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

// Interop against implementations that are not this library — the whole
// point of shipping HTTP/1.1 in the first place.
//
//   * curl drives ListenerHTTP1: keep-alive reuse, chunked upload,
//     Expect: 100-continue, HEAD, and a plain GET.
//   * ClientHTTP1 drives python3's http.server, which answers HTTP/1.0 with
//     `Connection: close` — the legacy shape our own listener never emits.
//
// Both peers are optional: if curl or python3 is missing the corresponding
// half is skipped rather than failed, so the suite still runs on a bare
// machine.

#include <signal.h>
#include <unistd.h>
#include <sys/wait.h>
#include <stdio.h>

import Crafter.Network;
import std;
using namespace Crafter;

namespace {
    int failures = 0;

    void Check(bool condition, std::string_view what) {
        if (!condition) {
            std::println("FAIL: {}", what);
            ++failures;
        }
    }

    bool HaveCommand(std::string_view name) {
        const std::string probe = "command -v " + std::string(name) + " >/dev/null 2>&1";
        return std::system(probe.c_str()) == 0;
    }

    // Run a command and return its stdout. stderr is folded in so a curl
    // failure explains itself in the test output.
    std::string Run(const std::string& command) {
        std::string output;
        FILE* pipe = popen((command + " 2>&1").c_str(), "r");
        if (pipe == nullptr) return output;
        char buffer[4096];
        while (std::size_t read = std::fread(buffer, 1, sizeof(buffer), pipe)) {
            output.append(buffer, read);
        }
        pclose(pipe);
        return output;
    }

    // A child process, killed when this goes out of scope.
    class Child {
    public:
        explicit Child(std::vector<std::string> argv) {
            std::vector<char*> raw;
            for (auto& argument : argv) raw.push_back(argument.data());
            raw.push_back(nullptr);
            pid = fork();
            if (pid == 0) {
                // Keep the test output clean; the child's chatter is not
                // interesting unless it fails to start, which shows up as a
                // connection failure instead.
                freopen("/dev/null", "w", stdout);
                freopen("/dev/null", "w", stderr);
                execvp(raw[0], raw.data());
                _exit(127);
            }
        }
        ~Child() {
            if (pid > 0) {
                kill(pid, SIGTERM);
                int status = 0;
                waitpid(pid, &status, 0);
            }
        }
        Child(const Child&) = delete;
        bool Started() const { return pid > 0; }

    private:
        pid_t pid = -1;
    };

    // Poll until something accepts on the port, so the test doesn't race a
    // slow-starting server.
    bool WaitForPort(std::uint16_t port, std::chrono::milliseconds budget) {
        const auto deadline = std::chrono::steady_clock::now() + budget;
        while (std::chrono::steady_clock::now() < deadline) {
            try {
                ClientTCP probe("localhost", port);
                return true;
            } catch (const std::exception&) {
                std::this_thread::sleep_for(std::chrono::milliseconds(25));
            }
        }
        return false;
    }

    void CurlAgainstListener() {
        if (!HaveCommand("curl")) {
            std::println("skipping the curl half: curl is not installed");
            return;
        }

        std::unordered_map<std::string, std::function<HTTPResponse(const HTTPRequest&)>> routes;
        routes["/hello"] = [](const HTTPRequest&) {
            return CreateResponseHTTP("200", {{"content-type", "text/plain"}}, "Hello curl!");
        };
        routes["/echo"] = [](const HTTPRequest& request) {
            return CreateResponseHTTP("200", request.method + ":" + request.body);
        };
        routes["/agent"] = [](const HTTPRequest& request) {
            auto agent = request.headers.find("user-agent");
            return CreateResponseHTTP("200", agent == request.headers.end() ? "none" : agent->second);
        };

        ListenerAsyncHTTP1 listener(8093, std::move(routes));
        Check(WaitForPort(8093, std::chrono::seconds(2)), "the HTTP/1.1 listener came up");

        const std::string base = "http://localhost:8093";

        Check(Run("curl -sS --http1.1 " + base + "/hello") == "Hello curl!", "curl GET");

        // Two URLs in one invocation: curl reuses the connection, which
        // only works if our framing let it know the first response ended.
        const std::uint64_t before = listener.listener.AcceptedCount();
        const std::string both = Run("curl -sS --http1.1 " + base + "/hello " + base + "/hello");
        Check(both == "Hello curl!Hello curl!", "curl got both responses");
        Check(listener.listener.AcceptedCount() == before + 1, "curl reused one connection for both");

        Check(Run("curl -sS --http1.1 -d 'body text' " + base + "/echo") == "POST:body text",
              "curl POST with content-length");

        // Chunked upload — curl streams stdin with Transfer-Encoding:
        // chunked when it can't know the length up front.
        Check(Run("printf 'streamed body' | curl -sS --http1.1 -H 'Transfer-Encoding: chunked' "
                  "--data-binary @- " + base + "/echo") == "POST:streamed body",
              "curl chunked upload");

        // A body over 1 KiB makes curl wait for `100 Continue` before it
        // sends anything. Run it verbosely so the trace proves the interim
        // response actually went out — without it curl still recovers after
        // a one-second stall, which would hide the bug.
        const std::string large(64 * 1024, 'x');
        const std::string upload =
            "head -c 65536 /dev/zero | tr '\\0' 'x' | curl -sS --http1.1 "
            "-H 'Expect: 100-continue' --data-binary @- " + base + "/echo";
        // The trace goes to stderr and the body to stdout; keeping them in
        // separate runs avoids the two streams interleaving in the pipe.
        Check(Run(upload + " -v -o /dev/null").find("HTTP/1.1 100 Continue") != std::string::npos,
              "curl saw the interim 100 Continue");
        Check(Run(upload) == "POST:" + large, "curl Expect: 100-continue upload arrived intact");

        // HEAD must produce the GET headers and no body.
        const std::string head = Run("curl -sS --http1.1 -I " + base + "/hello");
        Check(head.find("HTTP/1.1 200 OK") != std::string::npos, "curl HEAD status line");
        Check(head.find("content-length: 11") != std::string::npos, "curl HEAD keeps content-length");
        Check(head.find("Hello curl!") == std::string::npos, "curl HEAD carries no body");

        Check(Run("curl -sS --http1.1 -A 'crafter-test/1.0' " + base + "/agent") == "crafter-test/1.0",
              "request headers reach the handler");

        // The status line has to be readable by a real client, not just by
        // our own parser.
        Check(Run("curl -sS --http1.1 -o /dev/null -w '%{http_code}' " + base + "/missing") == "404",
              "curl reads the 404 status");

        listener.Stop();
    }

    void ClientAgainstPythonServer() {
        if (!HaveCommand("python3")) {
            std::println("skipping the python half: python3 is not installed");
            return;
        }

        const std::filesystem::path root =
            std::filesystem::temp_directory_path() / "crafter-network-http1-interop";
        std::filesystem::create_directories(root);
        const std::string content = "served by python\n";
        {
            std::ofstream file(root / "hello.txt", std::ios::binary);
            file << content;
        }

        // http.server answers HTTP/1.0 with `Connection: close`: every
        // request needs its own connection, and the client has to notice.
        Child server({"python3", "-m", "http.server", "8094", "--bind", "127.0.0.1",
                      "--directory", root.string()});
        Check(server.Started(), "python3 http.server was spawned");
        if (!WaitForPort(8094, std::chrono::seconds(10))) {
            std::println("skipping the python half: http.server never came up");
            return;
        }

        ClientHTTP1 client("localhost", 8094);
        HTTPResponse response = client.Send(CreateRequestHTTP("GET", "/hello.txt", "localhost:8094"));
        Check(response.status == "200", "python GET status");
        Check(response.body == content, "python GET body");
        Check(!client.Connected(), "an HTTP/1.0 response closes the connection");

        HTTPResponse listing = client.Send(CreateRequestHTTP("GET", "/", "localhost:8094"));
        Check(listing.status == "200", "python directory listing status");
        Check(listing.body.find("hello.txt") != std::string::npos, "python directory listing body");

        HTTPResponse missing = client.Send(CreateRequestHTTP("GET", "/nothing-here", "localhost:8094"));
        Check(missing.status == "404", "python 404");

        HTTPResponse head = client.Send(CreateRequestHTTP("HEAD", "/hello.txt", "localhost:8094"));
        Check(head.status == "200", "python HEAD status");
        Check(head.body.empty(), "python HEAD has no body");

        std::filesystem::remove_all(root);
    }
}

int main() {
    try {
        CurlAgainstListener();
        ClientAgainstPythonServer();
    } catch (const std::exception& error) {
        std::println("threw: {}", error.what());
        return 1;
    }

    if (failures != 0) {
        std::println("{} check(s) failed", failures);
        return 1;
    }
    return 0;
}