import SwiftUI

extension ScheduleChanges: Identifiable {
    var id: String { "\(document)|\(group)|\(at.timeIntervalSince1970)" }
}

/**
 * The overview's card after the university republished the group's document: how many lessons
 * changed, "Показать" for the list, and a close button. Both mark the record as seen.
 */
struct ChangesCard: View {
    var record: ScheduleChanges
    var onShow: () -> Void
    var onClose: () -> Void

    var body: some View {
        HStack(alignment: .top, spacing: 14) {
            Image(systemName: "arrow.triangle.2.circlepath.doc.on.clipboard")
                .font(.body.weight(.semibold))
                .foregroundStyle(Color.onBrand)
                .frame(width: 40, height: 40)
                .background(Color.brand, in: .circle)
                .accessibilityHidden(true)
            VStack(alignment: .leading, spacing: 4) {
                Text("Расписание обновлено · \(changesLabel(record.count))").font(.headline)
                Text("Для \(record.group)" + (fileDateLabel(record.to).map { " · файл от \($0)" } ?? ""))
                    .font(.subheadline).foregroundStyle(.secondary)
                Button("Показать", action: onShow)
                    .buttonStyle(.glassProminent)
                    .padding(.top, 6)
            }
            .frame(maxWidth: .infinity, alignment: .leading)
            Button("Скрыть сообщение об изменениях", systemImage: "xmark", action: onClose)
                .labelStyle(.iconOnly)
                .buttonStyle(.glass)
                .buttonBorderShape(.circle)
        }
        .card(padding: 18)
    }
}

/// The list behind the card: changed, added and removed lessons, as in the PWA.
struct ChangesSheet: View {
    @Environment(\.dismiss) private var dismiss
    var record: ScheduleChanges

    var body: some View {
        NavigationStack {
            List {
                Section {
                    Text("\(record.group) · \(record.name.replacingOccurrences(of: #"\.docx?$"#, with: "", options: [.regularExpression, .caseInsensitive]))"
                        + (fileDateLabel(record.to).map { " · файл от \($0)" } ?? "")
                        + ". Сравнение с прошлой версией, сохранённой на этом устройстве.")
                        .font(.subheadline).foregroundStyle(.secondary)
                }
                if !record.changed.isEmpty {
                    Section("Изменено · \(record.changed.count)") {
                        ForEach(record.changed, id: \.self) { change in
                            VStack(alignment: .leading, spacing: 4) {
                                when(change.after)
                                Text(change.after.lesson.subject).font(.headline)
                                ForEach(change.fields, id: \.self) { f in
                                    (Text("\(f.label): ").foregroundStyle(.secondary)
                                        + Text(f.from).strikethrough().foregroundStyle(.secondary)
                                        + Text("  →  ").foregroundStyle(.secondary)
                                        + Text(f.to))
                                        .font(.subheadline)
                                        .accessibilityLabel("\(f.label): было \(f.from), стало \(f.to)")
                                }
                                if change.fields.isEmpty {
                                    Text("Изменился текст ячейки Word").font(.subheadline).foregroundStyle(.secondary)
                                }
                            }
                            .padding(.vertical, 2)
                        }
                    }
                }
                if !record.added.isEmpty {
                    Section("Добавлено · \(record.added.count)") {
                        ForEach(record.added, id: \.self) { row in
                            item(row, details: [row.lesson.type, row.lesson.teachers.joined(separator: ", "),
                                                withPlace(row.lesson.rooms.map { "ауд. \($0)" }.joined(separator: ", "), row.lesson.place) ?? "", row.lesson.condition])
                        }
                    }
                }
                if !record.removed.isEmpty {
                    Section("Удалено · \(record.removed.count)") {
                        ForEach(record.removed, id: \.self) { row in
                            item(row, removed: true, details: [row.lesson.type, row.lesson.condition])
                        }
                    }
                }
                Section {} footer: { Text("Сверяйтесь с документом Word: при сомнениях он главнее.") }
            }
            .navigationTitle("Изменения")
            .toolbar { ToolbarItem(placement: .confirmationAction) { Button("Готово", systemImage: "checkmark") { dismiss() } } }
        }
    }

    private func when(_ row: ChangedLesson) -> some View {
        let day = row.date.flatMap { CivilDate($0) }.map { "\($0.shortWeekday), \($0.longLabel)" } ?? dayName(row.day)
        return Text(day + " · " + row.lesson.start).font(.subheadline.weight(.semibold)).foregroundStyle(Color.brand)
    }

    private func item(_ row: ChangedLesson, removed: Bool = false, details: [String]) -> some View {
        VStack(alignment: .leading, spacing: 4) {
            when(row).foregroundStyle(removed ? .secondary : Color.brand)
            Text(row.lesson.subject).font(.headline).strikethrough(removed).foregroundStyle(removed ? .secondary : .primary)
            let text = details.filter { !$0.trimmed.isEmpty }.joined(separator: " · ")
            if !text.isEmpty { Text(text).font(.subheadline).foregroundStyle(.secondary) }
        }
        .padding(.vertical, 2)
    }
}