/**
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0.
 */

#include <aws/auth/credentials.h>

#include <aws/common/environment.h>
#include <aws/common/string.h>

/*
 * A structure that wraps the public/private data needed to sign an authenticated AWS request
 */
struct aws_credentials {
    struct aws_allocator *allocator;

    struct aws_atomic_var ref_count;

    struct aws_string *access_key_id;
    struct aws_string *secret_access_key;
    struct aws_string *session_token;

    /*
     * A timepoint, in seconds since epoch, at which the credentials should no longer be used because they
     * will have expired.
     *
     *
     * The primary purpose of this value is to allow providers to communicate to the caching provider any
     * additional constraints on how the sourced credentials should be used (STS).  After refreshing the cached
     * credentials, the caching provider uses the following calculation to determine the next requery time:
     *
     *   next_requery_time = now + cached_expiration_config;
     *   if (cached_creds->expiration_timepoint_seconds < next_requery_time) {
     *       next_requery_time = cached_creds->expiration_timepoint_seconds;
     *
     *  The cached provider may, at its discretion, use a smaller requery time to avoid edge-case scenarios where
     *  credential expiration becomes a race condition.
     *
     * The following leaf providers always set this value to UINT64_MAX (indefinite):
     *    static
     *    environment
     *    imds
     *    profile_config*
     *
     *  * - profile_config may invoke sts which will use a non-max value
     *
     *  The following leaf providers set this value to a sensible timepoint:
     *    sts - value is based on current time + options->duration_seconds
     *
     */
    uint64_t expiration_timepoint_seconds;
};

/*
 * Credentials API implementations
 */
struct aws_credentials *aws_credentials_new(
    struct aws_allocator *allocator,
    struct aws_byte_cursor access_key_id_cursor,
    struct aws_byte_cursor secret_access_key_cursor,
    struct aws_byte_cursor session_token_cursor,
    uint64_t expiration_timepoint_seconds) {

    if (access_key_id_cursor.ptr == NULL || access_key_id_cursor.len == 0) {
        aws_raise_error(AWS_ERROR_INVALID_ARGUMENT);
        return NULL;
    }

    if (secret_access_key_cursor.ptr == NULL || secret_access_key_cursor.len == 0) {
        aws_raise_error(AWS_ERROR_INVALID_ARGUMENT);
        return NULL;
    }

    struct aws_credentials *credentials = aws_mem_acquire(allocator, sizeof(struct aws_credentials));
    if (credentials == NULL) {
        return NULL;
    }

    AWS_ZERO_STRUCT(*credentials);

    credentials->allocator = allocator;
    aws_atomic_init_int(&credentials->ref_count, 1);

    credentials->access_key_id =
        aws_string_new_from_array(allocator, access_key_id_cursor.ptr, access_key_id_cursor.len);
    if (credentials->access_key_id == NULL) {
        goto error;
    }

    credentials->secret_access_key =
        aws_string_new_from_array(allocator, secret_access_key_cursor.ptr, secret_access_key_cursor.len);
    if (credentials->secret_access_key == NULL) {
        goto error;
    }

    if (session_token_cursor.ptr != NULL && session_token_cursor.len > 0) {
        credentials->session_token =
            aws_string_new_from_array(allocator, session_token_cursor.ptr, session_token_cursor.len);
        if (credentials->session_token == NULL) {
            goto error;
        }
    }

    credentials->expiration_timepoint_seconds = expiration_timepoint_seconds;

    return credentials;

error:

    aws_credentials_release(credentials);

    return NULL;
}

static void s_aws_credentials_destroy(struct aws_credentials *credentials) {
    if (credentials == NULL) {
        return;
    }

    if (credentials->access_key_id != NULL) {
        aws_string_destroy(credentials->access_key_id);
    }

    if (credentials->secret_access_key != NULL) {
        aws_string_destroy_secure(credentials->secret_access_key);
    }

    if (credentials->session_token != NULL) {
        aws_string_destroy_secure(credentials->session_token);
    }

    aws_mem_release(credentials->allocator, credentials);
}

void aws_credentials_acquire(const struct aws_credentials *credentials) {
    if (credentials == NULL) {
        return;
    }

    aws_atomic_fetch_add((struct aws_atomic_var *)&credentials->ref_count, 1);
}

void aws_credentials_release(const struct aws_credentials *credentials) {
    if (credentials == NULL) {
        return;
    }

    size_t old_value = aws_atomic_fetch_sub((struct aws_atomic_var *)&credentials->ref_count, 1);
    if (old_value == 1) {
        s_aws_credentials_destroy((struct aws_credentials *)credentials);
    }
}

struct aws_byte_cursor aws_credentials_get_access_key_id(const struct aws_credentials *credentials) {
    return aws_byte_cursor_from_string(credentials->access_key_id);
}

struct aws_byte_cursor aws_credentials_get_secret_access_key(const struct aws_credentials *credentials) {
    return aws_byte_cursor_from_string(credentials->secret_access_key);
}

static struct aws_byte_cursor s_empty_session_token_cursor = {
    .ptr = NULL,
    .len = 0,
};

struct aws_byte_cursor aws_credentials_get_session_token(const struct aws_credentials *credentials) {
    if (credentials->session_token != NULL) {
        return aws_byte_cursor_from_string(credentials->session_token);
    }

    return s_empty_session_token_cursor;
}

uint64_t aws_credentials_get_expiration_timepoint_seconds(const struct aws_credentials *credentials) {
    return credentials->expiration_timepoint_seconds;
}

struct aws_credentials *aws_credentials_new_from_string(
    struct aws_allocator *allocator,
    const struct aws_string *access_key_id,
    const struct aws_string *secret_access_key,
    const struct aws_string *session_token,
    uint64_t expiration_timepoint_seconds) {
    struct aws_byte_cursor access_key_cursor = aws_byte_cursor_from_string(access_key_id);
    struct aws_byte_cursor secret_access_key_cursor = aws_byte_cursor_from_string(secret_access_key);
    struct aws_byte_cursor session_token_cursor;
    AWS_ZERO_STRUCT(session_token_cursor);

    if (session_token) {
        session_token_cursor = aws_byte_cursor_from_string(session_token);
    }

    return aws_credentials_new(
        allocator, access_key_cursor, secret_access_key_cursor, session_token_cursor, expiration_timepoint_seconds);
}

/*
 * global credentials provider APIs
 */

void aws_credentials_provider_destroy(struct aws_credentials_provider *provider) {
    if (provider != NULL) {
        provider->vtable->destroy(provider);
    }
}

void aws_credentials_provider_release(struct aws_credentials_provider *provider) {
    if (provider == NULL) {
        return;
    }

    size_t old_value = aws_atomic_fetch_sub(&provider->ref_count, 1);
    if (old_value == 1) {
        aws_credentials_provider_destroy(provider);
    }
}

void aws_credentials_provider_acquire(struct aws_credentials_provider *provider) {
    aws_atomic_fetch_add(&provider->ref_count, 1);
}

int aws_credentials_provider_get_credentials(
    struct aws_credentials_provider *provider,
    aws_on_get_credentials_callback_fn callback,
    void *user_data) {

    AWS_ASSERT(provider->vtable->get_credentials);

    return provider->vtable->get_credentials(provider, callback, user_data);
}