#include <string.h>
#include <dirent.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/unistd.h>
#include <sys/stat.h>

#include "sd/sd.h"

#include "esp_err.h"
#include "esp_log.h"
#include "esp_vfs_fat.h"
#include "sdmmc_cmd.h"
#include "driver/gpio.h"
#include "driver/sdspi_host.h"
#include "driver/spi_common.h"

#define MAX_CHAR_SIZE 64
#define MOUNT_POINT "/sdcard"

#define SD_PIN_MOSI    (GPIO_NUM_11)
#define SD_PIN_MISO    (GPIO_NUM_13)
#define SD_PIN_CLK     (GPIO_NUM_12)
#define SD_PIN_CS      (GPIO_NUM_10)

static sdmmc_card_t* card = NULL;
static const char *TAG = "sd";

static char** _file_list = NULL;
static size_t _current_file = 0;
static size_t _file_count = 0;

static esp_err_t get_top_level_files(void);

void sd_init(void){
    if(card != NULL){
        ESP_LOGW(TAG, "SD card already initialized");
        return;
    }

    sdmmc_host_t host = SDSPI_HOST_DEFAULT();
    host.unaligned_multi_block_rw_max_chunk_size = 8;

    spi_bus_config_t bus_config = {
        .mosi_io_num = SD_PIN_MOSI,
        .miso_io_num = SD_PIN_MISO,
        .sclk_io_num = SD_PIN_CLK,
        .quadwp_io_num = GPIO_NUM_NC,
        .quadhd_io_num = GPIO_NUM_NC,
        .max_transfer_sz = 4000,
    };

    esp_err_t ret = spi_bus_initialize(host.slot, &bus_config, SDSPI_DEFAULT_DMA);
    if(ret != ESP_OK){
        ESP_LOGE(TAG, "Failed to initialize SD SPI bus (%s)", esp_err_to_name(ret));
        return;
    }

    sdspi_device_config_t slot_config = SDSPI_DEVICE_CONFIG_DEFAULT();
    slot_config.gpio_cs = SD_PIN_CS;
    slot_config.host_id = host.slot;

    esp_vfs_fat_sdmmc_mount_config_t mount_config = {
        .format_if_mount_failed = false,
        .max_files = MAX_SIMULTANEOUS_OPEN_FILES,
        .allocation_unit_size = 16 * 1024
    };

    const char mount_point[] = MOUNT_POINT;

    ret = esp_vfs_fat_sdspi_mount(mount_point, &host, &slot_config, &mount_config, &card);
    
    if(ret != ESP_OK){
        if(ret == ESP_FAIL) ESP_LOGE(TAG, "Failed to mount filesystem."); else ESP_LOGE(TAG, "Failed to initialize the card (%s). ", esp_err_to_name(ret));
        spi_bus_free(host.slot);
        return;
    }

    ESP_LOGI(TAG, "SD card initialized");

    if(get_top_level_files() == ESP_OK) ESP_LOGI(TAG, "Found %d files in root directory", _file_count); else ESP_LOGW(TAG, "No files found in root directory");
}

void print_sd_card_info(void){
    if(card == NULL) return;
    sdmmc_card_print_info(stdout, card);
}

static inline void make_file_path(char* buffer, size_t buffer_size, const char* filename){
    snprintf(buffer, buffer_size, "%s/%s", MOUNT_POINT, filename);
}   

FILE* sd_open_read(const char* filename){
    if(filename == NULL) return NULL;
    char full_path[strlen(MOUNT_POINT) + strlen(filename) + 2];
    make_file_path(full_path, sizeof(full_path), filename);
    return fopen(full_path, "r");
}

FILE* sd_open_write(const char* filename){
    if(filename == NULL) return NULL;
    char full_path[strlen(MOUNT_POINT) + strlen(filename) + 2];
    make_file_path(full_path, sizeof(full_path), filename);
    return fopen(full_path, "w");
}

void sd_close_file(FILE* file){
    if(file != NULL) fclose(file);
}

static esp_err_t get_top_level_files(void){
    char** file_list = NULL;
    size_t count = 0;
    size_t capacity = 0;

    DIR* dir = opendir(MOUNT_POINT);
    if(dir == NULL){
        ESP_LOGE(TAG, "Failed to open directory: %s", MOUNT_POINT);
        return ESP_FAIL;
    }

    struct dirent* entry;
    while((entry = readdir(dir)) != NULL){
        if(entry->d_type == DT_REG){
            ESP_LOGI(TAG, "Found file: %s", entry->d_name);
            
            size_t name_length = strlen(entry->d_name);
            if(name_length >= MAX_CHAR_SIZE){
                ESP_LOGW(TAG, "File name too long: %s", entry->d_name);
                continue;
            }

            if(count == capacity){
                size_t new_capacity = capacity == 0 ? 8 : capacity * 2;
                char** new_file_list = (char**)realloc(file_list, sizeof(char*) * new_capacity);
                if(new_file_list == NULL){
                    ESP_LOGE(TAG, "Failed to allocate memory for file list");
                    for(size_t j = 0; j < count; j++) free(file_list[j]);
                    free(file_list);
                    closedir(dir);
                    return ESP_FAIL;
                }
                file_list = new_file_list;
                capacity = new_capacity;
            }

            file_list[count] = (char*)malloc(sizeof(char) * (name_length + 1));
            if(file_list[count] == NULL){
                ESP_LOGE(TAG, "Failed to allocate memory for file name");
                for(size_t j = 0; j < count; j++) free(file_list[j]);
                free(file_list);
                closedir(dir);
                return ESP_FAIL;
            }

            memcpy(file_list[count], entry->d_name, name_length + 1);
            count++;
        }
    }
    closedir(dir);
    
    if(count == 0){
        ESP_LOGW(TAG, "No files found in directory: %s", MOUNT_POINT);
        free(file_list);
        _file_list = NULL;
        _current_file = 0;
        return ESP_FAIL;
    }

    _file_list = file_list;
    _file_count = count;

    return ESP_OK;
}

size_t sd_get_file_count(void){
    return _file_count;
}

const char* sd_get_next_file(void){
    if(_current_file >= _file_count) _current_file = 0;
    return _file_list[_current_file++];
}

const char* sd_get_previous_file(void){
    if(_current_file == 0) _current_file = _file_count;
    return _file_list[--_current_file];
}

void sd_destroy(void){
    if(card != NULL){
        esp_vfs_fat_sdcard_unmount(MOUNT_POINT, card);
        card = NULL;
        ESP_LOGI(TAG, "SD card unmounted");
    }

    if(_file_list != NULL){
        for(int i = 0; i < _file_count; i++) free((void*)_file_list[i]);
        free((void*)_file_list);
        _file_list = NULL;
    }

    _file_count = 0;
    _current_file = 0;
}