/*

 Copyright (C) 2017 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 Triangle Wave Generator

*/

import Foundation

import AVFoundation

class TriangleWaveGenerator : NSObject {

    var mSampleRate: Float = 44100.0

    var mFreqHz: Float = 440.0

    var mAmplitude: Float = 0.25

    var mFrameCount: Float = 0.0

    override init() {

        super.init()

    }

    convenience init(sampleRate: Float) {

        self.init(sampleRate: sampleRate, frequency: 440.0, amplitude: 0.25)

    }

    convenience init(sampleRate: Float, frequency: Float) {

        self.init(sampleRate: sampleRate, frequency: frequency, amplitude: 0.25)

    }

    init(sampleRate: Float, frequency: Float, amplitude: Float) {

        super.init()

        self.mSampleRate = sampleRate

        self.mFreqHz = frequency

        self.mAmplitude = amplitude

    }

    func render(_ buffer: AVAudioPCMBuffer) {

        print("Buffer: \(buffer.format.description) \(buffer.description)\n")

        let nFrames = buffer.frameLength

        let nChannels = buffer.format.channelCount

        let isInterleaved = buffer.format.isInterleaved

        let amp = mAmplitude

        let phaseStep = mFreqHz / mSampleRate;

        if (isInterleaved) {

            var ptr = buffer.floatChannelData?[0]

            for frame in 0 ..< nFrames {

                let phase = fmodf(Float(frame) * phaseStep, 1.0)

                let value = (fabsf(2.0 - 4.0 * phase) - 1.0) * amp;

                for _ in 0 ..< nChannels {

                    ptr?.pointee = value;

                    ptr = ptr?.successor()

                }

            }

        } else {

            for ch in 0 ..< nChannels {

                var ptr = buffer.floatChannelData?[Int(ch)]

                for frame in 0 ..< nFrames {

                    let phase = fmodf(Float(frame) * phaseStep, 1.0)

                    let value = (fabsf(2.0 - 4.0 * phase) - 1.0) * amp;

                    ptr?.pointee = value

                    ptr = ptr?.successor()

                }

            }

        }

        mFrameCount = Float(nFrames);

    }

}