'use strict';
const { promisify } = require('util');
const fs = require('fs');
const path = require('path');
const fastGlob = require('fast-glob');
const gitIgnore = require('ignore');
const slash = require('slash');

const DEFAULT_IGNORE = [
  '**/node_modules/**',
  '**/flow-typed/**',
  '**/coverage/**',
  '**/.git',
];

const readFileP = promisify(fs.readFile);

const mapGitIgnorePatternTo = (base) => (ignore) => {
  if (ignore.startsWith('!')) {
    return '!' + path.posix.join(base, ignore.slice(1));
  }

  return path.posix.join(base, ignore);
};

const parseGitIgnore = (content, options) => {
  const base = slash(
    path.relative(options.cwd, path.dirname(options.fileName))
  );

  return content
    .split(/\r?\n/)
    .filter(Boolean)
    .filter((line) => !line.startsWith('#'))
    .map(mapGitIgnorePatternTo(base));
};

const reduceIgnore = (files) => {
  const ignores = gitIgnore();
  for (const file of files) {
    ignores.add(
      parseGitIgnore(file.content, {
        cwd: file.cwd,
        fileName: file.filePath,
      })
    );
  }

  return ignores;
};

const ensureAbsolutePathForCwd = (cwd, p) => {
  cwd = slash(cwd);
  if (path.isAbsolute(p)) {
    if (slash(p).startsWith(cwd)) {
      return p;
    }

    throw new Error(`Path ${p} is not in cwd ${cwd}`);
  }

  return path.join(cwd, p);
};

const getIsIgnoredPredecate = (ignores, cwd) => {
  return (p) =>
    ignores.ignores(
      slash(path.relative(cwd, ensureAbsolutePathForCwd(cwd, p.path || p)))
    );
};

const getFile = async (file, cwd) => {
  const filePath = path.join(cwd, file);
  const content = await readFileP(filePath, 'utf8');

  return {
    cwd,
    filePath,
    content,
  };
};

const getFileSync = (file, cwd) => {
  const filePath = path.join(cwd, file);
  const content = fs.readFileSync(filePath, 'utf8');

  return {
    cwd,
    filePath,
    content,
  };
};

const normalizeOptions = ({ ignore = [], cwd = slash(process.cwd()) } = {}) => {
  return { ignore, cwd };
};

module.exports = async (options) => {
  options = normalizeOptions(options);

  const paths = await fastGlob('**/.gitignore', {
    ignore: DEFAULT_IGNORE.concat(options.ignore),
    cwd: options.cwd,
  });

  const files = await Promise.all(
    paths.map((file) => getFile(file, options.cwd))
  );
  const ignores = reduceIgnore(files);

  return getIsIgnoredPredecate(ignores, options.cwd);
};

module.exports.sync = (options) => {
  options = normalizeOptions(options);

  const paths = fastGlob.sync('**/.gitignore', {
    ignore: DEFAULT_IGNORE.concat(options.ignore),
    cwd: options.cwd,
  });

  const files = paths.map((file) => getFileSync(file, options.cwd));
  const ignores = reduceIgnore(files);

  return getIsIgnoredPredecate(ignores, options.cwd);
};