CONTACTS-PROGRAM

FILENAME="CONTACTS.TXT"


def add_contacts():

    try:
        name=input("Enter Name: ")

        # Keep asking until user enters a valid 10-digit number
        while True:

            phone = input("Enter Phone Number: ")

            if phone.isdigit() and len(phone) == 10:

                break
            else:

                print("Invalid phone number. Please enter exactly 10 digits.")
        
        with open("contacts.txt","a") as file:

            file.write(f"{name},{phone}\n")

        print("Contact added successfully.")

    except Exception as e:

        print(f"an error occureed: {e}")

def view_contacts():

    try:

        with open(FILENAME,"r") as f:

            contacts=f.readlines()

            if not contacts:

                print("no contacts found ")

            else:

                print("\nContacts List:")

                for i, contact in enumerate(contacts, start=1):

                    parts = contact.strip().split(",")

                    if len(parts) == 2:  # only process valid lines

                        name, phone = parts

                        print(f"{i}. {name} -- {phone}")

                    else:

                        print(f"{i}. [Invalid entry: {contact.strip()}]")


    except FileNotFoundError:

        print("no contacts found, please add a contact first ")

    except Exception as e:

        print("error while reading a file ",e)



def update_contact():

    try:

        view_contacts()

        choice=int(input("Enter the contact number to update: "))


        with open (FILENAME,"r") as f:

            contacts=f.readlines()

            if 1<=choice<=len(contacts):

                name,phone=contacts[choice-1].strip().split(",")

                print(f"Current Name: {name}, Current Phone: {phone}")

                new_name=input("Enter new name (leave blank to keep current: ") or name 

                while True:

                    new_phone = input("Enter new phone number (leave blank to keep current): ") or phone

                    if new_phone.isdigit() and len(new_phone) == 10:

                        break

                    elif new_phone == phone:  # user kept old value

                        break

                    else:

                        print("Invalid phone number. Please enter exactly 10 digits.")

                contacts[choice-1]=f"{new_name},{new_phone}\n"


                with open(FILENAME,"w") as f:

                    f.writelines(contacts)


                print("Contact updated successfully.")

            else:
                print("Invalid contact number.")

    except ValueError:

        print("Please enter a valid number.")

    except Exception as e:

        print(f"an error occurred",e)


def delete_contact():

    try:

        view_contacts()

        choice=int(input("Enter the contact number to delete: "))

        with open(FILENAME,"r") as f:

            contacts=f.readlines()


        if 1<=choice<=len(contacts):

            deleted=contacts.pop(choice-1)

            with open(FILENAME,"w") as f:

                f.writelines(contacts) 
                print(f"Contact {deleted.strip()} deleted successfully.")


        else:
                print("Invalid contact number.")

    except ValueError:
        print("Please enter a valid number.")

    except  Exception as e:
        print(f"an error occurred:{e}")

def main():
    while True:
        print("\nContact Management System")
        print("1. Add Contact")
        print("2.View Contacts")
        print("3.Update Contact")
        print("4.Delete Contacts")
        print("5.exit")

        try:
            choice=int(input("Enter your choice (1-5): "))

            if choice==1:

                add_contacts()

            elif choice==2:

                view_contacts()

            elif choice==3:

                update_contact()

            elif choice==4:

                delete_contact()

            elif choice==5:

                print("Exiting the program.")

                break

            else:

                print("invalid choice")

        except ValueError:
            print("Please enter a valid number.")

        except Exception as e:
            print(f"an error occurred: {e}")

if __name__=="__main__":
    main()