import { AudioDocument } from "@suaveplan/audio-core";

const PAGE_SIZE = 1024;

/**
 * Build an `AudioDocument` from pre-computed channel data. Splits each
 * channel into pages of `PAGE_SIZE` samples.
 */
export function buildDoc(
    channels: Float32Array[],
    sampleRate: number
): AudioDocument {
    const sourceLength = channels[0]?.length ?? 0;
    const pages: { channelData: Float32Array[]; startSample: number }[] = [];
    for (let start = 0; start < sourceLength; start += PAGE_SIZE) {
        const len = Math.min(PAGE_SIZE, sourceLength - start);
        const pageData: Float32Array[] = channels.map((ch) =>
            ch.subarray(start, start + len)
        );
        pages.push({ channelData: pageData, startSample: start });
    }
    return new AudioDocument({
        sampleRate,
        channels: channels.length,
        sourceLength,
        pages,
    });
}

/**
 * Generate a sine-wave channel buffer at the given amplitude, frequency, and
 * duration. Amplitude is linear (1.0 = 0 dBFS).
 */
export function sine(
    amplitude: number,
    frequencyHz: number,
    sampleRate: number,
    durationSeconds: number
): Float32Array {
    const n = Math.round(durationSeconds * sampleRate);
    const out = new Float32Array(n);
    const w = (2 * Math.PI * frequencyHz) / sampleRate;
    for (let i = 0; i < n; i++) out[i] = amplitude * Math.sin(w * i);
    return out;
}

/** Constant-DC channel. */
export function constant(value: number, n: number): Float32Array {
    const out = new Float32Array(n);
    out.fill(value);
    return out;
}

/** Concatenate channel segments. */
export function concat(...segments: Float32Array[]): Float32Array {
    let total = 0;
    for (const s of segments) total += s.length;
    const out = new Float32Array(total);
    let p = 0;
    for (const s of segments) {
        out.set(s, p);
        p += s.length;
    }
    return out;
}