package main

import (
	"regexp"
	"sort"
	"strings"

	"github.com/kami/maven/internal/lexicon"
)

// reminderMarker — the words that open a reminder. Stripped because they are
// the instruction, not the thing to say at the hour.
//
// The verbs come from the lexicon (Vikunja #530). They are a closed set of the
// commands she answers to, exactly like capture_verbs, and the literal that
// stood here knew four of them.
var reminderMarker = regexp.MustCompile(`(?i)^\s*(?:` + alternation(lexicon.ReminderVerbs()) +
	`)\s*(?:мне|me)?[\s,:—-]*`)

// reminderTimeWords — the time expressions a reminder carries, removed from
// the body because the fire time is already a column. Ordered longest-first
// where two could match the same words, so "через полтора часа" does not leave
// "полтора" behind.
//
// Go's \b is ASCII-only and never fires next to a Cyrillic letter, so the word
// boundaries here are written out as whitespace or an end of string — the same
// trap the agenda grammars hit.
//
// The Russian word lists are gone (Vikunja #530). The day words are
// lexicon.DayOffsetWords, which is why "вчера" and "позавчера" are stripped now
// and were not before, and the times of day are lexicon.PartsOfDay. What is
// still written out here is the shape of a clock reading — a preposition, digits,
// a colon — which is structured input rather than a claim about Russian.
var reminderTimeWords = []*regexp.Regexp{
	regexp.MustCompile(`(?i)(^|\s)через\s+\S+(\s+(часа?|часов|минут[уы]?|секунд[уы]?|дня|дней|недел[юи]))?(\s|$)`),
	regexp.MustCompile(`(?i)(^|\s)(в|во)\s+\d{1,2}(:\d{2})?(\s*(часа?|часов))?(\s*(утра|вечера|дня|ночи))?(\s|$)`),
	regexp.MustCompile(`(?i)(^|\s)(` + alternation(lexicon.DayOffsetWords()) + `)(\s|$)`),
	regexp.MustCompile(`(?i)(^|\s)(` + alternation(lexicon.PartsOfDay()) + `)(\s|$)`),
	regexp.MustCompile(`(?i)(^|\s)(at|in)\s+\d{1,2}(:\d{2})?\s*(am|pm)?(\s|$)`),
}

// alternation folds a lexicon set into one regexp branch, longest member first
// so "послезавтра" is not matched as "завтра" with a tail left behind. Sorted
// rather than taken as given, because two members of equal length must still
// produce the same pattern on every build.
func alternation(set []string) string {
	out := make([]string, 0, len(set))
	for _, w := range set {
		out = append(out, regexp.QuoteMeta(w))
	}
	sort.Slice(out, func(i, j int) bool {
		if len(out[i]) != len(out[j]) {
			return len(out[i]) > len(out[j])
		}
		return out[i] < out[j]
	})
	return strings.Join(out, "|")
}

// reminderBody is what she says at the hour.
//
// The whole utterance used to be stored, so /reminders read "напомни завтра в
// 9 утра выпить таблетки" where it should read "выпить таблетки", and the
// agenda recited the marker back at him (Vikunja #469). The fire time is
// already a column, and the marker is an instruction that was carried out.
//
// Falls back to the fuller text whenever stripping would leave nothing: an
// empty body is a reminder that fires and says nothing, which is worse than a
// wordy one.
func reminderBody(utterance, text string) string {
	body := strings.TrimSpace(text)
	if body == "" {
		body = strings.TrimSpace(utterance)
	}
	stripped := reminderMarker.ReplaceAllString(body, "")
	for _, re := range reminderTimeWords {
		stripped = re.ReplaceAllString(stripped, " ")
	}
	stripped = strings.TrimSpace(strings.Join(strings.Fields(stripped), " "))
	stripped = strings.Trim(stripped, " ,;:—-")
	if stripped == "" {
		return body
	}
	return stripped
}