package pdfcert

import (
	"bytes"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/phpdave11/gofpdf"
	qrcode "github.com/skip2/go-qrcode"
)

// Minimal fallback when Node/jsPDF is unavailable.
func buildFallbackGofpdf(in Input, docName, created, scope, merkle, lookup string) ([]byte, error) {
	pdf := gofpdf.New("P", "pt", "Letter", "")
	pdf.SetCompression(false)
	pdf.SetMargins(48, 48, 48)
	pdf.SetAutoPageBreak(false, 0)
	pdf.AddPage()
	pageW, pageH := pdf.GetPageSize()
	margin := 48.0

	pdf.SetDrawColor(42, 24, 56)
	pdf.SetLineWidth(2)
	pdf.Rect(28, 28, pageW-56, pageH-56, "D")
	pdf.SetDrawColor(196, 168, 90)
	pdf.SetLineWidth(0.6)
	pdf.Rect(34, 34, pageW-68, pageH-68, "D")

	if p, cleanup, err := materializeLogo(); err == nil {
		pdf.ImageOptions(p, margin, 48, 120, 36, false, gofpdf.ImageOptions{ImageType: "PNG", ReadDpi: true}, 0, "")
		if cleanup != nil {
			defer cleanup()
		}
	}

	pdf.SetTextColor(42, 24, 56)
	pdf.SetFont("Times", "B", 18)
	pdf.SetXY(margin, 100)
	pdf.CellFormat(pageW-margin*2, 20, "Verae Timestamp Registration Document", "", 0, "C", false, 0, "")

	pdf.SetTextColor(90, 80, 100)
	pdf.SetFont("Helvetica", "", 10)
	pdf.SetXY(margin, 122)
	pdf.CellFormat(pageW-margin*2, 12, "Official certificate of digital content registration on the VeraeTime global ledger", "", 0, "C", false, 0, "")

	pdf.SetDrawColor(196, 168, 90)
	pdf.SetLineWidth(1)
	pdf.Line(margin, 142, pageW-margin, 142)

	if created == "" {
		created = "—"
	}
	fields := [][2]string{
		{"Document name", docName},
		{"Content SHA-256", in.SHA256},
		{"Registration scope", scope},
		{"Original timestamp (UTC)", created},
		{"Receipt ID (CID)", orDash(in.ReceiptID)},
		{"Merkle / block hash", merkle},
		{"Ledger location", "VeraeTime global ledger - api.veraetime.net"},
		{"Blockchain explorer", "https://explorer.verae.ai/"},
		{"Public lookup URL", lookup},
	}
	if in.ByteLength > 0 {
		fields = append([][2]string{
			{"Document name", docName},
			{"Document size", fmt.Sprintf("%d bytes", in.ByteLength)},
		}, fields[1:]...)
	}

	isHTTP := func(s string) bool {
		return strings.HasPrefix(strings.ToLower(strings.TrimSpace(s)), "http://") ||
			strings.HasPrefix(strings.ToLower(strings.TrimSpace(s)), "https://")
	}

	y := 168.0
	for _, fv := range fields {
		pdf.SetFont("Helvetica", "B", 10)
		pdf.SetTextColor(42, 24, 56)
		pdf.SetXY(margin, y)
		pdf.Cell(pageW-margin*2, 12, fv[0])
		y += 14
		pdf.SetFont("Helvetica", "", 10)
		linkURL := ""
		if isHTTP(fv[1]) {
			linkURL = strings.TrimSpace(fv[1])
			pdf.SetTextColor(74, 46, 140)
		} else {
			pdf.SetTextColor(40, 40, 50)
		}
		for _, ln := range pdf.SplitLines([]byte(fv[1]), pageW-margin*2-10) {
			pdf.SetXY(margin, y)
			if linkURL != "" {
				pdf.CellFormat(pageW-margin*2-10, 12, string(ln), "", 0, "L", false, 0, linkURL)
			} else {
				pdf.Cell(pageW-margin*2-10, 12, string(ln))
			}
			y += 12
		}
		y += 10
		if y > pageH-220 {
			break
		}
	}

	if qrPNG, err := qrcode.Encode(lookup, qrcode.Medium, 280); err == nil {
		if qrFile, qclean, qerr := writeTempPNG(qrPNG); qerr == nil {
			qrSize := 110.0
			qrX := pageW - margin - qrSize
			qrY := pageH - margin - qrSize - 36
			pdf.ImageOptions(qrFile, qrX, qrY, qrSize, qrSize, false, gofpdf.ImageOptions{ImageType: "PNG"}, 0, "")
			pdf.LinkString(qrX, qrY, qrSize, qrSize, lookup)
			pdf.SetFont("Helvetica", "", 8)
			pdf.SetTextColor(74, 46, 140)
			pdf.SetXY(qrX, qrY+qrSize+4)
			pdf.CellFormat(qrSize, 10, "Scan to look up this registration", "", 0, "C", false, 0, lookup)
			if qclean != nil {
				defer qclean()
			}
		}
	}

	pdf.SetFont("Helvetica", "", 8)
	pdf.SetTextColor(90, 80, 100)
	pdf.SetXY(margin, pageH-64)
	pdf.MultiCell(pageW-margin*2-130, 10, "This document certifies that the SHA-256 digest above was registered with Verae. File bytes were not uploaded; only the digest was submitted.", "", "L", false)
	pdf.SetFont("Helvetica", "B", 9)
	pdf.SetTextColor(42, 24, 56)
	pdf.SetXY(margin, pageH-36)
	pdf.Cell(40, 12, "Verae | ")
	pdf.SetTextColor(74, 46, 140)
	pdf.CellFormat(55, 12, "verae.com", "", 0, "L", false, 0, "https://verae.com")
	pdf.SetTextColor(42, 24, 56)
	pdf.Cell(12, 12, " | ")
	pdf.SetTextColor(74, 46, 140)
	pdf.CellFormat(90, 12, "explorer.verae.ai", "", 0, "L", false, 0, "https://explorer.verae.ai/")

	var buf bytes.Buffer
	if err := pdf.Output(&buf); err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

func orDash(s string) string {
	if s == "" {
		return "—"
	}
	return s
}

func materializeLogo() (path string, cleanup func(), err error) {
	for _, c := range []string{
		filepath.Join("assets", "VeraeFullLogo.png"),
		"/Users/marchon/research/PrintToVeraeTimeStamp/assets/VeraeFullLogo.png",
	} {
		if st, e := os.Stat(c); e == nil && st.Size() > 0 {
			return c, nil, nil
		}
	}
	if len(embeddedLogo) == 0 {
		return "", nil, fmt.Errorf("logo not found")
	}
	return writeTempPNG(embeddedLogo)
}

func writeTempPNG(b []byte) (path string, cleanup func(), err error) {
	f, err := os.CreateTemp("", "verae-png-*.png")
	if err != nil {
		return "", nil, err
	}
	if _, err := f.Write(b); err != nil {
		f.Close()
		os.Remove(f.Name())
		return "", nil, err
	}
	f.Close()
	return f.Name(), func() { _ = os.Remove(f.Name()) }, nil
}