/*
    arrays2d.c

	Jeff Ondich, 6 Jan 2022

    Demonstrating the strange world of 2-dimensional arrays in C.
*/

#include <stdio.h>
#include <stdlib.h>

#define MAX_ROW_COUNT 30
#define MAX_COLUMN_COUNT 50

void fill_grid(char grid[][MAX_COLUMN_COUNT], int row_count, int column_count);
void swap_rows(char grid[][MAX_COLUMN_COUNT], int row_index_1, int row_index_2, int column_count);
void print_grid(char grid[][MAX_COLUMN_COUNT], int row_count, int column_count, FILE *output_stream);

int main(int argc, char *argv[]) {
    // Start with a 2D array, fill it with some stuff, and swap
    // a couple rows before printing the results. We're allocating
    // the memory statically here in main, but we'll discuss doing
    // the allocation dynamically (i.e. with malloc) on another day.
    char grid[MAX_ROW_COUNT][MAX_COLUMN_COUNT];
    int row_count = 8;
    int column_count = 30;

    fill_grid(grid, row_count, column_count);

    printf("Before:\n");
    print_grid(grid, row_count, column_count, stdout);

    swap_rows(grid, 1, 6, column_count);

    printf("After:\n");
    print_grid(grid, row_count, column_count, stdout);

    return 0;
}

// Fills the grid with a row of A's, a row of B's, etc. up to row_count. Only
// columns up to column_count are filled (the rest of the allocated space, if
// any, is left unchanged.
void fill_grid(char grid[][MAX_COLUMN_COUNT], int row_count, int column_count) {
    char ch = 'A';
    for (int row = 0; row < row_count; row++) {
        for (int column = 0; column < column_count; column++) {
            grid[row][column] = ch;           
        }
        ch++;
    }
}

// Swaps the contents of the specified rows in the grid (only swapping column data
// up to the specified column count).
void swap_rows(char grid[][MAX_COLUMN_COUNT], int row_index_1, int row_index_2, int column_count) {
    for (int column = 0; column < column_count; column++) {
        char saved_char = grid[row_index_1][column];
        grid[row_index_1][column] = grid[row_index_2][column];
        grid[row_index_2][column] = saved_char;
    }
}

// Prints the contents of the grid (only printing data stored in the specified
// range of rows and columns).
void print_grid(char grid[][MAX_COLUMN_COUNT], int row_count, int column_count, FILE *output_stream) {
    for (int row = 0; row < row_count; row++) {
        for (int column = 0; column < column_count; column++) {
            fputc(grid[row][column], output_stream);
        }
        fputc('\n', output_stream);
    }
    fputc('\n', output_stream);
}