<?php
// AString.php
// Created: 2021-04-26
// Updated: 2023-01-01

namespace Index;

use Traversable;
use InvalidArgumentException;

/**
 * Provides an immutable ASCII string with arrow methods.
 *
 * Normal PHP strings should be used for buffers/byte arrays.
 */
final class AString implements IString {
    use XStringTrait;

    private string $value;

    /**
     * Create an AString instance.
     *
     * @param string $value PHP string to inherit.
     * @return AString New instance of AString.
     */
    public function __construct(string $value) {
        $this->value = $value;
    }

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

    public function isEmpty(): bool {
        return $this->value === '';
    }

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

    /**
     * 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 $offset): bool {
        return isset($this->value[$offset]);
    }

    /**
     * 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 $this->value[$offset];
    }

    /**
     * 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->value];
    }

    /**
     * Reconstructs an object from a serialized string.
     *
     * @param array $serialized Serialized data.
     */
    public function __unserialize(array $serialized): void {
        $this->value = $serialized[0];
    }

    /**
     * Checks whether this string is identical to another.
     *
     * @param mixed $other An instance of AString 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 $other): int {
        return strcmp($this->value, (string)$other);
    }

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

    public function indexOf(IString|string $text, int $offset = 0): int {
        $pos = strpos($this->value, (string)$text, $offset);
        if($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 $length = null): IString {
        return new AString(substr($this->value, $offset, $length));
    }

    public function replace(IString|string $search, IString|string $replace): IString {
        return new AString(str_replace((string)$search, (string)$replace, $this->value));
    }

    public function append(IString|string $string): IString {
        return new AString($this->value . (string)$string);
    }

    public function prepend(IString|string $string): IString {
        return new AString(((string)$string) . $this->value);
    }

    public function split(IString|string $separator, int $limit = PHP_INT_MAX): array {
        $separator = (string)$separator;
        if(empty($separator))
            throw new InvalidArgumentException('$separator may not be empty.');
        return XArray::select(
            explode($separator, $this->value, $limit),
            fn($str) => new AString($str)
        );
    }

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

    public function trim(IString|string $characters = IString::TRIM_CHARS): IString {
        return new AString(trim($this->value, (string)$characters));
    }

    public function trimStart(IString|string $characters = IString::TRIM_CHARS): IString {
        return new AString(ltrim($this->value, (string)$characters));
    }

    public function trimEnd(IString|string $characters = IString::TRIM_CHARS): IString {
        return new AString(rtrim($this->value, (string)$characters));
    }

    public function toLower(): IString {
        return new AString(strtolower($this->value));
    }

    public function toUpper(): IString {
        return new AString(strtoupper($this->value));
    }

    public function reverse(): IString {
        return new AString(strrev($this->value));
    }

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

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

    /**
     * Casts this AString to a WString.
     *
     * @param ?string $encoding Intended encoding, null for the Index-level default.
     * @param bool $convert true to convert the string to the target encoding, false to leave the bytes as-is.
     * @return WString A WString of the provided encoding with the value of this AString.
     */
    public function toWString(?string $encoding = null, bool $convert = true): WString {
        $value = $this->value;
        $encoding ??= WString::getDefaultEncoding();
        if($convert)
            $value = mb_convert_encoding($value, $encoding, 'ascii');
        return new WString($value, $encoding);
    }

    /**
     * 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.
     * @return AString Resulting string.
     */
    public static function join(iterable $source, IString|string $separator = ''): AString {
        if(!is_array($source)) {
            $parts = [];
            foreach($source as $value)
                $parts[] = $value;
            $source = $parts;
        }

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

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

    /**
     * Converts a value to AString.
     *
     * @param mixed $value Source value.
     * @return AString An AString representing the given value.
     */
    public static function cast(mixed $value): AString {
        if($value instanceof AString)
            return $value;
        if($value instanceof WString)
            return $value->toAString();
        return new AString((string)$value);
    }
}