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

int copy_char_by_char(FILE * input, FILE * output) {
    for (int c = fgetc(input); c != EOF; c = fgetc(input))
	if (fputc(c, output) == EOF){
	    fprintf(stderr, "could not write into output file\n");
	    return 0;
	}
    return 1;
}

int copy_with_buffer(FILE * input, FILE * output) {
    char buffer[1024];
    size_t s;
    while ((s = fread(buffer, sizeof(char), 1024, input)) > 0) {
	size_t w = 0;
	do {
	    w += fwrite(buffer, sizeof(char), s - w, input);
	    if (w == 0){
		fprintf(stderr, "could not write into output file\n");
		return 0;
	    }
	} while (w < s);
    }
    return 0;
}

/* syntax: ./copy -c file1 file2
 *
 * makes a copy of file1 into a new file file2
 */
int main(int argc, char * argv[]) {
    FILE * input;
    FILE * output;
    int buffer;
    const char * input_fname;
    const char * output_fname;

    switch (argc) {
    case 1:
    case 2:
	fprintf(stderr, "usage: %s [b=<buffer-size>] <source-file> <dest-file>\n", argv[0]);
	return 1;
    case 3:
	input_fname = argv[1];
	output_fname = argv[2];
	buffer = 0;
	break;
    default:
	if (strcmp(argv[1], "-b") != 0) {
	    fprintf(stderr, "usage: %s [-b] <source-file> <dest-file>\n", argv[0]);
	    return 1;
	}
	buffer = 1;
	input_fname = argv[2];
	output_fname = argv[3];
    }

    input = fopen(input_fname, "rb");
    if (input == 0) {
	fprintf(stderr, "could not open file %s for reading\n", argv[1]);
	return 1;
    }

    output = fopen(output_fname, "wb");
    if (output == 0) {
	fprintf(stderr, "could not open file %s for writing\n", argv[2]);
	fclose(input);
	return 1;
    }
    if (buffer)
	copy_with_buffer(input, output);
    else
	copy_char_by_char(input, output);
    fclose(input);
    fclose(output);
}