package service

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

	"github.com/gochat/gochat/internal/llm"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// IntentService provides LLM-based intent recognition for customer messages.
// Reference: Chatwoot Captain::Llm::AssistantChatService intent classification
type IntentService struct {
	llmProvider llm.Provider
}

// NewIntentService creates a new IntentService.
func NewIntentService(llmProvider llm.Provider) *IntentService {
	return &IntentService{llmProvider: llmProvider}
}

// IntentType represents the classified intent of a user message.
type IntentType string

const (
	IntentTypeQuestion      IntentType = "question"       // User asks a question
	IntentTypeComplaint     IntentType = "complaint"      // User expresses dissatisfaction
	IntentTypeRequest       IntentType = "request"        // User requests an action/feature
	IntentTypeFeedback      IntentType = "feedback"       // User provides feedback
	IntentTypeGreeting      IntentType = "greeting"       // User says hello/greetings
	IntentTypeUrgent        IntentType = "urgent"         // User expresses urgency
	IntentTypeCancellation  IntentType = "cancellation"   // User wants to cancel/stop
	IntentTypeBilling       IntentType = "billing"        // User has billing/payment issue
	IntentTypeTechnical     IntentType = "technical"      // User has technical/bug issue
	IntentTypeOther         IntentType = "other"          // Unclassified intent
)

// IntentResult holds the classification result.
type IntentResult struct {
	Intent       IntentType `json:"intent"`
	Confidence   float64    `json:"confidence"`
	SubIntents   []string   `json:"sub_intents,omitempty"`
	SuggestedTone string    `json:"suggested_tone,omitempty"` // empathetic, formal, casual
	KeyTopics    []string   `json:"key_topics,omitempty"`
}

// ClassifyIntentRequest is the DTO for intent classification.
type ClassifyIntentRequest struct {
	Message string `json:"message" validate:"required"`
	Language string `json:"language,omitempty"` // optional language hint
}

// ClassifyIntent analyzes a user message and returns its intent classification.
// Uses LLM to determine the primary intent, confidence level, sub-intents,
// suggested response tone, and key topics extracted from the message.
func (s *IntentService) ClassifyIntent(ctx context.Context, req *ClassifyIntentRequest) (*IntentResult, error) {
	systemPrompt := buildIntentSystemPrompt()

	messages := []llm.ChatMessage{
		{Role: "system", Content: systemPrompt},
		{Role: "user", Content: fmt.Sprintf("Classify the intent of this message:\n%s", req.Message)},
	}

	llmResp, err := s.llmProvider.ChatCompletion(ctx, llm.ChatRequest{
		Model:       "gpt-4",
		Messages:    messages,
		Temperature: 0.1, // Low temperature for consistent classification
		MaxTokens:   256,
	})
	if err != nil {
		applogger.L().Errorf("ClassifyIntent LLM call: %v", err)
		return nil, fmt.Errorf("intent classification failed: %w", err)
	}

	if len(llmResp.Choices) == 0 {
		return &IntentResult{Intent: IntentTypeOther, Confidence: 0.0}, nil
	}

	content := llmResp.Choices[0].Message.Content
	var result IntentResult
	if err := json.Unmarshal([]byte(extractJSON(content)), &result); err != nil {
		// Fallback: try to parse intent from raw text
		result.Intent = parseIntentFromText(content)
		result.Confidence = 0.5
	}

	return &result, nil
}

// buildIntentSystemPrompt constructs the system prompt for intent classification.
func buildIntentSystemPrompt() string {
	return `You are an intent classifier for customer support messages. Analyze the message and classify its primary intent.

Valid intents: question, complaint, request, feedback, greeting, urgent, cancellation, billing, technical, other

For each message, return a JSON object with:
- "intent": the primary intent (must be one of the valid intents above)
- "confidence": a float between 0.0 and 1.0 indicating classification confidence
- "sub_intents": an array of secondary intents if present (optional)
- "suggested_tone": recommended response tone (empathetic, formal, casual, professional)
- "key_topics": an array of key topics/subjects mentioned in the message

Return ONLY the JSON object, no other text.`
}

// extractJSON tries to extract a JSON object from a string that may contain
// markdown formatting or other noise around the JSON.
func extractJSON(s string) string {
	// Try to find JSON between ```json and ``` markers
	if idx := strings.Index(s, "```json"); idx != -1 {
		s = s[idx+7:]
		if end := strings.Index(s, "```"); end != -1 {
			return strings.TrimSpace(s[:end])
		}
	}
	// Try to find JSON between ``` and ```
	if idx := strings.Index(s, "```"); idx != -1 {
		s = s[idx+3:]
		if end := strings.Index(s, "```"); end != -1 {
			return strings.TrimSpace(s[:end])
		}
	}
	// Try to find a JSON object by looking for { ... }
	start := strings.Index(s, "{")
	end := strings.LastIndex(s, "}")
	if start != -1 && end != -1 && end > start {
		return s[start:end+1]
	}
	return s
}

// parseIntentFromText attempts to extract an intent from raw LLM text when
// JSON parsing fails.
func parseIntentFromText(text string) IntentType {
	textLower := strings.ToLower(text)
	intentKeywords := map[IntentType][]string{
		IntentTypeQuestion:     {"question", "ask", "wonder", "curious", "how", "what", "why", "when", "where"},
		IntentTypeComplaint:    {"complaint", "unhappy", "dissatisfied", "disappointed", "angry", "frustrated", "terrible", "awful"},
		IntentTypeRequest:      {"request", "please", "want", "need", "can you", "could you", "would like"},
		IntentTypeFeedback:     {"feedback", "suggestion", "improvement", "opinion", "review", "rating"},
		IntentTypeGreeting:     {"hello", "hi", "hey", "good morning", "good afternoon", "greetings"},
		IntentTypeUrgent:       {"urgent", "emergency", "asap", "immediately", "critical", "right now"},
		IntentTypeCancellation: {"cancel", "stop", "unsubscribe", "discontinue", "terminate", "end"},
		IntentTypeBilling:      {"billing", "payment", "charge", "invoice", "refund", "price", "cost", "money"},
		IntentTypeTechnical:    {"bug", "error", "crash", "broken", "not working", "issue", "problem", "fail"},
	}

	for intent, keywords := range intentKeywords {
		for _, kw := range keywords {
			if strings.Contains(textLower, kw) {
				return intent
			}
		}
	}
	return IntentTypeOther
}