#!/usr/bin/env node
const {open, readdir, stat, rmdir} = require('node:fs/promises');
const {join} = require('node:path');
const {unlink} = require('node:fs/promises');
const {Buffer} = require('node:buffer');


const Kilobyte = 1024;
const Megabyte = Kilobyte * 1024;
const Gigabyte = Megabyte * 1024;

const BLOCK_SIZE = 16 * Megabyte;

const locale = 'en-US';

/** @type {Buffer} */
const BufferA = Buffer.alloc(BLOCK_SIZE);
/** @type {Buffer} */
const BufferB = Buffer.alloc(BLOCK_SIZE);


const Terminal = Object.freeze({
  fg: {
    red: (text) => `\u001b[31m${text}\u001b[0m`,
    green: (text) => `\u001b[32m${text}\u001b[0m`,
    yellow: (text) => `\u001b[33m${text}\u001b[0m`,
    blue: (text) => `\u001b[34m${text}\u001b[0m`,
  }
});

/**
 * @typedef {{bySize: {[key: string]: string[]}}} Cache
 */

/**
 * @param {function(typeof Terminal)|string} param
 */
function log(param) {
  console.log(typeof param === 'string' ? param : param(Terminal))
}

/**
 * @param {Number} size
 * @returns {*}
 */
function formatSize(size) {
  let suffix = '';
  let digits = 0;
  if (size >= Megabyte) {
    digits = 1;
    if (size >= Gigabyte) {
      size /= Gigabyte;
      suffix = ' G';
    } else {
      size /= Megabyte;
      suffix = ' M';
    }
  } else if (size >= Kilobyte) {
    digits = 1;
    size /= Kilobyte;
    suffix = ' K'
  }
  return `${size.toLocaleString(locale, {
    minimumFractionDigits: digits,
    maximumFractionDigits: digits,
    useGrouping: false
  })}${suffix}`
}

/**
 * @param path
 * @returns {Promise<{files: Dirent[], dirs: Dirent[]}>}
 */
async function dirEntries(path) {
  return (await readdir(path, {withFileTypes: true}))
    .reduce((acc, file) => {
      (file.isDirectory() ? acc.dirs : acc.files).push(file)
      return acc;
    }, {files: [], dirs: []})
}

async function compareFiles(localPath, remotePath, size) {
  const localFile = await open(localPath),
    remoteFile = await open(remotePath);
  try {
    for (let i = 0; ;) {
      const start = process.hrtime.bigint();
      const a = await localFile.read(BufferA, 0, BLOCK_SIZE);
      const b = await remoteFile.read(BufferB, 0, BLOCK_SIZE);

      if (a.bytesRead !== b.bytesRead || BufferA.compare(BufferB) !== 0) {
        log(f => f.fg.yellow(`  files are different`));
        console.log();
        return false;
      }
      if (a.bytesRead === 0) {
        console.log();
        return true;
      }
      const seconds = Number(process.hrtime.bigint() - start) / 1_000_000_000;
      i += a.bytesRead;
      process.stdout.write(`\r${(i * 100 / size).toLocaleString(locale, {
        minimumFractionDigits: 2,
        maximumFractionDigits: 2
      })}% ${formatSize((a.bytesRead + b.bytesRead) / seconds)}Bytes/sec`)
    }
    console.log('')

  } finally {
    Promise.allSettled([localFile.close(), remoteFile.close()]);
  }
}

/**
 * @param local
 * @param {Cache} cache
 * @param options
 * @returns {Promise<boolean>}
 */
async function compareDirs(local, cache, options) {
  try {
    let canRemoveDir = true;
    const entries = await dirEntries(local)
    loop: for (const file of entries.files) {
      const localPath = join(local, file.name);
      const localStat = await stat(localPath);

      const sameSize = cache.bySize[localStat.size];
      if (!sameSize) {
        canRemoveDir = false;
        continue;
      }

      log(f => `${f.fg.green(localPath)} (${f.fg.green(`${formatSize(localStat.size)}B`)})`)
      for (let i = 0; i < sameSize.length; i++) {
        const remotePath = sameSize[i];
        const remoteStat = await stat(remotePath);


        if (localStat.ino === remoteStat.ino) {
          log(f => f.fg.red('This is the same file'));
        } else {
          log(f => `Comparing with ${f.fg.blue(remotePath)}`)
          if (await compareFiles(localPath, remotePath, localStat.size)) {
            if (options.delete) {
              log(f => `  ${f.fg.red('files are the same - deleting')}`);
              await unlink(localPath)
            }
            continue loop;
          }
        }
      }
      canRemoveDir = false;
    }
    for (const dir of entries.dirs) {
      if (!await compareDirs(join(local, dir.name), cache, options)) canRemoveDir = false;
    }
    if (canRemoveDir && options.delete) {
      log(f => `Directory ${f.fg.yellow(local)} is empty, removed`)
      await rmdir(local)
    }
    return canRemoveDir;
  } catch (err) {
    console.error(err);
    return false;
  }
}

const options = {
  delete: false
};

if (process.argv[3] === 'delete') {
  options.delete = true;
}

/**
 * @param path
 * @param result
 * @returns {Promise<Cache>}
 */
async function scanDir(path, result) {
  const entries = await dirEntries(path)
  for (const file of entries.files) {
    let absPath = join(path, file.name);
    let {size} = (await stat(absPath));
    let bySize = result.bySize[size];
    if (bySize) {
      bySize.push(absPath);
    } else {
      bySize = [absPath];
      result.bySize[size] = bySize;
    }
  }
  for (const dir of entries.dirs) {
    await scanDir(join(path, dir.name), result)
  }
  return result;
}

(async function () {
  log('Scanning target directory...')
  const scan = await scanDir(process.argv[2], {bySize: {}})
  log('Comparing...')
  await compareDirs(process.cwd(), scan, options);
})();