#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#define FILENAME "database.dat"
 
// Define record structure
struct Record {
    int id;
    char name[50];
    int age;
    float salary;
};
 
// Function prototypes
void addRecord();
void displayRecords();
void searchRecord();
void updateRecord();
void deleteRecord();
 
int main() {
    int choice;
 
    while (1) {
        printf("\n========= MINI DATABASE SYSTEM =========\n");
        printf("1. Add Record\n");
        printf("2. Display All Records\n");
        printf("3. Search Record\n");
        printf("4. Update Record\n");
        printf("5. Delete Record\n");
        printf("6. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);
 
        switch (choice) {
            case 1: addRecord(); break;
            case 2: displayRecords(); break;
            case 3: searchRecord(); break;
            case 4: updateRecord(); break;
            case 5: deleteRecord(); break;
            case 6: exit(0);
            default: printf("Invalid choice!\n");
        }
    }
    return 0;
}
 
// Function to add a new record
void addRecord() {
    FILE *fp;
    struct Record rec;
 
    fp = fopen(FILENAME, "ab"); // append binary mode
    if (fp == NULL) {
        printf("Error opening file!\n");
        return;
    }
 
    printf("Enter ID: ");
    scanf("%d", &rec.id);
    printf("Enter Name: ");
    getchar(); // clear newline
    fgets(rec.name, sizeof(rec.name), stdin);
    rec.name[strcspn(rec.name, "\n")] = '\0'; // remove newline
    printf("Enter Age: ");
    scanf("%d", &rec.age);
    printf("Enter Salary: ");
    scanf("%f", &rec.salary);
 
    fwrite(&rec, sizeof(rec), 1, fp);
    fclose(fp);
 
    printf("Record added successfully!\n");
}
 
// Function to display all records
void displayRecords() {
    FILE *fp;
    struct Record rec;
 
    fp = fopen(FILENAME, "rb");
    if (fp == NULL) {
        printf("No records found!\n");
        return;
    }
 
    printf("\n%-10s %-20s %-10s %-10s\n", "ID", "Name", "Age", "Salary");
    printf("---------------------------------------------------\n");
 
    while (fread(&rec, sizeof(rec), 1, fp)) {
        printf("%-10d %-20s %-10d %-10.2f\n", rec.id, rec.name, rec.age, rec.salary);
    }
 
    fclose(fp);
}
 
// Function to search for a record by ID
void searchRecord() {
    FILE *fp;
    struct Record rec;
    int id, found = 0;
 
    fp = fopen(FILENAME, "rb");
    if (fp == NULL) {
        printf("File not found!\n");
        return;
    }
 
    printf("Enter ID to search: ");
    scanf("%d", &id);
 
    while (fread(&rec, sizeof(rec), 1, fp)) {
        if (rec.id == id) {
            printf("\nRecord Found:\n");
            printf("ID: %d\nName: %s\nAge: %d\nSalary: %.2f\n",
                   rec.id, rec.name, rec.age, rec.salary);
            found = 1;
            break;
        }
    }
 
    if (!found)
        printf("Record not found!\n");
 
    fclose(fp);
}
 
// Function to update a record by ID
void updateRecord() {
    FILE *fp;
    struct Record rec;
    int id, found = 0;
    long pos;
 
    fp = fopen(FILENAME, "r+b"); // read/write binary mode
    if (fp == NULL) {
        printf("File not found!\n");
        return;
    }
 
    printf("Enter ID to update: ");
    scanf("%d", &id);
 
    while (fread(&rec, sizeof(rec), 1, fp)) {
        if (rec.id == id) {
            printf("Enter new Name: ");
            getchar(); // clear newline
            fgets(rec.name, sizeof(rec.name), stdin);
            rec.name[strcspn(rec.name, "\n")] = '\0';
            printf("Enter new Age: ");
            scanf("%d", &rec.age);
            printf("Enter new Salary: ");
            scanf("%f", &rec.salary);
 
            pos = ftell(fp) - sizeof(rec);
            fseek(fp, pos, SEEK_SET);
            fwrite(&rec, sizeof(rec), 1, fp);
 
            printf("Record updated successfully!\n");
            found = 1;
            break;
        }
    }
 
    if (!found)
        printf("Record not found!\n");
 
    fclose(fp);
}
 
// Function to delete a record by ID
void deleteRecord() {
    FILE *fp, *temp;
    struct Record rec;
    int id, found = 0;
 
    fp = fopen(FILENAME, "rb");
    if (fp == NULL) {
        printf("File not found!\n");
        return;
    }
 
    temp = fopen("temp.dat", "wb");
    if (temp == NULL) {
        printf("Error creating temp file!\n");
        fclose(fp);
        return;
    }
 
    printf("Enter ID to delete: ");
    scanf("%d", &id);
 
    while (fread(&rec, sizeof(rec), 1, fp)) {
        if (rec.id == id) {
            found = 1;
        } else {
            fwrite(&rec, sizeof(rec), 1, temp);
        }
    }
 
    fclose(fp);
    fclose(temp);
 
    remove(FILENAME);
    rename("temp.dat", FILENAME);
 
    if (found)
        printf("Record deleted successfully!\n");
    else
        printf("Record not found!\n");
}