package handlers

import (
	"fmt"
	"os"
	"slices"

	"git.odit.services/lfk/document-server/models"
	"github.com/gofiber/fiber/v2"
	"github.com/pdfcpu/pdfcpu/pkg/api"
	"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/model"
)

// GenerateCard godoc
//
//	@Summary		Generate runner cards
//	@Description	Generate cards based on the provided data
//	@Tags			pdfs
//	@Accept			json
//	@Param			data	body	models.CardRequest	true	"Card data"
//	@Produce		application/pdf
//	@Security		ApiKeyAuth
//	@Router			/v1/pdfs/cards [post]
func (h *DefaultHandler) GenerateCard(c *fiber.Ctx) error {
	logger := h.Logger.Named("GenerateCard")

	cardRequest := new(models.CardRequest)
	if err := c.BodyParser(cardRequest); err != nil {
		logger.Errorw("Invalid request", "error", err)
		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
			"error": err.Error(),
		})
	}
	if !slices.Contains([]string{"en", "de"}, cardRequest.Locale) {
		logger.Errorw("Invalid locale", "locale", cardRequest.Locale)
		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
			"error": "Invalid locale",
		})
	}

	logger = logger.With("locale", cardRequest.Locale)

	templateString, err := h.StaticService.GetTemplate(cardRequest.Locale, "card")
	if err != nil {
		logger.Errorw("Template not found", "error", err)
		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
			"error": "Template not found",
		})
	}
	template, err := h.Templater.StringToTemplate(templateString)
	if err != nil {
		logger.Errorw("Error parsing template", "error", err)
		return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
			"error": err.Error(),
		})
	}

	segmentLength := calculateOptimalSegmentSize(len(cardRequest.Cards))
	pdfs := []string{}
	for i := 0; i < len(cardRequest.Cards); i += segmentLength {

		segment := cardRequest.Cards[i:]
		if len(segment) > segmentLength {
			segment = cardRequest.Cards[i : i+segmentLength]
		}

		genConfig := &models.CardTemplateOptions{
			CardSegments:  splitCardSegments(segment),
			EventName:     h.Config.EventName,
			CardSubtitle:  h.Config.CardSubtitle,
			BarcodeFormat: h.Config.CardBarcodeFormat,
			BarcodePrefix: h.Config.CardBarcodePrefix,
		}

		logger.Info("Generating card html")
		result, err := h.Templater.Execute(template, genConfig)
		if err != nil {
			logger.Errorw("Error executing template", "error", err)
			return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
				"error": err.Error(),
			})
		}
		logger.Info("Generated card html")
		c.Set(fiber.HeaderContentType, "text/html")

		logger.Info("Converting html to pdf")
		pdf, err := h.Converter.ToPdf(result, "a4", false)
		if err != nil {
			logger.Errorw("Error converting html to pdf", "error", err)
			return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
				"error": err.Error(),
			})
		}

		tempFile, err := os.CreateTemp("", fmt.Sprintf("cards-%d-*.pdf", i/segmentLength))
		if err != nil {
			logger.Errorw("Error creating temp file", "error", err)
			return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
				"error": err.Error(),
			})
		}
		defer os.Remove(tempFile.Name()) // Ensure cleanup even on error paths

		if _, err := tempFile.Write(pdf); err != nil {
			logger.Errorw("Error writing pdf to temp file", "error", err)
			return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
				"error": err.Error(),
			})
		}
		tempFile.Close()
		pdfs = append(pdfs, tempFile.Name())
	}

	outputFile := "./output.pdf"
	conf := model.NewDefaultConfiguration()
	err = api.MergeCreateFile(pdfs, outputFile, false, conf)
	if err != nil {
		logger.Errorw("Failed to merge PDFs", "error", err)
		return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
			"error": err.Error(),
		})
	}

	// Clean up individual PDF files
	for _, file := range pdfs {
		if err := os.Remove(file); err != nil {
			logger.Warnw("Failed to remove temporary PDF file", "file", file, "error", err)
		}
	}

	// Set headers and return the merged PDF
	c.Set(fiber.HeaderContentType, "application/pdf")
	c.Set(fiber.HeaderContentDisposition, "attachment; filename=runner-cards.pdf")
	pdfBytes, err := os.ReadFile(outputFile)
	if err != nil {
		logger.Errorw("Failed to read merged PDF", "error", err)
		return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
			"error": err.Error(),
		})
	}
	os.Remove(outputFile) // Clean up the merged file

	logger.Info("Converted html to pdf")

	c.Set(fiber.HeaderContentType, "application/pdf")
	c.Set(fiber.HeaderContentDisposition, "attachment; filename=runner-cards.pdf")
	return c.Send(pdfBytes)
}

func calculateOptimalSegmentSize(totalCards int) int {
	if totalCards < 30 {
		return 25 // Reduces overhead for really small batches
	}

	// Base size for small batches
	if totalCards < 100 {
		return 50
	}

	// For medium batches
	if totalCards < 500 {
		return 75
	}

	// For large batches, be more conservative
	return 100
}

func invertCardArrayItemPairs(cards []models.Card) []models.Card {
	inverted := make([]models.Card, 0)
	for i := 0; i < len(cards); i += 2 {
		if i+1 < len(cards) {
			inverted = append(inverted, cards[i+1])
		}
		inverted = append(inverted, cards[i])
	}
	return inverted
}

func splitCardSegments(cards []models.Card) []models.CardTemplateSegment {
	cardSegments := make([]models.CardTemplateSegment, 0)
	const currentCards = 0
	for i := 0; i < len(cards); i += 10 {
		segmentLength := 10
		if len(cards)-i < 10 {
			segmentLength = len(cards) - i
		}
		segment := cards[i : i+segmentLength]
		if segmentLength%2 != 0 {
			segment = append(segment, models.Card{
				ID:      0,
				Enabled: false,
				Runner:  models.Runner{},
				Code:    "",
			})
		}
		cardSegments = append(cardSegments, models.CardTemplateSegment{
			Cards:        segment,
			CardsSwapped: invertCardArrayItemPairs(segment),
		})
	}
	return cardSegments
}