const jsnes = require('jsnes')
const { createCanvas } = require('canvas');
const { writeFileSync } = require('fs');
const { requestAnimationFrame, cancelAnimationFrame } = require('request-animation-frame-polyfill')

class NESScreenShooter {
    constructor() {
        this.SCREEN_WIDTH = 256;
        this.SCREEN_HEIGHT = 240;
        this.FRAMEBUFFER_SIZE = this.SCREEN_WIDTH * this.SCREEN_HEIGHT;

        this.canvas_ctx;
        this.image;
        this.framebuffer_u8;
        this.framebuffer_u32;

        this.id = 0;

        this.nes = new jsnes.NES({
            onFrame: (framebuffer_24) => {
                for (var i = 0; i < this.FRAMEBUFFER_SIZE; i++) this.framebuffer_u32[i] = 0xFF000000 | framebuffer_24[i];
            },
        });
    }

    requestAnimationFrame(fn) {
        this.id = requestAnimationFrame(fn)

        if (this.id > 5000) {
            cancelAnimationFrame(this.id)
        }
    }

    onAnimationFrame(time) {
        if(this.id % 60 === 0) this.saveImage(`image_${this.id}`)
        this.requestAnimationFrame(this.onAnimationFrame.bind(this))

        this.image.data.set(this.framebuffer_u8);
        this.canvas_ctx.putImageData(this.image, 0, 0);
        this.nes.frame();

        if (this.id > 60) {
            this.nes.buttonDown(1, jsnes.Controller.BUTTON_START)
        }

        if (this.id > 120) {
            this.nes.buttonDown(1, jsnes.Controller.BUTTON_B)
            this.nes.buttonDown(1, jsnes.Controller.BUTTON_A)
        }
    }

    nes_init() {
        const canvas = createCanvas(this.SCREEN_WIDTH, this.SCREEN_HEIGHT);
        this.canvas_ctx = canvas.getContext("2d");
        this.image = this.canvas_ctx.getImageData(0, 0, this.SCREEN_WIDTH, this.SCREEN_HEIGHT);

        this.canvas_ctx.fillStyle = "black";
        this.canvas_ctx.fillRect(0, 0, this.SCREEN_WIDTH, this.SCREEN_HEIGHT);

        // Allocate framebuffer array.
        var buffer = new ArrayBuffer(this.image.data.length);
        this.framebuffer_u8 = new Uint8ClampedArray(buffer);
        this.framebuffer_u32 = new Uint32Array(buffer);
    }

    nes_boot(rom_data) {
        this.nes.loadROM(rom_data);

        this.requestAnimationFrame(this.onAnimationFrame.bind(this));
    }

    nes_load_data(rom_data) {
        this.nes_init();
        this.nes_boot(rom_data);
    }

    saveImage(name) {
        const buffer = this.canvas_ctx.canvas.toBuffer('image/png')
        writeFileSync(`./images/${name}.png`, buffer);
    }
}
module.exports = NESScreenShooter;