dizquetv/src/channel-cache.js

const SLACK = require('./constants').SLACK;

let cache = {};

let fillerPlayTimeCache = {};
let configCache = {};
let numbers = null;

async function getChannelConfig(channelDB, channelId) {
    //with lazy-loading
     
    if ( typeof(configCache[channelId]) === 'undefined') {
        let channel = await channelDB.getChannel(channelId)
        if (channel == null) {
            configCache[channelId]  = [];
        } else {
            configCache[channelId] = [channel];
        }
    }
    return configCache[channelId];
}

async function getAllNumbers(channelDB) {
    if (numbers === null) {
        let n = await channelDB.getAllChannelNumbers();
        numbers = n;
    }
    return numbers;
}

async function getAllChannels(channelDB) {
    let channelNumbers = await getAllNumbers(channelDB);
    return (await Promise.all( channelNumbers.map( async (x) => {
        return (await getChannelConfig(channelDB, x))[0];
    }) )).filter( (channel) => {
        if (channel == null) {
            console.error("Found a null channel " + JSON.stringify(channelNumbers) );
            return false;
        }
        if ( typeof(channel) === "undefined") {
            console.error("Found a undefined channel " + JSON.stringify(channelNumbers) );
            return false;
        }
        if ( typeof(channel.number) === "undefined") {
            console.error("Found a channel without number " + JSON.stringify(channelNumbers) );
            return false;
        }

        return true;
    } );
}


function saveChannelConfig(number, channel ) {
    configCache[number] = [channel];
    
    // flush the item played cache for the channel and any channel in its
    // redirect chain
    if (typeof(cache[number]) !== 'undefined') {
        let lineupItem = cache[number].lineupItem;
        for (let i = 0; i < lineupItem.redirectChannels.length; i++) {
            delete cache[ lineupItem.redirectChannels[i].number ];
        }
        delete cache[number];

    }
    numbers = null;
}

function getCurrentLineupItem(channelId, t1) {
    if (typeof(cache[channelId]) === 'undefined') {
        return null;
    }
    let recorded = cache[channelId];
    let lineupItem =  JSON.parse( JSON.stringify(recorded.lineupItem) );
    let diff = t1 - recorded.t0;
    let rem = lineupItem.duration - lineupItem.start;
    if (typeof(lineupItem.streamDuration) !== 'undefined') {
        rem = Math.min(rem, lineupItem.streamDuration);
    }
    if ( (diff <= SLACK) && (diff + SLACK < rem) ) {
        //closed the stream and opened it again let's not lose seconds for
        //no reason
        let originalT0 = recorded.lineupItem.originalT0;
        if (typeof(originalT0) === 'undefined') {
            originalT0 = recorded.t0;
        }
        if (t1 - originalT0 <= SLACK) {
            lineupItem.originalT0 = originalT0;
            return lineupItem;
        }
    }
   
    lineupItem.start += diff;
    if (typeof(lineupItem.streamDuration)!=='undefined') {
        lineupItem.streamDuration -= diff;
        if (lineupItem.streamDuration < SLACK) { //let's not waste time playing some loose seconds
            return null;
        }
    }
    if(lineupItem.start + SLACK > lineupItem.duration) {
        return null;
    }
    return lineupItem;
}

function getProgramKey(program) {
    let serverKey = "!unknown!";
    if (typeof(program.serverKey) !== 'undefined') {
        if (typeof(program.serverKey) !== 'undefined') {
            serverKey = "plex|" + program.serverKey;
        }
    }
    let programKey = "!unknownProgram!";
    if (typeof(program.key) !== 'undefined') {
        programKey = program.key;
    }
    return serverKey + "|" + programKey;
}


function getFillerKey(channelId, fillerId) {
    return channelId + "|" + fillerId;
}



function recordProgramPlayTime(programPlayTime, channelId, lineupItem, t0) {
    let remaining;
    if ( typeof(lineupItem.streamDuration) !== 'undefined') {
        remaining = lineupItem.streamDuration;
    } else {
        remaining = lineupItem.duration - lineupItem.start;
    }
    setProgramLastPlayTime(programPlayTime, channelId, lineupItem, t0 + remaining);
    if (typeof(lineupItem.fillerId) !== 'undefined') {
        fillerPlayTimeCache[ getFillerKey(channelId, lineupItem.fillerId) ] = t0 + remaining;
    }
}

function setProgramLastPlayTime(programPlayTime, channelId, lineupItem, t) {
    let programKey = getProgramKey(lineupItem);
    programPlayTime.update(channelId, programKey, t);
}

function getProgramLastPlayTime(programPlayTime, channelId, program) {
    let programKey = getProgramKey(program);
    return programPlayTime.getProgramLastPlayTime(channelId, programKey);
}

function getFillerLastPlayTime(channelId, fillerId) {
    let v = fillerPlayTimeCache[ getFillerKey(channelId, fillerId) ];
    if (typeof(v) === 'undefined') {
        return 0;
    } else {
        return v;
    }
}

function recordPlayback(programPlayTime, channelId, t0, lineupItem) {
    recordProgramPlayTime(programPlayTime, channelId, lineupItem, t0);
    
    cache[channelId] = {
        t0: t0,
        lineupItem: lineupItem,
    }
}

function clearPlayback(channelId) {
    delete cache[channelId];
}

function clear() {
    //it's not necessary to clear the playback cache and it may be undesirable
    configCache = {};
    cache = {};
    numbers = null;
}

module.exports = {
    getCurrentLineupItem: getCurrentLineupItem,
    recordPlayback: recordPlayback,
    clear: clear,
    getProgramLastPlayTime: getProgramLastPlayTime,
    getAllChannels: getAllChannels,
    getAllNumbers: getAllNumbers,
    getChannelConfig: getChannelConfig,
    saveChannelConfig: saveChannelConfig,
    getFillerLastPlayTime: getFillerLastPlayTime,
    clearPlayback: clearPlayback,
}