import SwiftUI

struct SettingsProviderView: View {
  @EnvironmentObject var settings: SettingsManager
  @State private var showingCustomBooruSheet = false
  @State private var newDomain: String = ""
  @State private var newFlavor: BooruProviderFlavor = .danbooru
  @State private var domainError: String?

  var body: some View {
    Group {
      Picker("Provider", selection: $settings.preferredBooru) {
        ForEach(BooruProvider.allCases, id: \.self) { type in
          Text(type.rawValue).tag(type)
        }

        ForEach(settings.customProviders, id: \.id) { provider in
          Text(provider.domain)
            .tag(BooruProvider.custom(provider))
        }
      }

      Button("Add Custom Provider") {
        showingCustomBooruSheet = true
      }
      #if os(macOS)
        .frame(maxWidth: .infinity, alignment: .trailing)
      #endif
      .sheet(isPresented: $showingCustomBooruSheet) {
        Form {
          TextField("Domain", text: $newDomain)
            .autocorrectionDisabled(true)

          Picker("Flavor", selection: $newFlavor) {
            ForEach(BooruProviderFlavor.allCases, id: \.self) { flavor in
              Text(flavor.rawValue).tag(flavor)
            }
          }
        }
        #if os(macOS)
          .formStyle(.grouped)
        #endif
        .toolbar {
          ToolbarItem(placement: .cancellationAction) {
            Button("Cancel") {
              showingCustomBooruSheet = false
              resetForm()
            }
          }

          ToolbarItem(placement: .confirmationAction) {
            Button("Add") {
              if validateDomain() {
                addCustomProvider()
                showingCustomBooruSheet = false
              }
            }
            .disabled(newDomain.isEmpty || domainError != nil)
          }
        }
      }

      if case .custom(let provider) = settings.preferredBooru {
        removeCustomProviderButtonContent(provider)
      }

      Button("Remove All Custom Providers") {
        if case .custom = settings.preferredBooru {
          settings.preferredBooru = .safebooru
        }

        if !settings.customProviders.isEmpty {
          settings.customProviders.removeAll()
        }
      }
      #if os(macOS)
        .frame(maxWidth: .infinity, alignment: .trailing)
      #endif
    }
    .alert(
      "Invalid Domain",
      isPresented: Binding(
        get: { domainError != nil },
        set: { if !$0 { domainError = nil } }
      )
    ) {
      Button("OK", role: .cancel) { () }
    } message: {
      Text(domainError ?? "An unknown error occurred while validating the domain.")
    }
  }

  private func addCustomProvider() {
    let customProvider = BooruProviderCustom(
      domain: newDomain.lowercased(),
      flavor: newFlavor
    )

    settings.customProviders.append(customProvider)
    resetForm()
  }

  private func resetForm() {
    newDomain = ""
    newFlavor = .danbooru
    domainError = nil
  }

  @discardableResult
  private func validateDomain() -> Bool {
    guard !newDomain.isEmpty else {
      domainError = nil

      return false
    }

    let domain = newDomain.lowercased().trimmingCharacters(in: .whitespaces)
    let domainRegex =
      "^[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?(?:\\.[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?)*\\.[a-z]{2,}$"

    guard NSPredicate(format: "SELF MATCHES %@", domainRegex).evaluate(with: domain) else {
      domainError = "Please enter a valid domain name, such as yande.re."

      return false
    }

    guard !domain.contains("://"), !domain.contains("/"), !domain.contains("?") else {
      domainError = "Only enter the domain name—leave out 'http://' or extra details."

      return false
    }

    guard domain.count <= 253 else {  // RFC 1035
      domainError = "This domain name is too long. It must be 253 characters or fewer."

      return false
    }

    let labels = domain.split(separator: ".")

    guard labels.allSatisfy({ $0.count <= 63 }) else {
      domainError = "Each section of the domain name must be 63 characters or fewer."

      return false
    }

    domainError = nil

    return true
  }

  private func removeCustomProviderButtonContent(_ provider: BooruProviderCustom) -> some View {
    Button("Remove Custom Provider") {
      settings.customProviders.removeAll { $0.id == provider.id }
      settings.preferredBooru = .safebooru
    }
    .disabled(!settings.customProviders.contains { $0.id == provider.id })
    #if os(macOS)
      .frame(maxWidth: .infinity, alignment: .trailing)
    #endif
  }
}