filehandle3.cpp

#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

// Reads lines from file into vector
vector<string> readLines(string filename) {
    ifstream infile(filename.c_str());
    vector<string> lines;
    string line;

    while (getline(infile, line)) {
        lines.push_back(line);
    }
    infile.close();
    return lines;
}

// Writes lines from vector to file
void writeLines(string filename, const vector<string>& lines) {
    ofstream outfile(filename.c_str());
    for (int i = 0; i < lines.size(); i++) {
        outfile << lines[i] << endl;
    }
    outfile.close();
}

// Display lines with line numbers
void displayLines(const vector<string>& lines) {
    cout << "\nFile content:\n";
    for (int i = 0; i < lines.size(); i++) {
        cout << i + 1 << ": " << lines[i] << endl;
    }
}

// Backup original file
void backupFile(string filename) {
    vector<string> lines = readLines(filename);
    string backupName = filename + ".bak";
    writeLines(backupName, lines);
    cout << "Backup saved as: " << backupName << endl;
}

// Edit multiple lines
void editLines(vector<string>& lines) {
    int count;
    cout << "How many lines do you want to edit? ";
    cin >> count;

    for (int i = 0; i < count; i++) {
        int lineNumber;
        cout << "\nEnter line number to edit (1 to " << lines.size() << "): ";
        cin >> lineNumber;

        if (lineNumber < 1 || lineNumber > lines.size()) {
            cout << "Invalid line number. Skipping.\n";
            continue;
        }

        cin.ignore(); // clear input buffer
        string newText;
        cout << "Enter new text for line " << lineNumber << ": ";
        getline(cin, newText);

        lines[lineNumber - 1] = newText;
    }
}

// Add new line
void addLine(vector<string>& lines) {
    cin.ignore();
    string newText;
    cout << "Enter text to add as new line: ";
    getline(cin, newText);
    lines.push_back(newText);
    cout << "Line added at the end.\n";
}

// Delete a line
void deleteLine(vector<string>& lines) {
    int lineNumber;
    cout << "Enter line number to delete (1 to " << lines.size() << "): ";
    cin >> lineNumber;

    if (lineNumber < 1 || lineNumber > lines.size()) {
        cout << "Invalid line number.\n";
        return;
    }

    lines.erase(lines.begin() + (lineNumber - 1));
    cout << "Line deleted.\n";
}

int main() {
    string filename;
    int choice;

    cout << "Enter file name: ";
    cin >> filename;

    vector<string> lines = readLines(filename);

    do {
        cout << "\n--- Menu ---\n";
        cout << "1. Display file content\n";
        cout << "2. Edit lines\n";
        cout << "3. Add new line\n";
        cout << "4. Delete line\n";
        cout << "5. Backup file\n";
        cout << "6. Save and exit\n";
        cout << "Enter your choice: ";
        cin >> choice;

        switch (choice) {
            case 1:
                displayLines(lines);
                break;
            case 2:
                editLines(lines);
                break;
            case 3:
                addLine(lines);
                break;
            case 4:
                deleteLine(lines);
                break;
            case 5:
                backupFile(filename);
                break;
            case 6:
                writeLines(filename, lines);
                cout << "Changes saved. Exiting.\n";
                break;
            default:
                cout << "Invalid choice.\n";
        }
    } while (choice != 6);

    return 0;
}