/*
braindrain.d

a brainfuck interpreter

compile with dmd braindrain.d
usage: only with the brainfuck program as parameter
example:
    $ braindrain ",[..,]"
    it should print your entered key's twice, till you kill the process
testet with dmd 1.014 on Windows XP
future improvements: add fileusage instead of parameter's
*/

import std.stdio;
import std.cstream;

class Stack(T)
{
    private T[] data;
    private T lastone;

    public void push(T element)
    {
        data.length = data.length + 1;
        data[data.length - 1] = element;
    }

    public T pop()
    {
        if (data.length > 0)
        {
            lastone = this.last;
            data.length = data.length - 1;
            return lastone;
        }
        else assert(0);
    }

    public T last()
    {
        return data[data.length - 1];
    }
}

int main(char[][] args)
{
    char[300_000] speicher;
    for(int i = 0; i < 300_000; i++) { speicher[i] += 1; }
    int position, kommandoindex = 0;
    Stack!(char) klammernstack = new Stack!(char);
    char[] kommandos;

    try
    {
        kommandos = args[1];
    }
    catch
    {
        writefln("No Args? Try this out:");
        writefln("braindrain \"++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.\"");
        writefln("It should print 'Hello'");
    }

    while (kommandoindex < kommandos.length)
        {
            switch (kommandos[kommandoindex])
            {
            case '>':
                position += 1;
                break;
            case '<':
                position -= 1;
                break;
            case '+':
                speicher[position] += 1;
                break;
            case '-':
                speicher[position] -= 1;
                break;
            case '.':
                writef(speicher[position]);
                break;
            case ',':
                dout.flush;
                speicher[position] = getch;
                break;
            case '[':
                klammernstack.push(kommandoindex);
                break;
            case ']':
                if (speicher[position] != 0)
                {
                    kommandoindex = klammernstack.last;
                }
                else
                {
                    klammernstack.pop;
                }
                break;
            default: break;
            }
            kommandoindex += 1;
        }
    return 0;
}