const { execFile } = require("child_process");
const process = require("process");

const PM2_EXEC_OPTIONS = {
    timeout: 5000,
    maxBuffer: 10 * 1024 * 1024,
};

/**
 * Truncate command output to keep error messages compact.
 * @param {string | Buffer} output Command output.
 * @returns {string} The truncated output text.
 */
function truncateOutput(output) {
    const text = (output || "").toString().trim();
    if (text.length > 200) {
        return text.substring(0, 200) + "...";
    }
    return text;
}

/**
 * Query PM2 for the current process list.
 * @returns {Promise<{id: string, name: string, status: string}[]>} The normalized PM2 process list.
 */
function getPM2ProcessList() {
    return new Promise((resolve, reject) => {
        execFile(
            process.platform === "win32" ? "pm2.cmd" : "pm2",
            ["jlist"],
            PM2_EXEC_OPTIONS,
            (error, stdout, stderr) => {
                if (error) {
                    const details = truncateOutput(stderr) || error.code || error.message;
                    reject(new Error(`Unable to query PM2 process list (${details}).`));
                    return;
                }

                try {
                    const parsed = JSON.parse((stdout || "").toString());
                    if (!Array.isArray(parsed)) {
                        reject(new Error("Unexpected PM2 process list output."));
                        return;
                    }

                    resolve(
                        parsed
                            .map((item) => {
                                const id = item?.pm_id != null ? String(item.pm_id) : null;
                                const name = item?.name || null;

                                if (!id && !name) {
                                    return null;
                                }

                                return {
                                    id: id || name,
                                    name: name || id,
                                    status: item?.pm2_env?.status?.toString().toLowerCase() || "unknown",
                                };
                            })
                            .filter(Boolean)
                    );
                } catch (parseError) {
                    reject(new Error(truncateOutput(stderr) || "Unable to parse PM2 process list output."));
                }
            }
        );
    });
}

module.exports = {
    getPM2ProcessList,
};