package agent

import (
	"context"
	"encoding/json"
	"regexp"
	"strings"

	"github.com/gooseek/backend/internal/llm"
	"github.com/gooseek/backend/internal/prompts"
)

type ClassificationResult struct {
	StandaloneFollowUp string   `json:"standaloneFollowUp"`
	SkipSearch         bool     `json:"skipSearch"`
	Topics             []string `json:"topics,omitempty"`
	QueryType          string   `json:"queryType,omitempty"`
	Engines            []string `json:"engines,omitempty"`
}

func classify(ctx context.Context, client llm.Client, query string, history []llm.Message, locale, detectedLang string) (*ClassificationResult, error) {
	prompt := prompts.GetClassifierPrompt(locale, detectedLang)

	historyStr := formatHistory(history)
	userContent := "<conversation>\n" + historyStr + "\nUser: " + query + "\n</conversation>"

	messages := []llm.Message{
		{Role: llm.RoleSystem, Content: prompt},
		{Role: llm.RoleUser, Content: userContent},
	}

	response, err := client.GenerateText(ctx, llm.StreamRequest{
		Messages: messages,
		Options:  llm.StreamOptions{MaxTokens: 1024},
	})
	if err != nil {
		return nil, err
	}

	jsonMatch := regexp.MustCompile(`\{[\s\S]*\}`).FindString(response)
	if jsonMatch == "" {
		return &ClassificationResult{
			StandaloneFollowUp: query,
			SkipSearch:         false,
		}, nil
	}

	var result ClassificationResult
	if err := json.Unmarshal([]byte(jsonMatch), &result); err != nil {
		return &ClassificationResult{
			StandaloneFollowUp: query,
			SkipSearch:         false,
		}, nil
	}

	if result.StandaloneFollowUp == "" {
		result.StandaloneFollowUp = query
	}

	return &result, nil
}

func fastClassify(query string, history []llm.Message) *ClassificationResult {
	queryLower := strings.ToLower(query)

	skipPatterns := []string{
		"привет", "как дела", "спасибо", "пока",
		"hello", "hi", "thanks", "bye",
		"объясни", "расскажи подробнее", "что ты имеешь",
	}

	skipSearch := false
	for _, p := range skipPatterns {
		if strings.Contains(queryLower, p) && len(query) < 50 {
			skipSearch = true
			break
		}
	}

	standalone := query

	if len(history) > 0 {
		pronouns := []string{
			"это", "этот", "эта", "эти",
			"он", "она", "оно", "они",
			"it", "this", "that", "they", "them",
		}

		hasPronouns := false
		for _, p := range pronouns {
			if strings.Contains(queryLower, p+" ") || strings.HasPrefix(queryLower, p+" ") {
				hasPronouns = true
				break
			}
		}

		if hasPronouns && len(history) >= 2 {
			lastAssistant := ""
			for i := len(history) - 1; i >= 0; i-- {
				if history[i].Role == llm.RoleAssistant {
					lastAssistant = history[i].Content
					break
				}
			}

			if lastAssistant != "" {
				topics := extractTopics(lastAssistant)
				if len(topics) > 0 {
					standalone = query + " (контекст: " + strings.Join(topics, ", ") + ")"
				}
			}
		}
	}

	engines := detectEngines(queryLower)

	return &ClassificationResult{
		StandaloneFollowUp: standalone,
		SkipSearch:         skipSearch,
		Engines:            engines,
	}
}

func generateSearchQueries(query string) []string {
	queries := []string{query}

	if len(query) > 100 {
		words := strings.Fields(query)
		if len(words) > 5 {
			queries = append(queries, strings.Join(words[:5], " "))
		}
	}

	keywordPatterns := []string{
		"как", "что такое", "где", "когда", "почему", "кто",
		"how", "what is", "where", "when", "why", "who",
	}

	for _, p := range keywordPatterns {
		if strings.HasPrefix(strings.ToLower(query), p) {
			withoutPrefix := strings.TrimPrefix(strings.ToLower(query), p)
			withoutPrefix = strings.TrimSpace(withoutPrefix)
			if len(withoutPrefix) > 10 {
				queries = append(queries, withoutPrefix)
			}
			break
		}
	}

	if len(queries) > 3 {
		queries = queries[:3]
	}

	return queries
}

func detectEngines(query string) []string {
	engines := []string{"google", "duckduckgo"}

	if strings.Contains(query, "новости") || strings.Contains(query, "news") {
		engines = append(engines, "google_news")
	}

	if strings.Contains(query, "видео") || strings.Contains(query, "video") {
		engines = append(engines, "youtube")
	}

	if strings.Contains(query, "товар") || strings.Contains(query, "купить") ||
		strings.Contains(query, "цена") || strings.Contains(query, "price") {
		engines = append(engines, "google_shopping")
	}

	return engines
}

func extractTopics(text string) []string {
	words := strings.Fields(text)
	if len(words) > 50 {
		words = words[:50]
	}

	topics := make([]string, 0)
	for _, w := range words {
		if len(w) > 5 && len(w) < 20 {
			r := []rune(w)
			if len(r) > 0 && ((r[0] >= 'A' && r[0] <= 'Z') || (r[0] >= 'А' && r[0] <= 'Я')) {
				topics = append(topics, w)
				if len(topics) >= 3 {
					break
				}
			}
		}
	}

	return topics
}

func formatHistory(messages []llm.Message) string {
	var sb strings.Builder
	for _, m := range messages {
		role := "User"
		if m.Role == llm.RoleAssistant {
			role = "Assistant"
		}
		sb.WriteString(role)
		sb.WriteString(": ")
		content := m.Content
		if len(content) > 500 {
			content = content[:500] + "..."
		}
		sb.WriteString(content)
		sb.WriteString("\n")
	}
	return sb.String()
}

func detectLanguage(text string) string {
	cyrillicCount := 0
	latinCount := 0

	for _, r := range text {
		if r >= 'а' && r <= 'я' || r >= 'А' && r <= 'Я' {
			cyrillicCount++
		} else if r >= 'a' && r <= 'z' || r >= 'A' && r <= 'Z' {
			latinCount++
		}
	}

	if cyrillicCount > latinCount {
		return "ru"
	}
	return "en"
}