//
//  RuleStatus.swift
//  Severed
//

import Foundation

/// The live state of a rule at a moment in time. Derived, never stored.
enum RuleStatus: Equatable, Sendable {
    case disabled
    /// Enabled but no days selected, so it never fires.
    case dormant
    /// Currently blocking; ends at the associated date.
    case active(until: Date)
    /// The user unblocked the current window; blocking resumes at the next window.
    case paused(until: Date)
    case upcoming(startsAt: Date)

    var isActive: Bool {
        if case .active = self { return true }
        return false
    }

    /// Short status label shown on rule cards and detail sheets:
    /// "6h left", "Starts in 22h", "Paused", "Disabled".
    func label(relativeTo now: Date) -> String {
        switch self {
        case .disabled: "Disabled"
        case .dormant: "No days selected"
        case .paused: "Paused"
        case .active(let until): "\(Self.countdown(from: now, to: until)) left"
        case .upcoming(let start): "Starts in \(Self.countdown(from: now, to: start))"
        }
    }

    /// Compact countdown matching the reference app: minutes under an hour,
    /// hours (rounded up) under two days, then days.
    static func countdown(from now: Date, to target: Date) -> String {
        let minutes = max(1, Int(ceil(target.timeIntervalSince(now) / 60)))
        guard minutes >= 60 else { return "\(minutes)m" }
        let hours = (minutes + 59) / 60
        guard hours >= 48 else { return "\(hours)h" }
        return "\(hours / 24)d"
    }
}

extension BlockingRule {
    /// Live status of this rule. Schedule rules derive it from their time window;
    /// time/open-limit rules report upcoming based on their enabled days only
    /// (their blocking is triggered by usage, not the clock).
    func status(at now: Date = .now, calendar: Calendar = .current) -> RuleStatus {
        guard isEnabled else { return .disabled }
        guard !days.isEmpty else { return .dormant }

        guard kind == .schedule else {
            guard let next = schedule.nextStart(after: now, calendar: calendar) else {
                return .dormant
            }
            return .upcoming(startsAt: next)
        }

        if let window = schedule.activeWindow(containing: now, calendar: calendar) {
            if let pausedUntil, pausedUntil > now {
                return .paused(until: min(pausedUntil, window.end))
            }
            return .active(until: window.end)
        }
        if let next = schedule.nextStart(after: now, calendar: calendar) {
            return .upcoming(startsAt: next)
        }
        return .dormant
    }
}