brainfuck.ts

import { parse } from "https://deno.land/std@0.180.0/flags/mod.ts";

interface Indexable {
    [index: number]: number;
    length: number;
}

const args = parse(Deno.args);

if (args.help || args.program === undefined) {
    const scriptName =
        (await Deno.permissions.query({ name: "read" })).state === "granted"
            ? Deno.mainModule.split("/").at(-1)
            : "brainfuck.ts";
    console.log(scriptName + " - a brainfuck runner");
    console.log(`Usage: deno run ${scriptName} [OPTIONS]`);
    console.log("Options:");
    console.log("--program <program>: The brainfuck program to run");
    console.log(
        "--cellLength <length>: The number of the cells. If -1 or not specified, infinite cells"
    );
    console.log(
        "--disallowComments: Disallow any character in the program which isn't +-<>[],."
    );
    console.log(
        "--check <runtime or start>: When to check the program. Defaults to runtime"
    );
    console.log(
        "--size <uint8 or unlimited>: size of each cell, default unlimited"
    );
    Deno.exit(1);
}

const prog = args.program as string;
const runtimeChecking = !(args.check && args.check === "start");
const bracketMap = new Map<number, number>();
if (!runtimeChecking) {
    const openBracketStack = [];
    for (let i = 0; i < prog.length; i++) {
        const char = args.program[i];
        if (char === "[") {
            openBracketStack.push(i);
        } else if (char === "]") {
            if (openBracketStack.length === 0) {
                console.log("Unmatched close bracket at " + i);
                Deno.exit(1);
            }
            const value = openBracketStack.pop()!;
            bracketMap.set(value, i);
            bracketMap.set(i, value);
        }
    }
    if (openBracketStack.length > 0) {
        console.log("Umatched open bracket at " + openBracketStack.pop());
        Deno.exit(1);
    }
} else if (args.check && args.check !== "runtime") {
    console.log(`Unsupported check type ${args.check}`);
    Deno.exit(1);
}

const cellSize = (args.cellLength as number) ?? -1;
if (cellSize === 0) {
    console.log("Cell size cannot be 0");
    Deno.exit(1);
}
const isUint8 = args.size === "uint8";
if (!isUint8 && args.size && args.size !== "unlimited") {
    console.log(`Unsupported size type ${args.size}`);
    Deno.exit(1);
}
const state: Indexable =
    isUint8 && cellSize !== -1 ? new Uint8Array(cellSize) : [0];
let pointer = 0;
let curCommand = 0;
const disallowComments = args.disallowComments;

while (true) {
    const command = prog[curCommand];
    switch (command) {
        case ">":
            pointer++;
            if (pointer == state.length) {
                if (cellSize == -1 || (state.length < cellSize && !isUint8)) {
                    (state as number[]).push(0);
                } else {
                    console.log("new pointer > cell size");
                    Deno.exit(1);
                }
            }
            break;
        case "<":
            pointer--;
            if (pointer < 0) {
                console.log("pointer < 0");
                Deno.exit(1);
            }
            break;
        case "+":
            state[pointer]++;
            break;
        case "-":
            state[pointer]--;
            break;
        case ".":
            await Deno.stdout.write(new Uint8Array([state[pointer]]));
            break;
        case ",":
            const buf = new Uint8Array(1);
            let read = await Deno.stdin.read(buf);
            if (read != 1) {
                console.log("IO error");
                Deno.exit(1);
            }
            state[pointer] = buf[0];
            break;
        case "[":
            if (state[pointer] == 0) {
                if (runtimeChecking) {
                    const oldCurCommand = curCommand;
                    let openBracketCount = 0;
                    while (true) {
                        curCommand++;
                        if (runtimeChecking && curCommand === prog.length) {
                            console.log(
                                "Unmatched open bracket at " + oldCurCommand
                            );
                            Deno.exit(1);
                        }
                        if (prog[curCommand] == "]" && openBracketCount == 0) {
                            break;
                        } else if (prog[curCommand] == "]") {
                            openBracketCount--;
                        } else if (prog[curCommand] == "[") {
                            openBracketCount++;
                        }
                    }
                } else {
                    // not runtime checking implies that the bracketMap is populated
                    curCommand = bracketMap.get(curCommand)!;
                }
            }
            break;
        case "]":
            if (state[pointer] != 0) {
                if (runtimeChecking) {
                    let closeBracketCount = 0;
                    const oldCurCommand = curCommand;
                    while (true) {
                        curCommand--;
                        if (runtimeChecking && curCommand === -1) {
                            console.log(
                                "Unmatched close bracket at " + oldCurCommand
                            );
                            Deno.exit(1);
                        }
                        if (prog[curCommand] == "[" && closeBracketCount === 0) {
                            break;
                        } else if (prog[curCommand] == "[") {
                            closeBracketCount--;
                        } else if (prog[curCommand] == "]") {
                            closeBracketCount++;
                        }
                    }
                } else {
                    curCommand = bracketMap.get(curCommand)!;
                }
            }
            break;
        default:
            if (disallowComments) {
                console.log(
                    "comment at char " +
                        curCommand +
                        " not allowed due to --disallowComments"
                );
                Deno.exit(0);
            }
    }
    curCommand++;
    if (curCommand == prog.length) {
        break;
    }
}