import SwiftUI

/// Paste a token, name the instance, done. There is no browser flow and no
/// password in the app: tokens are minted on the instance's web settings
/// page or over SSH.
struct SignInView: View {

    @Environment(SessionStore.self) private var session

    @State private var instanceURL = "gitbay.org"
    @State private var token = ""
    @State private var errorMessage: String?
    @State private var signingIn = false
    @FocusState private var tokenFieldFocused: Bool

    var body: some View {
        Form {
            if let notice = session.signedOutMessage {
                Section {
                    Label(notice, systemImage: "key.slash")
                        .foregroundStyle(.secondary)
                }
            }

            Section("Instance") {
                TextField("gitbay.org", text: $instanceURL)
                    .textContentType(.URL)
                    .keyboardType(.URL)
                    .autocorrectionDisabled()
                    .textInputAutocapitalization(.never)
            }

            Section {
                SecureField("Paste a token", text: $token)
                    .autocorrectionDisabled()
                    .textInputAutocapitalization(.never)
                    .focused($tokenFieldFocused)
                    .submitLabel(.go)
                    .onSubmit { signIn() }
                    .privacySensitive()
            } header: {
                Text("Token")
            } footer: {
                VStack(alignment: .leading, spacing: 8) {
                    if let tokenPage = (try? GitbayInstance(url: instanceURL))?.tokenPageURL {
                        Link(destination: tokenPage) {
                            Text("Create one with full scope under Settings → API tokens")
                                .multilineTextAlignment(.leading)
                                .frame(maxWidth: .infinity, alignment: .leading)
                        }
                        Text("Or over SSH on a machine that has your key:")
                    } else {
                        Text("Create one over SSH on a machine that has your key:")
                    }
                    Text(verbatim: "gitbay auth token create --name iphone --scope full --ttl 90d")
                        .font(.gbMono(.caption))
                        .textSelection(.enabled)
                    Text("Full scope can comment and merge, and on an admin account, administer the instance. A read-only token cannot comment or merge.")
                }
            }

            if let errorMessage {
                Section {
                    GBNotice(errorMessage)
                }
            }

            Section {
                Button {
                    signIn()
                } label: {
                    if signingIn {
                        ProgressView()
                            .frame(maxWidth: .infinity)
                    } else {
                        Text("Sign In")
                            .frame(maxWidth: .infinity)
                    }
                }
                .disabled(signingIn || token.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
            }
        }
        .navigationTitle("Sign in to gitbay")
        .onAppear { tokenFieldFocused = true }
    }

    private func signIn() {
        signingIn = true
        errorMessage = nil
        Task {
            defer { signingIn = false }
            do {
                try await session.signIn(instanceURL: instanceURL, token: token)
                token = ""
            } catch let error as GitbayError {
                errorMessage = signInMessage(for: error)
            } catch let error as GitbayInstance.InvalidURL {
                errorMessage = error.errorDescription
            } catch {
                errorMessage = "Something went wrong. Please try again."
            }
        }
    }

    /// Sign-in is the one place a 401 means "that token", not "your session".
    private func signInMessage(for error: GitbayError) -> String {
        if error.requiresReauthentication {
            return "That token was not accepted. Check it was pasted whole and has not expired."
        }
        return error.userFacingMessage
    }
}

#Preview {
    NavigationStack {
        SignInView()
    }
    .environment(SessionStore())
}