--[[---------------------------------------------------------
	Media Player Metadata

	All media metadata is cached in an SQLite table for quick
	lookup and to prevent unnecessary network requests.
-----------------------------------------------------------]]

MediaPlayer.Metadata = {}

---
-- Default metadata table name
-- @type String
--
local TableName = "mediaplayer_metadata"

---
-- SQLite table struct
-- @type String
--
local TableStruct = string.format([[
CREATE TABLE %s (
	id              VARCHAR(48) PRIMARY KEY,
	title           VARCHAR(128),
	duration        INTEGER NOT NULL DEFAULT 0,
	extra           VARCHAR(2048),
	request_count   INTEGER NOT NULL DEFAULT 1,
	last_request    INTEGER NOT NULL DEFAULT 0,
	last_updated    INTEGER NOT NULL DEFAULT 0,
	expired         BOOLEAN NOT NULL DEFAULT 0
)]], TableName)

---
-- Maximum cache age before it expires; currently one week in seconds.
-- @type Number
--
local MaxCacheAge = 604800

---
-- Query the metadata table for the given media object's metadata.
-- If the metadata is older than one week, it is ignored and replaced upon
-- saving.
--
-- @param media     Media service object.
-- @return table    Cached metadata results.
--
function MediaPlayer.Metadata:Query( media )
	local id = media:UniqueID()
	if not id then return end

	local query = ("SELECT * FROM `%s` WHERE id=%s"):format(TableName, sql.SQLStr(id))

	if MediaPlayer.DEBUG then
		print("MediaPlayer.Metadata.Query")
		print(query)
	end

	local results = sql.QueryRow(query)

	if results then
		local expired = ( tonumber(results.expired) == 1 )

		-- Media metadata has been marked as out-of-date
		if expired then
			return nil
		end

		local lastupdated = tonumber( results.last_updated )
		local timediff = os.time() - lastupdated

		if timediff > MaxCacheAge then

			-- Set metadata entry as expired
			query = "UPDATE `%s` SET expired=1 WHERE id=%s"
			query = query:format( TableName, sql.SQLStr(id) )

			if MediaPlayer.DEBUG then
				print("MediaPlayer.Metadata.Query: Setting entry as expired")
				print(query)
			end

			sql.Query( query )

			return nil

		else
			return results
		end
	elseif results == false then
		ErrorNoHalt("MediaPlayer.Metadata.Query: There was an error executing the SQL query\n")
		print(query)
	end

	return nil
end

---
-- Save or update the given media object into the metadata table.
--
-- @param media     Media service object.
-- @return table    SQL query results.
--
function MediaPlayer.Metadata:Save( media )
	local id = media:UniqueID()
	if not id then return end

	local query = ("SELECT expired FROM `%s` WHERE id=%s"):format(TableName, sql.SQLStr(id))
	local results = sql.Query(query)

	if istable(results) then -- update

		if MediaPlayer.DEBUG then
			print("MediaPlayer.Metadata.Save Results:")
			PrintTable(results)
		end

		results = results[1]

		local expired = ( tonumber(results.expired) == 1 )

		if expired then

			-- Update possible new metadata
			local extra = (media._metadata and media._metadata.extra) or {}
			query = "UPDATE `%s` SET request_count=request_count+1, title=%s, duration=%d, extra=%s, last_request=%s, last_updated=%s, expired=0 WHERE id=%s"
			query = query:format( TableName,
						sql.SQLStr( media:Title() ),
						media:Duration() or 0,
						sql.SQLStr( util.TableToJSON(extra) ),
						os.time(),
						os.time(),
						sql.SQLStr(id) )

		else

			query = "UPDATE `%s` SET request_count=request_count+1, last_request=%s WHERE id=%s"
			query = query:format( TableName, os.time(), sql.SQLStr(id) )

		end

	else -- insert

		local extra = (media._metadata and media._metadata.extra) or {}
		query = string.format( "INSERT INTO `%s` ", TableName ) ..
			"(id,title,duration,extra,last_request,last_updated) VALUES (" ..
			string.format( "%s,", sql.SQLStr(id) ) ..
			string.format( "%s,", sql.SQLStr( media:Title() ) ) ..
			string.format( "%d,", media:Duration() or 0 ) ..
			string.format( "%s,", sql.SQLStr( util.TableToJSON(extra) ) ) ..
			string.format( "%d,", os.time() ) ..
			string.format( "%d)", os.time() )

	end

	if MediaPlayer.DEBUG then
		print("MediaPlayer.Metadata.Save")
		print(query)
	end

	results = sql.Query(query)

	if results == false then
		ErrorNoHalt("MediaPlayer.Metadata.Save: There was an error executing the SQL query\n")
		print(query)
	end

	return results
end

-- Create the SQLite table if it doesn't exist
if not sql.TableExists(TableName) then
	Msg("MediaPlayer.Metadata: Creating `" .. TableName .. "` table...\n")
	sql.Query(TableStruct)
end

if SERVER then
	---
	-- Truncates (clears) all rows from the metadata cache table.
	-- Useful for forcing a full re-fetch of all media metadata.
	--
	-- @return boolean  True on success, false on failure.
	--
	function MediaPlayer.Metadata:Truncate()
		local query = ("DELETE FROM `%s`"):format(TableName)

		if MediaPlayer.DEBUG then
			print("MediaPlayer.Metadata.Truncate")
			print(query)
		end

		local result = sql.Query(query)

		if result == false then
			ErrorNoHalt("MediaPlayer.Metadata.Truncate: SQL error: " .. tostring(sql.LastError()) .. "\n")
			return false
		end

		return true
	end
end