# -*- coding: utf-8 -*-
"""Untitled3.ipynb

Automatically generated by Colab.

Original file is located at
    https://colab.research.google.com/drive/11sS74P6WlrbXCzSh9_b8ELPTtcfdsz8s
"""

# -*- coding: utf-8 -*-
# HW3: Deterministic calculator + LLM explanation (Gradio)
# Topic: Simply supported beam with center point load (max bending stress & midspan deflection)

# -*- coding: utf-8 -*-
# HW3: Deterministic calculator + Gradio + LLM explanation
# Simply Supported Beam with Center Load

import gradio as gr
import math
import json
from transformers import pipeline

# -------------------------------
# 1. Deterministic backend function
# -------------------------------
def beam_calculator(L, P, E, I, c, sigma_allow=250.0, fy=350.0, n=1.5):
    """
    Deterministic first-principles calculation for a simply supported beam
    under a central point load.
    
    Inputs:
        L  (m): span length
        P  (kN): central load
        E  (GPa): elastic modulus
        I  (cm^4): second moment of area
        c  (cm): extreme fiber distance
        sigma_allow (MPa): allowable stress
        fy (MPa): yield strength
        n (–): safety factor
    """

    # --- Unit conversions ---
    P_N = P * 1000        # kN -> N
    E_Pa = E * 1e9        # GPa -> Pa
    I_m4 = I * 1e-8       # cm^4 -> m^4
    c_m = c / 100.0       # cm -> m

    # --- Mechanics formulas ---
    M_max = P_N * L / 4.0                      # Max bending moment (N·m)
    delta_max = (P_N * L**3) / (48 * E_Pa * I_m4)  # Max deflection (m)
    sigma_max = M_max * c_m / I_m4 / 1e6       # Max stress (MPa)

    # --- Safety checks ---
    utilization_stress = sigma_max / sigma_allow
    utilization_yield = sigma_max / (fy / n)

    # Structured record
    record = {
        "inputs": {
            "L_m": L, "P_kN": P, "E_GPa": E, "I_cm4": I, "c_cm": c,
            "sigma_allow_MPa": sigma_allow, "fy_MPa": fy, "safety_factor": n
        },
        "results": {
            "M_max_Nm": M_max,
            "delta_max_m": delta_max,
            "sigma_max_MPa": sigma_max,
            "utilization_vs_allow": utilization_stress,
            "utilization_vs_yield": utilization_yield
        }
    }
    return record

# -------------------------------
# 2. LLM Explanation
# -------------------------------
explainer = pipeline("text-generation", model="distilgpt2")

def explain_results(record):
    """Use LLM to produce a clear explanation grounded in numbers."""
    text = json.dumps(record, indent=2)
    prompt = f"""
You are an engineering assistant. A beam calculation was performed.
Here are the structured results:

{text}

Explain the results to a civil engineering student in plain English:
- Report the maximum bending moment, stress, and deflection.
- Compare stress with allowable stress and yield strength.
- State clearly if the beam is safe or unsafe.
Avoid speculation. Base explanation only on the provided numbers.
"""
    explanation = explainer(prompt, max_new_tokens=200)[0]["generated_text"]
    return explanation

# -------------------------------
# 3. Wrapper for Gradio
# -------------------------------
def run_calculation(L, P, E, I, c, sigma_allow, fy, n):
    try:
        rec = beam_calculator(L, P, E, I, c, sigma_allow, fy, n)
        explanation = explain_results(rec)
        return json.dumps(rec["results"], indent=2), explanation
    except Exception as e:
        return {"error": str(e)}, "Error during calculation."

# -------------------------------
# 4. Gradio UI
# -------------------------------
with gr.Blocks() as demo:
    gr.Markdown("# Simply Supported Beam — Center Load")
    gr.Markdown("Deterministic calculator + LLM explanation (first principles).")

    with gr.Row():
        with gr.Column():
            L = gr.Slider(0.5, 30.0, value=2.0, label="Span L (m)")
            P = gr.Slider(0.1, 500.0, value=10.0, label="Center load P (kN)")
            E = gr.Slider(10, 300, value=200, label="Elastic modulus E (GPa)")
            I = gr.Number(value=8000, label="Second moment of area I (cm^4)")
            c = gr.Number(value=15, label="Extreme fiber distance c (cm)")

            with gr.Accordion("Optional: Allowables", open=False):
                sigma_allow = gr.Number(value=250, label="Allowable stress σ_allow (MPa)")
                fy = gr.Number(value=350, label="Yield strength fy (MPa)")
                n = gr.Number(value=1.5, label="Safety factor n")

            run_btn = gr.Button("Compute")

        with gr.Column():
            results_out = gr.Textbox(label="Numerical Results")
            explain_out = gr.Textbox(label="LLM Explanation")

    run_btn.click(
        fn=run_calculation,
        inputs=[L, P, E, I, c, sigma_allow, fy, n],
        outputs=[results_out, explain_out],
    )

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