#include <stdio.h>
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/spi_slave.h"
#include "esp_log.h"
#include "esp_err.h"
#include "esp_wifi.h"
#include "esp_now.h"
#include "esp_netif.h"
#include "nvs_flash.h"
#include "esp_timer.h"

static const char *TAG = "SPI_SLAVE";

// SPI Slave configuration for ESP32-C3
#define SPI_SLAVE_HOST    SPI2_HOST
#define SPI_SLAVE_MOSI    10
#define SPI_SLAVE_MISO    9
#define SPI_SLAVE_SCLK    20
#define SPI_SLAVE_CS      7
#define SPI_SLAVE_DMA_CHAN SPI_DMA_CH_AUTO

// Buffer size for SPI communication
#define BUFFER_SIZE 256

// ESP-NOW configuration
#define ESPNOW_MAXDELAY 512
#define ESPNOW_QUEUE_SIZE 6

// Max ESP-NOW payload length; keep within safe limit
#define ESPNOW_MAX_PAYLOAD 200

// SPI slave receive buffer
static uint8_t recvbuf[BUFFER_SIZE];
static uint8_t sendbuf[BUFFER_SIZE];

// ESP-NOW broadcast MAC address (broadcast to all devices)
static uint8_t broadcast_mac[ESP_NOW_ETH_ALEN] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};

// SPI slave configuration structure
static spi_slave_transaction_t slave_trans;

// ESP-NOW callback functions
static void espnow_send_cb(const esp_now_send_info_t *send_info, esp_now_send_status_t status)
{
    ESP_LOGI(TAG, "ESP-NOW send status: %s", status == ESP_NOW_SEND_SUCCESS ? "SUCCESS" : "FAIL");
}

static void espnow_recv_cb(const esp_now_recv_info_t *recv_info, const uint8_t *data, int len)
{
    ESP_LOGI(TAG, "ESP-NOW received %d bytes from %02x:%02x:%02x:%02x:%02x:%02x", 
             len, recv_info->src_addr[0], recv_info->src_addr[1], recv_info->src_addr[2],
             recv_info->src_addr[3], recv_info->src_addr[4], recv_info->src_addr[5]);
}

// Initialize ESP-NOW
static esp_err_t espnow_init(void)
{
    // Initialize NVS
    esp_err_t ret = nvs_flash_init();
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
        ESP_ERROR_CHECK(nvs_flash_erase());
        ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK(ret);

    // Initialize network interface
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    // Initialize WiFi
    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK(esp_wifi_init(&cfg));
    ESP_ERROR_CHECK(esp_wifi_set_storage(WIFI_STORAGE_RAM));
    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
    ESP_ERROR_CHECK(esp_wifi_start());

    // Initialize ESP-NOW
    ESP_ERROR_CHECK(esp_now_init());
    ESP_ERROR_CHECK(esp_now_register_send_cb(espnow_send_cb));
    ESP_ERROR_CHECK(esp_now_register_recv_cb(espnow_recv_cb));

    // Add peer (broadcast)
    esp_now_peer_info_t peer;
    memset(&peer, 0, sizeof(esp_now_peer_info_t));
    memcpy(peer.peer_addr, broadcast_mac, ESP_NOW_ETH_ALEN);
    peer.channel = 0;
    peer.ifidx = WIFI_IF_STA;
    peer.encrypt = false;
    ESP_ERROR_CHECK(esp_now_add_peer(&peer));

    ESP_LOGI(TAG, "ESP-NOW initialized successfully");
    return ESP_OK;
}

// Broadcast raw SPI bytes via ESP-NOW
static void broadcast_spi_data(uint8_t *data, uint8_t length)
{
    uint8_t send_len = length > ESPNOW_MAX_PAYLOAD ? ESPNOW_MAX_PAYLOAD : length;

    // Send raw payload directly; receiver can json.loads if payload is JSON
    esp_err_t result = esp_now_send(broadcast_mac, data, send_len);
    if (result != ESP_OK) {
        ESP_LOGE(TAG, "ESP-NOW send failed: %s", esp_err_to_name(result));
    } else {
        ESP_LOGI(TAG, "Broadcasting %d bytes via ESP-NOW", send_len);
    }
}

void app_main(void)
{
    ESP_LOGI(TAG, "Starting SPI Slave with ESP-NOW example");
    
    // Initialize ESP-NOW first
    esp_err_t ret = espnow_init();
    if (ret != ESP_OK) {
        ESP_LOGE(TAG, "ESP-NOW initialization failed: %s", esp_err_to_name(ret));
        return;
    }
    
    // Configure SPI slave bus
    spi_bus_config_t buscfg = {
        .mosi_io_num = SPI_SLAVE_MOSI,
        .miso_io_num = SPI_SLAVE_MISO,
        .sclk_io_num = SPI_SLAVE_SCLK,
        .quadwp_io_num = -1,
        .quadhd_io_num = -1,
        .max_transfer_sz = BUFFER_SIZE,
    };
    
    // Configure SPI slave interface
    spi_slave_interface_config_t slvcfg = {
        .mode = 0,  // SPI mode 0 (CPOL=0, CPHA=0)
        .spics_io_num = SPI_SLAVE_CS,
        .queue_size = 3,
        .flags = 0,
    };
    
    // Initialize SPI slave bus
    ret = spi_slave_initialize(SPI_SLAVE_HOST, &buscfg, &slvcfg, SPI_SLAVE_DMA_CHAN);
    if (ret != ESP_OK) {
        ESP_LOGE(TAG, "Failed to initialize SPI slave: %s", esp_err_to_name(ret));
        return;
    }
    
    ESP_LOGI(TAG, "SPI Slave initialized successfully");
    ESP_LOGI(TAG, "MOSI: GPIO%d, MISO: GPIO%d, SCLK: GPIO%d, CS: GPIO%d", 
             SPI_SLAVE_MOSI, SPI_SLAVE_MISO, SPI_SLAVE_SCLK, SPI_SLAVE_CS);
    
    // Prepare send buffer with some test data
    for (int i = 0; i < BUFFER_SIZE; i++) {
        sendbuf[i] = i;
    }
    
    // Main loop
    while (1) {
        // Clear receive buffer
        memset(recvbuf, 0, BUFFER_SIZE);
        
        // Prepare transaction
        slave_trans.length = BUFFER_SIZE * 8;  // Length in bits
        slave_trans.trans_len = 0;
        slave_trans.tx_buffer = sendbuf;
        slave_trans.rx_buffer = recvbuf;
        
        // Wait for SPI master to initiate transaction
        ret = spi_slave_transmit(SPI_SLAVE_HOST, &slave_trans, portMAX_DELAY);
        if (ret != ESP_OK) {
            ESP_LOGE(TAG, "SPI slave transmit failed: %s", esp_err_to_name(ret));
            continue;
        }
        
        // Print received data
        uint8_t received_bytes = slave_trans.trans_len / 8;
        ESP_LOGI(TAG, "Received %d bytes:", received_bytes);
        for (int i = 0; i < received_bytes && i < 32; i++) {
            printf("0x%02x ", recvbuf[i]);
            if ((i + 1) % 16 == 0) printf("\n");
        }
        if (received_bytes % 16 != 0) printf("\n");
        
        // Broadcast received data via ESP-NOW
        if (received_bytes > 0) {
            broadcast_spi_data(recvbuf, received_bytes);
        }
        
        // Small delay before next transaction
        vTaskDelay(pdMS_TO_TICKS(100));
    }
}