package search

import (
	"context"
	"sort"
	"strings"
	"unicode/utf8"
)

const (
	MaxQueryRunes = 1500
	MaxK          = 20
	DefaultK      = 8
	DefaultV2K    = 5
	NameSearxNG   = "searxng"
	NameBraveLLM  = "brave_llm"
	NameTavily    = "tavily"
)

var sourceRank = map[string]int{
	NameSearxNG:  0,
	NameBraveLLM: 1,
	NameTavily:   2,
}

// Hit is one search result after mapping. No page body, no vendor answers.
type Hit struct {
	URL     string  `json:"url"`
	Title   string  `json:"title"`
	Snippet string  `json:"snippet"`
	Score   float64 `json:"score"`
	Source  string  `json:"source"`
}

// Source is one upstream. Config-fixed endpoint; never a request URL.
type Source interface {
	Name() string
	Search(ctx context.Context, query string, k int) SourceOut
}

type SourceOut struct {
	Hits    []Hit
	Warn    string
	Credits int
}

func ValidateQuery(q string) string {
	q = strings.TrimSpace(q)
	if q == "" {
		return "invalid query"
	}
	if utf8.RuneCountInString(q) > MaxQueryRunes {
		return "invalid query"
	}
	return ""
}

func ClampK(k, def int) int {
	if k <= 0 {
		k = def
	}
	if k > MaxK {
		return MaxK
	}
	return k
}

// Dedupe by canonical URL. First source (in fan-in order) wins the Source
// field; a later longer snippet replaces the text.
func Dedupe(in []Hit) []Hit {
	type slot struct {
		h Hit
		i int
	}
	order := make([]string, 0)
	seen := map[string]*slot{}
	for _, h := range in {
		canon := CanonicalURL(h.URL)
		if canon == "" {
			continue
		}
		h.URL = canon
		if s, ok := seen[canon]; ok {
			if len(h.Snippet) > len(s.h.Snippet) {
				src := s.h.Source
				sc := s.h.Score
				s.h = h
				s.h.Source = src
				if sc > s.h.Score {
					s.h.Score = sc
				}
			}
			continue
		}
		cp := h
		seen[canon] = &slot{h: cp, i: len(order)}
		order = append(order, canon)
	}
	out := make([]Hit, 0, len(order))
	for _, c := range order {
		out = append(out, seen[c].h)
	}
	return out
}

func sortBySourceOrder(hits []Hit) {
	sort.SliceStable(hits, func(i, j int) bool {
		ri, rj := sourceRank[hits[i].Source], sourceRank[hits[j].Source]
		if ri != rj {
			return ri < rj
		}
		return false
	})
}