// Copyright (C) 2026 Zaher Salman
// SPDX-License-Identifier: GPL-3.0-or-later

// Windows support for the bundled TRIM.SP-NL engine. The Linux engine is a
// statically linked ELF binary; it cannot run natively on Windows, so the
// Windows installer also ships the whole engine as a WSL2 root filesystem and
// the main process imports it as a private distribution on first run. From then
// on the renderer launches the engine as
//   wsl.exe -d trimspNL-runtime -- /opt/trimsp-runtime/bin/trimspNL <run> [rng]
// (see prepareTrimspLaunch in TrimSPelec.js).
//
// All heavy lifting is expressed as small pure helpers so the import flow can be
// unit-tested without Windows: the only Windows-specific piece is the default
// spawner, which is injectable.

const fs = require("fs");
const path = require("path");
const childProcess = require("child_process");

// Keep these in sync with TrimSPelec.js (TRIMSP_WSL_DISTRO / TRIMSP_WSL_PREFIX)
// and packaging/wsl2/build-wsl2.sh (the prefix baked into the rootfs).
const DEFAULT_DISTRO = "trimspNL-runtime";
const DEFAULT_PREFIX = "/opt/trimsp-runtime";
const ROOTFS_BASENAME = "trimspNL-runtime-rootfs.tar.gz";

// Candidate locations for the shipped rootfs tarball, in priority order. A
// forge/electron-packager `extraResource` entry is copied *flat* into the
// resources directory (the first candidate); the `wsl-runtime/` subdirectory is
// kept for an explicit directory layout; the last tolerates running from a
// development checkout without repackaging.
function rootfsCandidates(resourcesPath) {
    const base = resourcesPath || ".";
    return [
        path.join(base, ROOTFS_BASENAME),
        path.join(base, "wsl-runtime", ROOTFS_BASENAME),
        path.join(base, "packaging", "wsl2", "out", ROOTFS_BASENAME)
    ];
}

function findRootfsTarball(resourcesPath) {
    const candidates = rootfsCandidates(resourcesPath);
    for (const candidate of candidates) {
        try {
            if (fs.statSync(candidate).isFile()) return candidate;
        } catch (error) {
            // Missing candidate: keep looking.
        }
    }
    return "";
}

// Where the imported distribution's virtual disk is stored on the Windows host.
function distroInstallDir(appDataPath, distro) {
    const name = distro || DEFAULT_DISTRO;
    return path.join(appDataPath || ".", "TrimSP", name);
}

// wsl.exe writes UTF-16LE for --list output but UTF-8 for progress text. Detect
// UTF-16LE by the presence of NUL bytes rather than trusting the locale.
function decodeWslOutput(chunk) {
    if (chunk == null) return "";
    if (!Buffer.isBuffer(chunk)) return String(chunk);
    if (chunk.length === 0) return "";
    return chunk.includes(0) ? chunk.toString("utf16le") : chunk.toString("utf8");
}

// Turn `wsl.exe --list --quiet` output into a clean list of distribution names.
function parseDistroList(text) {
    return String(text || "")
        .replace(/\u0000/g, "")
        .split(/\r?\n/)
        .map((line) => line.replace(/[\u0000\s]+$/g, "").replace(/^\u0000+/, "").trim())
        .filter((line) => line.length > 0);
}

function distroIsRegistered(text, distro) {
    const wanted = String(distro || DEFAULT_DISTRO).toLowerCase();
    return parseDistroList(text).some((name) => name.toLowerCase() === wanted);
}

// `wsl --import <Distro> <InstallLocation> <FileName> [--version <1|2>]`.
function importArgs(rootfsPath, targetDir, distro) {
    return [
        "--import",
        distro || DEFAULT_DISTRO,
        targetDir,
        rootfsPath,
        "--version",
        "2"
    ];
}

function listArgs() {
    return ["--list", "--quiet"];
}

// Default spawner: runs wsl.exe and resolves with { status, stdout, stderr }.
// Output is streamed to onOutput as it arrives so long imports can report
// progress without blocking the Electron main process.
function defaultRunWsl(args, onOutput) {
    return new Promise((resolve) => {
        let child;
        try {
            child = childProcess.spawn("wsl.exe", args, { windowsHide: true });
        } catch (error) {
            resolve({ status: -1, stdout: "", stderr: "", error: error.message || String(error) });
            return;
        }
        let stdout = "";
        let stderr = "";
        const forward = (stream, sink) => {
            stream.on("data", (chunk) => {
                const text = decodeWslOutput(chunk);
                if (sink === "stdout") stdout += text; else stderr += text;
                if (typeof onOutput === "function") onOutput(text);
            });
        };
        forward(child.stdout, "stdout");
        forward(child.stderr, "stderr");
        child.on("error", (error) => {
            resolve({ status: -1, stdout, stderr, error: error.message || String(error) });
        });
        child.on("close", (code) => {
            resolve({ status: code == null ? -1 : code, stdout, stderr, error: null });
        });
    });
}

// Ensure the private WSL2 distribution exists, importing it from the bundled
// rootfs on first run. Resolves with a plain status object; never throws.
//
// options:
//   platform       - override process.platform (tests)
//   resourcesPath  - Electron process.resourcesPath (where the rootfs ships)
//   appDataPath    - %LOCALAPPDATA% (where the distribution is imported)
//   distro         - distribution name override
//   rootfsPath     - explicit rootfs path (tests)
//   run            - spawner override, signature run(args, onOutput) -> Promise
//   onProgress     - callback receiving { phase, ... } as work proceeds
async function ensureWSLRuntime(options) {
    const opts = options || {};
    const platform = opts.platform || process.platform;
    const distro = opts.distro || DEFAULT_DISTRO;
    const run = opts.run || defaultRunWsl;
    const onProgress = typeof opts.onProgress === "function" ? opts.onProgress : function () {};

    if (platform !== "win32") {
        return { ok: true, status: "skipped", reason: "not-windows", distro: distro };
    }

    const rootfs = opts.rootfsPath || findRootfsTarball(opts.resourcesPath || "");
    if (!rootfs) {
        return {
            ok: false,
            status: "missing-rootfs",
            distro: distro,
            error: "Bundled WSL runtime archive not found under " + (opts.resourcesPath || "resources")
        };
    }

    onProgress({ phase: "checking", distro: distro });
    const listed = await run(listArgs());
    if (listed && listed.status === 0 && distroIsRegistered(listed.stdout, distro)) {
        onProgress({ phase: "ready", distro: distro });
        return { ok: true, status: "already-present", distro: distro, rootfs: rootfs };
    }

    const target = distroInstallDir(opts.appDataPath || "", distro);
    try {
        fs.mkdirSync(path.dirname(target), { recursive: true });
    } catch (error) {
        return {
            ok: false,
            status: "error",
            distro: distro,
            error: "Cannot create install directory: " + (error.message || String(error))
        };
    }

    onProgress({ phase: "importing", distro: distro, rootfs: rootfs, target: target });
    const imported = await run(importArgs(rootfs, target, distro), (text) => {
        onProgress({ phase: "importing", distro: distro, output: text });
    });
    if (!imported || imported.status !== 0) {
        return {
            ok: false,
            status: "import-failed",
            distro: distro,
            target: target,
            error: (imported && (imported.error || imported.stderr || imported.stdout)) || "wsl --import failed"
        };
    }

    onProgress({ phase: "ready", distro: distro, target: target });
    return { ok: true, status: "imported", distro: distro, target: target, rootfs: rootfs };
}

module.exports = {
    DEFAULT_DISTRO,
    DEFAULT_PREFIX,
    ROOTFS_BASENAME,
    rootfsCandidates,
    findRootfsTarball,
    distroInstallDir,
    decodeWslOutput,
    parseDistroList,
    distroIsRegistered,
    importArgs,
    listArgs,
    defaultRunWsl,
    ensureWSLRuntime
};