package router

import "strings"

// Feed queries — "что нового в лентах?", "что нового по технологиям?"
// (Vikunja #258).
//
// Deterministic matching, like the calendar, plan and habit matchers above it:
// the LLM router says this is a query, and this decides whether it is a question
// about the feeds. A model deciding that would occasionally answer "что нового?"
// out of world knowledge, which is the one thing a feed reader exists to avoid.

// FeedQuery — a parsed "what's new" question. Category is the topic he named
// ("технологии"), empty when he asked about the feeds in general.
type FeedQuery struct {
	Category string
}

// feedNouns — the words that make a question about the feeds themselves.
var feedNouns = []string{
	"лента", "ленте", "ленты", "лентах", "лентам",
	"новости", "новостей", "новостях", "новостям",
	"новое", "нового", "новенького",
	"feed", "feeds", "news", "headlines",
}

// newnessMarkers — the "что нового" half. "нового" alone is in feedNouns
// because it carries the question on its own ("что нового?"); a bare "лента"
// needs the ask, which is what askMarkers below is for.
var askMarkers = []string{
	"что", "какие", "какое", "расскажи", "почитай", "прочитай", "покажи",
	"what", "any", "tell", "show", "read",
}

// ParseFeedQuery reports whether an utterance asks what is new in the feeds, and
// which topic if it names one after "по"/"о"/"про"/"about".
//
// Both a feed noun and an ask are required. "у меня новая лента в инстаграме" is
// a statement and must not be read as a request to recite headlines.
func ParseFeedQuery(text string) (FeedQuery, bool) {
	toks := planTokens(text)
	noun, ask := false, false
	for _, t := range toks {
		for _, n := range feedNouns {
			if t == n {
				noun = true
				break
			}
		}
		for _, a := range askMarkers {
			if t == a {
				ask = true
				break
			}
		}
	}
	if !noun || !ask {
		return FeedQuery{}, false
	}
	return FeedQuery{Category: feedCategory(toks)}, true
}

// categoryPreps — the prepositions a topic follows. Russian marks the topic with
// a preposition ("по технологиям", "про политику"), so the word after one is the
// category; there is no stemming here, and the match against the configured
// category is a prefix comparison for exactly that reason.
var categoryPreps = map[string]bool{"по": true, "о": true, "об": true, "про": true, "about": true, "on": true}

func feedCategory(toks []string) string {
	for i, t := range toks {
		if categoryPreps[t] && i+1 < len(toks) {
			next := toks[i+1]
			// "по новостям" names no topic, it repeats the noun.
			for _, n := range feedNouns {
				if next == n {
					return ""
				}
			}
			return next
		}
	}
	return ""
}

// CategoryMatches reports whether a note's text plausibly belongs to the
// category he named. Russian inflects the topic ("технологиям" vs the configured
// "технологии"), and there is no stemmer in this repo, so the comparison is on a
// common prefix — long enough that "полит" and "погод" stay apart, short enough
// to survive a case ending.
func CategoryMatches(text, category string) bool {
	if category == "" {
		return true
	}
	stem := categoryStem(category)
	if stem == "" {
		return false
	}
	return strings.Contains(strings.ToLower(text), stem)
}

// categoryStem cuts a word down to the part inflection leaves alone. 5 runes is
// the compromise: shorter words are used whole.
func categoryStem(word string) string {
	r := []rune(strings.ToLower(strings.TrimSpace(word)))
	if len(r) > 5 {
		r = r[:5]
	}
	return string(r)
}