import Foundation

nonisolated enum DateSection: Hashable {
    case today
    case yesterday
    case thisWeek
    case thisMonth
    case year(Int)

    var label: String {
        switch self {
        case .today:        return "今天"
        case .yesterday:    return "昨天"
        case .thisWeek:     return "本周"
        case .thisMonth:    return "本月"
        case .year(let y):  return "\(y) 年"
        }
    }

    var sortIndex: Int {
        switch self {
        case .today:       return 0
        case .yesterday:   return 1
        case .thisWeek:    return 2
        case .thisMonth:   return 3
        case .year(let y): return 10_000 - y
        }
    }
}

enum TimelineGrouping {
    static func section(for date: Date,
                        now: Date = .now,
                        calendar: Calendar = .current) -> DateSection {
        if calendar.isDate(date, inSameDayAs: now) { return .today }
        if let yesterday = calendar.date(byAdding: .day, value: -1, to: now),
           calendar.isDate(date, inSameDayAs: yesterday) {
            return .yesterday
        }
        if calendar.isDate(date, equalTo: now, toGranularity: .weekOfYear) {
            return .thisWeek
        }
        if calendar.isDate(date, equalTo: now, toGranularity: .month) {
            return .thisMonth
        }
        let year = calendar.component(.year, from: date)
        return .year(year)
    }

    static func group(_ entries: [TimelineEntry],
                      now: Date = .now,
                      calendar: Calendar = .current)
    -> [(section: DateSection, items: [TimelineEntry])] {
        var buckets: [DateSection: [TimelineEntry]] = [:]
        for entry in entries {
            let key = section(for: entry.date, now: now, calendar: calendar)
            buckets[key, default: []].append(entry)
        }
        return buckets
            .map { ($0.key, $0.value.sorted { $0.date > $1.date }) }
            .sorted { $0.0.sortIndex < $1.0.sortIndex }
    }
}

func formatDuration(_ interval: TimeInterval) -> String {
    let totalMinutes = Int(max(0, interval) / 60)
    let days = totalMinutes / (60 * 24)
    let hours = (totalMinutes % (60 * 24)) / 60
    let minutes = totalMinutes % 60

    if days > 0 && hours > 0 { return "\(days) 天 \(hours) 小时" }
    if days > 0 { return "\(days) 天" }
    if hours > 0 && minutes > 0 { return "\(hours) 小时 \(minutes) 分" }
    if hours > 0 { return "\(hours) 小时" }
    if minutes > 0 { return "\(minutes) 分钟" }
    return "刚刚"
}