/* CBF (Coed Brainfuck) Interpreter */

#load "io.h2"
#load "lib.h2"
#load "ntl.h2"
#load "str.h2"
#load "stat.h2"

#define ASCII   255
#define BYTE    5000
#define RDNLY   "-r"

struct Pointer
{
    array = [null];
    loops = [];
    ptr = 0;
};

struct File
{
    descriptor = 0;
    plength = 0;
    string = "";
};

function create_pointer();
function starting_file(file_name);

function increase(*ptr);
function decrease(*ptr);

function start_loop(*loop, counter);
function end_loop(*pointer, *counter);

function main(argc, argv)
{
    pointer = create_pointer();

    if (!argv[1])
    {
        fprintf(stderr, "Usage: % <file name>\n", argv[0]);
        exit(1);
    }

    if (!strfind(argv[1], /.+\.bf/))
    {
        fprintf(stderr, "Cannot read file %\n", argv[1]);
        exit(1);
    }

    file = starting_file(argv[1]);

    for (i = 0; i < file.plength; i++)
    {
        switch (file.string[i])
        {
            case '<':
                decrease(&pointer.ptr, BYTE);
                break;

            case '>':
                increase(&pointer.ptr, BYTE);
                break;

            case '+':
                increase(&pointer.array[pointer.ptr], ARRAY);
                break;

            case '-':
                decrease(&pointer.array[pointer.ptr], ARRAY);
                break;

            case '.':
                putchar(pointer.array[pointer.ptr]);
                break;

            case ',':
                pointer.array[pointer.ptr] = getchar();
                break;

            case '[':
                start_loop(&pointer.loops, i);
                break;

            case ']':
                end_loop(&pointer, &i);
                break;
        }
    }

    close(file.descriptor);
    return 0;
}

function create_pointer()
{
    pointer = Pointer;

    for (i = 0; i < BYTE; i++)
    {
        pointer.array[i] = 0;
    }

    return pointer;
}

function starting_file(file_name)
{
    file = File;

    if ((file.descriptor = open(file_name, RDNLY)) < 0)
    {
        fprintf(stderr, "File % doesn't exist\n", file_name);
        exit(1);
    }

    file.string = read(file.descriptor);
    file.plength = length(file.string);

    return file;
}

function increase(*ptr, limit)
{
    if (*ptr == limit)
    {
        *ptr = 0;
    }
    else
    {
        ++(*ptr);
    }
}

function decrease(*ptr, limit)
{
    if (!*ptr)
    {
        *ptr = limit;
    }
    else
    {
        --(*ptr);
    }
}

function start_loop(*loop, counter)
{
    push(*loop, counter);
}

function end_loop(*pointer, *counter)
{
    if (*pointer->array[*pointer->ptr])
    {
        pop(*pointer->loops);
    }
    else
    {
        *counter = *pointer->loops[length(*pointer->loops) - 1];
    }
}