import Foundation

struct TerminalCloseProtectionCandidate: Equatable {
  let hasAgent: Bool
  let agentDisplayState: AgentDisplayState?
  let commandRunningDuration: TimeInterval?
  var editingAge: TimeInterval?
  var hasMarkedText = false
}

enum TerminalCloseProtectionReason: Equatable, Hashable {
  case recentInput
  case agentActive
  case longRunningCommand
}

struct TerminalCloseConfirmationDecision: Equatable {
  let protectedPaneCount: Int
  let reasons: Set<TerminalCloseProtectionReason>

  var requiresConfirmation: Bool {
    protectedPaneCount > 0
  }
}

enum TerminalCloseConfirmationPolicy {
  static let recentEditingThreshold: TimeInterval = 10
  static let longRunningCommandThreshold: TimeInterval = 10

  static func decision(
    for candidates: [TerminalCloseProtectionCandidate],
    threshold: TimeInterval = Self.longRunningCommandThreshold
  ) -> TerminalCloseConfirmationDecision {
    var protectedPaneCount = 0
    var reasons: Set<TerminalCloseProtectionReason> = []

    for candidate in candidates {
      var paneReasons: Set<TerminalCloseProtectionReason> = []
      if candidate.hasMarkedText || candidate.editingAge.map({ $0 <= recentEditingThreshold }) == true {
        paneReasons.insert(.recentInput)
      }
      if let reason = protectionReason(for: candidate, threshold: threshold) {
        paneReasons.insert(reason)
      }
      guard !paneReasons.isEmpty else { continue }
      protectedPaneCount += 1
      reasons.formUnion(paneReasons)
    }

    return TerminalCloseConfirmationDecision(
      protectedPaneCount: protectedPaneCount,
      reasons: reasons
    )
  }

  /// Alert body for a close prompt. Always names the worktree: the prompt can
  /// be triggered from the sidebar against a worktree whose tabs are not
  /// visible, so the target's identity must be part of the confirmation.
  static func informativeMessage(
    for decision: TerminalCloseConfirmationDecision,
    worktreeName: String
  ) -> String {
    let paneText =
      decision.protectedPaneCount == 1
      ? String(localized: "pane")
      : String(localized: "panes")
    let reasonText: String
    if decision.reasons.contains(.recentInput) {
      var activities = [String(localized: "recent input")]
      if decision.reasons.contains(.agentActive) {
        activities.append(String(localized: "active agent work or an unseen agent result"))
      }
      if decision.reasons.contains(.longRunningCommand) {
        activities.append(String(localized: "a command that has been running for at least 10 seconds"))
      }
      let activitiesList = activities.joined(separator: ", ")
      let template = String(localized: "This will close %lld %@ in “%@” with %@. Closing may lose unsubmitted input.")
      return String(format: template, decision.protectedPaneCount, paneText, worktreeName, activitiesList)
    } else if decision.reasons == Set([.agentActive]) {
      reasonText = String(localized: "active agent work or an unseen agent result")
    } else if decision.reasons == Set([.longRunningCommand]) {
      reasonText = String(localized: "a command that has been running for at least 10 seconds")
    } else {
      reasonText = String(localized: "active agent work, unseen agent results, or long-running commands")
    }
    let template = String(localized: "This will close %lld %@ in “%@” with %@.")
    return String(format: template, decision.protectedPaneCount, paneText, worktreeName, reasonText)
  }
  private static func protectionReason(
    for candidate: TerminalCloseProtectionCandidate,
    threshold: TimeInterval
  ) -> TerminalCloseProtectionReason? {
    if candidate.hasAgent {
      switch candidate.agentDisplayState {
      case .working, .blocked, .done:
        return .agentActive
      case .idle, .none:
        return nil
      }
    }

    guard let duration = candidate.commandRunningDuration, duration >= threshold else {
      return nil
    }
    return .longRunningCommand
  }
}