import { RtpEncodingParameters } from '../../RtpParameters';

export function getRtpEncodings(
	{
		offerMediaObject,
		track
	}:
	{
		offerMediaObject: any;
		track: MediaStreamTrack;
	}
): RtpEncodingParameters[]
{
	// First media SSRC (or the only one).
	let firstSsrc;
	const ssrcs = new Set();

	for (const line of offerMediaObject.ssrcs || [])
	{
		if (line.attribute !== 'msid')
			continue;

		const trackId = line.value.split(' ')[1];

		if (trackId === track.id)
		{
			const ssrc = line.id;

			ssrcs.add(ssrc);

			if (!firstSsrc)
				firstSsrc = ssrc;
		}
	}

	if (ssrcs.size === 0)
		throw new Error(`a=ssrc line with msid information not found [track.id:${track.id}]`);

	const ssrcToRtxSsrc = new Map();

	// First assume RTX is used.
	for (const line of offerMediaObject.ssrcGroups || [])
	{
		if (line.semantics !== 'FID')
			continue;

		let [ ssrc, rtxSsrc ] = line.ssrcs.split(/\s+/);

		ssrc = Number(ssrc);
		rtxSsrc = Number(rtxSsrc);

		if (ssrcs.has(ssrc))
		{
			// Remove both the SSRC and RTX SSRC from the set so later we know that they
			// are already handled.
			ssrcs.delete(ssrc);
			ssrcs.delete(rtxSsrc);

			// Add to the map.
			ssrcToRtxSsrc.set(ssrc, rtxSsrc);
		}
	}

	// If the set of SSRCs is not empty it means that RTX is not being used, so take
	// media SSRCs from there.
	for (const ssrc of ssrcs)
	{
		// Add to the map.
		ssrcToRtxSsrc.set(ssrc, null);
	}

	const encodings: RtpEncodingParameters[] = [];

	for (const [ ssrc, rtxSsrc ] of ssrcToRtxSsrc)
	{
		const encoding: any = { ssrc };

		if (rtxSsrc)
			encoding.rtx = { ssrc: rtxSsrc };

		encodings.push(encoding);
	}

	return encodings;
}

/**
 * Adds multi-ssrc based simulcast into the given SDP media section offer.
 */
export function addLegacySimulcast(
	{
		offerMediaObject,
		track,
		numStreams
	}:
	{
		offerMediaObject: any;
		track: MediaStreamTrack;
		numStreams: number;
	}
): void
{
	if (numStreams <= 1)
		throw new TypeError('numStreams must be greater than 1');

	let firstSsrc: any;
	let firstRtxSsrc: any;
	let streamId: any;

	// Get the SSRC.
	const ssrcMsidLine = (offerMediaObject.ssrcs || [])
		.find((line: any) =>
		{
			if (line.attribute !== 'msid')
				return false;

			const trackId = line.value.split(' ')[1];

			if (trackId === track.id)
			{
				firstSsrc = line.id;
				streamId = line.value.split(' ')[0];

				return true;
			}
			else
			{
				return false;
			}
		});

	if (!ssrcMsidLine)
		throw new Error(`a=ssrc line with msid information not found [track.id:${track.id}]`);

	// Get the SSRC for RTX.
	(offerMediaObject.ssrcGroups || [])
		.some((line: any) =>
		{
			if (line.semantics !== 'FID')
				return false;

			const ssrcs = line.ssrcs.split(/\s+/);

			if (Number(ssrcs[0]) === firstSsrc)
			{
				firstRtxSsrc = Number(ssrcs[1]);

				return true;
			}
			else
			{
				return false;
			}
		});

	const ssrcCnameLine = offerMediaObject.ssrcs
		.find((line: any) => (line.attribute === 'cname' && line.id === firstSsrc));

	if (!ssrcCnameLine)
		throw new Error(`a=ssrc line with cname information not found [track.id:${track.id}]`);

	const cname = ssrcCnameLine.value;
	const ssrcs = [];
	const rtxSsrcs = [];

	for (let i = 0; i < numStreams; ++i)
	{
		ssrcs.push(firstSsrc + i);

		if (firstRtxSsrc)
			rtxSsrcs.push(firstRtxSsrc + i);
	}

	offerMediaObject.ssrcGroups = offerMediaObject.ssrcGroups || [];
	offerMediaObject.ssrcs = offerMediaObject.ssrcs || [];

	offerMediaObject.ssrcGroups.push(
		{
			semantics : 'SIM',
			ssrcs     : ssrcs.join(' ')
		});

	for (let i = 0; i < ssrcs.length; ++i)
	{
		const ssrc = ssrcs[i];

		offerMediaObject.ssrcs.push(
			{
				id        : ssrc,
				attribute : 'cname',
				value     : cname
			});

		offerMediaObject.ssrcs.push(
			{
				id        : ssrc,
				attribute : 'msid',
				value     : `${streamId} ${track.id}`
			});
	}

	for (let i = 0; i < rtxSsrcs.length; ++i)
	{
		const ssrc = ssrcs[i];
		const rtxSsrc = rtxSsrcs[i];

		offerMediaObject.ssrcs.push(
			{
				id        : rtxSsrc,
				attribute : 'cname',
				value     : cname
			});

		offerMediaObject.ssrcs.push(
			{
				id        : rtxSsrc,
				attribute : 'msid',
				value     : `${streamId} ${track.id}`
			});

		offerMediaObject.ssrcGroups.push(
			{
				semantics : 'FID',
				ssrcs     : `${ssrc} ${rtxSsrc}`
			});
	}
}