extern crate termios;

use nonblock::NonBlockingReader;
use rand::seq::SliceRandom;
use std::io::Write;

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: [u8; FIGURE_SIZE] = [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0];
const CELLS_L2: [u8; FIGURE_SIZE] = [0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0];
const CELLS_L: [u8; FIGURE_SIZE] = [0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0];
const CELLS_B: [u8; FIGURE_SIZE] = [0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0];
const CELLS_S: [u8; FIGURE_SIZE] = [0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0];
const CELLS_T: [u8; FIGURE_SIZE] = [0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0];
const CELLS_Z: [u8; FIGURE_SIZE] = [0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0];
const NEXT_COUNT: usize = 4;
const DISPLAY_NEXT_OFFSET_DOWN: usize = 4;
const DISPLAY_HOLD_OFFSET_DOWN: usize = 4;
const GHOST_MASK: u8 = 8;

enum StepResult {
    StateChanged,
    Quit,
}

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

struct Timeout {
    beginning: nix::sys::time::TimeSpec,
    duration: std::time::Duration,
}

impl Default for Timeout {
    #[inline]
    fn default() -> Self {
        Self {
            beginning: nix::sys::time::TimeSpec::new(0, 0),
            duration: std::time::Duration::default(),
        }
    }
}

impl Timeout {
    fn from_duration(d: std::time::Duration) -> Self {
        Timeout {
            beginning: nix::time::clock_gettime(nix::time::ClockId::CLOCK_MONOTONIC).unwrap(),
            duration: d,
        }
    }
    fn is_elapsed(&self) -> bool {
        std::time::Duration::from(self.beginning) + self.duration
            <= std::time::Duration::from(
                nix::time::clock_gettime(nix::time::ClockId::CLOCK_MONOTONIC).unwrap(),
            )
    }
}

#[derive(Clone)]
struct Figure {
    kind: FigureKind,
    cells: [u8; FIGURE_SIZE],
}

impl Figure {
    fn from_kind(kind: FigureKind) -> Self {
        match kind {
            FigureKind::I => Self {
                cells: CELLS_I,
                kind,
            },
            FigureKind::J => Self {
                cells: CELLS_L2,
                kind,
            },
            FigureKind::L => Self {
                cells: CELLS_L,
                kind,
            },
            FigureKind::O => Self {
                cells: CELLS_B,
                kind,
            },
            FigureKind::S => Self {
                cells: CELLS_S,
                kind,
            },
            FigureKind::T => Self {
                cells: CELLS_T,
                kind,
            },
            FigureKind::Z => Self {
                cells: CELLS_Z,
                kind,
            },
        }
    }
    fn rotate_cw_4x4(&mut self) {
        let mut tmp: [u8; 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: [u8; 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::J => self.rotate_cw_3x3(),
            FigureKind::L => self.rotate_cw_3x3(),
            FigureKind::O => {}
            FigureKind::S => self.rotate_cw_3x3(),
            FigureKind::T => self.rotate_cw_3x3(),
            FigureKind::Z => self.rotate_cw_3x3(),
        }
    }
}

trait Cell {
    fn is_ghost(&self) -> bool;
    fn set_ghost(&mut self, ghost: bool);
    fn color(&self) -> Self;
}

impl Cell for u8 {
    fn is_ghost(&self) -> bool {
        *self & GHOST_MASK != 0
    }
    fn set_ghost(&mut self, ghost: bool) {
        if ghost {
            *self |= GHOST_MASK;
        } else {
            *self &= !GHOST_MASK;
        }
    }
    fn color(&self) -> Self {
        self & !GHOST_MASK
    }
}

#[derive(Clone)]
struct Field {
    cells: [u8; 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 || f_x >= FIELD_COLS as isize || f_y < 0 || f_y >= FIELD_ROWS as isize {
                continue;
            }
            let color = figure.cells[i].color();
            let current = f_x as usize + f_y as usize * FIELD_COLS;
            if color != 0 && (self.cells[current].is_ghost() || self.cells[current] == 0) {
                self.cells[current] = 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;
            let color = figure.cells[i].color();
            if color != 0 {
                if f_x < 0 || f_x >= FIELD_COLS as isize || f_y < 0 || f_y >= FIELD_ROWS as isize {
                    return true;
                }
                let fcolor = self.cells[f_x as usize + f_y as usize * FIELD_COLS].color();
                if fcolor != 0 {
                    return true;
                }
            }
        }
        false
    }
    fn is_line_complete(&self, line: usize) -> bool {
        assert!(line < FIELD_ROWS);
        self.cells[FIELD_COLS * line..][..FIELD_COLS]
            .iter()
            .fold(1, |a, e| a & e)
            != 0
    }
    fn kill_line(&mut self, line: usize) {
        for row in line..FIELD_ROWS - 1 {
            for col in 0..FIELD_COLS {
                self.cells[col + row * FIELD_COLS] = self.cells[col + (row + 1) * FIELD_COLS];
            }
        }
        for col in 0..FIELD_COLS {
            self.cells[col + (FIELD_ROWS - 1) * FIELD_COLS] = 0;
        }
    }
}

struct Bag {
    index: u8,
    pieces: [u8; 7],
}

impl Bag {
    fn next(&mut self) -> FigureKind {
        if self.index >= 7 {
            self.index = 0;
            self.pieces.shuffle(&mut rand::thread_rng());
        }
        let i = self.index;
        self.index += 1;
        match self.pieces[i as usize] {
            1 => FigureKind::I,
            2 => FigureKind::J,
            3 => FigureKind::L,
            5 => FigureKind::O,
            6 => FigureKind::S,
            4 => FigureKind::T,
            7 => FigureKind::Z,
            _ => unreachable!(),
        }
    }
}

impl Default for Bag {
    #[inline]
    fn default() -> Self {
        let mut pieces: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
        pieces.shuffle(&mut rand::thread_rng());
        Self { index: 0, pieces }
    }
}

enum MenuAction {
    Run,
    Quit,
}

enum MenuContent {
    Action(MenuAction),
}

struct Menu {
    name: &'static str,
    content: MenuContent,
}

enum GameState {
    Menu,
    InGame,
}

struct Game {
    state: GameState,
    menu: Vec<Menu>,
    menu_selected: usize,
    field: Field,
    figure: Figure,
    x: isize,
    y: isize,
    fall_timeout: Timeout,
    place_timeout: Option<Timeout>,
    bag: Bag,
    figure_next: [Figure; NEXT_COUNT],
    figure_on_hold: Figure,
}

impl Default for Game {
    #[inline]
    fn default() -> Self {
        let menu = vec![
            Menu{
                name: "Play",
                content: MenuContent::Action(MenuAction::Run),
            },
            Menu{
                name: "Quit",
                content: MenuContent::Action(MenuAction::Quit),
            },
        ];
        let mut bag = Bag::default();
        let figure_on_hold = Figure::from_kind(bag.next());
        let figure = Figure::from_kind(bag.next());
        let figure_next = [
            Figure::from_kind(bag.next()),
            Figure::from_kind(bag.next()),
            Figure::from_kind(bag.next()),
            Figure::from_kind(bag.next()),
        ];
        Self {
            state: GameState::InGame,
            menu,
            menu_selected: 0,
            field: Field::default(),
            figure,
            x: 3,
            y: 17,
            fall_timeout: Timeout::from_duration(std::time::Duration::from_millis(500)),
            place_timeout: None,
            bag,
            figure_next,
            figure_on_hold,
        }
    }
}

impl Game {
    fn start_game(&mut self) {
        self.bag = Bag::default();
        self.figure_on_hold = Figure::from_kind(self.bag.next());
        self.figure = Figure::from_kind(self.bag.next());
        self.figure_next = [
            Figure::from_kind(self.bag.next()),
            Figure::from_kind(self.bag.next()),
            Figure::from_kind(self.bag.next()),
            Figure::from_kind(self.bag.next()),
        ];
        self.field = Field::default();
        self.state = GameState::InGame;
        (self.x, self.y) = (3, 17);
        self.fall_timeout = Timeout::from_duration(std::time::Duration::from_millis(500));
        self.place_timeout = None;
    }

    fn place_figure(&mut self) {
        self.field.render(&self.figure, self.x, self.y);
        self.figure = self.figure_next[0].clone();
        for i in 0..NEXT_COUNT - 1 {
            self.figure_next[i] = self.figure_next[i + 1].clone();
        }
        self.figure_next[NEXT_COUNT - 1] = Figure::from_kind(self.bag.next());
        (self.x, self.y) = (3, 17);
        for line in 0..FIELD_ROWS - 1 {
            while self.field.is_line_complete(line) {
                self.field.kill_line(line);
            }
        }
        self.stop_place_timeout();
    }

    fn hold_figure(&mut self) {
        (self.figure_on_hold, self.figure) = (
            Figure::from_kind(self.figure.kind.clone()),
            self.figure_on_hold.clone(),
        );
        (self.x, self.y) = (3, 17);
    }

    fn reset_fall_timeout(&mut self) {
        self.fall_timeout = Timeout::from_duration(std::time::Duration::from_millis(500));
    }

    fn start_place_timeout(&mut self) {
        self.place_timeout = Some(Timeout::from_duration(std::time::Duration::from_millis(
            500,
        )));
    }

    fn stop_place_timeout(&mut self) {
        self.place_timeout = None
    }

    fn reset_place_timeout(&mut self) {
        if self.place_timeout.is_some() {
            self.start_place_timeout();
        }
    }

    fn handle_input_ingame(&mut self, c: char) -> Option<StepResult> {
        match c {
            'q' => return Some(StepResult::Quit),
            ' ' => {
                while !self.field.has_collision(&self.figure, self.x, self.y - 1) {
                    self.y -= 1;
                }
                self.place_figure();
                self.stop_place_timeout();
            }
            'j' => {
                if !self.field.has_collision(&self.figure, self.x - 1, self.y) {
                    self.x -= 1;
                }
            }
            'k' => {
                if !self.field.has_collision(&self.figure, self.x, self.y - 1) {
                    self.y -= 1;
                    self.reset_fall_timeout();
                } else {
                    self.start_place_timeout();
                }
            }
            ';' | 'i' => {
                let mut figure = self.figure.clone();
                figure.rotate();
                if !self.field.has_collision(&figure, self.x, self.y) {
                    self.figure.rotate()
                }
            }
            'l' => {
                if !self.field.has_collision(&self.figure, self.x + 1, self.y) {
                    self.x += 1;
                }
            }
            'h' => {
                self.hold_figure();
                self.reset_fall_timeout();
                self.stop_place_timeout();
            }
            _ => return None,
        }
        self.reset_place_timeout();
        Some(StepResult::StateChanged)
    }

    fn advance_figure(&mut self) {
        if self.field.has_collision(&self.figure, self.x, self.y - 1) {
            self.place_figure();
        } else {
            self.y -= 1;
            if self.field.has_collision(&self.figure, self.x, self.y - 1) {
                self.start_place_timeout();
            } else {
                self.stop_place_timeout();
            }
        }
        self.reset_fall_timeout();
    }

    fn step_game(&mut self, c_optional: Option<char>) -> Option<StepResult> {
        let handle_input_result = if let Some(c) = c_optional {
            self.handle_input_ingame(c)
        } else {
            None
        };
        let advance_figure_result = if let Some(t) = &self.place_timeout {
            if t.is_elapsed() {
                self.advance_figure();
                Some(StepResult::StateChanged)
            } else {
                None
            }
        } else if self.fall_timeout.is_elapsed() {
            self.advance_figure();
            Some(StepResult::StateChanged)
        } else {
            None
        };
        if handle_input_result.is_none() {
            advance_figure_result
        } else {
            handle_input_result
        }
    }

    fn handle_input_menu(&mut self, c: char) -> Option<StepResult> {
        match c {
            'q' => return Some(StepResult::Quit),
            'k' => {
                if self.menu_selected + 1 < self.menu.len() {
                    self.menu_selected += 1;
                    Some(StepResult::StateChanged)
                } else {
                    None
                }
            }
            'i' => {
                if self.menu_selected > 0 {
                    self.menu_selected -= 1;
                    Some(StepResult::StateChanged)
                } else {
                    None
                }
            }
            'l' | ' ' | '\n' => {
                match &self.menu[self.menu_selected].content {
                    MenuContent::Action(action) => match action {
                        MenuAction::Run => {
                            self.start_game();
                            Some(StepResult::StateChanged)
                        },
                        MenuAction::Quit => Some(StepResult::Quit),
                    },
                }
            }
            _ => None,
        }
    }

    fn step_menu(&mut self, c_optional: Option<char>) -> Option<StepResult> {
        if let Some(c) = c_optional {
            self.handle_input_menu(c)
        } else {
            None
        }
    }

    fn step(&mut self, c_optional: Option<char>) -> Option<StepResult> {
        match self.state {
            GameState::Menu => self.step_menu(c_optional),
            GameState::InGame => self.step_game(c_optional),
        }
    }
}

struct Tui {
    state: termios::Termios,
}

impl Tui {
    fn display_hold(&self, figure: &Figure, y_global: usize) {
        let offset = DISPLAY_HOLD_OFFSET_DOWN;
        let at_figure = y_global >= (1 + offset) && y_global < FIGURE_SIZE_ROWS + (1 + offset);
        if y_global == offset {
            print!("   Hold:  ");
        } else if at_figure {
            print!(" ");
            let y = FIGURE_SIZE_ROWS - 1 - (y_global - 1 - offset);
            for x in 0..FIGURE_SIZE_COLS {
                let c = figure.cells[y * FIGURE_SIZE_COLS + x];
                if c == 0 {
                    print!("  ");
                } else {
                    print!("██");
                }
            }
            print!(" ");
        } else {
            print!("          ");
        }
    }

    fn display_next(&self, figures: &[Figure; NEXT_COUNT], y_global: usize) {
        let offset = DISPLAY_NEXT_OFFSET_DOWN;
        if y_global == offset {
            return print!("   Next:  ");
        }
        for (i, figure) in figures.iter().enumerate().take(NEXT_COUNT) {
            let at_figure = y_global >= (1 + offset + FIGURE_SIZE_ROWS * i)
                && y_global < (1 + offset + FIGURE_SIZE_ROWS * (i + 1));
            if at_figure {
                print!(" ");
                let y = FIGURE_SIZE_ROWS - 1 - (y_global - 1 - offset - FIGURE_SIZE_ROWS * i);
                for x in 0..FIGURE_SIZE_COLS {
                    let c = figure.cells[y * FIGURE_SIZE_COLS + x];
                    if c == 0 {
                        print!("  ");
                    } else {
                        print!("██");
                    }
                }
                break;
            }
        }
    }

    fn display_field(&self, field: &Field, y: usize) {
        print!("|");
        for x in 0..FIELD_COLS {
            let cell = field.cells[(FIELD_ROWS_VISIBLE - 1 - y) * FIELD_COLS + x];
            if cell.color() == 0 {
                print!("  ");
            } else if cell.is_ghost() {
                print!("░░");
            } else {
                print!("██");
            }
        }
        print!("|");
    }

    fn display_game_ingame(&self, game: &Game) {
        self.cursor_to_home();
        let mut field = game.field.clone();
        let mut ghost = game.figure.clone();
        for i in 0..FIGURE_SIZE {
            ghost.cells[i].set_ghost(true);
        }
        let mut y_ghost = game.y;
        while !field.has_collision(&ghost, game.x, y_ghost) {
            y_ghost -= 1;
        }
        y_ghost += 1;
        field.render(&ghost, game.x, y_ghost);
        field.render(&game.figure, game.x, game.y);
        for y in 0..FIELD_ROWS_VISIBLE {
            self.display_hold(&game.figure_on_hold, y);
            self.display_field(&field, y);
            self.display_next(&game.figure_next, y);
            print!("\r\x1b[1B");
        }
        if game.field.has_collision(&game.figure, game.x, game.y) {
            println!("Collision!");
        } else {
            self.clear_line();
        }
    }

    fn display_game_menu(&self, game: &Game) {
        self.cursor_to_home();
        for y in 0..FIELD_ROWS_VISIBLE {
            print!("          |");
            if y == 10 {
                if game.menu_selected == 0 {
                    print!("\x1b[7m");
                }
                print!("{:^20}\x1b[0m", game.menu[0].name);
            } else if y == 11 {
                if game.menu_selected == 1 {
                    print!("\x1b[7m");
                }
                print!("{:^20}\x1b[0m", game.menu[1].name);
            } else {
                print!("                    ");
            }
            print!("|");
            print!("\r\x1b[1B");
        }
    }

    fn display_game(&self, game: &Game) {
        match game.state {
            GameState::Menu => self.display_game_menu(game),
            GameState::InGame => self.display_game_ingame(game),
        }
        std::io::stdout().flush().unwrap();
    }

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

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

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

    fn hide_cursor(&self) {
        println!("\x1B[?25l");
    }

    fn show_cursor(&self) {
        println!("\x1B[?25h");
    }
}

impl Default for Tui {
    fn default() -> Self {
        let termios_state_initial = termios::Termios::from_fd(0).unwrap();
        let mut termios_state = termios_state_initial;
        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;
        let tui = Self {
            state: termios_state_initial,
        };
        tui.clear_screen();
        tui.hide_cursor();
        tui
    }
}

impl Drop for Tui {
    fn drop(&mut self) {
        self.show_cursor();
        self.cursor_to_home();
        termios::tcsetattr(0, termios::TCSADRAIN, &self.state).unwrap();
    }
}

fn main() {
    let tui = Tui::default();
    let mut game = Game::default();
    if std::env::args().len() > 1 {
        game.state = GameState::Menu;
    }
    tui.display_game(&game);
    let mut noblock_stdin = NonBlockingReader::from_fd(std::io::stdin()).unwrap();
    'outer: while !noblock_stdin.is_eof() {
        let mut buf = String::new();
        noblock_stdin.read_available_to_string(&mut buf).unwrap();
        let mut changed = false;
        for c in buf.bytes() {
            if let Some(result) = game.step(Some(c as char)) {
                match result {
                    StepResult::StateChanged => changed = true,
                    StepResult::Quit => break 'outer,
                }
            }
        }
        if let Some(result) = game.step(None) {
            match result {
                StepResult::StateChanged => changed = true,
                StepResult::Quit => break 'outer,
            }
        }
        if changed {
            tui.display_game(&game);
        }
        std::thread::sleep(std::time::Duration::from_millis(1));
    }
}