#include <cstddef>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <string>
#include <sys/timeb.h>
#include <time.h>

#include "util.hpp"

#define VALID_CHARACTERS                                                       \
  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

enum Command parse_command(char *line) {
  /* Find a valid command in the first word of the line (case sensitive)
  args:
    line (char*): string of characters from the input file

  returns:
    (command): Returns the found command. Returns else if first word is invalid.
  */
  if (line == NULL) {
    return INVALID;
  }

  char *rest;
  char *tok = strtok_r(line, " ", &rest);

  if (tok == NULL) {
    return INVALID;
  }

  // REGISTER [username] [password]
  if (strcmp(tok, "REGISTER") == 0) {
    char *username = strtok_r(rest, " ", &rest);
    if (!isValidUsername(username))
      return INVALID;

    char *password = strtok_r(rest, " ", &rest);
    if (password == NULL)
      return INVALID;
    if (!isValidPassword(password))
      return INVALID;

    char *misc = strtok_r(rest, " ", &rest);
    if (misc != NULL)
      return INVALID;

    return REGISTER;
  }

  // LOGIN [username] [password]
  if (strcmp(tok, "LOGIN") == 0) {
    char *username = strtok_r(rest, " ", &rest);
    if (!isValidUsername(username))
      return INVALID;

    char *password = strtok_r(rest, " ", &rest);
    if (password == NULL)
      return INVALID;
    if (!isValidPassword(password))
      return INVALID;

    char *misc = strtok_r(rest, " ", &rest);
    if (misc != NULL)
      return INVALID;

    return LOGIN;
  }

  // LOGOUT
  if (strcmp(tok, "LOGOUT") == 0) {
    char *misc = strtok_r(rest, " ", &rest);
    if (misc != NULL)
      return INVALID;

    return LOGOUT;
  }

  // SEND [msg]
  if (strcmp(tok, "SEND") == 0) {
    if (int(strlen(rest) == 0))
      return INVALID;

    return SEND;
  }

  // SEND2 [username] [msg]
  if (strcmp(tok, "SEND2") == 0) {
    char *username = strtok_r(rest, " ", &rest);
    if (!isValidUsername(username))
      return INVALID;

    if (int(strlen(rest) == 0))
      return INVALID;

    return SEND2;
  }

  // SENDA [msg]
  if (strcmp(tok, "SENDA") == 0) {
    if (int(strlen(rest) == 0))
      return INVALID;

    return SENDA;
  }

  // SENDA2 [username] [msg]
  if (strcmp(tok, "SENDA2") == 0) {
    char *username = strtok_r(rest, " ", &rest);
    if (!isValidUsername(username))
      return INVALID;

    if (int(strlen(rest) == 0))
      return INVALID;

    return SENDA2;
  }

  // SENDF [local file]
  if (strcmp(tok, "SENDF") == 0) {
    char *file_name = strtok_r(rest, " ", &rest);
    if (file_name == NULL)
      return INVALID;

    if (int(strlen(rest) != 0))
      return INVALID;

    return SENDF;
  }

  // SENDF2 [username] [local file]
  if (strcmp(tok, "SENDF2") == 0) {
    char *username = strtok_r(rest, " ", &rest);
    if (!isValidUsername(username))
      return INVALID;

    char *file_name = strtok_r(rest, " ", &rest);
    if (file_name == NULL)
      return INVALID;

    if (int(strlen(rest) != 0))
      return INVALID;

    return SENDF2;
  }

  // LIST
  if (strcmp(tok, "LIST") == 0) {
    char *misc = strtok_r(rest, " ", &rest);
    if (misc != NULL)
      return INVALID;

    return LIST;
  }

  // DELAY
  if (strcmp(tok, "DELAY") == 0) {
    char *delay_time = strtok_r(rest, " ", &rest);
    if (delay_time == NULL)
      return INVALID;

    std::string str(delay_time);
    std::size_t found = str.find_first_not_of("0123456789");
    if (found != std::string::npos)
      return INVALID;

    if (int(strlen(rest) != 0))
      return INVALID;

    return DELAY;
  }

  // default
  return INVALID;
}

bool isValidUsername(char *username) {
  /* Helper function to check if a username string is valid
  args:
    username (char*): Username to be tested.

  returns:
    bool: Username is valid ? true, false
  */
  if (username == NULL)
    return false;
  else if ((strlen(username) > MAX_USERNAME_LEN) ||
           (strlen(username) < MIN_USERNAME_LEN))
    return false;
  else {
    std::string str(username);
    std::size_t found = str.find_first_not_of(VALID_CHARACTERS);
    if (found != std::string::npos)
      return false;
  }

  return true;
}

bool isValidPassword(char *password) {
  if (password == NULL)
    return false;
  else if ((strlen(password) > MAX_PASSWORD_LEN) ||
           (strlen(password) < MIN_PASSWORD_LEN))
    return false;
  else {
    std::string str(password);
    std::size_t found = str.find_first_not_of(VALID_CHARACTERS);
    if (found != std::string::npos)
      return false;
  }

  return true;
}

void Error(const char *format, ...) {
  char msg[4096];
  va_list argptr;
  va_start(argptr, format);
  vsprintf(msg, format, argptr);
  va_end(argptr);
  fprintf(stderr, "Error: %s\n", msg);
  exit(-1);
}

void Log(const char *format, ...) {
  char msg[2048];
  va_list argptr;
  va_start(argptr, format);
  vsprintf(msg, format, argptr);
  va_end(argptr);
  fprintf(stderr, "%s\n", msg);
}

// convert buf[0:3] to int
void buf2i(BYTE *buf, int &i) {
  // No way to avoid Segmentation fault. Some bytes may be 0
  i = 0;
  i += buf[3];
  i += ((int)(buf[2])) << 8;
  i += ((int)(buf[1])) << 16;
  i += ((int)(buf[0])) << 24;
}

// convert int to buf[4] where buf[0] contains MSB's and buf[3] contains LSB's
void i2buf(int &i, BYTE *buf) {
  // No way to avoid Segmentation fault. Some bytes may be 0
  buf[0] = (BYTE)((i & 0xFF000000) >> 24);
  buf[1] = (BYTE)((i & 0x00FF0000) >> 16);
  buf[2] = (BYTE)((i & 0x0000FF00) >> 8);
  buf[3] = (BYTE)(i & 0x000000FF);
}

const char *com2str(enum Command command) {
  const char *com2str[] = {"REGISTER", "LOGIN",   "LOGOUT", "SEND",
                           "SEND2",    "SENDA",   "SENDA2", "SENDF",
                           "SENDF2",   "LIST",    "DELAY",  "GETF",
                           "PING",     "CONNECT", "",       "INVALID"};
  return com2str[command];
}

// Computes the difference between times a and b in seconds
// a - b = result
double timeDifference(struct timeb a, struct timeb b) {
  return (a.time + a.millitm / (double)1000.0f) -
         (b.time + b.millitm / (double)1000.0f);
}

int getNumEntries(const char *database) {
  FILE *fp = fopen(database, "r");
  if (!fp) {
    Log("Username check failed to open the file: %s", database);
    return -1;
  }

  int numEntries = 0;

  char line[LINE_SIZE] = {0};
  while (fgets(line, LINE_SIZE, fp) != NULL) {
    char *new_line_pos = strchr(line, '\n');
    if (new_line_pos != NULL)
      *new_line_pos = 0;
    // Including blank lines as entries. Don't use any blank lines.
    numEntries++;
    memset(line, 0, LINE_SIZE);
  }

  fclose(fp);
  return numEntries;
}

bool loginQuery(const char *database, char *username, char *password) {
  FILE *fp = fopen(database, "r");
  if (!fp) {
    Log("Could not open user file: %s", database);
    return false;
  }

  char line[LINE_SIZE] = {0};
  while (fgets(line, LINE_SIZE, fp) != NULL) {
    char *new_line_pos = strchr(line, '\n');
    if (new_line_pos != NULL)
      *new_line_pos = 0;

    char *rest;
    char *usr = strtok_r(line, " ", &rest);
    char *pswd = strtok_r(rest, " ", &rest);

    if (usr == NULL || pswd == NULL) {
      Log("Registry check failed to parse the file: %s", database);
      fclose(fp);
      return false;
    }

    if ((strcmp(username, usr) == 0) && (strcmp(password, pswd) == 0)) {
      fclose(fp);
      return true;
    }

    memset(line, 0, LINE_SIZE);
  }

  fclose(fp);
  return false;
}

// User is in registry: true
// User is not in registry: false
bool usernameQuery(const char *database, char *username) {
  FILE *fp = fopen(database, "r");
  if (!fp) {
    Log("Username check failed to open the file: %s", database);
    return false;
  }

  char line[LINE_SIZE] = {0};
  while (fgets(line, LINE_SIZE, fp) != NULL) {
    char *new_line_pos = strchr(line, '\n');
    if (new_line_pos != NULL)
      *new_line_pos = 0;

    char *rest;
    char *usr = strtok_r(line, " ", &rest);

    if (usr == NULL)
      continue;

    if (strcmp(username, usr) == 0) {
      fclose(fp);
      return true;
    }

    memset(line, 0, LINE_SIZE);
  }

  fclose(fp);
  return false;
}

void recordEntry(const char *database, char *key, char *value) {
  FILE *fp = fopen(database, "a");

  if (!fp) {
    Log("Registry append failed to open the file: %s", database);
    return;
  }

  char line[LINE_SIZE] = {0};
  strcat(line, key);
  strcat(line, " ");
  strcat(line, value);
  strcat(line, "\n");

  fputs(line, fp);
  fclose(fp);
}

int buf2file(BYTE *buf, int nbytes, char *filename) {
  FILE *f = fopen(filename, "w");
  if (!f)
    return -1;

  fwrite(buf, 1, nbytes, f);
  fclose(f);
  return 0;
}

int file2buf(char *filename, BYTE *buf) {
  FILE *f = fopen(filename, "r");
  if (!f) {
    Log("Error: Cannot open %s", filename);
    return -1;
  }

  fseek(f, 0, SEEK_END);  // jump to end of file
  long nbytes = ftell(f); // find current offset on file f
  fseek(f, 0, SEEK_SET);  // jump to beginning of file

  if (nbytes > MAX_REQUEST_SIZE) {
    Log("Error: File %s is too big: %d", filename, nbytes);
    fclose(f);
    return -1;
  }

  int nread = fread(buf, 1, nbytes, f);
  if (nread != nbytes) {
    Log("Error: Byte count mismatch with fread: %d, %d", nbytes, nread);
    fclose(f);
    return -1;
  }

  fclose(f);
  return nbytes;
}