import SwiftUI

/// The main presence screen.
///
/// This is the emotional core of the app. A large, tactile "I am here"
/// toggle that makes being present feel like an intentional act — not a
/// passive background process. Below it, the live feed of silhouettes.
struct PresenceView: View {
    @EnvironmentObject private var vm: PresenceViewModel
    @EnvironmentObject private var revealFlow: RevealFlow
    @State private var showReveal = false

    var body: some View {
        NavigationStack {
            ScrollView {
                VStack(spacing: 24) {
                    presenceToggle
                    radiusPicker
                    encounterFeed
                }
                .padding()
            }
            .navigationTitle("Proximity")
            .toolbar {
                #if DEBUG
                ToolbarItem(placement: .topBarLeading) {
                    NavigationLink {
                        DebugMenu()
                    } label: {
                        Image(systemName: "hammer")
                    }
                }
                #endif
            }
        }
        .onChange(of: revealFlow.phase) { _, phase in
            if case .mutual = phase {
                showReveal = true
            }
        }
        .fullScreenCover(isPresented: $showReveal) {
            RevealView()
                .environmentObject(revealFlow)
        }
    }

    // MARK: - The presence toggle

    private var presenceToggle: some View {
        Button(action: vm.togglePresence) {
            ZStack {
                Circle()
                    .fill(vm.isPresent ? Color.green : Color.gray.opacity(0.2))
                    .frame(width: 200, height: 200)
                    .overlay(
                        Circle()
                            .stroke(vm.isPresent ? Color.green : Color.gray,
                                    lineWidth: 4)
                    )

                VStack(spacing: 8) {
                    Image(systemName: vm.isPresent
                          ? "dot.radiowaves.left.and.right"
                          : "person.crop.circle.dashed")
                        .font(.system(size: 56))
                    Text(vm.isPresent ? "I'm Here" : "Tap to be Present")
                        .font(.headline)
                }
                .foregroundColor(vm.isPresent ? .white : .secondary)
            }
            .scaleEffect(vm.isPresent ? 1.0 : 0.98)
            .animation(.spring(response: 0.4, dampingFraction: 0.6),
                       value: vm.isPresent)
        }
        .buttonStyle(.plain)
        .accessibilityLabel(vm.isPresent ? "You are present. Tap to go offline."
                                         : "Go present")
    }

    // MARK: - Radius picker

    private var radiusPicker: some View {
        VStack(alignment: .leading, spacing: 8) {
            Text("How far are you open to?")
                .font(.subheadline)
                .foregroundColor(.secondary)

            Picker("Radius", selection: $vm.radiusTier) {
                ForEach(DistanceTier.allCases) { tier in
                    Text(tier.title).tag(tier)
                }
            }
            .pickerStyle(.segmented)

            Text(vm.radiusTier.subtitle)
                .font(.caption)
                .foregroundColor(.secondary)
        }
    }

    // MARK: - Encounter feed

    private var encounterFeed: some View {
        VStack(alignment: .leading, spacing: 12) {
            HStack {
                Text("People you've passed")
                    .font(.headline)
                Spacer()
                if let last = vm.lastScan {
                    Text("last scan \(last, style: .time)")
                        .font(.caption)
                        .foregroundColor(.secondary)
                }
            }

            if vm.encounters.isEmpty {
                emptyState
            } else {
                ForEach(vm.encounters) { encounter in
                    SilhouetteRow(encounter: encounter) {
                        // Tap a silhouette → consider it → wave.
                        revealFlow.consider(encounter)
                        Task { await revealFlow.wave() }
                    }
                }
            }
        }
    }

    private var emptyState: some View {
        VStack(spacing: 12) {
            Image(systemName: "eye.slash")
                .font(.system(size: 40))
                .foregroundColor(.secondary)
            Text(vm.isPresent
                 ? "Looking for people near you…"
                 : "Go present to start seeing people.")
                .multilineTextAlignment(.center)
                .foregroundColor(.secondary)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 40)
    }
}