'use strict';

const fs = require('fs');

const copyWithProgress = async ({ source, destination, jobLog, updateProgress, label }) => {
  const sourceSize = fs.statSync(source).size;
  const sourceSizeMb = (sourceSize / 1024 / 1024).toFixed(1);
  const startMs = Date.now();
  let copiedBytes = 0;
  let nextProgressPercent = 0;

  const report = (percent, message) => {
    const boundedPercent = Math.min(Math.max(percent, 0), 100);
    if (typeof updateProgress === 'function') {
      updateProgress({
        progress: boundedPercent,
        jobLog: message,
      });
    }
    if (typeof jobLog === 'function') jobLog(`${message}\n`);
  };

  await new Promise((resolve, reject) => {
    const rd = fs.createReadStream(source);
    const wr = fs.createWriteStream(destination);
    let settled = false;
    const fail = (error) => {
      if (settled) return;
      settled = true;
      rd.destroy();
      wr.destroy();
      reject(error);
    };

    rd.on('error', fail);
    wr.on('error', fail);
    wr.on('finish', () => {
      if (settled) return;
      settled = true;
      resolve();
    });
    rd.on('data', (chunk) => {
      copiedBytes += chunk.length;
      const percent = sourceSize === 0 ? 100 : Math.floor((copiedBytes / sourceSize) * 100);
      if (percent < nextProgressPercent) return;

      const elapsedSeconds = Math.max((Date.now() - startMs) / 1000, 0.1);
      const copiedMb = (copiedBytes / 1024 / 1024).toFixed(1);
      const speedMbPerSecond = (copiedBytes / 1024 / 1024 / elapsedSeconds).toFixed(1);
      report(
        percent,
        `[${label}] Progress: ${Math.min(percent, 100)}% `
          + `(${copiedMb}/${sourceSizeMb} MB, ${speedMbPerSecond} MB/s)`,
      );
      nextProgressPercent = (Math.floor(percent / 10) + 1) * 10;
    });
    rd.pipe(wr);
  });

  const destinationSize = fs.statSync(destination).size;
  if (destinationSize !== sourceSize) {
    throw new Error(
      `[${label}] Copy size mismatch: expected ${sourceSize} bytes, got ${destinationSize}`,
    );
  }

  const elapsed = ((Date.now() - startMs) / 1000).toFixed(1);
  report(100, `[${label}] Done: ${sourceSizeMb} MB copied in ${elapsed}s`);
};

module.exports = { copyWithProgress };