import Foundation

/// Minimal XRP Ledger JSON-RPC client. A couple of public endpoints are tried
/// in order so a single outage does not break the wallet.
final class XRPClient {
  static let shared = XRPClient()

  private let endpoints = [
    "https://s1.ripple.com:51234/",
    "https://s2.ripple.com:51234/",
    "https://xrplcluster.com/",
  ]

  private var preferredEndpoint = 0
  private let session: URLSession

  private init() {
    let configuration = URLSessionConfiguration.ephemeral
    configuration.timeoutIntervalForRequest = 20
    configuration.waitsForConnectivity = false
    session = URLSession(configuration: configuration)
  }

  func rpc(_ method: String, _ params: [String: Any] = [:]) async throws -> [String: Any] {
    var lastError: Error = XRPError.network("XRP network is unavailable")
    for attempt in 0..<endpoints.count {
      let index = (preferredEndpoint + attempt) % endpoints.count
      guard let url = URL(string: endpoints[index]) else { continue }
      do {
        let result = try await send(method, params, to: url)
        preferredEndpoint = index
        return result
      } catch {
        lastError = error
      }
    }
    throw lastError
  }

  private func send(_ method: String, _ params: [String: Any], to url: URL) async throws -> [String: Any] {
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")
    let body: [String: Any] = ["method": method, "params": [params], "id": 1]
    request.httpBody = try JSONSerialization.data(withJSONObject: body)

    let (data, response) = try await session.data(for: request)
    guard let http = response as? HTTPURLResponse, (200..<300).contains(http.statusCode) else {
      throw XRPError.network("Ledger request failed (\(method))")
    }
    guard let json = try JSONSerialization.jsonObject(with: data) as? [String: Any] else {
      throw XRPError.network("Malformed ledger response")
    }

    let result = json["result"] as? [String: Any] ?? [:]
    if let error = result["error"] as? String {
      let message = result["error_message"] as? String ?? error
      throw XRPError.rpc(message)
    }
    if let error = json["error"] as? String {
      throw XRPError.rpc(json["error_message"] as? String ?? error)
    }
    return result
  }

  static func isAccountNotFound(_ error: Error) -> Bool {
    if case XRPError.rpc(let message) = error {
      return message == "actNotFound" || message.contains("Account not found")
    }
    return false
  }
}