/*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

#pragma once

#include <stdbool.h>

#include "stuffer/s2n_stuffer.h"
#include "tls/s2n_tls_parameters.h"

#define S2N_EXTENSION_TYPE_FIELD_LENGTH   2
#define S2N_EXTENSION_LENGTH_FIELD_LENGTH 2
#define S2N_EXTENSION_HEADER_LENGTH       (S2N_EXTENSION_TYPE_FIELD_LENGTH + S2N_EXTENSION_LENGTH_FIELD_LENGTH)

/* The number of extensions supported by S2N */
#define S2N_SUPPORTED_EXTENSIONS_COUNT (sizeof(s2n_supported_extensions) / sizeof(s2n_supported_extensions[0]))

/* The number of bytes needed to assign 1 bit to every supported extension.
 * The +1 is necessary to handle any remainder left over when dividing. */
#define S2N_SUPPORTED_EXTENSIONS_BITFIELD_LEN ((S2N_SUPPORTED_EXTENSIONS_COUNT / sizeof(char)) + 1)

struct s2n_connection;
typedef struct {
    uint16_t iana_value;
    unsigned is_response : 1;
    uint16_t minimum_version;

    int (*send)(struct s2n_connection *conn, struct s2n_stuffer *out);
    int (*recv)(struct s2n_connection *conn, struct s2n_stuffer *in);

    /* Returns true or false to indicate whether the extension should be sent */
    bool (*should_send)(struct s2n_connection *conn);

    /* Handler called if an extension is not received */
    int (*if_missing)(struct s2n_connection *conn);
} s2n_extension_type;

static const uint16_t s2n_supported_extensions[] = {
    TLS_EXTENSION_RENEGOTIATION_INFO,
    TLS_EXTENSION_PQ_KEM_PARAMETERS,
    TLS_EXTENSION_SERVER_NAME,
    TLS_EXTENSION_MAX_FRAG_LEN,
    TLS_EXTENSION_STATUS_REQUEST,
    TLS_EXTENSION_SUPPORTED_GROUPS,
    TLS_EXTENSION_EC_POINT_FORMATS,
    TLS_EXTENSION_SIGNATURE_ALGORITHMS,
    TLS_EXTENSION_ALPN,
    TLS_EXTENSION_SCT_LIST,
    TLS_EXTENSION_SESSION_TICKET,
    TLS_EXTENSION_SUPPORTED_VERSIONS,
    TLS_EXTENSION_KEY_SHARE,
    TLS_EXTENSION_COOKIE,
    TLS_QUIC_TRANSPORT_PARAMETERS,
    TLS_EXTENSION_PSK_KEY_EXCHANGE_MODES,
    TLS_EXTENSION_PRE_SHARED_KEY,
    TLS_EXTENSION_EARLY_DATA,
    TLS_EXTENSION_EMS,
    TLS_EXTENSION_NPN,
};

typedef char s2n_extension_bitfield[S2N_SUPPORTED_EXTENSIONS_BITFIELD_LEN];

typedef uint8_t s2n_extension_type_id;
extern const s2n_extension_type_id s2n_unsupported_extension;

int s2n_extension_send(const s2n_extension_type *extension_type, struct s2n_connection *conn, struct s2n_stuffer *out);
int s2n_extension_recv(const s2n_extension_type *extension_type, struct s2n_connection *conn, struct s2n_stuffer *in);
int s2n_extension_is_missing(const s2n_extension_type *extension_type, struct s2n_connection *conn);

/* Map from TLS IANA value to internal s2n id.
 * All possible IANA values is a large space, so using an internal id gives us more
 * flexibility when using arrays / bitfields / etc. */
int s2n_extension_supported_iana_value_to_id(const uint16_t iana_value, s2n_extension_type_id *internal_id);

/* Initializer */
int s2n_extension_type_init();

/* Common implementations for send */
int s2n_extension_send_unimplemented(struct s2n_connection *conn, struct s2n_stuffer *out);
int s2n_extension_send_noop(struct s2n_connection *conn, struct s2n_stuffer *out);

/* Common implementations for recv */
int s2n_extension_recv_unimplemented(struct s2n_connection *conn, struct s2n_stuffer *in);
int s2n_extension_recv_noop(struct s2n_connection *conn, struct s2n_stuffer *out);

/* Common implementations for should_send */
bool s2n_extension_always_send(struct s2n_connection *conn);
bool s2n_extension_never_send(struct s2n_connection *conn);
bool s2n_extension_send_if_tls13_connection(struct s2n_connection *conn);

/* Common implementations for if_missing */
int s2n_extension_error_if_missing(struct s2n_connection *conn);
int s2n_extension_noop_if_missing(struct s2n_connection *conn);