use glutin::event::{ElementState, Event, KeyEvent, WindowEvent};
use glutin::keyboard::Key;

use glutin::platform::modifier_supplement::KeyEventExtModifierSupplement;

use crate::bridge::{SerialCommand, UiCommand};
use crate::event_aggregator::EVENT_AGGREGATOR;
use crate::settings::SETTINGS;
use crate::window::KeyboardSettings;

enum KeyOrIme {
    Key(KeyEvent),
    Ime(String),
}
pub struct KeyboardManager {
    shift: bool,
    ctrl: bool,
    alt: bool,
    logo: bool,
    ignore_input_this_frame: bool,
    queued_key_or_ime_events: Vec<KeyOrIme>,
}

impl KeyboardManager {
    pub fn new() -> KeyboardManager {
        KeyboardManager {
            shift: false,
            ctrl: false,
            alt: false,
            logo: false,
            ignore_input_this_frame: false,
            queued_key_or_ime_events: Vec::new(),
        }
    }

    pub fn handle_event(&mut self, event: &Event<()>) {
        match event {
            Event::WindowEvent {
                event: WindowEvent::Focused(_focused),
                ..
            } => {
                // When window is just focused or lost it's focus, ignore keyboard events
                // that were submitted this frame
                self.ignore_input_this_frame = true;
            }
            Event::WindowEvent {
                event:
                    WindowEvent::KeyboardInput {
                        event: key_event, ..
                    },
                ..
            } => {
                // Store the event so that we can ignore it properly if the window was just
                // focused.
                self.queued_key_or_ime_events
                    .push(KeyOrIme::Key(key_event.clone()));
            }
            Event::WindowEvent {
                event: WindowEvent::ReceivedImeText(string),
                ..
            } => {
                self.queued_key_or_ime_events
                    .push(KeyOrIme::Ime(string.to_string()));
            }
            Event::WindowEvent {
                event: WindowEvent::ModifiersChanged(modifiers),
                ..
            } => {
                // Record the modifer states so that we can properly add them to the keybinding
                // text
                self.shift = modifiers.shift_key();
                self.ctrl = modifiers.control_key();
                self.alt = modifiers.alt_key();
                self.logo = modifiers.super_key();
            }
            Event::MainEventsCleared => {
                // And the window wasn't just focused.
                let settings = SETTINGS.get::<KeyboardSettings>();

                if !self.should_ignore_input(&settings) {
                    // If we have a keyboard event this frame
                    for key_or_ime_event in self.queued_key_or_ime_events.iter() {
                        match key_or_ime_event {
                            KeyOrIme::Key(key_event) => {
                                // And a key was pressed
                                if key_event.state == ElementState::Pressed {
                                    if let Some(keybinding) = self.maybe_get_keybinding(key_event) {
                                        EVENT_AGGREGATOR
                                            .send(UiCommand::Serial(SerialCommand::Keyboard(keybinding)));
                                    }
                                }
                            }
                            KeyOrIme::Ime(raw_input) => {
                                EVENT_AGGREGATOR
                                    .send(UiCommand::Serial(SerialCommand::Keyboard(raw_input.to_string())));
                            }
                        }
                    }
                }

                // Regardless of whether this was a valid keyboard input or not, rest ignoring and
                // whatever event was queued.
                self.ignore_input_this_frame = false;
                self.queued_key_or_ime_events.clear();
            }
            _ => {}
        }
    }

    fn should_ignore_input(&self, settings: &KeyboardSettings) -> bool {
        self.ignore_input_this_frame || (self.logo && !settings.use_logo)
    }

    fn maybe_get_keybinding(&self, key_event: &KeyEvent) -> Option<String> {
        // Determine if this key event represents a key which won't ever
        // present text.

        if let Some(key_text) = is_control_key(key_event.logical_key) {
            Some(self.format_keybinding_string(true, true, key_text))
        } else {
            let is_dead_key =
                key_event.text_with_all_modifiers().is_some() && key_event.text.is_none();
            let key_text = if (self.alt || is_dead_key) && cfg!(target_os = "macos") {
                key_event.text_with_all_modifiers()
            } else {
                key_event.text
            };

            if let Some(key_text) = key_text {
                // This is not a control key, so we rely upon winit to determine if
                // this is a deadkey or not.
                let keybinding_string = if let Some(escaped_text) = is_special(key_text) {
                    self.format_keybinding_string(true, false, escaped_text)
                } else {
                    self.format_keybinding_string(false, false, key_text)
                };

                Some(keybinding_string)
            } else {
                None
            }
        }
    }

    fn format_keybinding_string(&self, special: bool, use_shift: bool, text: &str) -> String {
        let special = special || self.ctrl || use_alt(self.alt) || self.logo;

        let open = or_empty(special, "<");
        let modifiers = self.format_modifier_string(use_shift);
        let close = or_empty(special, ">");

        open.to_owned() + &modifiers + text + close
    }

    pub fn format_modifier_string(&self, use_shift: bool) -> String {
        let shift = or_empty(self.shift && use_shift, "S-");
        let ctrl = or_empty(self.ctrl, "C-");
        let alt = or_empty(use_alt(self.alt), "M-");
        let logo = or_empty(self.logo, "D-");

        shift.to_owned() + ctrl + alt + logo
    }
}

#[cfg(not(target_os = "macos"))]
fn use_alt(alt: bool) -> bool {
    alt
}

// The option or alt key is used on Macos for character set changes
// and does not operate the same as other systems.
#[cfg(target_os = "macos")]
fn use_alt(_: bool) -> bool {
    false
}

fn or_empty(condition: bool, text: &str) -> &str {
    if condition {
        text
    } else {
        ""
    }
}

fn is_control_key(key: Key<'static>) -> Option<&str> {
    match key {
        Key::Backspace => Some("BS"),
        Key::Escape => Some("Esc"),
        Key::Delete => Some("Del"),
        Key::ArrowUp => Some("Up"),
        Key::ArrowDown => Some("Down"),
        Key::ArrowLeft => Some("Left"),
        Key::ArrowRight => Some("Right"),
        Key::F1 => Some("F1"),
        Key::F2 => Some("F2"),
        Key::F3 => Some("F3"),
        Key::F4 => Some("F4"),
        Key::F5 => Some("F5"),
        Key::F6 => Some("F6"),
        Key::F7 => Some("F7"),
        Key::F8 => Some("F8"),
        Key::F9 => Some("F9"),
        Key::F10 => Some("F10"),
        Key::F11 => Some("F11"),
        Key::F12 => Some("F12"),
        Key::Insert => Some("Insert"),
        Key::Home => Some("Home"),
        Key::End => Some("End"),
        Key::PageUp => Some("PageUp"),
        Key::PageDown => Some("PageDown"),
        Key::Tab => Some("Tab"),
        _ => None,
    }
}

fn is_special(text: &str) -> Option<&str> {
    match text {
        " " => Some("Space"),
        "<" => Some("lt"),
        "\\" => Some("Bslash"),
        "|" => Some("Bar"),
        "\t" => Some("Tab"),
        "\n" => Some("CR"),
        _ => None,
    }
}