use crate::{error::Error, key, log::*};
use anyhow::{Context, Result};
use windows::Win32::Foundation::HANDLE;
use windows::Win32::System::Console;

fn log_input_mode(mode: Console::CONSOLE_MODE) {
    // Characters read by the ReadFile or ReadConsole function are written to the active screen
    // buffer as they are typed into the console. This mode can be used only if the
    // ENABLE_LINE_INPUT mode is also enabled.
    if (mode & Console::ENABLE_ECHO_INPUT).0 > 0 {
        debug!("Echo Input:             Enabled");
    } else {
        debug!("Echo Input:             Disabled");
    }

    // When enabled, text entered in a console window will be inserted at the current cursor
    // location and all text following that location will not be overwritten. When disabled, all
    // following text will be overwritten.
    if (mode & Console::ENABLE_INSERT_MODE).0 > 0 {
        debug!("Insert Mode:            Enabled");
    } else {
        debug!("Insert Mode:            Disabled");
    }

    // The ReadFile or ReadConsole function returns only when a carriage return character is read.
    // If this mode is disabled, the functions return when one or more characters are available.
    if (mode & Console::ENABLE_LINE_INPUT).0 > 0 {
        debug!("Line Input Mode:        Enabled");
    } else {
        debug!("Line Input Mode:        Disabled");
    }

    // If the mouse pointer is within the borders of the console window and the window has the
    // keyboard focus, mouse events generated by mouse movement and button presses are placed in
    // the input buffer. These events are discarded by ReadFile or ReadConsole, even when this mode
    // is enabled. The ReadConsoleInput function can be used to read MOUSE_EVENT input records from
    // the input buffer.
    if (mode & Console::ENABLE_MOUSE_INPUT).0 > 0 {
        debug!("Mouse Input:            Enabled");
    } else {
        debug!("Mouse Input:            Disabled");
    }

    // CTRL+C is processed by the system and is not placed in the input buffer. If the input buffer
    // is being read by ReadFile or ReadConsole, other control keys are processed by the system and
    // are not returned in the ReadFile or ReadConsole buffer. If the ENABLE_LINE_INPUT mode is
    // also enabled, backspace, carriage return, and line feed characters are handled by the
    // system.
    if (mode & Console::ENABLE_PROCESSED_INPUT).0 > 0 {
        debug!("Processed Input:        Enabled");
    } else {
        debug!("Processed Input:        Disabled");
    }

    // This flag enables the user to use the mouse to select and edit text. To enable this mode,
    // use ENABLE_QUICK_EDIT_MODE | ENABLE_EXTENDED_FLAGS. To disable this mode, use
    // ENABLE_EXTENDED_FLAGS without this flag.
    if (mode & Console::ENABLE_QUICK_EDIT_MODE).0 > 0 {
        debug!("Quick Edit Mode:        Enabled");
    } else {
        debug!("Quick Edit Mode:        Disabled");
    }

    // User interactions that change the size of the console screen buffer are reported in the
    // console's input buffer. Information about these events can be read from the input buffer by
    // applications using the ReadConsoleInput function, but not by those using ReadFile or
    // ReadConsole.
    if (mode & Console::ENABLE_WINDOW_INPUT).0 > 0 {
        debug!("Window Input:           Enabled");
    } else {
        debug!("Window Input:           Disabled");
    }

    // Setting this flag directs the Virtual Terminal processing engine to convert user input
    // received by the console window into Console Virtual Terminal Sequences that can be retrieved
    // by a supporting application through ReadFile or ReadConsole functions.
    //
    // The typical usage of this flag is intended in conjunction with
    // ENABLE_VIRTUAL_TERMINAL_PROCESSING on the output handle to connect to an application that
    // communicates exclusively via virtual terminal sequences.
    if (mode & Console::ENABLE_VIRTUAL_TERMINAL_INPUT).0 > 0 {
        debug!("Virtual Terminal Input: Enabled");
    } else {
        debug!("Virtual Terminal Input: Disabled");
    }
}

fn stdin_handle() -> Result<HANDLE> {
    unsafe {
        let handle = Console::GetStdHandle(Console::STD_INPUT_HANDLE)
            .context("unable to get stdin handle")?;
        Ok(handle)
    }
}

fn setup_stdin() -> Result<()> {
    let mut mode = Console::CONSOLE_MODE(0);
    unsafe {
        Console::SetConsoleCP(65001);

        let handle = stdin_handle()?;
        Error::check(Console::GetConsoleMode(handle, &mut mode))?;

        // allow terminal input characters
        mode |= Console::ENABLE_VIRTUAL_TERMINAL_INPUT;

        // disable automatic processing of CTRL+C, we'll handle it ourselves
        mode &= !Console::ENABLE_PROCESSED_INPUT;

        // disable line mode to get every input as its pressed
        mode &= !Console::ENABLE_LINE_INPUT;

        // disable automatic echoing of inputs
        mode &= !Console::ENABLE_ECHO_INPUT;

        // enable mouse input
        mode |= Console::ENABLE_MOUSE_INPUT;

        Error::check(Console::SetConsoleMode(handle, mode))?;
        Error::check(Console::GetConsoleMode(handle, &mut mode))?;
        debug!("Stdin details:");
        log_input_mode(mode);
    }
    Ok(())
}

pub struct Reader {
    input: HANDLE,
    // this area in memory is where the Windows API will write events read off of the keyboard.
    buf: [Console::INPUT_RECORD; 100],
    // the number of valid input record items in the buf since last read
    buf_len: u32,
    // the position of our current indexer into the input record buffer
    buf_idx: usize,
}

impl Reader {
    pub fn new() -> Result<Self> {
        setup_stdin()?;
        Ok(Self {
            buf: [Console::INPUT_RECORD::default(); 100],
            buf_len: 0,
            buf_idx: 0,
            input: stdin_handle()?,
        })
    }

    pub fn next(&mut self) -> Result<Event> {
        let rec = self.next_rec()?;
        if rec.EventType as u32 == Console::KEY_EVENT {
            unsafe {
                let event = rec.Event.KeyEvent;
                if event.wVirtualKeyCode == 0 && event.uChar.UnicodeChar == 27 {
                    return Ok(self.next_escape_sequence()?);
                }
            }
        }
        Ok(rec.into())
    }

    fn next_rec(&mut self) -> Result<Console::INPUT_RECORD> {
        if self.buf_idx as u32 >= self.buf_len {
            unsafe {
                Error::check(Console::ReadConsoleInputA(
                    self.input,
                    &mut self.buf,
                    &mut self.buf_len,
                ))?;
            }
            self.buf_idx = 0;
        }

        let rec = self.buf[self.buf_idx];
        self.buf_idx += 1;
        return Ok(rec);
    }

    fn next_escape_sequence(&mut self) -> Result<Event> {
        self.take_bracket()?;
        match self.next_escape_char()? {
            'D' => Ok(Event::Left),
            e => Err(Error::input_error(format!("unexpected escape char: {}", e)).into()),
        }
    }

    fn take_bracket(&mut self) -> Result<()> {
        let rec = self.next_rec()?;
        if rec.EventType as u32 != Console::KEY_EVENT {
            Err(Error::input_error("failed to read escape sequence: not a key event").into())
        } else {
            unsafe {
                let event = rec.Event.KeyEvent;
                if event.wVirtualKeyCode == 0 && event.uChar.UnicodeChar == 91 {
                    Ok(())
                } else {
                    Err(Error::input_error("failed to read escape sequence: not a [").into())
                }
            }
        }
    }

    fn next_escape_char(&mut self) -> Result<char> {
        let rec = self.next_rec()?;
        if rec.EventType as u32 != Console::KEY_EVENT {
            Err(
                Error::input_error("failed to read char in escape sequence: not a key event")
                    .into(),
            )
        } else {
            unsafe {
                let n = rec.Event.KeyEvent.uChar.UnicodeChar as u32;
                let c = char::from_u32(n);
                c.ok_or_else(|| {
                    let msg = format!("escape key value is not a valid unicode character: {}", n);
                    Error::input_error(msg).into()
                })
            }
        }
    }
}

#[derive(Debug)]
pub enum Event {
    Focus(bool),
    Menu(u32),
    Key(key::Event),
    Mouse { x: i16, y: i16 },
    Size,
    Left,
}

const ALT_KEYS: u32 = 0x0002 | 0x0001;
const CTRL_KEYS: u32 = 0x0008 | 0x0004;
const SHIFT_PRESSED: u32 = 0x0010;

impl From<Console::INPUT_RECORD> for Event {
    fn from(rec: Console::INPUT_RECORD) -> Self {
        // This is documented here:
        // https://learn.microsoft.com/en-us/windows/console/input-record-str
        match rec.EventType as u32 {
            Console::FOCUS_EVENT => unsafe {
                let event = rec.Event.FocusEvent;
                Event::Focus(event.bSetFocus.as_bool())
            },
            Console::MENU_EVENT => unsafe {
                let event = rec.Event.MenuEvent;
                Event::Menu(event.dwCommandId)
            },
            Console::KEY_EVENT => {
                // https://learn.microsoft.com/en-us/windows/win32/inputdev/virtual-key-codes
                unsafe {
                    let event = rec.Event.KeyEvent;
                    let mstate = event.dwControlKeyState;
                    let c = char::from_u32(event.uChar.UnicodeChar as u32).unwrap_or('💀');

                    Event::Key(key::Event {
                        down: event.bKeyDown.as_bool(),
                        repeats: event.wRepeatCount,
                        code: event.wVirtualKeyCode,
                        alt: mstate & ALT_KEYS > 0,
                        ctrl: mstate & CTRL_KEYS > 0,
                        shift: mstate & SHIFT_PRESSED > 0,
                        char: c,
                    })
                }
            }
            Console::MOUSE_EVENT => {
                // OK I think it's safe to ignore these events since we're using the terminal
                // escape sequences. I think we never see them because terminal.exe is going to
                // turn mouse events into virtual terminal sequences anyway
                unsafe {
                    let event = rec.Event.MouseEvent;
                    // pub dwMousePosition: COORD, i16 i16
                    // pub dwButtonState: u32,
                    // pub dwControlKeyState: u32,
                    // pub dwEventFlags: u32,
                    Event::Mouse {
                        x: event.dwMousePosition.X,
                        y: event.dwMousePosition.Y,
                    }
                }
            }
            Console::WINDOW_BUFFER_SIZE_EVENT => Event::Size,
            _ => {
                unreachable!()
            }
        }
    }
}