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description("Channel mixing rules for AudioNodes.");

var context = 0;
var sampleRate = 44100;
var renderNumberOfChannels = 8;
var singleTestFrameLength = 8;
var testBuffers;

// A list of connections to an AudioNode input, each of which is to be used in one or more specific test cases.
// Each element in the list is a string, with the number of connections corresponding to the length of the string,
// and each character in the string is from '1' to '8' representing a 1 to 8 channel connection (from an AudioNode output).
// For example, the string "128" means 3 connections, having 1, 2, and 8 channels respectively.
var connectionsList = ["1", "2", "3", "4", "5", "6", "7", "8", "11", "12", "14", "18", "111", "122", "123", "124", "128"];

// A list of mixing rules, each of which will be tested against all of the connections in connectionsList.
var mixingRulesList = [
    {channelCount: 2, channelCountMode: "max", channelInterpretation: "speakers"},
    {channelCount: 4, channelCountMode: "clamped-max", channelInterpretation: "speakers"},

    // Test up-down-mix to some explicit speaker layouts.
    {channelCount: 1, channelCountMode: "explicit", channelInterpretation: "speakers"},
    {channelCount: 2, channelCountMode: "explicit", channelInterpretation: "speakers"},
    {channelCount: 4, channelCountMode: "explicit", channelInterpretation: "speakers"},
    {channelCount: 6, channelCountMode: "explicit", channelInterpretation: "speakers"},

    {channelCount: 2, channelCountMode: "max", channelInterpretation: "discrete"},
    {channelCount: 4, channelCountMode: "clamped-max", channelInterpretation: "discrete"},
    {channelCount: 4, channelCountMode: "explicit", channelInterpretation: "discrete"},
    {channelCount: 8, channelCountMode: "explicit", channelInterpretation: "discrete"},
];

var numberOfTests = mixingRulesList.length * connectionsList.length;

// Create an n-channel buffer, with all sample data zero except for a shifted impulse.
// The impulse position depends on the channel index.
// For example, for a 4-channel buffer:
// channel0: 1 0 0 0 0 0 0 0
// channel1: 0 1 0 0 0 0 0 0
// channel2: 0 0 1 0 0 0 0 0
// channel3: 0 0 0 1 0 0 0 0
function createTestBuffer(numberOfChannels) {
    var buffer = context.createBuffer(numberOfChannels, singleTestFrameLength, context.sampleRate);
    for (var i = 0; i < numberOfChannels; ++i) {
        var data = buffer.getChannelData(i);
        data[i] = 1;
    }
    return buffer;
}

// Discrete channel interpretation mixing:
// https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#UpMix
// up-mix by filling channels until they run out then ignore remaining dest channels.
// down-mix by filling as many channels as possible, then dropping remaining source channels.
function discreteSum(sourceBuffer, destBuffer) {
    if (sourceBuffer.length != destBuffer.length) {
        alert("discreteSum(): invalid AudioBuffer!");
        return;
    }

    var numberOfChannels = sourceBuffer.numberOfChannels < destBuffer.numberOfChannels ? sourceBuffer.numberOfChannels : destBuffer.numberOfChannels;
    var length = numberOfChannels;

    for (var c = 0; c < numberOfChannels; ++c) {
        var source = sourceBuffer.getChannelData(c);
        var dest = destBuffer.getChannelData(c);
        for (var i = 0; i < length; ++i) {
            dest[i] += source[i];
        }
    }
}

// Speaker channel interpretation mixing:
// https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#UpMix
function speakersSum(sourceBuffer, destBuffer)
{
    var numberOfSourceChannels = sourceBuffer.numberOfChannels;
    var numberOfDestinationChannels = destBuffer.numberOfChannels;
    var length = destBuffer.length;

    if (numberOfDestinationChannels == 2 && numberOfSourceChannels == 1) {
        // Handle mono -> stereo case (summing mono channel into both left and right).
        var source = sourceBuffer.getChannelData(0);
        var destL = destBuffer.getChannelData(0);
        var destR = destBuffer.getChannelData(1);

        for (var i = 0; i < length; ++i) {
            destL[i] += source[i];
            destR[i] += source[i];
        }
    } else if (numberOfDestinationChannels == 1 && numberOfSourceChannels == 2) {
        // Handle stereo -> mono case. output += 0.5 * (input.L + input.R).
        var sourceL = sourceBuffer.getChannelData(0);
        var sourceR = sourceBuffer.getChannelData(1);
        var dest = destBuffer.getChannelData(0);

        for (var i = 0; i < length; ++i) {
            dest[i] += 0.5 * (sourceL[i] + sourceR[i]);
        }
    } else if (numberOfDestinationChannels == 6 && numberOfSourceChannels == 1) {
        // Handle mono -> 5.1 case, sum mono channel into center.
        var source = sourceBuffer.getChannelData(0);
        var dest = destBuffer.getChannelData(2);

        for (var i = 0; i < length; ++i) {
            dest[i] += source[i];
        }
    } else if (numberOfDestinationChannels == 1 && numberOfSourceChannels == 6) {
        // Handle 5.1 -> mono.
        var sourceL = sourceBuffer.getChannelData(0);
        var sourceR = sourceBuffer.getChannelData(1);
        var sourceC = sourceBuffer.getChannelData(2);
        // skip LFE for now, according to current spec.
        var sourceSL = sourceBuffer.getChannelData(4);
        var sourceSR = sourceBuffer.getChannelData(5);
        var dest = destBuffer.getChannelData(0);

        for (var i = 0; i < length; ++i) {
            dest[i] += 0.7071 * (sourceL[i] + sourceR[i]) + sourceC[i] + 0.5 * (sourceSL[i] + sourceSR[i]);
        }
    } else {
        // Fallback for unknown combinations.
        discreteSum(sourceBuffer, destBuffer);
    }
}

function scheduleTest(testNumber, connections, channelCount, channelCountMode, channelInterpretation) {
    var mixNode = context.createGain();
    mixNode.channelCount = channelCount;
    mixNode.channelCountMode = channelCountMode;
    mixNode.channelInterpretation = channelInterpretation;
    mixNode.connect(context.destination);

    for (var i = 0; i < connections.length; ++i) {
        var connectionNumberOfChannels = connections.charCodeAt(i) - "0".charCodeAt(0);

        var source = context.createBufferSource();
        // Get a buffer with the right number of channels, converting from 1-based to 0-based index.
        var buffer = testBuffers[connectionNumberOfChannels - 1];
        source.buffer = buffer;
        source.connect(mixNode);

        // Start at the right offset.
        var sampleFrameOffset = testNumber * singleTestFrameLength;
        var time = sampleFrameOffset / sampleRate;
        source.start(time);
    }
}

function computeNumberOfChannels(connections, channelCount, channelCountMode) {
    if (channelCountMode == "explicit")
        return channelCount;

    var computedNumberOfChannels = 1; // Must have at least one channel.

    // Compute "computedNumberOfChannels" based on all the connections.
    for (var i = 0; i < connections.length; ++i) {
        var connectionNumberOfChannels = connections.charCodeAt(i) - "0".charCodeAt(0);
        computedNumberOfChannels = Math.max(computedNumberOfChannels, connectionNumberOfChannels);
    }

    if (channelCountMode == "clamped-max")
        computedNumberOfChannels = Math.min(computedNumberOfChannels, channelCount);

    return computedNumberOfChannels;
}

function checkTestResult(renderedBuffer, testNumber, connections, channelCount, channelCountMode, channelInterpretation) {
    var s = "connections: " + connections + ", " + channelCountMode;

    // channelCount is ignored in "max" mode.
    if (channelCountMode == "clamped-max" || channelCountMode == "explicit") {
        s += "(" + channelCount + ")";
    }

    s += ", " + channelInterpretation;

    var computedNumberOfChannels = computeNumberOfChannels(connections, channelCount, channelCountMode);

    // Show rendered output for this test:
    //
    // console.log(s);
    // var sampleFrameOffset = testNumber * singleTestFrameLength;
    // for (var c = 0; c < renderNumberOfChannels; ++c) {
    //     var data = renderedBuffer.getChannelData(c);
    //     var s = "";
    //     for (var sampleFrame = 0; sampleFrame < singleTestFrameLength; ++sampleFrame) {
    //         s += data[sampleFrame + sampleFrameOffset] + " ";
    //     }
    //     s += "\n";
    //     console.log(s);
    // }
    // return;

    // Create a zero-initialized silent AudioBuffer with computedNumberOfChannels.
    var destBuffer = context.createBuffer(computedNumberOfChannels, singleTestFrameLength, context.sampleRate);

    // Mix all of the connections into the destination buffer.
    for (var i = 0; i < connections.length; ++i) {
        var connectionNumberOfChannels = connections.charCodeAt(i) - "0".charCodeAt(0);
        var sourceBuffer = testBuffers[connectionNumberOfChannels - 1]; // convert from 1-based to 0-based index

        if (channelInterpretation == "speakers") {
            speakersSum(sourceBuffer, destBuffer);
        } else if (channelInterpretation == "discrete") {
            discreteSum(sourceBuffer, destBuffer);
        } else {
            alert("Invalid channel interpretation!");
        }
    }

    // Validate that destBuffer matches the rendered output.
    // We need to check the rendered output at a specific sample-frame-offset corresponding
    // to the specific test case we're checking for based on testNumber.

    var sampleFrameOffset = testNumber * singleTestFrameLength;
    for (var c = 0; c < renderNumberOfChannels; ++c) {
        var renderedData = renderedBuffer.getChannelData(c);
        for (var frame = 0; frame < singleTestFrameLength; ++frame) {
            var renderedValue = renderedData[frame + sampleFrameOffset];

            var expectedValue = 0;
            if (c < destBuffer.numberOfChannels) {
                var expectedData = destBuffer.getChannelData(c);
                expectedValue = expectedData[frame];
            }

            // We may need to add an epsilon in the comparison if we add more test vectors.
            if (renderedValue != expectedValue) {
                var message = s + "rendered: " + renderedValue + " expected: " + expectedValue + " channel: " + c + " frame: " + frame;
                testFailed(s);
                return;
            }
        }
    }

    testPassed(s);
}

function checkResult(event) {
    var buffer = event.renderedBuffer;

    // Sanity check result.
    if (buffer.length != numberOfTests * singleTestFrameLength || buffer.numberOfChannels != renderNumberOfChannels) {
        testFailed("OfflineAudioContext result not of expected size!");
        finishJSTest();
        return;
    }

    // Check all the tests.
    var testNumber = 0;
    for (var m = 0; m < mixingRulesList.length; ++m) {
        var mixingRules = mixingRulesList[m];
        for (var i = 0; i < connectionsList.length; ++i, ++testNumber) {
            checkTestResult(buffer, testNumber, connectionsList[i], mixingRules.channelCount, mixingRules.channelCountMode, mixingRules.channelInterpretation);
        }
    }

    finishJSTest();
}

function runTest() {
    if (window.testRunner) {
        testRunner.dumpAsText();
        testRunner.waitUntilDone();
    }

    window.jsTestIsAsync = true;

    // Create 8-channel offline audio context.
    // Each test will render 8 sample-frames starting at sample-frame position testNumber * 8.
    var totalFrameLength = numberOfTests * singleTestFrameLength;
    context = new webkitOfflineAudioContext(renderNumberOfChannels, totalFrameLength, sampleRate);

    // Set destination to discrete mixing.
    context.destination.channelCount = renderNumberOfChannels;
    context.destination.channelCountMode = "explicit";
    context.destination.channelInterpretation = "discrete";

    // Create test buffers from 1 to 8 channels.
    testBuffers = new Array();
    for (var i = 0; i < renderNumberOfChannels; ++i) {
        testBuffers[i] = createTestBuffer(i + 1);
    }

    // Schedule all the tests.
    var testNumber = 0;
    for (var m = 0; m < mixingRulesList.length; ++m) {
        var mixingRules = mixingRulesList[m];
        for (var i = 0; i < connectionsList.length; ++i, ++testNumber) {
            scheduleTest(testNumber, connectionsList[i], mixingRules.channelCount, mixingRules.channelCountMode, mixingRules.channelInterpretation);
        }
    }

    // Render then check results.
    context.oncomplete = checkResult;
    context.startRendering();
}

runTest();

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