package main

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"text/template"
	"time"

	"github.com/Masterminds/sprig/v3"
	"github.com/gin-gonic/gin"
	"github.com/tmc/langchaingo/llms"
	"github.com/tmc/langchaingo/llms/ollama"
	"github.com/tmc/langchaingo/llms/openai"
)

// Global Variables and Constants
var (
	paperlessBaseURL  = os.Getenv("PAPERLESS_BASE_URL")
	paperlessAPIToken = os.Getenv("PAPERLESS_API_TOKEN")
	openaiAPIKey      = os.Getenv("OPENAI_API_KEY")
	manualTag         = "paperless-gpt"
	autoTag           = "paperless-gpt-auto"
	llmProvider       = os.Getenv("LLM_PROVIDER")
	llmModel          = os.Getenv("LLM_MODEL")
	visionLlmProvider = os.Getenv("VISION_LLM_PROVIDER")
	visionLlmModel    = os.Getenv("VISION_LLM_MODEL")

	// Templates
	titleTemplate *template.Template
	tagTemplate   *template.Template
	templateMutex sync.RWMutex

	// Default templates
	defaultTitleTemplate = `I will provide you with the content of a document that has been partially read by OCR (so it may contain errors).
Your task is to find a suitable document title that I can use as the title in the paperless-ngx program.
Respond only with the title, without any additional information. The content is likely in {{.Language}}.

Content:
{{.Content}}
`

	defaultTagTemplate = `I will provide you with the content and the title of a document. Your task is to select appropriate tags for the document from the list of available tags I will provide. Only select tags from the provided list. Respond only with the selected tags as a comma-separated list, without any additional information. The content is likely in {{.Language}}.

Available Tags:
{{.AvailableTags | join ", "}}

Title:
{{.Title}}

Content:
{{.Content}}

Please concisely select the {{.Language}} tags from the list above that best describe the document.
Be very selective and only choose the most relevant tags since too many tags will make the document less discoverable.
`
)

// App struct to hold dependencies
type App struct {
	Client    *PaperlessClient
	LLM       llms.Model
	VisionLLM llms.Model
}

func main() {
	// Validate Environment Variables
	validateEnvVars()

	// Initialize PaperlessClient
	client := NewPaperlessClient(paperlessBaseURL, paperlessAPIToken)

	// Load Templates
	loadTemplates()

	// Initialize LLM
	llm, err := createLLM()
	if err != nil {
		log.Fatalf("Failed to create LLM client: %v", err)
	}

	// Initialize Vision LLM
	visionLlm, err := createVisionLLM()
	if err != nil {
		log.Fatalf("Failed to create Vision LLM client: %v", err)
	}

	// Initialize App with dependencies
	app := &App{
		Client:    client,
		LLM:       llm,
		VisionLLM: visionLlm,
	}

	// Start background process for auto-tagging
	go func() {

		minBackoffDuration := time.Second
		maxBackoffDuration := time.Hour
		pollingInterval := 10 * time.Second

		backoffDuration := minBackoffDuration
		for {
			if err := app.processAutoTagDocuments(); err != nil {
				log.Printf("Error in processAutoTagDocuments: %v", err)
				time.Sleep(backoffDuration)
				backoffDuration *= 2 // Exponential backoff
				if backoffDuration > maxBackoffDuration {
					log.Printf("Repeated errors in processAutoTagDocuments detected. Setting backoff to %v", maxBackoffDuration)
					backoffDuration = maxBackoffDuration
				}
			} else {
				backoffDuration = minBackoffDuration
			}
			time.Sleep(pollingInterval)
		}
	}()

	// Create a Gin router with default middleware (logger and recovery)
	router := gin.Default()

	// API routes
	api := router.Group("/api")
	{
		api.GET("/documents", app.documentsHandler)
		api.POST("/generate-suggestions", app.generateSuggestionsHandler)
		api.PATCH("/update-documents", app.updateDocumentsHandler)
		api.GET("/filter-tag", func(c *gin.Context) {
			c.JSON(http.StatusOK, gin.H{"tag": manualTag})
		})
		// Get all tags
		api.GET("/tags", app.getAllTagsHandler)
		api.GET("/prompts", getPromptsHandler)
		api.POST("/prompts", updatePromptsHandler)

		// OCR endpoints
		api.POST("/documents/:id/ocr", app.submitOCRJobHandler)
		api.GET("/jobs/ocr/:job_id", app.getJobStatusHandler)
		api.GET("/jobs/ocr", app.getAllJobsHandler)
	}

	// Serve static files for the frontend under /assets
	router.StaticFS("/assets", gin.Dir("./web-app/dist/assets", true))
	router.StaticFile("/vite.svg", "./web-app/dist/vite.svg")

	// Catch-all route for serving the frontend
	router.NoRoute(func(c *gin.Context) {
		c.File("./web-app/dist/index.html")
	})

	// Start OCR worker pool
	numWorkers := 1 // Number of workers to start
	startWorkerPool(app, numWorkers)

	log.Println("Server started on port :8080")
	if err := router.Run(":8080"); err != nil {
		log.Fatalf("Failed to run server: %v", err)
	}
}

// validateEnvVars ensures all necessary environment variables are set
func validateEnvVars() {
	if paperlessBaseURL == "" {
		log.Fatal("Please set the PAPERLESS_BASE_URL environment variable.")
	}

	if paperlessAPIToken == "" {
		log.Fatal("Please set the PAPERLESS_API_TOKEN environment variable.")
	}

	if llmProvider == "" {
		log.Fatal("Please set the LLM_PROVIDER environment variable.")
	}

	if llmModel == "" {
		log.Fatal("Please set the LLM_MODEL environment variable.")
	}

	if llmProvider == "openai" && openaiAPIKey == "" {
		log.Fatal("Please set the OPENAI_API_KEY environment variable for OpenAI provider.")
	}
}

// processAutoTagDocuments handles the background auto-tagging of documents
func (app *App) processAutoTagDocuments() error {
	ctx := context.Background()

	documents, err := app.Client.GetDocumentsByTags(ctx, []string{autoTag})
	if err != nil {
		return fmt.Errorf("error fetching documents with autoTag: %w", err)
	}

	if len(documents) == 0 {
		return nil // No documents to process
	}

	suggestionRequest := GenerateSuggestionsRequest{
		Documents:      documents,
		GenerateTitles: true,
		GenerateTags:   true,
	}

	suggestions, err := app.generateDocumentSuggestions(ctx, suggestionRequest)
	if err != nil {
		return fmt.Errorf("error generating suggestions: %w", err)
	}

	err = app.Client.UpdateDocuments(ctx, suggestions)
	if err != nil {
		return fmt.Errorf("error updating documents: %w", err)
	}

	return nil
}

// removeTagFromList removes a specific tag from a list of tags
func removeTagFromList(tags []string, tagToRemove string) []string {
	filteredTags := []string{}
	for _, tag := range tags {
		if tag != tagToRemove {
			filteredTags = append(filteredTags, tag)
		}
	}
	return filteredTags
}

// getLikelyLanguage determines the likely language of the document content
func getLikelyLanguage() string {
	likelyLanguage := os.Getenv("LLM_LANGUAGE")
	if likelyLanguage == "" {
		likelyLanguage = "English"
	}
	return strings.Title(strings.ToLower(likelyLanguage))
}

// loadTemplates loads the title and tag templates from files or uses default templates
func loadTemplates() {
	templateMutex.Lock()
	defer templateMutex.Unlock()

	// Ensure prompts directory exists
	promptsDir := "prompts"
	if err := os.MkdirAll(promptsDir, os.ModePerm); err != nil {
		log.Fatalf("Failed to create prompts directory: %v", err)
	}

	// Load title template
	titleTemplatePath := filepath.Join(promptsDir, "title_prompt.tmpl")
	titleTemplateContent, err := os.ReadFile(titleTemplatePath)
	if err != nil {
		log.Printf("Could not read %s, using default template: %v", titleTemplatePath, err)
		titleTemplateContent = []byte(defaultTitleTemplate)
		if err := os.WriteFile(titleTemplatePath, titleTemplateContent, os.ModePerm); err != nil {
			log.Fatalf("Failed to write default title template to disk: %v", err)
		}
	}
	titleTemplate, err = template.New("title").Funcs(sprig.FuncMap()).Parse(string(titleTemplateContent))
	if err != nil {
		log.Fatalf("Failed to parse title template: %v", err)
	}

	// Load tag template
	tagTemplatePath := filepath.Join(promptsDir, "tag_prompt.tmpl")
	tagTemplateContent, err := os.ReadFile(tagTemplatePath)
	if err != nil {
		log.Printf("Could not read %s, using default template: %v", tagTemplatePath, err)
		tagTemplateContent = []byte(defaultTagTemplate)
		if err := os.WriteFile(tagTemplatePath, tagTemplateContent, os.ModePerm); err != nil {
			log.Fatalf("Failed to write default tag template to disk: %v", err)
		}
	}
	tagTemplate, err = template.New("tag").Funcs(sprig.FuncMap()).Parse(string(tagTemplateContent))
	if err != nil {
		log.Fatalf("Failed to parse tag template: %v", err)
	}
}

// createLLM creates the appropriate LLM client based on the provider
func createLLM() (llms.Model, error) {
	switch strings.ToLower(llmProvider) {
	case "openai":
		if openaiAPIKey == "" {
			return nil, fmt.Errorf("OpenAI API key is not set")
		}
		return openai.New(
			openai.WithModel(llmModel),
			openai.WithToken(openaiAPIKey),
		)
	case "ollama":
		host := os.Getenv("OLLAMA_HOST")
		if host == "" {
			host = "http://127.0.0.1:11434"
		}
		return ollama.New(
			ollama.WithModel(llmModel),
			ollama.WithServerURL(host),
		)
	default:
		return nil, fmt.Errorf("unsupported LLM provider: %s", llmProvider)
	}
}

func createVisionLLM() (llms.Model, error) {
	switch strings.ToLower(visionLlmProvider) {
	case "openai":
		if openaiAPIKey == "" {
			return nil, fmt.Errorf("OpenAI API key is not set")
		}
		return openai.New(
			openai.WithModel(visionLlmModel),
			openai.WithToken(openaiAPIKey),
		)
	case "ollama":
		host := os.Getenv("OLLAMA_HOST")
		if host == "" {
			host = "http://127.0.0.1:11434"
		}
		return ollama.New(
			ollama.WithModel(visionLlmModel),
			ollama.WithServerURL(host),
		)
	default:
		return nil, fmt.Errorf("unsupported LLM provider: %s", llmProvider)
	}
}