DateFormatter.php

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<?php
class DateFormatter {
    public $mSource, $mTarget;
    public $monthNames = '', $rxDM, $rxMD, $rxDMY, $rxYDM, $rxMDY, $rxYMD;

    public $regexes, $pDays, $pMonths, $pYears;
    public $rules, $xMonths, $preferences;

    protected $lang, $mLinked;

    const ALL = -1;
    const NONE = 0;
    const MDY = 1;
    const DMY = 2;
    const YMD = 3;
    const ISO1 = 4;
    const LASTPREF = 4;
    const ISO2 = 5;
    const YDM = 6;
    const DM = 7;
    const MD = 8;
    const LAST = 8;

    public function __construct( Language $lang ) {
        $this->lang = $lang;

        $this->monthNames = $this->getMonthRegex();
        for ( $i = 1; $i <= 12; $i++ ) {
            $this->xMonths[$this->lang->lc( $this->lang->getMonthName( $i ) )] = $i;
            $this->xMonths[$this->lang->lc( $this->lang->getMonthAbbreviation( $i ) )] = $i;
        }

        $this->regexTrail = '(?![a-z])/iu';

        # Partial regular expressions
        $this->prxDM = '\[\[(\d{1,2})[ _](' . $this->monthNames . ')\]\]';
        $this->prxMD = '\[\[(' . $this->monthNames . ')[ _](\d{1,2})\]\]';
        $this->prxY = '\[\[(\d{1,4}([ _]BC|))\]\]';
        $this->prxISO1 = '\[\[(-?\d{4})]]-\[\[(\d{2})-(\d{2})\]\]';
        $this->prxISO2 = '\[\[(-?\d{4})-(\d{2})-(\d{2})\]\]';

        # Real regular expressions
        $this->regexes[self::DMY] = "/{$this->prxDM}(?: *, *| +){$this->prxY}{$this->regexTrail}";
        $this->regexes[self::YDM] = "/{$this->prxY}(?: *, *| +){$this->prxDM}{$this->regexTrail}";
        $this->regexes[self::MDY] = "/{$this->prxMD}(?: *, *| +){$this->prxY}{$this->regexTrail}";
        $this->regexes[self::YMD] = "/{$this->prxY}(?: *, *| +){$this->prxMD}{$this->regexTrail}";
        $this->regexes[self::DM] = "/{$this->prxDM}{$this->regexTrail}";
        $this->regexes[self::MD] = "/{$this->prxMD}{$this->regexTrail}";
        $this->regexes[self::ISO1] = "/{$this->prxISO1}{$this->regexTrail}";
        $this->regexes[self::ISO2] = "/{$this->prxISO2}{$this->regexTrail}";

        # Extraction keys
        # See the comments in replace() for the meaning of the letters
        $this->keys[self::DMY] = 'jFY';
        $this->keys[self::YDM] = 'Y jF';
        $this->keys[self::MDY] = 'FjY';
        $this->keys[self::YMD] = 'Y Fj';
        $this->keys[self::DM] = 'jF';
        $this->keys[self::MD] = 'Fj';
        $this->keys[self::ISO1] = 'ymd'; # y means ISO year
        $this->keys[self::ISO2] = 'ymd';

        # Target date formats
        $this->targets[self::DMY] = '[[F j|j F]] [[Y]]';
        $this->targets[self::YDM] = '[[Y]], [[F j|j F]]';
        $this->targets[self::MDY] = '[[F j]], [[Y]]';
        $this->targets[self::YMD] = '[[Y]] [[F j]]';
        $this->targets[self::DM] = '[[F j|j F]]';
        $this->targets[self::MD] = '[[F j]]';
        $this->targets[self::ISO1] = '[[Y|y]]-[[F j|m-d]]';
        $this->targets[self::ISO2] = '[[y-m-d]]';

        # Rules
        #            pref    source       target
        $this->rules[self::DMY][self::MD] = self::DM;
        $this->rules[self::ALL][self::MD] = self::MD;
        $this->rules[self::MDY][self::DM] = self::MD;
        $this->rules[self::ALL][self::DM] = self::DM;
        $this->rules[self::NONE][self::ISO2] = self::ISO1;

        $this->preferences = [
            'default' => self::NONE,
            'dmy' => self::DMY,
            'mdy' => self::MDY,
            'ymd' => self::YMD,
            'ISO 8601' => self::ISO1,
        ];
    }

    public static function getInstance( $lang = null ) {
        global $wgContLang, $wgMainCacheType;

        $lang = $lang ? wfGetLangObj( $lang ) : $wgContLang;
        $cache = ObjectCache::getLocalServerInstance( $wgMainCacheType );

        static $dateFormatter = false;
        if ( !$dateFormatter ) {
            $dateFormatter = $cache->getWithSetCallback(
                $cache->makeKey( 'dateformatter', $lang->getCode() ),
                $cache::TTL_HOUR,
                function () use ( $lang ) {
                    return new DateFormatter( $lang );
                }
            );
        }

        return $dateFormatter;
    }

    public function reformat( $preference, $text, $options = [ 'linked' ] ) {
        $linked = in_array( 'linked', $options );
        $match_whole = in_array( 'match-whole', $options );

        if ( isset( $this->preferences[$preference] ) ) {
            $preference = $this->preferences[$preference];
        } else {
            $preference = self::NONE;
        }
        for ( $i = 1; $i <= self::LAST; $i++ ) {
            $this->mSource = $i;
            if ( isset( $this->rules[$preference][$i] ) ) {
                # Specific rules
                $this->mTarget = $this->rules[$preference][$i];
            } elseif ( isset( $this->rules[self::ALL][$i] ) ) {
                # General rules
                $this->mTarget = $this->rules[self::ALL][$i];
            } elseif ( $preference ) {
                # User preference
                $this->mTarget = $preference;
            } else {
                # Default
                $this->mTarget = $i;
            }
            $regex = $this->regexes[$i];

            // Horrible hack
            if ( !$linked ) {
                $regex = str_replace( [ '\[\[', '\]\]' ], '', $regex );
            }

            if ( $match_whole ) {
                // Let's hope this works
                $regex = preg_replace( '!^/!', '/^', $regex );
                $regex = str_replace( $this->regexTrail,
                    '$' . $this->regexTrail, $regex );
            }

            // Another horrible hack
            $this->mLinked = $linked;
            $text = preg_replace_callback( $regex, [ $this, 'replace' ], $text );
            unset( $this->mLinked );
        }
        return $text;
    }

    public function replace( $matches ) {
        # Extract information from $matches
        $linked = true;
        if ( isset( $this->mLinked ) ) {
            $linked = $this->mLinked;
        }

        $bits = [];
        $key = $this->keys[$this->mSource];
        $keyLength = strlen( $key );
        for ( $p = 0; $p < $keyLength; $p++ ) {
            if ( $key[$p] != ' ' ) {
                $bits[$key[$p]] = $matches[$p + 1];
            }
        }

        return $this->formatDate( $bits, $linked );
    }

    public function formatDate( $bits, $link = true ) {
        $format = $this->targets[$this->mTarget];

        if ( !$link ) {
            // strip piped links
            $format = preg_replace( '/\[\[[^|]+\|([^\]]+)\]\]/', '$1', $format );
            // strip remaining links
            $format = str_replace( [ '[[', ']]' ], '', $format );
        }

        # Construct new date
        $text = '';
        $fail = false;

        // Pre-generate y/Y stuff because we need the year for the <span> title.
        if ( !isset( $bits['y'] ) && isset( $bits['Y'] ) ) {
            $bits['y'] = $this->makeIsoYear( $bits['Y'] );
        }
        if ( !isset( $bits['Y'] ) && isset( $bits['y'] ) ) {
            $bits['Y'] = $this->makeNormalYear( $bits['y'] );
        }

        if ( !isset( $bits['m'] ) ) {
            $m = $this->makeIsoMonth( $bits['F'] );
            if ( !$m || $m == '00' ) {
                $fail = true;
            } else {
                $bits['m'] = $m;
            }
        }

        if ( !isset( $bits['d'] ) ) {
            $bits['d'] = sprintf( '%02d', $bits['j'] );
        }

        $formatLength = strlen( $format );
        for ( $p = 0; $p < $formatLength; $p++ ) {
            $char = $format[$p];
            switch ( $char ) {
                case 'd': # ISO day of month
                    $text .= $bits['d'];
                    break;
                case 'm': # ISO month
                    $text .= $bits['m'];
                    break;
                case 'y': # ISO year
                    $text .= $bits['y'];
                    break;
                case 'j': # ordinary day of month
                    if ( !isset( $bits['j'] ) ) {
                        $text .= intval( $bits['d'] );
                    } else {
                        $text .= $bits['j'];
                    }
                    break;
                case 'F': # long month
                    if ( !isset( $bits['F'] ) ) {
                        $m = intval( $bits['m'] );
                        if ( $m > 12 || $m < 1 ) {
                            $fail = true;
                        } else {
                            $text .= $this->lang->getMonthName( $m );
                        }
                    } else {
                        $text .= ucfirst( $bits['F'] );
                    }
                    break;
                case 'Y': # ordinary (optional BC) year
                    $text .= $bits['Y'];
                    break;
                default:
                    $text .= $char;
            }
        }
        if ( $fail ) {
            $text = $matches[0];
        }

        $isoBits = [];
        if ( isset( $bits['y'] ) ) {
            $isoBits[] = $bits['y'];
        }
        $isoBits[] = $bits['m'];
        $isoBits[] = $bits['d'];
        $isoDate = implode( '-', $isoBits );

        // Output is not strictly HTML (it's wikitext), but <span> is whitelisted.
        $text = Html::rawElement( 'span',
                    [ 'class' => 'mw-formatted-date', 'title' => $isoDate ], $text );

        return $text;
    }

    public function getMonthRegex() {
        $names = [];
        for ( $i = 1; $i <= 12; $i++ ) {
            $names[] = $this->lang->getMonthName( $i );
            $names[] = $this->lang->getMonthAbbreviation( $i );
        }
        return implode( '|', $names );
    }

    public function makeIsoMonth( $monthName ) {
        $n = $this->xMonths[$this->lang->lc( $monthName )];
        return sprintf( '%02d', $n );
    }

    public function makeIsoYear( $year ) {
        # Assumes the year is in a nice format, as enforced by the regex
        if ( substr( $year, -2 ) == 'BC' ) {
            $num = intval( substr( $year, 0, -3 ) ) - 1;
            # PHP bug note: sprintf( "%04d", -1 ) fails poorly
            $text = sprintf( '-%04d', $num );

        } else {
            $text = sprintf( '%04d', $year );
        }
        return $text;
    }

    public function makeNormalYear( $iso ) {
        if ( $iso[0] == '-' ) {
            $text = ( intval( substr( $iso, 1 ) ) + 1 ) . ' BC';
        } else {
            $text = intval( $iso );
        }
        return $text;
    }
}