backend/services/ai_engine.py

from openai import OpenAI
import os
import json

def generate_cold_email(resume_text: str, company_info: dict, tone="Confident, polite, result-oriented"):
    """
    Generates a cold email using OpenRouter API.
    """
    
    # Fetch key dynamically to ensure it's loaded
    OPENROUTER_API_KEY = os.getenv("OPENROUTER_API_KEY")

    # 1. Map Data
    candidate_profile = resume_text[:4000] # Increased limit slightly
    company_name = company_info.get('Company Name', 'Target Company')
    role = company_info.get('Role', 'Employee')
    tech_stack = company_info.get('Tech Stack', 'Industry standard technologies')
    hr_name = company_info.get('HR Name', 'Hiring Manager')

    # 2. Construct Master Prompt
    # Enhanced prompt for better personalization
    prompt = f"""
You are an expert Copywriter and AI Outreach Assistant.

OBJECTIVE:
Write a high-converting, hyper-personalized cold email to {hr_name} at {company_name} for the role of {role}.

CANDIDATE PROFILE (RESUME):
{candidate_profile}

TARGET COMPANY DETAILS:
Company: {company_name}
Role: {role}
Tech Stack: {tech_stack}

INSTRUCTIONS:
1.  **Analyze the Match**: First, silently identify the *strongest* project or skill from the candidate's resume that DIRECTLY pertains to the company's tech stack ({tech_stack}).
2.  **Hook**: Open with a strong, non-generic hook. Mention why you are interested in {company_name} or a specific achievement of theirs if known (or just general enthusiasm for their mission).
3.  **The "Why Me" (Crucial)**: You MUST include 1-2 sentences explicitly connecting a specific project/skill from the resume to the {role} requirements. "For example, in my project [Project Name], I used [Tech] to achieve [Result], which aligns with your work in [Domain]."
4.  **Tone**: Confident, professional, yet human. Avoid stiff corporate jargon.
5.  **Structure**:
    *   **Subject**: Catchy & Relevant (e.g., "{role} Application - [Candidate Name] - [Key Skill] expert")
    *   **Salutation**: Dear {hr_name},
    *   **Body**: Hook -> "Why Me" (Specific Proof) -> Value Proposition.
    *   **Call to Action**: Clear request for a brief chat or interview. Mention attached resume.
    *   **Sign-off**: Best regards, [Candidate Name]

CONSTRAINTS:
*   Keep it under 150 words.
*   NO spelling errors.
*   NO placeholders like [Insert Here] - use the data provided. If data is missing, generalize intelligently.
*   OUTPUT ONLY the email content.
"""

    return generate_email_via_ai(prompt, OPENROUTER_API_KEY)

def generate_email_via_ai(prompt: str, api_key: str) -> str:
    if not api_key:
        return "Error: OPENROUTER_API_KEY not found in environment variables. Please check your .env file."

    try:
        client = OpenAI(
            api_key=api_key,
            base_url="https://openrouter.ai/api/v1"
        )

        response = client.chat.completions.create(
            model="openai/gpt-oss-20b",
            messages=[
                {"role": "system", "content": "You are a professional AI assistant."},
                {"role": "user", "content": prompt}
            ],
            temperature=0.5,
            max_tokens=1000 # Increased slightly to ensure full email + reasoning found in some models
        )
        
        return response.choices[0].message.content
    except Exception as e:
        return f"Error connecting to OpenRouter: {str(e)}"