//
//  ActivityLog.swift
//  WorkoutsPlus
//
//  Created by Felix Förtsch on 09.09.24.
//
// https://www.artemnovichkov.com/blog/github-contribution-graph-swift-charts
// https://github.com/artemnovichkov/awesome-swift-charts

import SwiftUI
import Charts

struct ActivityLog: View {
		@State var activities: [Activity] = Activity.generate()
		
		var body: some View {
				Chart(activities) { contribution in
						RectangleMark(
								xStart: .value("Start week", contribution.date, unit: .weekOfYear),
								xEnd: .value("End week", contribution.date, unit: .weekOfYear),
								yStart: .value("Start weekday", weekday(for: contribution.date)),
								yEnd: .value("End weekday", weekday(for: contribution.date) + 1)
						)
						.clipShape(RoundedRectangle(cornerRadius: 4).inset(by: 2))
						.foregroundStyle(by: .value("Count", contribution.count))
				}
				.chartPlotStyle { content in
						content
								.aspectRatio(aspectRatio, contentMode: .fit)
				}
				.chartForegroundStyleScale(range: Gradient(colors: colors))
				.chartXAxis {
						AxisMarks(position: .top, values: .stride(by: .month)) {
								AxisValueLabel(format: .dateTime.month())
										.foregroundStyle(Color(.label))
						}
				}
				.chartYAxis {
						AxisMarks(position: .leading, values: [1, 3, 5]) { value in
								if let value = value.as(Int.self) {
										AxisValueLabel {
												// Symbols from Calendar.current starting with Monday
//												Text(shortWeekdaySymbols[value - 1])
										}
										.foregroundStyle(Color(.label))
								}
						}
				}
				.chartYScale(domain: .automatic(includesZero: false, reversed: true))
				.chartLegend {
						HStack(spacing: 4) {
								Text("Less")
								ForEach(legendColors, id: \.self) { color in
										color
												.frame(width: 10, height: 10)
												.cornerRadius(2)
								}
								Text("More")
						}
						.padding(4)
						.foregroundStyle(Color(.label))
						.font(.caption2)
				}
				
				
		}
		
		private func weekday(for date: Date) -> Int {
				let weekday = Calendar.current.component(.weekday, from: date)
				let adjustedWeekday = (weekday == 1) ? 7 : (weekday - 1)
				return adjustedWeekday
		}
		
		private var aspectRatio: Double {
				if activities.isEmpty {
						return 1
				}
				let firstDate = activities.first!.date
				let lastDate = activities.last!.date
				let firstWeek = Calendar.current.component(.weekOfYear, from: firstDate)
				let lastWeek = Calendar.current.component(.weekOfYear, from: lastDate)
				return Double(lastWeek - firstWeek + 1) / 7
		}
		
		private var colors: [Color] {
				(0...10).map { index in
						if index == 0 {
								return Color(.systemGray5)
						}
						return Color(.systemGreen).opacity(Double(index) / 10)
				}
		}
		
		private var legendColors: [Color] {
				Array(stride(from: 0, to: colors.count, by: 2).map { colors[$0] })
		}
}

#Preview {
		ActivityLog()
}

struct Activity: Identifiable {
		
		let date: Date
		let count: Int
		
		var id: Date {
				date
		}
}

extension Activity {
		
		static func generate() -> [Activity] {
				var contributions: [Activity] = []
				let toDate = Date.now
				let fromDate = Calendar.current.date(byAdding: .day, value: -60, to: toDate)!
				
				var currentDate = fromDate
				while currentDate <= toDate {
						let contribution = Activity(date: currentDate, count: .random(in: 0...10))
						contributions.append(contribution)
						currentDate = Calendar.current.date(byAdding: .day, value: 1, to: currentDate)!
				}
				
				return contributions
		}
}