stdin support, added optional highlight(1) dependency

en

@@ -1,76 +1,61 @@
 #!/bin/sh -e
 
-# Copyright (c) 2023 Emma Tebibyte <emma@tebibyte.media>
+# Copyright (c) 2023-2024 Emma Tebibyte <emma@tebibyte.media>
 # SPDX-License-Identifier: FSFAP
 #
 # Copying and distribution of this file, with or without modification, are
 # permitted in any medium without royalty provided the copyright notice and this
 # notice are preserved.	This file is offered as-is, without any warranty.
 
-argv0="$0"
-exec >&2 </dev/tty
-
-if test -z "$1"; then
-	printf "Usage: %s file...\n" "$argv0" 1>&2
-	exit 64 # sysexits.h(3) EX_USAGE
+if command -v highlight >/dev/null 2>&1
+then
+	HIGHLIGHT_OPTIONS='--out-format=ansi'; export HIGHLIGHT_OPTIONS
+else
+	alias highlight=cat
 fi
 
-if ! command -v mktemp >/dev/null 2>&1
-then
-	printf "%s: mktemp(1): Missing dependency." "$argv0"
-	exit 69 # sysexits.h(3) EX_UNAVAILABLE
+if test -z "$1"; then
+	set -- /dev/stdin
+	HIGHLIGHT_OPTIONS="$HIGHLIGHT_OPTIONS --syntax=none"
+	export HIGHLIGHT_OPTIONS
 fi
 
 help="$(printf "Commands:\n\
-/ – display lines containing a string.\n\
-? – displays this help message.\n\
-a – appends a line to the current buffer.\n\
-c – clears the screen.\n\
-d – deletes a line.\n\
-e – evaluates a command in the shell environment.\n\
-i – inserts a line into the buffer at position line.\n\
-p – prints the current buffer.\n\
-q – terminates editing.\n\
-r – applies a regular expression to the current buffer.\n\
-w – writes the current buffer to the file.\n\
+/ – display lines containing a string\n\
+? – display this help message\n\
+a – append a line to the current buffer\n\
+c – clear the screen\n\
+d – delete a line\n\
+e – evaluate a command in the shell environment\n\
+h – change syntax highlighting language\n\
+i – insert a line into the buffer at position line\n\
+p – print the current buffer\n\
+q – terminate editing\n\
+r – apply a regular expression to the current buffer\n\
+x – exit the program without writing output\n\
 \n\
-To learn more about a command verb, type \`? verb'.\n\
-en(1) Copyright (c) 2023 Emma Tebibyte\n")"
+en(1) Copyright (c) 2023–2024 Emma Tebibyte\n")"
 
 while test -n "$1"; do
 	content="$(cat "$1")"
-	file="$(printf "%s\n" "$1" | tr -d '/')"
-	temp_highlight="$(mktemp -t "XXXXX$file")"
-
-	# use bat for syntax highlighting if it’s available, but remove the frills
-	if command -v bat >/dev/null
-	then
-		# make bat use terminal theme
-		BAT_THEME=ansi; export BAT_THEME
-		# there has to be a temp file for writing the highlighted text to
-		syntax_h() {
-			printf "%s\n" "$1" >"$temp_highlight"
-			bat -pp --color always "$temp_highlight"
-		}
-	fi
 
 	while true; do
-		printf ">> "
+		printf ">> " >/dev/tty
 		read -r command args
 
 		case $command in
 			"/")
 				if test -z "$args"; then
-					printf "%s: %s: Missing argument.\n" "$argv0" "$args"
+					printf "%s: %s: missing argument\n" "$0" "$args"
 				else
 					printf "%s" "$content" | nl | sed -n "/$args/p"
 				fi
 				;;
 			"?")
 				if test -z "$args"; then
-					printf "%s: %s\n" "$argv0" "$help"
+					printf "%s: %s\n" "$0" "$help"
 				else
-					printf "%s: Command-specific help not implemented.\n" "$argv0" 1>&2
+					printf "%s: %s: %s invalid argument\n" "$0" "$command" "$args" 1>&2
 					continue
 				fi
 				;;
@@ -82,12 +67,10 @@ while test -n "$1"; do
 					content="$(printf "%s\n%s" "$content" "$append")"
 				fi
 				;;
-			"c")
-				clear
-				;;
+			"c") clear ;;
 			"d")
 				if test -z "$args"; then
-					printf "%s: %s: Missing argument.\n" "$argv0" "$command" 1>&2
+					printf "%s: %s: Missing argument.\n" "$0" "$command" 1>&2
 				else
 					for line in $(printf "%s\n" "$args" | sed 's/,/\n/g')
 					do
@@ -99,40 +82,29 @@ while test -n "$1"; do
 			"e")
 				eval "$args" || true
 				;;
+			"h")
+				HIGHLIGHT_OPTIONS="$HIGHLIGHT_OPTIONS --syntax=$args"
+				export HIGHLIGHT_OPTIONS
+				;;
 			"i")
-				printf "%s: i: Command not implemented.\n" "$argv0" 1>&2
+				printf "%s: i: Command not implemented.\n" "$0" 1>&2
 				;;
 			"p")
-				out="$(syntax_h "$content" 2>/dev/null || printf "%s\n" "$content")"
-				printf "%s\n" "$out" | nl -ba
-				;;
-			"q")
-				if test -n "$(printf "%s\n" "$content" | diff "$1" -)"
-				then
-					printf "%s: %s: Unsaved changes in the buffer. Quit anyway? [y/N] " \
-						"$argv0" \
-						"$1"
-					read -r quit
-					if [ "$quit" = "y" ]; then
-						break
-					else
-						continue
-					fi
-				else
-					break
-				fi
+				printf "%s\n" "$content" | highlight | nl -ba >/dev/tty
 				;;
+			"q") break ;;
 			"r")
 				content="$(printf "%s" "$content" | sed -e "$args")"
 				;;
-			"w")
-				printf "%s\n" "$content" > "$1"
-				;;
+			"x") exit ;;
+			"") ;;
 			*)
-				printf "%s: %s: No such command.\n" "$argv0" "$command"
+				printf "%s: %s: unrecognized command\n" "$0" "$command"
 				;;
 		esac
 	done
 
+	printf '%s\n' "$content"
+
 	shift
 done