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

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

module.exports = class Computer {
    /**
     * An Intcode Computer for the Advent of Code 2019 challenge
     *
     * @author Apis Necros
     *
     * @param {number[]} stack The initial memory to load into the computer
     * @param {Object} options Options that can be enabled within the computer
     * @param {boolean} options.followPointer When true, the memory will be dumped every call to Execute with the current instruction highlighted
     * @param {number} options.tickRate The number of milliseconds between calls to Execute. Initializes to 0.
     */
    constructor(stack, options = {}) {
        this._initialMemory = DeepClone(stack);
        this.stack = new Stack(stack);
        this.OPCODES = {
            ADD: 1,
            MULTIPLY: 2,
            INPUT: 3,
            OUTPUT: 4,
            JUMP_IF_TRUE: 5,
            JUMP_IF_FALSE: 6,
            LESS_THAN: 7,
            EQUALS: 8,
            HALT: 99,
        };

        this.EQUALITY = {
            EQUALS: 0,
            LESS_THAN: 1,
        };

        this.parameterMode = ComputerParameterMode.POSITION_MODE;

        /**
         * Whether the Execute loop should skip moving the pointer after running the opcode
         *
         * Some opcodes, such as JUMP_IF_TRUE set the stack pointer, and as such shouldn't have
         * the Execute function move it after the opcode finishes executing.
         */
        this.skipNext = false;

        this.options = {
            followPointer: options.followPointer ?? false,
            tickRate: options.tickRate ?? 0,
        };
    }

    /**
     * Run the computer
     *
     * Runs opcodes on the stack until either the a HALT command is
     * encountered, or an error is thrown.
     * @returns {void}
     */
    async Run() {
        while (this.Execute(this.stack.Get(ComputerParameterMode.IMMEDIATE_MODE)) === true) {
            if (this.options.tickRate) {
                // Sleep
                // eslint-disable-next-line no-await-in-loop, no-promise-executor-return, arrow-parens
                await new Promise(resolve => setTimeout(resolve, this.options.tickRate));
            }
        }
    }

    /**
     * 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;
        this.skipNext = false;

        if (this.options.followPointer) {
            this.DumpMemory(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(rawOpcode);
                break;
            }
            case this.OPCODES.JUMP_IF_TRUE: {
                this.Operation_JumpIf(rawOpcode, true);
                break;
            }
            case this.OPCODES.JUMP_IF_FALSE: {
                this.Operation_JumpIf(rawOpcode, false);
                break;
            }
            case this.OPCODES.LESS_THAN: {
                this.Operation_Equality(rawOpcode, this.EQUALITY.LESS_THAN);
                break;
            }
            case this.OPCODES.EQUALS: {
                this.Operation_Equality(rawOpcode, this.EQUALITY.EQUALS);
                break;
            }
            case this.OPCODES.HALT:
                status = false;
                break;
            default:
                throw Error(`Opcode ${opcode} not found\nMemdump: ${JSON.stringify(this.stack.Dump())}\nPointer: ${this.stack.pointer}`);
        }

        if (!this.skipNext) {
            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
     *
     * @param {number} rawOpcode The opcode in memory used to make this call
     * @returns {void}
     */
    Operation_Output(rawOpcode) {
        const currAddress = this.stack.pointer;
        const outputPositionMode = ComputerParameterMode.ParseParameterMode(rawOpcode, 1);
        const output = this.stack.Next().Get(outputPositionMode);

        console.log(`OUTPUT FROM ADDRESS ${currAddress}: ${output}`);
    }

    /**
     * Execute the Jump_If_True and Jump_If_False opcodes
     *
     * Jumps to a given address in memory if the value at next address is memory matches
     * the given true/false condition.
     *
     * @param {number} rawOpcode The opcode in memory used to make this call
     * @param {boolean} testCondition The value the memory value should be compared against
     * @returns {void}
     */
    Operation_JumpIf(rawOpcode, testCondition) {
        const paramMode = ComputerParameterMode.ParseParameterMode(rawOpcode, 1);
        const jumpAddressMode = ComputerParameterMode.ParseParameterMode(rawOpcode, 2);

        const param = this.stack.Next().Get(paramMode);
        const jumpAddress = this.stack.Next().Get(jumpAddressMode);

        const performJump = !!param == testCondition;

        if (performJump) {
            this.skipNext = true;
            this.stack.SetPointerAddress(jumpAddress);
        }
    }

    /**
     * Execute the various equality checking opcodes
     *
     * @param {number} rawOpcode The opcode in memory used to make this call
     * @param {number} testCondition The type of equality check to perform as defined in the computer's constructor
     * @returns {void}
     */
    Operation_Equality(rawOpcode, testCondition) {
        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);

        let testPassed = false;

        switch (testCondition) {
            case this.EQUALITY.EQUALS:
                testPassed = operandLeft == operandRight;
                break;
            case this.EQUALITY.LESS_THAN:
                testPassed = operandLeft < operandRight;
                break;
            default:
                break;
        }

        this.stack.Put(outputPosition, Number(testPassed));
    }

    /**
     * Outputs the computer's stack to the console
     *
     * @param {boolean} [highlightPointer=false] Should the memory address of the current pointer be highlighted
     * @returns {void}
     */
    DumpMemory(highlightPointer = false) {
        let memory = this.stack.Dump();

        if (highlightPointer) {
            memory = memory.map((instruction, idx) => (idx == this.stack.pointer ? `{${instruction}}` : instruction));
        }

        console.log(util.inspect(memory, { breakLength: Infinity, colors: true, compact: true }));
    }

    /**
     * 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);
    }
};