<?php
class Index
{
    private $tweets;
    private $categories;
    private $users;
    private $inverted;
    private $files_map;

    //file names holding the json-encoded data
    public static $indexed_inverted = 'indexed_inverted';
    public static $indexed_tweets = 'indexed_tweets';
    public static $indexed_categories = 'indexed_categories';
    public static $indexed_users = 'indexed_users';

    function Index()
    {
        $this->files_map = array(Index::$indexed_inverted   => &$this->inverted,
                                 Index::$indexed_tweets     => &$this->tweets,
                                 Index::$indexed_categories => &$this->categories,
                                 Index::$indexed_users      => &$this->users);
    }

    function assignIndices($indices_to_fetch)
    {
        //data validation
        if(!is_array($indices_to_fetch))
        {
            throw new Excepton('$indices_to_fetch needs to be an array');
        }

        foreach($indices_to_fetch as $file_name)
        {
            if(!array_key_exists($file_name, $this->files_map))
            {
                throw new Exception('Key ' . $file_name . ' doesn\t exist in files_map');
            }
            $file_path = 'data/'.$file_name.'.txt';

            //pre existing data.. exists
            if(file_exists($file_path))
            {
                $file_contents = file_get_contents($file_path);
                $this->files_map[$file_name] = (array) json_decode($file_contents);
            }
        }
    }

    function buildIndex($num)
    {
        $read_handle = fopen('data/raw_tweets.txt.'.$num.'', 'r');
        $count = 0;
        while(!feof($read_handle))
        {
            //divide the tweet into an array, an index will exist per n+1 commas
            $current_tweet_array = explode(',', fgets($read_handle));

            //lets me know there's progress.. rather than watching an idle console screen
            if($count % 500 == 0)
                echo "reached $count\n";

            //get rid of follower data
            array_pop($current_tweet_array);
            array_pop($current_tweet_array);

            $user_name = strtolower(array_pop($current_tweet_array));

            //get rid of timestamp
            array_shift($current_tweet_array);

            //put the tweet back together, incase the actual message contained commas
            $tweet = implode(",", $current_tweet_array);

            //undo the html special characters which appear quite often
            $tweet = htmlspecialchars_decode($tweet);

            //the current tweet's id is the previous tweets position in the array
            $tweet_id = count($this->tweets);

            //attribute the tweet to the author
            if(!isset($this->users[$user_name]))
            {
                $this->users[$user_name] = array();
            }
            $this->users[$user_name][] = $tweet_id;

            //index only the words from the tweet.
            $clean_tweet =  preg_replace('/[^a-zA-Z0-9@&#_\s]/', ' ', $tweet);
            $tweet = $this->tokenizeLine($clean_tweet, $tweet_id, $tweet);
            $tweet = str_replace($user_name, '<a href = "/index.php?query='.$user_name.'&type=u">'. $user_name .'</a>', ($user_name . '%' . $tweet));
            $this->tweets[] = $tweet;
            $count++;
        }
        $this->writeToFile(array_keys($this->files_map));
    }

    private function tokenizeLine($clean_tweet, $tweet_id, $tweet)
    {
        $token = strtok($clean_tweet, " ");
        $words_in_place = array();
        while($token !== false)
        {
            $words_in_place[$token] = 1;
            //replace the category with a link to the categories
            if($token[0] == '#')
            {
                $token_display = $token;
                $token = substr($token, 1);
                $tweet = str_replace($token_display, '<a href = "/index.php?query='.$token.'&type=c">'. $token_display .'</a>', $tweet);
                if(!isset($this->categories[$token]))
                    $this->categories[$token] = array();
                $this->categories[$token][] = $tweet_id;
            }

            //don't bother indexing usernames with the general terms, but make it clickable
            if($token[0] == '@')
            {
                $token_display = $token;
                $token = substr($token, 1);
                $tweet = str_replace($token_display, '<a href = "/index.php?query='.$token.'&type=u">'. $token_display .'</a>', $tweet);
                $token = strtok(' ');
                continue;
            }

            //index the token after putting it to lower case, this ensures, that case-conflicts don't emerge when fetching said token
            $token = strtolower($token);
            if(!isset($this->inverted[$token]))
            {
                $this->inverted[$token] = array();
            }

            if(!isset($words_in_place[$token]))
            {
                $this->inverted[$token][] = $tweet_id;
            }
            $token = strtok(' ');
        }
        return $tweet;
    }

    private function writeToFile($file_name_array)
    {
        if(is_array($file_name_array))
        {
            foreach($file_name_array as $file_name)
            {
                //write our indexed data to file in json format
                $file_path = 'data/'.$file_name.'.txt';
                unlink($file_path);
                $write_handle = fopen($file_path, 'w');
                fwrite($write_handle, json_encode($this->files_map[$file_name]));
                fclose($write_handle);
            }
        }
    }
}
?>