package no.naiv.meddetsamme.alarm

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import java.time.LocalDate
import java.time.temporal.ChronoUnit
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import no.naiv.meddetsamme.data.MedDatabase
import no.naiv.meddetsamme.domain.ScheduleEngine
import no.naiv.meddetsamme.domain.ScheduleText
import no.naiv.meddetsamme.notify.Notifications
import no.naiv.meddetsamme.settings.SettingsStore

/**
 * Daily derived-state check: low stock (inventory ÷ scheduled rate) and
 * prescription renewal (rx expiry, independent of stock — decision #9).
 * One digest notification, not one per med.
 */
class SupplyCheckReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        val pending = goAsync()
        CoroutineScope(Dispatchers.IO).launch {
            try {
                check(context)
            } finally {
                AlarmScheduler(context).armSupplyCheck() // chain the next daily check
                pending.finish()
            }
        }
    }

    private companion object {
        /** "About a week in advance" for prescription renewal. */
        const val RX_LEAD_DAYS = 7

        /** How early to nudge before a resting seasonal med's window opens. */
        const val SEASON_START_LEAD_DAYS = 7L

        /** How early to offer "Forleng" before the current season closes. */
        const val SEASON_END_LEAD_DAYS = 5L
    }

    private suspend fun check(context: Context) {
        val db = MedDatabase.get(context)
        val today = LocalDate.now()
        val lowStock = mutableListOf<String>()
        val rxRenewal = mutableListOf<String>()

        val meds = db.medicationDao().getActive()
        // Dose-times feed both the supply rate and the season check; fetch once.
        val dtsByMed = meds.associate { it.med.id to db.doseTimeDao().getForMed(it.med.id) }

        // Per inventory item: consumption is the SUM across all active regimens
        // drawing from it — one shared box drains faster than either alone.
        for ((_, group) in meds.groupBy { it.item.id }) {
            val item = group.first().item
            var rate = 0.0
            for (med in group) rate += ScheduleEngine.dailyConsumption(dtsByMed[med.med.id].orEmpty(), today)
            if (ScheduleEngine.needsRefill(item.stockUnits, rate, item.lowStockLeadDays)) {
                val days = ScheduleEngine.daysOfSupply(item.stockUnits, rate)
                lowStock += "${item.name}: lager for ${ScheduleText.daysCount(days?.toInt() ?: 0)}"
            }
            if (ScheduleEngine.needsRenewal(item.rxExpiryEpochDay, today, RX_LEAD_DAYS)) {
                val expired = item.rxExpiryEpochDay!! < today.toEpochDay()
                rxRenewal += if (expired) "${item.name}: resept utløpt" else "${item.name}: resept må fornyes"
            }
        }

        for (med in meds) checkSeason(context, med.displayName, med.med.id, dtsByMed[med.med.id].orEmpty(), today)

        // Post-or-cancel: cancelling when the condition clears is what lets the
        // ongoing rx notification disappear by itself after a renewal.
        if (lowStock.isNotEmpty()) {
            Notifications.post(
                context,
                Notifications.SUPPLY_NOTIFICATION_ID,
                Notifications.buildLowStockNotification(context, lowStock),
            )
        } else {
            Notifications.cancel(context, Notifications.SUPPLY_NOTIFICATION_ID)
        }
        if (rxRenewal.isNotEmpty()) {
            Notifications.post(
                context,
                Notifications.RX_NOTIFICATION_ID,
                Notifications.buildRxNotification(context, rxRenewal),
            )
        } else {
            Notifications.cancel(context, Notifications.RX_NOTIFICATION_ID)
        }
    }

    /**
     * Per-med seasonal nudge, post-or-cancel like the digests above:
     * - resting and within [SEASON_START_LEAD_DAYS] of the next window → "Start nå";
     * - in season and within [SEASON_END_LEAD_DAYS] of its close → "Forleng" (once per close).
     * Acting on either (or the season simply passing) clears it the next day.
     */
    private fun checkSeason(
        context: Context,
        name: String,
        medId: Long,
        doseTimes: List<no.naiv.meddetsamme.data.DoseTime>,
        today: LocalDate,
    ) {
        val notifId = Notifications.seasonNotificationId(medId)
        if (!ScheduleEngine.isSeasonal(doseTimes)) {
            Notifications.cancel(context, notifId)
            return
        }
        if (!ScheduleEngine.inSeasonNow(doseTimes, today)) {
            val start = ScheduleEngine.nextSeasonStart(doseTimes, today)
            val days = start?.let { ChronoUnit.DAYS.between(today, it) }
            if (start != null && days != null && days in 0..SEASON_START_LEAD_DAYS) {
                Notifications.post(
                    context, notifId,
                    Notifications.buildSeasonNotification(
                        context, medId, name,
                        "Sesongen nærmer seg (fra ${ScheduleText.dateLabel(start)}). Vil du starte nå?",
                        starting = true,
                    ),
                )
            } else {
                Notifications.cancel(context, notifId)
            }
        } else {
            val end = ScheduleEngine.currentSeasonEnd(doseTimes, today)
            val days = end?.let { ChronoUnit.DAYS.between(today, it) }
            if (end != null && days != null && days in 0..SEASON_END_LEAD_DAYS) {
                // Once per season close, not daily: a dismissed card stays dismissed.
                // Keyed on the end date, so "Forleng" (new end) earns one fresh nudge.
                val settings = SettingsStore(context)
                if (settings.seasonEndNudgedEpochDay(medId) != end.toEpochDay()) {
                    Notifications.post(
                        context, notifId,
                        Notifications.buildSeasonNotification(
                            context, medId, name,
                            "Sesongen er snart over (${ScheduleText.dateLabel(end)}). Fortsatt plaget? Forleng to uker.",
                            starting = false,
                        ),
                    )
                    settings.setSeasonEndNudgedEpochDay(medId, end.toEpochDay())
                }
            } else {
                Notifications.cancel(context, notifId)
            }
        }
    }
}