<?php

/**
 * Time and date internationalization management library
 *
 * @author     Timely Network Inc
 * @since      2012.10.09
 *
 * @package    AllInOneCalendar
 * @subpackage AllInOneCalendar.Lib.Utility
 */
class Ai1ec_Time_I18n_Utility extends Ai1ec_Base {

    /**
     * @var char Separator to wrap unique keys and avoid collisions
     *           EOT is used instead of NUL, as NUL is used by `date()`
     *           functions family as guard and causes memory leaks.
     */
    protected $_separator = "\004";

    /**
     * @var array Map of keys, used by date methods
     */
    protected $_keys      = array();

    /**
     * @var array Map of keys for substition
     */
    protected $_skeys     = array();

    /**
     * @var string Format to use when calling `date_i18n()`
     */
    protected $_format    = NULL;

    /**
     * @var Ai1ec_Memory_Utility Parsed time entries
     */
    protected $_memory    = NULL;

    /**
     * @var Ai1ec_Memory_Utility Parsed format entries
     */
    protected $_transf    = NULL;

    /**
     * Constructor
     *
     * Initialize internal memory objects and date keys.
     *
     * @param Ai1ec_Memory_Utility $memory Optionally inject memory to use
     *
     * @return void Constructor does not return
     */
    public function __construct(
        Ai1ec_Registry_Object $registry,
        Ai1ec_Cache_Memory $memory = null
    ) {
        parent::__construct( $registry );
        if ( NULL === $memory ) {
            $memory = $this->_registry->get( 'cache.memory', 120 ); // 30 * 4
        }
        $this->_memory = $memory;
        $this->_transf = $this->_registry->get( 'cache.memory' );
        $this->_keys   = $this->_initialize_keys();
        $this->_skeys  = $this->_initialize_keys(
            $this->_separator,
            $this->_separator
        );
        $this->_format = implode( $this->_separator, $this->_keys );
    }

    /**
     * format method
     *
     * Convenient wrapper for `date_i18n()`, which caches both faster format
     * version and response for {$timestamp} and {$is_gmt} combination.
     *
     * @param string $format    Format string to output timestamp in
     * @param int    $timestamp UNIX timestamp to output in given format
     * @param bool   $is_gmt    Set to true, to treat {$timestamp} as GMT
     *
     * @return string Formatted date-time entry
     */
    public function format( $format, $timestamp = false, $is_gmt = false ) {
        $time_elements = $this->parse( $timestamp, $is_gmt );
        $local_format  = $this->_safe_format( $format );
        return str_replace( $this->_skeys, $time_elements, $local_format );
    }

    /**
     * parse method
     *
     * Parse given timestamp into I18n date/time values map.
     *
     * @param int  $timestamp Timestamp to parse
     * @param bool $is_gmt    Set to true, to treat value as present in GMT
     *
     * @return array Map of date format keys and corresponding time values
     */
    public function parse( $timestamp = false, $is_gmt = false ) {
        $timestamp = (int)$timestamp;
        if ( $timestamp <= 0 ) {
            $timestamp = $this->_registry->get( 'date.system' )->current_time();
        }
        $cache_key = $timestamp . "\0" . $is_gmt;
        if ( NULL === ( $record = $this->_memory->get( $cache_key ) ) ) {
            $record = array_combine(
                $this->_keys,
                explode(
                    $this->_separator,
                    date_i18n( $this->_format, $timestamp, $is_gmt )
                )
            );
            $this->_memory->set( $cache_key, $record );
        }
        return $record;
    }

    /**
     * _safe_format method
     *
     * Prepare safe format value, to use in substitutions.
     * In prepared string special values are wrapped by {$_separator} to allow
     * fast replacement methods, using binary search.
     *
     * @param string $format Given format to polish
     *
     * @return string Modified format, with special keys wrapped in bin fields
     */
    protected function _safe_format( $format ) {
        if ( NULL === ( $safe = $this->_transf->get( $format ) ) ) {
            $safe      = '';
            $state     = 0;
            $separator = $this->_separator;
            $length    = strlen( $format );
            for ( $index = 0; $index < $length; $index++ ) {
                if ( $state > 0 ) {
                    --$state;
                }
                $current = $format{$index};
                if ( 0 === $state ) {
                    if ( '\\' === $current ) {
                        $state = 2;
                    } elseif ( isset( $this->_keys[$current] ) ) {
                        $current = $separator . $current . $separator;
                    }
                }
                if ( 2 !== $state ) {
                    $safe .= $current;
                }
            }
            $this->_transf->set( $format, $safe );
        }
        return $safe;
    }

    /**
     * _initialize_keys method
     *
     * Prepare list of keys, used by date functions.
     * Optionally wrap values (keys are the same, always).
     *
     * @param string $prepend Prefix to date key
     * @param string $append  Suffix to date key
     *
     * @return array Map of date keys
     */
    protected function _initialize_keys( $prepend = '', $append = '' ) {
        $keys = array(
            'd',
            'D',
            'j',
            'l',
            'N',
            'S',
            'w',
            'z',
            'W',
            'F',
            'm',
            'M',
            'n',
            't',
            'L',
            'o',
            'Y',
            'y',
            'a',
            'A',
            'B',
            'g',
            'G',
            'h',
            'H',
            'i',
            's',
            'u',
            'e',
            'I',
            'O',
            'P',
            'T',
            'Z',
            'c',
            'r',
            'U',
        );
        $map = array();
        foreach ( $keys as $key ) {
            $map[$key] = $prepend . $key . $append;
        }
        return $map;
    }

}