-- Radio Chapters
-- Creates chapters for streams from metadata titles.
local options = {
	-- whether to show OSD messages on title changes
	show_osd = true,
	-- String format to show on OSD on title change
	osd_string = "%s",
	-- If the first chapter should start at 00:00
	zero_first_chapter = true,
}

local last_title = nil
local first_metadata_received = false

function create_chapter(title, time)
	if not title then return end
	
	-- Create chapter
	local chapter_title = string.gsub(title, '[\n\r]', ' ')
	
	local chapter = {
		title = chapter_title,
		time = time
	}
	
	local chapter_list = mp.get_property_native("chapter-list") or {}
	table.insert(chapter_list, chapter)
	mp.set_property_native("chapter-list", chapter_list)
	
	if options.show_osd then
		mp.osd_message(string.format(options.osd_string, chapter_title))
	end
end

function handle_metadata(metadata)
	local current_title = metadata["icy-title"] or metadata["title"]
	if not current_title then return end

	local current_time = mp.get_property_number("time-pos") or 0
	
	-- First metadata recieved, create chapter.
	if not first_metadata_received then
		-- Set chapter at time 0 or current time based on option
		local initial_time = options.zero_first_chapter and 0 or current_time
		create_chapter(current_title, initial_time)
		first_metadata_received = true
		last_title = current_title
		return
	end
	
	-- Create new chapter if title changed
	if current_title ~= last_title then
		create_chapter(current_title, current_time)
		last_title = current_title
	end
end

function on_metadata_change(name, metadata)
	if name ~= "metadata" then return end
	if not metadata then return end
	
	handle_metadata(metadata)
end

-- Reset state on new file
function on_file_loaded()
	last_title = nil
	first_metadata_received = false
	mp.set_property_native("chapter-list", {})
end

mp.observe_property("metadata", "native", on_metadata_change)
mp.register_event("file-loaded", on_file_loaded)