extends Node2D
class_name Grid

@export var rows: int = 5
@export var cols: int = 5
@export var min_group_size: int = 3

@export var offset: float = 55.0

@onready
var grid_area: Area2D = $BoundaryArea

@onready
var grid_shape: CollisionShape2D = $BoundaryArea/BoundaryShape


var grid: Array[Array]
var groups: Array
var hovered_group: Array

var debug_label: Label

var token = preload("res://token.tscn")

func _ready():
	debug_label = $"Debug Label"

	grid_area.position = Vector2(cols * offset / 2, rows * offset / 2)
	grid_shape.shape.size = Vector2(cols * offset, rows * offset)

	for column in cols:
		grid.append([])
		for row in rows:
			grid[column].append(null)

	generate_board()

	redraw_grid()
	calculate_token_groups()

func _process(_delta: float) -> void:
	clear_highlights()

	# get mouse position for hover
	var mouse_position = self.get_local_mouse_position()
	if not pixel_within_grid(mouse_position):
		return

	var coord_under_mouse = pixel_to_grid_coord(mouse_position)
	var token_under_mouse: Token = get_token(coord_under_mouse[0], coord_under_mouse[1])

	if token_under_mouse != null:
		var group = get_group_of_token(coord_under_mouse)
		if group.size() >= min_group_size:
			highlight_group(group, true)

	# if click, determine token clicked
func pixel_within_grid(coord: Vector2) -> bool:
	return (coord.x >= 0 and coord.x < cols * offset and
					coord.y >= 0 and coord.y < rows * offset)

func pixel_to_grid_coord(coord: Vector2) -> Array[int]:
	return [coord.y / offset, coord.x / offset]

func get_token(row, col):
	return grid[col][row]

func set_token(token: Token, row, col):
	grid[col][row] = token

func generate_board():
	for row in rows:
		for column in cols:
			var token_node: Token = token.instantiate()
			add_child(token_node)
			token_node.set_type(randi_range(0,3) as Token.token_type)
			set_token(token_node, row, column)

func highlight_group(group: Array, enable: bool):

	for coord in group:
		var current_token = get_token(coord[0], coord[1])
		if current_token == null: continue
		current_token.set_highlighted(enable)

	hovered_group = group

func clear_highlights():
	for row in grid:
		for token: Token in row:
			if token != null:
				token.set_highlighted(false)

func update_grid():
#	search for empty cells and drop tokens above them down
	for column in range(cols):
		var col_array = []
		for row in range(rows-1, -1, -1):
#			create a temporary array from the column
			col_array.append(grid[row][column])

#		filter the nulls out of the array
		col_array = col_array.filter(func(token): return token != null)

#		put the filtered column back into the grid
		for row in range(rows-1, -1, -1):
			var idx = rows - row - 1
			grid[row][column] = col_array[idx] if idx < col_array.size() else null


# search for empty coluns and shift tokens horizontally to fill them
	var empty_columns = []
	for column in range(cols):
		var col_array = []
		for row in range(rows):
			col_array.append(grid[row][column])

		if col_array.all(func(token): return token == null):
			empty_columns.append(column)

	if empty_columns.size() > 0:
		var idx = 0
		var dest_column = 0
		while idx < cols:
			if idx in empty_columns:
				idx += 1
				continue

			for row in range(rows):
				grid[row][dest_column] = grid[row][idx]
			idx += 1
			dest_column += 1

	redraw_grid()
	calculate_token_groups()

func redraw_grid():
	for row in range(rows):
		for column in range(cols):
			var current_token = get_token(row, column)
			if current_token == null:
				continue

			current_token.set_debug_label(str(row) + "," + str(column))

			current_token.position = Vector2(offset*column, offset*row)

func calculate_token_groups():
	groups = []
	var visited_nodes = []
	var group_queue = []
	for row in rows:
		for col in cols:
			if [row, col] in visited_nodes or get_token(row, col) == null:
				continue

			group_queue.append([row,col])

			var new_group = []
			while not group_queue.is_empty():
				var current_coord = group_queue.pop_back()
				var current_token = get_token(current_coord[0], current_coord[1])
				new_group.append(current_coord)
				visited_nodes.append(current_coord)

				var adjacent_token_coords = [
					[current_coord[0] - 1, current_coord[1]],
					[current_coord[0], current_coord[1] + 1],
					[current_coord[0] + 1, current_coord[1]],
					[current_coord[0], current_coord[1] - 1]
				]

				var valid_coords = adjacent_token_coords.filter(
					func(coord_pair):
						return (
							coord_pair[0] >= 0 and
							coord_pair[0] < rows and
							coord_pair[1] >= 0 and
							coord_pair[1] < cols
						)
				)

				for coord in valid_coords:
					var token = get_token(coord[0],coord[1])
					if (token != null and
							coord not in visited_nodes and
							token.type == current_token.type and
							coord not in group_queue):
						group_queue.append(coord)
			groups.append(new_group)

	debug_label.text = str(groups)

func get_group_of_token(token_coord) -> Array:
	for group in groups:
		if token_coord in group:
			return group

	return []


func _on_boundary_area_input_event(viewport: Node, event: InputEvent, shape_idx: int) -> void:
	if event.is_action_pressed("select"):
		var position = self.get_local_mouse_position()
		var token_coord = pixel_to_grid_coord(position)
		var group = get_group_of_token(token_coord)
		if group.size() >= min_group_size:
			for coord in group:
				var current_token = grid[coord[0]][coord[1]] as Token
				current_token.queue_free()
				set_token(null, coord[0], coord[1])# do I actually want a null value or should there be some other placeholder?

			update_grid()