# main.py
from fastapi import FastAPI, HTTPException, status, File, UploadFile, Form, Query
from fastapi.middleware.cors import CORSMiddleware
from typing import Optional
import pandas as pd
import io
import os
from text_engine import Text_Search_Engine

app = FastAPI(title="CortexSearch", version="1.0", description="A flexible text search API with multiple FAISS index types and BM25 support.")

# Choose default index_type here: "flat", "ivf", or "hnsw"
store = Text_Search_Engine(index_type=os.getenv("INDEX_TYPE", "flat"))
try:
    store.load()
except Exception:
    pass

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


@app.get("/")
async def root():
    return {"Status": "The CortexSearch API is live!!!"}


# -------------------------
# Column preview endpoint
# -------------------------
@app.post("/list_columns")
async def list_columns(file: UploadFile = File(...)):
    """
    Upload a CSV and get available columns back.
    Useful to preview before choosing columns to index.
    """
    try:
        contents = await file.read()
        df = pd.read_csv(io.BytesIO(contents))
        return {"available_columns": list(df.columns)}
    except Exception as e:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=str(e))


# -------------------------
# Health check endpoint
# -------------------------
@app.get("/health")
async def health():
    return {"status": "ok", "rows_indexed": len(store.rows), "index_type": store.index_type}


# -------------------------
# Upload CSV (build fresh index)
# -------------------------
@app.post("/upload_csv")
async def upload_csv(file: UploadFile = File(...), columns: str = Form(...), index_type: Optional[str] = Form(None)):
    #Upload CSV and specify columns (comma-separated) to combine into searchable text.
    #Optional form field 'index_type' can be 'flat', 'ivf', or 'hnsw' to override engine default.
    try:
        contents = await file.read()
        df = pd.read_csv(io.BytesIO(contents))

        column_list = [c.strip() for c in columns.split(",") if c.strip()]
        # Validate
        for col in column_list:
            if col not in df.columns:
                return {
                    "status": "error",
                    "detail": f"Column '{col}' not found.",
                    "available_columns": list(df.columns),
                }

        rows = df.dropna(subset=column_list).to_dict(orient="records")
        for r in rows:
            r["_search_text"] = " ".join(str(r[col]) for col in column_list if r.get(col) is not None)

        texts = [r["_search_text"] for r in rows]

        if index_type:
            store.index_type = index_type

        store.encode_store(rows, texts)
        return {"status": "success", "count": len(rows), "used_columns": column_list, "index_type": store.index_type}
    except Exception as e:
        raise HTTPException(status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail=str(e))


# -------------------------
# Add CSV (append new rows)
# -------------------------
@app.post("/add_csv")
async def add_csv(file: UploadFile = File(...), columns: str = Form(...)):
    try:
        contents = await file.read()
        df = pd.read_csv(io.BytesIO(contents))

        column_list = [c.strip() for c in columns.split(",") if c.strip()]
        for col in column_list:
            if col not in df.columns:
                return {
                    "status": "error",
                    "detail": f"Column '{col}' not found.",
                    "available_columns": list(df.columns),
                }

        new_rows = df.dropna(subset=column_list).to_dict(orient="records")
        for r in new_rows:
            r["_search_text"] = " ".join(str(r[col]) for col in column_list if r.get(col) is not None)

        new_texts = [r["_search_text"] for r in new_rows]

        store.add_rows(new_rows, new_texts)

        return {"status": "success", "added_count": len(new_rows), "used_columns": column_list, "total_rows": len(store.rows)}
    except Exception as e:
        raise HTTPException(status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail=str(e))


# -------------------------
# Search endpoint
# -------------------------
@app.get("/search")
async def search(
    query: str,
    top_k: int = 3,
    mode: str = Query("semantic", enum=["semantic", "lexical", "hybrid"]),
    alpha: float = 0.5,):
    #mode: semantic | lexical | hybrid
    #alpha: weight for semantic in hybrid (0..1)
    try:
        if mode == "semantic":
            results = store.search(query, top_k=top_k)
        elif mode == "lexical":
            if store.bm25 is None:
                return {"results": []}
            tokenized_query = query.lower().split()
            scores = store.bm25.get_scores(tokenized_query)
            ranked = sorted(enumerate(scores), key=lambda x: x[1], reverse=True)[:top_k]
            results = [{**store.rows[i], "score": float(score)} for i, score in ranked]
        else:
            results = store.hybrid_search(query, top_k=top_k, alpha=alpha)

        return {"results": results}
    except Exception as e:
        raise HTTPException(status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail=str(e))


# -------------------------
# Delete all data
# -------------------------
@app.delete("/delete_data")
async def delete_data():
    try:
        store.clear_vdb()
        return {"status": "success", "message": "Vector DB cleared"}
    except Exception as e:
        raise HTTPException(status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail=str(e))