//
//  RulePolicy.swift
//  Severed
//

import Foundation

/// Gates every mutation of a rule. This is where Hard Mode is enforced:
/// while a hard-mode rule is actively blocking, nothing about it can be
/// weakened until the window ends.
enum RulePolicy {
    /// True while the rule is actively blocking with Hard Mode on.
    static func isHardLocked(
        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
    ) -> Bool {
        rule.hardMode && rule.status(at: now, calendar: calendar).isActive
    }

    static func canEdit(
        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
    ) -> Bool {
        !isHardLocked(rule, at: now, calendar: calendar)
    }

    static func canDisable(
        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
    ) -> Bool {
        !isHardLocked(rule, at: now, calendar: calendar)
    }

    static func canDelete(
        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
    ) -> Bool {
        !isHardLocked(rule, at: now, calendar: calendar)
    }

    /// Whether the user may lift the current block early ("Unblock").
    /// Requires an active window and Hard Mode off.
    static func canUnblock(
        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
    ) -> Bool {
        rule.status(at: now, calendar: calendar).isActive && !rule.hardMode
    }

    /// Hard Mode can always be turned on, but never off while the rule is
    /// actively blocking — that is the whole point of a hard block.
    static func canTurnOffHardMode(
        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
    ) -> Bool {
        !isHardLocked(rule, at: now, calendar: calendar)
    }

    /// Pauses the rule's current window. Returns false (and changes nothing)
    /// when unblocking is not allowed.
    @discardableResult
    static func unblock(
        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
    ) -> Bool {
        guard canUnblock(rule, at: now, calendar: calendar),
              let window = rule.schedule.activeWindow(containing: now, calendar: calendar)
        else { return false }
        rule.pausedUntil = window.end
        return true
    }
}