import SwiftUI

struct InboxView: View {
    @StateObject private var vm = InboxViewModel()
    @State private var showSettings = false
    // Load the inbox only on first appearance. `.task` fires on every
    // appearance (including popping back from a PR detail), so without this
    // guard the landing page re-runs the full network refresh on each back
    // navigation. After the first load, refresh only via pull-to-refresh.
    @State private var didInitialLoad = false

    var body: some View {
        NavigationStack {
            Group {
                if !vm.isConfigured {
                    ContentUnavailableView(
                        "Not configured",
                        systemImage: "key",
                        description: Text("Add your Gitea instance and token in Settings."))
                    .toolbar {
                        ToolbarItem(placement: .primaryAction) { settingsButton }
                    }
                } else if vm.displayedRows.isEmpty && !vm.isLoading {
                    ContentUnavailableView(
                        "No open PRs",
                        systemImage: "tray",
                        description: Text("Nothing to review."))
                } else {
                    List {
                        ForEach(vm.displayedRows) { row in
                            NavigationLink(value: row) {
                                PRRowView(row: row)
                            }
                        }
                    }
                    .refreshable { await vm.load() }
                    .listStyle(.plain)
                }
            }
            .navigationTitle("Pull Requests")
            .navigationBarTitleDisplayMode(.large)
            .toolbar {
                ToolbarItem(placement: .primaryAction) { settingsButton }
            }
            .navigationDestination(for: PRRow.self) { row in
                PRDetailView(repo: row.repo, prNumber: row.pr.number)
            }
            .task {
                // Load only on first appearance; subsequent appearances (e.g.
                // popping back from a PR) reuse the cached list and only
                // refresh when the user pulls down.
                guard !didInitialLoad else { return }
                didInitialLoad = true
                await vm.load()
            }
            .alert("Error", isPresented: .init(
                get: { vm.errorMessage != nil },
                set: { if !$0 { vm.errorMessage = nil } })) {
                Button("OK", role: .cancel) {}
            } message: {
                Text(vm.errorMessage ?? "")
            }
            .sheet(isPresented: $showSettings) {
                SettingsView()
            }
        }
    }

    private var settingsButton: some View {
        Button { showSettings = true } label: {
            Image(systemName: "gearshape")
        }
    }
}

struct PRRowView: View {
    let row: PRRow
    var body: some View {
        HStack(alignment: .top, spacing: 12) {
            VStack(alignment: .leading, spacing: 4) {
                HStack(spacing: 6) {
                    Text("#\(row.pr.number)")
                        .font(.subheadline.weight(.bold))
                        .foregroundColor(.secondary)
                    if row.pr.draft == true {
                        Text("Draft")
                            .font(.caption2)
                            .foregroundColor(.secondary)
                    }
                }
                Text(row.pr.title)
                    .font(.body.weight(.medium))
                    .lineLimit(2)
                Text(row.fullName)
                    .font(.caption)
                    .foregroundColor(.secondary)
            }
            Spacer()
            if let updated = row.pr.updatedAt {
                Text(relative(updated))
                    .font(.caption2)
                    .foregroundColor(.secondary)
            }
        }
        .padding(.vertical, 2)
    }

    private func relative(_ date: Date) -> String {
        let f = RelativeDateTimeFormatter()
        f.unitsStyle = .abbreviated
        return f.localizedString(for: date, relativeTo: Date())
    }
}