import Foundation
import LCEssentials

/// Explicit failure for callers that want to see it (`evaluateOrThrow`, the
/// notifications client). The safe `evaluate(...)` path never surfaces this —
/// it degrades to cache/defaults instead (FC-060 §4).
public enum FeatureControlError: Error, Sendable, Equatable {
    /// 400 `FEATURE_CONTROL_CONTEXT_INVALID`
    case invalidContext(code: String)
    /// 401 `…MISSING_AUTH` / `…INVALID_MODULE_TOKEN`
    case unauthorized(code: String)
    /// 403 `…PANEL_ROLE_REQUIRED` / `…INSUFFICIENT_PERMISSIONS`
    case forbidden(code: String)
    /// 429 `FEATURE_CONTROL_RATE_LIMIT`
    case rateLimited(code: String)
    /// Any other non-2xx status.
    case server(code: String, status: Int)
    /// Decoding failure, or any error not raised by `LCEssentials.API`'s HTTP path.
    case transport(message: String)
}

enum FeatureControlErrorMapper {
    /// `LCEssentials.API` throws an `NSError` (domain `LCEssentials.DEFAULT_ERROR_DOMAIN`,
    /// `code` = HTTP status, `localizedFailureReason` = pretty-printed body) for non-2xx
    /// responses, or a bridged `DecodingError`/`URLError` for anything else. Only the
    /// former carries a real HTTP status to map.
    static func map(_ error: Error) -> FeatureControlError {
        let nsError = error as NSError
        guard nsError.domain == LCEssentials.DEFAULT_ERROR_DOMAIN else {
            return .transport(message: nsError.localizedDescription)
        }

        let status = nsError.code
        let bodyCode = extractCode(from: nsError.localizedFailureReason) ?? "UNKNOWN"
        switch status {
        case 400: return .invalidContext(code: bodyCode)
        case 401: return .unauthorized(code: bodyCode)
        case 403: return .forbidden(code: bodyCode)
        case 429: return .rateLimited(code: bodyCode)
        default:  return .server(code: bodyCode, status: status)
        }
    }

    private static func extractCode(from prettyJSON: String?) -> String? {
        guard let prettyJSON,
              let data = prettyJSON.data(using: .utf8),
              let object = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
              let code = object["code"] as? String else { return nil }
        return code
    }
}