/*
 * Copyright (c) 2023 Marceline Cramer
 * Copyright (c) 2023 Emma Tebibyte <emma@tebibyte.media>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Affero General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see https://www.gnu.org/licenses/.
 */

use std::collections::HashMap;

use crossterm::event::KeyCode;
use toml::{Table, Value};

use crate::actions::{load_actions, Action};

pub type Key = KeyCode;

pub type KeyMap = HashMap<Key, Keybind>;

pub struct Keybinds {
    pub normal: ModeKeys,
    pub insert: ModeKeys,
    pub visual: ModeKeys,
}

impl Default for Keybinds {
    fn default() -> Self {
        use crate::actions::*;
        use KeyCode::*;

        let basic_nav = &[
            (Esc, normal_mode as Action),
            (Left, move_char_left),
            (Down, move_line_down),
            (Up, move_line_up),
            (Right, move_char_right),
            (PageUp, page_up),
            (PageDown, page_down),
            (Home, goto_line_start),
            (End, goto_line_end),
        ];

        let goto_keys = &[
            (Char('h'), goto_line_start as Action),
            (Char('l'), goto_line_end),
            (Char('s'), goto_first_nonwhitespace),
            (Char('g'), goto_file_start),
            (Char('e'), goto_file_end),
        ];

        let normalish_keys = [
            (Char(':'), command_mode as Action),
            (Char('$'), goto_line_end),
            (Char('0'), goto_line_start),
            (Char('^'), goto_first_nonwhitespace),
            (Char('h'), move_char_left),
            (Char('j'), move_line_down),
            (Char('k'), move_line_up),
            (Char('l'), move_char_right),
            (Char('w'), move_next_word_start),
            (Char('b'), move_prev_word_start),
            (Char('e'), move_next_word_end),
            (Char('W'), move_next_long_word_start),
            (Char('B'), move_prev_long_word_start),
            (Char('E'), move_next_long_word_end),
            (Char('i'), insert_mode),
            (Char('a'), append_mode),
            (Char('I'), insert_at_line_start),
            (Char('A'), insert_at_line_end),
            (Char('o'), open_below),
            (Char('O'), open_above),
            (Char('u'), undo),
            (Char('U'), redo),
            (Char('d'), delete_char_forward),
        ]
        .iter()
        .chain(basic_nav);

        let normalish_submodes: HashMap<Key, KeyMap> =
            [(Char('g'), key_map_from_iter(goto_keys))].into();

        let insert_keys = [
            (Backspace, delete_char_backward as Action),
            (Delete, delete_char_forward),
            (Enter, insert_newline),
        ]
        .iter()
        .chain(basic_nav);

        Self {
            normal: ModeKeys {
                submodes: normalish_submodes.clone(),
                map: key_map_from_iter(normalish_keys.clone()),
            },
            insert: ModeKeys {
                submodes: [].into(),
                map: key_map_from_iter(insert_keys),
            },
            visual: ModeKeys {
                submodes: normalish_submodes,
                map: key_map_from_iter(normalish_keys.clone()),
            },
        }
    }
}

#[derive(Clone, Default)]
pub struct ModeKeys {
    pub submodes: HashMap<Key, KeyMap>,
    pub map: KeyMap,
}

impl ModeKeys {
    pub fn apply_table(values: Table) -> Result<Self, String> {
        let mut keys = Self::default();

        for (key, value) in values {
            let key = parse_key(&key)?;
            match value {
                Value::Table(table) => {
                    let map = parse_key_map(table)?;
                    keys.submodes.insert(key, map);
                }
                Value::String(keybind) => {
                    let bind = Keybind::try_from(keybind.as_str())?;
                    keys.map.insert(key, bind);
                }
                value => return Err(format!("Expected string or table but got {:?}", value)),
            }
        }

        Ok(keys)
    }
}

#[derive(Clone)]
pub enum Keybind {
    Action(Action),
    Command(String),
}

impl TryFrom<Value> for Keybind {
    type Error = String;

    fn try_from(value: Value) -> Result<Self, String> {
        value
            .as_str()
            .ok_or_else(|| format!("Expected string but got {:?}", value))?
            .try_into()
    }
}

impl TryFrom<&str> for Keybind {
    type Error = String;

    fn try_from(keybind: &str) -> Result<Self, String> {
        if keybind.starts_with(':') {
            Ok(Keybind::Command(keybind[1..].to_string()))
        } else {
            // TODO static once cell
            let actions = load_actions();
            actions
                .get(keybind)
                .map(|cb| Keybind::Action(cb.clone()))
                .ok_or_else(|| format!("Couldn't find action {:?}", keybind))
        }
    }
}

pub fn key_map_from_iter<'a, T>(iter: T) -> KeyMap
where
    T: IntoIterator<Item = &'a (Key, Action)>,
{
    let mut map = KeyMap::new();
    for (key, action) in iter {
        map.insert(*key, Keybind::Action(*action));
    }

    map
}

pub fn parse_key_map(values: Table) -> Result<KeyMap, String> {
    let mut map = KeyMap::with_capacity(values.len());

    for (key, value) in values {
        let key = parse_key(&key)?;
        let bind = Keybind::try_from(value)?;
        map.insert(key, bind);
    }

    Ok(map)
}

pub fn parse_key(key: &str) -> Result<Key, String> {
    use KeyCode::*;
    let key = match key {
        key if key.len() == 1 => Char(key.chars().nth(0).unwrap()),
        "backspace" => Backspace,
        "space" => Char(' '),
        "ret" => Enter,
        "minus" => Char('-'),
        "left" => Left,
        "right" => Right,
        "up" => Up,
        "down" => Down,
        "home" => Home,
        "end" => End,
        "pageup" => PageUp,
        "pagedown" => PageDown,
        "tab" => Tab,
        "del" => Delete,
        "ins" => Insert,
        "null" => Null,
        "esc" => Esc,
        key => return Err(format!("Unrecognized key name {:?}", key)),
    };

    Ok(key)
}