# services/login.py
from fastapi import APIRouter, HTTPException
from pydantic import BaseModel
import sqlite3, os, hmac, hashlib
from typing import Optional

router = APIRouter()

# Resolve absolute path to db/users.db (adjust if your file is elsewhere)
BASE_DIR = os.path.dirname(os.path.abspath(__file__))        # .../services
PROJECT_ROOT = os.path.dirname(BASE_DIR)                     # project root
DB_PATH = os.path.join(PROJECT_ROOT, "db", "users.db")       # .../db/users.db

def get_conn():
    # Helpful debug: see exactly which file is used
    print(f"[login.py] Connecting to DB: {DB_PATH} | exists={os.path.exists(DB_PATH)}")
    return sqlite3.connect(DB_PATH)

def pbkdf2_hash(password: str, salt_hex: Optional[str] = None) -> tuple[str, str]:
    if not salt_hex:
        salt_hex = os.urandom(16).hex()
    salt = bytes.fromhex(salt_hex)
    dk = hashlib.pbkdf2_hmac("sha256", password.encode("utf-8"), salt, 100_000)
    return dk.hex(), salt_hex

def verify_password(password: str, stored_hash_hex: str, salt_hex: str) -> bool:
    actual_hash_hex, _ = pbkdf2_hash(password, salt_hex)
    return hmac.compare_digest(actual_hash_hex, stored_hash_hex)

class LoginRequest(BaseModel):
    username: str
    password: str

@router.post("/login")
def login(req: LoginRequest):
    username = req.username.strip()
    password = req.password

    if not username or not password:
        raise HTTPException(status_code=400, detail="Username and password required.")

    conn = get_conn()
    try:
        cur = conn.execute("SELECT password_hash, salt FROM users WHERE username = ?", (username,))
        row = cur.fetchone()
        if not row:
            raise HTTPException(status_code=401, detail="Invalid credentials.")
        stored_hash, salt = row

        if not verify_password(password, stored_hash, salt):
            raise HTTPException(status_code=401, detail="Invalid credentials.")

        return {"ok": True, "username": username}
    finally:
        conn.close()