Add Body Composition Calculator play (#1672)

Co-authored-by: Priyankar Pal <88102392+priyankarpal@users.noreply.github.com>

Author: deansereigns

src/plays/body-composition-calculator/BodyCompositionCalculator.tsx

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+import React, { useMemo, useState } from 'react';
+
+import './styles/styles.css';
+import CalculatorForm from './components/CalculatorForm';
+import ResultDisplay from './components/ResultDisplay';
+
+import { calculateBMR, calculateTDEE } from './utils/healthUtils';
+import { FormData } from './types';
+
+const BodyCompositionCalculator: React.FC = () => {
+  const [formData, setFormData] = useState<FormData>({
+    gender: 'male',
+    weight: '',
+    height: '',
+    age: '',
+    activityLevel: 'sedentary'
+  });
+
+  /**
+   * Generic handler for updating form state
+   */
+  const handleChange = (field: keyof FormData, value: string) => {
+    setFormData((prev) => ({
+      ...prev,
+      [field]: value
+    }));
+  };
+
+  /**
+   * Convert Inputs Safely
+   */
+  const numericWeight = Number(formData.weight);
+  const numericHeight = Number(formData.height);
+  const numericAge = Number(formData.age);
+
+  const isValid = numericWeight > 0 && numericHeight > 0 && numericAge > 0;
+
+  /**
+   * Derived BMR
+   */
+  const bmr = useMemo(() => {
+    if (!isValid) return null;
+
+    return calculateBMR({
+      gender: formData.gender,
+      weight: numericWeight,
+      height: numericHeight,
+      age: numericAge
+    });
+  }, [formData.gender, numericWeight, numericHeight, numericAge, isValid]);
+
+  /**
+   * Derived TDEE
+   */
+  const tdee = useMemo(() => {
+    if (!bmr) return null;
+
+    return calculateTDEE(bmr, formData.activityLevel);
+  }, [bmr, formData.activityLevel]);
+
+  return (
+    <div className="container">
+      <h2 className="calculator-title">BMR & TDEE Calculator</h2>
+
+      <p className="calculator-summary">
+        <strong>BMR (Basal Metabolic Rate)</strong> is the number of calories your body needs at
+        complete rest to maintain essential functions such as breathing, circulation, and
+        temperature regulation.
+        <br />
+        <br />
+        <strong>TDEE (Total Daily Energy Expenditure)</strong> is the total number of calories your
+        body burns in a day, including all physical activities like walking, exercise, and daily
+        tasks.
+      </p>
+      <CalculatorForm formData={formData} onChange={handleChange} />
+
+      <ResultDisplay bmr={bmr} tdee={tdee} />
+    </div>
+  );
+};
+
+export default BodyCompositionCalculator;

src/plays/body-composition-calculator/Readme.md

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+# Body Composition Calculator
+
+An interactive Body Composition Calculator that computes Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using scientifically validated formulas.
+
+This calculator helps users understand their daily calorie requirements based on body measurements and activity level.
+
+---
+
+## Play Demographic
+
+- Language: TypeScript
+- Level: Intermediate
+- Category: Health / Fitness / Calculator
+
+---
+
+## Creator Information
+
+- User: deansereigns
+- GitHub Link: https://github.com/deansereigns
+
+---
+
+## Implementation Details
+
+This play is built using React and TypeScript with a modular and scalable architecture.
+
+The calculator uses the **Mifflin-St Jeor Equation**, which is considered one of the most accurate formulas for estimating Basal Metabolic Rate.
+
+### BMR (Basal Metabolic Rate)
+
+BMR represents the number of calories your body requires to perform essential life-sustaining functions while at rest.
+
+These include:
+
+- Breathing
+- Blood circulation
+- Brain activity
+- Cell production
+- Maintaining body temperature
+
+Formula used:
+
+Male:
+
+```text
+BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age_years) + 5
+```
+
+Female:
+
+```text
+BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age_years) − 161
+```
+
+---
+
+### TDEE (Total Daily Energy Expenditure)
+
+TDEE represents the total calories your body burns in a day including all physical activities.
+
+It is calculated by multiplying BMR with an activity multiplier.
+
+Formula:
+```text
+TDEE = BMR × activity_multiplier
+```
+
+Activity multipliers used:
+
+| Activity Level | Multiplier |
+|---------------|------------|
+| Sedentary | 1.2 |
+| Light Activity | 1.375 |
+| Moderate Activity | 1.55 |
+| Active | 1.725 |
+| Very Active | 1.9 |
+
+---
+
+### Features Implemented
+
+- Built with TypeScript for type safety
+- Modular and reusable component structure
+- Real-time BMR and TDEE calculation using React Hooks
+- Controlled form inputs with validation
+- Clean and responsive user interface
+
+---
+
+## Considerations
+
+- Validates inputs before performing calculations
+- Handles empty or invalid values safely
+- Optimized using React Hooks
+- Easily extendable for additional health metrics
+
+---
+
+## Future Improvements
+
+- BMI and body fat calculator
+- Calorie recommendations for weight goals
+- Enhanced UI and data visualization

src/plays/body-composition-calculator/components/CalculatorForm.tsx

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+import React, { ChangeEvent } from 'react';
+import { FormData, Gender, ActivityLevel } from '../types';
+
+interface CalculatorFormProps {
+  formData: FormData;
+  onChange: (field: keyof FormData, value: string) => void;
+}
+
+/**
+ * Calculator Form
+ *
+ * Responsible for rendering and managing all input fields.
+ * This is a presentational component with no business logic.
+ */
+const CalculatorForm: React.FC<CalculatorFormProps> = ({ formData, onChange }) => {
+  /**
+   * Handle select change safely with typing
+   */
+  const handleGenderChange = (event: ChangeEvent<HTMLSelectElement>) => {
+    onChange('gender', event.target.value as Gender);
+  };
+
+  const handleActivityChange = (event: ChangeEvent<HTMLSelectElement>) => {
+    onChange('activityLevel', event.target.value as ActivityLevel);
+  };
+
+  /**
+   * Handle numeric input changes
+   */
+  const handleWeightChange = (event: ChangeEvent<HTMLInputElement>) => {
+    onChange('weight', event.target.value);
+  };
+
+  const handleHeightChange = (event: ChangeEvent<HTMLInputElement>) => {
+    onChange('height', event.target.value);
+  };
+
+  const handleAgeChange = (event: ChangeEvent<HTMLInputElement>) => {
+    onChange('age', event.target.value);
+  };
+
+  return (
+    <div className="form">
+      {/* Gender*/}
+      <label>
+        Gender
+        <select value={formData.gender} onChange={handleGenderChange}>
+          <option value="male">Male</option>
+          <option value="female">Female</option>
+        </select>
+      </label>
+
+      {/* Weight*/}
+      <label>
+        Weight (kg)
+        <input
+          min="40"
+          placeholder="Enter weight"
+          type="number"
+          value={formData.weight}
+          onChange={handleWeightChange}
+        />
+      </label>
+
+      {/* Height*/}
+      <label>
+        Height (cm)
+        <input
+          min="70"
+          placeholder="Enter Height"
+          type="number"
+          value={formData.height}
+          onChange={handleHeightChange}
+        />
+      </label>
+
+      {/* Age*/}
+      <label>
+        Age
+        <input
+          min="10"
+          placeholder="Enter Age"
+          type="number"
+          value={formData.age}
+          onChange={handleAgeChange}
+        />
+      </label>
+
+      {/* Activity Level */}
+      <label>
+        Activity Level
+        <select value={formData.activityLevel} onChange={handleActivityChange}>
+          <option value="sedentary">Sedentary (little or no exercise)</option>
+          <option value="light">Light (1-3 days/week)</option>
+          <option value="moderate">Moderate (3-5 days/week)</option>
+          <option value="active">Active (6-7 days/week)</option>
+          <option value="very_active">Very Active (physical job or intense training)</option>
+        </select>
+      </label>
+    </div>
+  );
+};
+
+export default CalculatorForm;

src/plays/body-composition-calculator/components/ResultDisplay.tsx

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+import React from 'react';
+
+interface ResultDisplayProps {
+  bmr: number | null;
+  tdee: number | null;
+}
+
+/**
+ * ResultDisplay Component
+ *
+ * Displays calculated BMR and TDEE values.
+ * Pure Presentational component.
+ */
+const ResultDisplay: React.FC<ResultDisplayProps> = ({ bmr, tdee }) => {
+  /**
+   * Format number Safely
+   */
+  const formatValue = (value: number | null): string => {
+    if (value === null || Number.isNaN(value)) {
+      return '--';
+    }
+
+    return `${Math.round(value)} kcal/day`;
+  };
+
+  return (
+    <div className="result-container">
+      <h3>Results</h3>
+
+      <div className="result-item">
+        <span className="label">BMR</span>
+        <span className="value">{formatValue(bmr)}</span>
+      </div>
+
+      <div className="result-item">
+        <span className="label">TDEE</span>
+        <span className="value">{formatValue(tdee)}</span>
+      </div>
+
+      {bmr === null && <p className="hint">Enter weight, height, and age to calculate.</p>}
+    </div>
+  );
+};
+
+export default ResultDisplay;