package wav

import (
    "errors"
    "math"
    "time"
)

var (
    ErrPCMChunkNotFound = errors.New("PCM Chunk not found in audio file")
)

func nullTermStr(b []byte) string {
    return string(b[:clen(b)])
}

func clen(n []byte) int {
    for i := 0; i < len(n); i++ {
        if n[i] == 0 {
            return i
        }
    }
    return len(n)
}

func bytesNumFromDuration(dur time.Duration, sampleRate, bitDepth int) int {
    k := bitDepth / 8
    return samplesNumFromDuration(dur, sampleRate) * k
}

func samplesNumFromDuration(dur time.Duration, sampleRate int) int {
    return int(math.Floor(float64(dur / sampleDuration(sampleRate))))
}

func sampleDuration(sampleRate int) time.Duration {
    if sampleRate == 0 {
        return 0
    }
    return time.Second / time.Duration(math.Abs(float64(sampleRate)))
}