package snake

import k2 "../.."
import "core:math"
import "core:fmt"
import "core:time"
import "core:math/rand"
import "base:intrinsics"
import "core:log"
import "core:mem"

_ :: mem

WINDOW_SIZE :: 1000
GRID_WIDTH :: 20
CELL_SIZE :: 16
CANVAS_SIZE :: GRID_WIDTH*CELL_SIZE
TICK_RATE :: 0.13
Vec2i :: [2]int
MAX_SNAKE_LENGTH :: GRID_WIDTH*GRID_WIDTH

snake: [MAX_SNAKE_LENGTH]Vec2i
snake_length: int
tick_timer: f32 = TICK_RATE
move_direction: Vec2i
game_over: bool
food_pos: Vec2i

food_sprite: k2.Texture
head_sprite: k2.Texture
body_sprite: k2.Texture
tail_sprite: k2.Texture

food_eaten_at: time.Time
started_at: time.Time
prev_time: time.Time

place_food :: proc() {
	occupied: [GRID_WIDTH][GRID_WIDTH]bool

	for i in 0..<snake_length {
		occupied[snake[i].x][snake[i].y] = true
	}

	free_cells := make([dynamic]Vec2i, context.temp_allocator)

	for x in 0..<GRID_WIDTH {
		for y in 0..<GRID_WIDTH {
			if !occupied[x][y] {
				append(&free_cells, Vec2i {x, y})
			}
		}
	}

	if len(free_cells) > 0 {
		random_cell_index := rand.int31_max(i32(len(free_cells)))
		food_pos = free_cells[random_cell_index]
	}

}

restart :: proc() {
	start_head_pos := Vec2i { GRID_WIDTH / 2, GRID_WIDTH / 2 }
	snake[0] = start_head_pos
	snake[1] = start_head_pos - {0, 1}
	snake[2] = start_head_pos - {0, 2}
	snake_length = 3
	move_direction = {0, 1}
	game_over = false
	place_food()
}

main :: proc() {
	context.logger = log.create_console_logger()
	init()
	run := true

	for run {
		run = step()
	}

	shutdown()
}

font: k2.Font_Handle

init :: proc() {
	k2.init(WINDOW_SIZE, WINDOW_SIZE, "Snake")

	prev_time = time.now()

	restart()

	food_sprite = k2.load_texture_from_bytes(#load("food.png"))
	head_sprite = k2.load_texture_from_bytes(#load("head.png"))
	body_sprite = k2.load_texture_from_bytes(#load("body.png"))
	tail_sprite = k2.load_texture_from_bytes(#load("tail.png"))

	food_eaten_at = time.now()
	started_at = time.now()
}

step :: proc() -> bool {
	k2.new_frame()
	k2.process_events()

	if k2.key_is_held(.Up) || k2.gamepad_button_is_held(0, .Left_Face_Up) {
		move_direction = {0, -1}
	}

	if k2.key_is_held(.Down) || k2.gamepad_button_is_held(0, .Left_Face_Down) {
		move_direction = {0, 1}
	}

	if k2.key_is_held(.Left) || k2.gamepad_button_is_held(0, .Left_Face_Left) {
		move_direction = {-1, 0}
	}

	if k2.key_is_held(.Right) || k2.gamepad_button_is_held(0, .Left_Face_Right) {
		move_direction = {1, 0}
	}

	dt := k2.get_frame_time()

	if game_over {
		if k2.key_went_down(.Enter) {
			restart()
		}
	} else {
		tick_timer -= dt
	}

	if tick_timer <= 0 {
		next_part_pos := snake[0]
		snake[0] += move_direction
		head_pos := snake[0]

		if head_pos.x < 0 || head_pos.y < 0 || head_pos.x >= GRID_WIDTH || head_pos.y >= GRID_WIDTH {
			game_over = true
		}

		for i in 1..<snake_length {
			cur_pos := snake[i]

			if cur_pos == head_pos {
				game_over = true
			}

			snake[i] = next_part_pos
			next_part_pos = cur_pos
		}

		if head_pos == food_pos {
			snake_length += 1
			snake[snake_length - 1] = next_part_pos
			place_food()
			food_eaten_at = time.now()
		}

		tick_timer = TICK_RATE + tick_timer
	}

	k2.clear({76, 53, 83, 255})

	camera := k2.Camera {
		zoom = f32(WINDOW_SIZE) / CANVAS_SIZE,
	}
	
	k2.set_camera(camera)
	food_sprite.width = CELL_SIZE
	food_sprite.height = CELL_SIZE

	k2.draw_texture(food_sprite, {f32(food_pos.x), f32(food_pos.y)}*CELL_SIZE)

	for i in 0..<snake_length {
		part_sprite := body_sprite
		dir: Vec2i

		if i == 0 {
			part_sprite = head_sprite
			dir = snake[i] - snake[i + 1]
		} else if i == snake_length - 1 {
			part_sprite = tail_sprite
			dir = snake[i - 1] - snake[i]
		} else {
			dir = snake[i - 1] - snake[i]
		}

		rot := math.atan2(f32(dir.y), f32(dir.x)) * math.DEG_PER_RAD

		source := k2.Rect {
			0, 0,
			f32(part_sprite.width), f32(part_sprite.height),
		}

		dest := k2.Rect {
			f32(snake[i].x)*CELL_SIZE + 0.5*CELL_SIZE,
			f32(snake[i].y)*CELL_SIZE + 0.5*CELL_SIZE,
			CELL_SIZE,
			CELL_SIZE,
		}

		k2.draw_texture_ex(part_sprite, source, dest, {CELL_SIZE, CELL_SIZE}*0.5, rot)
	}

	if game_over {
		k2.draw_text("Game Over!", {4, 4}, 25, k2.RL_RED)
		k2.draw_text("Press Enter to play again", {4, 30}, 15, k2.BLACK)
	}

	score := snake_length - 3
	score_str := fmt.tprintf("Score: %v", score)
	k2.draw_text(score_str, {4, CANVAS_SIZE - 14}, 10, k2.RL_GRAY)
	k2.present()

	free_all(context.temp_allocator)
	return !k2.shutdown_wanted()
}

shutdown :: proc() {
	k2.destroy_texture(head_sprite)
	k2.destroy_texture(food_sprite)
	k2.destroy_texture(body_sprite)
	k2.destroy_texture(tail_sprite)

	k2.shutdown()
}