<?php

class StringTransform
{
    /**
     * This Method Converts a String to Title Case
     *
     * @param string $str
     * @param bool   $apStyle use AP-Style title case if true
     * @return string
     */
    public static function titleCase($str, $apStyle = false) {
        $str = strtolower($str);

        $exclude = 'the a an of by at on in so to for from and or but like';
        if (!$apStyle) $exclude .= ' with before after over';
        $exclude = explode(' ', $exclude);

        $regex = "/(?<!\w)[\p{L}']+/u";

        preg_match_all($regex, $str, $matches);
        $matchCount = count($matches[0]);

        $wordIdx = 0;
        $str = preg_replace_callback($regex, function($matches) use ($exclude, $matchCount, &$wordIdx) {
            // capitalize all words not included in $excluded,
            // with the first and last word always getting capitalized
            if (!in_array($matches[0], $exclude) || ($wordIdx == 0 || $wordIdx == $matchCount - 1)) {
                $word = ucfirst($matches[0]);
            } else {
                $word = $matches[0];
            }

            $wordIdx++;

            return $word;
        }, $str);

        // capitalize letter after colon and parentheses
        $str = preg_replace_callback('/(?<=:\s|\()\p{L}/u', function($matches) {
            return strtoupper($matches[0]);
        }, $str);

        return $str;
    }

    /**
     * ThisMethodConvertsAStringToPascalCase
     *
     * @param string $str
     * @return string
     */
    public static function pascalCase($str) {
        return self::replaceWhitespace(ucwords($str));
    }

    /**
     * thisMethodConvertsAStringToCamelCase
     *
     * @param string $str
     * @return string
     */
    public static function camelCase($str) {
        return lcfirst(self::replaceWhitespace(ucwords($str)));
    }

    /**
     * this_method_converts_a_string_to_snake_case
     *
     * @param string $str
     * @return string
     */
    public static function snakeCase($str) {
        return self::replaceWhitespace(strtolower($str), '_');
    }

    /**
     * ThIs MeThOd CoNvErTs A sTrInG tO sTuDlYcApS
     *
     * @param string $str
     * @param bool   $upperOdd   uppercase odd character positions
     * @param bool   $whitespace if false, whitespaces will be removed
     * @return string
     */
    public static function mixedCase($str, $upperOdd = false, $whitespace = true) {
        if (!$whitespace) {
            $str = self::replaceWhitespace($str);
        }

        $letters = str_split(strtolower($str));

        $i = 0;
        foreach ($letters as &$letter) {
            // only act on letters, ignore whitespace and other chars
            if (preg_match('/\p{L}/u', $letter)) {
                if ($i % 2 === (int) $upperOdd) {
                    $letter = strtoupper($letter);
                }

                $i++;
            }
        }

        $str = implode($letters);

        return $str;
    }

    /**
     * Th1s m3th0d c0nv3rts 4 str1ng t0 l33t
     *
     * @param string       $str
     * @param string|array $mapping 'simple', 'full' (for all leet numbers)
     *                              or associative array for custom mapping, in the form 'letter' => number
     * @return string
     */
    public static function leet($str, $mapping = 'simple') {
        $leetChars = array(
            'a' => 4,
            'e' => 3,
            'i' => 1,
            'o' => 0
        );

        if ($mapping == 'full') {
            $extended = array(
                'g' => 6,
                's' => 5,
                't' => 7
            );

            $leetChars = array_merge($leetChars, $extended);
        } elseif (is_array($mapping)) {
            $leetChars = $mapping;
        }

        $letters = str_split($str);

        foreach ($letters as &$letter) {
            if (array_key_exists(strtolower($letter), $leetChars)) {
                $letter = strtolower($letter);
                $letter = $leetChars[$letter];
            }
        }

        $str = implode($letters);

        return $str;
    }

    private static function replaceWhitespace($str, $separator = '') {
        return preg_replace('/\s+/', $separator, $str);
    }
}