extern crate termios;

use rand::Rng;
use std::io::Read;

const FIELD_COLS: usize = 10;
const FIELD_ROWS_VISIBLE: usize = 20;
const FIELD_ROWS: usize = FIELD_ROWS_VISIBLE + 20;
const FIELD_SIZE: usize = FIELD_COLS * FIELD_ROWS;
const FIGURE_SIZE_COLS: usize = 4;
const FIGURE_SIZE_ROWS: usize = 4;
const FIGURE_SIZE: usize = FIGURE_SIZE_COLS*FIGURE_SIZE_ROWS;
const CELLS_I: [i8; FIGURE_SIZE] = [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0];
const CELLS_L2:[i8; FIGURE_SIZE] = [0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0];
const CELLS_L: [i8; FIGURE_SIZE] = [0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0];
const CELLS_B: [i8; FIGURE_SIZE] = [0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0];
const CELLS_S: [i8; FIGURE_SIZE] = [0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0];
const CELLS_T: [i8; FIGURE_SIZE] = [0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0];
const CELLS_Z: [i8; FIGURE_SIZE] = [0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0];

#[derive(Clone)]
#[derive(Debug)]
enum FigureKind {
    I,
    L2,
    L,
    T,
    B,
    S,
    Z,
}

#[derive(Clone)]
struct Figure {
    kind: FigureKind,
    cells: [i8; FIGURE_SIZE],
}

impl Figure {
    fn kind_random() -> Self {
        return match rand::thread_rng().gen_range(0..7) {
            0 => Self::kind_i(),
            1 => Self::kind_l2(),
            2 => Self::kind_l(),
            3 => Self::kind_b(),
            4 => Self::kind_s(),
            5 => Self::kind_t(),
            6 => Self::kind_z(),
            _ => unreachable!(),
        };
    }
    const fn kind_i() -> Self { Self{ cells: CELLS_I, kind: FigureKind::I } }
    const fn kind_l2() -> Self { Self{ cells: CELLS_L2, kind: FigureKind::L2 } }
    const fn kind_l() -> Self { Self{ cells: CELLS_L, kind: FigureKind::L } }
    const fn kind_b() -> Self { Self{ cells: CELLS_B, kind: FigureKind::B } }
    const fn kind_s() -> Self { Self{ cells: CELLS_S, kind: FigureKind::S } }
    const fn kind_t() -> Self { Self{ cells: CELLS_T, kind: FigureKind::T } }
    const fn kind_z() -> Self { Self{ cells: CELLS_Z, kind: FigureKind::Z } }
    fn rotate_cw_4x4(&mut self) {
        let mut tmp: [i8; 4 * 4] = Default::default();
        for y in 0..4 {
            for x in 0..4 {
                tmp[y + (3 - x) * 4] = self.cells[x + y * 4];
            }
        }
        self.cells = tmp;
    }
    fn rotate_cw_3x3(&mut self) {
        let mut tmp: [i8; 3 * 3] = Default::default();
        for y in 0..3 {
            for x in 0..3 {
                tmp[y + (2 - x) * 3] = self.cells[x + y * 4];
            }
        }
        for y in 0..3 {
            for x in 0..3 {
                self.cells[x + y * 4] = tmp[x + y * 3];
            }
        }
    }
    fn rotate(&mut self) {
        match self.kind {
            FigureKind::I => self.rotate_cw_4x4(),
            FigureKind::L2 => self.rotate_cw_3x3(),
            FigureKind::L => self.rotate_cw_3x3(),
            FigureKind::B => {},
            FigureKind::S => self.rotate_cw_3x3(),
            FigureKind::T => self.rotate_cw_3x3(),
            FigureKind::Z => self.rotate_cw_3x3(),
        }
    }
}

#[derive(Clone)]
struct Field {
    cells: [i8; FIELD_SIZE],
}

impl Default for Field {
    #[inline]
    fn default() -> Self {
        Self { cells: [0; FIELD_SIZE] }
    }
}

impl Field {
    fn render(&mut self, figure: &Figure, x: isize, y: isize) {
        for i in 0..FIGURE_SIZE {
            let f_x = (i % FIGURE_SIZE_COLS) as isize + x;
            let f_y = (i / FIGURE_SIZE_ROWS) as isize + y;
            if f_x < 0 {
                continue;
            } else if f_x >= FIELD_COLS as isize {
                continue;
            } else if f_y < 0 {
                continue;
            } else if f_y >= FIELD_ROWS as isize {
                continue;
            }
            if figure.cells[i] != 0 {
                self.cells[f_x as usize + f_y as usize * FIELD_COLS] = figure.cells[i];
            }
        }
    }
    fn has_collision(&self, figure: &Figure, x: isize, y: isize) -> bool {
        for i in 0..FIGURE_SIZE {
            let f_x = (i % FIGURE_SIZE_COLS) as isize + x;
            let f_y = (i / FIGURE_SIZE_ROWS) as isize + y;
            if figure.cells[i] != 0 {
                if f_x < 0 {
                    return true;
                } else if f_x >= FIELD_COLS as isize {
                    return true;
                } else if f_y < 0 {
                    return true;
                } else if f_y >= FIELD_ROWS as isize {
                    return true;
                } else if self.cells[f_x as usize + f_y as usize * FIELD_COLS] != 0 {
                    return true;
                }
            }
        }
        false
    }
}

struct Game {
    field: Field,
    figure: Figure,
    x: isize,
    y: isize,
}

impl Default for Game {
    #[inline]
    fn default() -> Self {
        Self{ field: Field::default(), figure: Figure::kind_random(), x: 0, y: 0 }
    }
}

impl Game {
    fn place(&mut self) {
        self.field.render(&self.figure, self.x, self.y);
        self.figure = Figure::kind_random();
        self.x = 0;
        self.y = 0;
    }
    fn step(&mut self, fd: &mut std::io::Stdin) -> Option<()> {
        let mut r: [u8;1]=[0];
        fd.read(&mut r[..]).unwrap();
        match r[0] as char {
            'q' => return None,
            ' ' => {
                if !self.field.has_collision(&self.figure, self.x, self.y) {
                    self.place()
                }
            },
            'h' => {
                if self.field.has_collision(&self.figure, self.x, self.y) {
                    self.x -= 1
                } else if !self.field.has_collision(&self.figure, self.x - 1, self.y) {
                    self.x -= 1
                }
            }
            'j' => {
                if self.field.has_collision(&self.figure, self.x, self.y) {
                    self.y -= 1
                } else if !self.field.has_collision(&self.figure, self.x, self.y - 1) {
                    self.y -= 1
                }
            }
            'k' => {
                if self.field.has_collision(&self.figure, self.x, self.y) {
                    self.y += 1
                } else if !self.field.has_collision(&self.figure, self.x, self.y + 1) {
                    self.y += 1
                }
            }
            'l' => {
                if self.field.has_collision(&self.figure, self.x, self.y) {
                    self.x += 1
                } else if !self.field.has_collision(&self.figure, self.x + 1, self.y) {
                    self.x += 1
                }
            }
            ';' => {
                let mut figure = self.figure.clone();
                figure.rotate();
                if !self.field.has_collision(&figure, self.x, self.y) {
                    self.figure.rotate()
                }
            }
            _ => {},
        }
        Some(())
    }
}

fn print_field(field: &Field) {
    cursor_to_home();
    clear_line();
    for y in 0..FIELD_ROWS_VISIBLE {
        for x in 0..FIELD_COLS {
            let c = field.cells[(FIELD_ROWS_VISIBLE - 1 - y) * FIELD_COLS + x];
            if c == 0 {
                print!("██");
            } else {
                print!("  ");
            }
        }
        print!("\r\x1b[1B");
    }
}

fn display_game(game: &Game) {
    cursor_to_home();
    let mut field = game.field.clone();
    field.render(&game.figure, game.x, game.y);
    print_field(&field);
    if game.field.has_collision(&game.figure, game.x, game.y) {
        println!("Collision!");
    } else {
        clear_line();
    }
}

fn clear_screen() {
    print!("\x1B[2J");
}

fn cursor_to_home() {
    print!("\x1B[H");
}

fn clear_line() {
    println!("\x1B[2K");
}

fn main() {
    let termios_state_initial = termios::Termios::from_fd(0).unwrap();
    let mut termios_state = termios_state_initial.clone();
    let c_lflag = termios_state.c_lflag;
    termios_state.c_lflag &= !(termios::ICANON | termios::ECHO);
    termios::tcsetattr(0, termios::TCSADRAIN, &termios_state).unwrap();
    termios_state.c_lflag = c_lflag;
    clear_screen();
    let mut game = Game::default();
    display_game(&game);
    let mut stdin = std::io::stdin();
    loop {
        if let None = game.step(&mut stdin) {
            break;
        }
        display_game(&game);
    }
    termios::tcsetattr(0, termios::TCSADRAIN, &termios_state_initial).unwrap();
}