/*
 * This file is part of espanso.
 *
 * Copyright (C) 2019-2021 Federico Terzi
 *
 * espanso is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * espanso 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with espanso.  If not, see <https://www.gnu.org/licenses/>.
 */

use std::{
  ffi::CStr,
  sync::{
    mpsc::{channel, Receiver, Sender},
    Arc, Mutex,
  },
};

use lazycell::LazyCell;
use log::{error, trace, warn};

use anyhow::Result;
use thiserror::Error;

use crate::event::Variant::*;
use crate::event::{InputEvent, Key, KeyboardEvent, Variant};
use crate::event::{Key::*, MouseButton, MouseEvent};
use crate::{event::Status::*, Source, SourceCallback};

const INPUT_EVENT_TYPE_KEYBOARD: i32 = 1;
const INPUT_EVENT_TYPE_MOUSE: i32 = 2;

const INPUT_STATUS_PRESSED: i32 = 1;
const INPUT_STATUS_RELEASED: i32 = 2;

const INPUT_MOUSE_LEFT_BUTTON: i32 = 1;
const INPUT_MOUSE_RIGHT_BUTTON: i32 = 2;
const INPUT_MOUSE_MIDDLE_BUTTON: i32 = 3;

// Take a look at the native.h header file for an explanation of the fields
#[repr(C)]
pub struct RawInputEvent {
  pub event_type: i32,

  pub buffer: [u8; 24],
  pub buffer_len: i32,

  pub key_code: i32,
  pub status: i32,
}

#[allow(improper_ctypes)]
#[link(name = "espansodetect", kind = "static")]
extern "C" {
  pub fn detect_initialize(callback: extern "C" fn(event: RawInputEvent));
}

lazy_static! {
  static ref CURRENT_SENDER: Arc<Mutex<Option<Sender<InputEvent>>>> = Arc::new(Mutex::new(None));
}

extern "C" fn native_callback(raw_event: RawInputEvent) {
  let lock = CURRENT_SENDER
    .lock()
    .expect("unable to acquire CocoaSource sender lock");
  if let Some(sender) = lock.as_ref() {
    let event: Option<InputEvent> = raw_event.into();
    if let Some(event) = event {
      if let Err(error) = sender.send(event) {
        error!("Unable to send event to Cocoa Sender: {}", error);
      }
    } else {
      trace!("Unable to convert raw event to input event");
    }
  } else {
    warn!("Lost raw event, as Cocoa Sender is not available");
  }
}

pub struct CocoaSource {
  receiver: LazyCell<Receiver<InputEvent>>,
}

#[allow(clippy::new_without_default)]
impl CocoaSource {
  pub fn new() -> CocoaSource {
    Self {
      receiver: LazyCell::new(),
    }
  }
}

impl Source for CocoaSource {
  fn initialize(&mut self) -> Result<()> {
    let (sender, receiver) = channel();

    // Set the global sender
    {
      let mut lock = CURRENT_SENDER
        .lock()
        .expect("unable to acquire CocoaSource sender lock during initialization");
      *lock = Some(sender);
    }

    unsafe { detect_initialize(native_callback) };

    if self.receiver.fill(receiver).is_err() {
      error!("Unable to set CocoaSource receiver");
      return Err(CocoaSourceError::Unknown().into());
    }

    Ok(())
  }

  fn eventloop(&self, event_callback: SourceCallback) -> Result<()> {
    if let Some(receiver) = self.receiver.borrow() {
      loop {
        let event = receiver.recv();
        match event {
          Ok(event) => {
            event_callback(event);
          }
          Err(error) => {
            error!("CocoaSource receiver reported error: {}", error);
            break;
          }
        }
      }
    } else {
      error!("Unable to start event loop if CocoaSource receiver is null");
      return Err(CocoaSourceError::Unknown().into());
    }

    Ok(())
  }
}

impl Drop for CocoaSource {
  fn drop(&mut self) {
    // Reset the global sender
    {
      let mut lock = CURRENT_SENDER
        .lock()
        .expect("unable to acquire CocoaSource sender lock during initialization");
      *lock = None;
    }
  }
}

#[derive(Error, Debug)]
pub enum CocoaSourceError {
  #[error("unknown error")]
  Unknown(),
}

impl From<RawInputEvent> for Option<InputEvent> {
  fn from(raw: RawInputEvent) -> Option<InputEvent> {
    let status = match raw.status {
      INPUT_STATUS_RELEASED => Released,
      INPUT_STATUS_PRESSED => Pressed,
      _ => Pressed,
    };

    match raw.event_type {
      // Keyboard events
      INPUT_EVENT_TYPE_KEYBOARD => {
        let (key, variant) = key_code_to_key(raw.key_code);

        let value = if raw.buffer_len > 0 {
          let raw_string_result =
            CStr::from_bytes_with_nul(&raw.buffer[..((raw.buffer_len + 1) as usize)]);
          match raw_string_result {
            Ok(c_string) => {
              let string_result = c_string.to_str();
              match string_result {
                Ok(value) => Some(value.to_string()),
                Err(err) => {
                  warn!("CocoaSource event utf8 conversion error: {}", err);
                  None
                }
              }
            }
            Err(err) => {
              trace!("Received malformed event buffer: {}", err);
              None
            }
          }
        } else {
          None
        };

        return Some(InputEvent::Keyboard(KeyboardEvent {
          key,
          value,
          status,
          variant,
        }));
      }
      // Mouse events
      INPUT_EVENT_TYPE_MOUSE => {
        let button = raw_to_mouse_button(raw.key_code);

        if let Some(button) = button {
          return Some(InputEvent::Mouse(MouseEvent { button, status }));
        }
      }
      _ => {}
    }

    None
  }
}

// Mappings from: https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key/Key_Values
fn key_code_to_key(key_code: i32) -> (Key, Option<Variant>) {
  match key_code {
    // Modifiers
    0x3A => (Alt, Some(Left)),
    0x3D => (Alt, Some(Right)),
    0x39 => (CapsLock, None), // TODO
    0x3B => (Control, Some(Left)),
    0x3E => (Control, Some(Right)),
    0x37 => (Meta, Some(Left)),
    0x36 => (Meta, Some(Right)),
    0x38 => (Shift, Some(Left)),
    0x3C => (Shift, Some(Right)),

    // Whitespace
    0x24 => (Enter, None),
    0x30 => (Tab, None),
    0x31 => (Space, None),

    // Navigation
    0x7D => (ArrowDown, None),
    0x7B => (ArrowLeft, None),
    0x7C => (ArrowRight, None),
    0x7E => (ArrowUp, None),
    0x77 => (End, None),
    0x73 => (Home, None),
    0x79 => (PageDown, None),
    0x74 => (PageUp, None),

    // UI
    0x35 => (Escape, None),

    // Editing keys
    0x33 => (Backspace, None),

    // Function keys
    0x7A => (F1, None),
    0x78 => (F2, None),
    0x63 => (F3, None),
    0x76 => (F4, None),
    0x60 => (F5, None),
    0x61 => (F6, None),
    0x62 => (F7, None),
    0x64 => (F8, None),
    0x65 => (F9, None),
    0x6D => (F10, None),
    0x67 => (F11, None),
    0x6F => (F12, None),
    0x69 => (F13, None),
    0x6B => (F14, None),
    0x71 => (F15, None),
    0x6A => (F16, None),
    0x40 => (F17, None),
    0x4F => (F18, None),
    0x50 => (F19, None),
    0x5A => (F20, None),

    // Other keys, includes the raw code provided by the operating system
    _ => (Other(key_code), None),
  }
}

fn raw_to_mouse_button(raw: i32) -> Option<MouseButton> {
  match raw {
    INPUT_MOUSE_LEFT_BUTTON => Some(MouseButton::Left),
    INPUT_MOUSE_RIGHT_BUTTON => Some(MouseButton::Right),
    INPUT_MOUSE_MIDDLE_BUTTON => Some(MouseButton::Middle),
    _ => None,
  }
}

#[cfg(test)]
mod tests {
  use std::ffi::CString;

  use super::*;

  fn default_raw_input_event() -> RawInputEvent {
    RawInputEvent {
      event_type: INPUT_EVENT_TYPE_KEYBOARD,
      buffer: [0; 24],
      buffer_len: 0,
      key_code: 0,
      status: INPUT_STATUS_PRESSED,
    }
  }

  #[test]
  fn raw_to_input_event_keyboard_works_correctly() {
    let c_string = CString::new("k".to_string()).unwrap();
    let mut buffer: [u8; 24] = [0; 24];
    buffer[..1].copy_from_slice(c_string.as_bytes());

    let mut raw = default_raw_input_event();
    raw.buffer = buffer;
    raw.buffer_len = 1;
    raw.status = INPUT_STATUS_RELEASED;
    raw.key_code = 40;

    let result: Option<InputEvent> = raw.into();
    assert_eq!(
      result.unwrap(),
      InputEvent::Keyboard(KeyboardEvent {
        key: Other(40),
        status: Released,
        value: Some("k".to_string()),
        variant: None,
      })
    );
  }

  #[test]
  fn raw_to_input_event_mouse_works_correctly() {
    let mut raw = default_raw_input_event();
    raw.event_type = INPUT_EVENT_TYPE_MOUSE;
    raw.status = INPUT_STATUS_RELEASED;
    raw.key_code = INPUT_MOUSE_RIGHT_BUTTON;

    let result: Option<InputEvent> = raw.into();
    assert_eq!(
      result.unwrap(),
      InputEvent::Mouse(MouseEvent {
        status: Released,
        button: MouseButton::Right,
      })
    );
  }
}