app.py

"""Main application file.
"""

from flask import Flask, render_template, request, redirect, url_for, flash
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy.engine import Engine
from sqlalchemy import event, exc

app = Flask(__name__)
app.secret_key = "secret_key"

app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///C:\\sqlite\\Databases\\python_crud_app.db"
app.config["SQLALCHEMY_TRACK_MODIFICATIONS"]= False

db = SQLAlchemy(app)


class InventoryItem(db.Model):
    """ORM for Inventory Items.
    """
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100), unique=True, nullable=False)
    quantity = db.Column(db.Integer, nullable=False)
    warehouse_id = db.Column(db.Integer, db.ForeignKey('warehouse.id'), nullable=True)


class Warehouse(db.Model):
    """ORM for Warehouses.  One-to-many with Inventory Items.
    """
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100), unique=True, nullable=False)

    inventory_items = db.relationship('InventoryItem', backref='warehouse')


@app.route('/')
def Index():
    inventory_data = InventoryItem.query.all()
    warehouse_data = Warehouse.query.all()
    return render_template("index.html", inventory_data=inventory_data, warehouse_data=warehouse_data)


@app.route('/insert_item', methods=['POST'])
def insert_item():
    if request.method == 'POST':
        name = request.form['name']
        quantity = request.form['quantity']
        warehouse_id = request.form['warehouse_id'] or None

        data = InventoryItem(name=name, quantity=quantity, warehouse_id=warehouse_id)
        try:
            db.session.add(data)
            db.session.commit()
            flash("Inserted Inventory Item Successfully", 'success')
        except exc.IntegrityError:
            flash("Failed to Insert Inventory Item", 'danger')  # generic error for DB API errors (e.g. foreign key constraint)
        finally:
            return redirect(url_for('Index')) 


@app.route('/update_item', methods=['GET', 'POST'])
def update_item():
    if request.method == 'POST':
        data = InventoryItem.query.get(request.form.get('id'))  # the hidden ID from the form
        data.name = request.form['name']
        data.quantity = request.form['quantity']
        data.warehouse_id = request.form['warehouse_id']

        try:
            db.session.commit()
            flash("Updated Inventory Item Successfully", 'success')
        except exc.IntegrityError as e:
            flash("Failed to Update Inventory Item", 'danger')  # generic error for DB API errors (e.g. foreign key constraint)
        finally:
            return redirect(url_for('Index')) 


@app.route('/delete_item/<id>/', methods=['GET', 'POST'])
def delete_item(id):
    data = InventoryItem.query.get(id)

    db.session.delete(data)
    db.session.commit()

    flash("Deleted Inventory Item Successfully", 'success')
    return redirect(url_for('Index'))


@app.route('/insert_warehouse', methods=['POST'])
def insert_warehouse():
    if request.method == 'POST':
        name = request.form['name']

        data = Warehouse(name=name)
        db.session.add(data)
        db.session.commit()

        flash("Inserted Warehouse Successfully", 'success')

        return redirect(url_for('Index'))


@app.route('/update_warehouse', methods=['GET', 'POST'])
def update_warehouse():
    if request.method == 'POST':
        data = Warehouse.query.get(request.form.get('id'))  # the hidden ID from the form
        data.name = request.form['name']

        db.session.commit()
        flash("Updated Warehouse Successfully", 'success')
        return redirect(url_for('Index'))


@app.route('/delete_warehouse/<id>/', methods=['GET', 'POST'])
def delete_warehouse(id):
    data = Warehouse.query.get(id)
    db.session.delete(data)
    db.session.commit()
    flash("Deleted Warehouse Successfully", 'success')
    return redirect(url_for('Index'))


@event.listens_for(Engine, "connect")
def set_sqlite_pragma(dbapi_connection, connection_record):
    """Change the foreign keys setting for SQLite to enforce foreign key constraints.
    
    By default, foreign keys SQLite do not affect the operation of the tables.
    """
    cursor = dbapi_connection.cursor()
    cursor.execute("PRAGMA foreign_keys=ON")
    cursor.close()


if __name__ == "__main__":
    db.drop_all()  # clear db tables for development purposes
    db.create_all()  # create database tables
    app.run(host="0.0.0.0")