use nix::fcntl::{F_GETFL, F_SETFL, OFlag, fcntl};
use nix::pty::{ForkptyResult, PtyMaster, forkpty};
use nix::sys::wait::{WaitPidFlag, WaitStatus, waitpid};
use nix::unistd::{Pid, execve, read, write};

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

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

use ttf_parser::Face;

use vte::Parser;

use zeno::{Fill, Mask, Stroke, Style, Transform};

mod config;
use config::*;

mod structs;
use structs::*;

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

    let mut model = Model::new(
        MODEL_WIDTH,
        MODEL_HEIGHT,
        MODEL_SCALE,
    );

    // initialize window and its buffer
    let mut window = Window::new(
        WINDOW_TITLE,
        model.screenbuffer_width(),
        model.screenbuffer_height(),
        WindowOptions::default(),
    )
    .unwrap();
    window.set_target_fps(WINDOW_TARGET_FPS);

    // pty and pid of child
    let (pty, child) = spawn_pty().unwrap();

    // set pty as non-blocking
    fcntl(
        &pty,
        F_SETFL(OFlag::from_bits_truncate(fcntl(&pty, F_GETFL).unwrap()) | OFlag::O_NONBLOCK),
    )
    .unwrap();

    // parser for `vte`
    let mut statemachine = Parser::new();

    // buffers for input and writing to the screen
    let mut buf = [0u8; INPUT_BUFFER_SIZE];
    let mut mask = vec![0u8; model.screenbuffer_width() * model.screenbuffer_height()];

    // window is open, child is alive
    while window.is_open()
        && waitpid(child, Some(WaitPidFlag::WNOHANG)) == Ok(WaitStatus::StillAlive)
    {
        // clear mask from last frame
        mask.fill(0u8);

        // render each char into mask
        // remember that `model.buffer` is always 1-indexed
        for row in 1..=model.buffer_height() {
            for col in 1..=model.buffer_width() {
                if let Some(chr) = model.buffer_at(row, col).chr() {
                    Mask::new(font.get(&chr).map_or("", |v| v)) // get svg
                        .transform(Some(
                            Transform::scale(model.scale(), -model.scale()) // scale it
                                .then_translate(
                                    // col and row are 1 indexed; we want col to be 0 indexed bc
                                    // this refers to the bottom left corner of each cell, or at
                                    // least behaves like it
                                    (col as f32 - 1.0) * model.cell_width() as f32 * model.scale(),
                                    row as f32 * model.scale() * model.cell_height() as f32,
                                ),
                        ))
                        .style(
                            match model.buffer_at(row, col).char_attr() {
                                CharAttr::Normal => Style::Fill(Fill::NonZero),
                                CharAttr::Bold => Style::Stroke(Stroke::new(500.0)),
                                CharAttr::Inverse => Style::Stroke(Stroke::new(50.0)),
                                _ => Style::Stroke(Stroke::new(50.0)),
                            }
                        )
                        .size(
                            // fits transformed svg to screen, or trims excess
                            model.screenbuffer_width() as u32,
                            model.screenbuffer_height() as u32,
                        )
                        // writes it to mask
                        .render_into(&mut mask, None);
                }
            }
        }

        // render mask onto screen
        model.set_screenbuffer(&mask);

        // update screen with new screenbuffer
        window
            .update_with_buffer(
                model.screenbuffer_buffer(),
                model.screenbuffer_width(),
                model.screenbuffer_height(),
            )
            .unwrap();

        // other stuff
        match read(&pty, &mut buf) {
            Ok(0) => (),
            // if there are new chars, feed them to `vte`
            Ok(n) => statemachine.advance(&mut model, &buf[..n]),
            Err(_e) => (),
        };

        let keys = window.get_keys_pressed(KeyRepeat::Yes);
        let shift = window.is_key_down(Key::LeftShift)
            || window.is_key_down(Key::RightShift)
            || window.is_key_down(Key::CapsLock);
        let ctrl = window.is_key_down(Key::LeftCtrl) || window.is_key_down(Key::RightCtrl);
        // writes keystrokes to buffer, will be processed by vte next frame
        if !keys.is_empty() {
            let bytes: Vec<u8> = keys
                .iter()
                .map(|key| {
                    key_to_u8(
                        *key, // key
                        shift, ctrl,
                    )
                })
                .filter(|v| *v != 0u8)
                .collect();
            write(&pty, bytes.as_slice());
        };
    }
}

// forks a new pty and returns file descriptor of the master
fn spawn_pty() -> Option<(PtyMaster, Pid)> {
    // 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) }, child));
            }
            ForkptyResult::Child => {
                let _ = execve::<CString, CString>(
                    &CString::new("/usr/bin/env").unwrap(),
                    &[
                        CString::new("/usr/bin/env").unwrap(),
                        CString::new("bash").unwrap(),
                        CString::new("--norc").unwrap(),
                        CString::new("--noprofile").unwrap(),
                    ],
                    &[
                        CString::new("TERM=".to_string() + ENV_TERM).unwrap(),
                        CString::new("PATH=".to_string() + ENV_PATH).unwrap(),
                        CString::new("NIXPKGS_CONFIG=/etc/nix/nixpkgs-config.nix").unwrap(),
                        CString::new("NIX_PATH=nixpkgs=flake:nixpkgs:/nix/var/nix/profiles/per-user/root/channels").unwrap(),
                    ],
                );
                return None;
            }
        },
        Err(_e) => return None,
    };
}

// returns unrecognised keys as null bytes
fn key_to_u8(key: Key, shift: bool, ctrl: bool) -> u8 {
    let mut 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,
    };

    if shift {
        base = 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,
        };
    }

    if ctrl {
        base = base & 0x1F;
    }

    return base;
}

// 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::new();
        face.outline_glyph(face.glyph_index(c).unwrap(), &mut builder)
            .unwrap();
        hm.entry(c).insert_entry(builder.0);
    }

    hm
}