Enable authentication

* gn3/auth/authentication/routes.py: Add `/login` endpoint and a function to
  validate the login credentials.
* gn3/auth/authentication/users.py: add function to fetch user details by
  email

2 files changed, 71 insertions, 0 deletions

diff --git a/gn3/auth/authentication/routes.py b/gn3/auth/authentication/routes.py
new file mode 100644
index 0000000..3b288d7
--- /dev/null
+++ b/gn3/auth/authentication/routes.py
@@ -0,0 +1,57 @@
+import requests
+
+import bcrypt
+from flask import flash, jsonify, request, session, Blueprint
+
+from gn3.auth import db
+from gn3.settings import AUTH_DB
+
+from .users import User, user_by_email
+
+auth_routes = Blueprint("auth", __name__)
+
+def valid_login(conn: db.DbConnection, user: User, password: str) -> bool:
+    """Check the validity of the provided credentials for login."""
+    with db.cursor(conn) as cursor:
+        cursor.execute(
+            ("SELECT * FROM users LEFT JOIN user_credentials "
+             "ON users.user_id=user_credentials.user_id "
+             "WHERE users.user_id=?"),
+            (str(user.user_id),))
+        row = cursor.fetchone()
+
+    if row == None:
+        return False
+
+    return bcrypt.checkpw(password.encode("utf-8"), row["password"])
+
+@auth_routes.route("/login", methods=["POST"])
+def login():
+    """Log in the user."""
+    print(request.cookies)
+    if session.get("user"):
+        flash("Already logged in!", "alert-warning")
+        print(f"ALREADY LOGGED IN: {session['user']}")
+        return redirect("/", code=302)
+
+    form = request.form
+    email = form.get("email").strip()
+    password = form.get("password").strip()
+    if email == "" or password == "":
+        flash("You must provide the email and password!", "alert-error")
+        return redirect("/", code=302)
+
+    with db.connection(AUTH_DB) as conn:
+        user = user_by_email(conn, email).maybe(False, lambda usr: usr)
+        if user and valid_login(conn, user, password):
+            session["user"] = user
+            return jsonify({
+                "user_id": user.user_id,
+                "email": user.email,
+                "name": user.name
+            }), 200
+
+    return jsonify({
+        "message": "Could not login. Invalid 'email' or 'password'.",
+        "type": "authentication-error"
+    }), 401
diff --git a/gn3/auth/authentication/users.py b/gn3/auth/authentication/users.py
index 4854d18..4adee61 100644
--- a/gn3/auth/authentication/users.py
+++ b/gn3/auth/authentication/users.py
@@ -2,8 +2,22 @@
 from uuid import UUID
 from typing import NamedTuple
 
+from pymonad.maybe import Just, Maybe, Nothing
+
+from gn3.auth import db
+
 class User(NamedTuple):
     """Class representing a user."""
     user_id: UUID
     email: str
     name: str
+
+def user_by_email(conn: db.DbConnection, email: str) -> Maybe:
+    with db.cursor(conn) as cursor:
+        cursor.execute("SELECT * FROM users WHERE email=?", (email,))
+        row = cursor.fetchone()
+
+    if row:
+        return Just(User(UUID(row["user_id"]), row["email"], row["name"]))
+
+    return Nothing