//
// WeightProgressionChartView.swift
// Workouts
//
// Created on 7/20/25.
//
// Copyright 2025 Rouslan Zenetl. All Rights Reserved.
//

import SwiftUI
import Charts
import CoreData

struct WeightProgressionChartView: View {
    @Environment(\.managedObjectContext) private var viewContext

    let exerciseName: String
    @State private var weightData: [WeightDataPoint] = []
    @State private var isLoading: Bool = true
    @State private var motivationalMessage: String = ""

    var body: some View {
        VStack(alignment: .leading) {
            if isLoading {
                ProgressView("Loading data...")
            } else if weightData.isEmpty {
                Text("No weight history available yet.")
                    .foregroundColor(.secondary)
                    .frame(maxWidth: .infinity, alignment: .center)
                    .padding()
            } else {
                Text("Weight Progression")
                    .font(.headline)
                    .padding(.bottom, 4)

                Chart {
                    ForEach(weightData) { dataPoint in
                        LineMark(
                            x: .value("Date", dataPoint.date),
                            y: .value("Weight", dataPoint.weight)
                        )
                        .foregroundStyle(Color.blue.gradient)
                        .interpolationMethod(.catmullRom)

                        PointMark(
                            x: .value("Date", dataPoint.date),
                            y: .value("Weight", dataPoint.weight)
                        )
                        .foregroundStyle(Color.blue)
                    }
                }
                .chartYScale(domain: .automatic(includesZero: false))
                .chartXAxis {
                    AxisMarks(values: .automatic) { _ in
                        AxisGridLine()
                        AxisValueLabel(format: .dateTime.month().day())
                    }
                }
                .frame(height: 200)
                .padding(.bottom, 8)

                if !motivationalMessage.isEmpty {
                    Text(motivationalMessage)
                        .font(.subheadline)
                        .foregroundColor(.primary)
                        .padding()
                        .background(Color.blue.opacity(0.1))
                        .cornerRadius(8)
                }
            }
        }
        .padding()
        .onAppear {
            loadWeightData()
        }
    }

    private func loadWeightData() {
        isLoading = true

        let request: NSFetchRequest<WorkoutLog> = WorkoutLog.fetchRequest()
        request.predicate = NSPredicate(format: "exerciseName == %@ AND completed == YES", exerciseName)
        request.sortDescriptors = [NSSortDescriptor(keyPath: \WorkoutLog.date, ascending: true)]

        if let logs = try? viewContext.fetch(request) {
            weightData = logs.map { log in
                WeightDataPoint(date: log.date, weight: Int(log.weight))
            }
            generateMotivationalMessage()
        }

        isLoading = false
    }

    private func generateMotivationalMessage() {
        guard weightData.count >= 2 else {
            motivationalMessage = "Complete more workouts to track your progress!"
            return
        }

        let firstWeight = weightData.first?.weight ?? 0
        let currentWeight = weightData.last?.weight ?? 0
        let weightDifference = currentWeight - firstWeight

        if weightDifference > 0 {
            let percentIncrease = Int((Double(weightDifference) / Double(firstWeight)) * 100)
            if percentIncrease >= 20 {
                motivationalMessage = "Amazing progress! You've increased your weight by \(weightDifference) lbs (\(percentIncrease)%)!"
            } else if percentIncrease >= 10 {
                motivationalMessage = "Great job! You've increased your weight by \(weightDifference) lbs (\(percentIncrease)%)!"
            } else {
                motivationalMessage = "You're making progress! Weight increased by \(weightDifference) lbs. Keep it up!"
            }
        } else if weightDifference == 0 {
            motivationalMessage = "You're maintaining consistent weight. Focus on form and consider increasing when ready!"
        } else {
            motivationalMessage = "Your current weight is lower than when you started. Adjust your training as needed and keep pushing!"
        }
    }
}

// Data structure for chart points
struct WeightDataPoint: Identifiable {
    let id = UUID()
    let date: Date
    let weight: Int
}