use nix::fcntl::{fcntl, F_GETFL, F_SETFL, OFlag};
use nix::pty::{ForkptyResult, forkpty, PtyMaster};
use nix::unistd::{execv, read, write};

use minifb::{Key, KeyRepeat, Window, WindowOptions};

use std::vec;
use std::collections::HashMap;
use std::ffi::CString;
use std::fmt::Write;

use ttf_parser::{Face, OutlineBuilder, Rect};

use vte::{Params, Parser, Perform};

use zeno::{Mask, Transform};

// params
const SHELL: &str = "/home/andromeda/.nix-profile/bin/sh";
const FONT: &str = "/home/andromeda/.nix-profile/share/fonts/truetype/Miracode.ttf";

struct Buffer<T: std::clone::Clone> {
    buffer: Vec<T>,
    width: usize,
    height: usize,
}
impl<T: Clone> Buffer<T> {
    fn new(val: T, width: usize, height: usize) -> Self {
        Buffer {
            buffer: vec![val; width * height],
            width: width,
            height: height,
        }
    }
    fn get(&self, col: usize, row: usize) -> T {
        self.buffer.get(col + row * self.width).unwrap().clone()
    }
    fn set(&mut self, col: usize, row: usize, val: T) {
        self.buffer[col + row * self.width] = val;
    }
}

struct Cursor {
    col: usize,
    row: usize,
}

struct Model {
    screenbuffer: Buffer<u32>,
    buffer: Buffer<Option<char>>,
    cell: Rect,
    cursor: Cursor,
}
impl Model {
    // `cell` is the bbox of a cell
    // width and height are measured in cells
    fn new(cell: Rect, width: usize, height: usize, scale: f32) -> Self {
        Model {
            screenbuffer: Buffer::new(
                              0,
                              (cell.width() as f32 * width as f32 * scale) as usize,
                              (cell.height() as f32 * height as f32 * scale) as usize
                          ),
            buffer: Buffer::new(
                None,
                width,
                height
            ),
            cell: cell,
            cursor: Cursor {
                col: 0,
                row: 0,
            },
        }
    }

    // returns scale
    fn scale(&self) -> f32 {
        self.screenbuffer.height as f32 / (self.cell.height() as f32 * self.buffer.height as f32)
    }
}
impl Perform for Model {
    // draw a character to the screen and update states
    fn print(&mut self, c: char) {
        self.buffer.set(self.cursor.col, self.cursor.row, Some(c));
        self.cursor.col += 1;
        println!("[print] {:?}", c);
    }

    // execute a C0 or C1 control function
    fn execute(&mut self, byte: u8) {
        match byte {
            0x0D => self.cursor.col = 0,
            0x0A => self.cursor.row = self.cursor.row + 1,
            _ => (),
        }
        println!("[execute] {:02x}", byte);
    }

    // invoked when a final character arrives in first part of device control string
    fn hook(&mut self, params: &Params, intermediates: &[u8], ignore: bool, c: char) {
        println!(
            "[hook] params={:?}, intermediates={:?}, ignore={:?}, char={:?}",
            params, intermediates, ignore, c
        );
    }

    // pass bytes as part of a device control string to the handle chosen by hook
    // C0 controls are also passed to this handler
    fn put(&mut self, byte: u8) {
        println!("[put] {:02x}", byte);
    }

    // called when a device control string is terminated
    fn unhook(&mut self) {
        println!("[unhook]");
    }

    // dispatch an operating system command
    fn osc_dispatch(&mut self, params: &[&[u8]], bell_terminated: bool) {
        println!("[osc_dispatch] params={:?} bell_terminated={}", params, bell_terminated);
    }

    // a final character has arrived for a csi sequence
    fn csi_dispatch(&mut self, params: &Params, intermediates: &[u8], ignore: bool, c: char) {
        println!(
            "[csi_dispatch] params={:#?}, intermediates={:?}, ignore={:?}, char={:?}",
            params, intermediates, ignore, c
        );
    }

    // the final character of an escape sequence has arrived
    fn esc_dispatch(&mut self, intermediates: &[u8], ignore: bool, byte: u8) {
        println!(
            "[esc_dispatch] intermediates={:?}, ignore={:?}, byte={:02x}",
            intermediates, ignore, byte
        );
    }
}

// yoinked from tty_parser docs
struct Builder(String);
impl OutlineBuilder for Builder {
    fn move_to(&mut self, x: f32, y: f32) {
        write!(&mut self.0, "M {} {} ", x, y).unwrap();
    }

    fn line_to(&mut self, x: f32, y: f32) {
        write!(&mut self.0, "L {} {} ", x, y).unwrap();
    }

    fn quad_to(&mut self, x1: f32, y1: f32, x: f32, y: f32) {
        write!(&mut self.0, "Q {} {} {} {} ", x1, y1, x, y).unwrap();
    }

    fn curve_to(&mut self, x1: f32, y1: f32, x2: f32, y2: f32, x: f32, y: f32) {
        write!(&mut self.0, "C {} {} {} {} {} {} ", x1, y1, x2, y2, x, y).unwrap();
    }

    fn close(&mut self) {
        write!(&mut self.0, "Z ").unwrap();
    }
}

fn main() {
    // initialize the font
    let font_data = std::fs::read(FONT).unwrap();
    let face = Face::parse(&font_data, 0).unwrap();
    let font = generate_font(&face);

    let mut model = Model::new(
        Rect {
            x_min: 0,
            y_min: 0,
            x_max: face.height(),
            y_max: face.height(),
        },
        80,
        24,
        0.008,
    );

    // initialize window and its buffer
    let mut window = Window::new(
        "rust-term",
        model.screenbuffer.width,
        model.screenbuffer.height,
        WindowOptions::default(),
    ).unwrap();
    window.set_target_fps(60);

    let pty = spawn_pty(&SHELL).unwrap();
    fcntl(&pty, F_SETFL(OFlag::from_bits_truncate(fcntl(&pty, F_GETFL).unwrap()) | OFlag::O_NONBLOCK)).unwrap();

    let mut statemachine = Parser::new();

    let mut buf = [0u8; 2048];
    while window.is_open() && !window.is_key_down(Key::Escape) {
        // mask to render into
        let mut mask = vec![0u8; model.screenbuffer.width * model.screenbuffer.height];

        // render each char into mask
        for row in 0..model.buffer.height {
            for col in 0..model.buffer.width {
                if let Some(c) = model.buffer.get(col, row) {
                    Mask::new(font.get(&c).map_or("", |v| v)) // get svg
                        .transform(Some(
                                Transform::scale(model.scale(), -model.scale()) // scale it
                                .then_translate(
                                    col as f32 * model.cell.width() as f32 * model.scale(),
                                    // shift right by the cell width * the scale
                                    (1 + row) as f32 * model.scale() * model.cell.height() as f32,
                                    )
                                ))
                        .size(model.screenbuffer.width as u32, model.screenbuffer.height as u32)
                        .render_into(&mut mask, None); }
            };
        };

        // render in white/grayscale to screen
        for (p, m) in model.screenbuffer.buffer.iter_mut().zip(mask.iter()) {
            let m0 = *m as u32;
            *p = m0 << 16 | m0 << 8 | m0;
        }

        // update screen with buffer
        window.update_with_buffer(&model.screenbuffer.buffer, model.screenbuffer.width, model.screenbuffer.height).unwrap();


        // other stuff
        match read(&pty, &mut buf) {
            Ok(0) => (),
            Ok(n) => statemachine.advance(&mut model, &buf[..n]),
            Err(_e) => (),
        };

        let keys = window.get_keys_pressed(KeyRepeat::No);
        if !keys.is_empty() {
            let bytes: Vec<u8> = keys.iter()
                // TODO apply modifiers
                .map(|key| key_to_u8(*key, false, false))
                .collect();
            write(&pty, bytes.as_slice());
        };
    }
}

// forks a new pty and returns file descriptor of the master
fn spawn_pty(shell: &str) -> Option<PtyMaster> {
    // SAFETY safe unless os out of PTYs; incredibly unlikely
    match unsafe {forkpty(None, None)} {
        Ok(fork_pty_res) => match fork_pty_res {
            ForkptyResult::Parent {child:_, master} => {

                // SAFETY `master` is a valid PtyMaster
                return Some(unsafe{PtyMaster::from_owned_fd(master)});
            }
            ForkptyResult::Child =>{
                let _ = execv::<CString>(&CString::new(shell).unwrap(), &[]);
                return None;
            }
        },
        Err(_e) => return None,
    };
}

// WARNING not functional; missing some keys and also modifiers
fn key_to_u8(key: Key, shift: bool, ctrl: bool) -> u8 {
    let base = match key {
        Key::Key0 => b'0',
        Key::Key1 => b'1',
        Key::Key2 => b'2',
        Key::Key3 => b'3',
        Key::Key4 => b'4',
        Key::Key5 => b'5',
        Key::Key6 => b'6',
        Key::Key7 => b'7',
        Key::Key8 => b'8',
        Key::Key9 => b'9',
        Key::A => b'a',
        Key::B => b'b',
        Key::C => b'c',
        Key::D => b'd',
        Key::E => b'e',
        Key::F => b'f',
        Key::G => b'g',
        Key::H => b'h',
        Key::I => b'i',
        Key::J => b'j',
        Key::K => b'k',
        Key::L => b'l',
        Key::M => b'm',
        Key::N => b'n',
        Key::O => b'o',
        Key::P => b'p',
        Key::Q => b'q',
        Key::R => b'r',
        Key::S => b's',
        Key::T => b't',
        Key::U => b'u',
        Key::V => b'v',
        Key::W => b'w',
        Key::X => b'x',
        Key::Y => b'y',
        Key::Z => b'z',
        Key::F1 => 0,
        Key::F2 => 0,
        Key::F3 => 0,
        Key::F4 => 0,
        Key::F5 => 0,
        Key::F6 => 0,
        Key::F7 => 0,
        Key::F8 => 0,
        Key::F9 => 0,
        Key::F10 => 0,
        Key::F11 => 0,
        Key::F12 => 0,
        Key::F13 => 0,
        Key::F14 => 0,
        Key::F15 => 0,
        Key::Down => 0,
        Key::Left => 0,
        Key::Right => 0,
        Key::Up => 0,
        Key::Apostrophe => b'\'',
        Key::Backquote => b'`',
        Key::Backslash => b'\\',
        Key::Comma => b',',
        Key::Equal => b'=',
        Key::LeftBracket => b'[',
        Key::Minus => b'-',
        Key::Period => b'.',
        Key::RightBracket => b']',
        Key::Semicolon => b';',
        Key::Slash => b'/',
        Key::Backspace => 8,
        Key::Delete => 127,
        Key::End => 0,
        Key::Enter => b'\n',
        Key::Escape => 27,
        Key::Home => 0,
        Key::Insert => 0,
        Key::Menu => 0,
        Key::PageDown => 0,
        Key::PageUp => 0,
        Key::Pause => 0,
        Key::Space => b' ',
        Key::Tab => b'\t',
        Key::NumLock => 0,
        Key::CapsLock => 0,
        Key::ScrollLock => 0,
        Key::LeftShift => 0,
        Key::RightShift => 0,
        Key::LeftCtrl => 0,
        Key::RightCtrl => 0,
        Key::NumPad0 => 0,
        Key::NumPad1 => 0,
        Key::NumPad2 => 0,
        Key::NumPad3 => 0,
        Key::NumPad4 => 0,
        Key::NumPad5 => 0,
        Key::NumPad6 => 0,
        Key::NumPad7 => 0,
        Key::NumPad8 => 0,
        Key::NumPad9 => 0,
        Key::NumPadDot => 0,
        Key::NumPadSlash => 0,
        Key::NumPadAsterisk => 0,
        Key::NumPadMinus => 0,
        Key::NumPadPlus => 0,
        Key::NumPadEnter => 0,
        Key::LeftAlt => 0,
        Key::RightAlt => 0,
        Key::LeftSuper => 0,
        Key::RightSuper => 0,
        Key::Unknown => 0,
        Key::Count => 0,
    };

    let base_shift = if shift {
        match base {
            b'0' => b')',
            b'1' => b'!',
            b'2' => b'@',
            b'3' => b'#',
            b'4' => b'$',
            b'5' => b'%',
            b'6' => b'^',
            b'7' => b'&',
            b'8' => b'*',
            b'9' => b'(',
            b'a'..=b'z' => base - 32,
            b'\'' => b'"',
            b'`' => b'~',
            b'\\' => b'|',
            b',' => b'<',
            b'=' => b'+',
            b'[' => b'{',
            b'-' => b'_',
            b'.' => b'>',
            b']' => b'}',
            b';' => b':',
            b'/' => b'?',
            _ => base,
        }
    } else { base };

    let base_shift_ctrl = if ctrl {
        base_shift & 0x1F
    } else { base_shift };

    return base_shift_ctrl;
}

// creats a mapping from a `char` to its svg spec for a selection of characters
fn generate_font(face: &Face) -> HashMap<char, String> {
    let chars = 
        vec![
            '\'', '`', '\\', ',', '=', '[', '-', '.', ']', ';', '/',
            ')', '!', '@', '#', '$', '%', '^', '&', '*', '(', '"', '~', '|', '<', '+', '{', '_', '>', '}', ':', '?'
        ]
            .into_iter()
            .chain('a'..='z')
            .chain('A'..='Z')
            .chain('0'..='9');

    let mut hm = HashMap::new();

    for c in chars {
        let mut builder = Builder(String::new());
        face.outline_glyph(face.glyph_index(c).unwrap(), &mut builder).unwrap();
        hm.entry(c).insert_entry(builder.0);
    }

    hm
}