package extractfreq

import (
	"math"

	"git.crumpington.com/public/jlaudio/lib/util"
	"gonum.org/v1/gonum/stat"
)

type HarmonicWindow struct {
	TargetFreq     float64
	Amps           []float64
	Freqs          []float64
	Idx0           int
	IdxPeak        int
	IdxPeakInterp  float64
	FreqPeakInterp float64
	AmpPeak        float64
	AmpMean        float64
	AmpStd         float64
}

// Construct a window around the harmonic peak with a width of 100 cents.
func NewHarmonicWindow(
	amps []float64,
	freqs []float64,
	targetFreq float64,
	idxPeak int,
) *HarmonicWindow {
	deltaF := freqs[1] - freqs[0] // Size of frequency bins.
	fCenter := freqs[idxPeak]     // Center frequency.

	// Create a window approximately 200 cents in width.
	deltaIdx := int(math.Round(deltaF / (100 * util.CentDeltaFreq(fCenter))))
	idxMin := idxPeak - deltaIdx
	idxMax := idxPeak + deltaIdx

	if idxMin < 0 {
		idxMin = 0
	}

	if idxMax > len(freqs) {
		idxMax = len(freqs)
	}

	hw := &HarmonicWindow{
		TargetFreq: targetFreq,
		Amps:       amps[idxMin:idxMax],
		Freqs:      freqs[idxMin:idxMax],
		IdxPeak:    idxPeak,
		AmpPeak:    amps[idxPeak],
	}

	hw.AmpMean, hw.AmpStd = stat.MeanStdDev(hw.Amps, nil)
	return hw
}