learning_ai_clock/ios/ChronoMind/Shared/TimerEngine/Cascade.swift

// ── Pre-Warning Cascade System ─────────────────────────────────
// Cascade presets aligned with PRD: Aggressive, Standard, Light, Minimal, None, Custom
// Ported from web/src/lib/cascade.ts

import Foundation

// MARK: - Cascade Preset

enum CascadePreset: String, Codable, CaseIterable, Identifiable {
    case aggressive
    case standard
    case light
    case minimal
    case none
    case custom

    var id: String { rawValue }

    var label: String {
        switch self {
        case .aggressive: return "Aggressive"
        case .standard: return "Standard"
        case .light: return "Light"
        case .minimal: return "Minimal"
        case .none: return "None (fire only)"
        case .custom: return "Custom"
        }
    }

    /// Default intervals in minutes before target time
    var defaultIntervals: [Int] {
        switch self {
        case .aggressive: return [240, 180, 120, 90, 60, 30, 15, 5, 1]
        case .standard: return [120, 60, 30, 15, 5]
        case .light: return [60, 15, 5]
        case .minimal: return [15]
        case .none: return []
        case .custom: return []
        }
    }
}

// MARK: - Cascade Warning

struct CascadeWarning: Codable, Identifiable, Equatable {
    let id: String
    let minutesBefore: Int
    var fired: Bool
    var firedAt: Date?
    var scheduledTime: Date

    static func == (lhs: CascadeWarning, rhs: CascadeWarning) -> Bool {
        lhs.id == rhs.id
    }
}

// MARK: - Cascade Config

struct CascadeConfig: Codable {
    let preset: CascadePreset
    let intervals: [Int] // minutes before target time (for custom preset)
}

// MARK: - Cascade Functions

/// Calculate all warning timestamps from target time and cascade intervals.
/// Filters out warnings that would be in the past relative to `now`.
func calculateCascadeWarnings(
    targetTime: Date,
    intervals: [Int],
    now: Date = Date()
) -> [CascadeWarning] {
    let sorted = intervals.sorted(by: >) // largest first (earliest warning)
    return sorted.enumerated().map { idx, minutesBefore in
        let scheduledTime = targetTime.addingTimeInterval(-Double(minutesBefore) * 60.0)
        return CascadeWarning(
            id: "w-\(idx)-\(minutesBefore)m",
            minutesBefore: minutesBefore,
            fired: scheduledTime <= now,
            firedAt: scheduledTime <= now ? scheduledTime : nil,
            scheduledTime: scheduledTime
        )
    }
}

/// Get the next unfired warning from a cascade.
func getNextWarning(_ warnings: [CascadeWarning]) -> CascadeWarning? {
    warnings.first(where: { !$0.fired })
}

/// Check which warnings should fire given the current time.
/// Returns newly-fired warning IDs and mutates the warnings array.
@discardableResult
func checkWarnings(_ warnings: inout [CascadeWarning], now: Date = Date()) -> [String] {
    var newlyFired: [String] = []
    for i in warnings.indices {
        if !warnings[i].fired && warnings[i].scheduledTime <= now {
            warnings[i].fired = true
            warnings[i].firedAt = now
            newlyFired.append(warnings[i].id)
        }
    }
    return newlyFired
}

/// Get intervals for a preset, or custom intervals if preset is 'custom'.
func getCascadeIntervals(_ config: CascadeConfig) -> [Int] {
    if config.preset == .custom {
        return config.intervals.sorted(by: >)
    }
    return config.preset.defaultIntervals
}

/// Format minutes into human-readable string.
func formatMinutesBefore(_ minutes: Int) -> String {
    if minutes >= 60 {
        let hours = minutes / 60
        let remaining = minutes % 60
        if remaining == 0 { return "\(hours)h" }
        return "\(hours)h \(remaining)m"
    }
    return "\(minutes)m"
}