import React, { useState, useEffect, useRef } from 'react';
import { initializeApp, getApps, getApp } from 'firebase/app';
import { getAuth, signInAnonymously, signInWithCustomToken, onAuthStateChanged } from 'firebase/auth';
import { getFirestore, collection, addDoc, query, orderBy, onSnapshot, serverTimestamp, Timestamp } from 'firebase/firestore';
import { Line } from 'react-chartjs-2';
import { Chart as ChartJS, CategoryScale, LinearScale, PointElement, LineElement, Title, Tooltip, Legend } from 'chart.js';

// Register Chart.js components
ChartJS.register(CategoryScale, LinearScale, PointElement, LineElement, Title, Tooltip, Legend);

// Define global variables for Firebase configuration (provided by the environment)
const appId = typeof __app_id !== 'undefined' ? __app_id : 'default-app-id';
const firebaseConfig = typeof __firebase_config !== 'undefined' ? JSON.parse(__firebase_config) : {};
const initialAuthToken = typeof __initial_auth_token !== 'undefined' ? __initial_auth_token : null;

// Initialize Firebase (will be done once in useEffect)
let app = null;
let db = null;
let auth = null;

// Check if Firebase app is already initialized
if (!getApps().length) {
    app = initializeApp(firebaseConfig);
    db = getFirestore(app);
    auth = getAuth(app);
}

function App() {
    const [weight, setWeight] = useState('');
    const [height, setHeight] = useState('');
    const [age, setAge] = useState('');
    const [neckCircumference, setNeckCircumference] = useState('');
    const [waistCircumference, setWaistCircumference] = useState('');
    const [hipCircumference, setHipCircumference] = useState(''); // Only for female formula
    const [femininityPercentage, setFemininityPercentage] = useState(50); // 0-100, 0=Masculine, 100=Feminine
    const [calculatedBMI, setCalculatedBMI] = useState(null);
    const [calculatedBF, setCalculatedBF] = useState(null);
    const [calculatedLeanMass, setCalculatedLeanMass] = useState(null);
    const [calculatedFatMass, setCalculatedFatMass] = useState(null);
    const [notes, setNotes] = useState('');
    const [history, setHistory] = useState([]);
    const [userId, setUserId] = useState(null);
    const [loading, setLoading] = useState(true);
    const [error, setError] = useState('');
    const [message, setMessage] = useState('');
    const [unitSystem, setUnitSystem] = useState('imperial'); // 'imperial' or 'metric'
    const [inputDate, setInputDate] = useState(new Date().toISOString().split('T')[0]); // Default to current date
    const isFirebaseInitialized = useRef(false);
    const appVersion = "0.6"; // Define the app version

    // Initialize Firebase and set up authentication
    useEffect(() => {
        const initializeFirebase = async () => {
            if (isFirebaseInitialized.current) return;

            // Use the already initialized app if it exists
            if (!app) {
                 app = initializeApp(firebaseConfig);
                 db = getFirestore(app);
                 auth = getAuth(app);
            }
            try {

                // Sign in with custom token if available, otherwise anonymously
                if (initialAuthToken) {
                    await signInWithCustomToken(auth, initialAuthToken);
                } else {
                    await signInAnonymously(auth);
                }

                // Listen for auth state changes
                onAuthStateChanged(auth, (user) => {
                    if (user) {
                        setUserId(user.uid);
                        setLoading(false);
                    } else {
                        setUserId(crypto.randomUUID()); // Fallback for unauthenticated or anonymous users
                        setLoading(false);
                    }
                });

                isFirebaseInitialized.current = true;
            } catch (err) {
                console.error("Firebase initialization error:", err);
                setError("Failed to initialize Firebase. Please try again later.");
                setLoading(false);
            }
        };

        initializeFirebase();
    }, []);

    // Fetch data from Firestore when userId is available
    useEffect(() => {
        if (!userId || !db) return;

        const q = query(
            collection(db, `artifacts/${appId}/users/${userId}/bodyCompositionData`),
            orderBy('date', 'desc') // Order by date descending for history
        );

        const unsubscribe = onSnapshot(q, (snapshot) => {
            const data = snapshot.docs.map(doc => ({
                id: doc.id,
                ...doc.data(),
                // If customDate is present, use it, otherwise fall back to serverTimestamp
                date: doc.data().customDate || doc.data().date?.toDate().toISOString().split('T')[0] || 'N/A'
            }));
            setHistory(data);
        }, (err) => {
            console.error("Error fetching data:", err);
            setError("Failed to load historical data.");
        });

        return () => unsubscribe(); // Cleanup listener on component unmount
    }, [userId]); // Depend on userId to re-run when auth state is ready

    // Conversion functions
    const kgToLbs = (kg) => kg * 2.20462;
    const lbsToKg = (lbs) => lbs / 2.20462;
    const cmToInches = (cm) => cm * 0.393701;
    const inchesToCm = (inches) => inches / 0.393701;

    // Function to calculate BMI (always uses lbs and inches internally)
    const calculateBMI = (weightLbs, heightInches) => {
        if (!weightLbs || !heightInches) return null;
        return (weightLbs / (heightInches * heightInches)) * 703;
    };

    // Function to calculate Body Fat Percentage using U.S. Navy Method (always uses inches internally)
    const calculateBodyFatNavyMethod = (weightLbs, heightInches, neckInches, waistInches, hipInches, femininity) => {
        if (!weightLbs || !heightInches || !neckInches || !waistInches) return null;

        // Rounding rules for U.S. Navy Method
        const roundedNeck = Math.ceil(neckInches * 2) / 2; // round up to nearest 0.5 inch
        const roundedWaist = Math.floor(waistInches * 2) / 2; // round down to nearest 0.5 inch
        const roundedHeight = Math.round(heightInches * 2) / 2; // round to nearest 0.5 inch

        // Male formula
        const bfMale = 86.010 * Math.log10(roundedWaist - roundedNeck) - 70.041 * Math.log10(roundedHeight) + 36.76;

        // Female formula (requires hip circumference)
        let bfFemale = null;
        if (hipInches) {
            const roundedHip = Math.floor(hipInches * 2) / 2; // round down to nearest 0.5 inch
            bfFemale = 163.205 * Math.log10(roundedWaist + roundedHip - roundedNeck) - 97.684 * Math.log10(roundedHeight) - 78.387;
        }

        // Interpolate based on femininity percentage
        if (bfFemale === null) {
            // If hip is not provided, we can't calculate female formula, so just use male.
            // Or, we could default to a more general formula if available, but for now,
            // we'll highlight that hip is needed for full interpolation.
            return bfMale; // Fallback to male if female calculation is not possible
        }

        // Linear interpolation: 0% femininity = 100% Male, 100% femininity = 100% Female
        const interpolationFactor = femininity / 100;
        const interpolatedBF = bfMale * (1 - interpolationFactor) + bfFemale * interpolationFactor;

        return interpolatedBF;
    };

    const handleCalculate = () => {
        setError('');
        setMessage('');

        let w = parseFloat(weight);
        let h = parseFloat(height);
        let n = parseFloat(neckCircumference);
        let wa = parseFloat(waistCircumference);
        let hi = parseFloat(hipCircumference);
        const a = parseFloat(age);

        if (isNaN(w) || isNaN(h) || isNaN(a) || isNaN(n) || isNaN(wa)) {
            setError('Please enter valid numbers for all required fields (Weight, Height, Age, Neck, Waist).');
            return;
        }

        // Convert to imperial units if current system is metric
        let weightLbs = w;
        let heightInches = h;
        let neckInches = n;
        let waistInches = wa;
        let hipInches = hi;

        if (unitSystem === 'metric') {
            weightLbs = kgToLbs(w);
            heightInches = cmToInches(h);
            neckInches = cmToInches(n);
            waistInches = cmToInches(wa);
            hipInches = hi ? cmToInches(hi) : null;
        }

        // Calculate BMI
        const bmi = calculateBMI(weightLbs, heightInches);
        setCalculatedBMI(bmi ? bmi.toFixed(2) : null);

        // Calculate Body Fat
        const bf = calculateBodyFatNavyMethod(weightLbs, heightInches, neckInches, waistInches, hipInches, femininityPercentage);
        setCalculatedBF(bf ? bf.toFixed(2) : null);

        // Calculate Lean Mass and Fat Mass if BF is available
        if (bf !== null) {
            const fatMassLbs = (bf / 100) * weightLbs;
            const leanMassLbs = weightLbs - fatMassLbs;

            // Convert back to metric if unit system is metric
            setCalculatedFatMass(unitSystem === 'metric' ? lbsToKg(fatMassLbs).toFixed(2) : fatMassLbs.toFixed(2));
            setCalculatedLeanMass(unitSystem === 'metric' ? lbsToKg(leanMassLbs).toFixed(2) : leanMassLbs.toFixed(2));
        } else {
            setCalculatedFatMass(null);
            setCalculatedLeanMass(null);
        }
    };

    const handleSave = async () => {
        setError('');
        setMessage('');

        if (!userId) {
            setError("User not authenticated. Please wait or refresh.");
            return;
        }

        if (calculatedBMI === null || calculatedBF === null) {
            setError("Please calculate body composition before saving.");
            return;
        }

        try {
            // Use the inputDate if provided, otherwise use serverTimestamp
            const timestampToSave = inputDate ? inputDate : serverTimestamp();

            await addDoc(collection(db, `artifacts/${appId}/users/${userId}/bodyCompositionData`), {
                date: serverTimestamp(), // Keep serverTimestamp for ordering
                customDate: inputDate, // Store the user-selected date string
                weight: parseFloat(weight),
                height: parseFloat(height),
                age: parseInt(age),
                neckCircumference: parseFloat(neckCircumference),
                waistCircumference: parseFloat(waistCircumference),
                hipCircumference: parseFloat(hipCircumference || 0), // Store 0 if not provided
                femininityPercentage: parseInt(femininityPercentage),
                calculatedBMI: parseFloat(calculatedBMI),
                calculatedBF: parseFloat(calculatedBF),
                calculatedLeanMass: parseFloat(calculatedLeanMass),
                calculatedFatMass: parseFloat(calculatedFatMass),
                notes: notes,
                unitSystem: unitSystem, // Save the unit system used for this entry
            });
            setMessage("Data saved successfully!");
            setNotes(''); // Clear notes after saving
            setInputDate(new Date().toISOString().split('T')[0]); // Reset date to current
        } catch (e) {
            console.error("Error adding document: ", e);
            setError("Failed to save data. Please try again.");
        }
    };

    const handleExportToCSV = () => {
        if (history.length === 0) {
            setError("No data to export.");
            return;
        }

        // Define CSV headers
        const headers = [
            'Date',
            `Weight (${unitSystem === 'imperial' ? 'lbs' : 'kg'})`,
            `Height (${unitSystem === 'imperial' ? 'in' : 'cm'})`,
            'Age',
            `Neck Circumference (${unitSystem === 'imperial' ? 'in' : 'cm'})`,
            `Waist Circumference (${unitSystem === 'imperial' ? 'in' : 'cm'})`,
            `Hip Circumference (${unitSystem === 'imperial' ? 'in' : 'cm'})`,
            'Femininity Percentage',
            'BMI',
            'Body Fat %',
            `Lean Mass (${unitSystem === 'imperial' ? 'lbs' : 'kg'})`,
            `Fat Mass (${unitSystem === 'imperial' ? 'lbs' : 'kg'})`,
            'Notes',
            'Unit System'
        ];

        // Format data rows
        const csvRows = history.map(entry => {
            // Ensure values are strings and handle commas in notes by enclosing in quotes
            const formattedNotes = `"${(entry.notes || '').replace(/"/g, '""')}"`; // Escape double quotes

            // Convert to currently selected unit system for export display
            const displayWeight = entry.unitSystem === unitSystem ? entry.weight :
                                  unitSystem === 'imperial' ? kgToLbs(entry.weight).toFixed(2) : lbsToKg(entry.weight).toFixed(2);
            const displayHeight = entry.unitSystem === unitSystem ? entry.height :
                                  unitSystem === 'imperial' ? cmToInches(entry.height).toFixed(2) : inchesToCm(entry.height).toFixed(2);
            const displayNeck = entry.unitSystem === unitSystem ? entry.neckCircumference :
                                unitSystem === 'imperial' ? cmToInches(entry.neckCircumference).toFixed(2) : inchesToCm(entry.neckCircumference).toFixed(2);
            const displayWaist = entry.unitSystem === unitSystem ? entry.waistCircumference :
                                 unitSystem === 'imperial' ? cmToInches(entry.waistCircumference).toFixed(2) : inchesToCm(entry.waistCircumference).toFixed(2);
            const displayHip = entry.unitSystem === unitSystem ? (entry.hipCircumference || '') :
                               (entry.hipCircumference ? (unitSystem === 'imperial' ? cmToInches(entry.hipCircumference).toFixed(2) : inchesToCm(entry.hipCircumference).toFixed(2)) : '');

            return [
                entry.date,
                displayWeight,
                displayHeight,
                entry.age,
                displayNeck,
                displayWaist,
                displayHip,
                entry.femininityPercentage,
                entry.calculatedBMI,
                entry.calculatedBF,
                entry.calculatedLeanMass,
                entry.calculatedFatMass,
                formattedNotes,
                entry.unitSystem
            ].join(',');
        });

        // Combine headers and rows
        const csvContent = [
            headers.join(','),
            ...csvRows
        ].join('\n');

        // Create a Blob and trigger download
        const blob = new Blob([csvContent], { type: 'text/csv;charset=utf-8;' });
        const link = document.createElement('a');
        link.href = URL.createObjectURL(blob);
        link.download = 'body_composition_data.csv';
        document.body.appendChild(link);
        link.click();
        document.body.removeChild(link);
        URL.revokeObjectURL(link.href);
        setMessage("Data exported successfully to body_composition_data.csv!");
    };


    // Prepare data for Chart.js
    const chartData = {
        labels: history.map(entry => entry.date).reverse(), // Reverse to show oldest first
        datasets: [
            {
                label: `Weight (${unitSystem === 'imperial' ? 'lbs' : 'kg'})`,
                data: history.map(entry => unitSystem === 'imperial' ? entry.weight : lbsToKg(entry.weight)).reverse(),
                borderColor: 'rgb(75, 192, 192)',
                backgroundColor: 'rgba(75, 192, 192, 0.5)',
                yAxisID: 'y',
            },
            {
                label: 'Body Fat %',
                data: history.map(entry => entry.calculatedBF).reverse(),
                borderColor: 'rgb(255, 99, 132)',
                backgroundColor: 'rgba(255, 99, 132, 0.5)',
                yAxisID: 'y1',
            },
            {
                label: 'Femininity %',
                data: history.map(entry => entry.femininityPercentage).reverse(),
                borderColor: 'rgb(153, 102, 255)',
                backgroundColor: 'rgba(153, 102, 255, 0.5)',
                yAxisID: 'y2',
            }
        ],
    };

    const chartOptions = {
        responsive: true,
        maintainAspectRatio: false,
        interaction: {
            mode: 'index',
            intersect: false,
        },
        stacked: false,
        plugins: {
            title: {
                display: true,
                text: 'Body Composition Trends',
            },
        },
        scales: {
            x: {
                title: {
                    display: true,
                    text: 'Date',
                },
            },
            y: {
                type: 'linear',
                display: true,
                position: 'left',
                title: {
                    display: true,
                    text: `Weight (${unitSystem === 'imperial' ? 'lbs' : 'kg'})`,
                },
            },
            y1: {
                type: 'linear',
                display: true,
                position: 'right',
                title: {
                    display: true,
                    text: 'Body Fat %',
                },
                grid: {
                    drawOnChartArea: false, // Only draw grid lines for the first axis
                },
            },
            y2: {
                type: 'linear',
                display: true,
                position: 'right',
                title: {
                    display: true,
                    text: 'Femininity %',
                },
                grid: {
                    drawOnChartArea: false, // Only draw grid lines for the first axis
                },
            },
        },
    };

    if (loading) {
        return (
            <div className="min-h-screen flex items-center justify-center bg-gradient-to-br from-purple-100 to-pink-100 p-4">
                <div className="text-xl font-semibold text-purple-700">Loading app...</div>
            </div>
        );
    }

    return (
        <div className="min-h-screen bg-gradient-to-br from-purple-100 to-pink-100 flex flex-col items-center justify-center p-4">
            <div className="bg-white p-8 rounded-xl shadow-2xl w-full max-w-4xl space-y-8">
                <h1 className="text-4xl font-extrabold text-center text-purple-800 mb-6">
                    Inclusive Body Composition Tracker
                    <span className="block text-base font-medium text-gray-500 mt-2">Version {appVersion}</span>
                </h1>

                {error && (
                    <div className="bg-red-100 border border-red-400 text-red-700 px-4 py-3 rounded-md relative" role="alert">
                        <strong className="font-bold">Error!</strong>
                        <span className="block sm:inline"> {error}</span>
                    </div>
                )}
                {message && (
                    <div className="bg-green-100 border border-green-400 text-green-700 px-4 py-3 rounded-md relative" role="alert">
                        <strong className="font-bold">Success!</strong>
                        <span className="block sm:inline"> {message}</span>
                    </div>
                )}

                <div className="flex justify-center mb-6">
                    <button
                        onClick={() => setUnitSystem('imperial')}
                        className={`px-6 py-2 rounded-l-lg font-semibold transition-colors duration-200 ${unitSystem === 'imperial' ? 'bg-purple-600 text-white shadow-md' : 'bg-gray-200 text-gray-700 hover:bg-gray-300'}`}
                    >
                        Imperial (lbs, in)
                    </button>
                    <button
                        onClick={() => setUnitSystem('metric')}
                        className={`px-6 py-2 rounded-r-lg font-semibold transition-colors duration-200 ${unitSystem === 'metric' ? 'bg-purple-600 text-white shadow-md' : 'bg-gray-200 text-gray-700 hover:bg-gray-300'}`}
                    >
                        Metric (kg, cm)
                    </button>
                </div>

                <div className="grid grid-cols-1 md:grid-cols-2 gap-6">
                    <div className="space-y-4">
                        <h2 className="text-2xl font-bold text-purple-700">Your Measurements</h2>
                        <div>
                            <label htmlFor="inputDate" className="block text-sm font-medium text-gray-700">Date</label>
                            <input
                                type="date"
                                id="inputDate"
                                value={inputDate}
                                onChange={(e) => setInputDate(e.target.value)}
                                className="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-purple-500 focus:border-purple-500 sm:text-sm"
                            />
                        </div>
                        <div>
                            <label htmlFor="weight" className="block text-sm font-medium text-gray-700">Weight ({unitSystem === 'imperial' ? 'lbs' : 'kg'})</label>
                            <input
                                type="number"
                                id="weight"
                                value={weight}
                                onChange={(e) => setWeight(e.target.value)}
                                className="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-purple-500 focus:border-purple-500 sm:text-sm"
                                placeholder={unitSystem === 'imperial' ? 'e.g., 150' : 'e.g., 68'}
                            />
                        </div>
                        <div>
                            <label htmlFor="height" className="block text-sm font-medium text-gray-700">Height ({unitSystem === 'imperial' ? 'inches' : 'cm'})</label>
                            <input
                                type="number"
                                id="height"
                                value={height}
                                onChange={(e) => setHeight(e.target.value)}
                                className="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-purple-500 focus:border-purple-500 sm:text-sm"
                                placeholder={unitSystem === 'imperial' ? 'e.g., 68' : 'e.g., 173'}
                            />
                        </div>
                        <div>
                            <label htmlFor="age" className="block text-sm font-medium text-gray-700">Age</label>
                            <input
                                type="number"
                                id="age"
                                value={age}
                                onChange={(e) => setAge(e.target.value)}
                                className="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-purple-500 focus:border-purple-500 sm:text-sm"
                                placeholder="e.g., 30"
                            />
                        </div>
                        <div>
                            <label htmlFor="neck" className="block text-sm font-medium text-gray-700">Neck Circumference ({unitSystem === 'imperial' ? 'inches' : 'cm'})</label>
                            <input
                                type="number"
                                id="neck"
                                value={neckCircumference}
                                onChange={(e) => setNeckCircumference(e.target.value)}
                                className="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-purple-500 focus:border-purple-500 sm:text-sm"
                                placeholder={unitSystem === 'imperial' ? 'e.g., 15' : 'e.g., 38'}
                            />
                        </div>
                        <div>
                            <label htmlFor="waist" className="block text-sm font-medium text-gray-700">Waist Circumference ({unitSystem === 'imperial' ? 'inches' : 'cm'})</label>
                            <input
                                type="number"
                                id="waist"
                                value={waistCircumference}
                                onChange={(e) => setWaistCircumference(e.target.value)}
                                className="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-purple-500 focus:border-purple-500 sm:text-sm"
                                placeholder={unitSystem === 'imperial' ? 'e.g., 30' : 'e.g., 76'}
                            />
                        </div>
                        <div>
                            <label htmlFor="hip" className="block text-sm font-medium text-gray-700">Hip Circumference ({unitSystem === 'imperial' ? 'inches' : 'cm'}) - *For Feminine Calculation*</label>
                            <input
                                type="number"
                                id="hip"
                                value={hipCircumference}
                                onChange={(e) => setHipCircumference(e.target.value)}
                                className="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-purple-500 focus:border-purple-500 sm:text-sm"
                                placeholder={unitSystem === 'imperial' ? 'e.g., 38' : 'e.g., 96'}
                            />
                        </div>
                    </div>

                    <div className="space-y-4">
                        <h2 className="text-2xl font-bold text-purple-700">Femininity Crossfade</h2>
                        <div>
                            <label htmlFor="femininity" className="block text-sm font-medium text-gray-700">
                                Femininity Percentage: {femininityPercentage}%
                            </label>
                            <input
                                type="range"
                                id="femininity"
                                min="0"
                                max="100"
                                value={femininityPercentage}
                                onChange={(e) => setFemininityPercentage(e.target.value)}
                                className="mt-1 w-full h-2 bg-purple-200 rounded-lg appearance-none cursor-pointer accent-purple-500"
                            />
                            <div className="flex justify-between text-xs text-gray-500 mt-1">
                                <span>Masculine (0%)</span>
                                <span>Feminine (100%)</span>
                            </div>
                            <p className="text-sm text-gray-600 mt-2">
                                Adjust this slider to blend between masculine and feminine body composition calculations. This helps visualize changes over time or find an average range.
                            </p>
                        </div>

                        <div className="mt-6">
                            <h2 className="text-2xl font-bold text-purple-700">Calculated Results</h2>
                            <div className="bg-purple-50 p-4 rounded-lg shadow-inner mt-4 space-y-2">
                                <p className="text-lg font-semibold text-gray-800">BMI: <span className="text-purple-600">{calculatedBMI || 'N/A'}</span></p>
                                <p className="text-lg font-semibold text-gray-800">Body Fat %: <span className="text-purple-600">{calculatedBF || 'N/A'}</span></p>
                                <p className="text-lg font-semibold text-gray-800">Lean Mass ({unitSystem === 'imperial' ? 'lbs' : 'kg'}): <span className="text-purple-600">{calculatedLeanMass || 'N/A'}</span></p>
                                <p className="text-lg font-semibold text-gray-800">Fat Mass ({unitSystem === 'imperial' ? 'lbs' : 'kg'}): <span className="text-purple-600">{calculatedFatMass || 'N/A'}</span></p>
                            </div>
                        </div>

                        <div>
                            <label htmlFor="notes" className="block text-sm font-medium text-gray-700">Notes (e.g., HRT start date, surgery date)</label>
                            <textarea
                                id="notes"
                                rows="3"
                                value={notes}
                                onChange={(e) => setNotes(e.target.value)}
                                className="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-purple-500 focus:border-purple-500 sm:text-sm"
                                placeholder="Add any relevant notes here..."
                            ></textarea>
                        </div>

                        <div className="flex flex-col sm:flex-row gap-4 mt-6">
                            <button
                                onClick={handleCalculate}
                                className="flex-1 bg-purple-600 hover:bg-purple-700 text-white font-bold py-3 px-6 rounded-lg shadow-lg transform transition duration-300 ease-in-out hover:scale-105 focus:outline-none focus:ring-2 focus:ring-purple-500 focus:ring-opacity-75"
                            >
                                Calculate
                            </button>
                            <button
                                onClick={handleSave}
                                className="flex-1 bg-pink-500 hover:bg-pink-600 text-white font-bold py-3 px-6 rounded-lg shadow-lg transform transition duration-300 ease-in-out hover:scale-105 focus:outline-none focus:ring-2 focus:ring-pink-400 focus:ring-opacity-75"
                            >
                                Save Data
                            </button>
                        </div>
                    </div>
                </div>

                <div className="mt-8">
                    <h2 className="text-2xl font-bold text-purple-700 mb-4">Your Progress Over Time</h2>
                    <p className="text-sm text-gray-600 mb-4">
                        Your User ID: <span className="font-mono text-purple-700 break-all">{userId || 'N/A'}</span>
                    </p>
                    <div className="h-80 w-full mb-8">
                        {history.length > 0 ? (
                            <Line data={chartData} options={chartOptions} />
                        ) : (
                            <p className="text-center text-gray-500">No data yet. Save your first entry to see your progress!</p>
                        )}
                    </div>

                    <h3 className="text-xl font-bold text-purple-700 mb-3">Historical Entries</h3>
                    {history.length === 0 ? (
                        <p className="text-gray-500">No historical data available.</p>
                    ) : (
                        <div className="overflow-x-auto rounded-lg shadow-md">
                            <table className="min-w-full divide-y divide-gray-200">
                                <thead className="bg-purple-50">
                                    <tr>
                                        <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider rounded-tl-lg">Date</th>
                                        <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Weight ({unitSystem === 'imperial' ? 'lbs' : 'kg'})</th>
                                        <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Height ({unitSystem === 'imperial' ? 'in' : 'cm'})</th>
                                        <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">BF %</th>
                                        <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Femininity %</th>
                                        <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Notes</th>
                                        <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider rounded-tr-lg">Units</th>
                                    </tr>
                                </thead>
                                <tbody className="bg-white divide-y divide-gray-200">
                                    {history.map((entry) => (
                                        <tr key={entry.id} className="hover:bg-gray-50">
                                            <td className="px-6 py-4 whitespace-nowrap text-sm font-medium text-gray-900">{entry.date}</td>
                                            <td className="px-6 py-4 whitespace-nowrap text-sm text-gray-700">{entry.weight}</td>
                                            <td className="px-6 py-4 whitespace-nowrap text-sm text-gray-700">{entry.height}</td>
                                            <td className="px-6 py-4 whitespace-nowrap text-sm text-gray-700">{entry.calculatedBF}</td>
                                            <td className="px-6 py-4 whitespace-nowrap text-sm text-gray-700">{entry.femininityPercentage}</td>
                                            <td className="px-6 py-4 whitespace-nowrap text-sm text-gray-700">{entry.notes || 'N/A'}</td>
                                            <td className="px-6 py-4 whitespace-nowrap text-sm text-gray-700">{entry.unitSystem || 'imperial'}</td>
                                        </tr>
                                    ))}
                                </tbody>
                            </table>
                        </div>
                    )}
                    <div className="mt-6 flex justify-center">
                        <button
                            onClick={handleExportToCSV}
                            className="bg-green-600 hover:bg-green-700 text-white font-bold py-3 px-6 rounded-lg shadow-lg transform transition duration-300 ease-in-out hover:scale-105 focus:outline-none focus:ring-2 focus:ring-green-500 focus:ring-opacity-75"
                        >
                            Export Data to CSV
                        </button>
                    </div>
                </div>
            </div>
        </div>
    );
}

export default App;