import SwiftUI
import EventKit

/// The "Routes (multi-source)" panel — extracted from ContentView so the
/// route list/editor is its own small, native-feeling view instead of one
/// piece of a 2000-line file. Owns no persisted state itself: `routes` is a
/// binding into ContentView's own @State (which still owns saving it to
/// UserDefaults), and everything else here is read-only context passed down.
struct RoutesSectionView: View {
    @Binding var routes: [Route]
    let calendars: [EKCalendar]
    let isRunning: Bool
    let titlePrefix: String
    let placeholderTitle: String
    let canAddRoute: Bool
    let onAddRoute: () -> Void

    @State private var expandedRouteID: UUID?

    private static let intFormatter: NumberFormatter = {
        let f = NumberFormatter()
        f.minimum = 0
        f.maximumFractionDigits = 0
        return f
    }()

    private func labelForCalendar(id: String) -> String {
        calendars.first(where: { $0.calendarIdentifier == id }).map(calLabel) ?? id
    }

    var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            HStack {
                Text("Routes (multi-source)")
                    .font(.headline)
                Spacer()
                Button("Add from current selection", action: onAddRoute)
                    .disabled(isRunning || !canAddRoute)
                    .buttonStyle(.borderedProminent)
                Button("Clear") { routes.removeAll() }
                    .disabled(isRunning || routes.isEmpty)
                    .buttonStyle(.bordered)
            }
            if routes.isEmpty {
                Text("No routes yet. Pick a Source and Targets above, then click ‘Add from current selection’.")
                    .foregroundStyle(.secondary)
                    .padding(.vertical, 8)
            } else {
                LazyVStack(spacing: 10) {
                    ForEach($routes, id: \.id) { routeBinding in
                        routeCard(for: routeBinding)
                    }
                }
            }
        }
    }

    @ViewBuilder
    private func routeCard(for routeBinding: Binding<Route>) -> some View {
        let route = routeBinding.wrappedValue
        let isExpanded = expandedRouteID == route.id
        VStack(alignment: .leading, spacing: 10) {
            Button {
                expandedRouteID = isExpanded ? nil : route.id
            } label: {
                HStack(alignment: .top, spacing: 10) {
                    Image(systemName: "chevron.right")
                        .font(.caption.weight(.semibold))
                        .foregroundStyle(.secondary)
                        .rotationEffect(.degrees(isExpanded ? 90 : 0))
                        .frame(width: 12)
                        .padding(.top, 3)
                    VStack(alignment: .leading, spacing: 8) {
                        sourceSummaryView(for: route)
                        targetSummaryView(for: route)
                    }
                    Spacer(minLength: 12)
                }
                .contentShape(Rectangle())
            }
            .buttonStyle(.plain)

            if isExpanded {
                Divider()

                Toggle("Private", isOn: routeBinding.privacy)
                    .help("If ON, mirror as ‘\(titlePrefix)\(placeholderTitle)’ with no notes. If OFF, mirror source title (and optionally notes).")
                Toggle("Copy description", isOn: routeBinding.copyNotes)
                    .disabled(isRunning || route.privacy)
                    .help("If ON and Private is OFF, copy the source event’s notes/description into the placeholder.")
                Toggle("Sync reminders", isOn: routeBinding.syncReminders)
                    .disabled(isRunning)
                    .help("If ON, copy the source event’s reminders/alarms into the placeholder.")
                Toggle("Mirror all-day events for this route", isOn: routeBinding.allDay)
                    .disabled(isRunning)
                    .help("Mirror all-day events for this source.")

                HStack(spacing: 16) {
                    mergeGapField(for: routeBinding)
                    overlapPicker(for: routeBinding)
                    Spacer(minLength: 0)
                    Button(role: .destructive) {
                        routes.removeAll { $0.id == route.id }
                    } label: { Text("Remove Route") }
                }
            }
        }
        .padding(12)
        .background(
            RoundedRectangle(cornerRadius: 12, style: .continuous)
                .fill(Color(nsColor: .controlBackgroundColor))
        )
        .overlay(
            RoundedRectangle(cornerRadius: 12, style: .continuous)
                .stroke(Color.primary.opacity(0.25), lineWidth: 1.1)
        )
    }

    @ViewBuilder
    private func sourceSummaryView(for route: Route) -> some View {
        VStack(alignment: .leading, spacing: 3) {
            Text("Source")
                .font(.caption)
                .foregroundStyle(.secondary)
            if let sCal = calendars.first(where: { $0.calendarIdentifier == route.sourceID }) {
                HStack(spacing: 6) {
                    Circle().fill(calColor(sCal)).frame(width: 10, height: 10)
                    Text(calLabel(sCal))
                        .fontWeight(.semibold)
                }
            } else {
                Text(labelForCalendar(id: route.sourceID))
                    .fontWeight(.semibold)
            }
        }
    }

    @ViewBuilder
    private func targetSummaryView(for route: Route) -> some View {
        VStack(alignment: .leading, spacing: 6) {
            Text("Targets")
                .font(.caption)
                .foregroundStyle(.secondary)
            ScrollView(.horizontal, showsIndicators: false) {
                HStack(spacing: 8) {
                    ForEach(route.targetIDs.sorted(by: <), id: \.self) { tid in
                        if let tCal = calendars.first(where: { $0.calendarIdentifier == tid }) {
                            HStack(spacing: 6) {
                                Circle().fill(calColor(tCal)).frame(width: 9, height: 9)
                                Text(calLabel(tCal))
                            }
                            .padding(.horizontal, 10)
                            .padding(.vertical, 5)
                            .background(
                                RoundedRectangle(cornerRadius: 999, style: .continuous)
                                    .fill(Color.primary.opacity(0.1))
                            )
                        } else {
                            Text(labelForCalendar(id: tid))
                                .padding(.horizontal, 10)
                                .padding(.vertical, 5)
                                .background(
                                    RoundedRectangle(cornerRadius: 999, style: .continuous)
                                        .fill(Color.primary.opacity(0.1))
                                )
                        }
                    }
                }
            }
        }
    }

    @ViewBuilder
    private func mergeGapField(for routeBinding: Binding<Route>) -> some View {
        HStack(spacing: 8) {
            Text("Merge gap")
            TextField("0", value: routeBinding.mergeGapHours, formatter: Self.intFormatter)
                .frame(width: 56)
                .disabled(isRunning)
                .help("Merge adjacent source events separated by ≤ this many hours (e.g., flight legs). 0 = no merge.")
            Text("h").foregroundStyle(.secondary)
        }
        .font(.subheadline)
    }

    @ViewBuilder
    private func overlapPicker(for routeBinding: Binding<Route>) -> some View {
        HStack(spacing: 8) {
            Text("Overlap")
            Picker("Overlap", selection: routeBinding.overlap) {
                ForEach(OverlapMode.allCases) { mode in
                    Text(mode.rawValue).tag(mode)
                }
            }
            .frame(width: 170)
            .help("allow = always place; skipCovered = skip if target already has a block covering the time; fillGaps = only fill uncovered gaps within the source block.")
        }
        .font(.subheadline)
    }
}