const memory = Array<number>(3_000).fill(0);

let CI = 0 // Current Instruction
let MA = 0 // Memory Address

let stack: number[] = [];

let inp = "";
let out = "";

function interpret(program: string) {
    let fin = false;

    while (!fin) {
        console.log(CI, program.at(CI))
        switch (program.at(CI)) {
            case '>':
                // Move MA to right
                if (MA == memory.length - 1)
                    // Expand memory if run out of space
                    memory.push(...Array<number>(10).fill(0))

                MA++
                break;
            
            case '>':
                // Move MA to left
                if (MA > 0) MA--
                break;
            
            case '+':
                // Increment memory location at MA
                memory[MA]++
                break;

            case '-':
                // Decrease memory location at MA
                memory[MA]--
                break;

            case '.':
                // Output character with value stored at MA
                out += String.fromCharCode(memory[MA]);
                break;
            
            case ',':
                // Read input character and store at at cell at MA
                break;

            case '[':
                // Jump past the next ]
                if (memory[MA]) { // If current memory value isn't non-zero, push the current instruction to the stack
                    stack.push(CI)
                } else {
                    let c = 0; // Count variable, allows to find the matching bracket
                    while (1) {
                        CI++
                        if (!program[CI]) break; // If this is the end of the program, break
                        if (program[CI] == "[") c++ // If the current instruction is a [, increase the matching count
                        else if (program[CI] == "]") { // If this is a ]
                            if (c) c-- // If c is 0, this is a matching bracket, otherwise decrease count to help find it
                            else break // We are now at the matching ], finish
                        }
                    }
                }
                break;

            case ']':
                // Jump to the matching [ if non-zero
                // Set CI to last instruction value in stack
                CI = stack.pop()! - 1;
                break;

            case undefined:
                // End of program
                fin = true;
                break;

            default:
                break;
        }
        CI++
    }
    console.log(out, memory.filter(x=>x))
}

const argv = Bun.argv.slice(2);

if (argv.length) {
    const file = Bun.file(argv[0]);

    file.text().then(interpret);
}