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

export module Crafter.Network:TLS;
import std;
import :Stream;

#ifndef CRAFTER_NETWORK_BROWSER
namespace Crafter {
    // TLS over a TCP socket, via libssl (OpenSSL 3). This is the transport
    // that turns `ClientHTTP1`/`ListenerHTTP1` into `https://` endpoints; it
    // is deliberately protocol-agnostic, so anything else that owns a
    // connected descriptor can wrap it the same way.
    //
    // No OpenSSL type appears below: the SSL_CTX and SSL live behind the Impl
    // pointers, so importing this partition does not drag <openssl/*.h> into
    // the consumer. TLS 1.2 is the floor, the platform's cipher defaults are
    // used unchanged, and renegotiation is left to OpenSSL's own policy.
    export class TLSException : public std::runtime_error {
    public:
        using std::runtime_error::runtime_error;
    };

    // A certificate and its private key, PEM-encoded.
    export struct TLSCertificatePem {
        std::string certificate;
        std::string privateKey;
    };

    // The certificate the server presents. Exactly one source is used, in
    // this order: certPath/keyPath, then certPem/keyPem, then selfSigned.
    //
    // selfSigned generates an ephemeral in-memory certificate (see
    // GetSelfSignedCertificatePem) — for development, tests and LAN use. A
    // client talking to it needs either insecureNoServerValidation or the
    // certificate itself as a trust anchor.
    export struct TLSServerCredentials {
        // PEM files on disk. certPath may hold a chain (leaf first).
        std::string certPath;
        std::string keyPath;
        // The same material inline, for callers that hold it in memory
        // already (a secret store, a test) and would rather not touch disk.
        std::string certPem;
        std::string keyPem;
        bool selfSigned = false;

        // Mutual TLS. With requireClientCertificate set, a peer that presents
        // no certificate — or one that does not chain to clientCaPath — is
        // rejected during the handshake. clientCaPath is a PEM file or a
        // directory of them; when it is empty the system trust store is used.
        std::string clientCaPath;
        bool requireClientCertificate = false;

        // Protocols we are willing to speak, in server preference order. A
        // client that offers ALPN and none of these is rejected with
        // no_application_protocol (RFC 7301 §3.2) rather than being let
        // through to speak something we cannot parse. A client that offers no
        // ALPN at all is accepted — plenty of tooling still does not send it.
        std::vector<std::string> alpnProtocols = { "http/1.1" };
    };

    // How the client checks the server, and what it presents itself.
    //
    // The default verifies the chain against the system trust store *and* the
    // hostname, which is the only combination that is actually safe; a chain
    // check without a name check accepts any valid certificate for any name.
    export struct TLSClientCredentials {
        // Skip both checks. Development only — it accepts any certificate,
        // including an attacker's.
        bool insecureNoServerValidation = false;

        // Extra trust anchor: a PEM file or a directory of them. Added to the
        // system store rather than replacing it. This is how you talk to a
        // self-signed listener without giving up verification — hand the
        // client the server's certificate.
        std::string caPath;
        // The same, inline.
        std::string caPem;

        // Overrides the name used for SNI and hostname verification. Empty
        // means the host being connected to, which is what you want unless
        // you are dialling an address that differs from the certificate name
        // (a tunnel, a pinned IP).
        std::string serverName;

        // Client certificate for mutual TLS. Ignored when the server does not
        // ask for one.
        std::string certPath;
        std::string keyPath;

        // Protocols to offer, in client preference order. Empty sends no ALPN
        // extension at all.
        std::vector<std::string> alpnProtocols = { "http/1.1" };
    };

    // A configured SSL_CTX. Shared by every connection it produces — one per
    // listener, one per client — because the expensive parts (parsing the
    // certificate, loading the trust store) are per-context, and OpenSSL 3
    // lets an SSL_CTX be used concurrently from many threads.
    //
    // Held by shared_ptr: a TLSStream keeps its context alive, so a listener
    // that goes away mid-connection does not pull the configuration out from
    // under a session still using it.
    export class TLSContext {
    public:
        static std::shared_ptr<TLSContext> Server(const TLSServerCredentials& credentials);
        static std::shared_ptr<TLSContext> Client(const TLSClientCredentials& credentials);

        ~TLSContext();
        TLSContext(const TLSContext&) = delete;
        TLSContext& operator=(const TLSContext&) = delete;

    private:
        TLSContext();
        struct Impl;
        std::unique_ptr<Impl> impl;
        friend class TLSStream;
    };

    // A TLS session over an already-connected descriptor. Non-owning, like
    // PlainStream: the descriptor stays owned by its ClientTCP, and this only
    // adds the record layer on top.
    //
    // Both factories complete the handshake before returning, so a stream you
    // hold is a stream you can write to. They throw TLSException on
    // certificate rejection, on a protocol mismatch, and on a peer that stops
    // answering mid-handshake.
    export class TLSStream final : public ByteStream {
    public:
        // Client side. `hostName` drives SNI and hostname verification unless
        // the credentials overrode it with serverName; an IP literal sets no
        // SNI (RFC 6066 forbids it) and is checked against the certificate's
        // iPAddress SANs instead.
        static std::unique_ptr<TLSStream> Connect(int descriptor,
                                                 std::shared_ptr<TLSContext> context,
                                                 const std::string& hostName,
                                                 std::chrono::milliseconds timeout);

        // Server side, on a descriptor accept(2) just handed us.
        static std::unique_ptr<TLSStream> Accept(int descriptor,
                                                std::shared_ptr<TLSContext> context,
                                                std::chrono::milliseconds timeout);

        ~TLSStream() override;

        StreamStatus ReadSome(char* buffer, std::size_t size,
                              std::chrono::milliseconds timeout,
                              std::size_t& read) override;
        void Write(const void* buffer, std::size_t size,
                   std::chrono::milliseconds timeout) override;
        void Shutdown() noexcept override;
        int Descriptor() const noexcept override;
        std::string_view Protocol() const noexcept override;
        bool Secure() const noexcept override { return true; }

        // The negotiated protocol version, e.g. "TLSv1.3". For logging.
        std::string Version() const;
        // One-line subject of the peer's certificate, empty when it presented
        // none. With requireClientCertificate a non-empty value is the
        // authenticated client identity.
        std::string PeerCertificateSubject() const;

    private:
        TLSStream();
        struct Impl;
        std::unique_ptr<Impl> impl;
    };

    // The process-wide ephemeral self-signed certificate used by
    // TLSServerCredentials{selfSigned=true}, in PEM form. Generated on first
    // call and then cached, so every listener in a process presents the same
    // certificate and a client can be handed it as a trust anchor.
    //
    // ECDSA P-256, CN=localhost, SAN {DNS:localhost, IP:127.0.0.1, IP:::1},
    // valid for 10 days. Development and tests only — it is regenerated on
    // every process start and no peer has any reason to trust it.
    export const TLSCertificatePem& GetSelfSignedCertificatePem();
}
#endif