#!/usr/bin/env node

console.time("Compiled in");

const fs = require("fs");
const args = process.argv.slice(2, process.argv.length);

if (!args[0] && args[0] !== 0) {
  console.error("Usage: mblf <input file> <output file>");
  process.exit(1);
} else if (!args[1] && args[1] !== 0) {
  console.error("Error: Please provide an output path.");
  process.exit(1);
}

function parseNum(number) {
  if (typeof number == "string") {
    if (number.startsWith("0x")) {
      return parseInt(number.slice(2, number.length), 16);
    } else if (number.startsWith("\"") && number.endsWith("\"")) {
      return number.charCodeAt(1);
    } else {
      return parseInt(number);
    }
  } else {
    return number;
  }
}

let bfOutput = [];
let variables = [];
let ptr = 0;
let prevPtr = 0;

function instruct(instruction, arg) {
  let pointedVariable;
  let number;
  switch (instruction) {
    case "var":
      if (variables.indexOf(arg) != -1) {
        return `${arg} already exists.`;
      }
      let emptyAddress = 0;
      while (!(variables[emptyAddress] === undefined)) {
        emptyAddress++;
      }
      variables[emptyAddress] = arg;
    break;
    case "delvar":
      delete variables[variables.indexOf(arg)];
    break;
    case "point":
      if (bfOutput[bfOutput.length-1] !== undefined &&
         (bfOutput[bfOutput.length-1].endsWith("<") ||
          bfOutput[bfOutput.length-1].endsWith(">"))) {
        bfOutput.pop();
        ptr = prevPtr;
      }
      let variable = variables.indexOf(arg);
      if (variable == -1) {
        return `${arg} is not a variable.`;
      }
      let distance = variable - ptr;
      prevPtr = ptr;
      if (distance > 0) {
        bfOutput.push(">".repeat(distance));
      } else if (distance < 0) {
        bfOutput.push("<".repeat(-distance));
      }
      ptr = variable;
    break;
    case "pointm":
      bfOutput.push("<+[-<+]-"); // thank you mixtela
      ptr = variables.indexOf(arg);
    break;
    case "add":
      number = parseNum(arg);
      if (Number.isNaN(number)) {
        return "Failed to parse number.";
      }
      bfOutput.push("+".repeat(number));
    break;
    case "addb":
      number = parseNum(arg);
      if (Number.isNaN(number)) {
        return "Failed to parse number.";
      }
      pointedVariable = variables[ptr];
      instruct("var", "__temp");
      instruct("point", "__temp");
      instruct("add", Math.floor(number / 16));
      bfOutput.push("[");
      instruct("sub", "1");
      instruct("point", pointedVariable);
      instruct("add", "16");
      instruct("point", "__temp");
      bfOutput.push("]");
      instruct("point", pointedVariable);
      instruct("add", number - Math.floor(number / 16) * 16);
      instruct("delvar", "__temp");
    break;
    case "addv":
      pointedVariable = variables[ptr];
      bfOutput.push("[");
      instruct("sub", "1");
      instruct("point", arg);
      instruct("add", "1");
      instruct("point", pointedVariable);
      bfOutput.push("]");
    break;
    case "sub":
      number = parseNum(arg);
      if (Number.isNaN(number)) {
        return "Failed to parse number.";
      }
      bfOutput.push("-".repeat(number));
    break;
    case "subb":
      number = parseNum(arg);
      if (Number.isNaN(number)) {
        return "Failed to parse number.";
      }
      pointedVariable = variables[ptr];
      instruct("var", "__temp");
      instruct("point", "__temp");
      instruct("add", Math.floor(number / 10));
      bfOutput.push("[");
      instruct("sub", "1");
      instruct("point", pointedVariable);
      instruct("sub", "10");
      instruct("point", "__temp");
      bfOutput.push("]");
      instruct("point", pointedVariable);
      instruct("sub", number - Math.floor(number / 10) * 10);
      instruct("delvar", "__temp");
    break;
    case "subv":
      pointedVariable = variables[ptr];
      bfOutput.push("[");
      instruct("sub", "1");
      instruct("point", arg);
      instruct("sub", "1");
      instruct("point", pointedVariable);
      bfOutput.push("]");
    break;
    case "copy":
      pointedVariable = variables[ptr];
      instruct("var", "__temp");
      bfOutput.push("[");
      instruct("sub", "1");
      instruct("point", arg);
      instruct("add", "1");
      instruct("point", "__temp");
      instruct("add", "1");
      instruct("point", pointedVariable);
      bfOutput.push("]");
      instruct("point", "__temp");
      bfOutput.push("[");
      instruct("sub", "1");
      instruct("point", pointedVariable);
      instruct("add", "1");
      instruct("point", "__temp");
      bfOutput.push("]");
      instruct("delvar", "__temp");
    break;
    case "setz":
      bfOutput.push("[-]");
    break;
    case "getchr":
      bfOutput.push(",");
    break;
    case "print":
      bfOutput.push(".");
    break;
    case "[":
      bfOutput.push("[");
    break;
    case "]":
      bfOutput.push("]");
    break;
    default:
      if (instruction !== "") {
        return `${instruction} is not an instruction.`
      }
    break;
  }
}

function runMblf(inputFile) {
  let file;
  try {
    file = fs.readFileSync(inputFile, "utf8")
  } catch (e) {
    console.error(`Error: ${e.message}`);
    process.exit(1);
  }
  return file
    .replace(/\r/gm, "")
    .split("\n")
    .forEach((item, line) => {
      let statement = item.split(";;")[0].trim().split(" ");
      if (statement[0] == "#include") {
        try {
          runMblf(item.split("\"")[1]);
        } catch (e) {
          if (e.name == "RangeError" && e.message == "Maximum call stack size exceeded") {
            console.error(`[${inputFile}] Error in line ${line+1}: Call stack size exceeded. Check for cyclic dependencies.`);
            process.exit(1);
          } else {
            throw e;
          }
        }
      } else {
        let instructAttempt = instruct(statement[0], statement.slice(1, statement.length).join(" "));
        if (instructAttempt !== undefined) {
          console.error(`[${inputFile}] Error in line ${line+1}: ${instructAttempt}`);
          process.exit(1);
        }
      }
    });
}

runMblf(args[0]);
fs.writeFileSync(args[1], bfOutput.join(""));

console.timeEnd("Compiled in");