"use strict";

/*
 * pg_dump をspawnし、標準出力を splitSizeMb ごとにローカルファイルへ分割書き出しする。
 * `split -d -a 3` 相当の3桁ゼロ埋め連番(000, 001, ...)をファイル名末尾に付与する。
 */

const fs = require("fs");
const path = require("path");
const { spawn } = require("child_process");

function pad2(n) {
    return String(n).padStart(2, "0");
}

function formatTimestamp(date = new Date()) {
    return (
        `${date.getFullYear()}${pad2(date.getMonth() + 1)}${pad2(date.getDate())}-` +
        `${pad2(date.getHours())}${pad2(date.getMinutes())}${pad2(date.getSeconds())}`
    );
}

function runPgDump({
    pgDumpBin,
    host,
    port,
    user,
    password,
    database,
    outputDir,
    splitSizeMb,
    prefix = "postgres-",
    ext = ".dmp",
    timestamp = formatTimestamp(),
}) {
    return new Promise((resolve, reject) => {
        fs.mkdirSync(outputDir, { recursive: true });

        const splitSizeBytes = Number(splitSizeMb) * 1024 * 1024;
        const baseName = `${prefix}${timestamp}${ext}`;

        const args = ["-h", host, "-p", String(port), "-U", user, "-Fc", database];
        const env = { ...process.env };
        if (password) {
            env.PGPASSWORD = password;
        }

        const child = spawn(pgDumpBin, args, { env });

        const files = [];
        let partIndex = 0;
        let currentStream = null;
        let currentBytes = 0;
        let totalBytes = 0;
        let stderrOutput = "";
        let settled = false;

        function openNextPart() {
            const fileName = `${baseName}${String(partIndex).padStart(3, "0")}`;
            const filePath = path.join(outputDir, fileName);
            files.push(filePath);
            currentStream = fs.createWriteStream(filePath);
            currentBytes = 0;
            partIndex += 1;
        }

        openNextPart();

        child.stdout.on("data", (chunk) => {
            let offset = 0;
            while (offset < chunk.length) {
                if (currentBytes >= splitSizeBytes) {
                    currentStream.end();
                    openNextPart();
                }
                const remaining = splitSizeBytes - currentBytes;
                const writeLen = Math.min(remaining, chunk.length - offset);
                currentStream.write(chunk.subarray(offset, offset + writeLen));
                currentBytes += writeLen;
                totalBytes += writeLen;
                offset += writeLen;
            }
        });

        child.stderr.on("data", (chunk) => {
            stderrOutput += chunk.toString("utf8");
        });

        child.on("error", (err) => {
            if (settled) return;
            settled = true;
            if (currentStream) currentStream.end();
            reject(new Error(`pg_dump起動失敗: ${err.message}`));
        });

        child.on("close", (code) => {
            if (settled) return;

            const finalize = () => {
                settled = true;
                if (code !== 0) {
                    reject(new Error(`pg_dump異常終了 (code=${code}): ${stderrOutput.trim()}`));
                    return;
                }
                resolve({ files, totalBytes, stderrOutput: stderrOutput.trim() });
            };

            if (currentStream && !currentStream.destroyed) {
                currentStream.end(finalize);
            } else {
                finalize();
            }
        });
    });
}

function formatDateFolderName(date = new Date()) {
    return `${date.getFullYear()}${pad2(date.getMonth() + 1)}${pad2(date.getDate())}`;
}

module.exports = { runPgDump, formatTimestamp, formatDateFolderName };