/*
 * Copyright (c) 2016 Boucher, Antoni <bouanto@zoho.com>
 *
 * 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.
 */

use std::cell::Cell;
use std::rc::Rc;

use gdk::{EventKey, ModifierType, keyval_to_unicode};
use gdk::enums::key::{Escape, Tab, ISO_Left_Tab};
use gtk::{Inhibit, LabelExt};
use mg_settings::{self, EnumFromStr, EnumMetaData, SettingCompletion, SpecialCommand};
use mg_settings::key::Key::{self, Char};

use app::{
    Mg,
    Mode,
    Msg,
    BLOCKING_INPUT_MODE,
    COMMAND_MODE,
    INPUT_MODE,
};
use app::ShortcutCommand::{Complete, Incomplete};
use key_converter::gdk_key_to_key;

/// Convert a shortcut of keys to a `String`.
pub fn shortcut_to_string(keys: &[Key], show_count: bool) -> String {
    if show_count {
        let strings: Vec<_> = keys.iter().map(ToString::to_string).collect();
        strings.join("")
    }
    else {
        String::new()
    }
}

impl<COMM, SETT> Mg<COMM, SETT>
    where COMM: Clone + EnumFromStr + EnumMetaData + SpecialCommand + 'static,
          SETT: Default + EnumMetaData + mg_settings::settings::Settings + SettingCompletion + 'static,
{
    /// Add the key to the current shortcut.
    pub fn add_to_shortcut(&mut self, key: Key) {
        self.model.current_shortcut.push(key);
        self.update_shortcut_label();
    }

    /// Clear the current shortcut buffer.
    pub fn clear_shortcut(&mut self) {
        self.model.current_shortcut.clear();
        self.update_shortcut_label();
    }

    /// Handle a shortcut in input mode.
    pub fn handle_input_shortcut(&mut self, key: &EventKey) -> bool {
        if let Some(key) = gdk_key_to_key(key) {
            if self.model.shortcuts.contains_key(&key) {
                let answer = &self.model.shortcuts[&key].clone();
                self.model.shortcut_pressed = true;
                // set_dialog_answer() must be called after setting shortcut_pressed because this
                // method will set the answer to a Shortcut in this case.
                self.set_dialog_answer(answer);
                return true;
            }
        }
        false
    }

    /// Check if the key should be inhibitted for the shortcut.
    pub fn inhibit_handle_shortcut(current_mode: &Rc<Cell<Mode>>, key: &EventKey) -> Inhibit {
        let keyval = key.get_keyval();
        let alt_pressed = key.get_state().contains(ModifierType::MOD1_MASK);
        let control_pressed = key.get_state().contains(ModifierType::CONTROL_MASK);
        let shift_pressed = key.get_state().contains(ModifierType::SHIFT_MASK);
        let current_mode = current_mode.get();
        let is_char = keyval_to_unicode(keyval).is_some();
        let should_inhibit =
            current_mode == Mode::Normal || keyval == Escape ||
                ((current_mode == Mode::Command || current_mode == Mode::Input || current_mode == Mode::BlockingInput) &&
                 (alt_pressed || control_pressed || (!is_char && shift_pressed) || keyval == Tab ||
                  keyval == ISO_Left_Tab));
        Inhibit(should_inhibit)
    }

    /// Handle a possible input of a shortcut.
    pub fn handle_shortcut(&mut self, key: &EventKey) -> Option<Msg<COMM, SETT>> {
        let keyval = key.get_keyval();
        let alt_pressed = key.get_state().contains(ModifierType::MOD1_MASK);
        let control_pressed = key.get_state().contains(ModifierType::CONTROL_MASK);
        let shift_pressed = key.get_state().contains(ModifierType::SHIFT_MASK);
        if !self.model.entry_shown || alt_pressed || control_pressed || shift_pressed || keyval == Tab ||
            keyval == ISO_Left_Tab
        {
            if let Some(key) = gdk_key_to_key(key) {
                self.add_to_shortcut(key);
                let action = {
                    let mut current_mode = self.model.mode_string.clone();
                    // The input modes have the same mappings as the command mode.
                    if current_mode == INPUT_MODE || current_mode == BLOCKING_INPUT_MODE {
                        current_mode = COMMAND_MODE.to_string();
                    }
                    self.model.mappings.get(&current_mode.as_ref())
                        .and_then(|mappings| mappings.get(self.shortcut_without_prefix()).cloned())
                };
                if let Some(action) = action {
                    let prefix = self.shortcut_prefix();
                    // FIXME: this is copied a couple of lines below.
                    if !self.model.entry_shown {
                        // TODO: document why we need this.
                        self.reset();
                    }
                    self.clear_shortcut();
                    match self.action_to_command(&action) {
                        Complete(command) => {
                            return self.handle_command(Some(command), false, prefix);
                        },
                        Incomplete(command) => {
                            self.input_command(command);
                            self.show_completion();
                        },
                    }
                }
                else if self.no_possible_shortcut() {
                    let current_mode = self.model.current_mode.get();
                    if current_mode != Mode::Input && !self.model.entry_shown {
                        // TODO: document why we need this.
                        self.reset();
                    }
                    self.clear_shortcut();
                }
            }
        }
        None
    }

    /// Check if there are no possible shortcuts.
    fn no_possible_shortcut(&self) -> bool {
        if let Some(mappings) = self.model.mappings.get(&self.model.mode_string.as_ref()) {
            let shortcut = self.shortcut_without_prefix();
            for key in mappings.keys() {
                if key.starts_with(shortcut) {
                    return false;
                }
            }
        }
        true
    }

    fn shortcut_prefix(&self) -> Option<u32> {
        let mut digits = self.model.current_shortcut.iter()
            .take_while(is_digit)
            .peekable();
        if digits.peek().is_none() {
            None
        }
        else {
            let num = digits
                .fold(0, |num, key| {
                    if let Char(c) = *key {
                        if let Some(digit) = c.to_digit(10) {
                            return num * 10 + digit;
                        }
                    }
                    num
                });
            Some(num)
        }
    }

    fn shortcut_without_prefix(&self) -> &[Key] {
        let first = self.model.current_shortcut.first().cloned().unwrap_or(Char('0'));
        let start =
            if first == Char('0') {
                0
            }
            else {
                self.model.current_shortcut.iter()
                    .position(is_not_digit)
                    .unwrap_or_else(|| self.model.current_shortcut.len())
            };
        &self.model.current_shortcut[start..]
    }

    // TODO: remove this when updating the model in methods outside the trait will update the view.
    /// Update the shortcut label.
    fn update_shortcut_label(&self) {
        self.shortcut.widget().set_text(&shortcut_to_string(&self.model.current_shortcut, self.model.show_count));
    }
}

fn is_digit(key: &&Key) -> bool {
    !is_not_digit(key)
}

fn is_not_digit(key: &Key) -> bool {
    if let Char(c) = *key {
        !c.to_digit(10).is_some()
    }
    else {
        true
    }
}