main.py

from typing import Dict, Optional
from fastapi import FastAPI, HTTPException, Query
from pydantic import BaseModel, EmailStr, constr

app = FastAPI(title="User Directory API")

class User(BaseModel):
    id: int
    name: constr(strip_whitespace=True, min_length=1)
    email: EmailStr
    phone: constr(strip_whitespace=True, min_length=7, max_length=20)

class PublicUser(BaseModel):
    name: str
    email: EmailStr
    phone: str


class InfoIn(BaseModel):
    name: constr(strip_whitespace=True, min_length=1)
    email: EmailStr


class InfoOut(BaseModel):
    name: str
    email: EmailStr

# In-memory "database"
USERS: Dict[int, User] = {
    1: User(id=1, name="Alice Johnson",  email="alice@example.com", phone="+1-555-0100"),
    2: User(id=2, name="Bob Singh",      email="bob@example.com",   phone="+91-98765-43210"),
    3: User(id=3, name="Charlie Kumar",  email="charlie@example.com", phone="+44 20 7946 0958"),
}

@app.get("/users/{user_id}", response_model=PublicUser)
def get_user_by_id(user_id: int):
    user = USERS.get(user_id)
    if not user:
        raise HTTPException(status_code=404, detail="User not found")
    return PublicUser(name=user.name, email=user.email, phone=user.phone)

@app.get("/info", response_model=PublicUser)
def get_info_by_email(email: EmailStr = Query(..., description="Email to lookup")):
    for user in USERS.values():
        if user.email.lower() == email.lower():
            return PublicUser(name=user.name, email=user.email, phone=user.phone)
    raise HTTPException(status_code=404, detail="User not found")


@app.post("/info", response_model=PublicUser)
def post_info(payload: InfoIn):
    """Add a new user with the given name and email.
    
    Returns HTTP 400 if the email already exists.
    """
    # Check for duplicate email
    email_lower = payload.email.lower()
    for user in USERS.values():
        if user.email.lower() == email_lower:
            raise HTTPException(
                status_code=400,
                detail="A user with this email already exists"
            )
    
    # Generate new ID (max + 1)
    new_id = max(USERS.keys(), default=0) + 1
    
    # Create new user with a default phone number
    new_user = User(
        id=new_id,
        name=payload.name,
        email=payload.email,
        phone="+1-555-0000"  # Default phone
    )
    
    # Add to our "database"
    USERS[new_id] = new_user
    
    # Return public view
    return PublicUser(
        name=new_user.name,
        email=new_user.email,
        phone=new_user.phone
    )