/**
 * @file tftp.c
 * @brief tftp server
 * @author Speetjens S.
 */

#include "tftp.h"

static const char* TAG = "tftp_server";

extern struct llfs_data_file* llfs_root;

static tftp_custom_file_t virt_file[] =
    {
        {.name = "index.txt",.data = NULL, .len = 0, .ofset = 0},
        {.name = "virtImage.raw",.data = NULL, .len = 0, .ofset = 0}
    };

int str_cat_str(char* dest, size_t dest_size, const char* src) {
    int dest_len = strlen(dest);
    int src_len = strlen(src);
    if (dest_len + src_len > dest_size) {
        return -1;
    }
    memcpy(dest + dest_len, src, src_len);
    return 0;
}

int str_cat(char* dest, size_t dest_size, char c)
{
    int dest_len = strlen(dest);
    if (dest_len + 1 > dest_size) {
        return -1;
    }
    dest[dest_len] = c;
    dest[dest_len + 1] = '\0';
    return 0;
}

/**
 * @brief tftp custom file functions to set the offset and read the data
 * @param[in,out] handle Custom file handles
 * @param[in] offset The offset to set
 * @param[in] whence The origin of the offset
 */
void tftp_custom_fseek(tftp_custom_file_t* handle, size_t offset, int whence) {
    switch (whence) {
        case SEEK_SET:
            handle->ofset = offset;
            break;
        case SEEK_CUR:
            handle->ofset += offset;
            break;
        case SEEK_END:
            break;
    }
    if (handle->ofset > handle->len) {
        handle->ofset = handle->len;
    }
}

/**
 * @brief tftp custom file functions to read the data
 *        auto rolling over the offset
 *        if the bytes to read is bigger than the remaining bytes
 *        it will read the remaining bytes and set the bytes to 0
 * @param[out] buf The buffer to write the data to
 * @param[in] bytes The number of bytes to read
 * @param[in,out] handle Custom file handles
 */
size_t tftp_custom_fread(void* buf, size_t bytes, tftp_custom_file_t* handle) {
    if (handle->ofset + bytes > handle->len) {
        bytes = handle->len - handle->ofset;
    }
    memcpy(buf, handle->data + handle->ofset, bytes);
    handle->ofset += bytes;
    ((char*)buf)[bytes] = '\0';
    if (handle->ofset > handle->len) {
        bytes = 0;
    }
    return bytes;
}

/**
 * @brief tftp helper functions
 */

/**
 * @brief This function is called when a file is opened
 *        It should return a handle to the file or NULL if the file does not exist
 *        The handle contains a ptr to or the actual file data or a virtual file
 * 
 * @param fname The name of the file to open
 * @param mode 	Mode string from TFTP RFC
 * @param write Flag indicating read (0) or write (!= 0) access
 * @return void* File handle supplied to other functions 
 */
void* tftp_open(const char* fname, const char* mode, u8_t write) {
    LOG_INFO(TAG, "Opening %s", fname);

    if (strcmp(fname, virt_file[0].name) == 0 && write == TFTP_READ) {
        return &virt_file[0];
    } else if (strcmp(fname, virt_file[1].name) == 0 && write != TFTP_READ) {
        return &virt_file[1];
    }

    // TODO: waiting on Lorentz to finish creating f* functions for LLFS
    return fopen(fname, write ? "wb" : "rb");
}

/**
 * @brief This function is called when a file is closed
 * 
 * @param handle The handle to the file to close
 */
void tftp_close(void* handle) {
    LOG_INFO(TAG, "closing file");
    if (handle == NULL) {
        LOG_CRIT(TAG, "handle is null");
        return;
    }
    if (handle == &virt_file[0] || handle == &virt_file[1]) {
        return;
    }

    // TODO: waiting on Lorentz to finish creating f* functions for LLFS
    fclose((FILE*)handle);
}

/**
 * @brief This function is called when a file is read
 *        The virtual files are filtered out first
 *        then the file is trying to get read from the llfs
 * 
 * @param handle File handle returned by open()
 * @param buf Target buffer to copy read data to 
 * @param bytes Number of bytes to copy to buf 
 * @return int >= 0: Success; < 0: Error 
 */
int tftp_read(void* handle, void* buf, int bytes) {
    int ret = 0;
    LOG_INFO(TAG, "reading file");
    if (handle == NULL) {
        LOG_CRIT(TAG, "handle is null");
        return -1;
    }
    FILE* file = (FILE*)handle;

    if (file == &virt_file[0]) {
        ret = tftp_custom_fread(buf, bytes, file);
        return ret;
    } else if (file == &virt_file[1]) {
        LOG_CRIT(TAG, "Exception: Trying to read a write only file");
        return -1;
    }
    // TODO: waiting on Lorentz to finish creating f* functions for LLFS
    ret = fread(buf, sizeof(uint8_t), bytes, file);
    if (ret <= 0) {
        return -1;
    }
    return ret;
}

/**
 * @brief This function is called when a file is written
 * 
 * @param handle File handle returned by open()
 * @param p PBUF adjusted such that payload pointer points to the beginning of write data.
 * In other words, TFTP headers are stripped off. 
 * @return int >= 0: Success; < 0: Error 
 */
int tftp_write(void* handle, struct pbuf* p) {
    LOG_INFO(TAG, "Writing file");
    LOG_DEBUG(TAG, "Not implemented yet");
}

/**
 * @brief This function creates the file list for index.txt
 */
void init_index(void)
{
    int len = 0;
    // Add len of the virt files to the size
    for (int i = 0; i < 2; i++)
    {
        len += strlen(virt_file[i].name) + 1;
    }
    const struct llfs_data_file* root = llfs_root;
    while(root != NULL) {
        len += strlen(root->name) + 1;
        root = root->next;
    }
    len++; // +1 for the \0
    virt_file[0].data = malloc(len);
    virt_file[0].len = len;

    for (int i = 0; i < 2; i++)
    {
        str_cat_str(virt_file[0].data, len, virt_file[i].name);
        str_cat(virt_file[0].data, len, '\n');
    }
    root = llfs_root;
    while(root != NULL) {
        str_cat_str(virt_file[0].data, len, root->name);
        str_cat(virt_file[0].data, len, '\n');
        root = root->next;
    }
}

struct tftp_context tftpContext_s = {
    .open = tftp_open,
    .close = tftp_close,
    .read = tftp_read,
    .write = tftp_write
    };

/**
 * @brief Initialize tftp server
 */
void tftp_server_init(void) {
    LOG_INFO(TAG, "Initializing tftp server");
    // init the index.txt virt_file
    init_index();

    // Init the tftp server
    if (tftp_init(&tftpContext_s) != ERR_OK) {
        LOG_FATAL(TAG, "Could not initialize tftp server");
        return;
    }
    LOG_INFO(TAG, "tftp server initialized successfully");
}

void tftp_server_deinit(void) {
    LOG_INFO(TAG, "Deinitializing tftp server");
    tftp_cleanup();
    LOG_INFO(TAG, "tftp server deinitialized successfully");
    free(virt_file[0].data);
    virt_file[0].data = NULL;
    virt_file[0].len = 0;
    virt_file[0].ofset = 0;
}