package pdf

import (
	"context"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"time"

	"github.com/chromedp/cdproto/page"
	"github.com/chromedp/chromedp"
	"github.com/pdfcpu/pdfcpu/pkg/api"
)

// HTMLDocumentGenerator generates PDF documents from HTML templates using chromedp
type HTMLDocumentGenerator struct {
	outputDir string
}

// NewHTMLDocumentGenerator creates a new HTML-based document generator
func NewHTMLDocumentGenerator(outputDir string) *HTMLDocumentGenerator {
	return &HTMLDocumentGenerator{
		outputDir: outputDir,
	}
}

// GenerateInvoicePDF creates a PDF invoice from HTML template
// Returns (filename, error)
func (g *HTMLDocumentGenerator) GenerateInvoicePDF(data *InvoicePDFData) (string, error) {
	fmt.Println("=== HTML Generator: Starting invoice generation (two-pass with T&C page count) ===")

	// FIRST PASS: Generate PDF without page numbers to determine total pages (including T&C)
	fmt.Println("=== HTML Generator: First pass - generating without page count ===")
	html := g.BuildInvoiceHTML(data, 0, 0)

	fmt.Printf("=== HTML Generator: Generated %d bytes of HTML ===\n", len(html))

	tempHTML := filepath.Join(g.outputDir, "temp_invoice.html")
	if err := ioutil.WriteFile(tempHTML, []byte(html), 0644); err != nil {
		return "", fmt.Errorf("failed to write temp HTML: %w", err)
	}
	defer os.Remove(tempHTML)
	defer os.Remove(filepath.Join(g.outputDir, "invoice_logo.png")) // Clean up temp logo
	defer os.Remove(filepath.Join(g.outputDir, "temp_logo.png"))    // Clean up temp logo

	// Generate temp PDF
	tempPDFPath := filepath.Join(g.outputDir, "temp_invoice_first_pass.pdf")
	if err := g.htmlToPDF(tempHTML, tempPDFPath); err != nil {
		return "", fmt.Errorf("failed to convert HTML to PDF (first pass): %w", err)
	}

	// Get initial page count from invoice
	invoicePageCount, err := g.getPageCount(tempPDFPath)
	if err != nil {
		fmt.Printf("Warning: Could not extract invoice page count: %v\n", err)
		invoicePageCount = 1
	}

	// Check if T&C exists and merge to get total page count
	totalPageCount := invoicePageCount
	termsPath := filepath.Join(g.outputDir, "CMC_terms_and_conditions2006_A4.pdf")
	tempMergedPath := filepath.Join(g.outputDir, fmt.Sprintf("%s_merged_first_pass.pdf", data.Invoice.Title))

	if _, err := os.Stat(termsPath); err == nil {
		fmt.Println("=== HTML Generator: T&C found, merging to determine total pages ===")
		if err := MergePDFs(tempPDFPath, termsPath, tempMergedPath); err == nil {
			// Get total page count from merged PDF
			totalPageCount, err = g.getPageCount(tempMergedPath)
			if err != nil {
				fmt.Printf("Warning: Could not extract merged page count, using invoice count: %v\n", err)
				totalPageCount = invoicePageCount
			} else {
				fmt.Printf("=== HTML Generator: Total pages (invoice + T&C): %d ===\n", totalPageCount)
			}
		} else {
			fmt.Printf("Warning: Could not merge T&C for counting: %v\n", err)
		}
	}

	fmt.Printf("=== HTML Generator: First pass complete, detected %d total pages ===\n", totalPageCount)
	os.Remove(tempPDFPath)
	os.Remove(tempMergedPath)

	// SECOND PASS: Generate final PDF without page count in HTML (will be added via pdfcpu after merge)
	fmt.Println("=== HTML Generator: Second pass - regenerating final PDF ===")
	html = g.BuildInvoiceHTML(data, 0, 0)

	if err := ioutil.WriteFile(tempHTML, []byte(html), 0644); err != nil {
		return "", fmt.Errorf("failed to write temp HTML (second pass): %w", err)
	}

	// Generate final PDF filename using invoice number; fallback to a stable default
	invoiceNumber := ""
	if data.Document != nil {
		invoiceNumber = data.Document.CmcReference
	}
	filenameBase := invoiceNumber
	if filenameBase == "" {
		filenameBase = "CMC Invoice"
	}
	filename := fmt.Sprintf("%s.pdf", filenameBase)
	pdfPath := filepath.Join(g.outputDir, filename)
	fmt.Printf("=== HTML Generator: Invoice filename generation - invoiceNumber='%s', filenameBase='%s', final filename='%s' ===\n", invoiceNumber, filenameBase, filename)

	if err := g.htmlToPDF(tempHTML, pdfPath); err != nil {
		return "", fmt.Errorf("failed to convert HTML to PDF (second pass): %w", err)
	}

	fmt.Println("=== HTML Generator: PDF generation complete ===")

	// Merge with T&C PDF if it exists
	if _, err := os.Stat(termsPath); err == nil {
		fmt.Println("=== HTML Generator: Found T&C PDF, merging ===")
		tempMergedPath := filepath.Join(g.outputDir, fmt.Sprintf("%s_merged_temp.pdf", filenameBase))
		if err := MergePDFs(pdfPath, termsPath, tempMergedPath); err != nil {
			fmt.Printf("=== HTML Generator: Warning - could not merge T&C PDF: %v. Returning invoice without T&C.\n", err)
			return filename, nil
		}
		// Replace original with merged version
		if err := os.Rename(tempMergedPath, pdfPath); err != nil {
			fmt.Printf("=== HTML Generator: Warning - could not replace PDF: %v\n", err)
			return filename, err
		}
	}

	// Add page numbers to final PDF
	// TODO: Re-enable after fixing pdfcpu watermark API usage
	// fmt.Println("=== HTML Generator: Adding page numbers to final PDF ===")
	// if err := AddPageNumbers(pdfPath); err != nil {
	// 	fmt.Printf("=== HTML Generator: Warning - could not add page numbers: %v\n", err)
	// }

	return filename, nil
}

// GenerateQuotePDF creates a PDF quote from HTML template
// Returns (filename, error)
func (g *HTMLDocumentGenerator) GenerateQuotePDF(data *QuotePDFData) (string, error) {
	fmt.Println("=== HTML Generator: Starting quote generation (two-pass with T&C page count) ===")

	// FIRST PASS: Generate PDF without page numbers to determine total pages (including T&C)
	fmt.Println("=== HTML Generator: First pass - generating without page count ===")
	html := g.BuildQuoteHTML(data, 0, 0)

	fmt.Printf("=== HTML Generator: Generated %d bytes of HTML ===\n", len(html))

	tempHTML := filepath.Join(g.outputDir, "temp_quote.html")
	if err := ioutil.WriteFile(tempHTML, []byte(html), 0644); err != nil {
		return "", fmt.Errorf("failed to write temp HTML: %w", err)
	}
	defer os.Remove(tempHTML)
	defer os.Remove(filepath.Join(g.outputDir, "quote_logo.png")) // Clean up temp logo

	// Generate temp PDF
	tempPDFPath := filepath.Join(g.outputDir, "temp_quote_first_pass.pdf")
	if err := g.htmlToPDF(tempHTML, tempPDFPath); err != nil {
		return "", fmt.Errorf("failed to convert HTML to PDF (first pass): %w", err)
	}

	// Get initial page count from quote
	quotePageCount, err := g.getPageCount(tempPDFPath)
	if err != nil {
		fmt.Printf("Warning: Could not extract quote page count: %v\n", err)
		quotePageCount = 1
	}

	// Check if T&C exists and merge to get total page count
	totalPageCount := quotePageCount
	termsPath := filepath.Join(g.outputDir, "CMC_terms_and_conditions2006_A4.pdf")
	tempMergedPath := filepath.Join(g.outputDir, "temp_quote_merged_first_pass.pdf")

	if _, err := os.Stat(termsPath); err == nil {
		fmt.Println("=== HTML Generator: T&C found, merging to determine total pages ===")
		if err := MergePDFs(tempPDFPath, termsPath, tempMergedPath); err == nil {
			// Get total page count from merged PDF
			totalPageCount, err = g.getPageCount(tempMergedPath)
			if err != nil {
				fmt.Printf("Warning: Could not extract merged page count, using quote count: %v\n", err)
				totalPageCount = quotePageCount
			} else {
				fmt.Printf("=== HTML Generator: Total pages (quote + T&C): %d ===\n", totalPageCount)
			}
		} else {
			fmt.Printf("Warning: Could not merge T&C for counting: %v\n", err)
		}
	}

	fmt.Printf("=== HTML Generator: First pass complete, detected %d total pages ===\n", totalPageCount)
	os.Remove(tempPDFPath)
	os.Remove(tempMergedPath)

	// SECOND PASS: Generate final PDF without page count in HTML (will be added via pdfcpu after merge)
	fmt.Println("=== HTML Generator: Second pass - regenerating final PDF ===")
	html = g.BuildQuoteHTML(data, 0, 0)

	if err := ioutil.WriteFile(tempHTML, []byte(html), 0644); err != nil {
		return "", fmt.Errorf("failed to write temp HTML (second pass): %w", err)
	}

	// Generate final PDF filename using quote number
	quoteNumber := ""
	if data.Document != nil {
		log.Printf("=== HTML Generator: Document not nil, CmcReference='%s'", data.Document.CmcReference)
		quoteNumber = data.Document.CmcReference
		if quoteNumber == "" {
			// Strong fallback so we never emit a leading underscore filename
			quoteNumber = fmt.Sprintf("Quote-%d", data.Document.ID)
		}
		if data.Document.Revision > 0 {
			quoteNumber = fmt.Sprintf("%s_%d", quoteNumber, data.Document.Revision)
		}
	} else {
		log.Printf("=== HTML Generator: Document is nil!")
	}
	log.Printf("=== HTML Generator: Quote number before fallback: '%s', Document ID: %d, Revision: %d",
		quoteNumber, data.Document.ID, data.Document.Revision)
	filenameBase := quoteNumber
	if filenameBase == "" {
		log.Printf("=== HTML Generator: Using fallback filename")
		filenameBase = "CMC Quote"
	}
	log.Printf("=== HTML Generator: Final filename base: '%s'", filenameBase)
	filename := fmt.Sprintf("%s.pdf", filenameBase)
	pdfPath := filepath.Join(g.outputDir, filename)

	if err := g.htmlToPDF(tempHTML, pdfPath); err != nil {
		return "", fmt.Errorf("failed to convert HTML to PDF (second pass): %w", err)
	}

	fmt.Println("=== HTML Generator: PDF generation complete ===")

	// Merge with T&C PDF if it exists
	if _, err := os.Stat(termsPath); err == nil {
		fmt.Println("=== HTML Generator: Found T&C PDF, merging ===")
		tempMergedPath := filepath.Join(g.outputDir, fmt.Sprintf("%s_merged_temp.pdf", filenameBase))
		if err := MergePDFs(pdfPath, termsPath, tempMergedPath); err != nil {
			fmt.Printf("=== HTML Generator: Warning - could not merge T&C PDF: %v. Returning quote without T&C.\n", err)
			fmt.Printf("=== HTML Generator: Checking if pdfPath exists: %s\n", pdfPath)
			if stat, err := os.Stat(pdfPath); err == nil {
				fmt.Printf("=== HTML Generator: pdfPath exists, size=%d bytes\n", stat.Size())
			}
			return filename, nil
		}
		fmt.Printf("=== HTML Generator: Merge succeeded, replacing original PDF\n")
		// Replace original with merged version
		if err := os.Rename(tempMergedPath, pdfPath); err != nil {
			fmt.Printf("=== HTML Generator: Warning - could not replace PDF: %v\n", err)
			fmt.Printf("=== HTML Generator: tempMergedPath: %s\n", tempMergedPath)
			fmt.Printf("=== HTML Generator: pdfPath: %s\n", pdfPath)
			return filename, err
		}
		fmt.Printf("=== HTML Generator: Replaced PDF successfully\n")

		// Verify the final file exists
		if stat, err := os.Stat(pdfPath); err == nil {
			fmt.Printf("=== HTML Generator: Final PDF verified, size=%d bytes\n", stat.Size())
		} else {
			fmt.Printf("=== HTML Generator: ERROR - Final PDF does not exist after merge: %v\n", err)
			return filename, fmt.Errorf("final PDF does not exist: %w", err)
		}
	}

	// Add page numbers to final PDF
	// TODO: Re-enable after fixing pdfcpu watermark API usage
	// fmt.Println("=== HTML Generator: Adding page numbers to final PDF ===")
	// if err := AddPageNumbers(pdfPath); err != nil {
	// 	fmt.Printf("=== HTML Generator: Warning - could not add page numbers: %v\n", err)
	// }

	return filename, nil
}

// htmlToPDF converts an HTML file to PDF using chromedp
func (g *HTMLDocumentGenerator) htmlToPDF(htmlPath, pdfPath string) error {
	// Read the HTML file to get its content
	htmlContent, err := ioutil.ReadFile(htmlPath)
	if err != nil {
		return fmt.Errorf("failed to read HTML file: %w", err)
	}

	fmt.Printf("=== htmlToPDF: Read HTML file, size=%d bytes ===\n", len(htmlContent))

	// Create chromedp context
	opts := append(chromedp.DefaultExecAllocatorOptions[:],
		chromedp.Flag("headless", true),
		chromedp.Flag("disable-gpu", true),
		chromedp.Flag("no-sandbox", true),
		chromedp.Flag("disable-dev-shm-usage", true),
	)

	allocCtx, cancel := chromedp.NewExecAllocator(context.Background(), opts...)
	defer cancel()

	ctx, cancel := chromedp.NewContext(allocCtx)
	defer cancel()

	// Set timeout
	ctx, cancel = context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	// Navigate to file URL and print to PDF
	var pdfBuf []byte
	fileURL := "file://" + htmlPath

	fmt.Printf("=== htmlToPDF: Using file URL: %s ===\n", fileURL)
	fmt.Println("=== htmlToPDF: Starting chromedp navigation ===")

	if err := chromedp.Run(ctx,
		chromedp.Navigate(fileURL),
		chromedp.ActionFunc(func(ctx context.Context) error {
			fmt.Println("=== htmlToPDF: Executing PrintToPDF ===")
			var err error
			pdfBuf, _, err = page.PrintToPDF().
				WithPrintBackground(true).
				WithMarginTop(0).
				WithMarginBottom(0).
				WithMarginLeft(0).
				WithMarginRight(0).
				WithPaperWidth(8.27).   // A4 width in inches
				WithPaperHeight(11.69). // A4 height in inches
				Do(ctx)
			if err != nil {
				fmt.Printf("=== htmlToPDF: PrintToPDF error: %v ===\n", err)
			} else {
				fmt.Printf("=== htmlToPDF: PrintToPDF succeeded, PDF size=%d bytes ===\n", len(pdfBuf))
			}
			return err
		}),
	); err != nil {
		return fmt.Errorf("chromedp failed: %w", err)
	}

	// Write PDF to file
	if err := ioutil.WriteFile(pdfPath, pdfBuf, 0644); err != nil {
		return fmt.Errorf("failed to write PDF: %w", err)
	}

	return nil
}

// getPageCount extracts the page count from a PDF file
func (g *HTMLDocumentGenerator) getPageCount(pdfPath string) (int, error) {
	pageCount, err := api.PageCountFile(pdfPath)
	if err != nil {
		return 0, fmt.Errorf("failed to get page count: %w", err)
	}
	return pageCount, nil
}

// loadLogo loads the logo image and returns it as a relative path
func (g *HTMLDocumentGenerator) loadLogo(logoFileName string) string {
	// Use canonical path: /app/static/images in Docker, go/static/images locally
	logoPath := "/app/static/images/CMC-Mobile-Logo.png"
	if _, err := os.Stat(logoPath); err != nil {
		// Local development path
		logoPath = filepath.Join("go", "static", "images", "CMC-Mobile-Logo.png")
	}

	logoData, err := ioutil.ReadFile(logoPath)
	if err != nil {
		fmt.Printf("Warning: Could not read logo at %s: %v\n", logoPath, err)
		return ""
	}

	// Copy logo to output directory for chromedp to access
	destPath := filepath.Join(g.outputDir, logoFileName)
	if err := ioutil.WriteFile(destPath, logoData, 0644); err != nil {
		fmt.Printf("Warning: Could not write logo to output dir: %v\n", err)
		return ""
	}

	fmt.Printf("=== Copied logo from %s to %s ===\n", logoPath, destPath)
	// Return relative path (same directory as HTML file)
	return logoFileName
}