import Foundation

enum UserFacingError {
    static let generic = "Something went wrong. Please try again."

    static func message(for error: Error) -> String {
        if shouldUseGenericMessage(for: error) {
            return generic
        }

        let raw = (error as? LocalizedError)?.errorDescription ?? error.localizedDescription
        return sanitized(raw) ?? generic
    }

    static func networkMessage(for error: URLError) -> String {
        switch error.code {
        case .notConnectedToInternet:
            "You appear to be offline. Check your internet connection and try again."
        case .timedOut:
            "The request timed out. Please try again."
        case .networkConnectionLost:
            "Couldn't connect. Please try again."
        default:
            generic
        }
    }

    static func sanitized(_ message: String) -> String? {
        let trimmed = message.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else { return nil }
        guard !containsSensitiveContent(trimmed.lowercased()) else { return nil }
        return trimmed
    }

    private static func shouldUseGenericMessage(for error: Error) -> Bool {
        if error is DecodingError || error is EncodingError {
            return true
        }

        switch error {
        case PostGenerationError.invalidResponse,
             CommentGenerationError.invalidResponse,
             TitleOptimizationError.invalidResponse:
            return true
        default:
            return false
        }
    }

    private static func containsSensitiveContent(_ lower: String) -> Bool {
        lower.contains("api key")
            || lower.contains("apikey")
            || lower.contains("openai")
            || lower.contains("invalid_api_key")
            || lower.contains("incorrect api key")
            || lower.contains("bearer ")
            || lower.contains("sk-")
            || lower.contains("authentication")
            || lower.contains("not configured")
            || lower.contains("response format")
            || lower.contains("request failed")
            || lower.contains("ai request failed")
            || lower.contains("couldn't reach the ai service")
            || lower.contains("nsurlerrordomain")
            || lower.contains("cocoaerrordomain")
            || lower.contains("error domain")
            || (lower.contains("could not read") && lower.contains("response"))
            || (lower.contains("couldn't parse") && lower.contains("ai"))
            || (lower.contains("status") && lower.range(of: #"\b[1-5]\d{2}\b"#, options: .regularExpression) != nil)
    }
}