import os
import json
import re
import logging
import fitz  # PyMuPDF
import google.generativeai as genai
from dotenv import load_dotenv

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

load_dotenv()

api_key = os.getenv("GEMINI_API_KEY")
if not api_key:
    raise ValueError("GEMINI_API_KEY is missing.")

genai.configure(api_key=api_key)

def extract_text_from_stream(file_bytes: bytes) -> str:
    text = ""
    try:
        with fitz.open(stream=file_bytes, filetype="pdf") as doc:
            for page in doc:
                text += page.get_text()
    except Exception as e:
        logger.error(f"PDF Extraction Error: {e}")
        raise ValueError("Failed to extract text from PDF.")
    return text

def get_available_model_name():
    """
    Dynamically finds a working model from the user's account.
    """
    try:
        available_models = []
        for m in genai.list_models():
            if 'generateContent' in m.supported_generation_methods:
                available_models.append(m.name)
        
        if not available_models:
            logger.error("No models found.")
            return None

        # Priority list: Try to find these specific powerful models first
        preferred_order = [
            "models/gemini-1.5-flash",
            "models/gemini-1.5-pro",
            "models/gemini-pro",
            "models/gemini-1.0-pro"
        ]
        
        # 1. Check if any preferred model is in the available list
        for preferred in preferred_order:
            if preferred in available_models:
                logger.info(f"Selected Preferred Model: {preferred}")
                return preferred

        # 2. If none of the preferred ones exist, take the first available one
        fallback = available_models[0]
        logger.warning(f"Preferred models missing. Falling back to: {fallback}")
        return fallback

    except Exception as e:
        logger.error(f"Error listing models: {e}")
        return None

def analyze_resume(resume_text: str, job_description: str = None) -> dict:
    
    # 1. FIND A WORKING MODEL (The Critical Fix)
    model_name = get_available_model_name()
    if not model_name:
        return {"error": "CRITICAL: No available AI models found for this API Key."}

    # 2. CONSTRUCT PROMPT
    if job_description:
        prompt = f"""
        Act as a strict AI Recruiter. Compare the Resume against the Job Description.
        
        RETURN JSON ONLY with this exact structure:
        {{
            "candidate": {{
                "name": "string",
                "email": "string",
                "phone": "string",
                "skills": ["list", "of", "candidate", "skills"],
                "experience_years": "string or null"
            }},
            "match_analysis": {{
                "score": integer_0_to_100,
                "reasoning": "brief summary of why this score was given",
                "matching_skills": ["skills in both resume and JD"],
                "missing_skills": ["skills in JD but NOT in resume"],
                "verdict": "Interview" | "Shortlist" | "Reject"
            }}
        }}

        JOB DESCRIPTION:
        {job_description[:5000]}

        RESUME TEXT:
        {resume_text[:10000]}
        """
    else:
        prompt = f"""
        Extract structured data from the resume. Return JSON:
        {{
            "candidate": {{
                "name": "string",
                "email": "string",
                "phone": "string",
                "skills": ["list", "of", "skills"],
                "summary": "string"
            }}
        }}
        
        RESUME TEXT:
        {resume_text[:10000]}
        """

    # 3. GENERATE CONTENT
    try:
        model = genai.GenerativeModel(model_name)
        response = model.generate_content(prompt)
        
        raw = response.text.strip()
        clean_json = re.sub(r'```json\s*|```', '', raw, flags=re.MULTILINE).strip()
        return json.loads(clean_json)
        
    except Exception as e:
        logger.error(f"Analysis failed with model {model_name}: {e}")
        return {"error": f"Analysis failed using {model_name}. Detail: {str(e)}"}