package reduction

import (
    "encoding/binary"
//    "fmt"
    "math"
)

func lowPassFilter(input []float64, cutoffFrequency, sampleRate float64) []float64 {
    rc := 1.0 / (cutoffFrequency * 2.0 * math.Pi)
    dt := 1.0 / sampleRate
    alpha := dt / (rc + dt)
    output := make([]float64, len(input))
    output[0] = input[0]

    for i := 1; i < len(input); i++ {
        output[i] = output[i-1] + alpha*(input[i]-output[i-1])
    }
    return output
}

func ProcessAudio(input []byte, cutoffFrequency, sampleRate float64) ([]byte, error) {
    numSamples := len(input) / 2
    samples := make([]float64, numSamples)
    for i := 0; i < numSamples; i++ {
        samples[i] = float64(int16(binary.BigEndian.Uint16(input[i*2:])))
    }
    filteredSamples := lowPassFilter(samples, cutoffFrequency, sampleRate)
    output := make([]byte, len(input))
    for i := 0; i < numSamples; i++ {
        value := int16(filteredSamples[i])
        binary.LittleEndian.PutUint16(output[i*2:], uint16(value))
    }
    return output, nil
}

/*
func main() {
    inputBuffer := make([]byte, 16000*2) // 1 секунда на 16 кГц, 16 бит
    cutoffFrequency := 200.0 // Частота среза в Гц
    sampleRate := 16000.0    // Частота дискретизации в Гц
    processedBuffer, err := ProcessAudio(inputBuffer, cutoffFrequency, sampleRate)
    if err != nil {
        fmt.Println("Ошибка:", err)
        return
    }
    fmt.Println("Обработка завершена, размер выходного буфера:", len(processedBuffer))
}
*/