/* Example of FAT filesystem on external Flash.
   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.

   This sample shows how to store files inside a FAT filesystem.
   FAT filesystem is stored in a partition inside SPI flash, using the 
   flash wear levelling library.
*/

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "esp_flash.h"
#include "esp_flash_spi_init.h"
#include "esp_partition.h"
#include "esp_vfs.h"
#include "esp_vfs_fat.h"
#include "esp_system.h"

static const char *TAG = "example";

// Handle of the wear levelling library instance
static wl_handle_t s_wl_handle = WL_INVALID_HANDLE;

// Mount path for the partition
const char *base_path = "/extflash";

static esp_flash_t* example_init_ext_flash(void);
static const esp_partition_t* example_add_partition(esp_flash_t* ext_flash, const char* partition_label);
static void example_list_data_partitions(void);
static bool example_mount_fatfs(const char* partition_label);
static void example_get_fatfs_usage(size_t* out_total_bytes, size_t* out_free_bytes);

void app_main(void)
{
    // Set up SPI bus and initialize the external SPI Flash chip
    esp_flash_t* flash = example_init_ext_flash();
    if (flash == NULL) {
        return;
    }

    // Add the entire external flash chip as a partition
    const char *partition_label = "storage";
    example_add_partition(flash, partition_label);

    // List the available partitions
    example_list_data_partitions();

    // Initialize FAT FS in the partition
    if (!example_mount_fatfs(partition_label)) {
        return;
    }

    // Print FAT FS size information
    size_t bytes_total, bytes_free;
    example_get_fatfs_usage(&bytes_total, &bytes_free);
    ESP_LOGI(TAG, "FAT FS: %d kB total, %d kB free", bytes_total / 1024, bytes_free / 1024);

    // Create a file in FAT FS
    ESP_LOGI(TAG, "Opening file");
    FILE *f = fopen("/extflash/hello.txt", "wb");
    if (f == NULL) {
        ESP_LOGE(TAG, "Failed to open file for writing");
        return;
    }
    fprintf(f, "Written using ESP-IDF %s\n", esp_get_idf_version());
    fclose(f);
    ESP_LOGI(TAG, "File written");

    // Open file for reading
    ESP_LOGI(TAG, "Reading file");
    f = fopen("/extflash/hello.txt", "rb");
    if (f == NULL) {
        ESP_LOGE(TAG, "Failed to open file for reading");
        return;
    }
    char line[128];
    fgets(line, sizeof(line), f);
    fclose(f);
    // strip newline
    char *pos = strchr(line, '\n');
    if (pos) {
        *pos = '\0';
    }
    ESP_LOGI(TAG, "Read from file: '%s'", line);
}

static esp_flash_t* example_init_ext_flash(void)
{
    const spi_bus_config_t bus_config = {
        .mosi_io_num = VSPI_IOMUX_PIN_NUM_MOSI,
        .miso_io_num = VSPI_IOMUX_PIN_NUM_MISO,
        .sclk_io_num = VSPI_IOMUX_PIN_NUM_CLK,
        .quadwp_io_num = -1,
        .quadhd_io_num = -1,
    };

    const esp_flash_spi_device_config_t device_config = {
        .host_id = VSPI_HOST,
        .cs_id = 0,
        .cs_io_num = VSPI_IOMUX_PIN_NUM_CS,
        .io_mode = SPI_FLASH_DIO,
        .speed = ESP_FLASH_40MHZ
    };

    ESP_LOGI(TAG, "Initializing external SPI Flash");
    ESP_LOGI(TAG, "Pin assignments:");
    ESP_LOGI(TAG, "MOSI: %2d   MISO: %2d   SCLK: %2d   CS: %2d",
        bus_config.mosi_io_num, bus_config.miso_io_num,
        bus_config.sclk_io_num, device_config.cs_io_num
    );

    // Initialize the SPI bus
    ESP_ERROR_CHECK(spi_bus_initialize(VSPI_HOST, &bus_config, 1));

    // Add device to the SPI bus
    esp_flash_t* ext_flash;
    ESP_ERROR_CHECK(spi_bus_add_flash_device(&ext_flash, &device_config));

    // Probe the Flash chip and initialize it
    esp_err_t err = esp_flash_init(ext_flash);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "Failed to initialize external Flash: %s (0x%x)", esp_err_to_name(err), err);
        return NULL;
    }

    // Print out the ID and size
    uint32_t id;
    ESP_ERROR_CHECK(esp_flash_read_id(ext_flash, &id));
    ESP_LOGI(TAG, "Initialized external Flash, size=%d KB, ID=0x%x", ext_flash->size / 1024, id);

    return ext_flash;
}

static const esp_partition_t* example_add_partition(esp_flash_t* ext_flash, const char* partition_label)
{
    ESP_LOGI(TAG, "Adding external Flash as a partition, label=\"%s\", size=%d KB", partition_label, ext_flash->size / 1024);
    const esp_partition_t* fat_partition;
    ESP_ERROR_CHECK(esp_partition_register_external(ext_flash, 0, ext_flash->size, partition_label, ESP_PARTITION_TYPE_DATA, ESP_PARTITION_SUBTYPE_DATA_FAT, &fat_partition));
    return fat_partition;
}

static void example_list_data_partitions(void)
{
    ESP_LOGI(TAG, "Listing data partitions:");
    esp_partition_iterator_t it = esp_partition_find(ESP_PARTITION_TYPE_DATA, ESP_PARTITION_SUBTYPE_ANY, NULL);

    for (; it != NULL; it = esp_partition_next(it)) {
        const esp_partition_t *part = esp_partition_get(it);
        ESP_LOGI(TAG, "- partition '%s', subtype %d, offset 0x%x, size %d kB",
        part->label, part->subtype, part->address, part->size / 1024);
    }

    esp_partition_iterator_release(it);
}

static bool example_mount_fatfs(const char* partition_label)
{
    ESP_LOGI(TAG, "Mounting FAT filesystem");
    const esp_vfs_fat_mount_config_t mount_config = {
            .max_files = 4,
            .format_if_mount_failed = true,
            .allocation_unit_size = CONFIG_WL_SECTOR_SIZE
    };
    esp_err_t err = esp_vfs_fat_spiflash_mount(base_path, partition_label, &mount_config, &s_wl_handle);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "Failed to mount FATFS (%s)", esp_err_to_name(err));
        return false;
    }
    return true;
}

static void example_get_fatfs_usage(size_t* out_total_bytes, size_t* out_free_bytes)
{
    FATFS *fs;
    size_t free_clusters;
    int res = f_getfree("0:", &free_clusters, &fs);
    assert(res == FR_OK);
    size_t total_sectors = (fs->n_fatent - 2) * fs->csize;
    size_t free_sectors = free_clusters * fs->csize;

    // assuming the total size is < 4GiB, should be true for SPI Flash
    if (out_total_bytes != NULL) {
        *out_total_bytes = total_sectors * fs->ssize;
    }
    if (out_free_bytes != NULL) {
        *out_free_bytes = free_sectors * fs->ssize;
    }
}