vyatsu-schedule/app/src/main/java/agzam/vyatsu/data/remote/TeacherScheduleParser.kt

package agzam.vyatsu.data.remote

import agzam.vyatsu.data.remote.pdf.TextPatterns
import agzam.vyatsu.domain.model.Day
import agzam.vyatsu.domain.model.Lesson
import agzam.vyatsu.domain.model.LessonType
import agzam.vyatsu.domain.model.TimeSlot
import org.jsoup.Jsoup
import org.jsoup.nodes.Element
import java.time.LocalDate
import java.time.LocalTime
import java.time.format.DateTimeFormatter

object TeacherScheduleParser {

    private val DAY_REGEX = Regex("""^(понедельник|вторник|среда|четверг|пятница|суббота|воскресенье)\s+(\d{2}\.\d{2}\.\d{2})$""")
    private val INTERVAL_REGEX = Regex("""^(\d{2}:\d{2})-(\d{2}:\d{2})$""")
    private val GROUP_TOKEN = Regex("""(?U)\b[А-ЯЁа-яё]{1,4}-\d{2,4}-\d{2}-\d{2}\b""")
    private val SPLIT_BY_GROUP = Regex("""(?U)(?=\b[А-ЯЁа-яё]{1,4}-\d{2,4}-\d{2}-\d{2}\b)""")
    private val DATE_FMT = DateTimeFormatter.ofPattern("dd.MM.yy")

    data class ParsedTeacherSchedule(val teachers: List<String>, val days: List<Day>)

    fun parse(html: String): ParsedTeacherSchedule {
        val doc = Jsoup.parse(html)
        var headerFound = false
        var teachers: List<String> = emptyList()
        val days = mutableListOf<Day>()
        var currentDate: LocalDate? = null
        var currentIntervals: MutableList<TimeSlot>? = null

        fun flushDay() {
            val date = currentDate ?: return
            val intervals = currentIntervals ?: return
            if (intervals.isNotEmpty()) days.add(Day(date, intervals.toList()))
        }

        for (tr in doc.select("tr")) {
            val tds = tr.children().filter { it.tagName() == "td" }
            if (tds.size < 2) continue
            val first = cellText(tds[0])
            val second = cellText(tds[1])
            if (!headerFound && first == "День" && second == "Интервал") {
                teachers = tds.drop(2)
                    .map { cellText(it.selectFirst("span") ?: it) }
                    .filter { it.isNotEmpty() }
                    .distinct()
                headerFound = true
                continue
            }
            val dayMatch = DAY_REGEX.matchEntire(first)
            val intervalMatch = INTERVAL_REGEX.matchEntire(if (dayMatch != null) second else first)
            if (dayMatch != null) {
                flushDay()
                currentDate = LocalDate.parse(dayMatch.groupValues[2], DATE_FMT)
                currentIntervals = mutableListOf()
            }
            if (intervalMatch != null && currentIntervals != null) {
                parseIntervalRow(tds, intervalMatch, if (dayMatch != null) 2 else 1, teachers, currentIntervals!!)
            }
        }
        flushDay()
        return ParsedTeacherSchedule(teachers, days)
    }

    private fun parseIntervalRow(
        tds: List<Element>,
        intervalMatch: MatchResult,
        startCol: Int,
        teachers: List<String>,
        intervals: MutableList<TimeSlot>
    ) {
        val start = LocalTime.parse(intervalMatch.groupValues[1])
        val end = LocalTime.parse(intervalMatch.groupValues[2])
        val lessons = mutableListOf<Lesson>()
        for (i in teachers.indices) {
            val cell = tds.getOrNull(startCol + i) ?: continue
            lessons += parseCell(cell, teachers[i])
        }
        if (lessons.isNotEmpty()) intervals.add(TimeSlot(start, end, lessons))
    }

    private fun parseCell(cell: Element, teacher: String): List<Lesson> {
        val raw = cellText(cell)
        if (raw.isEmpty()) return emptyList()
        val room = TextPatterns.ROOM_REGEX.find(raw)?.value
        val typeMatch = TextPatterns.LESSON_TYPE_REGEX.find(raw)
        val type = LessonType.fromRaw(typeMatch?.value?.trim() ?: "")
        val segments = raw.split(SPLIT_BY_GROUP).map { it.trim() }.filter { it.isNotEmpty() }
        val groupSegments = segments.filter { GROUP_TOKEN.containsMatchIn(it) }
        if (groupSegments.isEmpty()) {
            return listOf(
                Lesson(
                    raw = raw,
                    room = room,
                    subject = subjectOf(raw, room, typeMatch),
                    type = type,
                    teacher = teacher
                )
            )
        }
        val subject = subjectOf(raw, room, typeMatch)
        return groupSegments.flatMap { segment ->
            val groups = GROUP_TOKEN.findAll(segment).map { it.value }.distinct().toList()
            val subgroup = TextPatterns.SUBGROUP_REGEX.find(segment)?.value
            groups.map { group ->
                Lesson(
                    raw = segment,
                    room = room,
                    group = group,
                    subgroup = subgroup,
                    subject = subject,
                    type = type,
                    teacher = teacher
                )
            }
        }
    }

    private fun subjectOf(raw: String, room: String?, typeMatch: MatchResult?): String? {
        val end = typeMatch?.range?.first ?: GROUP_TOKEN.find(raw)?.range?.first ?: raw.length
        val prefix = raw.substring(0, end).trim()
        val stripped = room?.let { prefix.removePrefix(it).trim() } ?: prefix
        return stripped.ifEmpty { null }
    }

    private fun cellText(el: Element): String = el.text().replace('\u00A0', ' ').trim()
}