// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.

module main

import rand
import time
import gx
import gg2 as gg
import glfw
import sokol
import sokol.sapp
import math
import freetype

const (
	block_size = 20 // pixels
	field_height = 20 // # of blocks
	field_width = 10
	tetro_size = 4
	win_width = block_size * field_width
	win_height = block_size * field_height
	timer_period = 250 // ms
	text_size = 12
	limit_thickness = 3
)

const (
	text_cfg = gx.TextCfg{
		align:gx.align_left
		size:text_size
		color:gx.rgb(0, 0, 0)
	}
	over_cfg = gx.TextCfg{
		align:gx.align_left
		size:text_size
		color:gx.white
	}
)

const (
	// Tetros' 4 possible states are encoded in binaries
	b_tetros = [
		// 0000 0
		// 0000 0
		// 0110 6
		// 0110 6
		[66, 66, 66, 66],
		// 0000 0
		// 0000 0
		// 0010 2
		// 0111 7
		[27, 131, 72, 232],
		// 0000 0
		// 0000 0
		// 0011 3
		// 0110 6
		[36, 231, 36, 231],
		// 0000 0
		// 0000 0
		// 0110 6
		// 0011 3
		[63, 132, 63, 132],
		// 0000 0
		// 0011 3
		// 0001 1
		// 0001 1
		[311, 17, 223, 74],
		// 0000 0
		// 0011 3
		// 0010 2
		// 0010 2
		[322, 71, 113, 47],
		// Special case since 15 can't be used
		// 1111
		[1111, 9, 1111, 9],
	]
	// Each tetro has its unique color
	colors = [
		gx.rgb(0, 0, 0),        // unused ?
		gx.rgb(255, 242, 0),    // yellow quad
		gx.rgb(174, 0, 255),    // purple triple
		gx.rgb(60, 255, 0),     // green short topright
		gx.rgb(255, 0, 0),      // red short topleft
		gx.rgb(255, 180, 31),   // orange long topleft
		gx.rgb(33, 66, 255),    // blue long topright
		gx.rgb(74, 198, 255),   // lightblue longest
		gx.rgb(0, 170, 170),    // unused ?
	]

	background_color = gx.white
	ui_color = gx.red
)

// TODO: type Tetro [tetro_size]struct{ x, y int }
struct Block {
	mut:
	x int
	y int
}

enum GameState {
        paused running gameover
}
struct Game {
	mut:
	// Score of the current game
	score        int
	// State of the current game
	state    GameState
	// Position of the current tetro
	pos_x        int
	pos_y        int
	// field[y][x] contains the color of the block with (x,y) coordinates
	// "-1" border is to avoid bounds checking.
	// -1 -1 -1 -1
	// -1  0  0 -1
	// -1  0  0 -1
	// -1 -1 -1 -1
	field       [][]int
	// TODO: tetro Tetro
	tetro       []Block
	// TODO: tetros_cache []Tetro
	tetros_cache []Block
	// Index of the current tetro. Refers to its color.
	tetro_idx    int
	// Index of the rotation (0-3)
	rotation_idx int
	// gg context for drawing
	gg          &gg.GG
	// ft context for font drawing
	ft          &freetype.FreeType
	font_loaded bool
}

fn frame(game &Game) {
	game.gg.begin()
	game.draw_scene()
	game.gg.end()
}

fn main() {
	mut game := &Game{}
	game.gg = gg.new_context(
		bg_color: gx.white
		width: win_width
		height: win_height
		use_ortho: true // This is needed for 2D drawing
		create_window: true
		window_title: 'V tetris'
		frame_fn: frame
		user_data: game
		//on_key_down: key_down
		event_cb: on_event
	)
		//font_path: os.resource_abs_path('assets/fonts/RobotoMono-Regular.ttf')

/*
	gconfig := gg.Config{
			width: win_width
			height: win_height
			use_ortho: true // This is needed for 2D drawing
			create_window: true
			window_title: 'V Tetris'
			//window_user_ptr: game
	}

	fconfig := gg.Config{
			width: win_width
			height: win_height
			use_ortho: true
			font_path: '../assets/fonts/RobotoMono-Regular.ttf'
			font_size: 18
			scale: 2
			window_user_ptr: 0
	}
	mut game := &Game{
		gg: gg.new_context(gconfig)
		ft: freetype.new_context(fconfig)
	}
	*/
	//game.gg.window.set_user_ptr(game) // TODO remove this when `window_user_ptr:` works
	game.init_game()
	//game.gg.window.onkeydown(key_down)
	go game.run() // Run the game loop in a new thread
	game.gg.run() // Run the render loop in the main thread
	/*
	game.font_loaded = game.ft != 0
	for {
		game.draw_scene()
		game.gg.render()
		if game.gg.window.should_close() {
			game.gg.window.destroy()
			return
		}
	}
	*/
}

fn (mut g Game) init_game() {
	g.parse_tetros()
	rand.seed(time.now().unix)
	g.generate_tetro()
	g.field = [] // TODO: g.field = [][]int
	// Generate the field, fill it with 0's, add -1's on each edge
	for _ in 0..field_height + 2 {
		mut row := [0].repeat(field_width + 2)
		row[0] = - 1
		row[field_width + 1] = - 1
		g.field << row
	}
	mut first_row := g.field[0]
	mut last_row := g.field[field_height + 1]
	for j in 0..field_width + 2 {
		first_row[j] = - 1
		last_row[j] = - 1
	}
	g.score = 0
	g.state = .running
}

fn (mut g Game) parse_tetros() {
	for b_tetros0 in b_tetros {
		for b_tetro in b_tetros0 {
			for t in parse_binary_tetro(b_tetro) {
				g.tetros_cache << t
			}
		}
	}
}

fn (mut g Game) run() {
	for {
		if g.state == .running {
			g.move_tetro()
			g.delete_completed_lines()
		}
		glfw.post_empty_event() // force window redraw
		time.sleep_ms(timer_period)
	}
}

fn (mut g Game) move_tetro() {
	// Check each block in current tetro
	for block in g.tetro {
		y := block.y + g.pos_y + 1
		x := block.x + g.pos_x
		// Reached the bottom of the screen or another block?
		// TODO: if g.field[y][x] != 0
		//if g.field[y][x] != 0 {
		row := g.field[y]
		if row[x] != 0 {
			// The new tetro has no space to drop => end of the game
			if g.pos_y < 2 {
				g.state = .gameover
				return
			}
			// Drop it and generate a new one
			g.drop_tetro()
			g.generate_tetro()
			return
		}
	}
	g.pos_y++
}

fn (mut g Game) move_right(dx int) bool {
	// Reached left/right edge or another tetro?
	for i in 0..tetro_size {
		tetro := g.tetro[i]
		y := tetro.y + g.pos_y
		x := tetro.x + g.pos_x + dx
		row := g.field[y]
		if row[x] != 0 {
			// Do not move
			return false
		}
	}
	g.pos_x += dx
	return true
}

fn (mut g Game) delete_completed_lines() {
	for y := field_height; y >= 1; y-- {
		g.delete_completed_line(y)
	}
}

fn (mut g Game) delete_completed_line(y int) {
	for x := 1; x <= field_width; x++ {
		f := g.field[y]
		if f[x] == 0 {
			return
		}
	}
	g.score += 10
	// Move everything down by 1 position
	for yy := y - 1; yy >= 1; yy-- {
		for x := 1; x <= field_width; x++ {
			mut a := g.field[yy + 1]
			b := g.field[yy]
			a[x] = b[x]
		}
	}
}

// Place a new tetro on top
fn (mut g Game) generate_tetro() {
	g.pos_y = 0
	g.pos_x = field_width / 2 - tetro_size / 2
	g.tetro_idx = rand.next(b_tetros.len)
	g.rotation_idx = 0
	g.get_tetro()
}

// Get the right tetro from cache
fn (mut g Game) get_tetro() {
	idx := g.tetro_idx * tetro_size * tetro_size + g.rotation_idx * tetro_size
	g.tetro = g.tetros_cache[idx..idx+tetro_size]
}

// TODO mut
fn (g &Game) drop_tetro() {
	for i in 0..tetro_size{
		tetro := g.tetro[i]
		x := tetro.x + g.pos_x
		y := tetro.y + g.pos_y
		// Remember the color of each block
		// TODO: g.field[y][x] = g.tetro_idx + 1
		mut row := g.field[y]
		row[x] = g.tetro_idx + 1
	}
}

fn (g &Game) draw_tetro() {
	for i in 0..tetro_size {
		tetro := g.tetro[i]
		g.draw_block(g.pos_y + tetro.y, g.pos_x + tetro.x, g.tetro_idx + 1)
	}
}

fn (g &Game) draw_block(i, j, color_idx int) {
	color := if g.state == .gameover { gx.gray } else { colors[color_idx] }
	g.gg.draw_rect((j - 1) * block_size, (i - 1) * block_size,
		block_size - 1, block_size - 1, color)
}

fn (g &Game) draw_field() {
	for i := 1; i < field_height + 1; i++ {
		for j := 1; j < field_width + 1; j++ {
			f := g.field[i]
			if f[j] > 0 {
				g.draw_block(i, j, f[j])
			}
		}
	}
}

fn (mut g Game) draw_ui() {
	if g.font_loaded {
		g.ft.draw_text(1, 3, g.score.str(), text_cfg)
		if g.state == .gameover {
			g.gg.draw_rect(0, win_height / 2 - text_size, win_width,
		 								5 * text_size, ui_color)
			g.ft.draw_text(1, win_height / 2 + 0 * text_size, 'Game Over', over_cfg)
			g.ft.draw_text(1, win_height / 2 + 2 * text_size, 'Space to restart', over_cfg)
		} else if g.state == .paused {
			g.gg.draw_rect(0, win_height / 2 - text_size, win_width,
				5 * text_size, ui_color)
			g.ft.draw_text(1, win_height / 2 + 0 * text_size, 'Game Paused', text_cfg)
			g.ft.draw_text(1, win_height / 2 + 2 * text_size, 'SPACE to resume', text_cfg)
		}
	}
	//g.gg.draw_rect(0, block_size, win_width, limit_thickness, ui_color)
}

fn (mut g Game) draw_scene() {
	g.draw_tetro()
	g.draw_field()
	g.draw_ui()
}

fn parse_binary_tetro(t_ int) []Block {
	mut t := t_
	res := [Block{}].repeat(4)
	mut cnt := 0
	horizontal := t == 9// special case for the horizontal line
	for i := 0; i <= 3; i++ {
		// Get ith digit of t
		p := int(math.pow(10, 3 - i))
		mut digit := t / p
		t %= p
		// Convert the digit to binary
		for j := 3; j >= 0; j-- {
			bin := digit % 2
			digit /= 2
			if bin == 1 || (horizontal && i == tetro_size - 1) {
				// TODO: res[cnt].x = j
				// res[cnt].y = i
				mut point := &res[cnt]
				point.x = j
				point.y = i
				cnt++
			}
		}
	}
	return res
}

fn on_event(e &sapp.Event, game mut Game) {
	if e.typ == .key_down {
		game.key_down(e.key_code)
	}
}

fn (game mut Game) key_down(key sapp.KeyCode) {
	// global keys
	match key {
		.escape {
			exit(0)
		}
		.space {
			if game.state == .running {
				game.state = .paused
			} else if game.state == .paused {
				game.state = .running
			} else if game.state == .gameover {
				game.init_game()
				game.state = .running
			}
		}
		else {}
	}

	if game.state != .running {
		return
	}
	// keys while game is running
	match key {
		.up {
			// Rotate the tetro
			old_rotation_idx := game.rotation_idx
			game.rotation_idx++
			if game.rotation_idx == tetro_size {
				game.rotation_idx = 0
			}
			game.get_tetro()
			if !game.move_right(0) {
				game.rotation_idx = old_rotation_idx
				game.get_tetro()
			}
			if game.pos_x < 0 {
				//game.pos_x = 1
			}
		}
		.left {
			game.move_right(-1)
		}
		.right {
			game.move_right(1)
		}
		.down {
			game.move_tetro() // drop faster when the player presses <down>
		}
		else { }
	}
}