-- Copyright 2025 David Vazgenovich Shakaryan

local epg = {}
local mt = {}
mt.__index = mt

function epg.new()
	return setmetatable({channels = {}}, mt)
end

-- local (non-DST) offset from UTC
local tz_offset
do
	local t = os.time()
	tz_offset = os.time(os.date('*t', t)) - os.time(os.date('!*t', t))
end

local function parse_time(str)
	local y, m, d, hh, mm, ss, zsign, zh, zm = str:match(
		'(%d%d%d%d)(%d%d)(%d%d)(%d%d)(%d%d)(%d%d) ([+-])(%d%d)(%d%d)')
	local dt = {
		year = y, month = m, day = d,
		hour = hh, min = mm, sec = ss, isdst = false}
	return os.time(dt) + tz_offset -
		(tonumber(zsign..zh) * 3600 + tonumber(zsign..zm) * 60)
end

function mt:load_xc_data(data)
	for _, v in ipairs(data) do
		local ch = v.channel:lower()
		local prog = {
			start = parse_time(v.start),
			stop = parse_time(v.stop),
			title = v.title,
			desc = v.desc,
		}

		if self.channels[ch] then
			self.channels[ch][#self.channels[ch]+1] = prog
		else
			self.channels[ch] = {prog}
		end
	end

	for _, progs in pairs(self.channels) do
		table.sort(progs, function(a, b)
			return a.start < b.start
		end)
	end
end

function mt:channel_programmes(ch)
	return self.channels[ch]
end

function mt:scheduled_programme(ch, time)
	local progs = self.channels[ch]
	if not progs then
		return
	end

	for _, v in ipairs(progs) do
		if time >= v.start and time < v.stop then
			return v
		end
	end
end

return epg