simulator_module.py

import pandas as pd

def run_simulator(
    site_name: str,
    visitor_count: int,
    current_risk: float,
    improvement_pct: float  # 0-100, do user kéo slider
) -> tuple[str, pd.DataFrame]:

    improvement = improvement_pct / 100
    new_risk = round(max(0.0, current_risk * (1 - improvement)), 3)

    # ── Tính toán TRƯỚC ───────────────────────────────────
    waste_total    = visitor_count * 0.5
    unmanaged_now  = waste_total * current_risk
    water_now      = round(unmanaged_now * 0.15, 2)
    co2_now        = round(unmanaged_now * 2.5, 2) if current_risk > 0.5 else 0.0
    cost_now       = round(unmanaged_now * 1.5, 1)

    # ── Tính toán SAU ─────────────────────────────────────
    unmanaged_new  = waste_total * new_risk
    water_new      = round(unmanaged_new * 0.15, 2)
    co2_new        = round(unmanaged_new * 2.5, 2) if new_risk > 0.5 else 0.0
    cost_new       = round(unmanaged_new * 1.5, 1)
    good_cost      = round(waste_total * 0.4, 1)

    daily_save     = round(max(cost_now - cost_new, 0), 1)
    annual_save    = int(daily_save * 365)

    # ── Trust grade ───────────────────────────────────────
    def grade(r):
        if r < 0.2:  return "A 🌟"
        if r < 0.4:  return "B ✅"
        if r < 0.6:  return "C ⚠️"
        if r < 0.8:  return "D 🚩"
        return "F 🚨"

    # ── DataFrame cho bar chart ───────────────────────────
    chart_df = pd.DataFrame({
        "Scenario":  ["Current", "After Improvement", "Current", "After Improvement", "Current", "After Improvement"],
        "Metric":    ["Unmanaged Waste (kg/day)", "Unmanaged Waste (kg/day)",
                      "CO2 Emission (kg/day)",    "CO2 Emission (kg/day)",
                      "Daily Cost (USD)",          "Daily Cost (USD)"],
        "Value":     [unmanaged_now, unmanaged_new, co2_now, co2_new, cost_now, cost_new]
    })

    # ── Text output ───────────────────────────────────────
    output = f"""## 🔄 Before / After Simulator — {site_name}

**Improvement Applied: {improvement_pct:.0f}%**
| | Before | After | Change |
|--|--------|-------|--------|
| Risk Score | {current_risk:.2f} | {new_risk:.2f} | {"↓ " + str(round((current_risk - new_risk)*100)) + "%" if new_risk < current_risk else "—"} |
| Trust Grade | {grade(current_risk)} | {grade(new_risk)} | {"⬆️ Improved" if new_risk < current_risk else "—"} |
| Unmanaged Waste | {unmanaged_now:.1f} kg/day | {unmanaged_new:.1f} kg/day | ↓ {round(unmanaged_now - unmanaged_new, 1)} kg |
| Water Pollution | {water_now} kg BOD | {water_new} kg BOD | ↓ {round(water_now - water_new, 2)} kg |
| CO₂ Emission | {co2_now} kg/day | {co2_new} kg/day | ↓ {round(co2_now - co2_new, 1)} kg |
| Daily Cost | ${cost_now} | ${cost_new} | ↓ ${daily_save} |
| **Annual Savings** | — | — | **${annual_save:,}/year** |

---

### 💡 What {improvement_pct:.0f}% improvement means in practice:
- Reduce unmanaged waste by **{round(unmanaged_now - unmanaged_new, 1)} kg every day**
- Save **${annual_save:,} USD per year**
- Protect **{int((water_now - water_new) * 1000 * 365):,} liters** of clean water annually
- Avoid **{round((co2_now - co2_new) * 365, 1)} kg CO₂** per year

> 📊 See bar chart below for visual comparison
"""
    return output, chart_df