app.py

import json
import gradio as gr

with open("model_data.json") as f:
    DATA = json.load(f)

MUNICIPALITIES = sorted(DATA["municipalities"])


def get_base(muni, area):
    lk = DATA["base_lookup"].get(muni, {})
    if not lk:
        return 2000
    keys = sorted(int(k) for k in lk)
    lo = max((k for k in keys if k <= area), default=keys[0])
    hi = min((k for k in keys if k >= area), default=keys[-1])
    if lo == hi:
        return lk[str(lo)]
    t = (area - lo) / (hi - lo)
    return lk[str(lo)] + t * (lk[str(hi)] - lk[str(lo)])


def get_rooms_delta(rooms):
    rooms = float(rooms)
    rd = DATA["rooms_deltas"]
    key = str(int(rooms)) if rooms == int(rooms) else str(rooms)
    if key in rd:
        return rd[key]
    keys = sorted(float(k) for k in rd)
    lo = max((k for k in keys if k <= rooms), default=keys[0])
    hi = min((k for k in keys if k >= rooms), default=keys[-1])
    lo_key = str(int(lo)) if lo == int(lo) else str(lo)
    hi_key = str(int(hi)) if hi == int(hi) else str(hi)
    if lo == hi:
        return rd[lo_key]
    t = (rooms - lo) / (hi - lo)
    return rd[lo_key] + t * (rd[hi_key] - rd[lo_key])


def predict(municipality, area, rooms, luxury, lake_view, furnished, temporary):
    area = float(area)
    rooms = float(rooms)

    p = get_base(municipality, area)
    base_rooms = min(6.0, max(1.0, round(area / 25) * 0.5))
    p += get_rooms_delta(rooms) - get_rooms_delta(base_rooms)

    if luxury:
        p += DATA["lux_delta"]
    if lake_view:
        p += DATA["sea_delta"]
    if furnished:
        p += DATA["fur_delta"]
    if temporary:
        p -= 200

    p = max(500, min(12000, round(p / 10) * 10))

    info = DATA["muni_info"].get(municipality, {})
    tax = info.get("tax_income", 0)
    dens = info.get("pop_dens", 0)
    tags = [t for t, f in [("Luxury", luxury), ("Lake view", lake_view),
                            ("Furnished", furnished), ("Temporary", temporary)] if f]

    result = f"""## CHF {p:,.0f} / month

**Typical error: ± CHF 446**  (model MAE, 5-fold CV)

---

### Input summary
| Feature | Value |
|---|---|
| Municipality | {municipality} |
| Living area | {area:.0f} m² |
| Rooms | {rooms} |
| m² per room | {area/rooms:.1f} |
| Listing tags | {", ".join(tags) if tags else "None"} |

### Municipal context (BFS data)
| | |
|---|---|
| Tax income | CHF {tax:,.0f} |
| Population density | {dens:,.0f} /km² |

---

### Feature importances
| Feature | Importance |
|---|---|
| Living area | 47.9% |
| Municipality | 17.6% |
| Population density | 10.9% |
| m² per room | 8.7% |
| Tax income | 4.3% |
| NLP listing tags ★ | ~1.5% |

*Gradient Boosting · R² 0.664 · trained on 2,400 real Zürich listings*
"""

    market = sorted(DATA["market"].items(), key=lambda x: -x[1])
    rows = list(market[:5])
    sel = next((x for x in market if x[0] == municipality), None)
    if sel and sel not in rows:
        rows.append(sel)
    rows.sort(key=lambda x: -x[1])

    cmp = "### Market comparison (3 rooms · 75 m²)\n\n"
    cmp += "| Municipality | CHF/month |\n|---|---|\n"
    for name, price in rows:
        marker = " ◀" if name == municipality else ""
        cmp += f"| **{name}**{marker} | {price:,} |\n"

    return result + "\n" + cmp


with gr.Blocks(title="Zürich Rent Predictor") as demo:

    gr.Markdown("# Zürich Apartment Rent Predictor")
    gr.Markdown(
        "Gradient Boosting model trained on 2,400 real Canton of Zürich listings "
        "enriched with BFS municipal data. "
        "**New feature:** NLP listing tags extracted from German descriptions "
        "(LUXURIÖS, SEESICHT, MÖBLIERT)."
    )

    with gr.Row():
        with gr.Column():
            municipality = gr.Dropdown(
                choices=MUNICIPALITIES,
                value="Zürich",
                label="Municipality"
            )
            area = gr.Slider(
                minimum=15, maximum=300, step=5, value=75,
                label="Living Area (m²)"
            )
            rooms = gr.Slider(
                minimum=1, maximum=6, step=0.5, value=3,
                label="Number of Rooms"
            )

            gr.Markdown("**Listing tags** *(new feature — extracted from listing descriptions)*")
            with gr.Row():
                luxury = gr.Checkbox(label="💎 Luxurious")
                lake_view = gr.Checkbox(label="🌊 Lake View")
            with gr.Row():
                furnished = gr.Checkbox(label="🛋️ Furnished")
                temporary = gr.Checkbox(label="📅 Temporary")

            btn = gr.Button("Predict Rent", variant="primary")

        with gr.Column():
            output = gr.Markdown(value="*Fill in the details and click Predict Rent.*")

    inputs = [municipality, area, rooms, luxury, lake_view, furnished, temporary]
    btn.click(fn=predict, inputs=inputs, outputs=output)
    for inp in inputs:
        if hasattr(inp, "change"):
            inp.change(fn=predict, inputs=inputs, outputs=output)

    gr.Markdown("---\nZHAW AI Applications · Canton of Zürich Rental Market · 2025")

if __name__ == "__main__":
    demo.launch(theme=gr.themes.Default())