Insertion Sort

#include <iostream>
#include <fstream>
#include <string>       //seems like I can't get the <getline> function to work without initializing <string> header

using namespace std;

struct product {
    int ID;
    string name;
    float price;
};

void insertionSort(product array[], const int);
void printArray(product array[], const int);
void textfilein(product array[], const int);
void textfileout();

int main() {
    const int size = 5;
    product p[size] = {{105, "Once again, I made something worthless, by Goemon", 5437.85}, {193, "Time Machine (Prototype)", 2212.12}, {102, "Bamboo Helicam", 176.19}, {106, "Cyalume Saber", 0.20}, {104, "Moad Snake", 4078.39}};

    cout << "--------------------------------------------------------------------------------------------------\n";
    cout << "The products are: \n\n";
    textfilein(p, size);       //text file input then output
    textfileout();

    cout << "--------------------------------------------------------------------------------------------------\n";
    cout << "The product after sort are: \n\n";
    insertionSort(p, size);     //do insertion sort then text file input then output
    textfilein(p, size);
    textfileout();

    return 0;
}

void insertionSort(product arr[], const int n)      //insertion sort, a copypasta from kan Gabumpa report
{
    for (int i = 1; i < n; i++)
    {
        int key = arr[i].ID;        //initialize <ID> since amo la an ig cocompare na value dire na an iba na aada <struct>
        product key2 = arr[i];      //initialize another key but this is only for a <key> to hold value to swap later. swapping doesn't work without this
        int j = i - 1;

        // Move elements of arr[0..i-1],        //a copypasta comment, just leaves it there for quality purposes
        // that are greater than key, to one
        // position ahead of their
        // current position
        while (j >= 0 && arr[j].ID > key)
        {
            arr[j + 1] = arr[j];
            j = j - 1;
        }
        arr[j + 1] = key2;
    }
}

void printArray(product arr[], const int n)     //did use this to try if the insertion sort works but ignores after implementing text files databases
{
    for (int i = 0; i < n; i++) {
        cout << "ID: " << arr[i].ID << "\n";
        cout << "Name: " << arr[i].name << "\n";
        cout << "Price: " << arr[i].price << " PHP \n\n";
    }
}

void textfilein(product arr[], const int n) {       //for text file to record the values
    fstream tf;

    tf.open("LAF2textfile.txt");
    for (int i = 0; i < n; i++) {
        tf << "ID: " << arr[i].ID << "\n";
        tf << "Name: " << arr[i].name << "\n";
        tf << "Price: " << arr[i].price << " PHP \n\n";
    }
    tf.close();
}

void textfileout() {        //outputs the values/lines in the text file
    fstream tf;
    string line;

    tf.open("LAF2textfile.txt");
    while (getline(tf, line)) {
        cout << line << "\n";
    }
    tf.close();
}