<?php

declare(strict_types=1);

namespace Contractless\Rpc\Protocol;

use Contractless\Rpc\Exception\ProtocolException;

final class Binary
{
    public static function u8(int $value): string
    {
        self::range($value, 0, 0xff, 'u8');
        return pack('C', $value);
    }

    public static function u16(int $value): string
    {
        self::range($value, 0, 0xffff, 'u16');
        return pack('v', $value);
    }

    public static function u32(int $value): string
    {
        self::range($value, 0, 0xffffffff, 'u32');
        return pack('V', $value);
    }

    public static function u64(int $value): string
    {
        if (PHP_INT_SIZE < 8 || $value < 0) {
            throw new ProtocolException('u64 values require 64-bit PHP and a non-negative integer.');
        }

        return pack('V2', $value & 0xffffffff, $value >> 32);
    }

    public static function i8(int $value): string
    {
        self::range($value, -128, 127, 'i8');
        return pack('c', $value);
    }

    public static function i16(int $value): string
    {
        self::range($value, -32768, 32767, 'i16');
        return pack('v', $value & 0xffff);
    }

    public static function i32(int $value): string
    {
        self::range($value, -2147483648, 2147483647, 'i32');
        return pack('V', $value & 0xffffffff);
    }

    public static function i64(int $value): string
    {
        if (PHP_INT_SIZE < 8) {
            throw new ProtocolException('i64 values require 64-bit PHP.');
        }
        return pack('V2', $value & 0xffffffff, $value >> 32);
    }

    public static function u128(string $value): string
    {
        return self::decimalInteger($value, false);
    }

    public static function i128(string $value): string
    {
        return self::decimalInteger($value, true);
    }

    public static function readU32(string $bytes): int
    {
        self::length($bytes, 4, 'u32');
        return unpack('Vvalue', $bytes)['value'];
    }

    public static function hex(string $hex, int $bytes, string $field): string
    {
        if (strlen($hex) !== $bytes * 2 || !ctype_xdigit($hex)) {
            throw new ProtocolException("$field must be exactly $bytes bytes of hexadecimal data.");
        }

        $decoded = hex2bin($hex);
        if ($decoded === false) {
            throw new ProtocolException("$field is not valid hexadecimal data.");
        }
        return $decoded;
    }

    public static function fixedText(string $value, int $bytes, string $field): string
    {
        if (strlen($value) > $bytes) {
            throw new ProtocolException("$field must be $bytes bytes or less.");
        }
        return str_pad($value, $bytes, ' ');
    }

    public static function length(string $value, int $bytes, string $field): void
    {
        if (strlen($value) !== $bytes) {
            throw new ProtocolException("$field must be exactly $bytes bytes.");
        }
    }

    private static function range(int $value, int $minimum, int $maximum, string $type): void
    {
        if ($value < $minimum || $value > $maximum) {
            throw new ProtocolException("$value is outside the $type range.");
        }
    }

    private static function decimalInteger(string $value, bool $signed): string
    {
        $value = trim($value);
        $negative = str_starts_with($value, '-');
        $digits = $negative ? substr($value, 1) : $value;
        if ($digits === '' || !ctype_digit($digits) || (!$signed && $negative)) {
            throw new ProtocolException('Invalid 128-bit decimal integer.');
        }
        $digits = ltrim($digits, '0');
        $digits = $digits === '' ? '0' : $digits;

        $maximum = $signed
            ? ($negative ? '170141183460469231731687303715884105728' : '170141183460469231731687303715884105727')
            : '340282366920938463463374607431768211455';
        if (strlen($digits) > strlen($maximum)
            || (strlen($digits) === strlen($maximum) && strcmp($digits, $maximum) > 0)
        ) {
            throw new ProtocolException('128-bit decimal integer is outside its allowed range.');
        }

        $bytes = '';
        for ($index = 0; $index < 16; $index++) {
            [$digits, $remainder] = self::divideDecimal($digits, 256);
            $bytes .= chr($remainder);
        }
        if ($digits !== '0') {
            throw new ProtocolException('128-bit decimal integer is too large.');
        }

        if ($negative) {
            $carry = 1;
            for ($index = 0; $index < 16; $index++) {
                $next = ((~ord($bytes[$index])) & 0xff) + $carry;
                $bytes[$index] = chr($next & 0xff);
                $carry = $next > 0xff ? 1 : 0;
            }
        }
        return $bytes;
    }

    /** @return array{string, int} */
    private static function divideDecimal(string $digits, int $divisor): array
    {
        $quotient = '';
        $remainder = 0;
        for ($index = 0, $length = strlen($digits); $index < $length; $index++) {
            $number = ($remainder * 10) + (ord($digits[$index]) - 48);
            $digit = intdiv($number, $divisor);
            if ($quotient !== '' || $digit !== 0) {
                $quotient .= (string) $digit;
            }
            $remainder = $number % $divisor;
        }
        return [$quotient === '' ? '0' : $quotient, $remainder];
    }
}