var ini = require('ini');
var glob = require('glob');
var path = require('path');
var fs = require('fs');

// Constants
var ICON_REALPATH_REGEX = /\..+$/;

exports.loadAllDesktopFiles = function(rootDirs) {

  return exports.findAllDesktopFiles(rootDirs)
    .then(function(filePaths) {

      var promises = filePaths.map(function(path) {
        return exports.loadDesktopFile(path);
      });

      return Promise.all(promises)
        .then(function(contents) {
          return contents.map(function(content, i) {
            return { content: content, path: filePaths[i] };
          });
        })
      ;

    })
  ;

};

exports.findAllDesktopFiles = function(rootDirs) {

  if(!Array.isArray(rootDirs)) {
    rootDirs = [rootDirs];
  }

  var promises = rootDirs.map(function(rootDir) {

    var globPath = path.join(rootDir, '**/*.desktop');

    return new Promise(function(resolve, reject) {
      glob(globPath, function(err, files) {
        if(err) return reject(err);
        return resolve(files);
      });
    });

  });

  return Promise.all(promises)
    .then(function(apps) {
      return uniq(flatten(apps));
    })
  ;

};

exports.loadDesktopFile = function(filePath) {
  return new Promise(function(resolve, reject) {
    fs.readFile(filePath, 'utf8', function(err, content) {
      if(err) return reject(err);
      try {
        var decoded = ini.decode(content);
        return resolve(decoded);
      } catch(err) {
        return reject(err);
      }
    });
  });
};

exports.findIcon = function(iconPath) {
  return new Promise(function(resolve, reject) {
    if( ICON_REALPATH_REGEX.test(iconPath) ) {
      return resolve(iconPath);
    }
  });
};

// Array helpers

function flatten(arr) {
  return arr.reduce(function(result, item) {
    result = result.concat.apply(result, Array.isArray(item) ? flatten(item) : [item]);
    return result;
  }, []);
}

function uniq(arr) {
  return arr.reduce(function(result, item) {
    if(result.indexOf(item) === -1) {
      result.push(item);
    }
    return result;
  }, []);
}