package router

import "strings"

// ruNumerals — spoken numbers as digits, for the clock hours and the minutes
// that follow them. Every case ending he might say is listed rather than
// stemmed: "в семь", "к семи", "около семи" are three forms of one hour, and a
// prefix rule short enough to cover them also matches "семья".
//
// Stops at thirty, which is as far as a spoken time goes ("без двадцати
// восемь", "в половине шестого"). Anything larger is said in digits.
var ruNumerals = map[string]string{
	"один": "1", "одного": "1", "одну": "1", "час": "1", "часу": "1",
	"два": "2", "две": "2", "двух": "2",
	"три": "3", "трёх": "3", "трех": "3",
	"четыре": "4", "четырёх": "4", "четырех": "4",
	"пять": "5", "пяти": "5",
	"шесть": "6", "шести": "6",
	"семь": "7", "семи": "7",
	"восемь": "8", "восьми": "8",
	"девять": "9", "девяти": "9",
	"десять": "10", "десяти": "10",
	"одиннадцать": "11", "одиннадцати": "11",
	"двенадцать": "12", "двенадцати": "12",
	"тринадцать": "13", "тринадцати": "13",
	"четырнадцать": "14", "четырнадцати": "14",
	"пятнадцать": "15", "пятнадцати": "15",
	"шестнадцать": "16", "шестнадцати": "16",
	"семнадцать": "17", "семнадцати": "17",
	"восемнадцать": "18", "восемнадцати": "18",
	"девятнадцать": "19", "девятнадцати": "19",
	"двадцать": "20", "двадцати": "20",
	"тридцать": "30", "тридцати": "30",
	"сорок": "40", "сорока": "40",
	"пятьдесят": "50", "пятидесяти": "50",
}

// numeralContext — the words that make a numeral a time. A numeral is only
// rewritten when one of these sits next to it, so "три яблока" in a note is
// left alone and "в три часа" is not.
var numeralContext = map[string]bool{
	"в": true, "во": true, "к": true, "около": true, "на": true,
	"часа": true, "часов": true, "час": true, "часу": true,
	"утра": true, "вечера": true, "дня": true, "ночи": true,
	"минут": true, "минуты": true, "минуту": true,
	"at": true, "by": true,
}

// SpellOutDigits rewrites spoken numbers as digits so the date parsers see the
// shape they know.
//
// "напомни мне позвонить маме в семь вечера" parsed to nothing, while "в 19:00"
// parsed fine (Vikunja #469). Speech is where reminders come from, and speech
// says the hour in words, so this is not a long-tail case — it is the ordinary
// one. dateparser reads "в 7 вечера" through the qualifier rewrite the python
// script already does; it does not read "в семь вечера".
//
// Conservative by construction: a numeral is only rewritten when a time word
// stands beside it. "три часа" becomes "3 часа"; "три яблока" stays as it is,
// and a note or a fact carrying a spoken number is untouched.
func SpellOutDigits(text string) string {
	toks := strings.Fields(text)
	if len(toks) == 0 {
		return text
	}
	out := make([]string, len(toks))
	copy(out, toks)
	for i, tok := range toks {
		key := strings.ToLower(strings.Trim(tok, ".,!?;:«»\"'"))
		digit, ok := ruNumerals[key]
		if !ok {
			continue
		}
		// "час" and "часу" are the hour noun as often as they are the number
		// one, and rewriting "в час дня" to "в 1 дня" is right either way. What
		// must not happen is rewriting the noun that gives another numeral its
		// context: "в семь часов" must keep "часов".
		if !hasTimeNeighbour(toks, i) {
			continue
		}
		out[i] = digit
	}
	return strings.Join(out, " ")
}

// hasTimeNeighbour reports whether the token before or after i is a time word.
func hasTimeNeighbour(toks []string, i int) bool {
	for _, j := range []int{i - 1, i + 1} {
		if j < 0 || j >= len(toks) {
			continue
		}
		if numeralContext[strings.ToLower(strings.Trim(toks[j], ".,!?;:«»\"'"))] {
			return true
		}
	}
	return false
}