import Foundation
import Combine

/// Performs the Phase 0 backend reachability check: `GET {baseURL}/api/status`.
///
/// This is a thin slice — the full `SparkControlClient` (label-merge, multipart,
/// sequential queueing, retries) arrives in Phase 5.
@MainActor
final class SparkControlHealth: ObservableObject {

    enum Status: Equatable {
        case unknown
        case checking
        case online(String)
        case offline(String)
    }

    @Published private(set) var status: Status = .unknown
    @Published private(set) var lastChecked: Date?

    func check(baseURL: String, skipTLS: Bool) async {
        status = .checking

        let trimmed = baseURL.trimmingCharacters(in: .whitespacesAndNewlines)
        let base = trimmed.hasSuffix("/") ? String(trimmed.dropLast()) : trimmed
        guard !base.isEmpty, let url = URL(string: base + "/api/status") else {
            status = .offline("Invalid host URL")
            return
        }

        let config = URLSessionConfiguration.ephemeral
        config.timeoutIntervalForRequest = 8
        config.waitsForConnectivity = false

        let delegate: URLSessionDelegate? = skipTLS
            ? InsecureTrustDelegate(allowedHost: url.host)
            : nil
        let session = URLSession(configuration: config, delegate: delegate, delegateQueue: nil)
        defer { session.finishTasksAndInvalidate() }

        do {
            let (data, response) = try await session.data(from: url)
            lastChecked = Date()
            guard let http = response as? HTTPURLResponse else {
                status = .offline("No HTTP response")
                return
            }
            if (200..<300).contains(http.statusCode) {
                status = .online(Self.summarize(data) ?? "Reachable")
            } else {
                status = .offline("HTTP \(http.statusCode)")
            }
        } catch {
            lastChecked = Date()
            status = .offline(error.localizedDescription)
        }
    }

    /// Best-effort one-line summary of the `/api/status` body, if it's JSON.
    private static func summarize(_ data: Data) -> String? {
        guard let object = try? JSONSerialization.jsonObject(with: data) as? [String: Any] else {
            return nil
        }
        if let s = object["status"] as? String { return s }
        if let s = object["state"] as? String { return s }
        return "Reachable"
    }
}