const fse = require('fs-extra');
const path = require('path');
const generateInfo = require('./generate-info');

/**
 * Read the symbols from info file.
 * @return {Promise<Array>} Resolves with an array of symbol objects.
 */
async function getSymbols() {
  const info = await generateInfo();
  return info.symbols.filter((symbol) => symbol.kind != 'member');
}

/**
 * Generate an import statement.
 * @param {Object} symbol Symbol.
 * @param {string} member Member.
 * @return {string} An import statement.
 */
function getImport(symbol, member) {
  const defaultExport = symbol.name.split('~');
  const namedExport = symbol.name.split('.');
  if (defaultExport.length > 1) {
    const from = defaultExport[0].replace(/^module\:/, './');
    const importName = from.replace(/[.\/]+/g, '$');
    return `import ${importName} from '${from}';`;
  } else if (namedExport.length > 1 && member) {
    const from = namedExport[0].replace(/^module\:/, './');
    const importName = from.replace(/[.\/]+/g, '_');
    return `import {${member} as ${importName}$${member}} from '${from}';`;
  }
}

/**
 * Generate code to export a named symbol.
 * @param {Object} symbol Symbol.
 * @param {Object<string, string>} namespaces Already defined namespaces.
 * @param {Object} imports Imports.
 * @return {string} Export code.
 */
function formatSymbolExport(symbol, namespaces, imports) {
  const name = symbol.name;
  const parts = name.split('~');
  const isNamed = parts[0].indexOf('.') !== -1;
  const nsParts = parts[0].replace(/^module\:/, '').split(/[\/\.]/);
  const last = nsParts.length - 1;
  const importName = isNamed
    ? '_' + nsParts.slice(0, last).join('_') + '$' + nsParts[last]
    : '$' + nsParts.join('$');
  let line = nsParts[0];
  for (let i = 1, ii = nsParts.length; i < ii; ++i) {
    line += `.${nsParts[i]}`;
    namespaces[line] =
      (line in namespaces ? namespaces[line] : true) && i < ii - 1;
  }
  line += ` = ${importName};`;
  imports[getImport(symbol, nsParts.pop())] = true;
  return line;
}

/**
 * Generate export code given a list symbol names.
 * @param {Array<Object>} symbols List of symbols.
 * @param {Object<string, string>} namespaces Already defined namespaces.
 * @param {Array<string>} imports List of all imports.
 * @return {string} Export code.
 */
function generateExports(symbols) {
  const namespaces = {};
  const imports = [];
  let blocks = [];
  symbols.forEach(function (symbol) {
    const name = symbol.name;
    if (name.indexOf('#') == -1) {
      const imp = getImport(symbol);
      if (imp) {
        imports[getImport(symbol)] = true;
      }
      const block = formatSymbolExport(symbol, namespaces, imports);
      if (block !== blocks[blocks.length - 1]) {
        blocks.push(block);
      }
    }
  });
  const nsdefs = [];
  const ns = Object.keys(namespaces).sort();
  for (let i = 0, ii = ns.length; i < ii; ++i) {
    if (namespaces[ns[i]]) {
      nsdefs.push(`${ns[i]} = {};`);
    }
  }
  blocks = Object.keys(imports)
    .concat('\nvar ol = {};\n', nsdefs.sort())
    .concat(blocks.sort());
  blocks.push('', 'export default ol;');
  return blocks.join('\n');
}

/**
 * Generate the exports code.
 * @return {Promise<string>} Resolves with the exports code.
 */
async function main() {
  const symbols = await getSymbols();
  return generateExports(symbols);
}

/**
 * If running this module directly, read the config file, call the main
 * function, and write the output file.
 */
if (require.main === module) {
  main()
    .then(async (code) => {
      const filepath = path.join(__dirname, '..', 'build', 'index.js');
      await fse.outputFile(filepath, code);
    })
    .catch((err) => {
      process.stderr.write(`${err.message}\n`, () => process.exit(1));
    });
}

/**
 * Export main function.
 */
module.exports = main;