/**
 * Video player for go2rtc streaming application.
 *
 * All modern web technologies are supported in almost any browser except Apple Safari.
 *
 * Support:
 * - RTCPeerConnection for Safari iOS 11.0+
 * - IntersectionObserver for Safari iOS 12.2+
 *
 * Doesn't support:
 * - MediaSource for Safari iOS all
 * - Customized built-in elements (extends HTMLVideoElement) because all Safari
 * - Public class fields because old Safari (before 14.0)
 * - Autoplay for Safari
 */
export class VideoRTC extends HTMLElement {
    constructor() {
        super();

        this.DISCONNECT_TIMEOUT = 5000;
        this.RECONNECT_TIMEOUT = 30000;

        this.CODECS = [
            "avc1.640029",      // H.264 high 4.1 (Chromecast 1st and 2nd Gen)
            "avc1.64002A",      // H.264 high 4.2 (Chromecast 3rd Gen)
            "avc1.640033",      // H.264 high 5.1 (Chromecast with Google TV)
            "hvc1.1.6.L153.B0", // H.265 main 5.1 (Chromecast Ultra)
            "mp4a.40.2",        // AAC LC
            "mp4a.40.5",        // AAC HE
            "opus",             // OPUS Chrome
        ];

        /**
         * [config] Supported modes (webrtc, mse, mp4, mjpeg).
         * @type {string}
         */
        this.mode = "webrtc,mse,mp4,mjpeg";

        /**
         * [config] Run stream when not displayed on the screen. Default `false`.
         * @type {boolean}
         */
        this.background = false;

        /**
         * [config] Run stream only when player in the viewport. Stop when user scroll out player.
         * Value is percentage of visibility from `0` (not visible) to `1` (full visible).
         * Default `0` - disable;
         * @type {number}
         */
        this.visibilityThreshold = 0;

        /**
         * [config] Run stream only when browser page on the screen. Stop when user change browser
         * tab or minimise browser windows.
         * @type {boolean}
         */
        this.visibilityCheck = true;

        /**
         * [config] WebRTC configuration
         * @type {RTCConfiguration}
         */
        this.pcConfig = {
            iceServers: [{urls: 'stun:stun.l.google.com:19302'}],
            sdpSemantics: 'unified-plan',  // important for Chromecast 1
        };

        /**
         * [info] WebSocket connection state. Values: CONNECTING, OPEN, CLOSED
         * @type {number}
         */
        this.wsState = WebSocket.CLOSED;

        /**
         * [info] WebRTC connection state.
         * @type {number}
         */
        this.pcState = WebSocket.CLOSED;

        /**
         * @type {HTMLVideoElement}
         */
        this.video = null;

        /**
         * @type {WebSocket}
         */
        this.ws = null;

        /**
         * @type {string|URL}
         */
        this.wsURL = "";

        /**
         * @type {RTCPeerConnection}
         */
        this.pc = null;

        /**
         * @type {number}
         */
        this.connectTS = 0;

        /**
         * @type {string}
         */
        this.mseCodecs = "";

        /**
         * [internal] Disconnect TimeoutID.
         * @type {number}
         */
        this.disconnectTID = 0;

        /**
         * [internal] Reconnect TimeoutID.
         * @type {number}
         */
        this.reconnectTID = 0;

        /**
         * [internal] Handler for receiving Binary from WebSocket.
         * @type {Function}
         */
        this.ondata = null;

        /**
         * [internal] Handlers list for receiving JSON from WebSocket
         * @type {Object.<string,Function>}}
         */
        this.onmessage = null;
    }

    /**
     * Set video source (WebSocket URL). Support relative path.
     * @param {string|URL} value
     */
    set src(value) {
        if (typeof value !== "string") value = value.toString();
        if (value.startsWith("http")) {
            value = "ws" + value.substring(4);
        } else if (value.startsWith("/")) {
            value = "ws" + location.origin.substring(4) + value;
        }

        this.wsURL = value;

        this.onconnect();
    }

    /**
     * Play video. Support automute when autoplay blocked.
     * https://developer.chrome.com/blog/autoplay/
     */
    play() {
        this.video.play().catch(er => {
            if (er.name === "NotAllowedError" && !this.video.muted) {
                this.video.muted = true;
                this.video.play().catch(() => console.debug);
            }
        });
    }

    /**
     * Send message to server via WebSocket
     * @param {Object} value
     */
    send(value) {
        if (this.ws) this.ws.send(JSON.stringify(value));
    }

    codecs(type) {
        const test = type === "mse"
            ? codec => MediaSource.isTypeSupported(`video/mp4; codecs="${codec}"`)
            : codec => this.video.canPlayType(`video/mp4; codecs="${codec}"`);
        return this.CODECS.filter(test).join();
    }

    /**
     * `CustomElement`. Invoked each time the custom element is appended into a
     * document-connected element.
     */
    connectedCallback() {
        if (this.disconnectTID) {
            clearTimeout(this.disconnectTID);
            this.disconnectTID = 0;
        }

        // because video autopause on disconnected from DOM
        if (this.video) {
            const seek = this.video.seekable;
            if (seek.length > 0) {
                this.video.currentTime = seek.end(seek.length - 1);
            }
            this.play();
        } else {
            this.oninit();
        }

        this.onconnect();
    }

    /**
     * `CustomElement`. Invoked each time the custom element is disconnected from the
     * document's DOM.
     */
    disconnectedCallback() {
        if (this.background || this.disconnectTID) return;
        if (this.wsState === WebSocket.CLOSED && this.pcState === WebSocket.CLOSED) return;

        this.disconnectTID = setTimeout(() => {
            if (this.reconnectTID) {
                clearTimeout(this.reconnectTID);
                this.reconnectTID = 0;
            }

            this.disconnectTID = 0;

            this.ondisconnect();
        }, this.DISCONNECT_TIMEOUT);
    }

    /**
     * Creates child DOM elements. Called automatically once on `connectedCallback`.
     */
    oninit() {
        this.video = document.createElement("video");
        this.video.controls = true;
        this.video.playsInline = true;
        this.video.preload = "auto";

        this.video.style.display = "block"; // fix bottom margin 4px
        this.video.style.width = "100%";
        this.video.style.height = "100%"

        this.appendChild(this.video);

        if (this.background) return;

        if ("hidden" in document && this.visibilityCheck) {
            document.addEventListener("visibilitychange", () => {
                if (document.hidden) {
                    this.disconnectedCallback();
                } else if (this.isConnected) {
                    this.connectedCallback();
                }
            })
        }

        if ("IntersectionObserver" in window && this.visibilityThreshold) {
            const observer = new IntersectionObserver(entries => {
                entries.forEach(entry => {
                    if (!entry.isIntersecting) {
                        this.disconnectedCallback();
                    } else if (this.isConnected) {
                        this.connectedCallback();
                    }
                });
            }, {threshold: this.visibilityThreshold});
            observer.observe(this);
        }
    }

    /**
     * Connect to WebSocket. Called automatically on `connectedCallback`.
     * @return {boolean} true if the connection has started.
     */
    onconnect() {
        if (!this.isConnected || !this.wsURL || this.ws || this.pc) return false;

        // CLOSED or CONNECTING => CONNECTING
        this.wsState = WebSocket.CONNECTING;

        this.connectTS = Date.now();

        this.ws = new WebSocket(this.wsURL);
        this.ws.binaryType = "arraybuffer";
        this.ws.addEventListener("open", ev => this.onopen(ev));
        this.ws.addEventListener("close", ev => this.onclose(ev));

        return true;
    }

    ondisconnect() {
        this.wsState = WebSocket.CLOSED;
        if (this.ws) {
            this.ws.close();
            this.ws = null;
        }

        this.pcState = WebSocket.CLOSED;
        if (this.pc) {
            this.pc.close();
            this.pc = null;
        }
    }

    /**
     * @returns {Array.<string>} of modes (mse, webrtc, etc.)
     */
    onopen() {
        // CONNECTING => OPEN
        this.wsState = WebSocket.OPEN;

        this.ws.addEventListener("message", ev => {
            if (typeof ev.data === "string") {
                const msg = JSON.parse(ev.data);
                for (const mode in this.onmessage) {
                    this.onmessage[mode](msg);
                }
            } else {
                this.ondata(ev.data);
            }
        });

        this.ondata = null;
        this.onmessage = {};

        const modes = [];

        if (this.mode.indexOf("mse") >= 0 && "MediaSource" in window) { // iPhone
            modes.push("mse");
            this.onmse();
        } else if (this.mode.indexOf("mp4") >= 0) {
            modes.push("mp4");
            this.onmp4();
        }

        if (this.mode.indexOf("webrtc") >= 0 && "RTCPeerConnection" in window) { // macOS Desktop app
            modes.push("webrtc");
            this.onwebrtc();
        }

        if (this.mode.indexOf("mjpeg") >= 0) {
            if (modes.length) {
                this.onmessage["mjpeg"] = msg => {
                    if (msg.type !== "error" || msg.value.indexOf(modes[0]) !== 0) return;
                    this.onmjpeg();
                }
            } else {
                modes.push("mjpeg");
                this.onmjpeg();
            }
        }

        return modes;
    }

    /**
     * @return {boolean} true if reconnection has started.
     */
    onclose() {
        if (this.wsState === WebSocket.CLOSED) return false;

        // CONNECTING, OPEN => CONNECTING
        this.wsState = WebSocket.CONNECTING;
        this.ws = null;

        // reconnect no more than once every X seconds
        const delay = Math.max(this.RECONNECT_TIMEOUT - (Date.now() - this.connectTS), 0);

        this.reconnectTID = setTimeout(() => {
            this.reconnectTID = 0;
            this.onconnect();
        }, delay);

        return true;
    }

    onmse() {
        const ms = new MediaSource();
        ms.addEventListener("sourceopen", () => {
            URL.revokeObjectURL(this.video.src);
            this.send({type: "mse", value: this.codecs("mse")});
        }, {once: true});

        this.video.src = URL.createObjectURL(ms);
        this.video.srcObject = null;
        this.play();

        this.mseCodecs = "";

        this.onmessage["mse"] = msg => {
            if (msg.type !== "mse") return;

            this.mseCodecs = msg.value;

            const sb = ms.addSourceBuffer(msg.value);
            sb.mode = "segments"; // segments or sequence
            sb.addEventListener("updateend", () => {
                if (sb.updating) return;

                try {
                    if (bufLen > 0) {
                        const data = buf.slice(0, bufLen);
                        bufLen = 0;
                        sb.appendBuffer(data);
                    } else if (sb.buffered && sb.buffered.length) {
                        const end = sb.buffered.end(sb.buffered.length - 1) - 15;
                        const start = sb.buffered.start(0);
                        if (end > start) {
                            sb.remove(start, end);
                            ms.setLiveSeekableRange(end, end + 15);
                        }
                        // console.debug("VideoRTC.buffered", start, end);
                    }
                } catch (e) {
                    // console.debug(e);
                }
            });

            const buf = new Uint8Array(2 * 1024 * 1024);
            let bufLen = 0;

            this.ondata = data => {
                if (sb.updating || bufLen > 0) {
                    const b = new Uint8Array(data);
                    buf.set(b, bufLen);
                    bufLen += b.byteLength;
                    // console.debug("VideoRTC.buffer", b.byteLength, bufLen);
                } else {
                    try {
                        sb.appendBuffer(data);
                    } catch (e) {
                        // console.debug(e);
                    }
                }
            }
        }
    }

    onwebrtc() {
        const pc = new RTCPeerConnection(this.pcConfig);

        /** @type {HTMLVideoElement} */
        const video2 = document.createElement("video");
        video2.addEventListener("loadeddata", ev => this.onpcvideo(ev), {once: true});

        pc.addEventListener("icecandidate", ev => {
            const candidate = ev.candidate ? ev.candidate.toJSON().candidate : "";
            this.send({type: "webrtc/candidate", value: candidate});
        });

        pc.addEventListener("track", ev => {
            // when stream already init
            if (video2.srcObject !== null) return;

            // when audio track not exist in Chrome
            if (ev.streams.length === 0) return;

            // when audio track not exist in Firefox
            if (ev.streams[0].id[0] === '{') return;

            video2.srcObject = ev.streams[0];
        });

        pc.addEventListener("connectionstatechange", () => {
            if (pc.connectionState === "failed" || pc.connectionState === "disconnected") {
                pc.close(); // stop next events

                this.pcState = WebSocket.CLOSED;
                this.pc = null;

                this.onconnect();
            }
        });

        this.onmessage["webrtc"] = msg => {
            switch (msg.type) {
                case "webrtc/candidate":
                    pc.addIceCandidate({
                        candidate: msg.value,
                        sdpMid: "0"
                    }).catch(() => console.debug);
                    break;
                case "webrtc/answer":
                    pc.setRemoteDescription({
                        type: "answer",
                        sdp: msg.value
                    }).catch(() => console.debug);
                    break;
                case "error":
                    if (msg.value.indexOf("webrtc/offer") < 0) return;
                    pc.close();
            }
        };

        // Safari doesn't support "offerToReceiveVideo"
        pc.addTransceiver("video", {direction: "recvonly"});
        pc.addTransceiver("audio", {direction: "recvonly"});

        pc.createOffer().then(offer => {
            pc.setLocalDescription(offer).then(() => {
                this.send({type: "webrtc/offer", value: offer.sdp});
            });
        });

        this.pcState = WebSocket.CONNECTING;
        this.pc = pc;
    }

    /**
     * @param ev {Event}
     */
    onpcvideo(ev) {
        if (!this.pc) return;

        /** @type {HTMLVideoElement} */
        const video2 = ev.target;
        const state = this.pc.connectionState;

        // Firefox doesn't support pc.connectionState
        if (state === "connected" || state === "connecting" || !state) {
            // Video+Audio > Video, H265 > H264, Video > Audio, WebRTC > MSE
            let rtcPriority = 0, msePriority = 0;

            /** @type {MediaStream} */
            const ms = video2.srcObject;
            if (ms.getVideoTracks().length > 0) rtcPriority += 0x220;
            if (ms.getAudioTracks().length > 0) rtcPriority += 0x102;

            if (this.mseCodecs.indexOf("hvc1.") >= 0) msePriority += 0x230;
            if (this.mseCodecs.indexOf("avc1.") >= 0) msePriority += 0x210;
            if (this.mseCodecs.indexOf("mp4a.") >= 0) msePriority += 0x101;

            if (rtcPriority >= msePriority) {
                this.video.srcObject = ms;
                this.play();

                this.pcState = WebSocket.OPEN;

                this.wsState = WebSocket.CLOSED;
                this.ws.close();
                this.ws = null;
            } else {
                this.pcState = WebSocket.CLOSED;
                this.pc.close();
                this.pc = null;
            }
        }

        video2.srcObject = null;
    }

    onmjpeg() {
        this.ondata = data => {
            this.video.controls = false;
            this.video.poster = "data:image/jpeg;base64," + VideoRTC.btoa(data);
        };

        this.send({type: "mjpeg"});
    }

    onmp4() {
        /** @type {HTMLCanvasElement} **/
        const canvas = document.createElement("canvas");
        /** @type {CanvasRenderingContext2D} */
        let context;

        /** @type {HTMLVideoElement} */
        const video2 = document.createElement("video");
        video2.autoplay = true;
        video2.playsInline = true;
        video2.muted = true;

        video2.addEventListener("loadeddata", ev => {
            if (!context) {
                canvas.width = video2.videoWidth;
                canvas.height = video2.videoHeight;
                context = canvas.getContext('2d');
            }

            context.drawImage(video2, 0, 0, canvas.width, canvas.height);

            this.video.controls = false;
            this.video.poster = canvas.toDataURL("image/jpeg");
        });

        this.ondata = data => {
            video2.src = "data:video/mp4;base64," + VideoRTC.btoa(data);
        };

        this.send({type: "mp4", value: this.codecs("mp4")});
    }

    static btoa(buffer) {
        const bytes = new Uint8Array(buffer);
        const len = bytes.byteLength;
        let binary = "";
        for (let i = 0; i < len; i++) {
            binary += String.fromCharCode(bytes[i]);
        }
        return window.btoa(binary);
    }
}