app.py

"""
app.py — Gradio demo for HF Spaces.
Loads the trained model (or a stub) and exposes a live prediction UI.
"""

import gradio as gr
import pandas as pd
import numpy as np
import pickle
import os
from pathlib import Path

# ── Load model (falls back to a stub if not yet trained) ──────────────────────
MODEL_PATH = Path("models/best_model.pkl")

def load_model():
    if MODEL_PATH.exists():
        with open(MODEL_PATH, "rb") as f:
            return pickle.load(f)
    return None  # stub mode

model = load_model()

CARRIER_MAP  = {"AA": 0, "DL": 1, "UA": 2, "WN": 3, "B6": 4, "AS": 5, "F9": 6, "NK": 7}
AIRPORT_STUB = {  # small lookup for demo
    "ATL": 0, "LAX": 1, "ORD": 2, "DFW": 3, "DEN": 4,
    "JFK": 5, "SFO": 6, "SEA": 7, "LAS": 8, "MIA": 9,
}

def predict_delay(
    dep_hour, dep_dayofweek, dep_month,
    carrier, origin, dest,
    crs_elapsed_time, distance,
    origin_delay_rate,
    is_weekend, is_peak_hour,
):
    carrier_enc = CARRIER_MAP.get(carrier, 0)
    origin_enc  = AIRPORT_STUB.get(origin, 0)
    dest_enc    = AIRPORT_STUB.get(dest, 1)

    features = pd.DataFrame([{
        "dep_hour":           int(dep_hour),
        "dep_dayofweek":      int(dep_dayofweek),
        "dep_month":          int(dep_month),
        "carrier_enc":        carrier_enc,
        "origin_enc":         origin_enc,
        "dest_enc":           dest_enc,
        "crs_elapsed_time":   float(crs_elapsed_time),
        "distance":           float(distance),
        "origin_delay_rate":  float(origin_delay_rate),
        "is_weekend":         int(is_weekend == "Yes"),
        "is_peak_hour":       int(is_peak_hour == "Yes"),
    }])

    if model is not None:
        prob = float(model.predict_proba(features)[0, 1])
    else:
        # Demo stub: simple heuristic
        prob = min(1.0, (
            origin_delay_rate * 0.5 +
            (0.15 if is_peak_hour == "Yes" else 0) +
            (0.1  if is_weekend  == "Yes" else 0) +
            (dep_month in [6, 7, 12]) * 0.1
        ) + np.random.normal(0, 0.05))
        prob = max(0.0, prob)

    label      = "🔴 LIKELY DELAYED" if prob >= 0.5 else "🟢 LIKELY ON TIME"
    confidence = "HIGH" if abs(prob - 0.5) > 0.25 else "MEDIUM" if abs(prob - 0.5) > 0.1 else "LOW"
    bar        = "█" * int(prob * 20) + "░" * (20 - int(prob * 20))

    return (
        f"{label}\n\n"
        f"Delay probability : {prob:.1%}\n"
        f"Confidence        : {confidence}\n"
        f"[{bar}] {prob:.1%}"
    )


# ── UI ────────────────────────────────────────────────────────────────────────
with gr.Blocks(
    title="✈️ Flight Delay Predictor",
    theme=gr.themes.Base(primary_hue="blue", neutral_hue="slate"),
) as demo:

    gr.Markdown("""
    # ✈️ Flight Delay Prediction
    Predict whether a flight will be **≥ 15 minutes late** using the trained XGBoost model.
    > Part of the [Flight Delay ML Platform](https://github.com/YOUR_USERNAME/flight-delay-platform)
    """)

    with gr.Row():
        with gr.Column():
            gr.Markdown("### ✈️ Flight Details")
            carrier  = gr.Dropdown(list(CARRIER_MAP.keys()), value="AA",  label="Airline")
            origin   = gr.Dropdown(list(AIRPORT_STUB.keys()), value="ATL", label="Origin Airport")
            dest     = gr.Dropdown(list(AIRPORT_STUB.keys()), value="LAX", label="Destination Airport")
            distance = gr.Slider(100, 5000, value=1400, step=50,  label="Distance (miles)")
            crs_elapsed_time = gr.Slider(30, 600, value=185, step=5, label="Scheduled Duration (min)")

        with gr.Column():
            gr.Markdown("### 🕐 Schedule")
            dep_hour       = gr.Slider(0, 23, value=8, step=1,  label="Departure Hour (0–23)")
            dep_dayofweek  = gr.Slider(0,  6, value=1, step=1,  label="Day of Week (0=Mon, 6=Sun)")
            dep_month      = gr.Slider(1, 12, value=3, step=1,  label="Month")
            is_weekend     = gr.Radio(["Yes", "No"], value="No",  label="Weekend Flight?")
            is_peak_hour   = gr.Radio(["Yes", "No"], value="Yes", label="Peak Hour? (7–9am / 5–8pm)")

        with gr.Column():
            gr.Markdown("### 🌦 Airport History")
            origin_delay_rate = gr.Slider(
                0.0, 1.0, value=0.22, step=0.01,
                label="Origin Airport 30-Day Delay Rate"
            )
            gr.Markdown("### 📊 Prediction")
            output = gr.Textbox(label="Result", lines=5, interactive=False)
            predict_btn = gr.Button("Predict Delay →", variant="primary")

    predict_btn.click(
        fn=predict_delay,
        inputs=[
            dep_hour, dep_dayofweek, dep_month,
            carrier, origin, dest,
            crs_elapsed_time, distance,
            origin_delay_rate, is_weekend, is_peak_hour,
        ],
        outputs=output,
    )

    gr.Examples(
        examples=[
            [8,  1, 3, "AA", "ATL", "LAX", 185, 1400, 0.22, "No",  "Yes"],
            [18, 4, 7, "UA", "ORD", "JFK", 140,  780, 0.38, "No",  "Yes"],
            [6,  6, 1, "WN", "DEN", "SFO",  95,  950, 0.12, "Yes", "No" ],
            [14, 3, 12,"DL", "ATL", "MIA",  75,  660, 0.45, "No",  "No" ],
        ],
        inputs=[
            dep_hour, dep_dayofweek, dep_month,
            carrier, origin, dest,
            crs_elapsed_time, distance,
            origin_delay_rate, is_weekend, is_peak_hour,
        ],
    )

if __name__ == "__main__":
    demo.launch()