/**
 * Read the authorized_keys file of the initrd, and put its lines in a json
 * array.
 * @return json array of authorized_keys
 */
json_t * readAuthorizedKeysToJson()
{
    json_t * keys = json_object();

    // Open file.
    FILE * authorized_keys = fopen(AUTHORIZED_KEYS_PATH, "r");
    // Check if that succeeded.
    if (authorized_keys == NULL)
    {
        return NULL;
    }

    // Read file line by line.
    int index = 1;
    char * field;
    char * line = NULL;
    size_t line_length = 0;
    ssize_t read;
    while ((read = getline(&line, &line_length, authorized_keys)) != -1)
    {
        // Ignore empty lines, they do have IDs though.
        if (strlen(line) > 1)
        {
            asprintf(&field, "%d", index);
            // Remove trailing newline.
            line[strcspn(line, "\n")] = 0;
            json_object_set(keys, field, json_string(line));
        }
        index++;
    }

    // Close file and clean up.
    fclose(authorized_keys);
    if (line)
    {
        free(line);
    }

    return keys;
}

/**
 * Callback function that lists the current ssh keys authorised for access
 * to the initrd.
 *
 * Example output:
 * {"ssh-keys":{"1":"ssh-rsa AAAAB3... example@example.com",
 * "2":"ssh-rsa AAAAB3...","5":"command=\"/usr/bin/cryptops-client\" ssh-rsa
 *  AAAAB3... cryptops-test@greenhost"}}
 *
 * The indices correspond to line numbers of the authorized_keys file.
 * Missing indices (like 3 and 4 in the example) arise from empty lines in the
 * file; those are creted when keys are deleted.
 *
 * @param[in]   request   incoming HTTP request
 * @param[out]  response  HTTP response to the request
 * @param[in]   user_data extra data to pass between main thread and callbacks
 * @return                internal status code
 */
int callback_ssh_keys_get(const struct _u_request * request,
    struct _u_response * response, void * user_data)
{
    // Read lines of authorized_keys file into json array.
    json_t * keys = readAuthorizedKeysToJson();
    if (keys == NULL)
    {
        y_log_message(Y_LOG_LEVEL_ERROR,
            "Could not open authorized_keys file");
        return send_simple_response(response, 500, "error",
            "error reading authorized_keys");
    }

    // Create json response.
    json_t * json_body = NULL;
    json_body = json_object();
    json_object_set_new(json_body, "ssh-keys", keys);

    // Send response.
    ulfius_set_json_body_response(response, 200, json_body);
    json_decref(json_body);
    return U_CALLBACK_CONTINUE;
}