// Towns of a lesson, as Word cells name them. Most lessons are in Novopolotsk; some faculties
// teach in Polotsk, and a cell says when a lesson or a whole day is in the other town:
// "Занятия в Полоцке" over a day's first row (that day, the column's lessons are in Polotsk),
// "Новополоцк" or "г.Новополоцк" on a line of its own, "246(Новополоцк)" after a room.

// Towns a cell may name without "г.": a bare capitalised word is otherwise a subject.
const TOWNS = "Новополоцк|Полоцк|Междуречье|Витебск|Минск";
const TOWN = String.raw`(?:г\.\s*([А-ЯЁ][а-яё]+(?:-[А-ЯЁ][а-яё]+)?)|(${TOWNS})е?)`;
// "Занятия в Полоцке", "Занятия проходят в г. Новополоцк": the rest of the line, if any, is a lesson.
const NOTE = new RegExp(
  String.raw`^[Зз]анятия\s+(?:(?:проход[яи]т|будут\s+проходить)\s+)?в\s+(?:г\.\s*)?([А-ЯЁ][а-яё]+(?:-[А-ЯЁ][а-яё]+)?)(?=$|[\s.,;:!–—-])[.!]?`,
  "u",
);
// A line that starts with the town: "г.Новополоцк", or "г. Полоцк, Дом офицеров" with the venue.
const LINE = new RegExp(String.raw`^\(?${TOWN}\)?(?:[.,]?$|(,\s*\S.*))`, "u");
// "246(Новополоцк)", "121 (г.Новополоцк)".
const AFTER_ROOM = new RegExp(String.raw`(?<=\d[А-ЯЁа-яё]{0,2})\s*\(${TOWN}\)`, "u");

/** "Полоцке" → "Полоцк", "Витебске" → "Витебск"; "Междуречье" stays. */
export const townName = (word) => word.replace(/(?<=(?:к|ст))е$/u, "");

/**
 * A note that a day is in another town, on a line of the cell: `{text, place, rest}`, the
 * cell without the note in `rest`; null when the cell has none.
 */
export function placeNote(text) {
  const lines = (text || "").split("\n");
  for (const [i, line] of lines.entries()) {
    const m = line.trim().match(NOTE);
    if (!m) continue;
    const rest = [...lines.slice(0, i), line.trim().slice(m[0].length).trim(), ...lines.slice(i + 1)]
      .filter((l) => l.trim())
      .join("\n");
    return { text: m[0].replace(/[.!]$/, "").replace(/\s+/g, " "), place: townName(m[1]), rest };
  }
  return null;
}

/** The town a lesson's own text names, and the text without it: `{place, rest}`. */
export function lessonPlace(text) {
  let place = null;
  const rest = (text || "")
    .split("\n")
    .filter((line) => {
      const m = line.trim().match(LINE);
      if (m && !place) place = townName(m[1] || m[2]);
      // The town alone goes; a venue after it stays in the text.
      return !m || m[3];
    })
    .join("\n")
    .replace(AFTER_ROOM, (_, named, town) => {
      place ||= townName(named || town);
      return "";
    });
  return { place, rest };
}

/**
 * The town of a lesson from the notes of its day: for every group of the lesson, a note for its
 * subgroup or the whole group, or — for a lesson of the whole group — notes in every subgroup
 * that name the same town. `labelsOf(group)`: the group's subgroup labels.
 */
export function placeOf(lesson, places, labelsOf) {
  let found = null;
  for (const group of lesson.groups) {
    const notes = places.filter(
      (p) => p.day === lesson.day && (!p.date || p.date === lesson.date) && p.groups.includes(group),
    );
    if (!notes.length) return null;
    const label = lesson.subgroups.find((s) => s.group === group)?.label;
    const own = (p) => p.subgroups.filter((s) => s.group === group).map((s) => s.label);
    let place = notes.find((p) => !own(p).length || (label && own(p).includes(label)))?.place;
    if (!place && !label) {
      const towns = new Map(notes.flatMap((p) => own(p).map((l) => [l, p.place])));
      const labels = labelsOf(group);
      if (labels.length && labels.every((l) => towns.has(l)) && new Set(towns.values()).size === 1)
        place = towns.get(labels[0]);
    }
    if (!place || (found && found !== place)) return null;
    found = place;
  }
  return found;
}