#!/usr/bin/env node

let
  app,
  json = require('../src/apps.json');

for (app in json.apps) {
  ['headers', 'html', 'env', 'meta', 'script'].forEach((type) => {
    let
      key,
      patterns = json.apps[app][type];

    if (patterns !== undefined) {
      patterns = typeof patterns === 'string' ? [patterns] : patterns;

      if (!(patterns instanceof Array)) {
        patterns = [];

        for (key in json.apps[app][type]) {
          patterns.push(json.apps[app][type][key]);
        }
      }

      patterns.forEach((pattern) => {
        let
          attrs = pattern.split('\\;'),
          regex = `/${attrs.shift().replace('/', '\/')}/`,
          version = attrs.find(attr => attr.indexOf('version:') === 0),
          amountOfCaptureGroups,
          captureGroupsNeeded,
          amountOfCaptureGroupsNeeded,
          highestBackReference;

        // Check if the pattern is a valid RegExp
        // Note: unlike when used in Wappalyzer, the modifier i isn't added here
        new RegExp(regex);

        // Actual amount of capture groups
        amountOfCaptureGroups = ''.match(new RegExp(`(?:${pattern})?`)).length - 1;

        // Capture groups of which the result is used
        captureGroupsNeeded = version ? (version.match(/\\\d/g) || []).filter((value, index, self) => self.indexOf(value) === index).map(value => parseInt(value.charAt(1), 10), // Will only work if backreferences cannot be any longer than a single digit
        ) : [];

        // Amount of capture groups needed
        amountOfCaptureGroupsNeeded = captureGroupsNeeded.length;

        // Highest back reference number used
        highestBackReference = Math.max.apply(null, captureGroupsNeeded);

        // Report error
        if (amountOfCaptureGroups > amountOfCaptureGroupsNeeded) {
          throw new Error(`The pattern uses more capture groups than needed. Use non-capturing groups where appropriate.\n${app}: ${type}: ${pattern}`);
        } else if (amountOfCaptureGroups < amountOfCaptureGroupsNeeded) {
          throw new Error(`The version string references more capture groups than there are in the pattern! Remove any incorrect back references from the version string and/or add the missing capture groups to the pattern.\n${app}: ${type}: ${pattern}`);
        } else if (highestBackReference > amountOfCaptureGroups) {
          throw new Error(`The version string references one or more capture groups whose index is higher than the amount of capture groups in the pattern. Please use the correct index instead of \\\\${highestBackReference}.\n${app}: ${type}: ${pattern}`);
        }

        if (/^\/(?:\^\$|\.\+|\.\*)\/$/.test(regex)) {
          throw new Error(`Pattern should be replaced with empty string.\n${app}: ${type}: ${pattern}`);
        }

        if (type === 'html') {
          if (/\.(?:\+|\*)/.test(regex)) {
            throw new Error(`Avoid ".+" and ".*" in HTML patterns. Consider using "[^>]+" or "[^<]+" instead.\n${app}: ${type}: ${pattern}`);
          }

          if (!/[<>]/.test(regex)) {
            throw new Error(`HTML patterns must contain "<" or ">".\n${app}: ${type}: ${pattern}`);
          }
        }

        // Warn about suspicious periods (".") in patterns which should probably have been escaped
        //	Periods inside character classes (such as [\d.]) don't count as wildcard, so we'll replace
        //	the character classes in the pattern with "_". (We could remove them entirely, but then
        //  we'd have to deal with leftover * and + characters; for example, removing the character
        //  class entirely from the pattern /test.[a-z]+/ would yield the pattern /test.+/, which
        //  would mean not detecting the un-escaped ".". Replacing the character class with an
        //	underscore instead gives /test._+/, which WOULD yield a warning about the unescaped ".".)
        if (/(?:^\/|[^\\])\.(?:[^*+]|\/$)/.test(regex.replace(/([^\\]|^)\[[^\]]+\]/g, '$1_'))) {
          console.warn(`Suspicious period (".") in pattern. Should this have been escaped?\n\tApp: ${app}\n\tPattern: ${type}: ${pattern}`);
        }
      });
    }
  });

  if (!/^https?:\/\//i.test(json.apps[app].website)) {
    throw new Error(`Invalid website URL\n${app}: ${json.apps[app].website}`);
  }
}