from flask import Flask, render_template, request, redirect, url_for, session

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

# Dummy user credentials
USER_CREDENTIALS = {"admin": "password123"}

@app.route("/", methods=["GET", "POST"])
def login():
    if request.method == "POST":
        username = request.form["username"]
        password = request.form["password"]
        
        if username in USER_CREDENTIALS and USER_CREDENTIALS[username] == password:
            session["user"] = username
            return redirect(url_for("dashboard"))
        else:
            return render_template("login.html", error="Invalid Credentials")

    return render_template("login.html", error=None)

@app.route("/dashboard")
def dashboard():
    if "user" in session:
        return f"Welcome, {session['user']}! <a href='/logout'>Logout</a>"
    return redirect(url_for("login"))

@app.route("/logout")
def logout():
    session.pop("user", None)
    return redirect(url_for("login"))

if __name__ == "__main__":
    app.run(debug=True)