<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Mime;

/**
 * @author Fabien Potencier <fabien@symfony.com>
 * @author Xavier De Cock <xdecock@gmail.com>
 *
 * @internal
 */
final class CharacterStream
{
    /** Pre-computed for optimization */
    private const UTF8_LENGTH_MAP = [
        "\x00" => 1, "\x01" => 1, "\x02" => 1, "\x03" => 1, "\x04" => 1, "\x05" => 1, "\x06" => 1, "\x07" => 1,
        "\x08" => 1, "\x09" => 1, "\x0a" => 1, "\x0b" => 1, "\x0c" => 1, "\x0d" => 1, "\x0e" => 1, "\x0f" => 1,
        "\x10" => 1, "\x11" => 1, "\x12" => 1, "\x13" => 1, "\x14" => 1, "\x15" => 1, "\x16" => 1, "\x17" => 1,
        "\x18" => 1, "\x19" => 1, "\x1a" => 1, "\x1b" => 1, "\x1c" => 1, "\x1d" => 1, "\x1e" => 1, "\x1f" => 1,
        "\x20" => 1, "\x21" => 1, "\x22" => 1, "\x23" => 1, "\x24" => 1, "\x25" => 1, "\x26" => 1, "\x27" => 1,
        "\x28" => 1, "\x29" => 1, "\x2a" => 1, "\x2b" => 1, "\x2c" => 1, "\x2d" => 1, "\x2e" => 1, "\x2f" => 1,
        "\x30" => 1, "\x31" => 1, "\x32" => 1, "\x33" => 1, "\x34" => 1, "\x35" => 1, "\x36" => 1, "\x37" => 1,
        "\x38" => 1, "\x39" => 1, "\x3a" => 1, "\x3b" => 1, "\x3c" => 1, "\x3d" => 1, "\x3e" => 1, "\x3f" => 1,
        "\x40" => 1, "\x41" => 1, "\x42" => 1, "\x43" => 1, "\x44" => 1, "\x45" => 1, "\x46" => 1, "\x47" => 1,
        "\x48" => 1, "\x49" => 1, "\x4a" => 1, "\x4b" => 1, "\x4c" => 1, "\x4d" => 1, "\x4e" => 1, "\x4f" => 1,
        "\x50" => 1, "\x51" => 1, "\x52" => 1, "\x53" => 1, "\x54" => 1, "\x55" => 1, "\x56" => 1, "\x57" => 1,
        "\x58" => 1, "\x59" => 1, "\x5a" => 1, "\x5b" => 1, "\x5c" => 1, "\x5d" => 1, "\x5e" => 1, "\x5f" => 1,
        "\x60" => 1, "\x61" => 1, "\x62" => 1, "\x63" => 1, "\x64" => 1, "\x65" => 1, "\x66" => 1, "\x67" => 1,
        "\x68" => 1, "\x69" => 1, "\x6a" => 1, "\x6b" => 1, "\x6c" => 1, "\x6d" => 1, "\x6e" => 1, "\x6f" => 1,
        "\x70" => 1, "\x71" => 1, "\x72" => 1, "\x73" => 1, "\x74" => 1, "\x75" => 1, "\x76" => 1, "\x77" => 1,
        "\x78" => 1, "\x79" => 1, "\x7a" => 1, "\x7b" => 1, "\x7c" => 1, "\x7d" => 1, "\x7e" => 1, "\x7f" => 1,
        "\x80" => 0, "\x81" => 0, "\x82" => 0, "\x83" => 0, "\x84" => 0, "\x85" => 0, "\x86" => 0, "\x87" => 0,
        "\x88" => 0, "\x89" => 0, "\x8a" => 0, "\x8b" => 0, "\x8c" => 0, "\x8d" => 0, "\x8e" => 0, "\x8f" => 0,
        "\x90" => 0, "\x91" => 0, "\x92" => 0, "\x93" => 0, "\x94" => 0, "\x95" => 0, "\x96" => 0, "\x97" => 0,
        "\x98" => 0, "\x99" => 0, "\x9a" => 0, "\x9b" => 0, "\x9c" => 0, "\x9d" => 0, "\x9e" => 0, "\x9f" => 0,
        "\xa0" => 0, "\xa1" => 0, "\xa2" => 0, "\xa3" => 0, "\xa4" => 0, "\xa5" => 0, "\xa6" => 0, "\xa7" => 0,
        "\xa8" => 0, "\xa9" => 0, "\xaa" => 0, "\xab" => 0, "\xac" => 0, "\xad" => 0, "\xae" => 0, "\xaf" => 0,
        "\xb0" => 0, "\xb1" => 0, "\xb2" => 0, "\xb3" => 0, "\xb4" => 0, "\xb5" => 0, "\xb6" => 0, "\xb7" => 0,
        "\xb8" => 0, "\xb9" => 0, "\xba" => 0, "\xbb" => 0, "\xbc" => 0, "\xbd" => 0, "\xbe" => 0, "\xbf" => 0,
        "\xc0" => 2, "\xc1" => 2, "\xc2" => 2, "\xc3" => 2, "\xc4" => 2, "\xc5" => 2, "\xc6" => 2, "\xc7" => 2,
        "\xc8" => 2, "\xc9" => 2, "\xca" => 2, "\xcb" => 2, "\xcc" => 2, "\xcd" => 2, "\xce" => 2, "\xcf" => 2,
        "\xd0" => 2, "\xd1" => 2, "\xd2" => 2, "\xd3" => 2, "\xd4" => 2, "\xd5" => 2, "\xd6" => 2, "\xd7" => 2,
        "\xd8" => 2, "\xd9" => 2, "\xda" => 2, "\xdb" => 2, "\xdc" => 2, "\xdd" => 2, "\xde" => 2, "\xdf" => 2,
        "\xe0" => 3, "\xe1" => 3, "\xe2" => 3, "\xe3" => 3, "\xe4" => 3, "\xe5" => 3, "\xe6" => 3, "\xe7" => 3,
        "\xe8" => 3, "\xe9" => 3, "\xea" => 3, "\xeb" => 3, "\xec" => 3, "\xed" => 3, "\xee" => 3, "\xef" => 3,
        "\xf0" => 4, "\xf1" => 4, "\xf2" => 4, "\xf3" => 4, "\xf4" => 4, "\xf5" => 4, "\xf6" => 4, "\xf7" => 4,
        "\xf8" => 5, "\xf9" => 5, "\xfa" => 5, "\xfb" => 5, "\xfc" => 6, "\xfd" => 6, "\xfe" => 0, "\xff" => 0,
    ];

    private string $data = '';
    private int $dataSize = 0;
    private array $map = [];
    private int $charCount = 0;
    private int $currentPos = 0;
    private int $fixedWidth = 0;

    /**
     * @param resource|string $input
     */
    public function __construct($input, ?string $charset = 'utf-8')
    {
        $charset = strtolower(trim($charset)) ?: 'utf-8';
        if ('utf-8' === $charset || 'utf8' === $charset) {
            $this->fixedWidth = 0;
            $this->map = ['p' => [], 'i' => []];
        } else {
            switch ($charset) {
                // 16 bits
                case 'ucs2':
                case 'ucs-2':
                case 'utf16':
                case 'utf-16':
                    $this->fixedWidth = 2;
                    break;

                    // 32 bits
                case 'ucs4':
                case 'ucs-4':
                case 'utf32':
                case 'utf-32':
                    $this->fixedWidth = 4;
                    break;

                    // 7-8 bit charsets: (us-)?ascii, (iso|iec)-?8859-?[0-9]+, windows-?125[0-9], cp-?[0-9]+, ansi, macintosh,
                //                   koi-?7, koi-?8-?.+, mik, (cork|t1), v?iscii
                    // and fallback
                default:
                    $this->fixedWidth = 1;
            }
        }
        if (\is_resource($input)) {
            $blocks = 16372;
            while (false !== $read = fread($input, $blocks)) {
                $this->write($read);
            }
        } else {
            $this->write($input);
        }
    }

    public function read(int $length): ?string
    {
        if ($this->currentPos >= $this->charCount) {
            return null;
        }
        $length = ($this->currentPos + $length > $this->charCount) ? $this->charCount - $this->currentPos : $length;
        if ($this->fixedWidth > 0) {
            $len = $length * $this->fixedWidth;
            $ret = substr($this->data, $this->currentPos * $this->fixedWidth, $len);
            $this->currentPos += $length;
        } else {
            $end = $this->currentPos + $length;
            $end = $end > $this->charCount ? $this->charCount : $end;
            $ret = '';
            $start = 0;
            if ($this->currentPos > 0) {
                $start = $this->map['p'][$this->currentPos - 1];
            }
            $to = $start;
            for (; $this->currentPos < $end; ++$this->currentPos) {
                if (isset($this->map['i'][$this->currentPos])) {
                    $ret .= substr($this->data, $start, $to - $start).'?';
                    $start = $this->map['p'][$this->currentPos];
                } else {
                    $to = $this->map['p'][$this->currentPos];
                }
            }
            $ret .= substr($this->data, $start, $to - $start);
        }

        return $ret;
    }

    public function readBytes(int $length): ?array
    {
        if (null !== $read = $this->read($length)) {
            return array_map('ord', str_split($read, 1));
        }

        return null;
    }

    public function setPointer(int $charOffset): void
    {
        if ($this->charCount < $charOffset) {
            $charOffset = $this->charCount;
        }
        $this->currentPos = $charOffset;
    }

    public function write(string $chars): void
    {
        $ignored = '';
        $this->data .= $chars;
        if ($this->fixedWidth > 0) {
            $strlen = \strlen($chars);
            $ignoredL = $strlen % $this->fixedWidth;
            $ignored = $ignoredL ? substr($chars, -$ignoredL) : '';
            $this->charCount += ($strlen - $ignoredL) / $this->fixedWidth;
        } else {
            $this->charCount += $this->getUtf8CharPositions($chars, $this->dataSize, $ignored);
        }
        $this->dataSize = \strlen($this->data) - \strlen($ignored);
    }

    private function getUtf8CharPositions(string $string, int $startOffset, string &$ignoredChars): int
    {
        $strlen = \strlen($string);
        $charPos = \count($this->map['p']);
        $foundChars = 0;
        $invalid = false;
        for ($i = 0; $i < $strlen; ++$i) {
            $char = $string[$i];
            $size = self::UTF8_LENGTH_MAP[$char];
            if (0 == $size) {
                /* char is invalid, we must wait for a resync */
                $invalid = true;
                continue;
            }

            if ($invalid) {
                /* We mark the chars as invalid and start a new char */
                $this->map['p'][$charPos + $foundChars] = $startOffset + $i;
                $this->map['i'][$charPos + $foundChars] = true;
                ++$foundChars;
                $invalid = false;
            }
            if (($i + $size) > $strlen) {
                $ignoredChars = substr($string, $i);
                break;
            }
            for ($j = 1; $j < $size; ++$j) {
                $char = $string[$i + $j];
                if ($char > "\x7F" && $char < "\xC0") {
                    // Valid - continue parsing
                } else {
                    /* char is invalid, we must wait for a resync */
                    $invalid = true;
                    continue 2;
                }
            }
            /* Ok we got a complete char here */
            $this->map['p'][$charPos + $foundChars] = $startOffset + $i + $size;
            $i += $j - 1;
            ++$foundChars;
        }

        return $foundChars;
    }
}