import { Component, ElementRef, ViewChild, HostListener, Input, Output, EventEmitter, OnInit,
  OnDestroy, OnChanges, ChangeDetectionStrategy, NgZone, AfterViewInit } from '@angular/core';
import { StateService } from 'src/app/services/state.service';
import { MempoolBlockWithTransactions, MempoolBlockDelta, TransactionStripped } from 'src/app/interfaces/websocket.interface';
import { Subscription, BehaviorSubject } from 'rxjs';
import { WebsocketService } from 'src/app/services/websocket.service';
import { FastVertexArray } from './fast-vertex-array';
import BlockScene from './block-scene';
import TxSprite from './tx-sprite';
import TxView from './tx-view';

@Component({
  selector: 'app-mempool-block-overview',
  templateUrl: './mempool-block-overview.component.html',
  styleUrls: ['./mempool-block-overview.component.scss'],
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class MempoolBlockOverviewComponent implements OnInit, OnDestroy, OnChanges, AfterViewInit {
  @Input() index: number;
  @Output() txPreviewEvent = new EventEmitter<TransactionStripped | void>();

  @ViewChild('blockCanvas')
  canvas: ElementRef<HTMLCanvasElement>;

  gl: WebGLRenderingContext;
  animationFrameRequest: number;
  displayWidth: number;
  displayHeight: number;
  shaderProgram: WebGLProgram;
  vertexArray: FastVertexArray;
  running: boolean;
  scene: BlockScene;
  hoverTx: TxView | void;
  selectedTx: TxView | void;
  lastBlockHeight: number;
  blockIndex: number;
  isLoading$ = new BehaviorSubject<boolean>(true);

  blockSub: Subscription;
  deltaSub: Subscription;

  constructor(
    public stateService: StateService,
    private websocketService: WebsocketService,
    readonly ngZone: NgZone,
  ) {
    this.vertexArray = new FastVertexArray(512, TxSprite.dataSize);
  }

  ngOnInit(): void {
    this.blockSub = this.stateService.mempoolBlockTransactions$.subscribe((transactionsStripped) => {
      this.replaceBlock(transactionsStripped);
    });
    this.deltaSub = this.stateService.mempoolBlockDelta$.subscribe((delta) => {
      this.updateBlock(delta);
    });
  }

  ngAfterViewInit(): void {
    this.canvas.nativeElement.addEventListener('webglcontextlost', this.handleContextLost, false);
    this.canvas.nativeElement.addEventListener('webglcontextrestored', this.handleContextRestored, false);
    this.gl = this.canvas.nativeElement.getContext('webgl');
    this.initCanvas();

    this.resizeCanvas();
  }

  ngOnChanges(changes): void {
    if (changes.index) {
      this.clearBlock(changes.index.currentValue > changes.index.previousValue ? 'right' : 'left');
      this.isLoading$.next(true);
      this.websocketService.startTrackMempoolBlock(changes.index.currentValue);
    }
  }

  ngOnDestroy(): void {
    this.blockSub.unsubscribe();
    this.deltaSub.unsubscribe();
    this.websocketService.stopTrackMempoolBlock();
  }

  clearBlock(direction): void {
    if (this.scene) {
      this.scene.exit(direction);
    }
    this.hoverTx = null;
    this.selectedTx = null;
    this.txPreviewEvent.emit(null);
  }

  replaceBlock(transactionsStripped: TransactionStripped[]): void {
    if (!this.scene) {
      this.scene = new BlockScene({ width: this.displayWidth, height: this.displayHeight, resolution: 75,
        blockLimit: this.stateService.blockVSize, vertexArray: this.vertexArray });
    }
    const blockMined = (this.stateService.latestBlockHeight > this.lastBlockHeight);
    if (this.blockIndex !== this.index) {
      const direction = (this.blockIndex == null || this.index < this.blockIndex) ? 'left' : 'right';
      this.scene.enter(transactionsStripped, direction);
    } else {
      this.scene.replace(transactionsStripped, blockMined ? 'right' : 'left');
    }

    this.lastBlockHeight = this.stateService.latestBlockHeight;
    this.blockIndex = this.index;
    this.isLoading$.next(false);
  }

  updateBlock(delta: MempoolBlockDelta): void {
    if (!this.scene) {
      this.scene = new BlockScene({ width: this.displayWidth, height: this.displayHeight, resolution: 75,
        blockLimit: this.stateService.blockVSize, vertexArray: this.vertexArray });
    }
    const blockMined = (this.stateService.latestBlockHeight > this.lastBlockHeight);

    if (this.blockIndex !== this.index) {
      const direction = (this.blockIndex == null || this.index < this.blockIndex) ? 'left' : 'right';
      this.scene.exit(direction);
      this.scene = new BlockScene({ width: this.displayWidth, height: this.displayHeight, resolution: 75,
        blockLimit: this.stateService.blockVSize, vertexArray: this.vertexArray });
      this.scene.enter(delta.added, direction);
    } else {
      this.scene.update(delta.added, delta.removed, blockMined ? 'right' : 'left', blockMined);
    }

    this.lastBlockHeight = this.stateService.latestBlockHeight;
    this.blockIndex = this.index;
    this.isLoading$.next(false);
  }

  initCanvas(): void {
    this.gl.clearColor(0.0, 0.0, 0.0, 0.0);
    this.gl.clear(this.gl.COLOR_BUFFER_BIT);

    const shaderSet = [
      {
        type: this.gl.VERTEX_SHADER,
        src: vertShaderSrc
      },
      {
        type: this.gl.FRAGMENT_SHADER,
        src: fragShaderSrc
      }
    ];

    this.shaderProgram = this.buildShaderProgram(shaderSet);

    this.gl.useProgram(this.shaderProgram);

    // Set up alpha blending
    this.gl.enable(this.gl.BLEND);
    this.gl.blendFunc(this.gl.ONE, this.gl.ONE_MINUS_SRC_ALPHA);

    const glBuffer = this.gl.createBuffer();
    this.gl.bindBuffer(this.gl.ARRAY_BUFFER, glBuffer);

    /* SET UP SHADER ATTRIBUTES */
    Object.keys(attribs).forEach((key, i) => {
      attribs[key].pointer = this.gl.getAttribLocation(this.shaderProgram, key);
      this.gl.enableVertexAttribArray(attribs[key].pointer);
    });

    this.start();
  }

  handleContextLost(event): void {
    event.preventDefault();
    cancelAnimationFrame(this.animationFrameRequest);
    this.animationFrameRequest = null;
    this.running = false;
  }

  handleContextRestored(event): void {
    this.initCanvas();
  }

  @HostListener('window:resize', ['$event'])
  resizeCanvas(): void {
    this.displayWidth = this.canvas.nativeElement.parentElement.clientWidth;
    this.displayHeight = this.canvas.nativeElement.parentElement.clientHeight;
    this.canvas.nativeElement.width = this.displayWidth;
    this.canvas.nativeElement.height = this.displayHeight;
    if (this.gl) {
      this.gl.viewport(0, 0, this.canvas.nativeElement.width, this.canvas.nativeElement.height);
    }
    if (this.scene) {
      this.scene.resize({ width: this.displayWidth, height: this.displayHeight });
    }
  }

  compileShader(src, type): WebGLShader {
    const shader = this.gl.createShader(type);

    this.gl.shaderSource(shader, src);
    this.gl.compileShader(shader);

    if (!this.gl.getShaderParameter(shader, this.gl.COMPILE_STATUS)) {
      console.log(`Error compiling ${type === this.gl.VERTEX_SHADER ? 'vertex' : 'fragment'} shader:`);
      console.log(this.gl.getShaderInfoLog(shader));
    }
    return shader;
  }

  buildShaderProgram(shaderInfo): WebGLProgram {
    const program = this.gl.createProgram();

    shaderInfo.forEach((desc) => {
      const shader = this.compileShader(desc.src, desc.type);
      if (shader) {
        this.gl.attachShader(program, shader);
      }
    });

    this.gl.linkProgram(program);

    if (!this.gl.getProgramParameter(program, this.gl.LINK_STATUS)) {
      console.log('Error linking shader program:');
      console.log(this.gl.getProgramInfoLog(program));
    }

    return program;
  }

  start(): void {
    this.running = true;
    this.ngZone.runOutsideAngular(() => this.run());
  }

  run(now?: DOMHighResTimeStamp): void {
    if (!now) {
      now = performance.now();
    }

    /* SET UP SHADER UNIFORMS */
    // screen dimensions
    this.gl.uniform2f(this.gl.getUniformLocation(this.shaderProgram, 'screenSize'), this.displayWidth, this.displayHeight);
    // frame timestamp
    this.gl.uniform1f(this.gl.getUniformLocation(this.shaderProgram, 'now'), now);

    /* SET UP SHADER ATTRIBUTES */
    Object.keys(attribs).forEach((key, i) => {
      this.gl.vertexAttribPointer(attribs[key].pointer,
      attribs[key].count,  // number of primitives in this attribute
      this.gl[attribs[key].type],  // type of primitive in this attribute (e.g. gl.FLOAT)
      false, // never normalised
      stride,   // distance between values of the same attribute
      attribs[key].offset);  // offset of the first value
    });

    const pointArray = this.vertexArray.getVertexData();

    if (pointArray.length) {
      this.gl.bufferData(this.gl.ARRAY_BUFFER, pointArray, this.gl.DYNAMIC_DRAW);
      this.gl.drawArrays(this.gl.TRIANGLES, 0, pointArray.length / TxSprite.vertexSize);
    }

    /* LOOP */
    if (this.running) {
      if (this.animationFrameRequest) {
        cancelAnimationFrame(this.animationFrameRequest);
        this.animationFrameRequest = null;
      }
      this.animationFrameRequest = requestAnimationFrame(() => this.run());
    }
  }

  @HostListener('click', ['$event'])
  onClick(event) {
    this.setPreviewTx(event.offsetX, event.offsetY, true);
  }

  @HostListener('pointermove', ['$event'])
  onPointerMove(event) {
    this.setPreviewTx(event.offsetX, event.offsetY, false);
  }

  @HostListener('pointerleave', ['$event'])
  onPointerLeave(event) {
    this.setPreviewTx(-1, -1, false);
  }

  setPreviewTx(x: number, y: number, clicked: boolean = false) {
    if (this.scene && (!this.selectedTx || clicked)) {
      const selected = this.scene.getTxAt({ x, y });
      const currentPreview = this.selectedTx || this.hoverTx;

      if (selected !== currentPreview) {
        if (currentPreview) {
          currentPreview.setHover(false);
        }
        if (selected) {
          selected.setHover(true);
          this.txPreviewEvent.emit({
            txid: selected.txid,
            fee: selected.fee,
            vsize: selected.vsize,
            value: selected.value
          });
          if (clicked) {
            this.selectedTx = selected;
          } else {
            this.hoverTx = selected;
          }
        } else {
          if (clicked) {
            this.selectedTx = null;
          }
          this.hoverTx = null;
          this.txPreviewEvent.emit(null);
        }
      } else if (clicked) {
        if (selected === this.selectedTx) {
          this.hoverTx = this.selectedTx;
          this.selectedTx = null;
        } else {
          this.selectedTx = selected;
        }
      }
    }
  }
}

// WebGL shader attributes
const attribs = {
  offset: { type: 'FLOAT', count: 2, pointer: null, offset: 0 },
  posX: { type: 'FLOAT', count: 4, pointer: null, offset: 0 },
  posY: { type: 'FLOAT', count: 4, pointer: null, offset: 0 },
  posR: { type: 'FLOAT', count: 4, pointer: null, offset: 0 },
  colR: { type: 'FLOAT', count: 4, pointer: null, offset: 0 },
  colG: { type: 'FLOAT', count: 4, pointer: null, offset: 0 },
  colB: { type: 'FLOAT', count: 4, pointer: null, offset: 0 },
  colA: { type: 'FLOAT', count: 4, pointer: null, offset: 0 }
};
// Calculate the number of bytes per vertex based on specified attributes
const stride = Object.values(attribs).reduce((total, attrib) => {
  return total + (attrib.count * 4);
}, 0);
// Calculate vertex attribute offsets
for (let i = 0, offset = 0; i < Object.keys(attribs).length; i++) {
  const attrib = Object.values(attribs)[i];
  attrib.offset = offset;
  offset += (attrib.count * 4);
}

const vertShaderSrc = `
varying lowp vec4 vColor;

// each attribute contains [x: startValue, y: endValue, z: startTime, w: rate]
// shader interpolates between start and end values at the given rate, from the given time

attribute vec2 offset;
attribute vec4 posX;
attribute vec4 posY;
attribute vec4 posR;
attribute vec4 colR;
attribute vec4 colG;
attribute vec4 colB;
attribute vec4 colA;

uniform vec2 screenSize;
uniform float now;

float smootherstep(float x) {
  x = clamp(x, 0.0, 1.0);
  float ix = 1.0 - x;
  x = x * x;
  return x / (x + ix * ix);
}

float interpolateAttribute(vec4 attr) {
  float d = (now - attr.z) * attr.w;
  float delta = smootherstep(d);
  return mix(attr.x, attr.y, delta);
}

void main() {
  vec4 screenTransform = vec4(2.0 / screenSize.x, 2.0 / screenSize.y, -1.0, -1.0);
  // vec4 screenTransform = vec4(1.0 / screenSize.x, 1.0 / screenSize.y, -0.5, -0.5);

  float radius = interpolateAttribute(posR);
  vec2 position = vec2(interpolateAttribute(posX), interpolateAttribute(posY)) + (radius * offset);

  gl_Position = vec4(position * screenTransform.xy + screenTransform.zw, 1.0, 1.0);

  float red = interpolateAttribute(colR);
  float green = interpolateAttribute(colG);
  float blue = interpolateAttribute(colB);
  float alpha = interpolateAttribute(colA);

  vColor = vec4(red, green, blue, alpha);
}
`;

const fragShaderSrc = `
varying lowp vec4 vColor;

void main() {
  gl_FragColor = vColor;
  // premultiply alpha
  gl_FragColor.rgb *= gl_FragColor.a;
}
`;