import fs from "fs";
import path from "path";
import os from "os";
import util from "util";
import crypto from "crypto";
import { exec } from "child_process";
import { SyncFoldersSyncFnParams } from "../types";
import grabDirNames from "./grab-dir-names";
import { fldFileToStr } from "./grab-folders-files-string-paths";
import delay from "./delay";

const execPromise = util.promisify(exec);

const LOCK_STALE_MS = 5 * 60 * 1000;
const LOCK_RETRY_MS = 100;

function lockPathFor(dirPath: string) {
    const hash = crypto
        .createHash("sha1")
        .update(path.resolve(dirPath))
        .digest("hex")
        .slice(0, 16);

    return path.join(os.tmpdir(), `turbosync-${hash}.lock`);
}

async function acquireLock(lockPath: string) {
    while (true) {
        try {
            const fd = fs.openSync(lockPath, "wx");
            fs.writeFileSync(fd, String(process.pid));
            fs.closeSync(fd);
            return;
        } catch (error: any) {
            if (error.code !== "EEXIST") throw error;

            try {
                const { mtimeMs } = fs.statSync(lockPath);
                if (Date.now() - mtimeMs > LOCK_STALE_MS) {
                    fs.unlinkSync(lockPath);
                    continue;
                }
            } catch {
                continue;
            }

            await delay(LOCK_RETRY_MS);
        }
    }
}

async function acquireLocks(lockPaths: string[]) {
    for (const lockPath of lockPaths) {
        await acquireLock(lockPath);
    }
}

function releaseLocks(lockPaths: string[]) {
    for (const lockPath of lockPaths) {
        try {
            fs.unlinkSync(lockPath);
        } catch {}
    }
}

export default async function sync({
    options,
    dirs,
    dirPath,
    isFiles,
    firstRun,
}: SyncFoldersSyncFnParams) {
    const dstDirs = dirs.filter((dr) => {
        if (typeof dr == "string") return dr !== dirPath;
        if (dr?.path) return dr.path !== dirPath;
        return false;
    });

    const { ignoreFileName } = grabDirNames();

    const rsyncIgnoreFile = path.join(dirPath, ignoreFileName);

    const rsyncTrailingSlash = isFiles ? "" : "/";

    const allCommandsArr: string[][] = [];

    for (let j = 0; j < dstDirs.length; j++) {
        const dstDr = dstDirs[j];

        let cmdArray = ["rsync", firstRun ? "-az" : "-azu", "--inplace"];

        if (options?.delete) {
            cmdArray.push("--delete");
        }

        if (options?.include?.[0]) {
            options.include.forEach((incl) => {
                cmdArray.push(`--include='${incl}'`);
            });
        }

        if (fs.existsSync(rsyncIgnoreFile)) {
            cmdArray.push(`--exclude-from=${rsyncIgnoreFile}`);
        }

        if (options?.exclude?.[0]) {
            options.exclude.forEach((excl) => {
                cmdArray.push(`--exclude='${excl}'`);
            });
        }

        if (typeof dstDr == "string") {
            if (!fs.existsSync(dstDr)) continue;

            if (dirPath === dstDr) {
                console.log(
                    `You can't sync the same paths. Please check your configuration and resolve duplicate paths`
                );
                process.exit(6);
            }

            cmdArray.push(
                path.normalize(dirPath) + rsyncTrailingSlash,
                path.normalize(dstDr) + rsyncTrailingSlash
            );
        } else if (dstDr.path) {
            if (!dstDr.host && !fs.existsSync(dstDr.path)) continue;

            if (dirPath === dstDr.path) {
                console.log(
                    `You can't sync the same paths. Please check your configuration and resolve duplicate paths`
                );
                process.exit(6);
            }

            if (dstDr.host && dstDr.ssh_key && dstDr.user) {
                cmdArray.push("-e", `'ssh -i ${dstDr.ssh_key}'`);
                cmdArray.push(
                    path.normalize(dirPath) + rsyncTrailingSlash,
                    `${dstDr.user}@${dstDr.host}:${dstDr.path}${rsyncTrailingSlash}`
                );
            } else {
                cmdArray.push(
                    path.normalize(dirPath),
                    path.normalize(dstDr.path)
                );
            }
        }

        allCommandsArr.push(cmdArray);
    }

    const lockPaths = [dirPath, ...dstDirs.map((dr) => fldFileToStr(dr))]
        .filter((pth): pth is string => Boolean(pth))
        .map((pth) => lockPathFor(pth))
        .sort();

    await acquireLocks(lockPaths);

    try {
        await Promise.all(
            allCommandsArr.map((cmdArr) => {
                return execPromise(cmdArr.join(" "));
            })
        );
    } finally {
        releaseLocks(lockPaths);
    }

    console.log(`${dirPath} Folder Sync Complete. Exiting ...`);
}