/**
 * @file zh_nrf24_gateway.h
 *
 * nRF24L01+ gateway for ESP-IDF.
 *
 * Receives RF sensor telemetry and posts it as events on the default
 * ESP event loop. Pairing is fully internal: the gateway allocates
 * per-type device IDs, persists the binding table in NVS and sends
 * ACK packets.
 *
 * Events emitted:
 *  - ZH_NRF_GATEWAY_EVENT_SENSOR_DATA       — sensor telemetry
 *  - ZH_NRF_GATEWAY_EVENT_SENSOR_PAIRED     — pairing completed (gateway
 *    assigned a new id and the ACK was delivered)
 *  - ZH_NRF_GATEWAY_EVENT_SENSOR_REGISTERED — data packet arrived from a
 *    {id, type} that was missing from the binding table; it was added
 *    on the fly (covers gateway replacement / NVS wipe without re-pairing)
 *
 * Binding table semantics:
 *  - each binding is a pair {id, type};
 *  - the same id may be reused across different types;
 *  - on pairing, the gateway allocates the smallest free id in 1..254
 *    for the requested type;
 *  - deleting a binding makes its id available to the next pairing
 *    request of the same type.
 */
#pragma once

#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>

#include <stdio.h>
#include <string.h>

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "driver/gpio.h"
#include "esp_log.h"
#include "esp_rom_sys.h"
#include "nvs_flash.h"
#include "nvs.h"

#include "esp_err.h"
#include "esp_event.h"
#include "driver/spi_master.h"
#include "zh_nrf24_config.h"

#ifdef __cplusplus
extern "C"
{
#endif

    extern TaskHandle_t zh_nrf24_gateway;

    typedef struct
    {
        spi_host_device_t spi_host; /*!< SPI host (SPI2_HOST / SPI3_HOST) */
        int pin_sck;                /*!< SCK  GPIO */
        int pin_miso;               /*!< MISO GPIO */
        int pin_mosi;               /*!< MOSI GPIO */
        int pin_csn;                /*!< CSN  GPIO (chip select, active low) */
        int pin_ce;                 /*!< CE   GPIO (chip enable, active high) */
        int pin_irq;                /*!< IRQ  GPIO (open-drain, active low) */
        uint8_t channel;            /*!< RF channel (0..125) */
        uint32_t address;           /*!< 24-bit pipe address, transmitted as LE bytes */
        uint32_t spi_clock_hz;      /*!< SPI clock, 0 → default 4 MHz */
    } zh_nrf24_gateway_init_config_t;

    typedef enum
    {
        ZH_NRF_GATEWAY_EVENT_SENSOR_DATA,
        ZH_NRF_GATEWAY_EVENT_SENSOR_PAIRED,
        ZH_NRF_GATEWAY_EVENT_SENSOR_REGISTERED,
    } zh_nrf24_gateway_event_t;

    ESP_EVENT_DECLARE_BASE(ZH_NRF24_GATEWAY_EVENTS);

    /** A single {id, type} binding. */
    typedef struct
    {
        uint8_t id;   /**< 1..254, 0xFF = unassigned */
        uint8_t type; /**< zh_nrf24_sensor_type_t */
    } zh_nrf_gateway_binding_t;

    /**
     * @brief Initialize the gateway.
     *
     * Configures SPI, the IRQ GPIO with falling-edge interrupt, the nRF24L01+
     * transceiver (DPL enabled, RX mode) and prepares NVS and the default
     * event loop if they are not already initialized.
     *
     * @param[in] config  Gateway configuration (must not be NULL)
     *
     * @return ESP_OK on success, or an ESP-IDF error code
     */
    esp_err_t zh_nrf_gateway_init(const zh_nrf24_gateway_init_config_t *config);

    /**
     * @brief Start the receiver task.
     *
     * The task blocks on the IRQ semaphore (or polls the FIFO as a fallback
     * once per second) and dispatches received packets.
     *
     * @return ESP_OK on success
     */
    esp_err_t zh_nrf_gateway_start(void);

    /* ===================== BINDING TABLE API ===================== */

    /**
     * @brief Copy current bindings into @p buf.
     *
     * Thread-safe. Returns number of entries copied (≤ max_count and ≤
     * current table size).
     */
    size_t zh_nrf_gateway_bindings_get(zh_nrf_gateway_binding_t *buf, size_t max_count);

    /** @brief Current number of bindings in the table. */
    size_t zh_nrf_gateway_bindings_count(void);

    /**
     * @brief Check whether a {id, type} binding exists.
     *
     * @return true if the binding is present in the table
     */
    bool zh_nrf_gateway_binding_exists(uint8_t id, uint8_t type);

    /**
     * @brief Auto-register {id, type} if not present.
     *
     * Validates both fields, then adds the pair to the table and persists
     * to NVS if it is not already there. The id is taken from the packet
     * as-is (unlike pairing, which assigns a new id).
     *
     * @return  1        binding was newly added
     * @return  0        binding already existed
     * @return negative  ESP error (invalid arg, NVS failure, etc.)
     */
    int zh_nrf_gateway_binding_auto_register(uint8_t id, uint8_t type);

    /**
     * @brief Delete a {id, type} binding.
     *
     * Composite key: both @p id AND @p type must match. If only one matches,
     * nothing is deleted and ESP_ERR_NOT_FOUND is returned.
     *
     * @return ESP_OK / ESP_ERR_NOT_FOUND / ESP_ERR_INVALID_ARG / ESP_ERR_INVALID_STATE / NVS error
     */
    esp_err_t zh_nrf_gateway_binding_delete(uint8_t id, uint8_t type);

    /** Delete every binding whose id equals @p id (any type). Returns count, or -err. */
    int zh_nrf_gateway_bindings_delete_by_id(uint8_t id);

    /** Delete every binding whose type equals @p type (any id). Returns count, or -err. */
    int zh_nrf_gateway_bindings_delete_by_type(uint8_t type);

    /** Remove all bindings (persisted). */
    esp_err_t zh_nrf_gateway_binding_clear_all(void);

#ifdef __cplusplus
}
#endif