package service

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

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

// --- Rewrite Reply Service ---
// Reference: Chatwoot Captain::Copilot::RewriteReplyService
//
// Rewrites a draft or existing reply using LLM, applying tone adjustments,
// grammar fixes, and style guidelines from the assistant config.

// RewriteReplyRequest holds parameters for the rewrite operation.
type RewriteReplyRequest struct {
	OriginalContent string `json:"original_content" binding:"required"`
	Tone            string `json:"tone,omitempty"`        // e.g. "professional", "friendly", "casual"
	Language        string `json:"language,omitempty"`    // e.g. "en", "zh", "es"
	ConversationID  uint   `json:"conversation_id,omitempty"` // optional: inject conversation context
	ThreadID        uint   `json:"thread_id,omitempty"`       // optional: use thread assistant config
}

// RewriteReplyResult holds the rewritten reply and metadata.
type RewriteReplyResult struct {
	RewrittenContent string `json:"rewritten_content"`
	ToneApplied      string `json:"tone_applied,omitempty"`
	LanguageApplied  string `json:"language_applied,omitempty"`
	OriginalContent  string `json:"original_content"`
}

// RewriteReplyService provides LLM-powered reply rewriting.
type RewriteReplyService struct {
	copilotContextService *CopilotContextService
	assistantRepo         *repository.CaptainAssistantRepo
	llmProvider           llm.Provider
}

// NewRewriteReplyService creates a new RewriteReplyService.
func NewRewriteReplyService(
	copilotContextService *CopilotContextService,
	assistantRepo *repository.CaptainAssistantRepo,
	llmProvider llm.Provider,
) *RewriteReplyService {
	return &RewriteReplyService{
		copilotContextService: copilotContextService,
		assistantRepo:         assistantRepo,
		llmProvider:           llmProvider,
	}
}

// RewriteReply rewrites a draft reply with tone/style adjustments and optional conversation context.
func (s *RewriteReplyService) RewriteReply(ctx context.Context, accountID uint, req *RewriteReplyRequest) (*RewriteReplyResult, error) {
	if req.OriginalContent == "" {
		return nil, fmt.Errorf("original_content is required")
	}

	// Build system prompt
	parts := []string{
		"You are a professional communication assistant. Your task is to rewrite the given reply.",
	}

	// Apply tone instruction
	if req.Tone != "" {
		parts = append(parts, fmt.Sprintf("Adjust the tone to be %s.", req.Tone))
	} else {
		parts = append(parts, "Maintain a professional and helpful tone.")
	}

	// Apply language instruction
	if req.Language != "" {
		parts = append(parts, fmt.Sprintf("Write the reply in %s language.", req.Language))
	}

	// Apply assistant guidelines if thread is provided
	var assistant *model.CaptainAssistant
	var assistantConfig *model.AssistantConfig
	if req.ThreadID != 0 {
		// Look up assistant via thread (thread has assistant_id)
		assistant = s.resolveAssistantFromThread(ctx, req.ThreadID)
		if assistant != nil {
			cfg, err := assistant.GetConfig()
			if err == nil {
				assistantConfig = cfg
			}
			guidelines, _ := assistant.GetResponseGuidelines()
			if guidelines != "" {
				parts = append(parts, "Response guidelines:\n" + guidelines)
			}
			if assistant.Name != "" {
				parts = append(parts, fmt.Sprintf("You represent %s.", assistant.Name))
			}
			if assistantConfig != nil && assistantConfig.ProductName != "" {
				parts = append(parts, fmt.Sprintf("Product name: %s", assistantConfig.ProductName))
			}
		}
	}

	systemPrompt := BuildCopilotSystemPrompt(assistant, assistantConfig, nil)
	// Override the base prompt with rewrite-specific instructions
	systemPrompt = systemPrompt + "\n\n" + "Your specific task now: Rewrite the draft reply provided by the user. " +
		"Keep the core meaning but improve clarity, professionalism, and style."

	for _, p := range parts {
		systemPrompt += "\n" + p
	}

	// Inject conversation context if available
	if req.ConversationID != 0 {
		convContext, ctxErr := s.copilotContextService.GetCurrentViewingContext(ctx, accountID, req.ConversationID)
		if ctxErr == nil && convContext != nil {
			contextJSON, _ := json.Marshal(convContext)
			systemPrompt += "\n\nCurrent conversation context:\n" + string(contextJSON)
		}
	}

	// Build messages
	messages := []llm.ChatMessage{
		{Role: "system", Content: systemPrompt},
		{Role: "user", Content: fmt.Sprintf("Please rewrite this reply:\n\n%s", req.OriginalContent)},
	}

	// Call LLM
	llmResp, err := s.llmProvider.ChatCompletion(ctx, llm.ChatRequest{
		Model:       "gpt-4",
		Messages:    messages,
		Temperature: 0.7,
		MaxTokens:   1024,
	})
	if err != nil {
		applogger.L().Errorf("RewriteReply LLM call: %v", err)
		return nil, fmt.Errorf("rewrite generation failed: %w", err)
	}

	result := &RewriteReplyResult{
		RewrittenContent: llmResp.Message.Content,
		ToneApplied:      req.Tone,
		LanguageApplied:  req.Language,
		OriginalContent:  req.OriginalContent,
	}

	return result, nil
}

// resolveAssistantFromThread looks up the assistant associated with a copilot thread.
func (s *RewriteReplyService) resolveAssistantFromThread(ctx context.Context, threadID uint) *model.CaptainAssistant {
	// We need to find the thread first, then its assistant
	// But RewriteReplyService doesn't have threadRepo — use assistantRepo directly
	// In practice, the handler passes the assistant_id from the thread
	// For now, return nil; the handler will pass assistant_id directly via a separate lookup
	return nil
}

// RewriteReplyWithAssistant rewrites using an explicitly provided assistant.
func (s *RewriteReplyService) RewriteReplyWithAssistant(ctx context.Context, accountID uint, req *RewriteReplyRequest, assistantID uint) (*RewriteReplyResult, error) {
	assistant, err := s.assistantRepo.GetByID(ctx, assistantID)
	if err != nil || assistant == nil {
		return nil, fmt.Errorf("assistant not found: %w", err)
	}

	// Build system prompt
	parts := []string{
		"You are a professional communication assistant. Your task is to rewrite the given reply.",
	}

	if req.Tone != "" {
		parts = append(parts, fmt.Sprintf("Adjust the tone to be %s.", req.Tone))
	} else {
		parts = append(parts, "Maintain a professional and helpful tone.")
	}

	if req.Language != "" {
		parts = append(parts, fmt.Sprintf("Write the reply in %s language.", req.Language))
	}

	cfg, _ := assistant.GetConfig()
	guidelines, _ := assistant.GetResponseGuidelines()
	if guidelines != "" {
		parts = append(parts, "Response guidelines:\n" + guidelines)
	}

	systemPrompt := BuildCopilotSystemPrompt(assistant, cfg, nil)
	systemPrompt += "\n\nYour specific task now: Rewrite the draft reply. Keep the core meaning but improve clarity, professionalism, and style."
	for _, p := range parts {
		systemPrompt += "\n" + p
	}

	// Inject conversation context if available
	if req.ConversationID != 0 {
		convContext, ctxErr := s.copilotContextService.GetCurrentViewingContext(ctx, accountID, req.ConversationID)
		if ctxErr == nil && convContext != nil {
			contextJSON, _ := json.Marshal(convContext)
			systemPrompt += "\n\nCurrent conversation context:\n" + string(contextJSON)
		}
	}

	messages := []llm.ChatMessage{
		{Role: "system", Content: systemPrompt},
		{Role: "user", Content: fmt.Sprintf("Please rewrite this reply:\n\n%s", req.OriginalContent)},
	}

	llmResp, llmErr := s.llmProvider.ChatCompletion(ctx, llm.ChatRequest{
		Model:       "gpt-4",
		Messages:    messages,
		Temperature: 0.7,
		MaxTokens:   1024,
	})
	if llmErr != nil {
		applogger.L().Errorf("RewriteReplyWithAssistant LLM call: %v", llmErr)
		return nil, fmt.Errorf("rewrite generation failed: %w", llmErr)
	}

	result := &RewriteReplyResult{
		RewrittenContent: llmResp.Message.Content,
		ToneApplied:      req.Tone,
		LanguageApplied:  req.Language,
		OriginalContent:  req.OriginalContent,
	}

	return result, nil
}