<?php
// WString.php
// Created: 2021-06-22
// Updated: 2022-02-27

namespace Index;

use Traversable;
use InvalidArgumentException;
use ValueError;

/**
 * Provides an immutable multi-byte string with arrow methods.
 */
final class WString implements IString {
    use XStringTrait;

    public const DEFAULT_ENCODING = 'utf-8';

    private static $defaultEncoding = self::DEFAULT_ENCODING;

    private string $value;
    private string $encoding;

    public function __construct(string $value = '', ?string $encoding = null) {
        $encoding ??= self::$defaultEncoding;

        if(!mb_check_encoding($value, $encoding))
            throw new InvalidArgumentException('$value is not a valid value for the selected encoding.');

        $this->value = $value;
        $this->encoding = mb_preferred_mime_name($encoding);
    }

    public function getLength(): int {
        return mb_strlen($this->value, $this->encoding);
    }

    /**
     * Returns the amount of bytes the string contains.
     *
     * @return int Amount of raw bytes.
     */
    public function getByteCount(): int {
        return strlen($this->value);
    }

    public function isEmpty(): bool {
        // an empty string is an empty string so this should be fine regardless of encoding
        return $this->value === '';
    }

    public function indexOf(IString|string $text, int $offset = 0): int {
        $text = (string)self::castEncoding($text, $this->encoding);
        $pos = mb_strpos($this->value, $text, $offset, $this->encoding);
        if($pos === false)
            return -1;
        return $pos;
    }

    public function contains(IString|string $text): bool {
        return str_contains($this->value, (string)$text);
    }

    public function substring(int $offset, int|null $length = null): IString {
        return new WString(mb_substr($this->value, $offset, $length, $this->encoding), $this->encoding);
    }

    public function startsWith(IString|string $text): bool {
        $text = self::castEncoding($text, $this->encoding);
        return $this->substring(0, $text->getLength())->equals($text);
    }

    public function endsWith(IString|string $text): bool {
        $text = self::castEncoding($text, $this->encoding);
        return $this->substring(0 - $text->getLength())->equals($text);
    }

    public function replace(IString|string $search, IString|string $replace): IString {
        $search = (string)self::castEncoding($search, $this->encoding);
        $replace = (string)self::castEncoding($replace, $this->encoding);
        $parts = self::doRegex(fn() => mb_split(preg_quote($search), $this->value));
        $subject = implode($replace, $parts);
        return new WString($subject, $this->encoding);
    }

    public function append(IString|string $string): IString {
        $string = self::castEncoding($string, $this->encoding);
        return new WString($this->value . $string->value, $this->encoding);
    }

    public function prepend(IString|string $string): IString {
        $string = self::castEncoding($string, $this->encoding);
        return new WString($string->value . $this->value, $this->encoding);
    }

    public function split(IString|string $separator, int $limit = PHP_INT_MAX): array {
        return XArray::select(
            self::doRegex(fn() => mb_split(preg_quote((string)$separator), $this->value, $limit)),
            fn($str) => new WString($str, $this->encoding)
        );
    }

    public function chunk(int $chunkSize): array {
        return XArray::select(
            mb_str_split($this->value, $chunkSize, $this->encoding),
            fn($str) => new WString($str, $this->encoding)
        );
    }

    private function trimInternal(IString|string $characters, int $flags): IString {
        if($flags & 0x01) {
            if($characters instanceof WString)
                $characters = (string)$characters->convertEncoding($this->encoding);
            else
                $characters = mb_convert_encoding((string)$characters, $this->encoding, 'ascii');
        } else
            $characters = (string)$characters;

        $start = 0;
        $end = $this->getLength() - 1;

        if($flags & 0x02)
            for(; $start < $this->getLength(); ++$start)
                if(mb_strpos($characters, $this[$start], 0, $this->encoding) === false)
                    break;

        if($flags & 0x04)
            for(; $end > 0; --$end)
                if(mb_strpos($characters, $this[$end], 0, $this->encoding) === false)
                    break;

        return $this->substring($start, $end - $start + 1);
    }

    public function trim(IString|string $characters = IString::TRIM_CHARS, bool $convertChars = true): IString {
        $flags = 0x06;
        if($convertChars) $flags |= 0x01;
        return $this->trimInternal($characters, $flags);
    }

    public function trimStart(IString|string $characters = IString::TRIM_CHARS, bool $convertChars = true): IString {
        $flags = 0x02;
        if($convertChars) $flags |= 0x01;
        return $this->trimInternal($characters, $flags);
    }

    public function trimEnd(IString|string $characters = IString::TRIM_CHARS, bool $convertChars = true): IString {
        $flags = 0x04;
        if($convertChars) $flags |= 0x01;
        return $this->trimInternal($characters, $flags);
    }

    public function toLower(): IString {
        return new WString(mb_strtolower($this->value, $this->encoding), $this->encoding);
    }

    public function toUpper(): IString {
        return new WString(mb_strtoupper($this->value, $this->encoding), $this->encoding);
    }

    public function reverse(): IString {
        $chars = [];
        foreach($this as $char)
            $chars[] = $char;
        return new WString(implode(array_reverse($chars)), $this->encoding);
    }

    public function __toString(): string {
        return $this->value;
    }

    public function toAString(bool $convert = true): AString {
        $value = $this->value;
        if($convert && self::sameEncoding('ascii', $this->encoding))
            $value = mb_convert_encoding($value, 'ascii', $this->encoding);
        return new AString($value);
    }

    public function getEncoding(): string {
        return $this->encoding;
    }

    public function convertEncoding(string $encoding): WString {
        if(self::sameEncoding($encoding, $this->encoding))
            return $this;
        $value = mb_convert_encoding($this->value, $encoding, $this->encoding);
        return new WString($value, $encoding);
    }

    /**
     * Checks if an offset exists in the string.
     *
     * You should call isset($string[$offset]) instead of $string->offsetExists($offset).
     *
     * @see https://www.php.net/manual/en/arrayaccess.offsetexists.php
     * @param int $offset Character offset.
     * @return bool true if it exists, false if not.
     */
    public function offsetExists(mixed $offset): bool {
        $offset = (int)$offset;
        return $offset >= 0 && $offset < $this->getLength();
    }

    /**
     * Gets an offset from the string.
     *
     * You should do $string[$offset] instead of $string->offsetGet($offset).
     *
     * @see https://www.php.net/manual/en/arrayaccess.offsetget.php
     * @param int $offset Character offset.
     * @return string Character at that offset.
     */
    public function offsetGet(mixed $offset): mixed {
        return mb_substr($this->value, (int)$offset, 1, $this->encoding);
    }

    /**
     * Gets an iterator object for this string.
     *
     * @return StringIterator An iterator for this string.
     */
    public function getIterator(): Traversable {
        return new StringIterator($this);
    }

    /**
     * Returns the data which should be serialized as json.
     *
     * @see https://www.php.net/manual/en/jsonserializable.jsonserialize.php
     * @return mixed Data to be passed to json_encode.
     */
    public function jsonSerialize(): mixed {
        return $this->value;
    }

    public function bencodeSerialise(): mixed {
        return $this->value;
    }

    /**
     * Gets a serialized representation of this object.
     *
     * @return array Serialized data.
     */
    public function __serialize(): array {
        return [$this->encoding, $this->value];
    }

    /**
     * Reconstructs an object from a serialized string.
     *
     * @param array $serialized Serialized data.
     */
    public function __unserialize(array $serialized): void {
        [$this->encoding, $this->value] = $serialized;
    }

    /**
     * Checks whether this string is identical to another.
     *
     * @param mixed $other An instance of IString or a PHP string.
     * @return bool true if the strings have the same value, false if not.
     */
    public function equals(mixed $other): bool {
        return $this->compare($other) === 0;
    }

    /**
     * Compares whether this string is identical to another.
     *
     * @param mixed $other An instance of IString or a PHP string.
     */
    public function compare(mixed $other): int {
        $other = self::castEncoding($other, $this->encoding);
        return strcmp($this->value, (string)$other);
    }

    /**
     * Creates a new identical WString instance.
     *
     * This method is somewhat pointless, given the immutable nature of this object,
     *  but rather people calling this instead of calling ->substring(0);
     *
     * @return WString A new identical instance of WString.
     */
    public function clone(): mixed {
        return new WString($this->value, $this->encoding);
    }

    private function doRegex(callable $callback): mixed {
        $encoding = self::getRegexEncoding();
        self::setRegexEncoding($this->encoding);
        $result = $callback();
        self::setRegexEncoding($encoding);
        return $result;
    }

    private static function sameEncoding(string $name1, string $name2): bool {
        return mb_preferred_mime_name($name1) === mb_preferred_mime_name($name2);
    }

    /**
     * Joins an iterable object together with a separator to create a string.
     *
     * @param iterable $source Source object.
     * @param IString|string $separator Separator to use as glue.
     * @param ?string $encoding Desired encoding, null for Index default.
     * @return WString Resulting string.
     */
    public static function join(iterable $source, IString|string $separator = '', ?string $encoding = null): WString {
        // func probably doesn't work entirely as intended
        $encoding ??= self::getDefaultEncoding();
        $separator = self::castEncoding($separator, $encoding);
        if(!is_array($source)) {
            $parts = [];
            foreach($source as $value)
                $parts[] = $value;
            $source = $parts;
        }

        return new WString(implode((string)$separator, $source), $encoding);
    }

    public static function getDefaultEncoding(): string {
        return self::$defaultEncoding;
    }

    public static function setDefaultEncoding(string $encoding = ''): void {
        if(empty($encoding))
            self::$defaultEncoding = self::DEFAULT_ENCODING;
        else {
            try {
                if(mb_encoding_aliases($encoding) !== false)
                    self::$defaultEncoding = $encoding;
            } catch(ValueError $ex) {}
        }
    }

    public static function getInternalEncoding(): string {
        return mb_internal_encoding();
    }

    public static function setInternalEncoding(string $encoding): void {
        mb_internal_encoding($encoding);
    }

    public static function getRegexEncoding(): string {
        return mb_regex_encoding();
    }

    public static function setRegexEncoding(string $encoding): void {
        mb_regex_encoding($encoding);
    }

    public static function fromRequest(string $raw): WString {
        return new WString($raw, self::getInternalEncoding());
    }

    /**
     * Returns a reusable empty string instance.
     *
     * @return WString An empty string.
     */
    public static function empty(): WString {
        static $empty = null;
        $empty ??= new WString('');
        return $empty;
    }

    public static function cast(mixed $string): WString {
        if($string instanceof WString)
            return $string;
        if($string instanceof AString)
            return $string->toWString('ascii', false);
        return new WString((string)$string, 'ascii');
    }

    public static function castEncoding(mixed $string, string $encoding): WString {
        return self::cast($string)->convertEncoding($encoding);
    }
}