import UIKit
import SwiftUI
import Foundation

enum WorkingCopyGuard {
    enum GuardError: LocalizedError {
        case notInstalled
        case apiKeyMissing
        case repoNameMissing(String)

        var errorDescription: String? {
            switch self {
            case .notInstalled:            return "Working Copy is not installed."
            case .apiKeyMissing:           return "Working Copy API key not set. Go to Settings → Working Copy."
            case .repoNameMissing(let p):  return "No Working Copy repo name set for '\(p)'."
            }
        }
        var actionLabel: String {
            switch self {
            case .notInstalled:   return "App Store"
            default:              return "Open Settings"
            }
        }
    }

    static func validate(projectName: String, requiresApiKey: Bool = true) throws {
        guard UIApplication.shared.canOpenURL(URL(string: "working-copy://")!) else {
            throw GuardError.notInstalled
        }
        if requiresApiKey {
            let key = UserDefaults.standard.string(forKey: "workingCopyAPIKey") ?? ""
            guard !key.trimmingCharacters(in: .whitespaces).isEmpty else {
                throw GuardError.apiKeyMissing
            }
        }
        let repoName = UserDefaults.standard.string(forKey: "wc_repo_for_\(projectName)") ?? ""
        guard !repoName.trimmingCharacters(in: .whitespaces).isEmpty else {
            throw GuardError.repoNameMissing(projectName)
        }
    }
}

struct WorkingCopyErrorBanner: ViewModifier {
    @Binding var error: WorkingCopyGuard.GuardError?
    func body(content: Content) -> some View {
        content.overlay(alignment: .top) {
            if let err = error {
                HStack(spacing: 10) {
                    Image(systemName: "exclamationmark.triangle.fill").foregroundStyle(.orange)
                    Text(err.localizedDescription ?? "").font(.subheadline).lineLimit(2)
                    Spacer()
                    Button(err.actionLabel) { handleAction(for: err) }.buttonStyle(.bordered).controlSize(.small)
                    Button { withAnimation { self.error = nil } }
                        label: { Image(systemName: "xmark").font(.caption.bold()) }
                        .buttonStyle(.plain).foregroundStyle(.secondary)
                }
                .padding(.horizontal, 14).padding(.vertical, 10)
                .background(.regularMaterial)
                .transition(.move(edge: .top).combined(with: .opacity))
            }
        }
        .animation(.spring(response: 0.3), value: error != nil)
    }

    private func handleAction(for err: WorkingCopyGuard.GuardError) {
        switch err {
        case .notInstalled:
            UIApplication.shared.open(URL(string: "https://apps.apple.com/app/working-copy-git-client/id896694807")!)
        default:
            NotificationCenter.default.post(name: .openSettings, object: nil)
        }
        self.error = nil
    }
}

extension View {
    func workingCopyErrorBanner(_ error: Binding<WorkingCopyGuard.GuardError?>) -> some View {
        modifier(WorkingCopyErrorBanner(error: error))
    }
}