local utils = require('mp.utils')

local script_dir = mp.get_script_directory()
local stream_prefix = mp.get_opt('iptv_menu.stream_prefix')

-- font size is in units of osd height, which is scaled to 720
local font_size = 20
local osd = mp.create_osd_overlay('ass-events')
local osd_lines = math.floor((720 / font_size) + 0.5) - 1
local osd_padding = math.floor((720 - (osd_lines * font_size)) / 2)
local key_bindings = {}

local categories = {}
local streams = {}

local depth = 0
local menus = {}
local menu_top = {}
local menu_pos = {}

local function load_json_file(path)
	local f = io.open(script_dir .. '/' .. path, 'r')
	local data = f:read('*all')
	f:close()
	return utils.parse_json(data)
end

local function load_data()
	categories = load_json_file('categories.json')
	for _, v in ipairs(categories) do
		v.type = 'category'
	end

	streams = load_json_file('streams.json')
	for _, v in ipairs(streams) do
		v.type = 'stream'
	end
end

local function osd_menu_lines()
	if depth > 1 then
		return osd_lines - depth
	else
		return osd_lines
	end
end

local function update_osd()
	local out = {}

	if depth > 1 then
		for i = 1, depth - 1 do
			out[#out+1] = '{\\c&H999999&} » [' ..
				menus[i][menu_pos[i]].category_name .. ']{\\c}'
		end
		out[#out+1] = ' ' -- space character for correct line height
	end

	for i = menu_top[depth], math.min(
			menu_top[depth] + osd_menu_lines() - 1,
			#menus[depth]) do
		local opt = menus[depth][i]
		local str

		if opt.type == 'category' then
			str = '[' .. opt.category_name .. ']'
		else
			str = opt.name
		end

		if i == menu_pos[depth] then
			str = '{\\c&HFF00&}* ' .. str .. '{\\c}'
		elseif opt.type == 'category' then
			str = '{\\c&H99DDFF&}' .. str .. '{\\c}'
		end

		out[#out+1] = str
	end

	-- \q2 disables line wrapping
	osd.data = '{\\q2}{\\fs' .. font_size .. '}{\\pos(' .. osd_padding ..
		',' .. osd_padding .. '}' .. table.concat(out, '\\N')
	osd:update()
end

local function advance_cursor(n, opts)
	pos = math.max(1, math.min(menu_pos[depth] + n, #menus[depth]))
	top = menu_top[depth]
	if opts and opts.advance_page then
		top = top + n
	end

	-- move page to keep selected option visible
	if pos < top then
		top = pos
	elseif pos > top + osd_menu_lines() - 1 then
		top = pos - osd_menu_lines() + 1
	end

	top = math.max(1, math.min(top, #menus[depth] - osd_menu_lines() + 1))

	menu_pos[depth] = pos
	menu_top[depth] = top
	update_osd()
end

local function next_option()
	advance_cursor(1)
end

local function prev_option()
	advance_cursor(-1)
end

local function next_page()
	advance_cursor(osd_menu_lines(), {advance_page=true})
end

local function prev_page()
	advance_cursor(-osd_menu_lines(), {advance_page=true})
end

local function first_option()
	advance_cursor(-math.huge)
end

local function last_option()
	advance_cursor(math.huge)
end

local function add_category_menu(category_id)
	local menu = {}
	for _, v in ipairs(categories) do
		if tostring(v.parent_id) == category_id then
			menu[#menu+1] = v
		end
	end
	for _, v in ipairs(streams) do
		if v.category_id == category_id then
			menu[#menu+1] = v
		end
	end

	depth = depth + 1
	menus[depth] = menu
	menu_top[depth] = 1
	menu_pos[depth] = 1
	update_osd()
end

local function play_stream(stream_id)
	local url = stream_prefix .. stream_id
	mp.commandv('loadfile', url)
end

local function select_option()
	local opt = menus[depth][menu_pos[depth]]

	if opt.type == 'category' then
		add_category_menu(opt.category_id)
	else
		play_stream(opt.stream_id)
	end
end

local function prev_menu()
	if depth > 1 then
		depth = depth - 1
		update_osd()
	end
end

local function bind_key(key, name, func, opts)
	key_bindings[#key_bindings+1] = name
	mp.add_forced_key_binding(key, name, func, opts)
end

local function unbind_keys()
	for _, name in ipairs(key_bindings) do
		mp.remove_key_binding(name)
	end
	key_bindings = {}
end

local function bind_keys()
	local repeatable = {repeatable=true}
	bind_key('DOWN', 'next-option', next_option, repeatable)
	bind_key('UP', 'prev-option', prev_option, repeatable)
	bind_key('PGDWN', 'next-page', next_page, repeatable)
	bind_key('PGUP', 'prev-page', prev_page, repeatable)
	bind_key('HOME', 'first-option', first_option)
	bind_key('END', 'last-option', last_option)
	bind_key('ENTER', 'select-option', select_option)
	bind_key('BS', 'prev-menu', prev_menu)
end

local function toggle_menu()
	osd.hidden = not osd.hidden
	osd:update()

	if osd.hidden then
		unbind_keys()
	else
		bind_keys()
	end
end

mp.add_forced_key_binding('TAB', 'toggle-menu', toggle_menu)
bind_keys()
load_data()
add_category_menu('0')
update_osd()