barChart.swift

import SwiftUI

extension HabitCard {
    var barChart: some View {
        Capsule()
            .fill(.quaternary)
            .overlay {
                GeometryReader { geometry in
                    let height = geometry.size.height
                    Capsule()
                        .fill(habit.color.gradient)
                        .background { targetBounceFiller(for: height) }
                        .offset(y: targetOffset(for: height))
                        .shadow(color: .black.opacity(0.07), radius: 2, x: 0, y: -2)
                        .background { overflowFiller(for: height)}
                        .clipShape(.capsule)
                        .padding(3)
                        .shadow(color: glowColor, radius: 4, x: 0, y: 6)
                        .animation(.bouncy(extraBounce: 0.1), value: progress)
                }
            }
            .frame(width: barChartWidth)
    }
}

extension HabitCard {
    func targetOffset(for height: CGFloat) -> CGFloat {
        switch progress {
            case  ...0: height
            case 0..<1: height * (1 - progress) - 12
            case     1: 0
            case  1...: height * (1 - (1 / progress)) - 12
            default   : height
        }
    }
    
    func overflowOffset(for height: CGFloat) -> CGFloat {
        progress > 1 ? 0 : targetOffset(for: height) + barChartWidth / 2
    }
    
    var glowColor: Color {
        switch colorScheme {
            case .light: habit.color.opacity(0.1)
            case .dark: habit.color.opacity(0.05)
            @unknown default: habit.color.opacity(0.1)
        }
    }
}

extension HabitCard {
    func targetBounceFiller(for height: CGFloat) -> some View {
        Rectangle()
            .fill(habit.color.gradient)
            .frame(height: height / 2 + barChartWidth / 2)
            .frame(maxHeight: .infinity, alignment: .bottom)
            .offset(y: barChartWidth / 2)
    }
    
    func overflowFiller(for height: CGFloat) -> some View {
        Capsule()
            .fill(habit.color.gradient)
            .brightness(-0.035)
            .rotationEffect(.degrees(180))
            .offset(y: overflowOffset(for: height))
            .animation(.bouncy(duration: 0.85, extraBounce: 0.2), value: progress)
    }
}