Problem 7.33 - Graphical methods for shear force & bending moment diagrams

[Problem adapted from © Kurt Gramoll CC BY NC-SA 4.0]

#| standalone: true
#| viewerHeight: 600
#| components: [viewer]

from shiny import App, render, ui, reactive
import random
import asyncio
import io
import math
import string
from datetime import datetime
from pathlib import Path

def generate_random_letters(length):
    # Generate a random string of letters of specified length
    return "".join(random.choice(string.ascii_lowercase) for _ in range(length))

problem_ID = "340"
w0 = reactive.Value("__")
a = reactive.Value("__")
b = reactive.Value("__")
c = reactive.Value("__")
attempts = ["Timestamp,Attempt,Answer1,Answer2,Feedback\n"]

app_ui = ui.page_fluid(
    ui.markdown("**Please enter your ID number from your instructor and click to generate your problem**"),
    ui.input_text("ID", "", placeholder="Enter ID Number Here"),
    ui.input_action_button("generate_problem", "Generate Problem", class_="btn-primary"),
    ui.markdown("**Problem Statement**"),
    ui.output_ui("ui_problem_statement"),
    ui.input_text("answer1", "Your Answer 1 in units of kip", placeholder="Please enter your answer 1"),
    ui.input_text("answer2", "Your Answer 2 in units of kip-in", placeholder="Please enter your answer 2"),
    ui.input_action_button("submit", "Submit Answers", class_="btn-primary"),
    ui.download_button("download", "Download File to Submit", class_="btn-success"),
)

def server(input, output, session):
    # Initialize a counter for attempts
    attempt_counter = reactive.Value(0)

    @output
    @render.ui
    def ui_problem_statement():
        return [
            ui.markdown(
                f"The lift of an aircraft can be modeled as a beam with distributed loads as shown, where w<sub>0</sub> = {w0()} lb/in. The aircraft weight is modeled as a uniform distributed load about the center of magnitude w. Assuming the lift distribution is symmetric around the center and that the plane is in static equilibrium, plot the shear force and bending moment diagrams for the loading shown. What is the maximum absolute shear force and maximum absolute bending moment? Assume lengths a = {a()} in., b = {b()} in., and c = {c()} in."
            )
        ]

    @reactive.Effect
    @reactive.event(input.generate_problem)
    def randomize_vars():
        random.seed(input.ID())
        w0.set(random.randrange(50,100,1))
        a.set(random.randrange(80,120,1))
        b.set(a()+random.randrange(50,100,1))
        c.set(b()+random.randrange(10,20,1))
        
    @reactive.Effect
    @reactive.event(input.submit)
    def _():
        attempt_counter.set(
            attempt_counter() + 1
        )  # Increment the attempt counter on each submission.

        # Calculate the instructor's answer and determine if the user's answer is correct.
        instr1 = (w0()*0.5*a()+w0()*(b()-a()))/1000
        instr2 = (w0()*b()**2/4+w0()*a()*b()/2)/1000

        correct1 = math.isclose(float(input.answer1()), instr1, rel_tol=0.01)
        correct2 = math.isclose(float(input.answer2()), instr2, rel_tol=0.01)
        
        if correct1 and correct2:
            check = f"{'both correct.'}"
        elif correct1:
            check = f" {'correct for answer 1 and incorrect for answer 2.'}"
        elif correct2:
            check = f"{'incorrect for answer 1 and correct for answer 2.'}"
        else:
            check = f"{'both incorrect.'}"
        
        correct_indicator = "JL" if correct1 and correct2 else "JG"

        random_start = generate_random_letters(4)
        random_middle = generate_random_letters(4)
        random_end = generate_random_letters(4)
        encoded_attempt = f"{random_start}{problem_ID}-{random_middle}{attempt_counter()}{correct_indicator}-{random_end}{input.ID()}"

        session.encoded_attempt = reactive.Value(encoded_attempt)
        attempts.append(f"{datetime.now()}, {attempt_counter()}, {input.answer1()}, {input.answer2()}, {check}\n")

        feedback = ui.markdown(f"Your answers of {input.answer1()} and {input.answer2()} are {check}. For reference in debugging this, the calculated instructor answers are {instr1} and {instr2}")
        m = ui.modal(feedback, title="Feedback", easy_close=True)
        ui.modal_show(m)

    @session.download(filename=lambda: f"Problem_Log-{problem_ID}-{input.ID()}.csv")
    async def download():
        final_encoded = session.encoded_attempt() if session.encoded_attempt is not None else "No attempts"
        yield f"{final_encoded}\n\n"
        yield "Timestamp,Attempt,Answer1,Answer2,Feedback\n"
        for attempt in attempts[1:]:
            await asyncio.sleep(0.25)
            yield attempt

app = App(app_ui, server)