#include "nocal/sync/oauth.hpp"

#include <algorithm>
#include <array>
#include <cstddef>
#include <exception>
#include <iostream>
#include <span>
#include <stdexcept>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

namespace {

using nocal::sync::AuthorizationCallback;
using nocal::sync::AuthorizationCallbackReceiver;
using nocal::sync::BrowserLauncher;
using nocal::sync::EntropySource;
using nocal::sync::HttpMethod;
using nocal::sync::HttpRequest;
using nocal::sync::HttpResponse;
using nocal::sync::HttpTransport;
using nocal::sync::OAuthClientConfig;
using nocal::sync::OAuthError;
using nocal::sync::authorize_with_pkce;

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

class ScriptedEntropy final : public EntropySource {
public:
    explicit ScriptedEntropy(std::vector<std::array<std::byte, 32>> scripted_values)
        : values(std::move(scripted_values)) {}

    std::vector<std::array<std::byte, 32>> values;
    std::size_t calls{0};
    std::size_t fail_at{static_cast<std::size_t>(-1)};

    void fill(std::span<std::byte> output) override {
        require(output.size() == 32, "entropy request was not exactly 32 bytes");
        const std::size_t call = calls++;
        if (call == fail_at) {
            throw std::runtime_error("entropy failure detail");
        }
        require(call < values.size(), "unexpected entropy request");
        std::copy(values[call].begin(), values[call].end(), output.begin());
    }
};

class RecordingBrowser final : public BrowserLauncher {
public:
    std::vector<std::string> urls;

    void open(const std::string& url) override { urls.push_back(url); }
};

class FixedReceiver final : public AuthorizationCallbackReceiver {
public:
    std::string redirect{"http://127.0.0.1:43123/callback"};
    AuthorizationCallback callback;
    std::size_t receives{0};

    [[nodiscard]] std::string redirect_uri() const override { return redirect; }

    AuthorizationCallback receive() override {
        ++receives;
        return callback;
    }
};

class RecordingTransport final : public HttpTransport {
public:
    std::vector<HttpRequest> requests;
    HttpResponse response{200, {}, "{\"access_token\":\"opaque\"}"};

    HttpResponse send(const HttpRequest& request) override {
        requests.push_back(request);
        return response;
    }
};

[[nodiscard]] OAuthClientConfig config() {
    return {"client id/+", "https://login.example/authorize", "https://login.example/token",
        {"openid", "Calendars.ReadWrite/test"}};
}

[[nodiscard]] std::array<std::byte, 32> zeros() { return {}; }

[[nodiscard]] int base64url_digit(char character) {
    if (character >= 'A' && character <= 'Z') {
        return character - 'A';
    }
    if (character >= 'a' && character <= 'z') {
        return character - 'a' + 26;
    }
    if (character >= '0' && character <= '9') {
        return character - '0' + 52;
    }
    if (character == '-') {
        return 62;
    }
    if (character == '_') {
        return 63;
    }
    throw std::runtime_error("invalid base64url test fixture");
}

[[nodiscard]] std::array<std::byte, 32> decode_verifier(std::string_view value) {
    std::vector<std::byte> decoded;
    unsigned int accumulator = 0;
    unsigned int bits = 0;
    for (const char character : value) {
        accumulator = (accumulator << 6U) | static_cast<unsigned int>(base64url_digit(character));
        bits += 6U;
        if (bits >= 8U) {
            bits -= 8U;
            decoded.push_back(static_cast<std::byte>((accumulator >> bits) & 0xffU));
        }
    }
    require(decoded.size() == 32, "RFC verifier fixture did not decode to 32 bytes");
    std::array<std::byte, 32> result{};
    std::copy(decoded.begin(), decoded.end(), result.begin());
    return result;
}

[[nodiscard]] std::string deterministic_state() {
    return "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
}

template <typename Action>
OAuthError expect_oauth_error(Action&& action, OAuthError::Kind kind) {
    try {
        action();
    } catch (const OAuthError& error) {
        require(error.kind() == kind, "OAuth error had the wrong kind");
        return error;
    }
    throw std::runtime_error("expected OAuthError was not thrown");
}

void test_rfc7636_vector_and_exact_exchange() {
    static constexpr std::string_view verifier =
        "dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk";
    ScriptedEntropy entropy{{zeros(), decode_verifier(verifier)}};
    RecordingBrowser browser;
    FixedReceiver receiver;
    receiver.callback = {"code +/&", deterministic_state(), "", ""};
    RecordingTransport transport;
    transport.response = {201, {{"Content-Type", "application/json"}}, "opaque token body"};

    const HttpResponse response =
        authorize_with_pkce(config(), browser, receiver, transport, entropy);

    require(response == transport.response, "successful token response was not returned unchanged");
    require(entropy.calls == 2, "OAuth attempt did not make exactly two entropy requests");
    require(browser.urls.size() == 1, "browser was not opened exactly once");
    require(receiver.receives == 1, "callback was not received exactly once");
    require(transport.requests.size() == 1, "token endpoint was not called exactly once");
    const std::string expected_url =
        "https://login.example/authorize?response_type=code&client_id=client%20id%2F%2B"
        "&redirect_uri=http%3A%2F%2F127.0.0.1%3A43123%2Fcallback"
        "&scope=openid%20Calendars.ReadWrite%2Ftest&state="
        + deterministic_state()
        + "&code_challenge=E9Melhoa2OwvFrEMTJguCHaoeK1t8URWbuGJSstw-cM"
          "&code_challenge_method=S256";
    require(browser.urls.front() == expected_url, "authorization URL was not exact RFC3986/PKCE");

    const HttpRequest& request = transport.requests.front();
    require(request.method == HttpMethod::post, "token exchange did not use POST");
    require(request.url == "https://login.example/token", "token endpoint changed");
    require(request.headers
            == std::vector<nocal::sync::HttpHeader>{{"Content-Type",
                                                       "application/x-www-form-urlencoded"},
                {"Accept", "application/json"}},
        "token request headers were not exact");
    const std::string expected_body =
        "grant_type=authorization_code&client_id=client%20id%2F%2B&code=code%20%2B%2F%26"
        "&redirect_uri=http%3A%2F%2F127.0.0.1%3A43123%2Fcallback&code_verifier="
        + std::string(verifier);
    require(request.body == expected_body, "token request form was not exact");
    require(request.body.find("client_secret") == std::string::npos,
        "token request contained a client secret");
    require(request.body.find("state=") == std::string::npos,
        "token request contained callback state");
}

void test_invalid_configurations_do_nothing() {
    std::vector<OAuthClientConfig> invalid;
    OAuthClientConfig value = config();
    value.client_id.clear();
    invalid.push_back(value);
    value = config();
    value.scopes.clear();
    invalid.push_back(value);
    value = config();
    value.scopes.push_back("");
    invalid.push_back(value);
    const std::vector<std::string> invalid_scopes = {"two scopes", "line\nbreak",
        "tab\tbreak", "quote\"", "backslash\\", std::string("nonascii-") + "\xC3\xAF"};
    for (const std::string& scope : invalid_scopes) {
        value = config();
        value.scopes = {scope};
        invalid.push_back(value);
    }
    for (const std::string endpoint : {"", "http://login.example/auth", "/authorize",
             "https://user@login.example/auth", "https://login.example/auth?prompt=login",
             "https://login.example/auth#fragment", "https://login.example/a path",
             "https:///authorize"}) {
        value = config();
        value.authorization_endpoint = endpoint;
        invalid.push_back(value);
        value = config();
        value.token_endpoint = endpoint;
        invalid.push_back(value);
    }

    for (const OAuthClientConfig& invalid_config : invalid) {
        ScriptedEntropy entropy{{zeros(), zeros()}};
        RecordingBrowser browser;
        FixedReceiver receiver;
        RecordingTransport transport;
        expect_oauth_error(
            [&] {
                (void)authorize_with_pkce(
                    invalid_config, browser, receiver, transport, entropy);
            },
            OAuthError::Kind::invalid_configuration);
        require(entropy.calls == 0 && browser.urls.empty() && receiver.receives == 0
                && transport.requests.empty(),
            "invalid configuration caused OAuth side effects");
    }
}

void test_redirect_validation() {
    const std::vector<std::string> invalid = {"", "https://localhost/callback",
        "http://example.com/callback", "http://localhost.example/callback",
        "http://127.0.0.2/callback", "http://user@localhost/callback",
        "http://localhost:0/callback", "http://localhost:65536/callback",
        "http://localhost:port/callback", "http://::1/callback",
        "http://[::1]evil/callback", "http://localhost/callback?code=x",
        "http://localhost/callback#fragment", "http://localhost/a path"};
    for (const std::string& redirect : invalid) {
        ScriptedEntropy entropy{{zeros(), zeros()}};
        RecordingBrowser browser;
        FixedReceiver receiver;
        receiver.redirect = redirect;
        RecordingTransport transport;
        expect_oauth_error(
            [&] {
                (void)authorize_with_pkce(config(), browser, receiver, transport, entropy);
            },
            OAuthError::Kind::invalid_redirect);
        require(entropy.calls == 0 && browser.urls.empty() && receiver.receives == 0
                && transport.requests.empty(),
            "invalid redirect caused OAuth side effects");
    }
}

void run_valid_redirect(std::string redirect) {
    ScriptedEntropy entropy{{zeros(), zeros()}};
    RecordingBrowser browser;
    FixedReceiver receiver;
    receiver.redirect = std::move(redirect);
    receiver.callback = {"code", deterministic_state(), "", ""};
    RecordingTransport transport;
    (void)authorize_with_pkce(config(), browser, receiver, transport, entropy);
    require(transport.requests.size() == 1, "valid loopback redirect was rejected");
}

void test_valid_loopback_redirects() {
    run_valid_redirect("http://localhost");
    run_valid_redirect("HTTP://LOCALHOST:65535/callback/path");
    run_valid_redirect("http://127.0.0.1:1/");
    run_valid_redirect("http://[::1]:43123/callback");
}

void test_non_ascii_encoding_and_upper_success_boundary() {
    ScriptedEntropy entropy{{zeros(), zeros()}};
    RecordingBrowser browser;
    FixedReceiver receiver;
    receiver.callback = {"code", deterministic_state(), "", ""};
    RecordingTransport transport;
    transport.response.status = 299;
    OAuthClientConfig utf8_config = config();
    utf8_config.client_id = std::string("client-") + "\xC3\xAF";

    const HttpResponse response =
        authorize_with_pkce(utf8_config, browser, receiver, transport, entropy);

    require(response.status == 299, "HTTP 299 token response was not accepted");
    require(browser.urls.front().find("client_id=client-%C3%AF") != std::string::npos,
        "non-ASCII authorization parameter was not byte-percent-encoded");
    require(transport.requests.front().body.find("client_id=client-%C3%AF")
            != std::string::npos,
        "non-ASCII form parameter was not byte-percent-encoded");
}

void test_callback_shapes_and_state() {
    const std::vector<AuthorizationCallback> malformed = {{}, {"code", "", "", ""},
        {"code", deterministic_state(), "error", ""},
        {"code", deterministic_state(), "", "unexpected"}, {"", "", "denied", ""}};
    for (const AuthorizationCallback& callback : malformed) {
        ScriptedEntropy entropy{{zeros(), zeros()}};
        RecordingBrowser browser;
        FixedReceiver receiver;
        receiver.callback = callback;
        RecordingTransport transport;
        expect_oauth_error(
            [&] {
                (void)authorize_with_pkce(config(), browser, receiver, transport, entropy);
            },
            OAuthError::Kind::invalid_callback);
        require(browser.urls.size() == 1 && transport.requests.empty(),
            "malformed callback had incorrect side effects");
    }

    const std::vector<AuthorizationCallback> mismatches = {
        {"code", "wrong", "", ""}, {"", "wrong", "denied", "description"}};
    for (const AuthorizationCallback& callback : mismatches) {
        ScriptedEntropy entropy{{zeros(), zeros()}};
        RecordingBrowser browser;
        FixedReceiver receiver;
        receiver.callback = callback;
        RecordingTransport transport;
        expect_oauth_error(
            [&] {
                (void)authorize_with_pkce(config(), browser, receiver, transport, entropy);
            },
            OAuthError::Kind::state_mismatch);
        require(transport.requests.empty(), "state mismatch sent a token request");
    }

    ScriptedEntropy entropy{{zeros(), zeros()}};
    RecordingBrowser browser;
    FixedReceiver receiver;
    receiver.callback = {"", deterministic_state(), "access_denied", "private detail"};
    RecordingTransport transport;
    const OAuthError rejection = expect_oauth_error(
        [&] { (void)authorize_with_pkce(config(), browser, receiver, transport, entropy); },
        OAuthError::Kind::authorization_rejected);
    require(std::string(rejection.what()).find("private detail") == std::string::npos,
        "authorization error leaked error_description");
    require(transport.requests.empty(), "authorization denial sent a token request");
}

void test_token_rejection_is_single_and_opaque() {
    for (const int status : {0, 199, 300, 400, 500}) {
        ScriptedEntropy entropy{{zeros(), zeros()}};
        RecordingBrowser browser;
        FixedReceiver receiver;
        receiver.callback = {"code", deterministic_state(), "", ""};
        RecordingTransport transport;
        transport.response = {status, {}, "private token failure body"};
        const OAuthError error = expect_oauth_error(
            [&] {
                (void)authorize_with_pkce(config(), browser, receiver, transport, entropy);
            },
            OAuthError::Kind::token_endpoint_rejected);
        require(transport.requests.size() == 1, "token rejection was retried or not sent");
        require(std::string(error.what()).find("private token failure body") == std::string::npos,
            "token rejection leaked response body");
    }
}

void test_entropy_failure_is_cryptographic_and_has_no_network_side_effect() {
    for (const std::size_t failure : {std::size_t{0}, std::size_t{1}}) {
        ScriptedEntropy entropy{{zeros(), zeros()}};
        entropy.fail_at = failure;
        RecordingBrowser browser;
        FixedReceiver receiver;
        RecordingTransport transport;
        expect_oauth_error(
            [&] {
                (void)authorize_with_pkce(config(), browser, receiver, transport, entropy);
            },
            OAuthError::Kind::cryptographic_failure);
        require(browser.urls.empty() && receiver.receives == 0 && transport.requests.empty(),
            "cryptographic failure caused browser or network side effects");
    }
}

} // namespace

int main() {
    try {
        test_rfc7636_vector_and_exact_exchange();
        test_invalid_configurations_do_nothing();
        test_redirect_validation();
        test_valid_loopback_redirects();
        test_non_ascii_encoding_and_upper_success_boundary();
        test_callback_shapes_and_state();
        test_token_rejection_is_single_and_opaque();
        test_entropy_failure_is_cryptographic_and_has_no_network_side_effect();
    } catch (const std::exception& error) {
        std::cerr << "oauth tests failed: " << error.what() << '\n';
        return 1;
    }
    std::cout << "oauth tests passed\n";
    return 0;
}