I assume you're asking for LangChain code to create content for Facebook using HeyGen's capabilities. HeyGen is a video platform that leverages generative AI, often used for creating video content, while LangChain is a framework for building applications with language models. Since HeyGen's API focuses on video generation and LangChain excels at text generation and orchestration, I’ll provide an example that combines LangChain to generate a script and integrates with HeyGen’s API to create a video for posting on Facebook.

Note: HeyGen’s API requires authentication (e.g., an API key) and specific endpoints, which I’ll reference generically here since exact implementation details depend on your HeyGen account and API access. You’ll need to replace placeholders like `YOUR_HEYGEN_API_KEY` with your actual credentials.

Below is an example of how you might use LangChain to generate a script and then use HeyGen’s API to create a video:

```python

import requests

from langchain.prompts import PromptTemplate

from langchain.chains import LLMChain

from langchain.llms import OpenAI # Or another LLM provider

# Step 1: Set up LangChain to generate a video script

llm = OpenAI(api_key="YOUR_OPENAI_API_KEY", temperature=0.7)

# Define a prompt template for generating a short Facebook-friendly video script

prompt_template = PromptTemplate(

input_variables=["topic"],

template="Write a short, engaging script (under 100 words) for a Facebook video about {topic}. Keep it casual, friendly, and include a call-to-action."

)

# Create a chain to generate the script

script_chain = LLMChain(llm=llm, prompt=prompt_template)

# Generate the script

topic = "a new eco-friendly product launch"

script = script_chain.run(topic)

print("Generated Script:")

print(script)

# Step 2: Use HeyGen API to create a video from the script

HEYGEN_API_KEY = "YOUR_HEYGEN_API_KEY"

HEYGEN_API_URL = "https://api.heygen.com/v1/video/generate" # Example endpoint, check HeyGen docs

# Define the payload for HeyGen API (adjust based on actual API requirements)

payload = {

"script": script,

"avatar": "default-avatar-id", # Replace with a valid HeyGen avatar ID

"voice": "default-voice-id", # Replace with a valid voice ID

"background": "simple", # Optional customization

"format": "mp4" # Suitable for Facebook

}

headers = {

"Authorization": f"Bearer {HEYGEN_API_KEY}",

"Content-Type": "application/json"

}

# Send request to HeyGen API

response = requests.post(HEYGEN_API_URL, json=payload, headers=headers)

if response.status_code == 200:

video_data = response.json()

video_url = video_data.get("video_url") # Adjust based on actual response structure

print(f"Video generated successfully! Download it here: {video_url}")

else:

print(f"Error generating video: {response.status_code} - {response.text}")

# Step 3: Optionally, post to Facebook (requires Facebook Graph API setup)

# This is a placeholder; you'll need to set up Facebook Graph API access separately

FACEBOOK_ACCESS_TOKEN = "YOUR_FB_ACCESS_TOKEN"

FACEBOOK_PAGE_ID = "YOUR_PAGE_ID"

FB_API_URL = f"https://graph.facebook.com/{FACEBOOK_PAGE_ID}/videos"

fb_payload = {

"access_token": FACEBOOK_ACCESS_TOKEN,

"file_url": video_url,

"description": f"Check out our new eco-friendly product! {topic}"

}

fb_response = requests.post(FB_API_URL, data=fb_payload)

if fb_response.status_code == 200:

print("Video posted to Facebook successfully!")

else:

print(f"Error posting to Facebook: {fb_response.status_code} - {fb_response.text}")

```

### Explanation:

1. **Script Generation with LangChain**:

- Uses `OpenAI` (or substitute with another LLM) to generate a concise, engaging script tailored for a Facebook audience.

- The `PromptTemplate` ensures the script fits the tone and length suitable for a short video.

2. **HeyGen Video Creation**:

- Sends the script to HeyGen’s API to generate a video with an avatar and voice.

- You’ll need to replace placeholder values (e.g., `avatar`, `voice`) with valid options from HeyGen’s documentation.

- The API call assumes a simple endpoint structure; refer to HeyGen’s official API docs for exact details (e.g., `https://docs.heygen.com/reference`).

3. **Posting to Facebook**:

- A basic example of using the Facebook Graph API to upload the video.

- Requires a Facebook Page, an access token, and proper API permissions (e.g., `publish_video`).

### Prerequisites:

- **API Keys**: Obtain keys for OpenAI (or your LLM), HeyGen, and Facebook Graph API.

- **Dependencies**: Install required packages:

```bash

pip install langchain openai requests

```

- **HeyGen API Access**: Sign up for HeyGen and get your API key and documentation for endpoints.

### Notes:

- This is a simplified workflow. HeyGen’s API might require additional steps (e.g., polling for video status if generation is asynchronous).

- For production, add error handling, retries, and validation.

- If you only need the script or video without posting to Facebook, skip the last step.

Let me know if you need help refining this further or integrating specific HeyGen features!