/*************************************************************************

    The 2nd semester Software Technology project reimplemented in C.
                Coded by Janith Leanage.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

 ************************************************************************/


#include<stdio.h>
#include<string.h>

typedef struct _node {
    int no;
    char bname[20];
    char manuf[20];
    float price;
    int qty;

    struct _node *right;
    struct _node *left;
} node;

node *newnode(int n, char bn[], char ma[], float pr, int q)
{
    node *temp;
    temp = (node *) malloc(sizeof(node));
    temp->no = n;
    temp->price = pr;
    temp->qty = q;
    strcpy(temp->bname, bn);
    strcpy(temp->manuf, ma);

    temp->right = NULL;
    temp->left = NULL;

    return temp;
}

node *root;

node *insertRec(node *cur, int n, char bn[], char ma[], float pr, int q)
{
    if (cur == NULL)
    {
        node *temp = newnode(n, bn, ma, pr, q);
        return temp;
    }
    else if (cur->no < n)
        cur->right = insertRec(cur->right, n, bn, ma, pr, q);
    else if (cur->no > n)
        cur->left = insertRec(cur->left, n, bn, ma, pr, q);

    return cur;
}

node *find(int key)
{
    node *cur = root;
    while(cur != NULL)
    {
        if(cur->no == key)
            return cur;
        else if(cur->no < key)
            cur = cur->right;
        else if(cur->no > key)
            cur = cur->left;
    }

    return NULL;
}

void insert()
{
    int n, q;
    char bn[20];
    char ma[20];
    float pr;
    int ans;
    while(1)
    {
        printf("\nAdd a new item\n\n");
        printf("Item ID      : ");
        scanf("%d", &n);
        printf("Brand name   : ");
        scanf("%s", &bn);
        printf("Manufacturer : ");
        scanf("%s", &ma);
        printf("Quantity     : ");
        scanf("%d", &q);
        printf("Unit price   : ");
        scanf("%f", &pr);

        root = insertRec(root, n, bn, ma, pr, q);

        printf("Do you want to add more items? Press 1 for yes, any other number for no: ");
        scanf("%d", &ans);
        if (ans == 1)
            continue;
        else
            break;
    }
}

void display()
{
    int key;
    printf("Enter item no to display: ");
    scanf("%d", &key);

    node *found = find(key);

    if(found == NULL)
        printf("Item not found\n");
    else
        printf("%d\t%s\t%s\t%f\t%d\n", found->no, found->bname, found->manuf, found->price, found->qty);
}

void postordel(node *cur)
{
    if(cur != NULL)
    {
        postordel(cur->left);
        postordel(cur->right);
        free(cur);
    }
}

void modify()
{
    int n, q;
    char bn[20];
    char ma[20];
    float pr;

    printf("\nModify an item\n\n");
    printf("Item ID      : ");
    scanf("%d", &n);

    node *found = find(n);

    if(found == NULL)
        printf("Item not found\n");
    else
    {
        printf("%d\t%s\t%s\t%f\t%d\n", found->no, found->bname, found->manuf, found->price, found->qty);

        printf("New brand name   : ");
        scanf("%s", &bn);
        printf("New manufacturer : ");
        scanf("%s", &ma);
        printf("New quantity     : ");
        scanf("%d", &q);
        printf("New unit price   : ");
        scanf("%f", &pr);

        found->price = pr;
        found->qty = q;
        strcpy(found->bname, bn);
        strcpy(found->manuf, ma);
    }
}

void stockar()
{
    int i, q, add;

    printf("\nEnter item ID: ");
    scanf("%d", &i);

    node *f = find(i);

    if(f == NULL)
        printf("Invalid Item ID.\n");
    else
    {
        printf("Enter 1 to add and 2 to remove items. ");
        scanf("%d", &add);

        switch(add)
        {
            case 1: printf("Quantity to add: ");
                scanf("%d", &q);
                f->qty += q;
                printf("\nQuantity added to stock. New level of stock is %d\n", f->qty);
                break;
            case 2: printf("Quantity to remove: ");
                scanf("%d", &q);
                f->qty -= q;
                printf("\nQuantity removed from stock. New level of stock is %d\n", f->qty);
                break;
            default: printf("Invalid selection\n");
                 break;
        }
    }
}

node *promote(node *cur)
{
    if(cur->left == NULL)
        return cur;
    else
    {
        node *suc = promote(cur->left);

        if(suc == cur->left)
            cur->left == suc->right;

        return suc;
    }
}

node *deleteRec(int key, node *cur)
{
    if(cur == NULL)
    {
        printf("Invalid Item ID\n");
        return NULL;
    }
    else if(key < cur->no)
    {
        cur->left = deleteRec(key, cur->left);
        return cur;
    }
    else if(key > cur->no)
    {
        cur->right = deleteRec(key, cur->right);
        return cur;
    }
    else if(key == cur->no)
    {
        if(cur->left == NULL && cur->right == NULL)
        {
            free(cur);
            printf("Item %d deleted.\n", key);
            return NULL;
        }
        else if(cur->left == NULL && cur->right != NULL)
        {
            node *temp = cur->right;
            free(cur);
            printf("Item %d deleted.\n", key);
            return temp;
        }
        else if(cur->left != NULL && cur->right == NULL)
        {
            node *temp = cur->left;
            free(cur);
            printf("Item %d deleted.\n", key);
            return temp;
        }
        else
        {
            node *suc = promote(cur->right);
            suc->left = cur->left;
            if(suc != cur->right)
                suc->right = cur->right;

            free(cur);
            printf("Item %d deleted.\n", key);
            return suc;
        }
    }
}
void delete()
{
    int i;
    printf("\nEnter Item ID: ");
    scanf("%d", &i);

    root = deleteRec(i, root);
}

void stockbalance(node *cur)
{
    if(cur != NULL)
    {
        stockbalance(cur->left);
        printf("%d\t%s\t%s\t%7.2f\t\t%d\n", cur->no, cur->bname, cur->manuf, cur->price, cur->qty);
        stockbalance(cur->right);
    }
}



void mainmenu()
{
    printf("Welcome to Good Health pharmacy\n Inventory control system\n");
    while(1)
    {
        printf("\nMain menu:\n");
        printf("1) Add a new item\n");
        printf("2) Add stock to an existing item / Remove stock from an existing item\n");
        printf("3) Modify an item\n");
        printf("4) Delete an item\n");
        printf("5) Print stock balance report\n");
        printf("0) Exit\n");

        int dec = -1;
        while (1)
        {
            printf("Enter an item number: ");
            scanf("%d", &dec);

            if (dec < 0 || dec > 5)
            {
                printf("Invalid input\n");
                continue;
            }
            else
                break;
        }

        switch(dec)
        {
            case 0: return;
            case 1: insert(); break;
            case 2: stockar(); break;
            case 3: modify(); break;
            case 4: delete(); break;
            case 5: printf("\nStock balance report\n"); stockbalance(root); break;
        }
    }
}


int main()
{
    mainmenu();

    postordel(root);
    return 0;
}