n' "System:   ${sum_sys:-null}"
        printf '%s\n' "New:      ${sum_new:-null}"

        # Use a case statement to easily compare three strings at
        # the same time. Pretty nifty.
        case ${sum_old:-null}${sum_sys:-null}${sum_new} in
            # old = Y, sys = X, new = Y
            "${sum_new}${sum_sys}${sum_old}")
                log "Skipping $file"
                continue
            ;;

            # old = X, sys = X, new = X
            # old = X, sys = Y, new = Y
            # old = X, sys = X, new = Y
            "${sum_old}${sum_old}${sum_old}"|\
            "${sum_old:-null}${sum_sys}${sum_sys}"|\
            "${sum_sys}${sum_old}"*)
                log "Installing $file"
                new=
            ;;

            # All other cases.
            *)
                war "$pkg_name" "saving /$file as /$file.new"
                new=.new
            ;;
        esac

        cp -fPp "$file" "$KISS_ROOT/${file}${new}"
        chown root:root "$KISS_ROOT/${file}${new}" 2>/dev/null
    done || :
)

pkg_removable() {
    # Check if a package is removable and die if it is not.
    # A package is removable when it has no dependents.
    log "$1" "Checking if package removable"

    cd "$sys_db"
    set +f

    ! grep -lFx -- "$1" */depends ||
        die "$1" "Not removable, has dependents"

    set -f
    cd "$OLDPWD"
}

pkg_remove() {
    # Remove a package and all of its files. The '/etc' directory is handled
    # differently and configuration files are *not* overwritten.
    pkg_list "$1" >/dev/null || return

    # Intended behavior.
    # shellcheck disable=2030,2031
    [ "${KISS_FORCE:=0}" = 1 ] || pkg_removable "$1"

    # Block being able to abort the script with 'Ctrl+C' during removal.
    # Removes all risk of the user aborting a package removal leaving an
    # incomplete package installed.
    trap '' INT

    if [ -x "$sys_db/$1/pre-remove" ]; then
        log "$1" "Running pre-remove script"
        "$sys_db/$1/pre-remove" || :
    fi

    # Make a backup of the etcsums file (if it exists).
    cp -f "$sys_db/$1/etcsums" "$mak_dir/c" 2>/dev/null || : > "$mak_dir/c"

    log "$1" "Removing package"
    pkg_remove_files < "$sys_db/$1/manifest"

    # Reset 'trap' to its original value. Removal is done so
    # we no longer need to block 'Ctrl+C'.
    trap pkg_clean EXIT INT

    log "$1" "Removed successfully"
}

pkg_installable() {
    # Check if a package is removable and die if it is not.
    # A package is removable when all of its dependencies
    # are satisfied.
    log "$1" "Checking if package installable"

    # False positive.
    # shellcheck disable=2094
    ! [ -f "$2" ] ||

    while read -r dep dep_type || [ "$dep" ]; do
        case $dep-$dep_type in
            \#*-*)
                continue
            ;;

            *-)
                pkg_list "$dep" >/dev/null 2>&1 || {
                    printf '%s %s\n' "$dep" "$dep_type"
                    set -- "$1" "$2" "$(($3 + 1))"
                }
            ;;
        esac
    done < "$2"

    case ${3:-0} in [1-9]*)
        die "$1" "Package not installable, missing $3 package(s)"
    esac
}

pkg_install() {
    # Install a built package tarball.
    #
    # Package installation works similarly to the method used by Slackware in
    # some of their tooling. It's not the obvious solution to the problem,
    # however it is the best solution at this given time.
    #
    # When an installation is an update to an existing package, instead of
    # removing the old version first we do something different.
    #
    # The new version is installed overwriting any files which it has in
    # common with the previously installed version of the package.
    #
    # A "diff" is then generated between the old and new versions and contains
    # any files existing in the old version but not the new version.
    #
    # The package manager then goes and removes these files which leaves us
    # with the new package version in the file system and all traces of the
    # old version gone.
    #
    # For good measure the package manager will then install the new package
    # an additional time. This is to ensure that the above diff didn't contain
    # anything incorrect.
    #
    # This is the better method as it is "seamless". An update to busybox won't
    # create a window in which there is no access to all of its utilities to
    # give an example.

    # Install can also take the full path to a tarball. We don't need to check
    # the repository if this is the case.
    if [ -f "$1" ] && [ -z "${1%%*.tar.*}" ]; then
        tar_file=$1 pkg_name=${1##*/} pkg_name=${pkg_name%[#@]*}

    elif pkg_cache "$1" 2>/dev/null; then
        pkg_name=$1

    else
        case $1 in
            *.tar.*) die "Tarball '$1' does not exist" ;;
            *)       die "Package '$1' has not yet been built"
        esac
    fi

    mkdir -p "$tar_dir/$pkg_name"
    cd       "$tar_dir/$pkg_name"

    # The tarball is extracted to a temporary directory where its contents are
    # then "installed" to the filesystem. Running this step as soon as possible
    # allows us to also check the validity of the tarball and bail out early
    # if needed.
    decompress "$tar_file" | tar xf -

    # Naively assume that the existence of a manifest file is all that
    # determines a valid KISS package from an invalid one. This should be a
    # fine assumption to make in 99.99% of cases.
    [ -f "./$pkg_db/$pkg_name/manifest" ] || die "Not a valid KISS package"

    [ "$KISS_FORCE" = 1 ] || {
        pkg_manifest_validate "$pkg_name"
        pkg_installable "$pkg_name" "$tar_dir/$pkg_name/$pkg_db/$pkg_name/depends"
    }

    run_hook pre-install "$pkg_name" "$tar_dir/$pkg_name"
    pkg_conflicts "$pkg_name"

    log "$pkg_name" "Installing package"

    # Block being able to abort the script with Ctrl+C during installation.
    # Removes all risk of the user aborting a package installation leaving
    # an incomplete package installed.
    trap '' INT

    # If the package is already installed (and this is an upgrade) make a
    # backup of the manifest and etcsums files.
    cp -f "$sys_db/$pkg_name/manifest" "$mak_dir/m" 2>/dev/null ||
        : > "$mak_dir/m"
    cp -f "$sys_db/$pkg_name/etcsums"  "$mak_dir/c" 2>/dev/null ||
        : > "$mak_dir/c"

    # Install the package's files by iterating over its manifest.
    pkg_install_files -z "$tar_dir/$pkg_name"

    # Handle /etc/ files in a special way (via a 3-way checksum) to determine
    # how these files should be installed. Do we overwrite the existing file?
    # Do we install it as $file.new to avoid deleting user configuration? etc.
    #
    # This is more or less similar to Arch Linux's Pacman with the user manually
    # handling the .new files when and if they appear.
    pkg_etc

    # This is the aforementioned step removing any files from the old version of
    # the package if the installation is an update. Each file type has to be
    # specially handled to ensure no system breakage occurs.
    #
    # Files in /etc/ are skipped entirely as they'll be handled via a 3-way
    # checksum system due to the nature of their existence.
    grep -vFxf "$sys_db/$pkg_name/manifest" "$mak_dir/m" 2>/dev/null |
    pkg_remove_files

    # Install the package's files a second time to fix any mess caused by the
    # above removal of the previous version of the package.
    log "$pkg_name" "Verifying installation"
    pkg_install_files -e "$tar_dir/$pkg_name"

    # Reset 'trap' to its original value. Installation is done so we no longer
    # need to block 'Ctrl+C'.
    trap pkg_clean EXIT INT

    if [ -x "$sys_db/$pkg_name/post-install" ]; then
        log "$pkg_name" "Running post-install hook"

        hook_output=$("$sys_db/$pkg_name/post-install" 2>&1)

        [ -z "$hook_output" ] || {
            log "$pkg_name" "Running post-install hook" 2>&1
            printf '%s\n' "$hook_output"
        } |

        # 'tee' is used as we would still like to display 'stderr'
        tee -a "$log_dir/post-install-$time-$pid" >/dev/null
    fi

    run_hook post-install "$pkg_name" "$sys_db/$pkg_name"

    log "$pkg_name" "Installed successfully"
}

pkg_updates() {
    # Check all installed packages for updates. So long as the installed
    # version and the version in the repositories differ, it's considered
    # an update.
    log "Updating repositories"

    # Create a list of all repositories.
    # Intentional, globbing disabled.
    # shellcheck disable=2046,2086
    { IFS=:; set -- $KISS_PATH; unset IFS; }

    # Update each repository in '$KISS_PATH'.
    for repo do
        # Handle null repositories (KISS_PATH=repo:::::repo).
        [ "$repo" ] || continue

        [ -d "$repo" ] || {
            log "$repo" " "
            printf 'Skipping repository, not a directory\n'
            continue
        }

        cd "$repo"

        git remote >/dev/null 2>&1 || {
            log "$repo" " "
            printf 'Skipping git pull, not a repository\n'
            continue
        }

        # Go to the repository's root directory.
        git_root=$(git rev-parse --show-toplevel)
        cd "${git_root:?"failed to find git root for '$PWD'"}"

        # Go to the real root directory if this is a submodule.
        git_root=$(git rev-parse --show-superproject-working-tree)
        cd "${git_root:-"$PWD"}"

        contains "$repos" "$PWD" || {
            repos="$repos $PWD "

            # Display a tick if signing is enabled for this repository.
            case $(git config merge.verifySignatures) in
                true) log "$PWD" "[signed] " ;;
                *)    log "$PWD" " " ;;
            esac

            if [ -w "$PWD" ] && [ "$uid" != 0 ]; then
                git pull
                git submodule update --remote --init -f

            else
                [ "$uid" = 0 ] || log "$PWD" "Need root to update"

                # Find out the owner of the repository and spawn
                # git as this user below.
                #
                # This prevents 'git' from changing the original
                # ownership of files and directories in the rare
                # case that the repository is owned by a 3rd user.
                file_owner "$PWD"

                # We're in a repository which is owned by a 3rd
                # user. Not root or the current user.
                [ "$user" = root ] || log "Dropping to $user for pull"

                as_root git pull
                as_root git submodule update --remote --init -f
            fi
        }
    done

    log "Checking for new package versions"

    set +f --

    for pkg in "$sys_db/"*; do
        read -r db_ver db_rel < "$pkg/version" ||
            die "${pkg##*/}" "Failed to read installed version"

        pkg_find_version "${pkg##*/}"

        # Compare installed packages to repository packages.
        [ "$db_ver-$db_rel" = "$repo_ver-$repo_rel" ] || {
            printf '%s\n' "${pkg##*/} $db_ver-$db_rel ==> $repo_ver-$repo_rel"
            set -- "$@" "${pkg##*/}"
        }
    done

    set -f

    case " $* " in
        *" kiss "*)
            log "Detected package manager update"
            log "The package manager will be updated first"

            prompt

            pkg_build kiss
            args i kiss

            log "Updated the package manager"
            log "Re-run 'kiss update' to update your system"
        ;;

        "  ")
            log "Everything is up to date"
        ;;

        *)
            log "Packages to update: $*"
            pkg_update=1
            pkg_build "$@"
            log "Updated all packages"
        ;;
    esac
}

pkg_clean() {
    # Clean up on exit or error. This removes everything related to the build.
    [ "$KISS_DEBUG" = 1 ] || rm -rf "$tmp_dir"
}

args() {
    # Parse script arguments manually. This is rather easy to do in our case
    # since the first argument is always an "action" and the arguments that
    # follow are all package names.
    action=$1
    shift "$(($# != 0))"

    # Ensure that arguments do not contain invalid characters. Wildcards can
    # not be used here as they would conflict with kiss extensions.
    case $action in
        a|alternatives)
            case $1 in */*|*\**|*\!*|*\[*|*\]*)
                die "Invalid argument: '/!*[]' ($1)"
            esac
        ;;

        b|build|c|checksum|d|download|l|list|r|remove)
            case $* in */*|*\**|*\!*|*\[*|*\]*)
                die "Arguments contain invalid characters: '/!*[]' ($*)"
            esac
        ;;

        i|install)
            case $* in *\**|*\!*|*\[*|*\]*)
                die "Arguments contain invalid characters: '!*[]' ($*)"
            esac
        ;;
    esac

    # CRUX style usage using the current directory as the name of the package
    # to be operated on. This needs to sit before the 'as_root()' calls as
    # they reset the current working directory during their invocations.
    [ "$1" ] || case $action in b|build|c|checksum|d|download|i|install|r|remove)
        export KISS_PATH=${PWD%/*}:$KISS_PATH
        set -- "${PWD##*/}"
    esac

    # Rerun the script as root with a fixed environment if needed. We sadly
    # can't run singular functions as root so this is needed.
    case $action in a|alternatives|i|install|r|remove)
        [ -z "$1" ] || [ -w "$KISS_ROOT/" ] || [ "$uid" = 0 ] || {
            as_root env \
                HOME="$HOME" \
                XDG_CACHE_HOME="$XDG_CACHE_HOME" \
                KISS_PATH="$KISS_PATH" \
                KISS_FORCE="$KISS_FORCE" \
                KISS_ROOT="$KISS_ROOT" \
                KISS_CHOICE="$KISS_CHOICE" \
                KISS_COLOR="$KISS_COLOR" \
                KISS_TMPDIR="$KISS_TMPDIR" \
                "$0" "$action" "$@"
            return
        }
    esac

    # Actions can be abbreviated to their first letter. This saves keystrokes
    # once you memorize the commands.
    case $action in
        a|alternatives)
            if [ "$1" = - ]; then
                while read -r pkg path; do
                    pkg_swap "$pkg" "$path"
                done

            elif [ "$1" ]; then
                pkg_swap "$@"

            else
                # Go over each alternative and format the file
                # name for listing. (pkg_name>usr>bin>ls)
                set +f; for pkg in "$sys_db/../choices"/*; do
                    printf '%s\n' "${pkg##*/}"
                done | sed 's|>| /|; s|>|/|g; /\*/d'
            fi
        ;;

        c|checksum)
            for pkg do pkg_lint   "$pkg"; done
            for pkg do pkg_source "$pkg" c; done
            for pkg do
                pkg_find "$pkg"

                [ -f "$repo_dir/sources" ] || {
                    log "$pkg" "No sources file, skipping checksums"
                    continue
                }

                sums=$(pkg_checksums "$pkg")

                [ "$sums" ] || {
                    log "$pkg" "No sources needing checksums"
                    continue
                }

                printf '%s\n' "$sums"
                printf '%s\n' "$sums" > "$repo_dir/checksums"
                log "$pkg" "Generated checksums"
            done
        ;;

        i|install|r|remove)
            pkg_order "$@"

            case $action in
                i*) for pkg in $order; do pkg_install "$pkg"; done ;;
                r*) for pkg in $redro; do pkg_remove  "$pkg"; done
            esac
        ;;

        b|build)    pkg_build "${@:?No packages installed}" ;;
        d|download) for pkg do pkg_source "$pkg"; done ;;
        l|list)     pkg_list "$@" ;;
        u|update)   pkg_updates ;;
        s|search)   for pkg do pkg_find "$pkg" all; done ;;
        v|version)  printf '5.4.6\n' ;;

        '')
            log 'kiss [a|b|c|d|i|l|r|s|u|v] [pkg]...'
            log 'alternatives List and swap to alternatives'
            log 'build        Build a package'
            log 'checksum     Generate checksums'
            log 'download     Pre-download all sources'
            log 'install      Install a package'
            log 'list         List installed packages'
            log 'remove       Remove a package'
            log 'search       Search for a package'
            log 'update       Update the system'
            log 'version      Package manager version'

            printf '\nRun "kiss help-ext" to see all actions\n'
        ;;

        help-ext)
            log 'Installed extensions (kiss-* in PATH)'

            # Intentional, globbing disabled.
            # shellcheck disable=2046,2030,2031
            set -- $(pkg_find kiss-\* all -x "$PATH")

            # To align descriptions figure out which extension has the longest
            # name by doing a simple 'name > max ? name : max' on the basename
            # of the path with 'kiss-' stripped as well.
            #
            # This also removes any duplicates found in '$PATH', picking the
            # first match.
            for path do p=${path#*/kiss-}
                case " $seen " in
                    *" $p "*) shift ;;
                    *) seen=" $seen $p " max=$((${#p} > max ? ${#p}+1 : max))
                esac
            done

            # Print each extension, grab its description from the second line
            # in the file and align the output based on the above max.
            for path do
                printf "%b->%b %-${max}s " "$c1" "$c3" "${path#*/kiss-}"
                sed -n 's/^# *//;2p' "$path"
            done >&2
        ;;

        *)
            pkg_find "kiss-$action*" "" -x "$PATH"
            "$repo_dir" "$@"
        ;;
    esac

    if [ -s "$log_dir/post-install-$time-$pid" ]; then
        cat "$log_dir/post-install-$time-$pid"
        log "Post-install log stored to $log_dir/post-install-$time-$pid"
    fi
}

create_tmp_dirs() {
    # Root directory.
    KISS_ROOT=${KISS_ROOT%"${KISS_ROOT##*[!/]}"}

    # This allows for automatic setup of a KISS chroot and will
    # do nothing on a normal system.
    mkdir -p "$KISS_ROOT/" 2>/dev/null || :

    # System package database.
    sys_db=$KISS_ROOT/${pkg_db:=var/db/kiss/installed}

    # Top-level cache directory.
    cac_dir=${XDG_CACHE_HOME:-"${HOME%"${HOME##*[!/]}"}/.cache"}
    cac_dir=${cac_dir%"${cac_dir##*[!/]}"}/kiss

    # Persistent cache directories.
    src_dir=$cac_dir/sources
    log_dir=$cac_dir/logs/${time%-*}
    bin_dir=$cac_dir/bin

    # Top-level Temporary cache directory.
    tmp_dir=${KISS_TMPDIR:="$cac_dir/proc"}
    tmp_dir=${tmp_dir%"${tmp_dir##*[!/]}"}/$pid

    # Temporary cache directories.
    mak_dir=$tmp_dir/build
    pkg_dir=$tmp_dir/pkg
    tar_dir=$tmp_dir/extract

    mkdir -p "$src_dir" "$log_dir" "$bin_dir" \
             "$mak_dir" "$pkg_dir" "$tar_dir"
}

main() {
    # Globally disable globbing and enable exit-on-error.
    set -ef

    # Color can be disabled via the environment variable KISS_COLOR. Colors are
    # also automatically disabled if output is being used in a pipe/redirection.
    [ "$KISS_COLOR" = 0 ] || ! [ -t 2 ] ||
        c1='\033[1;33m' c2='\033[1;34m' c3='\033[m'

    # Store the original working directory to ensure that relative paths
    # passed by the user on the command-line properly resolve to locations
    # in the filesystem.
    ppwd=$PWD

    # The PID of the current shell process is used to isolate directories
    # to each specific KISS instance. This allows multiple package manager
    # instances to be run at once. Store the value in another variable so
    # that it doesn't change beneath us.
    pid=$$

    # Catch errors and ensure that build files and directories are cleaned
    # up before we die. This occurs on 'Ctrl+C' as well as success and error.
    trap pkg_clean EXIT INT

    # Figure out which 'sudo' command to use based on the user's choice or what
    # is available on the system.
    cmd_su=${KISS_SU:-"$(
        command -v sudo ||
        command -v doas ||
        command -v ssu  ||
        command -v su
    )"} || cmd_su=su

    # Figure out which utility is available to dump elf information.
    cmd_elf=${KISS_ELF:="$(
        command -v readelf      ||
        command -v eu-readelf   ||
        command -v llvm-readelf
    )"} || cmd_elf=ldd

    # Store the date and time of script invocation to be used as the name of
    # the log files the package manager creates uring builds.
    time=$(date +%Y-%m-%d-%H:%M)

    # Make note of the user's current ID to do root checks later on.
    # This is used enough to warrant a place here.
    uid=$(id -u)

    create_tmp_dirs
    args "$@"
}

main "$@"