local bounding_box = require("__flib__/bounding-box")

--- @param box BoundingBox
--- @return number
function bounding_box.area(box)
	return bounding_box.width(box) * bounding_box.height(box)
end

--- @alias ChestGroup
--- | { entities: LuaEntity[], bounding_box: BoundingBox, merged_chest_name: string }

--- @param event chest_merged_event
local function raise_on_chest_merged(event)
	script.raise_event(MergingChests.on_chest_merged_event_name, event)
end

--- @param entities LuaEntity[]
--- @return { [string]: LuaEntity[] }
local function group_by_name(entities)
	local groups = { }
	for _, entity in ipairs(entities) do
		local entity_name = entity.name
		if not groups[entity_name] then
			groups[entity_name] = { }
		end
		table.insert(groups[entity_name], entity)
	end
	return groups
end

--- @alias Histogram
--- | number[]
--- | { min_index: integer, max_index: integer }

--- @param histogram Histogram
--- @param is_size_allowed fun(width: integer, height: integer): boolean
--- @return integer index, integer width, integer height
local function find_largest_rectangle_under_histogram(histogram, is_size_allowed)
	local max_index = 0
	local max_width = 0
	local max_height = 0

	local stack = { }
	local top = 0
	local index = 0

	local function calculate_area_and_update()
		local peak = stack[top]
		top = top - 1

		local width = histogram[peak + histogram.min_index]
		local height = top == 0 and index or (index - stack[top] - 1)

		if width * height > max_width * max_height and is_size_allowed(width, height) then
			max_index = index + histogram.min_index - height
			max_width = width
			max_height = height
		end
	end

	while index < histogram.max_index - histogram.min_index + 1 do
		if top == 0 or histogram[stack[top] + histogram.min_index] <= histogram[index + histogram.min_index] then
			top = top + 1
			stack[top] = index
			index = index + 1
		else
			calculate_area_and_update()
		end
	end

	while top > 0 do
		calculate_area_and_update()
	end

	return max_index, max_width, max_height
end

--- @param grid Grid
--- @param is_size_allowed fun(width: integer, height: integer): boolean
--- @return BoundingBox | nil
local function find_largest_rectangle(grid, is_size_allowed)
	--- @type BoundingBox | nil
	local rectangle = nil

	--- @type Histogram
	local histogram = {
		min_index = grid.min_y,
		max_index = grid.max_y
	}
	for x = grid.min_x, grid.max_x do
		for y = grid.min_y, grid.max_y do
			if grid[x] and grid[x][y] then
				histogram[y] = (histogram[y] or 0) + 1
			else
				histogram[y] = 0
			end
		end

		local y_start, width, height = find_largest_rectangle_under_histogram(histogram, is_size_allowed)

		if width * height > (rectangle and bounding_box.area(rectangle) or 0) then
			rectangle = {
				left_top = {
					x = x - width + 1,
					y = y_start
				},
				right_bottom = {
					x = x + 1,
					y = y_start + height
				}
			}
		end
	end

	return rectangle
end

--- @param entities LuaEntity[]
--- @return ChestGroup[]
local function group_chests(entities)
	local chest_name = entities[1].name
	local chest_grid = MergingChests.entities_to_grid(entities)

	local groups = { }
	local merged = false

	repeat
		merged = false

		--- @param width integer
		--- @param height integer
		--- @return boolean
		local function is_size_allowed(width, height)
			return game.entity_prototypes[MergingChests.get_merged_chest_name(chest_name, width, height)] ~= nil
		end

		local rectangle = find_largest_rectangle(chest_grid, is_size_allowed)

		if rectangle and (bounding_box.width(rectangle) > 1 or bounding_box.height(rectangle) > 1) then
			--- @type ChestGroup
			local group = {
				entities = { },
				merged_chest_name = MergingChests.get_merged_chest_name(chest_name, bounding_box.width(rectangle), bounding_box.height(rectangle)),
				bounding_box = rectangle
			}
			for x = rectangle.left_top.x, rectangle.right_bottom.x - 1 do
				for y = rectangle.left_top.y, rectangle.right_bottom.y - 1 do
					table.insert(group.entities, chest_grid[x][y])
					chest_grid[x][y] = nil
				end
			end

			table.insert(groups, group)
			merged = true
		end
	until not merged

	return groups
end

--- @param player LuaPlayer
--- @param chest_name string
--- @param position MapPosition
--- @return LuaEntity?
local function create_merged_chest(player, chest_name, position)
	return player.surface.create_entity({
		name = chest_name,
		position = position,
		force = player.force,
		raise_built = true
	})
end

local function on_player_selected_area(event)
	if event.item and event.item == MergingChests.merge_selection_tool_name then
		local player = game.players[event.player_index]

		local entity_groups = group_by_name(event.entities)
		for _, entities in pairs(entity_groups) do
			for _, chest_group_to_merge in ipairs(group_chests(entities)) do
				if MergingChests.can_move_inventories(chest_group_to_merge.entities, chest_group_to_merge.merged_chest_name, bounding_box.area(chest_group_to_merge.bounding_box)) then
					local merged_chest = create_merged_chest(player, chest_group_to_merge.merged_chest_name, bounding_box.center(chest_group_to_merge.bounding_box))
					if merged_chest then
						MergingChests.move_inventories(chest_group_to_merge.entities, { merged_chest })
						MergingChests.move_inventory_bar(chest_group_to_merge.entities, { merged_chest })
						MergingChests.reconnect_circuits(chest_group_to_merge.entities, { merged_chest })

						raise_on_chest_merged({
							player_index = event.player_index,
							surface = event.surface,
							merged_chest = merged_chest,
							split_chests = chest_group_to_merge.entities
						})

						for _, entity in ipairs(chest_group_to_merge.entities) do
							entity.destroy({ raise_destroy = true })
						end
					end
				else
					player.create_local_flying_text({
						text = 'flying-text.'..MergingChests.prefix_with_modname('items-would-be-deleted-merge'),
						position = chest_group_to_merge.entities[1].position
					})
				end
			end
		end
	end
end

script.on_event(defines.events.on_player_selected_area, on_player_selected_area)