<?php
/*
Plugin Name: Roman dates
Plugin URI: http://www.kryogenix.org/code/romandates.php.txt
Description: Display post dates in Ancient Roman form
Version: 1.0
Author: Stuart Langridge
Author URI: http://www.kryogenix.org/
*/

/* Released into the public domain, sil, 2009-03-13 (A.D. III ID. MART. MMIX) */
/* http://www.kryogenix.org/days/2009/03/13/roman-dates */

add_filter('the_time', 'romanise');

$months = array(
    1 => array( "name" => "January", "abbr" => "Ian.", "nones" => 5,
        "ides" => 13, "days" => 31 ),
    array( "name" => "February", "abbr" => "Feb.", "nones" => 5,
        "ides" => 13, "days" => 28 ),
    array( "name" => "March", "abbr" => "Mart.", "nones" => 7,
        "ides" => 15, "days" => 31 ),
    array( "name" => "April", "abbr" => "Apr.", "nones" => 5,
        "ides" => 13, "days" => 30 ),
    array( "name" => "May", "abbr" => "Mai.", "nones" => 7,
        "ides" => 15, "days" => 31 ),
    array( "name" => "June", "abbr" => "Iun.", "nones" => 5,
        "ides" => 13, "days" => 30 ),
    array( "name" => "July", "abbr" => "Iul.", "nones" => 7,
        "ides" => 15, "days" => 31 ),
    array( "name" => "August", "abbr" => "Aug.", "nones" => 5,
        "ides" => 13, "days" => 31 ),
    array( "name" => "September", "abbr" => "Sept.", "nones" => 5,
        "ides" => 13, "days" => 30 ),
    array( "name" => "October", "abbr" => "Oct.", "nones" => 7,
        "ides" => 15, "days" => 31 ),
    array( "name" => "November", "abbr" => "Nov.", "nones" => 5,
        "ides" => 13, "days" => 30 ),
    array( "name" => "December", "abbr" => "Dec.", "nones" => 5,
        "ides" => 13, "days" => 31 ),
    array( "name" => "January", "abbr" => "Ian.", "nones" => 5,
        "ides" => 13, "days" => 31 )
);

function convertdigit($num, $x, $l, $c) {
    if ($num < 4) { $digit = str_repeat($x, $num); }
    else if ($num == 4) { $digit = $x . $l; }
    else if ($num == 5) { $digit = $l; }
    else if ($num < 9 ) { $digit = $l . str_repeat($x, $num - 5); }
    else { $digit = $x.$c; }
    return $digit;
}

function arabictoroman($arabic) {
    $arabic = "0000" . $arabic;
    $arabic = substr($arabic, -4);
    $roman = "";
    for ($k=0; $k<4; $k++) {
        if ($k==3) {$a="i"; $b="v"; $c="x";}
        if ($k==2) {$a="x"; $b="l"; $c="c";}
        if ($k==1) {$a="c"; $b="d"; $c="m";}
        if ($k==0) {$a="m"; $b=""; $c="";}
        $d = substr($arabic,$k,1);
        $roman .= convertdigit((int)$d, $a, $b, $c);
    }
    return $roman;
}

function kalends($da, $mo, $arabic_yr, $leap, $caps) {
    global $months;
    $yr = arabictoroman($arabic_yr);
    
    $abbr = $months[$mo]['abbr'];
    $nones = $months[$mo]['nones'];
    $ides = $months[$mo]['ides'];
    $days = $months[$mo]['days'];

    $nonescount = $nones - $da + 1;
    $idescount = $ides - $da + 1;
    $kalendscount = $days - $da + 2;
    $monextnum = $mo+1;
    $monext = $months[$monextnum]['abbr'];
    
    if ($da == 1) { 
        $romandate = "kal. $abbr $yr"; 
    } else if ($da < $nones - 1) { 
        $romandate = "a.d. " . arabictoroman($nonescount) . " non. $abbr $yr";
    } else if ($da == $nones - 1) {
        $romandate="prid. non. $abbr $yr";
    } else if ($da == $nones) {
        $romandate="non. $abbr $yr";
    } else if ($da < $ides - 1) {
        $romandate="a.d. " . arabictoroman($idescount) . " id. $abbr $yr";
    } else if ($da == $ides - 1) {
        $romandate="prid. id. $abbr	$yr";
    } else if ($da == $ides) {
        $romandate="id. $abbr $yr";
    }
    else if ($da == 25 && $days == 29) {
        $romandate="a.d. bis vi kal. mart.";
    } else if ($da < $days) {
        $romandate = "a.d. " . arabictoroman($kalendscount) . " kal. $monext $yr";
    } else {
        $romandate="prid. kal. $monext $yr";
    }

    if ($caps) { $romandate = strtoupper($romandate); }

    return $romandate;
}

function romanise($result='') {
    $t = strtotime($result);
    if (strcmp(date('L', $t), '1') == 0) {
        $leap = true;
    } else {
        $leap = false;
    }
    return kalends((int)date('j',$t) + 1, (int)date('m', $t), (int)date('Y', $t), $leap, true);
}