main.py

from fastapi import FastAPI, Query
from fastapi.middleware.cors import CORSMiddleware
import numpy as np
import json
from sentence_transformers import SentenceTransformer
import google.generativeai as genai
import os
from dotenv import load_dotenv

# ---------------------
# Startup Config
# ---------------------

print("Loading environment variables...")
load_dotenv()

print("Loading songs data...")
with open("songs.json", encoding="utf-8") as f:
    songs = json.load(f)

print("Loading embeddings...")
embeddings = np.load("song_embeddings_e5_final.npy")

print("Loading embedding model...")
model = SentenceTransformer("intfloat/multilingual-e5-large")

print("Configuring Gemini API...")
genai.configure(api_key=os.getenv("GEMINI_API_KEY"))
gemini_model = genai.GenerativeModel("gemini-2.5-flash")

print("API ready!")

# ---------------------
# FastAPI App
# ---------------------

app = FastAPI(
    title="Thirumandiram Search API",
    description="Semantic search and AI-assisted explanations for Thirumandiram verses",
    version="2.0.0"
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_methods=["*"],
    allow_headers=["*"],
)

# ---------------------
# Payiram Mapper
# ---------------------

def get_payiram(song_number: int) -> str:
    if 1 <= song_number <= 336:
        return "First Payiram"
    elif 337 <= song_number <= 548:
        return "Second Payiram"
    elif 549 <= song_number <= 883:
        return "Third Payiram"
    elif 884 <= song_number <= 1033:
        return "Fourth Payiram"
    elif 1034 <= song_number <= 1560:
        return "Fifth Payiram"
    elif 1561 <= song_number <= 1783:
        return "Sixth Payiram"
    elif 1784 <= song_number <= 1980:
        return "Seventh Payiram"
    elif 1981 <= song_number <= 2121:
        return "Eighth Payiram"
    elif 2122 <= song_number <= 3000:
        return "Ninth Payiram"
    return "Unknown Payiram"

# ---------------------
# Semantic Search
# ---------------------

def search_songs(query: str, top_k: int = 3):
    query_text = "query: " + query
    query_vec = model.encode([query_text])[0]

    sims = np.dot(embeddings, query_vec) / (
        np.linalg.norm(embeddings, axis=1) * np.linalg.norm(query_vec)
    )

    top_idx = np.argsort(-sims)[:top_k]
    results = []

    for idx in top_idx:
        song = songs[idx]
        song_number = song["song_number"]

        results.append({
            "song_number": song_number,
            "padal": song["padal"],
            "vilakam": song["vilakam"],
            "vilakam_en": song["vilakam_en"],
            "payiram": get_payiram(song_number),
            "similarity": float(sims[idx]),
        })

    return results

# ---------------------
# Gemini Scope Classifier
# ---------------------

def is_thirumandiram_scope(query: str) -> bool:
    prompt = f"""
You are a strict classifier.

Decide whether the following user query is related to:
- Thirumandiram
- Thirumoolar
- Saivism, Siddha philosophy, Yoga
- Spiritual concepts explained in Thirumandiram verses

Respond with ONLY:
YES or NO

If unsure, respond NO.

User query:
"{query}"
"""
    response = gemini_model.generate_content(prompt)
    return response.text.strip().upper() == "YES"

# ---------------------
# API Endpoints
# ---------------------

@app.get("/")
def root():
    return {
        "name": "Thirumandiram Search API",
        "version": "2.0.0",
        "endpoints": {
            "search": "/search?q=<query>&top_k=3",
            "chat_search": "/chat_search?q=<query>&top_k=3",
            "docs": "/docs",
            "health": "/health"
        }
    }

@app.get("/health")
def health():
    return {
        "status": "healthy",
        "embedding_model_loaded": model is not None,
        "gemini_configured": os.getenv("GEMINI_API_KEY") is not None
    }

# ---------------------
# Endpoint 1: Raw Semantic Search
# ---------------------

@app.get("/search")
def search(
    q: str = Query(..., description="Search query in Tamil or English"),
    top_k: int = Query(3, ge=1, le=10)
):
    return {
        "query": q,
        "results": search_songs(q, top_k)
    }

# ---------------------
# Endpoint 2: Chat Search (Gemini-Gated)
# ---------------------

@app.get("/chat_search")
def chat_search(
    q: str = Query(..., description="Search query in Tamil or English"),
    top_k: int = Query(3, ge=1, le=10)
):
    # STEP 1: Scope check
    if not is_thirumandiram_scope(q):
        return {
            "query": q,
            "out_of_scope": True,
            "message": "The query is not within the scope of Thirumandiram.",
            "summary": None,
            "results": []
        }

    # STEP 2: Semantic search
    results = search_songs(q, top_k)

    # STEP 3: Context building
    context = "\n\n".join(
        f"Song {r['song_number']} ({r['payiram']}):\n"
        f"Verse:\n{r['padal']}\n"
        f"Explanation:\n{r['vilakam_en']}"
        for r in results
    )

    prompt = f"""
You are a Thirumandiram expert assistant.
Answer ONLY using Thirumandiram philosophy.

User query:
"{q}"

Relevant verses:
{context}

Explain clearly how these verses address the query.
"""

    response = gemini_model.generate_content(prompt)

    return {
        "query": q,
        "out_of_scope": False,
        "summary": response.text,
        "results": results
    }