import { nextPow2, realFftMagnitude } from "./yin.js";

const A4_FREQ = 440;
const A4_MIDI = 69;

/**
 * Compute a 12-bin pitch-class chromagram for a single frame using the
 * vendored real FFT. Energy below 30 Hz or above the Nyquist is ignored.
 */
export function chromagramFromFrame(
    frame: Float32Array,
    sampleRate: number,
    minFreq = 30
): Float32Array {
    const out = new Float32Array(12);
    if (frame.length < 8) return out;
    const mag = realFftMagnitude(frame);
    const fftSize = nextPow2(frame.length);
    const nyquist = sampleRate / 2;
    for (let k = 1; k < mag.length; k++) {
        const freq = (k * sampleRate) / fftSize;
        if (freq < minFreq || freq >= nyquist) continue;
        // k starts at 1 with sampleRate > 0, so freq > 0 and the log is finite.
        const midi = A4_MIDI + 12 * Math.log2(freq / A4_FREQ);
        const pc = ((Math.round(midi) % 12) + 12) % 12;
        const m = mag[k]!;
        out[pc] = out[pc]! + m;
    }
    return out;
}

/** Normalise a chromagram in-place so its max value is 1 (or zero remains zero). */
export function normaliseChroma(chroma: Float32Array): Float32Array {
    let max = 0;
    for (let i = 0; i < chroma.length; i++) {
        const v = chroma[i]!;
        if (v > max) max = v;
    }
    if (max === 0) return chroma;
    for (let i = 0; i < chroma.length; i++) {
        chroma[i] = chroma[i]! / max;
    }
    return chroma;
}

/** Sum two same-length chromagrams in-place into `acc`. */
export function accumulateChroma(
    acc: Float32Array,
    add: Float32Array
): Float32Array {
    const len = Math.min(acc.length, add.length);
    for (let i = 0; i < len; i++) {
        acc[i] = acc[i]! + add[i]!;
    }
    return acc;
}