config_io.h

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// Copyright (C) 2026 Douglas Quigg (dstroy0) <dquigg123@gmail.com>
// SPDX-License-Identifier: AGPL-3.0-or-later
 
/**
 * @file config_io.h
 * @brief Schema-driven config export / restore (DETWS_ENABLE_CONFIG_IO).
 *
 * The app declares a fixed schema - an array of {key, type} fields - and this
 * service serializes their current values from the config store to a portable
 * `key=value` text blob (one field per line) for backup / migration, and parses
 * such a blob back into the store for restore / bulk provisioning. Schema-driven
 * (rather than enumerating NVS) keeps it deterministic and zero-heap; the
 * serialize / parse round-trip is host-tested against the in-memory config store.
 *
 * @author  Douglas Quigg (dstroy0)
 * @date    2026
 */
 
#ifndef DETERMINISTICESPASYNCWEBSERVER_CONFIG_IO_H
#define DETERMINISTICESPASYNCWEBSERVER_CONFIG_IO_H
 
#include "ServerConfig.h"
#include <stddef.h>
#include <stdint.h>
 
#if DETWS_ENABLE_CONFIG_IO
 
/** @brief Type of a config field (selects the typed get/set used). */
enum class DetwsCfgType : uint8_t
{
    DETWS_CFG_STR = 0, ///< null-terminated string.
    DETWS_CFG_U32 = 1, ///< unsigned 32-bit integer (serialized as decimal).
};
 
/** @brief One field in an export/restore schema. */
struct DetwsCfgField
{
    const char *key;   ///< config-store key (<= 15 chars).
    DetwsCfgType type; ///< the field's value type.
};
 
/**
 * @brief Export the schema's current values from namespace @p ns as `key=value`
 *        lines into @p out.
 * @return characters written, or 0 on a too-small buffer / failure (fail-closed).
 */
int detws_config_export(const char *ns, const DetwsCfgField *fields, size_t n, char *out, size_t cap);
 
/**
 * @brief Import `key=value` lines from @p text into namespace @p ns, writing each
 *        line whose key is in the schema with the schema's type. Unknown keys are
 *        skipped.
 * @return number of fields written.
 */
int detws_config_import(const char *ns, const DetwsCfgField *fields, size_t n, const char *text, size_t len);
 
#endif // DETWS_ENABLE_CONFIG_IO
#endif // DETERMINISTICESPASYNCWEBSERVER_CONFIG_IO_H