package main

import (
	"regexp"
	"strings"
)

// reminderMarker — the words that open a reminder. Stripped because they are
// the instruction, not the thing to say at the hour.
var reminderMarker = regexp.MustCompile(`(?i)^\s*(?:напомни(?:те)?|напомнить|remind)\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.
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)(завтра|послезавтра|сегодня|вечером|утром|днём|днем|ночью)(\s|$)`),
	regexp.MustCompile(`(?i)(^|\s)(at|in)\s+\d{1,2}(:\d{2})?\s*(am|pm)?(\s|$)`),
	regexp.MustCompile(`(?i)(^|\s)(tomorrow|today|tonight)(\s|$)`),
}

// 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
}