Email Simulator

#include <iostream>
#include <string>
#include <stdlib.h> //for system("CLS");
#include <windows.h> //for GetAsyncKeyState();

using namespace std;

struct Email //just a basic struct
{
    //below is just data stored in the node
    string sender;
    string recipient;

    string day, month, year;

    string title;
    string content;

    //adapted from https://docs.microsoft.com/en-us/cpp/code-quality/c26495?view=msvc-160 , where it is set via default member initialization;
    int index{}; //every new email will have a different index, used to traverse and pinpoint the correct email.

    Email* prev{}, * next{}; //just previous and next nodes
};

Email* myTemplate() //used to initialise a struct (alternative of constructor)
{
    Email* temp = new Email;

    temp->sender = "\0";
    temp->recipient = "\0";

    temp->day = "\0";
    temp->month = "\0";
    temp->year = "\0";

    temp->title = "\0";
    temp->content = "\0";

    temp->index = 0;
    temp->next = NULL;
    temp->prev = NULL;

    return temp;
};

struct UI //another basic struct, but using constructors
{
    UI* prev, * next; //previous and next nodes
    string text[2]; //stores the selected text and unselected text

    bool selected; //bool to know when to trigger selected text
    int menuFunc; //used to determine which function to call, can also be used to represent Email's index when passing in values

    UI()
    {
        prev = NULL;
        next = NULL;
        text[0] = "\0";
        text[1] = "\0";

        selected = false;

        menuFunc = -1;
    }

    UI(UI* myPrev, UI* myNext, int myMFunc, string myText)
    {
        prev = myPrev;
        next = myNext;
        menuFunc = myMFunc;
        text[0] = myText;
        text[1] = "<<" + text[0] + ">>";

        selected = false;
    }
};

void mainMenu(UI* uiNavi, UI* uiHead)
{
    uiNavi = uiHead; //sets navigator to first element if it isn't already
    cout << endl <<
        "Welcome to the email simulator! Please select your operation from the list below." << endl <<
        "_________________________________________________________________________________" << endl << endl;
    while (uiNavi != NULL)//loop stops when it finally reaches NULL
    {
        cout << uiNavi->text[(int)uiNavi->selected] << endl << endl; //if the current uiNavi->selected is true, then the selected text will be displayed instead
        uiNavi = uiNavi->next;
    }
    cout <<
        "_________________________________________________________________________________" << endl <<
        "[Use ARROW KEYS UP & DOWN to navigate, ENTER/RETURN to select operation]" << endl;
}

int getKeyInt() //just a function to get relevant key codes
{

    if (GetAsyncKeyState(VK_UP))
    {
        return VK_UP;
    }
    else if (GetAsyncKeyState(VK_DOWN))
    {
        return VK_DOWN;
    }
    else if (GetAsyncKeyState(VK_RETURN))
    {
        return VK_RETURN;
    }
    else if (GetAsyncKeyState(VK_ESCAPE))
    {
        return VK_ESCAPE;
    }
    else
    {
        return -1;
    }
}

void displayEmail(int mailIndex, Email* eNavi, Email* eHead, Email* eTail) //used when displaying the individual stored emails
{
    system("CLS");
    eNavi = eHead; //sets email navigator to earliest element in the stack
    while (eNavi->index != mailIndex) //traverse the linked list until it reaches the email with the same index, reference line XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX for explanation
    {
        eNavi = eNavi->next;
    }
    cout <<
        "\nSender's Name: " << eNavi->sender <<
        "\nRecipient's Name: " << eNavi->recipient <<
        "\n\nDate: " << eNavi->day + " . " + eNavi->month + " . " + eNavi->year <<
        "\n\nTitle: " << eNavi->title <<
        "\n\nContent: \n" << eNavi->content << endl;
    system("pause");
    return;
}

void deleteMail(Email*& eNavi, Email*& eHead, Email*& eTail, int mailIndex, bool& modified) //used to remove nodes from the link list, not exactly popping though.
{
    system("CLS");

    string temp = "\0"; //just to get user confirmation

    cout << "\nAre you sure you want to delete this mail? Once deleted the data is gone forever!\nType DELETE to confirm mail deletion (CASE SENSITIVE), type anything else to cancel.\n:";
    cin >> temp;

    if (temp == "DELETE")
    {
        eNavi = eHead; //sets email navigator to earliest element in the node again if it isn't already
        while (eNavi->index != mailIndex) //traversing until the desired email to delete is reached, lets call this node a "node of interest"
        {
            eNavi = eNavi->next;
        }

        if (eNavi != NULL)//just in case for some reason the email was a NULL
        {
            if (eNavi->next != NULL)//if the "node of interest" has an earlier node
            {
                eNavi = eNavi->next;//navigator will switch addresses to earlier node

                if (eNavi->prev->prev != NULL)//if the "node of interest" has a newer node after itself
                {
                    eNavi->prev = eNavi->prev->prev; //navigator will point it's current "prev" to change from "node of interest" to the node after the "node of interest"
                    eNavi->prev->next = eNavi; //and that node will point it's "next" to the navigator's current address
                }
                else//if "node of interest" doesn't have a newer node, ie. it is the latest added node
                {
                    eNavi->prev = NULL;//navigator will point it's current "prev" to change from "node of interest" to NULL
                    eTail = eNavi; //a tail node will be assigned to navigator's address
                }
            }
            else if(eNavi->prev != NULL)//if "node of interest" has a newer node added after itself
            {
                eNavi = eNavi->prev; //navigator will then siwtch addresses to newer node
                eNavi->next = NULL; //navigator will point it's "next" to change from "node of interest" to a NULL
                eHead = eNavi; //a head node will be assigned to navigator's address
            }
            else// if "node of interest" doesn't have an earlier node or a newer node after itself
            {
                eHead = myTemplate(); //head will be reinitialised
                eTail = eHead; //tail will have the same address as head
                eNavi = eHead; //navigator will also have the same address as head
            }
        }

        cout << "Mail was deleted." << endl;
        modified = true; //used in refreshing the displayInbox() function to re-trigger the stuff outside the loop
        system("pause");

        return;
    }
    else
    {
        return;
    }
}

bool mailExecute(int executionCode, bool runFlag, UI* myNavi, UI* myHead, UI* uiTailIB, Email*& eNavi, Email*& eHead, Email*& eTail, int mailIndex, bool& modified) //a hub to determine what function is to be called based on the selected UI node
{
    if (executionCode == 1)
    {
        if (mailIndex != -1 && mailIndex != 0) // -1 and 0 are both default nodes, so they shouldn't trigger
        {
            displayEmail(mailIndex, eNavi, eHead, eTail);
        }
        else
        {
            system("CLS");
            cout << "\nNo mail to read!" << endl;
            system("pause");
        }
        return runFlag; //used to determine if the main loop outside this function with continue running or not
    }
    else if (executionCode == 2)
    {
        deleteMail(eNavi, eHead, eTail, mailIndex, modified);
        runFlag = false;
        return runFlag;
    }
    else if (executionCode == 99)
    {
        runFlag = false;
        return runFlag;
    }
    else
    {
        cout << "\nINVALID CODE" << endl; //usually not triggered, just in case
        return runFlag;
    }
}

bool prompt(string selectedText, int mailIndex, Email*& eNavi, Email*& eHead, Email*& eTail, bool& modified) //a selected mail hub to determine what function is to be called based on the selected UI node, triggered when a mail is selected
{
    bool tempRunFlag = true; // just a temporary run flag to determine if the loop will continue to run
    int tempKeyPress; // to log the current keypress
    UI* myNavi = new UI, * myHead = myNavi, * myTail = myNavi; //creating temporary UI nodes to use with this function
    UI* refreshCache = new UI; // to log the navigator's location upon reprinting the screen

    //initialising the UI nodes
    myNavi->next = new UI(NULL, NULL, 1, "READ EMAIL");
    myNavi = myNavi->next;
    myHead = myNavi;
    myHead->selected = true;
    myNavi->next = new UI(myNavi, NULL, 2, "DELETE EMAIL");
    myNavi = myNavi->next;
    myNavi->next = new UI(myNavi, NULL, 99, "BACK");
    myNavi = myNavi->next;
    myTail = myNavi;
    refreshCache = myHead; //before the loop happens, it points to a head node

    while (tempRunFlag)
    {
        system("CLS");
        cout << "SELECTED MAIL:\n" + selectedText << endl << endl; //shares the same text to indicate selected mail
        myNavi = myHead; //navigator will switch to head's address
        while (myNavi != NULL)//printing out the UI nodes
        {
            cout << myNavi->text[(int)myNavi->selected] << endl;
            myNavi = myNavi->next;
        }
        cout << "\n[Use ARROW KEYS UP & DOWN to navigate, ENTER / RETURN to select operation]" << endl;
        myNavi = refreshCache;//will be used to point navigator to a different node after printing for selection purposes
        system("pause");
        tempKeyPress = getKeyInt();

        //used to navigate the nodes
        switch (tempKeyPress)
        {
        case VK_UP:
            if (myNavi != myHead)
            {
                myNavi->selected = false;
                myNavi = myNavi->prev;
                myNavi->selected = true;
                refreshCache = myNavi; //saves the address to be reassigned to navigator after the reprinting
            }
            else
            {
                break;
            }
            break;
        case VK_DOWN:
            if (myNavi != myTail)
            {
                myNavi->selected = false;
                myNavi = myNavi->next;
                myNavi->selected = true;
                refreshCache = myNavi;
            }
            else
            {
                break;
            }
            break;
        case VK_RETURN:
            tempRunFlag = mailExecute(myNavi->menuFunc, tempRunFlag, myNavi, myHead, myTail, eNavi, eHead, eTail, mailIndex, modified); //to determine whether the loop should continue or break after function is called
            break;
        default:
            break;
        }
    }
    return !modified; //returns an inverse of the "modified" bool, to determine whether the loop should continue or break
}

void displayInbox(UI* myNavi, UI* myHead, UI* myTail, Email*& eNavi, Email*& eHead, Email*& eTail) //displays the inbox of the mail
{
    bool modified = false;
    bool tempRunFlag = true;
    int tempKeyPress;

    UI* refreshCache = myHead; // to log the navigator's location upon reprinting the screen, points to head before the loop begins

    myNavi = myHead; //points the navigator to the newest node in the list

    eNavi = eTail; //email navigator switches address to the newest node in the email linked list

    if (eNavi->sender != "\0") //to check if newest mail has values, just in case
    {
        myNavi->menuFunc = eNavi->index; //assigns the email index to the "menuFunc" to be passed when calling deleteMail() and displayMail()
        myNavi->text[0] = eNavi->sender + "|| " + eNavi->title + " || " + (string)eNavi->day + " . " + (string)eNavi->month + " . " + (string)eNavi->year;  //sets the UI text of navigator
        myNavi->text[1] = "<<" + myNavi->text[0] + ">>";
        myHead = myNavi;//setting myHead to point to navigator's current address
        myHead->selected = true; //this will trigger the selected text's output later
        refreshCache = myHead;// assigns refreshCache to myHead
        myTail = myHead; //if it's only 1 mail in the list, then this will prevent UI from traversing into NULL, if not, below will change the values

        if (eNavi->prev != NULL)//if email navigator has a earlier mail to point to, false if there's only 1 element in the list, which is already done above
        {
            while (eNavi != NULL)//if email navigator is not pointing to the earliest mail, or if theres only 1 element
            {
                if (eNavi != eHead) //double checking if email navigator hasn't reached the earliest mail yet, if it is, then no need to go even earlier
                {
                    eNavi = eNavi->prev; //email navigator approaches eHead by 1 node
                }
                myNavi->next = new UI(myNavi, NULL, eNavi->index, eNavi->sender + "|| " + eNavi->title + " || " + eNavi->day + " . " + eNavi->month + " . " + eNavi->year); //creates a new node to point to
                myNavi = myNavi->next; // navigator switch to the next address that it created
                myTail = myNavi; //assigns tail to newly created UI navigator node
            }
        }
    }
    else //if newest mail has no values, or no mail
    {
        myHead = new UI(NULL, NULL, 0, "nothing to see here");
        myHead->selected = true;
        refreshCache = myHead;
        myTail = myHead;
    }

    while (tempRunFlag)
    {
        system("CLS");
        cout <<
            "\nNow browsing inbox..." << endl <<
            "_____________________________________________________________________________________________________________________" << endl <<
            "SENDER\t\t||\t\t\t\tTITLE\t\t\t\t\t||\tDATE" << endl;
        myNavi = myHead; //UI navigator will be reassigned to point to first UI
        while (myNavi != NULL)
        {
            cout << myNavi->text[(int)myNavi->selected] << endl;
            myNavi = myNavi->next;
        }
        myNavi = refreshCache;//similar implementation in the prompt() function;
        if (myNavi != NULL)
        {
            cout << "\nMenu Function code: " << myNavi->menuFunc << endl;//used for debugging, displays the menuFunc
        }
        cout <<
            "\n\nReached end of inbox" << endl <<
            "_____________________________________________________________________________________________________________________" << endl <<
            "[Use ARROW KEYS UP & DOWN to navigate, ENTER/RETURN to select operation, ESC to return to Main Menu]" << endl;
        system("pause");

        tempKeyPress = getKeyInt();

        switch (tempKeyPress)
        {
        case VK_UP:
            if (myNavi != myHead)
            {
                myNavi->selected = false;
                myNavi = myNavi->prev;
                myNavi->selected = true;
                refreshCache = myNavi;
            }
            break;
        case VK_DOWN:
            if (myNavi != myTail)
            {
                myNavi->selected = false;
                myNavi = myNavi->next;
                myNavi->selected = true;
                refreshCache = myNavi;
            }
            break;
        case VK_RETURN:
            if (eHead->sender != "\0")
            {
                tempRunFlag = prompt(myNavi->text[(int)myNavi->selected], myNavi->menuFunc, eNavi, eHead, eTail, modified); //to determine whether the loop should continue or break after function is called
            }
            break;
        case VK_ESCAPE:
            tempRunFlag = false;
            break;
        default:
            break;
        }
    }
    return;
}


void pushMail(Email * &eHead, Email * &eTail, Email * &draft) //used to actually push the mail into the mail linked list
{
    if (eHead->sender == "\0") //if current head node is empty
    {
        draft->prev = NULL;
        draft->index = eTail->index + 1;
        eHead = draft;
        eTail = eHead;
    }
    else //if head node already has a value
    {
        draft->prev = eTail;
        draft->index = eTail->index + 1;
        eTail->next = draft;
        eTail = draft;
    }
}

void composeEmail(Email*& eHead, Email*& eTail) //prompting the user to get data
{
    Email* draft = new Email;
    system("CLS");
    if (eHead->sender != "\0") ///used to get rid of a \n character in the buffer for no reason, I don't know why it's there, but whats weird is that it only happens once the email linked list already has 1 element inside of it
    {
        cin.ignore();
    }

    do
    {
        cout << "\nPlease type in the sender's name (16 Character Limit)" << endl;
        getline(cin, draft->sender);
    }
    while (draft->sender.length() > 16 || draft->sender.length() <= 0);
    while (draft->sender.length() < 16)
    {
        draft->sender += " ";
    }

    do
    {
        cout << "\nPlease type in the recipient's name (16 Character Limit)" << endl;
        getline(cin, draft->recipient);
    }
    while (draft->recipient.length() > 16 || draft->recipient.length() <= 0);

    //I forgot why I separated day, month and year
    do
    {
        cout << "\nPlease type in the date of the month in numbers (Eg. 02 for 2nd day of the month, 10 for 10th)" << endl;
        cin >> draft->day;
    } while (draft->day.length() != 2);

    do
    {
        cout << "\nPlease type in the month in numbers (Eg. 03 for MARCH, 12 for DECEMBER)" << endl;
        cin >> draft->month;
    } while (draft->month.length() != 2 );

    do
    {
        cout << "\nPlease type in the year (Eg. 2020, 1956, 0126)" << endl;
        cin >> draft->year;
        cin.ignore();
    } while (draft->year.length() != 4);

    do
    {
        cout << "\nPlease type in the email title (72 Character Limit)" << endl;
        getline(cin, draft->title);
    }
    while (draft->title.length() > 68 || draft->title.length() <= 0);
    while (draft->title.length() < 68)
    {
        draft->title += " ";
    }

    cout << "\nPlease type in your email content below: " << endl;
    cout << "(When done, enter a \\ character to complete the email and send it)" << endl;
    getline(cin, draft->content, '\\'); //changed the delimiter to a "\" character so we can type in paragraphs without worry

    cout << "\n\nEmail is sent! Please check inbox." << endl;

    draft->next = NULL;
    pushMail(eHead, eTail, draft);

    system("pause");
}

bool terminateSim(bool runFlag) //used to confirm if user wants to quit the email simulator
{
    system("CLS");
    string temp = "\0";
    cout << "\nAre you sure you want to quit? Any data during this session is NOT stored\n\n Type \"QUIT\" to confirm (CASE SENSITIVE)\n or type anything else to continue session.\n";
    cin >> temp;

    if (temp == "QUIT")
    {
        return !runFlag;
    }
    else
    {
        return runFlag;
    }
}

bool mainMenuExecute(int executionCode, bool runFlag, UI* uiNaviIB, UI* uiHeadIB, UI* uiTailIB, Email*& eNavi, Email*& eHead, Email*& eTail) //a hub similar to prompt()
{
    if (executionCode == 1)
    {
        composeEmail(eHead, eTail);
        return runFlag;
    }
    else if (executionCode == 2)
    {
        displayInbox(uiNaviIB, uiHeadIB, uiTailIB, eNavi, eHead, eTail);
        return runFlag;
    }
    else if (executionCode == 99)
    {
        return terminateSim(runFlag);
    }
    else
    {
        cout << "\nINVALID CODE" << endl;
        return runFlag;
    }
}

int main()
{
    //Main Menu UI
    UI  * composer = new UI(NULL, NULL, 1, "Compose an email to yourself"),
        * inboxer = new UI(composer, NULL, 2, "Look through your inbox"),
        * terminator = new UI(inboxer, NULL, 99, "Terminate email simulator");
    composer->next = inboxer;
    inboxer->next = terminator;
    UI  * uiHeadMM = composer,
        * uiTailMM = terminator,
        * uiNaviMM = uiHeadMM;
    uiNaviMM->selected = true;


    //Inbox UI
    UI  * uiHeadIB = new UI(NULL,NULL,0,"nothing to see here"),
        * uiTailIB = uiHeadIB,
        * uiNaviIB = uiHeadIB;
        uiNaviIB->selected = true;


    //Actual mail stuff
    Email   * mHead = myTemplate(),
            * mTail = mHead;
    Email   * mNavi = mHead;


    bool simulate = true; ///similar to tempRunFlag
    int keypress;

    while (simulate)
    {
        system("CLS");
        mainMenu(uiNaviMM, uiHeadMM);
        system("pause");
        keypress = getKeyInt();

        switch (keypress)
        {
        case VK_UP:
            if (uiNaviMM->prev != NULL)
            {
                uiNaviMM->selected = false;
                uiNaviMM = uiNaviMM->prev;
                uiNaviMM->selected = true;
            }
            else //used to rotate selection
            {
                uiNaviMM->selected = false;
                uiNaviMM = uiTailMM;
                uiNaviMM->selected = true;
            }
            break;
        case VK_DOWN:
            if (uiNaviMM->next != NULL)
            {
                uiNaviMM->selected = false;
                uiNaviMM = uiNaviMM->next;
                uiNaviMM->selected = true;
            }
            else
            {
                uiNaviMM->selected = false;
                uiNaviMM = uiHeadMM;
                uiNaviMM->selected = true;
            }
            break;
        case VK_RETURN:
            simulate = mainMenuExecute(uiNaviMM->menuFunc, simulate, uiNaviIB, uiHeadIB, uiTailIB, mNavi, mHead, mTail);
            break;
        default:
            break;
        }
    }

    system("CLS");
    cout << "\nThank you for using email simulator, the program will now terminate." << endl;
    system("pause");
}