package sign

import (
	"strconv"
	"strings"
)

func (context *SignContext) createCatalog() (string, error) {
	var catalogBuilder strings.Builder

	// Start the catalog object
	catalogBuilder.WriteString(strconv.Itoa(int(context.CatalogData.ObjectId)) + " 0 obj\n")
	catalogBuilder.WriteString("<< /Type /Catalog")

	// (Optional; PDF 1.4) The version of the PDF specification to which
	// the document conforms (for example, 1.4) if later than the version
	// specified in the file’s header (see 7.5.2, "File header"). If the header
	// specifies a later version, or if this entry is absent, the document
	// shall conform to the version specified in the header. This entry
	// enables a PDF processor to update the version using an incremental
	// update; see 7.5.6, "Incremental updates".
	// The value of this entry shall be a name object, not a number, and
	// therefore shall be preceded by a SOLIDUS (2Fh) character (/) when
	// written in the PDF file (for example, /1.4).
	//
	// If an incremental upgrade requires a version that is higher than specified by the document.
	// if context.PDFReader.PDFVersion < "2.0" {
	// catalogBuilder.WriteString(" /Version /2.0")
	// }

	// Retrieve the root and check for necessary keys in one loop
	root := context.PDFReader.Trailer().Key("Root")
	rootPtr := root.GetPtr()
	context.CatalogData.RootString = strconv.Itoa(int(rootPtr.GetID())) + " " + strconv.Itoa(int(rootPtr.GetGen())) + " R"

	foundPages, foundNames := false, false
	for _, key := range root.Keys() {
		switch key {
		case "Pages":
			foundPages = true
		case "Names":
			foundNames = true
		}
		if foundPages && foundNames {
			break
		}
	}

	// Add Pages and Names references if they exist
	if foundPages {
		pages := root.Key("Pages").GetPtr()
		catalogBuilder.WriteString(" /Pages " + strconv.Itoa(int(pages.GetID())) + " " + strconv.Itoa(int(pages.GetGen())) + " R")
	}
	if foundNames {
		names := root.Key("Names").GetPtr()
		catalogBuilder.WriteString(" /Names " + strconv.Itoa(int(names.GetID())) + " " + strconv.Itoa(int(names.GetGen())) + " R")
	}

	// Start the AcroForm dictionary with /NeedAppearances
	catalogBuilder.WriteString(" /AcroForm << /Fields [")

	// Add existing signatures to the AcroForm dictionary
	for i, sig := range context.SignData.ExistingSignatures {
		if i > 0 {
			catalogBuilder.WriteString(" ")
		}
		catalogBuilder.WriteString(strconv.Itoa(int(sig.ObjectId)) + " 0 R")
	}

	// Add the visual signature field to the AcroForm dictionary
	if len(context.SignData.ExistingSignatures) > 0 {
		catalogBuilder.WriteString(" ")
	}
	catalogBuilder.WriteString(strconv.Itoa(int(context.VisualSignData.ObjectId)) + " 0 R")

	catalogBuilder.WriteString("]") // close Fields array

	catalogBuilder.WriteString(" /NeedAppearances false")

	// Signature flags (Table 225)
	//
	// Bit position 1: SignaturesExist
	// If set, the document contains at least one signature field. This
	// flag allows an interactive PDF processor to enable user
	// interface items (such as menu items or push-buttons) related to
	// signature processing without having to scan the entire
	// document for the presence of signature fields.
	//
	// Bit position 2: AppendOnly
	// If set, the document contains signatures that may be invalidated
	// if the PDF file is saved (written) in a way that alters its previous
	// contents, as opposed to an incremental update. Merely updating
	// the PDF file by appending new information to the end of the
	// previous version is safe (see H.7, "Updating example").
	// Interactive PDF processors may use this flag to inform a user
	// requesting a full save that signatures will be invalidated and
	// require explicit confirmation before continuing with the
	// operation.
	//
	// Set SigFlags and Permissions based on Signature Type
	switch context.SignData.Signature.CertType {
	case CertificationSignature, ApprovalSignature, TimeStampSignature:
		catalogBuilder.WriteString(" /SigFlags 3")
	case UsageRightsSignature:
		catalogBuilder.WriteString(" /SigFlags 1")
	}

	// Finalize the AcroForm and Catalog object
	catalogBuilder.WriteString(" >>")           // Close AcroForm
	catalogBuilder.WriteString(" >>\nendobj\n") // Close catalog object

	return catalogBuilder.String(), nil
}