const prompt = require("prompt-sync")({ sigint: true });

const Stack = require("./Stack");
const ComputerParameterMode = require("./ComputerParameterMode");
const { DeepClone } = require("./common");

/**
 * An Intcode Computer for the Advent of Code 2019 challenge
 *
 * @author Apis Necros
 */
module.exports = class Computer {
    constructor(stack) {
        this._initialMemory = DeepClone(stack);
        this.stack = new Stack(stack);
        this.OPCODES = {
            ADD: 1,
            MULTIPLY: 2,
            INPUT: 3,
            OUTPUT: 4,
            HALT: 99,
        };

        this.parameterMode = ComputerParameterMode.POSITION_MODE;
    }

    /**
     * Run the computer
     *
     * Runs opcodes on the stack until either the a HALT command is
     * encountered, or an error is thrown.
     * @returns {void}
     */
    Run() {
        // eslint-disable-next-line no-empty
        while (this.Execute(this.stack.Get(ComputerParameterMode.IMMEDIATE_MODE)) === true) { }
    }

    /**
     * Execute a call using the provided opcode
     *
     * @param {number} rawOpcode A opcode to execute
     * @returns {boolean} False if the opcode was HALT, otherwise true
     */
    Execute(rawOpcode) {
        let status = true;

        const opcode = rawOpcode % 100;

        // console.log(`DEBUG: opcode: ${opcode}`);
        switch (opcode) {
            case this.OPCODES.ADD: {
                this.Operation_Add(rawOpcode);
                break;
            }
            case this.OPCODES.MULTIPLY: {
                this.Operation_Multiply(rawOpcode);
                break;
            }
            case this.OPCODES.INPUT: {
                this.Operation_Input();
                break;
            }
            case this.OPCODES.OUTPUT: {
                this.Operation_Output();
                break;
            }
            case this.OPCODES.HALT:
                status = false;
                break;
            default:
                throw Error(`Opcode ${opcode} not found\nMemdump: ${JSON.stringify(this.stack.Dump())}`);
        }

        this.stack.Next();

        return status;
    }

    /**
     * Parse operands based on the current parameter mode
     *
     * When the int computer is in Immediate Mode, the values are returned
     * as-is. When in Position Mode, the operands are used as memory
     * addresses, and the values at those addresses are returned instead.
     *
     * @returns {number[]} The parsed list of operands
     */
    _ParseOperands(...operands) {
        if (this.parameterMode == ComputerParameterMode.IMMEDIATE_MODE) { return operands; }
        return operands.map((operand) => this.stack.Get(operand));
    }

    /**
     * Execute the Add opcode
     *
     * Adds two numbers and stores the result at the provided position
     * on the stack.
     *
     * Parses the operand Parameter Mode out of the opcode used to make
     * this call.
     *
     * @param {number} rawOpcode The opcode in memory used to make this call
     * @returns {void}
     */
    Operation_Add(rawOpcode) {
        const operandLeftMode = ComputerParameterMode.ParseParameterMode(rawOpcode, 1);
        const operandRightMode = ComputerParameterMode.ParseParameterMode(rawOpcode, 2);

        const operandLeft = this.stack.Next().Get(operandLeftMode);
        const operandRight = this.stack.Next().Get(operandRightMode);
        const outputPosition = this.stack.Next().Get(ComputerParameterMode.IMMEDIATE_MODE);

        const newValue = operandLeft + operandRight;
        this.stack.Put(outputPosition, newValue);
    }

    /**
     * Execute the Multiply opcode
     *
     * Multiplies two numbers and stores the result at the provided
     * position on the stack.
     *
     * @param {number} rawOpcode The opcode in memory used to make this call
     * @returns {void}
     */
    Operation_Multiply(rawOpcode) {
        const operandLeftMode = ComputerParameterMode.ParseParameterMode(rawOpcode, 1);
        const operandRightMode = ComputerParameterMode.ParseParameterMode(rawOpcode, 2);

        const operandLeft = this.stack.Next().Get(operandLeftMode);
        const operandRight = this.stack.Next().Get(operandRightMode);
        const outputPosition = this.stack.Next().Get(ComputerParameterMode.IMMEDIATE_MODE);

        const newValue = operandLeft * operandRight;
        this.stack.Put(outputPosition, newValue);
    }

    /**
     * Execute the Input opcode
     *
     * Prompts the user to input a value from the command line
     *
     * @returns {void}
     */
    Operation_Input() {
        const outputPosition = this.stack.Next().Get(ComputerParameterMode.IMMEDIATE_MODE);

        let userInput;

        do {
            userInput = Number(prompt("Please enter a number: "));
        } while (Number.isNaN(userInput));

        this.stack.Put(outputPosition, userInput);
    }

    /**
     * Execute the OUTPUT opcode
     *
     * @returns {void}
     */
    Operation_Output() {
        const outputPosition = this.stack.Next().Get(ComputerParameterMode.IMMEDIATE_MODE);

        console.log(this.stack.GetAtIndex(outputPosition, ComputerParameterMode.IMMEDIATE_MODE));
    }

    /**
     * Outputs the computer's stack to the console
     * @returns {void}
     */
    DumpMemory() {
        console.log(this.stack.Dump());
    }

    /**
     * Resets the computer's memory to the value it was created with
     *
     * @returns {void}
     */
    Reset() {
        this.stack = new Stack(this._initialMemory);
    }

    /**
     * Sets the computer's memory to a new stack
     *
     * Note: This resets the computer's initial memory, so `Reset` will use this value
     *
     * @param {number[]} stack The new memory stack for the computer
     * @returns {void}
     */
    SetMemory(stack) {
        this._initialMemory = DeepClone(stack);
        this.stack = new Stack(stack);
    }
};