import { spawn } from "node:child_process";
import { mkdir, mkdtemp, rm, stat } from "node:fs/promises";
import { tmpdir } from "node:os";
import { join } from "node:path";
import ffmpegInstaller from "@ffmpeg-installer/ffmpeg";

/** Path of the on-the-fly fixture video. Cached per Vitest worker. */
let fixturePath: string | undefined;
let fixtureDir: string | undefined;

/**
 * Synthesise a 5-second 320×240 colour-gradient MP4 once per worker and return
 * its absolute path. Subsequent calls return the cached path. Uses ffmpeg's
 * `lavfi` virtual source so no checked-in binary is required.
 */
export async function getFixtureVideo(): Promise<string> {
    if (fixturePath !== undefined) {
        return fixturePath;
    }
    const dir = await mkdtemp(join(tmpdir(), "vt-fixture-"));
    const out = join(dir, "fixture.mp4");
    await new Promise<void>((resolve, reject) => {
        const child = spawn(
            ffmpegInstaller.path,
            [
                "-y",
                "-f",
                "lavfi",
                "-i",
                "testsrc=duration=5:size=320x240:rate=10",
                "-pix_fmt",
                "yuv420p",
                "-c:v",
                "libx264",
                "-preset",
                "ultrafast",
                "-tune",
                "zerolatency",
                out,
            ],
            { stdio: "pipe" }
        );
        let stderr = "";
        child.stderr.on("data", (chunk) => {
            stderr += String(chunk);
        });
        child.once("error", reject);
        child.once("exit", (code) => {
            if (code === 0) {
                resolve();
            } else {
                reject(new Error(`ffmpeg fixture build failed: ${stderr}`));
            }
        });
    });
    const fileStat = await stat(out);
    if (fileStat.size === 0) {
        throw new Error("fixture video has zero bytes");
    }
    fixtureDir = dir;
    fixturePath = out;
    return out;
}

/** Create a unique tmp output directory for one test. */
export async function makeOutputDir(label: string): Promise<string> {
    const dir = await mkdtemp(join(tmpdir(), `vt-${label}-`));
    await mkdir(dir, { recursive: true });
    return dir;
}

/** Best-effort cleanup; safe to ignore failures (Windows / locked files). */
export async function safeRm(path: string): Promise<void> {
    try {
        await rm(path, { recursive: true, force: true });
    } catch {
        // ignored
    }
}

/** Clear the cached fixture (used by setup teardown). */
export async function clearFixtureCache(): Promise<void> {
    if (fixtureDir !== undefined) {
        await safeRm(fixtureDir);
    }
    fixturePath = undefined;
    fixtureDir = undefined;
}