/*
Crafter®.Network
Copyright (C) 2026 Catcrafts®
Catcrafts.net

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3.0 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
*/

// CRAFTER_NETWORK_BROWSER implementation of ClientHTTP. Each SendAsync
// hands its request to the JS bridge (additional/network-env.js), which
// runs a fetch() and dispatches the result back through the
// CrafterNetworkOnFetchComplete / CrafterNetworkOnFetchError wasm exports.

module;
module Crafter.Network:ClientHTTP_impl;
import :ClientHTTP;
import :HTTP;
import std;

using namespace Crafter;

namespace Crafter::NetworkBrowserBindings {
    // External linkage so the import_module/import_name attributes wire up.
    __attribute__((import_module("env"), import_name("crafterNetworkFetch")))
    void crafterNetworkFetch(
        const char* method, std::int32_t methodLen,
        const char* url, std::int32_t urlLen,
        const char* headers, std::int32_t headersLen,
        const char* body, std::int32_t bodyLen,
        std::int32_t callbackId);
}

namespace {
    struct FetchCallbacks {
        std::function<void(HTTPResponse)> onSuccess;
        std::function<void(std::string)> onError;
    };

    // JS dispatches back into wasm via a stable id we mint here. The id
    // counter is monotone — wraparound at 2 billion fetches is not a
    // realistic concern. The map is touched only from the JS event loop
    // (single-threaded in the browser), so no synchronisation is needed.
    std::unordered_map<std::int32_t, FetchCallbacks>& Callbacks() {
        static std::unordered_map<std::int32_t, FetchCallbacks> m;
        return m;
    }
    std::int32_t NextId() {
        static std::int32_t counter = 0;
        return ++counter;
    }

    // Serialise headers as newline-separated "name: value" pairs. The JS
    // side splits on '\n' and the first ": " for header construction.
    std::string SerialiseHeaders(const std::unordered_map<std::string, std::string>& headers) {
        std::string out;
        bool first = true;
        for (const auto& [name, value] : headers) {
            if (!first) out += '\n';
            first = false;
            out += name;
            out += ": ";
            out += value;
        }
        return out;
    }

    // Parse a "name: value\nname2: value2" blob into the HTTPResponse map.
    // Names are kept verbatim (fetch surfaces them lowercase already on the
    // browser side via response.headers.forEach).
    void ParseHeaders(std::string_view raw, HTTPResponse& response) {
        std::size_t pos = 0;
        while (pos < raw.size()) {
            std::size_t end = raw.find('\n', pos);
            std::string_view line = raw.substr(pos, end == std::string_view::npos ? raw.size() - pos : end - pos);
            std::size_t sep = line.find(": ");
            if (sep != std::string_view::npos) {
                response.headers.emplace(std::string(line.substr(0, sep)),
                                         std::string(line.substr(sep + 2)));
            }
            if (end == std::string_view::npos) break;
            pos = end + 1;
        }
    }
}

struct ClientHTTP::Impl {};

ClientHTTP::ClientHTTP(const char* host, std::uint16_t port, QUICClientCredentials)
    : host(host), port(port), impl(std::make_unique<Impl>()) {}

ClientHTTP::ClientHTTP(std::string host, std::uint16_t port, QUICClientCredentials creds)
    : ClientHTTP(host.c_str(), port, std::move(creds)) {}

ClientHTTP::ClientHTTP(ClientHTTP&&) noexcept = default;
ClientHTTP::~ClientHTTP() = default;

void ClientHTTP::SendAsync(const HTTPRequest& request,
                           std::function<void(HTTPResponse)> onSuccess,
                           std::function<void(std::string)> onError) {
    std::int32_t id = NextId();
    Callbacks().emplace(id, FetchCallbacks{std::move(onSuccess), std::move(onError)});

    std::string method    = request.method.empty()    ? std::string("GET")   : request.method;
    std::string path      = request.path.empty()      ? std::string("/")     : request.path;
    // Sentinel: a ClientHTTP constructed with an empty host fetches against
    // the page's own origin. fetch(url) in JS handles a leading-slash path
    // by resolving it against window.location, so we just hand the path
    // straight through. Useful for fetching files served by whatever static
    // server is hosting the wasm (e.g. ./cert-hash.txt for WebTransport).
    std::string url;
    if (host.empty()) {
        url = path;
    } else {
        std::string scheme    = request.scheme.empty()    ? std::string("https") : request.scheme;
        std::string authority = request.authority.empty() ? (host + ":" + std::to_string(port)) : request.authority;
        url = scheme + "://" + authority + path;
    }
    std::string headerStr = SerialiseHeaders(request.headers);

    Crafter::NetworkBrowserBindings::crafterNetworkFetch(
        method.data(),    static_cast<std::int32_t>(method.size()),
        url.data(),       static_cast<std::int32_t>(url.size()),
        headerStr.data(), static_cast<std::int32_t>(headerStr.size()),
        request.body.data(), static_cast<std::int32_t>(request.body.size()),
        id);
}

extern "C" {
    // JS allocates `headersPtr` and `bodyPtr` via WasmAlloc, copies the
    // response into them, then transfers ownership across this call. We
    // free the buffers after copying into the HTTPResponse.
    __attribute__((export_name("CrafterNetworkOnFetchComplete")))
    void CrafterNetworkOnFetchComplete(std::int32_t callbackId,
                                       std::int32_t status,
                                       char* headersPtr, std::int32_t headersLen,
                                       char* bodyPtr,    std::int32_t bodyLen) {
        auto& callbacks = Callbacks();
        auto it = callbacks.find(callbackId);
        if (it == callbacks.end()) {
            std::free(headersPtr);
            std::free(bodyPtr);
            return;
        }

        HTTPResponse response;
        response.status = std::to_string(status);
        if (headersPtr && headersLen > 0) {
            ParseHeaders(std::string_view(headersPtr, static_cast<std::size_t>(headersLen)), response);
        }
        if (bodyPtr && bodyLen > 0) {
            response.body.assign(bodyPtr, static_cast<std::size_t>(bodyLen));
        }
        std::free(headersPtr);
        std::free(bodyPtr);

        auto onSuccess = std::move(it->second.onSuccess);
        callbacks.erase(it);
        if (onSuccess) onSuccess(std::move(response));
    }

    __attribute__((export_name("CrafterNetworkOnFetchError")))
    void CrafterNetworkOnFetchError(std::int32_t callbackId,
                                    char* messagePtr, std::int32_t messageLen) {
        auto& callbacks = Callbacks();
        auto it = callbacks.find(callbackId);
        if (it == callbacks.end()) {
            std::free(messagePtr);
            return;
        }
        std::string msg(messagePtr ? messagePtr : "", static_cast<std::size_t>(messageLen));
        std::free(messagePtr);

        auto onError = std::move(it->second.onError);
        callbacks.erase(it);
        if (onError) onError(std::move(msg));
    }

    // WasmAlloc / WasmFree are the buffer-marshalling primitives the JS
    // bridge calls into. Crafter.Graphics's Dom backend defines the same
    // pair; we mark ours weak so the two libraries can coexist in one
    // executable without a duplicate-symbol error.
    __attribute__((export_name("WasmAlloc"), weak))
    void* WasmAlloc(std::int32_t size) { return std::malloc(static_cast<std::size_t>(size)); }

    __attribute__((export_name("WasmFree"), weak))
    void WasmFree(void* ptr) { std::free(ptr); }
}