POT/PO -> JSON i18n process

[MattiJarvinen]

Since Transloco insists on creating POT (portable object template) per language (this is actually very redundant one template is enough) or these should be named as PO. I have changed to producing only one named C.pot

We use POEdit to create the translation files ( .po ) for this allows i18n memory etc. goodies. Translators get the POT & PO files. They can use the POEdit to update their own language's .po file from the C.pot as described in https://maniacx.github.io/Airpod-Battery-Monitor/poedit-guide getting the new keys.

We then convert the PO-files gathered from the translator to the JSON format in build step and prestart / manually if needed. The script places the JSON file in the similar folder structure into the target folder as is found in the souce PO folders.

I decided to use gettext-parser for the job since it's readily available and it's somewhat easy to understand.

import { readFileSync, writeFileSync, readdirSync, existsSync, mkdirSync, lstatSync } from 'fs';
import { join, parse } from 'path';
import { po } from 'gettext-parser';

/**
 * Converts a PO file to a JSON file in the format expected by Transloco
 * @param poFilePath Path to the PO file
 * @param outputDir Directory where the JSON file will be saved
 */
const convertPoToJson = (poFilePath: string, outputDir: string): void => {
  try {
    // Read and parse the PO file
    const poContent = readFileSync(poFilePath, 'utf-8');
    const parsedPo = po.parse(poContent, {defaultCharset: 'utf-8'});

    // Transform translations to the format expected by Transloco
    const translations: Record<string, string> = {};

    for (const [key, value] of Object.entries(parsedPo.translations[''])) {
      if (key === '') continue; // Skip the header
      translations[key] = value.msgstr[0] ?? '';
    }

    // Create output directory if it doesn't exist
    if (!existsSync(outputDir)) {
      mkdirSync(outputDir, { recursive: true });
    }

    // Determine the output filename based on the PO file's language code
    const { name } = parse(poFilePath);
    const langCode = name.split('.')[0]; // Assumes format: en.po, fi.po, etc.
    const outputPath = join(outputDir, `${langCode}.json`);

    // Write the JSON file
    writeFileSync(outputPath, JSON.stringify(translations, null, 2), 'utf-8');
    console.log(`Converted ${poFilePath} -> ${outputPath}`);

  } catch (error) {
    console.error(`Error processing ${poFilePath}:`, error);
    process.exit(1);
  }
}

/**
 * Processes all PO files in a directory
 * @param inputDir Directory containing PO files
 * @param outputDir Directory where JSON files will be saved
 */
const processPoFiles = (inputDir: string, outputDir: string): void => {
  try {
    if (!existsSync(inputDir)) {
      throw new Error(`Input directory does not exist: ${inputDir}`);
    }

    const files = readdirSync(inputDir);

    const dirs = files.filter(file => lstatSync(join(inputDir, file)).isDirectory());

    for( const dir of dirs ) {
      processPoFiles(join(inputDir, dir), join(outputDir, dir));
    }

    const poFiles = files.filter(file =>
      file.endsWith('.po') && lstatSync(join(inputDir, file)).isFile()
    );

    if (poFiles.length === 0) {
      console.warn(`No PO files found in ${inputDir}`);
      return;
    }

    for (const file of poFiles) {
      const filePath = join(inputDir, file);
      convertPoToJson(filePath, outputDir);
    }

    console.log('PO to JSON conversion completed successfully!');
  } catch (error) {
    console.error('Error processing PO files:', error);
    process.exit(1);
  }
}

// Main execution
if (process.argv.length < 4) {
  console.log('Usage: tsx po2json.ts <input-dir> <output-dir>');
  console.log('Example: tsx po2json.ts ./locales/po ./src/assets/i18n');
  process.exit(1);
}

const inputDir = process.argv[2];
const outputDir = process.argv[3];

processPoFiles(inputDir, outputDir);