import RastrilloApple
import SwiftUI

struct EventEditor: View {
  @ObservedObject var model: CalendarModel
  let client: NativeHTTP
  @State var event: CalendarEvent
  @State private var start: Date
  @State private var end: Date
  @State private var scheduleChanged = false
  @State private var wallClockFields: Bool
  @State private var saving = false
  @State private var error = ""
  @Environment(\.dismiss) private var dismiss

  init(model: CalendarModel, client: NativeHTTP, event: CalendarEvent) {
    self.model = model; self.client = client
    _event = State(initialValue: event)
    let parsedStart = model.parse(event.start_local, allDay: event.all_day, zone: event.tz)
    let parsedEnd = model.parse(event.end_local, allDay: event.all_day, zone: event.tz)
    _wallClockFields = State(initialValue: parsedStart == nil || parsedEnd == nil)
    _start = State(initialValue: parsedStart ?? model.date)
    _end = State(initialValue: parsedEnd ?? model.date)
  }
  var body: some View {
    NavigationStack {
      Form {
        Section {
          TextField("Title", text: $event.title).accessibilityIdentifier("eventTitle")
          TextField("Location", text: $event.location)
          if event.id == 0 {
            Picker("Calendar", selection: $event.calendar_id) {
              ForEach(model.calendars.filter(\.writable)) { Text($0.name).tag($0.id) }
            }
          }
        }
        Section("When") {
          Toggle("All day", isOn: $event.all_day).disabled(wallClockFields)
          if wallClockFields {
            TextField("Starts", text: $event.start_local)
            TextField("Ends", text: $event.end_local)
            Text("This event uses a local time during a clock change. Its original local dates are preserved; edit them as YYYY-MM-DDTHH:mm.").font(.footnote).foregroundStyle(.secondary)
          } else {
          DatePicker("Starts", selection: $start, displayedComponents: event.all_day ? [.date] : [.date, .hourAndMinute])
          DatePicker(event.all_day ? "Ends before" : "Ends", selection: $end, displayedComponents: event.all_day ? [.date] : [.date, .hourAndMinute])
          }
          LabeledContent("Time zone", value: event.tz)
          if event.all_day { Text("The end date is the first day after this event.").font(.footnote).foregroundStyle(.secondary) }
        }
        Section("Notes") { TextEditor(text: $event.notes).frame(minHeight: 100).accessibilityLabel("Notes") }
        if !error.isEmpty { Section { Text(error).foregroundStyle(.red) } }
      }.formStyle(.grouped).environment(\.timeZone, TimeZone(identifier: event.tz) ?? .gmt)
        .navigationTitle(event.id == 0 ? "New event" : "Edit event")
        .toolbar {
          ToolbarItem(placement: .cancellationAction) { Button("Cancel") { dismiss() }.disabled(saving) }
          ToolbarItem(placement: .confirmationAction) {
            Button(saving ? "Saving…" : "Save") {
              if scheduleChanged && !wallClockFields {
              event.start_local = model.format(start, allDay: event.all_day, zone: event.tz)
              event.end_local = model.format(end, allDay: event.all_day, zone: event.tz)
              }
              saving = true
              Task {
                do { try await model.save(event, client: client); dismiss() }
                catch { self.error = error.localizedDescription; saving = false }
              }
            }.disabled(saving || event.title.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty || (!wallClockFields && end <= start))
          }
        }
    }
    #if os(macOS)
      .frame(width: 500, height: 560)
    #endif
    .onChange(of: start) { _, _ in scheduleChanged = true }
    .onChange(of: end) { _, _ in scheduleChanged = true }
    .onChange(of: event.all_day) { _, allDay in
      scheduleChanged = true
      if allDay && !wallClockFields {
        var calendar = Calendar(identifier: .gregorian)
        calendar.timeZone = TimeZone(identifier: event.tz) ?? .gmt
        start = calendar.startOfDay(for: start)
        end = max(calendar.startOfDay(for: end), calendar.date(byAdding: .day, value: 1, to: start)!)
      }
    }
    .interactiveDismissDisabled(saving)
  }
}