src/renderer/js/video-renderer.js

// ══════════════════════════════════════════════════════════════════════════════
// Chahua Video Builder - Video Renderer
// 100% Native Video Rendering Engine - No External Dependencies
// ══════════════════════════════════════════════════════════════════════════════
// Company: Chahua Development Co., Ltd.
// Version: 1.0.0
// License: MIT
// ══════════════════════════════════════════════════════════════════════════════

export class VideoRenderer {
  constructor(options = {}) {
    this.options = {
      width: options.width || 1920,
      height: options.height || 1080,
      fps: options.fps || 60,
      format: options.format || 'webm',
      quality: options.quality || 0.95,
      videoBitsPerSecond: options.videoBitsPerSecond || 8000000, // 8 Mbps
      ...options
    };

    this.mediaRecorder = null;
    this.recordedChunks = [];
    this.isRecording = false;
  }

  // ════════════════════════════════════════════════════════════════════════════
  // WebM/MP4 Recording using MediaRecorder API
  // ════════════════════════════════════════════════════════════════════════════

  async startRecording(element) {
    if (this.isRecording) {
      throw new Error('Recording already in progress');
    }

    try {
      // Create a canvas to capture the element
      this.canvas = document.createElement('canvas');
      this.canvas.width = this.options.width;
      this.canvas.height = this.options.height;
      this.ctx = this.canvas.getContext('2d', { 
        willReadFrequently: true,
        alpha: false 
      });

      // Store element reference
      this.element = element;

      // Start capturing frames
      this.startFrameCapture();

      // Get stream from canvas
      const stream = this.canvas.captureStream(this.options.fps);

      // Determine MIME type
      const mimeType = this.getBestMimeType();
      console.log('[VideoRenderer] Recording with:', mimeType, 'at', this.options.fps, 'fps');

      // Create MediaRecorder
      this.mediaRecorder = new MediaRecorder(stream, {
        mimeType,
        videoBitsPerSecond: this.options.videoBitsPerSecond
      });

      this.recordedChunks = [];

      // Handle data available
      this.mediaRecorder.addEventListener('dataavailable', (event) => {
        if (event.data && event.data.size > 0) {
          this.recordedChunks.push(event.data);
          console.log('[VideoRenderer] Chunk received:', event.data.size, 'bytes');
        }
      });

      // Start recording
      this.mediaRecorder.start(100); // Collect data every 100ms
      this.isRecording = true;

      console.log('[VideoRenderer] Recording started successfully');

      return {
        success: true,
        message: 'Recording started'
      };
    } catch (error) {
      console.error('[VideoRenderer] Error starting recording:', error);
      throw error;
    }
  }

  startFrameCapture() {
    const captureFrame = () => {
      if (!this.isRecording) {
        return;
      }

      try {
        // Clear canvas
        this.ctx.fillStyle = '#000000';
        this.ctx.fillRect(0, 0, this.canvas.width, this.canvas.height);

        // Get element's computed styles
        const styles = window.getComputedStyle(this.element);
        
        // Draw background
        if (styles.backgroundColor && styles.backgroundColor !== 'rgba(0, 0, 0, 0)') {
          this.ctx.fillStyle = styles.backgroundColor;
          this.ctx.fillRect(0, 0, this.canvas.width, this.canvas.height);
        }

        // Render element content using DOM to canvas conversion
        this.renderElementToCanvas(this.element, this.ctx);

      } catch (error) {
        console.error('[VideoRenderer] Frame capture error:', error);
      }

      if (this.isRecording) {
        this._frameId = requestAnimationFrame(captureFrame);
      }
    };

    captureFrame();
  }

  renderElementToCanvas(element, ctx) {
    // Get all text nodes and render them
    const walker = document.createTreeWalker(
      element,
      NodeFilter.SHOW_TEXT | NodeFilter.SHOW_ELEMENT,
      null
    );

    const texts = [];
    let node;
    
    while (node = walker.nextNode()) {
      if (node.nodeType === Node.TEXT_NODE && node.textContent.trim()) {
        const parent = node.parentElement;
        if (parent && parent.offsetParent !== null) {
          const rect = parent.getBoundingClientRect();
          const elementRect = element.getBoundingClientRect();
          const styles = window.getComputedStyle(parent);
          
          texts.push({
            text: node.textContent,
            x: rect.left - elementRect.left,
            y: rect.top - elementRect.top,
            width: rect.width,
            height: rect.height,
            font: styles.font || '16px sans-serif',
            color: styles.color || '#ffffff',
            fontSize: styles.fontSize,
            fontFamily: styles.fontFamily,
            fontWeight: styles.fontWeight,
            textAlign: styles.textAlign || 'left',
            lineHeight: parseFloat(styles.lineHeight) || parseFloat(styles.fontSize) * 1.2
          });
        }
      }
    }

    // Scale factor
    const scaleX = this.canvas.width / element.offsetWidth;
    const scaleY = this.canvas.height / element.offsetHeight;

    // Render texts
    texts.forEach(item => {
      ctx.save();
      ctx.fillStyle = item.color;
      ctx.font = `${item.fontWeight} ${parseFloat(item.fontSize) * scaleY}px ${item.fontFamily}`;
      ctx.textAlign = item.textAlign;
      ctx.textBaseline = 'top';
      
      const x = item.x * scaleX;
      const y = item.y * scaleY + (parseFloat(item.fontSize) * scaleY);
      
      ctx.fillText(item.text, x, y);
      ctx.restore();
    });
  }

  async stopRecording() {
    if (!this.isRecording || !this.mediaRecorder) {
      throw new Error('No recording in progress');
    }

    return new Promise((resolve, reject) => {
      this.mediaRecorder.addEventListener('stop', () => {
        // Stop frame capture
        if (this._frameId) {
          cancelAnimationFrame(this._frameId);
          this._frameId = null;
        }

        const blob = new Blob(this.recordedChunks, {
          type: this.mediaRecorder.mimeType
        });

        this.isRecording = false;

        console.log('[VideoRenderer] Recording stopped. Total size:', blob.size, 'bytes');
        console.log('[VideoRenderer] Total chunks:', this.recordedChunks.length);

        resolve({
          success: true,
          blob,
          size: blob.size,
          mimeType: this.mediaRecorder.mimeType,
          url: URL.createObjectURL(blob)
        });
      });

      this.mediaRecorder.addEventListener('error', (event) => {
        this.isRecording = false;
        if (this._frameId) {
          cancelAnimationFrame(this._frameId);
          this._frameId = null;
        }
        reject(new Error(`Recording error: ${event.error}`));
      });

      this.mediaRecorder.stop();
    });
  }

  // ════════════════════════════════════════════════════════════════════════════
  // GIF Rendering using Canvas
  // ════════════════════════════════════════════════════════════════════════════

  async renderGIF(element, duration, fps = 15) {
    const frames = [];
    const interval = 1000 / fps;
    const totalFrames = Math.ceil((duration / 1000) * fps);

    // Create canvas for capturing
    const canvas = document.createElement('canvas');
    canvas.width = this.options.width;
    canvas.height = this.options.height;
    const ctx = canvas.getContext('2d');

    // Capture frames
    for (let i = 0; i < totalFrames; i++) {
      await this.wait(interval);
      
      // Draw element to canvas
      await this.drawElementToCanvas(element, canvas, ctx);

      // Get image data
      const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
      frames.push({
        data: this.quantizeColors(imageData.data, 256),
        width: canvas.width,
        height: canvas.height,
        delay: Math.round(interval / 10) // Delay in 1/100s
      });
    }

    // Encode GIF
    const gifData = this.encodeGIF(frames);

    return {
      success: true,
      frames: frames.length,
      data: gifData,
      blob: new Blob([gifData], { type: 'image/gif' })
    };
  }

  // ════════════════════════════════════════════════════════════════════════════
  // Helper Functions
  // ════════════════════════════════════════════════════════════════════════════

  getBestMimeType() {
    // Chromium/Electron supports WebM very well, MP4 encoding is not directly supported
    const types = [
      'video/webm;codecs=vp9,opus',
      'video/webm;codecs=vp9',
      'video/webm;codecs=vp8,opus',
      'video/webm;codecs=vp8',
      'video/webm'
    ];

    for (const type of types) {
      if (MediaRecorder.isTypeSupported(type)) {
        console.log('[VideoRenderer] Using MIME type:', type);
        return type;
      }
    }

    console.warn('[VideoRenderer] No preferred MIME type supported, using default');
    return 'video/webm';
  }

  async captureElementStream(element) {
    const canvas = document.createElement('canvas');
    canvas.width = this.options.width;
    canvas.height = this.options.height;
    const ctx = canvas.getContext('2d');

    // Capture frames manually
    const captureFrame = async () => {
      await this.drawElementToCanvas(element, canvas, ctx);
    };

    const intervalId = setInterval(captureFrame, 1000 / this.options.fps);

    // Store interval ID for cleanup
    this._captureIntervalId = intervalId;

    return canvas.captureStream(this.options.fps);
  }

  async drawElementToCanvas(element, canvas, ctx) {
    // Use html2canvas-like approach
    const rect = element.getBoundingClientRect();
    
    // Clear canvas
    ctx.clearRect(0, 0, canvas.width, canvas.height);

    // Draw background
    ctx.fillStyle = window.getComputedStyle(element).backgroundColor || '#000';
    ctx.fillRect(0, 0, canvas.width, canvas.height);

    // For simplicity, we'll use drawImage if element is video/canvas
    // For other elements, we'd need to serialize to SVG
    if (element.tagName === 'CANVAS' || element.tagName === 'VIDEO') {
      ctx.drawImage(element, 0, 0, canvas.width, canvas.height);
    } else {
      // Serialize element to data URL and draw
      const data = await this.elementToDataURL(element);
      const img = new Image();
      await new Promise((resolve, reject) => {
        img.onload = resolve;
        img.onerror = reject;
        img.src = data;
      });
      ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
    }
  }

  async elementToDataURL(element) {
    // Create SVG foreignObject
    const rect = element.getBoundingClientRect();
    const svg = `
      <svg xmlns="http://www.w3.org/2000/svg" width="${rect.width}" height="${rect.height}">
        <foreignObject width="100%" height="100%">
          <div xmlns="http://www.w3.org/1999/xhtml">
            ${element.outerHTML}
          </div>
        </foreignObject>
      </svg>
    `;

    const blob = new Blob([svg], { type: 'image/svg+xml' });
    return URL.createObjectURL(blob);
  }

  // ════════════════════════════════════════════════════════════════════════════
  // GIF Encoding (Simplified LZW Compression)
  // ════════════════════════════════════════════════════════════════════════════

  encodeGIF(frames) {
    const { width, height } = frames[0];

    // GIF Header
    const header = this.stringToBytes('GIF89a');

    // Logical Screen Descriptor
    const lsd = new Uint8Array(7);
    lsd[0] = width & 0xFF;
    lsd[1] = (width >> 8) & 0xFF;
    lsd[2] = height & 0xFF;
    lsd[3] = (height >> 8) & 0xFF;
    lsd[4] = 0xF7; // Global Color Table Flag
    lsd[5] = 0x00; // Background Color Index
    lsd[6] = 0x00; // Pixel Aspect Ratio

    // Global Color Table (256 colors)
    const gct = this.generateColorTable(256);

    // Application Extension (for looping)
    const appExt = new Uint8Array([
      0x21, 0xFF, 0x0B,
      ...this.stringToBytes('NETSCAPE2.0'),
      0x03, 0x01, 0x00, 0x00, 0x00
    ]);

    const frameData = [];

    for (const frame of frames) {
      // Graphics Control Extension
      const gce = new Uint8Array([
        0x21, 0xF9, 0x04,
        0x04, // Disposal method
        frame.delay & 0xFF, (frame.delay >> 8) & 0xFF,
        0x00, // Transparent color index
        0x00
      ]);

      // Image Descriptor
      const imgDesc = new Uint8Array(10);
      imgDesc[0] = 0x2C; // Image separator
      imgDesc[1] = 0x00; imgDesc[2] = 0x00; // Left
      imgDesc[3] = 0x00; imgDesc[4] = 0x00; // Top
      imgDesc[5] = width & 0xFF; imgDesc[6] = (width >> 8) & 0xFF;
      imgDesc[7] = height & 0xFF; imgDesc[8] = (height >> 8) & 0xFF;
      imgDesc[9] = 0x00; // Packed fields

      // Image Data (simplified - use minimal compression)
      const imageData = this.compressImageData(frame.data);

      frameData.push(...gce, ...imgDesc, ...imageData);
    }

    // Trailer
    const trailer = new Uint8Array([0x3B]);

    // Combine all parts
    return new Uint8Array([
      ...header,
      ...lsd,
      ...gct,
      ...appExt,
      ...frameData,
      ...trailer
    ]);
  }

  generateColorTable(size) {
    const table = new Uint8Array(size * 3);
    for (let i = 0; i < size; i++) {
      table[i * 3] = i;
      table[i * 3 + 1] = i;
      table[i * 3 + 2] = i;
    }
    return table;
  }

  quantizeColors(imageData, colorCount) {
    // Simple color quantization
    const quantized = new Uint8Array(imageData.length / 4);
    for (let i = 0; i < imageData.length; i += 4) {
      const r = imageData[i];
      const g = imageData[i + 1];
      const b = imageData[i + 2];
      const gray = Math.floor(0.299 * r + 0.587 * g + 0.114 * b);
      quantized[i / 4] = Math.floor(gray * (colorCount - 1) / 255);
    }
    return quantized;
  }

  compressImageData(data) {
    // Minimal LZW compression (simplified)
    const lzwMinCodeSize = 8;
    const compressed = [lzwMinCodeSize];

    // Simple run-length encoding as fallback
    const blocks = [];
    let currentBlock = [];

    for (let i = 0; i < data.length; i++) {
      currentBlock.push(data[i]);
      if (currentBlock.length === 255) {
        blocks.push(currentBlock.length, ...currentBlock);
        currentBlock = [];
      }
    }

    if (currentBlock.length > 0) {
      blocks.push(currentBlock.length, ...currentBlock);
    }

    blocks.push(0); // Block terminator

    return new Uint8Array([...compressed, ...blocks]);
  }

  stringToBytes(str) {
    return new Uint8Array([...str].map(c => c.charCodeAt(0)));
  }

  wait(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
  }

  // ════════════════════════════════════════════════════════════════════════════
  // Cleanup
  // ════════════════════════════════════════════════════════════════════════════

  cleanup() {
    if (this._captureIntervalId) {
      clearInterval(this._captureIntervalId);
      this._captureIntervalId = null;
    }

    if (this.mediaRecorder && this.isRecording) {
      this.mediaRecorder.stop();
    }

    this.recordedChunks = [];
    this.mediaRecorder = null;
    this.isRecording = false;
  }
}

// ══════════════════════════════════════════════════════════════════════════════
// Export Format Helpers
// ══════════════════════════════════════════════════════════════════════════════

export function blobToBase64(blob) {
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.onloadend = () => resolve(reader.result);
    reader.onerror = reject;
    reader.readAsDataURL(blob);
  });
}

export function downloadBlob(blob, filename) {
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  a.download = filename;
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);
  URL.revokeObjectURL(url);
}