Core Module

public enum AppError: Error, Equatable, CustomStringConvertible, LocalizedError, Sendable {
    case network(code: Int, message: String?)
    case decoding
    case unauthorized
    case rateLimited(retryAfter: TimeInterval?)
    // Additional cases omitted for brevity.

    // User-friendly messages
    public var userMessage: String {
        switch self {
        case .network(_, let message) where message?.localizedCaseInsensitiveContains("offline") == true:
            return "You're offline. Please check your internet connection."
        case .network(_, let message) where message?.localizedCaseInsensitiveContains("timeout") == true:
            return "Request timed out. Please try again."
        case .unauthorized:
            return "Please sign in to continue."
        case .rateLimited:
            return "Too many requests. Please wait a moment and try again."
        // ... handles all cases with actionable messages
        }
    }
}

// From SwiftAIBoilerplatePro/AppShell/SignInView.swift
func signInWithApple() async {
    do {
        _ = try await authClient.signInWithApple()
        errorMessage = nil
    } catch {
        let appError = AppError.from(error)  // Auto-maps to AppError
        errorMessage = appError.userMessage  // Show friendly message to user
        AppLogger.error("Apple sign in failed: \(error)", category: AppLogger.ui)
    }
}

// Usage
AppLogger.debug("Message sent", category: AppLogger.ui)
AppLogger.info("API call succeeded", category: .networking)
AppLogger.error("Failed to save", category: .storage)

// Auto-redacts sensitive data
AppLogger.debug("Token: \(.redacted(token))")

// In AppError
case myFeature(reason: MyFeatureErrorReason)

enum MyFeatureErrorReason {
    case invalidInput
    case processingFailed
}

// Add user message
var userMessage: String {
    switch self {
    case .myFeature(.invalidInput):
        return "Please check your input"
    case .myFeature(.processingFailed):
        return "Processing failed. Please try again"
    }
}

extension AppLogger {
    static let myFeature = OSLog(
        subsystem: subsystem,
        category: "MyFeature"
    )
}

// Use it
AppLogger.info("Feature initialized", category: .myFeature)