// created.. 4.26.2024 ~q

#include <Preferences.h>
#include <vector>

const char* TAG = "UserManagement";

//user data structure
typedef struct user {
  char     userName[20];
  uint32_t hashPass;
  byte     userLevel;
};
//.vector of users
std::vector<user> users;
//nvm storage
Preferences prefs;


void setup() {
  Serial.begin(115200);

  Serial.println("User Management");
  Serial.println();
  Serial.println("Creating 2 users..");
  //hash a password..
  uint32_t ph = hash("1234");
  //make a couple of new users..
  user newUser = {"Joe", ph, 99};
  addUser(newUser);
  //gonna re-use, just change the name
  strcpy(newUser.userName, "Mike");
  addUser(newUser);
  //should have 2..
  Serial.print("User count:");
  //users.size() == user count
  Serial.println(users.size());
  // test loading  em back in..
  //generally you do this once during setup..
  Serial.println("Reloading..");
  loadUsers();
  //should have 2 again..
  Serial.print("User count:");
  Serial.println(users.size());
  //check for unique user names..
  Serial.println("Attempting to add Mike again");
  if (!addUser(newUser)) {
    Serial.println("Good, we can't..");
  } else {
    Serial.println("Wrong, should not be able to add..");
  }
  //should have 2..
  Serial.print("User count:");
  //users.size() == user count
  Serial.println(users.size());



  // find Mike??
  int idx = findUser("Mike");
  if ( idx > -1 ) {
    Serial.print("Found usename:");
    Serial.println(users[idx].userName);
    // check password by hashing what they enter..
    ph = hash("4321");// bad one
    if (users[idx].hashPass != ph) {
      Serial.println("Password is not: 4321");
    }
    ph = hash("1234");//good one
    if (users[idx].hashPass == ph) {
      Serial.println("Password is : 1234");
    }

  }

  //check user level functions..
  Serial.print("Mike's user level :");
  byte ul = getUserLevel("Mike");
  Serial.println(ul);
  Serial.println("Changing Mike's level to 1");
  if (setUserLevel("Mike", 1)) {
    Serial.print("Level changed to :");
    ul = getUserLevel("Mike");
    Serial.println(ul);
  }

  //delete a user..
  if (delUser("Mike")) {
    Serial.println("Mike deleted..");
  }
  //should be 1 now..
  Serial.print("User count:");
  Serial.println(users.size());
  //reload everything to make sure..
  Serial.println("Reloading..");
  loadUsers();
  //should now be 1..
  Serial.print("User count:");
  Serial.println(users.size());
  //delete Joe, the last user..
  if (delUser("Joe")) {
    Serial.println("Joe deleted..");
  }
  //should be 0
  Serial.print("User count:");
  Serial.println(users.size());
  //reload to check for still 0
  Serial.println("Reloading..");
  loadUsers();
  //should be 0
  Serial.print("User count:");
  Serial.println(users.size());
  //have fun..

}

void loop() {
  delay(1000);
}


// returns index in vector to user else -1 if not found..
int findUser(const char* userName) {
  int result = -1;
  if (users.size() == 0) return result;
  for ( int i = 0; i < users.size(); i++) {
    if (strcmp(userName, users[i].userName) == 0) {
      result = i;
      break;
    }
  }
  return result;
}

//returns -1 if not found else user level
int getUserLevel(const char* userName) {
  int result = -1;
  if (users.size() == 0) return result;
  for ( int i = 0; i < users.size(); i++) {
    if (strcmp(userName, users[i].userName) == 0) {
      result = users[i].userLevel;
      break;
    }
  }
  return result;
}

// changes user level for a user name, returns true if it saves..
bool setUserLevel(const char* userName, const byte newLevel) {
  bool result = false;
  if (users.size() == 0) return result;
  for ( int i = 0; i < users.size(); i++) {
    if (strcmp(userName, users[i].userName) == 0) {
      users[i].userLevel = newLevel;
      result = saveUsers();
      break;
    }
  }
  return result;
}

// returns true if user was added
bool addUser(user newUser) {
  bool result = false;
  //check for unique user name
  if (findUser(newUser.userName) < 0) {
    users.push_back(newUser);
    //save to prefs..
    result = saveUsers();
  }
  return result;
}

// returns true if user deleted..
bool delUser(const char* userName) {
  bool result = false;
  int pos = findUser(userName);
  if (pos < 0) return result;
  if (users.size() == 1) {
    users.clear();
  } else {
    users.erase(users.begin() + pos);
  }
  //save to prefs
  result = saveUsers();
  return result;
}

// saves all users..
bool saveUsers() {
  bool result = false;
  prefs.begin(TAG);
  if (users.size() < 1) {
    //remove all users..
    if (prefs.getBytesLength("_users_") > 0) {
      result = prefs.remove("_users_");
    } else result = true;//already gone..
  } else {
    //saving some users..
    int totalSize = users.size() * sizeof(user);
    int s = prefs.putBytes("_users_", users.data(), totalSize);
    if (s == totalSize) result = true;
  }
  prefs.end();
  return result;
}

// loads all users..
int loadUsers() {
  int result = 0;
  users.clear();
  prefs.begin(TAG);
  int numUsers = prefs.getBytesLength("_users_");
  if (numUsers > 0) numUsers = numUsers / sizeof(user);
  if (numUsers > 0) {
    user tmpUsers[numUsers];
    int loadedBytes = prefs.getBytes("_users_", tmpUsers, numUsers * sizeof(user));
    if (loadedBytes == (numUsers * sizeof(user))) {
      users.insert(users.begin(), tmpUsers, tmpUsers + numUsers);
      result = users.size();
    }
  }
  prefs.end();
  return result;
}


//djb2 - Hashing function, the hash is stored instead of password..
// password entered is then hashed and resulting hash is saved/compared..
// remember we don't spefically need to know the actual password..
// we just need to authenticate it..
uint32_t hash(char *str) {
  uint32_t hash = 5381;
  int c;
  while (c = *str++)
    hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
  return hash;
}