How to Build a Ai Video Generator

// Video generation using Runway Gen-3 via API
  async function generateVideo(prompt, options = {}) {
  const { duration = 4, aspectRatio = '16:9', imageRef = null } = options;

  const payload = {
    text_prompt: prompt,
    duration: duration,
    aspect_ratio: aspectRatio,
    ...(imageRef && { init_image: imageRef })
  };

  const response = await fetch('https://api.dev.runwayml.com/v1/generations', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${process.env.RUNWAY_API_KEY}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(payload)
  });

  const { id } = await response.json();
  // Poll for completion (video generation takes 30-120 seconds)
  return pollForResult(id);
  }

  async function pollForResult(generationId) {
  while (true) {
    const res = await fetch(`https://api.dev.runwayml.com/v1/generations/${generationId}`);
    const data = await res.json();
    if (data.status === 'SUCCEEDED') return data.output_url;
    if (data.status === 'FAILED') throw new Error(data.error);
    await new Promise(r => setTimeout(r, 5000));
  }
  }