package com.tt.honeyDue.widget

import kotlinx.datetime.DateTimeUnit
import kotlinx.datetime.LocalDateTime
import kotlinx.datetime.TimeZone
import kotlinx.datetime.plus
import kotlinx.datetime.toInstant
import kotlinx.datetime.toLocalDateTime

/**
 * Pure-logic schedule for widget refresh cadence. Mirrors the iOS-parity
 * split from the P3 parity plan:
 *
 *  - 06:00 (inclusive) .. 23:00 (exclusive) local → refresh every 30 minutes
 *  - 23:00 (inclusive) .. 06:00 (exclusive) local → refresh every 120 minutes
 *
 * iOS ([BackgroundTaskManager.swift]) uses a random 12am–4am overnight
 * BGAppRefreshTask window rather than a fixed cadence, because iOS
 * `BGTaskScheduler` is coalesced by the system. Android's WorkManager runs
 * user-defined intervals, so this file encodes the ios-parity cadence the
 * plan specifies. The split 30/120 preserves the core intent: frequent
 * while awake, sparse while the user is asleep.
 */
object WidgetRefreshSchedule {

    private const val DAY_START_HOUR_INCLUSIVE = 6   // 06:00 local
    private const val DAY_END_HOUR_EXCLUSIVE = 23    // 23:00 local

    const val DAY_INTERVAL_MINUTES: Long = 30L
    const val NIGHT_INTERVAL_MINUTES: Long = 120L

    /**
     * Returns the refresh interval (in minutes) for a wall-clock time.
     *
     * Hour bands:
     *  - [06:00, 23:00) → [DAY_INTERVAL_MINUTES] (30)
     *  - [23:00, 06:00) → [NIGHT_INTERVAL_MINUTES] (120)
     */
    fun intervalMinutes(at: LocalDateTime): Long {
        val hour = at.hour
        return if (hour in DAY_START_HOUR_INCLUSIVE until DAY_END_HOUR_EXCLUSIVE) {
            DAY_INTERVAL_MINUTES
        } else {
            NIGHT_INTERVAL_MINUTES
        }
    }

    /**
     * Returns `now + intervalMinutes(now)` as a [LocalDateTime].
     *
     * Arithmetic is performed through [TimeZone.UTC] to avoid ambiguity
     * around DST transitions in the local zone — the absolute minute offset
     * is what WorkManager's `setInitialDelay` consumes, so the returned
     * wall-clock value is for display/testing only.
     */
    fun nextRefreshTime(now: LocalDateTime): LocalDateTime {
        val interval = intervalMinutes(now)
        val instant = now.toInstant(TimeZone.UTC)
        val next = instant.plus(interval, DateTimeUnit.MINUTE)
        return next.toLocalDateTime(TimeZone.UTC)
    }
}