package no.naiv.meddetsamme.domain

import java.time.LocalDate
import java.time.format.DateTimeFormatter
import java.util.Locale
import no.naiv.meddetsamme.data.DoseTime

/**
 * Human-readable schedule descriptions (Norwegian, 24h) for the doctor
 * summary and the UI. Pure — unit-tested like the engine, since a wrong
 * description on a doctor's desk is a clinical communication error.
 */
object ScheduleText {

    /** Mask bit order matches ScheduleEngine: bit 0 = Sunday. */
    private val DAY_ABBREV = listOf("søn", "man", "tir", "ons", "tor", "fre", "lør")

    // Locale-pinned to nb so month names don't come out English on a foreign locale.
    private val dateFmt = DateTimeFormatter.ofPattern("d. MMM", Locale.forLanguageTag("nb"))

    fun describe(doseTime: DoseTime): String =
        "${"%02d:%02d".format(doseTime.minuteOfDay / 60, doseTime.minuteOfDay % 60)} " +
            "${daysText(doseTime)}${cycleText(doseTime)}${windowText(doseTime)}${seasonText(doseTime)}"

    /** " · syklus 21/28" when cyclic, else "". */
    fun cycleText(doseTime: DoseTime): String {
        val length = doseTime.cycleLengthDays
        val active = doseTime.cycleActiveDays
        return if (length > 0 && active in 1 until length) " · syklus $active/$length" else ""
    }

    /** " · 1.–14. jun", " · f.o.m. 1. jun", " · t.o.m. 14. jun" for a validity window. */
    fun windowText(doseTime: DoseTime): String {
        val start = doseTime.startEpochDay?.let { LocalDate.ofEpochDay(it) }
        val end = doseTime.endEpochDay?.let { LocalDate.ofEpochDay(it) }
        return when {
            start != null && end != null -> " · ${dateFmt.format(start)}–${dateFmt.format(end)}"
            start != null -> " · f.o.m. ${dateFmt.format(start)}"
            end != null -> " · t.o.m. ${dateFmt.format(end)}"
            else -> ""
        }
    }

    /** " · sesong 1. mar–31. mai" for a yearly seasonal window (month×100+day). */
    fun seasonText(doseTime: DoseTime): String {
        val start = doseTime.seasonStartMmdd
        val end = doseTime.seasonEndMmdd
        if (start <= 0 || end <= 0) return ""
        return " · sesong ${mmddText(start)}–${mmddText(end)}"
    }

    /** Formats a month×100+day mark as "1. mar". A leap-year-safe MonthDay so 0229 renders. */
    private fun mmddText(mmdd: Int): String =
        java.time.MonthDay.of(mmdd / 100, mmdd % 100).format(dateFmt)

    /** A single date as "1. mar" (nb-pinned), e.g. for "next season starts …". */
    fun dateLabel(date: LocalDate): String = dateFmt.format(date)

    fun daysText(doseTime: DoseTime): String {
        if (doseTime.intervalDays > 1) {
            return "(hver ${doseTime.intervalDays}. dag)"
        }
        return when (val mask = doseTime.daysOfWeekMask and 0x7F) {
            0x7F -> "(daglig)"
            0x3E -> "(man–fre)"
            0x41 -> "(lør–søn)"
            0 -> "(aldri)"
            else -> {
                // Week listed Monday-first for humans, despite bit 0 = Sunday.
                val days = (1..7).map { it % 7 }
                    .filter { mask and (1 shl it) != 0 }
                    .map { DAY_ABBREV[it] }
                "(${days.joinToString(", ")})"
            }
        }
    }

    /** "1 dag", "3 dager" — norsk flertall. */
    fun daysCount(days: Int): String = if (days == 1) "1 dag" else "$days dager"

    /** "1 tablett", "2,5 ml" — norsk desimalkomma. */
    fun amountText(amount: Double, unit: String): String {
        val number = if (amount == amount.toLong().toDouble()) {
            amount.toLong().toString()
        } else {
            amount.toString().replace('.', ',')
        }
        return "$number $unit"
    }
}