main.py

from fastapi import Depends,FastAPI
from fastapi.middleware.cors import CORSMiddleware
from models import Product
from database import session, engine
import database_models
from sqlalchemy.orm import Session

app=FastAPI()
#To resolve CORS for connection with backend and frontend
app.add_middleware(
    CORSMiddleware,
    #add the address of frontend
    allow_origins=["http://localhost:3000"],
    #allow all the methods in the app to access
    allow_methods=["*"]
)

#sqlalchemy to access the database and add the data to 
#database 
database_models.Base.metadata.create_all(bind=engine)
#we are trying to access the homepage 
@app.get("/")
def greet():
    return "Welcome to My app"
products=[
    #passing the value to models class product
    Product(id=1,name="Phone",description="budget phone",price=699.99,quantity=10),
    Product(id=2,name="Laptop",description="budget laptop",price=999.99,quantity=30),
    Product(id=3,name="Pen",description="A blue ink pen",price=1.99,quantity=100),
    Product(id=4,name="Table",description="A wooden table",price=199.99,quantity=20),
]
#getting globally the session to re use
#everytime anyone wants to use db then they have to inject this into 
#object
def get_db():

    db=session()
    #close the connection
    try:
        yield db
    finally:
        db.close()

#function to store data in the tables created
def init_db():
    db=session()
    #check if table is empty then execute else don't
    count=db.query(database_models.Product).count
    if count==0:
        for product in products:
            #we get product from db_model of sql alchemy then 
            #convert our product into sqlalchemy product were we convert pydantic using model dump then unpack model dump
            #for key value pair
            db.add(database_models.Product(**product.model_dump()))
        db.commit()
init_db()
#getting all the product
@app.get("/products")
#Dependencies Injection
def get_all_products(db:Session=Depends(get_db)):
    #database connection with injection from fastapi
    db_products=db.query(database_models.Product).all()
    return db_products
    

    return products


#get product through the ID
@app.get("/products/{id}")
def get_product_by_id(id:int,db:Session=Depends(get_db)):
    #find product in database model were first product whose id matches 
    db_product= db.query(database_models.Product).filter(database_models.Product.id==id).first()
        #if there is db-product then return db_product 
    if db_product:
        return db_product
        #else
    return "product not found"
#posting the product to the products list
@app.post("/products")
def add_product(product:Product,db:Session=Depends(get_db)):
    #adding data to the model were user enter the value
    db.add(database_models.Product(**product.model_dump()))
    #commit the changes to database
    db.commit()
    return product

#update product
@app.put("/products/{id}")
def update_product(id: int,product:Product,db:Session=Depends(get_db)):
    #check for product
    db_product=db.query(database_models.Product).filter(database_models.Product.id==id).first()
    #if product exist then
    if db_product:
        #change the properties of the product
        db_product.name=product.name
        db_product.price=product.price
        db_product.description=product.description
        db_product.quantity=product.quantity
        #commit the changes
        db.commit()
        return "Product Updated"

    else:
        return "No product found"

#delete product
@app.delete("/products")
def delete_product(id:int,db:Session=Depends(get_db)):
    #get the product
    db_product=db.query(database_models.Product).filter(database_models.Product.id==id).first()
    if db_product:
        db.delete(db_product)
        db.commit()
        return "Product Deleted"
    else:
        return "No Product Found"