// SPDX-License-Identifier: LGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

module Crafter.Debug.Core:Protocol_impl;
import std;
import :Value;
import :Protocol;

using namespace Crafter::Debug;

namespace {
    constexpr std::string_view alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    std::int32_t Sextet(char c) {
        if (c >= 'A' && c <= 'Z') return c - 'A';
        if (c >= 'a' && c <= 'z') return c - 'a' + 26;
        if (c >= '0' && c <= '9') return c - '0' + 52;
        if (c == '+') return 62;
        if (c == '/') return 63;
        return -1;
    }
}

Value Crafter::Debug::MakeReply(Value result) {
    Value reply = Value::MakeObject();
    reply.Set("result", std::move(result));
    return reply;
}

Value Crafter::Debug::MakeErrorReply(std::string_view code, std::string_view message) {
    Value error = Value::MakeObject();
    error.Set("code", Value(code));
    error.Set("message", Value(message));
    Value reply = Value::MakeObject();
    reply.Set("error", std::move(error));
    return reply;
}

std::string Crafter::Debug::Base64Encode(std::span<const std::byte> bytes) {
    std::string out;
    out.reserve((bytes.size() + 2) / 3 * 4);
    std::size_t i = 0;
    for (; i + 3 <= bytes.size(); i += 3) {
        const std::uint32_t chunk = (std::to_integer<std::uint32_t>(bytes[i]) << 16) | (std::to_integer<std::uint32_t>(bytes[i + 1]) << 8) | std::to_integer<std::uint32_t>(bytes[i + 2]);
        out += alphabet[(chunk >> 18) & 63];
        out += alphabet[(chunk >> 12) & 63];
        out += alphabet[(chunk >> 6) & 63];
        out += alphabet[chunk & 63];
    }
    const std::size_t rest = bytes.size() - i;
    if (rest == 1) {
        const std::uint32_t chunk = std::to_integer<std::uint32_t>(bytes[i]) << 16;
        out += alphabet[(chunk >> 18) & 63];
        out += alphabet[(chunk >> 12) & 63];
        out += "==";
    } else if (rest == 2) {
        const std::uint32_t chunk = (std::to_integer<std::uint32_t>(bytes[i]) << 16) | (std::to_integer<std::uint32_t>(bytes[i + 1]) << 8);
        out += alphabet[(chunk >> 18) & 63];
        out += alphabet[(chunk >> 12) & 63];
        out += alphabet[(chunk >> 6) & 63];
        out += '=';
    }
    return out;
}

std::optional<std::vector<std::byte>> Crafter::Debug::Base64Decode(std::string_view text) {
    if (text.size() % 4 != 0) return std::nullopt;
    std::vector<std::byte> out;
    out.reserve(text.size() / 4 * 3);
    for (std::size_t i = 0; i < text.size(); i += 4) {
        const bool last = i + 4 == text.size();
        const std::int32_t a = Sextet(text[i]);
        const std::int32_t b = Sextet(text[i + 1]);
        const bool pad2 = last && text[i + 2] == '=';
        const bool pad3 = last && text[i + 3] == '=';
        const std::int32_t c = pad2 ? 0 : Sextet(text[i + 2]);
        const std::int32_t d = pad3 ? 0 : Sextet(text[i + 3]);
        if (a < 0 || b < 0 || c < 0 || d < 0 || (pad2 && !pad3)) return std::nullopt;
        const std::uint32_t chunk = (static_cast<std::uint32_t>(a) << 18) | (static_cast<std::uint32_t>(b) << 12) | (static_cast<std::uint32_t>(c) << 6) | static_cast<std::uint32_t>(d);
        out.push_back(static_cast<std::byte>((chunk >> 16) & 0xFF));
        if (!pad2) out.push_back(static_cast<std::byte>((chunk >> 8) & 0xFF));
        if (!pad3) out.push_back(static_cast<std::byte>(chunk & 0xFF));
    }
    return out;
}