#include <zephyr/fs/littlefs.h>
#include <zephyr/fs/fs.h>
#include <zephyr/logging/log.h>
#include <zephyr/pm/device.h>

#include "fs_mgmt.h"

LOG_MODULE_REGISTER(fs_mgmt, CONFIG_FS_MGMT_LOG_LEVEL);

#define FS_PARTITION_ID FLASH_AREA_ID(littlefs_storage)
FS_LITTLEFS_DECLARE_DEFAULT_CONFIG(fs_storage_data);

#define QSPI_FLASH_NODE DT_ALIAS(qspi_flash)
static const struct device *flash_dev = DEVICE_DT_GET(QSPI_FLASH_NODE);

static struct fs_mount_t fs_storage_mnt = {
    .type = FS_LITTLEFS,
    .fs_data = &fs_storage_data,
    .storage_dev = (void *)FS_PARTITION_ID,
    .mnt_point = CONFIG_FS_MGMT_MOUNT_POINT,
};

static int open_count = 0;
static struct k_mutex flash_pm_lock;

/**
 * @brief Puts the QSPI flash into deep sleep mode to save power
 *       Decrements the open count and suspends the flash if no more users are active
 * @return 0 on success, negative error code on failure
 */
static int fs_mgmt_pm_flash_suspend(void)
{
#if IS_ENABLED(CONFIG_PM_DEVICE)
    if (!device_is_ready(flash_dev))
    {
        return -ENODEV;
    }

    k_mutex_lock(&flash_pm_lock, K_FOREVER);

    if (open_count > 0)
    {
        open_count--;
        if (open_count == 0)
        {
            int rc = pm_device_action_run(flash_dev, PM_DEVICE_ACTION_SUSPEND);
            if (rc < 0)
            {
                LOG_WRN("Could not suspend flash: %d", rc);
            }
            else
            {
                LOG_DBG("Flash entered deep power-down");
            }
        }
    }

    k_mutex_unlock(&flash_pm_lock);
#endif /* CONFIG_PM_DEVICE */
    return 0;
}

/**
 * @brief Resumes the QSPI flash from deep sleep mode
 *       Increments the open count and resumes the flash if it was previously suspended
 * @return 0 on success, negative error code on failure
 */
static int fs_mgmt_pm_flash_resume(void)
{
#if IS_ENABLED(CONFIG_PM_DEVICE)
    if (!device_is_ready(flash_dev))
        return -ENODEV;

    k_mutex_lock(&flash_pm_lock, K_FOREVER);

    if (open_count == 0)
    {
        int rc = pm_device_action_run(flash_dev, PM_DEVICE_ACTION_RESUME);
        if (rc == 0)
        {
            k_busy_wait(50); // t-exit-dpd
            LOG_DBG("Flash resumed");
        }
    }
    open_count++;

    k_mutex_unlock(&flash_pm_lock);
#endif /* CONFIG_PM_DEVICE */
    return 0;
}

int fs_mgmt_pm_open(struct fs_file_t *file, const char *path, fs_mode_t mode)
{
    LOG_DBG("PM Opening file '%s' with mode 0x%02x", path, mode);
    fs_mgmt_pm_flash_resume();
    int rc = fs_open(file, path, mode);
    if (rc < 0)
    {
        fs_mgmt_pm_flash_suspend();
    }
    return rc;
}

int fs_mgmt_pm_close(struct fs_file_t *file)
{
    LOG_DBG("PM Closing file");
    int rc = fs_close(file);
    fs_mgmt_pm_flash_suspend();
    return rc;
}

int fs_mgmt_pm_opendir(struct fs_dir_t *dirp, const char *path)
{
    LOG_DBG("PM Opening directory '%s'", path);
    fs_mgmt_pm_flash_resume();
    int rc = fs_opendir(dirp, path);
    if (rc < 0)
    {
        fs_mgmt_pm_flash_suspend();
    }
    return rc;
}

int fs_mgmt_pm_closedir(struct fs_dir_t *dirp)
{
    LOG_DBG("PM Closing directory");
    int rc = fs_closedir(dirp);
    fs_mgmt_pm_flash_suspend();
    return rc;
}

int fs_mgmt_pm_unlink(const char *path)
{
    LOG_DBG("PM Unlinking file '%s'", path);
    fs_mgmt_pm_flash_resume();
    int rc = fs_unlink(path);
    fs_mgmt_pm_flash_suspend();
    return rc;
}

int fs_mgmt_pm_statvfs(const char *path, struct fs_statvfs *stat)
{
    LOG_DBG("PM Getting filesystem stats for '%s'", path);
    fs_mgmt_pm_flash_resume();
    int rc = fs_statvfs(path, stat);
    fs_mgmt_pm_flash_suspend();
    return rc;
}

int fs_mgmt_pm_stat(const char *path, struct fs_dirent *entry)
{
    LOG_DBG("PM Getting stat for '%s'", path);
    fs_mgmt_pm_flash_resume();
    int rc = fs_stat(path, entry);
    fs_mgmt_pm_flash_suspend();
    return rc;
}

int fs_mgmt_pm_mkdir(const char *path)
{
    LOG_DBG("PM Creating directory '%s'", path);
    fs_mgmt_pm_flash_resume();
    int rc = fs_mkdir(path);
    fs_mgmt_pm_flash_suspend();
    return rc;
}

int fs_mgmt_pm_rename(const char *old_path, const char *new_path)
{
    LOG_DBG("PM Renaming '%s' to '%s'", old_path, new_path);
    fs_mgmt_pm_flash_resume();
    int rc = fs_rename(old_path, new_path);
    fs_mgmt_pm_flash_suspend();
    return rc;
}

int fs_mgmt_pm_rm_recursive(char *path_buf, size_t max_len)
{
    struct fs_dirent entry;
    struct fs_dir_t dir;
    int rc;

    fs_mgmt_pm_flash_resume();

    /* 1. Stat prüfen: Ist es eine Datei? */
    rc = fs_stat(path_buf, &entry);
    if (rc != 0)
    {
        fs_mgmt_pm_flash_suspend();
        return rc;
    }

    /* Wenn es eine Datei ist, direkt löschen und beenden */
    if (entry.type == FS_DIR_ENTRY_FILE)
    {
        rc = fs_unlink(path_buf);
        fs_mgmt_pm_flash_suspend();
        return rc;
    }

    /* 2. Es ist ein Verzeichnis. Schleife bis es leer ist. */
    size_t orig_len = strlen(path_buf);

    while (1)
    {
        fs_dir_t_init(&dir);
        rc = fs_opendir(&dir, path_buf);
        if (rc != 0)
        {
            break;
        }

        bool found_something = false;

        /* Genau EINEN löschbaren Eintrag suchen */
        while (1)
        {
            rc = fs_readdir(&dir, &entry);
            if (rc != 0 || entry.name[0] == '\0')
            {
                break; /* Ende oder Fehler */
            }
            if (strcmp(entry.name, ".") == 0 || strcmp(entry.name, "..") == 0)
            {
                continue; /* Ignorieren */
            }

            found_something = true;
            break; /* Treffer! Schleife abbrechen. */
        }

        /* WICHTIG: Das Verzeichnis SOFORT schließen, BEVOR wir rekurieren!
         * Damit geben wir das File-Handle (NUM_DIRS) an Zephyr zurück. */
        fs_closedir(&dir);

        if (!found_something || rc != 0)
        {
            break; /* Verzeichnis ist nun restlos leer */
        }

        size_t name_len = strlen(entry.name);
        if (orig_len + 1 + name_len >= max_len)
        {
            rc = -ENAMETOOLONG;
            break;
        }

        /* Pfad für das gefundene Kindelement bauen */
        path_buf[orig_len] = '/';
        strcpy(&path_buf[orig_len + 1], entry.name);

        /* Rekursiver Aufruf für das Kind */
        rc = fs_mgmt_pm_rm_recursive(path_buf, max_len);

        /* Puffer sofort wieder auf unser Verzeichnis zurückschneiden */
        path_buf[orig_len] = '\0';

        if (rc != 0)
        {
            break; /* Abbruch, falls beim Löschen des Kindes ein Fehler auftrat */
        }
    }

    /* 3. Das nun restlos leere Verzeichnis selbst löschen */
    if (rc == 0)
    {
        rc = fs_unlink(path_buf);
    }

    fs_mgmt_pm_flash_suspend();
    return rc;
}

int fs_mgmt_pm_mkdir_recursive(char *path)
{
    int rc = 0;
    struct fs_dirent entry;
    char *p = path;

    /* Führenden Slash überspringen, falls vorhanden (z. B. bei "/lfs") */
    if (*p == '/')
    {
        p++;
    }

    /* Flash für den gesamten Durchlauf aktivieren */
    fs_mgmt_pm_flash_resume();

    while (*p != '\0')
    {
        if (*p == '/')
        {
            *p = '\0'; /* String temporär am aktuellen Slash terminieren */

            /* Prüfen, ob dieser Pfadabschnitt bereits existiert */
            rc = fs_stat(path, &entry);

            if (rc == -ENOENT)
            {
                /* Existiert nicht -> anlegen */
                rc = fs_mkdir(path);
                if (rc != 0)
                {
                    *p = '/'; /* Bei Fehler Slash wiederherstellen und abbrechen */
                    break;
                }
            }
            else if (rc == 0)
            {
                /* Existiert -> prüfen, ob es ein Verzeichnis ist */
                if (entry.type != FS_DIR_ENTRY_DIR)
                {
                    rc = -ENOTDIR;
                    *p = '/';
                    break;
                }
            }
            else
            {
                /* Anderer Dateisystemfehler */
                *p = '/';
                break;
            }

            *p = '/'; /* Slash für den nächsten Schleifendurchlauf wiederherstellen */
        }
        p++;
    }

    /* Letztes Element verarbeiten, falls der Pfad nicht mit '/' endet */
    if (rc == 0 && p > path && *(p - 1) != '/')
    {
        rc = fs_stat(path, &entry);
        if (rc == -ENOENT)
        {
            rc = fs_mkdir(path);
        }
        else if (rc == 0)
        {
            if (entry.type != FS_DIR_ENTRY_DIR)
            {
                rc = -ENOTDIR;
            }
        }
    }

    /* Flash am Ende wieder in den Suspend schicken */
    fs_mgmt_pm_flash_suspend();
    return rc;
}

int fs_mgmt_init(void)
{
    k_mutex_init(&flash_pm_lock);
    
    if (!device_is_ready(flash_dev)) {
        LOG_ERR("Flash device not ready!");
        return -ENODEV;
    }

    fs_mgmt_pm_flash_resume();
    
    int rc = fs_mount(&fs_storage_mnt);

    if (rc < 0)
    {
        LOG_ERR("Error mounting filesystem: %d", rc);
        return rc;
    }
    fs_mgmt_pm_flash_suspend();
    LOG_DBG("Filesystem mounted successfully");
    return 0;
}