import json

def keep_only_one_source_domain(json_file_path):
    with open(json_file_path, 'r') as file:
        data = json.load(file)
    
    seen_domains = set()
    unique_data = []
    
    for item in data:
        source_domain = item.get('source_domain')
        json_obj = {}
        json_obj["url"] = item["url"]
        json_obj["source_domain"] = item["source_domain"]
        json_obj["title"] = item["title"]
        json_obj["raw_content"] = " ".join(item["raw_content"].split()[:50])
        if source_domain not in seen_domains:
            seen_domains.add(source_domain)
            unique_data.append(json_obj)
    
    with open("unique_source_documents.json", 'w') as file:
        json.dump(unique_data, file, indent=4, ensure_ascii=False)

# Usage example:
json_file_path = 'selected_documents.json'  # Replace 'data.json' with the path to your JSON file
keep_only_one_source_domain(json_file_path)