#include "nocal/sync/desktop_oauth.hpp"

#include <array>
#include <cerrno>
#include <chrono>
#include <cstdint>
#include <cstdlib>
#include <filesystem>
#include <fstream>
#include <functional>
#include <iostream>
#include <iterator>
#include <stdexcept>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

namespace {

using namespace std::chrono_literals;
using nocal::sync::AuthorizationCallback;
using nocal::sync::LoopbackCallbackReceiver;
using nocal::sync::XdgBrowserLauncher;

void require(bool condition, std::string_view message) {
    if (!condition) {
        throw std::runtime_error(std::string{message});
    }
}

template <typename Function>
void require_throws(Function&& function, std::string_view message) {
    try {
        function();
    } catch (const std::exception&) {
        return;
    }
    throw std::runtime_error(std::string{message});
}

class TempDirectory {
public:
    TempDirectory() {
        std::string pattern =
            (std::filesystem::temp_directory_path() / "nocal-desktop-oauth-tests.XXXXXX")
                .string();
        std::vector<char> writable(pattern.begin(), pattern.end());
        writable.push_back('\0');
        const char* created = ::mkdtemp(writable.data());
        if (created == nullptr) {
            throw std::runtime_error("mkdtemp failed");
        }
        path_ = created;
    }

    TempDirectory(const TempDirectory&) = delete;
    TempDirectory& operator=(const TempDirectory&) = delete;

    ~TempDirectory() {
        std::error_code ignored;
        std::filesystem::remove_all(path_, ignored);
    }

    [[nodiscard]] const std::filesystem::path& path() const noexcept { return path_; }

private:
    std::filesystem::path path_;
};

class Descriptor {
public:
    explicit Descriptor(int value = -1) : value_(value) {}
    ~Descriptor() {
        if (value_ >= 0) {
            static_cast<void>(::close(value_));
        }
    }

    Descriptor(const Descriptor&) = delete;
    Descriptor& operator=(const Descriptor&) = delete;
    Descriptor(Descriptor&& other) noexcept : value_(std::exchange(other.value_, -1)) {}

    Descriptor& operator=(Descriptor&& other) noexcept {
        if (this != &other) {
            if (value_ >= 0) {
                static_cast<void>(::close(value_));
            }
            value_ = std::exchange(other.value_, -1);
        }
        return *this;
    }

    [[nodiscard]] int get() const noexcept { return value_; }

private:
    int value_;
};

[[nodiscard]] std::string read_file(const std::filesystem::path& path) {
    std::ifstream input(path, std::ios::binary);
    require(static_cast<bool>(input), "could not read browser helper output");
    return {std::istreambuf_iterator<char>{input}, {}};
}

[[nodiscard]] std::string self_executable() {
    return std::filesystem::read_symlink("/proc/self/exe").string();
}

void set_helper_output(const std::filesystem::path& path) {
    require(::setenv("NOCAL_DESKTOP_OAUTH_HELPER_OUTPUT", path.c_str(), 1) == 0,
        "could not configure browser helper output");
}

int run_browser_helper(int argc, char** argv) {
    const char* output_path = std::getenv("NOCAL_DESKTOP_OAUTH_HELPER_OUTPUT");
    if (output_path == nullptr) {
        return 91;
    }
    std::ofstream output(output_path, std::ios::binary | std::ios::trunc);
    output << argc << '\n';
    for (int index = 0; index < argc; ++index) {
        output << argv[index] << '\n';
    }
    if (!output) {
        return 92;
    }
    return argc == 2 && std::string_view{argv[1]}.starts_with("browser-helper:exit=7") ? 7 : 0;
}

void test_browser_literal_argv_and_failures(const std::filesystem::path& root) {
    const auto helper_output = root / "browser-argv.txt";
    const auto injection_target = root / "must-not-exist";
    set_helper_output(helper_output);
    XdgBrowserLauncher launcher{self_executable()};
    const std::string url = "browser-helper:exit=0; literal argument; touch "
        + injection_target.string() + "; $(touch " + injection_target.string() + ")";
    launcher.open(url);
    const std::string report = read_file(helper_output);
    require(report.starts_with("2\n"), "browser helper received more than one URL argument");
    require(report.ends_with(url + "\n"), "browser helper did not receive the URL literally");
    require(!std::filesystem::exists(injection_target), "browser URL was interpreted by a shell");

    const std::string sensitive = "SENSITIVE_BROWSER_URL";
    try {
        launcher.open("browser-helper:exit=7;" + sensitive);
        throw std::runtime_error("nonzero browser exit was accepted");
    } catch (const std::exception& error) {
        require(std::string_view{error.what()}.find(sensitive) == std::string_view::npos,
            "browser URL leaked through an exception");
    }

    require_throws([] { XdgBrowserLauncher invalid{""}; },
        "empty browser executable was accepted");
    require_throws(
        [] { XdgBrowserLauncher invalid{std::string{"browser\0name", 12}}; },
        "browser executable containing NUL was accepted");
    require_throws(
        [] {
            XdgBrowserLauncher missing{"nocal-browser-executable-that-does-not-exist"};
            missing.open("https://example.test");
        },
        "missing browser executable was accepted");

    for (const std::string& invalid_url : {
             std::string{"https://example.test/\0secret", 28},
             std::string{"https://example.test/\nsecret"},
             std::string{"https://example.test/\rsecret"},
             std::string{"https://example.test/\x7fsecret"},
         }) {
        require_throws([&] { launcher.open(invalid_url); },
            "browser URL containing a control character was accepted");
    }
}

[[nodiscard]] unsigned int port_from_uri(std::string_view uri) {
    constexpr std::string_view prefix = "http://localhost:";
    constexpr std::string_view suffix = "/nocal/oauth/callback";
    require(uri.starts_with(prefix) && uri.ends_with(suffix),
        "loopback redirect URI has the wrong shape");
    const std::string_view encoded = uri.substr(prefix.size(), uri.size() - prefix.size() - suffix.size());
    require(!encoded.empty(), "loopback redirect URI has no port");
    unsigned int port = 0;
    for (const char character : encoded) {
        require(character >= '0' && character <= '9', "loopback redirect port is not numeric");
        port = port * 10U + static_cast<unsigned int>(character - '0');
    }
    require(port > 0 && port <= 65'535, "loopback redirect port is out of range");
    return port;
}

[[nodiscard]] Descriptor connect_ipv4(unsigned int port) {
    Descriptor client{::socket(AF_INET, SOCK_STREAM, 0)};
    require(client.get() >= 0, "could not create loopback test socket");
    sockaddr_in address{};
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    address.sin_port = htons(static_cast<std::uint16_t>(port));
    require(::connect(client.get(), reinterpret_cast<const sockaddr*>(&address), sizeof(address))
            == 0,
        "could not connect to loopback receiver");
    return client;
}

[[nodiscard]] bool can_connect_ipv4(unsigned int port) {
    Descriptor client{::socket(AF_INET, SOCK_STREAM, 0)};
    if (client.get() < 0) {
        return false;
    }
    sockaddr_in address{};
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    address.sin_port = htons(static_cast<std::uint16_t>(port));
    return ::connect(client.get(), reinterpret_cast<const sockaddr*>(&address), sizeof(address))
        == 0;
}

[[nodiscard]] bool can_connect_ipv6(unsigned int port) {
    Descriptor client{::socket(AF_INET6, SOCK_STREAM, 0)};
    if (client.get() < 0) {
        return false;
    }
    sockaddr_in6 address{};
    address.sin6_family = AF_INET6;
    address.sin6_addr = in6addr_loopback;
    address.sin6_port = htons(static_cast<std::uint16_t>(port));
    return ::connect(client.get(), reinterpret_cast<const sockaddr*>(&address), sizeof(address))
        == 0;
}

void send_bytes(int descriptor, std::string_view bytes) {
    std::size_t offset = 0;
    while (offset < bytes.size()) {
        const ssize_t sent =
            ::send(descriptor, bytes.data() + offset, bytes.size() - offset, MSG_NOSIGNAL);
        if (sent < 0 && errno == EINTR) {
            continue;
        }
        require(sent > 0, "failed to send loopback test request");
        offset += static_cast<std::size_t>(sent);
    }
}

void send_all(int descriptor, std::string_view bytes) {
    send_bytes(descriptor, bytes);
    require(::shutdown(descriptor, SHUT_WR) == 0, "failed to finish loopback test request");
}

[[nodiscard]] std::string read_response(int descriptor) {
    std::string result;
    std::array<char, 1024> buffer{};
    while (true) {
        const ssize_t received = ::recv(descriptor, buffer.data(), buffer.size(), 0);
        if (received > 0) {
            result.append(buffer.data(), static_cast<std::size_t>(received));
        } else if (received == 0) {
            return result;
        } else if (errno == ECONNRESET && !result.empty()) {
            return result;
        } else if (errno != EINTR) {
            throw std::runtime_error("failed to read loopback HTTP response");
        }
    }
}

[[nodiscard]] std::string request_for(unsigned int port, std::string_view target,
    std::string_view method = "GET", std::string_view extra_headers = {}) {
    return std::string{method} + " " + std::string{target} + " HTTP/1.1\r\nHost: localhost:"
        + std::to_string(port) + "\r\n" + std::string{extra_headers} + "\r\n";
}

struct ExchangeResult {
    AuthorizationCallback callback;
    std::string response;
};

[[nodiscard]] ExchangeResult valid_exchange(
    LoopbackCallbackReceiver& receiver, std::string_view query) {
    const unsigned int port = port_from_uri(receiver.redirect_uri());
    Descriptor client = connect_ipv4(port);
    send_all(client.get(), request_for(port, std::string{"/nocal/oauth/callback?"} + std::string{query}));
    AuthorizationCallback callback = receiver.receive();
    return {std::move(callback), read_response(client.get())};
}

[[nodiscard]] std::string invalid_exchange(
    LoopbackCallbackReceiver& receiver, const std::string& request) {
    const unsigned int port = port_from_uri(receiver.redirect_uri());
    Descriptor client = connect_ipv4(port);
    send_all(client.get(), request);
    require_throws([&] { static_cast<void>(receiver.receive()); },
        "invalid loopback request was accepted");
    return read_response(client.get());
}

void require_success_response(std::string_view response) {
    require(response.starts_with("HTTP/1.1 200 OK\r\n"),
        "valid callback did not receive HTTP 200");
    require(response.find("Cache-Control: no-store") != std::string_view::npos,
        "valid callback response is cacheable");
}

void require_failure_response(std::string_view response) {
    require(response.starts_with("HTTP/1.1 400 Bad Request\r\n"),
        "invalid callback did not receive HTTP 400");
    require(response.find("Cache-Control: no-store") != std::string_view::npos,
        "invalid callback response is cacheable");
    require(response.find("SENSITIVE_CALLBACK") == std::string_view::npos,
        "invalid callback response reflected request data");
}

void test_redirect_and_parsed_callbacks() {
    LoopbackCallbackReceiver success{1s};
    const unsigned int port = port_from_uri(success.redirect_uri());
    require(!can_connect_ipv6(port), "loopback receiver unexpectedly listens on IPv6");
    const auto accepted =
        valid_exchange(success, "code=abc%2Bdef&state=state+with+spaces&session_state=ignored");
    require(accepted.callback.code == "abc+def" && accepted.callback.state == "state with spaces",
        "successful callback query was not decoded correctly");
    require(accepted.callback.error.empty() && accepted.callback.error_description.empty(),
        "unknown callback field contaminated known fields");
    require_success_response(accepted.response);

    LoopbackCallbackReceiver denied{1s};
    const auto rejected = valid_exchange(denied,
        "error=access_denied&error_description=User+cancelled&state=state-2&unknown=value");
    require(rejected.callback.code.empty() && rejected.callback.error == "access_denied"
            && rejected.callback.error_description == "User cancelled"
            && rejected.callback.state == "state-2",
        "authorization error callback was not decoded correctly");
    require_success_response(rejected.response);

    LoopbackCallbackReceiver uppercase_host{1s};
    const unsigned int uppercase_port = port_from_uri(uppercase_host.redirect_uri());
    Descriptor uppercase_client = connect_ipv4(uppercase_port);
    send_all(uppercase_client.get(),
        "GET /nocal/oauth/callback?code=upper&state=case HTTP/1.1\r\nhOsT: LOCALHOST:"
            + std::to_string(uppercase_port) + "\r\n\r\n");
    const auto uppercase_callback = uppercase_host.receive();
    require(uppercase_callback.code == "upper" && uppercase_callback.state == "case",
        "ASCII-case-insensitive localhost Host was rejected");
    require_success_response(read_response(uppercase_client.get()));
}

void test_invalid_http_matrix() {
    auto run = [](const std::function<std::string(unsigned int)>& build) {
        LoopbackCallbackReceiver receiver{1s};
        const unsigned int port = port_from_uri(receiver.redirect_uri());
        const std::string response = invalid_exchange(receiver, build(port));
        require_failure_response(response);
        require(!can_connect_ipv4(port), "invalid callback left listener open");
    };

    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=x&state=y", "POST");
    });
    run([](unsigned int port) {
        return request_for(port, "/wrong?code=x&state=y");
    });
    run([](unsigned int port) {
        return "GET /nocal/oauth/callback?code=x&state=y HTTP/1.0\r\nHost: localhost:"
            + std::to_string(port) + "\r\n\r\n";
    });
    run([](unsigned int) {
        return std::string{"GET /nocal/oauth/callback?code=x&state=y HTTP/1.1\r\n\r\n"};
    });
    run([](unsigned int port) {
        return "GET /nocal/oauth/callback?code=x&state=y HTTP/1.1\r\nHost: 127.0.0.1:"
            + std::to_string(port) + "\r\n\r\n";
    });
    run([](unsigned int port) {
        return "GET /nocal/oauth/callback?code=x&state=y HTTP/1.1\r\nHost: localhost.:"
            + std::to_string(port) + "\r\n\r\n";
    });
    run([](unsigned int port) {
        return "GET /nocal/oauth/callback?code=x&state=y HTTP/1.1\r\nHost: localhost.evil:"
            + std::to_string(port) + "\r\n\r\n";
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=x&state=y",
            "GET", "Host: localhost:" + std::to_string(port) + "\r\n");
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=x&state=y", "GET", "Broken\r\n");
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=x&state=y", "GET",
            std::string{"X-"} + "\xC3\xA9" + ": value\r\n");
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=x&state=y", "GET",
            "Transfer-Encoding: chunked\r\n");
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=x&state=y", "GET",
                   "Content-Length: 1\r\n")
            + "x";
    });
    run([](unsigned int port) {
        return request_for(
            port, "/nocal/oauth/callback?code=SENSITIVE_CALLBACK&state=y&state=z");
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=%GG&state=y");
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=%00&state=y");
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=%1F&state=y");
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code&state=y");
    });
    run([](unsigned int port) {
        std::string target = "/nocal/oauth/callback?code=x&state=y";
        target.push_back('\0');
        return request_for(port, target);
    });
    run([](unsigned int port) {
        return request_for(port, "/nocal/oauth/callback?code=x&state=y", "GET",
            "X-Large: " + std::string(17U * 1024U, 'a') + "\r\n");
    });
    run([](unsigned int port) {
        return "GET /nocal/oauth/callback?code=x&state=y HTTP/1.1\nHost: localhost:"
            + std::to_string(port) + "\n\n";
    });
}

void test_timeout_single_use_and_cleanup() {
    require_throws([] { LoopbackCallbackReceiver invalid{0ms}; },
        "zero loopback timeout was accepted");
    require_throws([] { LoopbackCallbackReceiver invalid{-1ms}; },
        "negative loopback timeout was accepted");

    LoopbackCallbackReceiver timed{20ms};
    const unsigned int timed_port = port_from_uri(timed.redirect_uri());
    require_throws([&] { static_cast<void>(timed.receive()); },
        "loopback receiver did not time out");
    require(!can_connect_ipv4(timed_port), "timed-out receiver left listener open");
    require_throws([&] { static_cast<void>(timed.receive()); },
        "timed-out receiver was reusable");

    LoopbackCallbackReceiver partial{20ms};
    const unsigned int partial_port = port_from_uri(partial.redirect_uri());
    Descriptor partial_client = connect_ipv4(partial_port);
    send_bytes(partial_client.get(),
        "GET /nocal/oauth/callback?code=x&state=y HTTP/1.1\r\nHost: localhost:");
    require_throws([&] { static_cast<void>(partial.receive()); },
        "partial callback did not obey the total deadline");
    require_failure_response(read_response(partial_client.get()));
    require(!can_connect_ipv4(partial_port), "partial timeout left listener open");

    LoopbackCallbackReceiver used{1s};
    const unsigned int used_port = port_from_uri(used.redirect_uri());
    static_cast<void>(valid_exchange(used, "code=x&state=y"));
    require_throws([&] { static_cast<void>(used.receive()); },
        "completed receiver was reusable");
    require(!can_connect_ipv4(used_port), "completed receiver left listener open");

    unsigned int destroyed_port = 0;
    {
        LoopbackCallbackReceiver destroyed{1s};
        destroyed_port = port_from_uri(destroyed.redirect_uri());
    }
    require(!can_connect_ipv4(destroyed_port), "destroyed receiver left listener open");
}

void test_move_safety_and_cleanup() {
    LoopbackCallbackReceiver source{1s};
    const std::string uri = source.redirect_uri();
    LoopbackCallbackReceiver moved{std::move(source)};
    require(moved.redirect_uri() == uri, "move construction changed redirect URI");
    require_throws([&] { static_cast<void>(source.redirect_uri()); },
        "moved-from receiver remained usable");
    static_cast<void>(valid_exchange(moved, "code=moved&state=state"));

    LoopbackCallbackReceiver assignment_source{1s};
    const std::string assigned_uri = assignment_source.redirect_uri();
    LoopbackCallbackReceiver assignment_target{1s};
    const unsigned int replaced_port = port_from_uri(assignment_target.redirect_uri());
    assignment_target = std::move(assignment_source);
    require(assignment_target.redirect_uri() == assigned_uri,
        "move assignment changed redirect URI");
    require(!can_connect_ipv4(replaced_port),
        "move assignment did not close the replaced listener");
    require_throws([&] { static_cast<void>(assignment_source.redirect_uri()); },
        "move-assigned source remained usable");
    static_cast<void>(valid_exchange(assignment_target, "error=denied&state=state"));
}

} // namespace

int main(int argc, char** argv) {
    if (argc >= 2 && std::string_view{argv[1]}.starts_with("browser-helper:")) {
        return run_browser_helper(argc, argv);
    }
    try {
        TempDirectory temporary;
        test_browser_literal_argv_and_failures(temporary.path());
        test_redirect_and_parsed_callbacks();
        test_invalid_http_matrix();
        test_timeout_single_use_and_cleanup();
        test_move_safety_and_cleanup();
    } catch (const std::exception& error) {
        std::cerr << "desktop OAuth test failure: " << error.what() << '\n';
        return 1;
    }
    std::cout << "desktop OAuth tests passed\n";
    return 0;
}