package sdp

import (
	"fmt"
	"math/rand"
	"strconv"
	"strings"
)

// SessionBuilderTrack represents a single track in a SessionBuilder
type SessionBuilderTrack struct {
	SSRC    uint32
	IsAudio bool
}

// SessionBuilder provides an easy way to build an SDP for an RTCPeerConnection
type SessionBuilder struct {
	IceUsername, IcePassword, Fingerprint string

	Candidates []string

	Tracks []*SessionBuilderTrack
}

// BaseSessionDescription generates a default SDP response that is ice-lite, initiates the DTLS session and supports VP8, VP9 and Opus
func BaseSessionDescription(b *SessionBuilder) *SessionDescription {
	addMediaCandidates := func(m *MediaDescription) *MediaDescription {
		m.Attributes = append(m.Attributes, b.Candidates...)
		m.Attributes = append(m.Attributes, "end-of-candidates")
		return m
	}

	audioMediaDescription := &MediaDescription{
		MediaName:      "audio 9 RTP/SAVPF 111",
		ConnectionData: "IN IP4 127.0.0.1",
		Attributes: []string{
			"setup:active",
			"mid:audio",
			"sendrecv",
			"ice-ufrag:" + b.IceUsername,
			"ice-pwd:" + b.IcePassword,
			"ice-lite",
			"fingerprint:sha-256 " + b.Fingerprint,
			"rtcp-mux",
			"rtcp-rsize",
			"rtpmap:111 opus/48000/2",
			"fmtp:111 minptime=10;useinbandfec=1",
		},
	}

	videoMediaDescription := &MediaDescription{
		MediaName:      "video 9 RTP/SAVPF 96 98",
		ConnectionData: "IN IP4 127.0.0.1",
		Attributes: []string{
			"setup:active",
			"mid:video",
			"sendrecv",
			"ice-ufrag:" + b.IceUsername,
			"ice-pwd:" + b.IcePassword,
			"ice-lite",
			"fingerprint:sha-256 " + b.Fingerprint,
			"rtcp-mux",
			"rtcp-rsize",
			"rtpmap:96 VP8/90000",
			"rtpmap:98 VP9/90000",
		},
	}

	mediaStreamsAttribute := "msid-semantic: WMS"
	for i, track := range b.Tracks {
		var attributes *[]string
		if track.IsAudio {
			attributes = &audioMediaDescription.Attributes
		} else {
			attributes = &videoMediaDescription.Attributes
		}
		appendAttr := func(attr string) {
			*attributes = append(*attributes, attr)
		}

		appendAttr("ssrc:" + fmt.Sprint(track.SSRC) + " cname:pion" + strconv.Itoa(i))
		appendAttr("ssrc:" + fmt.Sprint(track.SSRC) + " msid:pion" + strconv.Itoa(i) + " pion" + strconv.Itoa(i))
		appendAttr("ssrc:" + fmt.Sprint(track.SSRC) + " mslabel:pion" + strconv.Itoa(i))
		appendAttr("ssrc:" + fmt.Sprint(track.SSRC) + " label:pion" + strconv.Itoa(i))

		mediaStreamsAttribute += " pion" + strconv.Itoa(i)
	}

	sessionID := strconv.FormatUint(uint64(rand.Uint32())<<32+uint64(rand.Uint32()), 10)
	return &SessionDescription{
		ProtocolVersion: 0,
		Origin:          "pion-webrtc " + sessionID + " 2 IN IP4 0.0.0.0",
		SessionName:     "-",
		Timing:          []string{"0 0"},
		Attributes: []string{
			"group:BUNDLE audio video",
			mediaStreamsAttribute,
		},
		MediaDescriptions: []*MediaDescription{
			addMediaCandidates(audioMediaDescription),
			addMediaCandidates(videoMediaDescription),
		},
	}
}

// GetCodecForPayloadType scans the SessionDescription for the given payloadType and returns the codec
func GetCodecForPayloadType(payloadType uint8, sd *SessionDescription) (ok bool, codec string) {
	for _, m := range sd.MediaDescriptions {
		for _, a := range m.Attributes {
			if strings.Contains(a, "rtpmap:"+strconv.Itoa(int(payloadType))) {
				split := strings.Split(a, " ")
				if len(split) == 2 {
					split := strings.Split(split[1], "/")
					return true, split[0]
				}
			}
		}
	}
	return false, ""
}