<?php
// {{{ICINGA_LICENSE_HEADER}}}
// {{{ICINGA_LICENSE_HEADER}}}

namespace Icinga\Protocol\File;

use Icinga\Data\DatasourceInterface;

/**
 * Class Reader
 *
 * Read file line by line
 *
 * @package Icinga\Protocol\File
 */
class Reader implements DatasourceInterface
{
    /**
     * Name of the file to read
     *
     * @var string
     */
    private $filename;

    /**
     * Configuration for this Datasource
     *
     * @var \Zend_Config
     */
    private $config;

    /**
     * @param \Zend_Config $config
     */
    public function __construct($config)
    {
        $this->config = $config;
        $this->filename = $config->filename;
    }

    /**
     * Instantiate a Query object
     *
     * @return Query
     */
    public function select()
    {
        return new Query($this);
    }

    /**
     * Fetch result as an array of objects
     *
     * @return array
     */
    public function fetchAll(Query $query)
    {
        $all = array();
        foreach ($this->fetchPairs($query) as $index => $value) {
            $all[$index] = new \stdClass();
            foreach ($value as $key => $value_2) {
                $all[$index]->{$key} = $value_2;
            }
        }
        return $all;
    }

    /**
     * Fetch first result row
     *
     * @return object
     */
    public function fetchRow(Query $query)
    {
        $all = $this->fetchAll($query);
        if (isset($all[0])) {
            return $all[0];
        }
        return null;
    }

    /**
     * Fetch first result column
     *
     * @return array
     */
    public function fetchColumn(Query $query)
    {
        $column = array();
        foreach ($this->fetchPairs($query) as $value) {
            foreach ($value as $value_2) {
                $column[] = $value_2;
                break;
            }
        }
        return $column;
    }

    /**
     * Fetch first column value from first result row
     *
     * @return mixed
     */
    public function fetchOne(Query $query)
    {
        $pairs = $this->fetchPairs($query);
        if (isset($pairs[0])) {
            foreach ($pairs[0] as $value) {
                return $value;
            }
        }
        return null;
    }

    /**
     * Fetch result as a key/value pair array
     *
     * @return array
     */
    public function fetchPairs(Query $query)
    {
        return $this->read($query);
    }

    /**
     * If given $line matches the $query's PCRE pattern and contains all the strings in the $query's filters array,
     * return an associative array of the matches of the PCRE pattern.
     * Otherwise, return false.
     * If preg_match returns false, it failed parsing the PCRE pattern.
     * In that case, throw an exception.
     *
     * @param string $line
     * @param Query $query
     *
     * @return array|bool
     *
     * @throws \Exception
     */
    public function validateLine($line, Query $query)
    {
        $data = array();
        $PCRE_result = @preg_match($this->config->fields, $line, $data);
        if ($PCRE_result === false) {
            throw new \Exception('Failed parsing regular expression!');
        } else if ($PCRE_result === 1) {
            foreach ($query->getFilters() as $filter) {
                if (strpos($line, $filter) === false) {
                    return false;
                }
            }
            foreach ($data as $key => $value) {
                if (is_int($key)) {
                    unset($data[$key]);
                }
            }
            return $data;
        }
        return false;
    }

    /**
     * Skip and read as many lines as needed according to given $query.
     *
     * @param Query $query
     *
     * @return array  result
     */
    public function read(Query $query)
    {
        $skip_lines = $query->getOffset();
        $read_lines = $query->getLimit();
        if ($skip_lines === null) {
            $skip_lines = 0;
        }
        return $this->{$query->sortDesc() ? 'readFromEnd' : 'readFromStart'}($skip_lines, $read_lines, $query);
    }

    /**
     * Backend for $this->read
     * Direction: LIFO
     */
    public function readFromEnd($skip_lines, $read_lines, Query $query)
    {
        $PHP_EOL_len = strlen(PHP_EOL);
        $lines = array();
        $s = '';
        $f = @fopen($this->filename, 'rb');
        if ($f !== false) {
            $buffer = '';
            fseek($f, 0, SEEK_END);
            if (ftell($f) === 0) {
                return array();
            }
            while ($read_lines === null || count($lines) < $read_lines) {
                $c = $this->fgetc($f, $buffer);
                if ($c === false) {
                    $l = $this->validateLine($s, $query);
                    if (!($l === false || $skip_lines)) {
                        $lines[] = $l;
                    }
                    break;
                }
                $s = $c . $s;
                if (strpos($s, PHP_EOL) === 0) {
                    $l = $this->validateLine((string)substr($s, $PHP_EOL_len), $query);
                    if ($l !== false) {
                        if ($skip_lines) {
                            $skip_lines--;
                        } else {
                            $lines[] = $l;
                        }
                    }
                    $s = '';
                }
            }
        }
        return $lines;
    }

    /**
     * Backend for $this->readFromEnd
     */
    public function fgetc($file, &$buffer)
    {
        $strlen = strlen($buffer);
        if ($strlen === 0) {
            $pos = ftell($file);
            if ($pos === 0) {
                return false;
            }
            if ($pos < 4096) {
                fseek($file, 0);
                $buffer = fread($file, $pos);
                fseek($file, 0);
            } else {
                fseek($file, -4096, SEEK_CUR);
                $buffer = fread($file, 4096);
                fseek($file, -4096, SEEK_CUR);
            }
            return $this->fgetc($file, $buffer);
        } else {
            $char = substr($buffer, -1);
            $buffer = substr($buffer, 0, $strlen - 1);
            return $char;
        }
    }

    /**
     * Backend for $this->read
     * Direction: FIFO
     */
    public function readFromStart($skip_lines, $read_lines, Query $query)
    {
        $PHP_EOL_len = strlen(PHP_EOL);
        $lines = array();
        $s = '';
        $f = @fopen($this->filename, 'rb');
        if ($f !== false) {
            $buffer = '';
            while ($read_lines === null || count($lines) < $read_lines) {
                if (strlen($buffer) === 0) {
                    $buffer = fread($f, 4096);
                    if (strlen($buffer) === 0) {
                        $l = $this->validateLine($s, $query);
                        if (!($l === false || $skip_lines)) {
                            $lines[] = $l;
                        }
                        break;
                    }
                }
                $s .= substr($buffer, 0, 1);
                $buffer = substr($buffer, 1);
                if (strpos($s, PHP_EOL) !== false) {
                    $l = $this->validateLine((string)substr($s, 0, strlen($s) - $PHP_EOL_len), $query);
                    if ($l !== false) {
                        if ($skip_lines) {
                            $skip_lines--;
                        } else {
                            $lines[] = $l;
                        }
                    }
                    $s = '';
                }
            }
        }
        return $lines;
    }

    /**
     * Return the number of available valid lines.
     *
     * @param Query $query
     *
     * @return int
     */
    public function count(Query $query) {
        $PHP_EOL_len = strlen(PHP_EOL);
        $lines = 0;
        $s = '';
        $f = @fopen($this->filename, 'rb');
        if ($f !== false) {
            $buffer = '';
            while (true) {
                if (strlen($buffer) === 0) {
                    $buffer = fread($f, 4096);
                    if (strlen($buffer) === 0) {
                        if ($this->validateLine($s, $query) !== false) {
                            $lines++;
                        }
                        break;
                    }
                }
                $s .= substr($buffer, 0, 1);
                $buffer = substr($buffer, 1);
                if (strpos($s, PHP_EOL) !== false) {
                    if ($this->validateLine((string)substr($s, 0, strlen($s) - $PHP_EOL_len), $query) !== false) {
                        $lines++;
                    }
                    $s = '';
                }
            }
        }
        return $lines;
    }
}