form.go

/*
Copyright 2018 The pdfcpu Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package validate

import (
	"strconv"
	"strings"

	"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/model"
	"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/types"
	"github.com/pkg/errors"
)

// func validateSignatureDict(xRefTable *model.XRefTable, o pdf.Object) error {
//
// 	d, err := xRefTable.DereferenceDict(o)
// 	if err != nil || d == nil {
// 		return err
// 	}
//
// 	// Type, optional, name
// 	_, err = validateNameEntry(xRefTable, d, "signatureDict", "Type", OPTIONAL, model.V10, func(s string) bool { return s == "Sig" })
//
// 	// process signature dict fields.
//
// 	return err
// }

func validateAppearanceSubDict(xRefTable *model.XRefTable, d types.Dict) error {

	// dict of xobjects
	for _, o := range d {

		if xRefTable.ValidationMode == model.ValidationRelaxed {
			if d, ok := o.(types.Dict); ok && len(d) == 0 {
				continue
			}
		}

		err := validateXObjectStreamDict(xRefTable, o)
		if err != nil {
			return err
		}

	}

	return nil
}

func validateAppearanceDictEntry(xRefTable *model.XRefTable, o types.Object) error {

	// stream or dict
	// single appearance stream or subdict

	o, err := xRefTable.Dereference(o)
	if err != nil || o == nil {
		return err
	}

	switch o := o.(type) {

	case types.Dict:
		err = validateAppearanceSubDict(xRefTable, o)

	case types.StreamDict:
		err = validateXObjectStreamDict(xRefTable, o)

	default:
		err = errors.New("pdfcpu: validateAppearanceDictEntry: unsupported PDF object")

	}

	return err
}

func validateAppearanceDict(xRefTable *model.XRefTable, o types.Object) error {

	// see 12.5.5 Appearance Streams

	d, err := xRefTable.DereferenceDict(o)
	if err != nil || d == nil {
		return err
	}

	// Normal Appearance
	o, ok := d.Find("N")
	if !ok {
		if xRefTable.ValidationMode == model.ValidationStrict {
			return errors.New("pdfcpu: validateAppearanceDict: missing required entry \"N\"")
		}
	} else {
		err = validateAppearanceDictEntry(xRefTable, o)
		if err != nil {
			return err
		}
	}

	// Rollover Appearance
	if o, ok = d.Find("R"); ok {
		err = validateAppearanceDictEntry(xRefTable, o)
		if err != nil {
			return err
		}
	}

	// Down Appearance
	if o, ok = d.Find("D"); ok {
		err = validateAppearanceDictEntry(xRefTable, o)
		if err != nil {
			return err
		}
	}

	return nil
}

func validateDA(s string) bool {
	// A sequence of valid page-content graphics or text state operators.
	// At a minimum, the string shall include a Tf (text font) operator along with its two operands, font and size.
	da := strings.Fields(s)
	for i := 0; i < len(da); i++ {
		if da[i] == "Tf" {
			if i < 2 {
				return false
			}
			if da[i-2][0] != '/' {
				return false
			}
			fontID := da[i-2][1:]
			if len(fontID) == 0 {
				return false
			}
			if _, err := strconv.ParseFloat(da[i-1], 64); err != nil {
				return false
			}
			continue
		}
		if da[i] == "rg" {
			if i < 3 {
				return false
			}
			if _, err := strconv.ParseFloat(da[i-3], 32); err != nil {
				return false
			}
			if _, err := strconv.ParseFloat(da[i-2], 32); err != nil {
				return false
			}
			if _, err := strconv.ParseFloat(da[i-1], 32); err != nil {
				return false
			}
		}
		if da[i] == "g" {
			if i < 1 {
				return false
			}
			if _, err := strconv.ParseFloat(da[i-1], 32); err != nil {
				return false
			}
		}
	}

	return true
}

func validateDARelaxed(s string) bool {
	// A sequence of valid page-content graphics or text state operators.
	// At a minimum, the string shall include a Tf (text font) operator along with its two operands, font and size.
	da := strings.Fields(s)
	for i := 0; i < len(da); i++ {
		if da[i] == "Tf" {
			if i < 2 {
				return false
			}
			if da[i-2][0] != '/' {
				return false
			}
			//fontID := da[i-2][1:]
			// if len(fontID) == 0 {
			// 	return false
			// }
			if _, err := strconv.ParseFloat(da[i-1], 64); err != nil {
				return false
			}
			continue
		}
		if da[i] == "rg" {
			if i < 3 {
				return false
			}
			if _, err := strconv.ParseFloat(da[i-3], 32); err != nil {
				return false
			}
			if _, err := strconv.ParseFloat(da[i-2], 32); err != nil {
				return false
			}
			if _, err := strconv.ParseFloat(da[i-1], 32); err != nil {
				return false
			}
		}
		if da[i] == "g" {
			if i < 1 {
				return false
			}
			if _, err := strconv.ParseFloat(da[i-1], 32); err != nil {
				return false
			}
		}
	}

	return true
}

func validateFormFieldDA(xRefTable *model.XRefTable, d types.Dict, dictName string, terminalNode bool, outFieldType *types.Name, requiresDA bool) (bool, error) {
	validate := validateDA
	if xRefTable.ValidationMode == model.ValidationRelaxed {
		validate = validateDARelaxed
	}
	if terminalNode && (*outFieldType).Value() == "Tx" {
		da, err := validateStringEntry(xRefTable, d, dictName, "DA", terminalNode && requiresDA, model.V10, validate)
		if err != nil {
			return false, err
		}
		if xRefTable.ValidationMode == model.ValidationRelaxed && da != nil {
			// Repair
			d["DA"] = types.StringLiteral(*da)
		}

		return da != nil && *da != "", nil
	}

	return false, nil
}

func validateFormFieldDictEntries(xRefTable *model.XRefTable, d types.Dict, terminalNode bool, inFieldType *types.Name, requiresDA bool) (outFieldType *types.Name, hasDA bool, err error) {

	dictName := "formFieldDict"

	// FT: name, Btn,Tx,Ch,Sig
	validate := func(s string) bool { return types.MemberOf(s, []string{"Btn", "Tx", "Ch", "Sig"}) }
	fieldType, err := validateNameEntry(xRefTable, d, dictName, "FT", terminalNode && inFieldType == nil, model.V10, validate)
	if err != nil {
		return nil, false, err
	}

	outFieldType = inFieldType
	if fieldType != nil {
		outFieldType = fieldType
	}

	// Parent, required if this is a child in the field hierarchy.
	_, err = validateIndRefEntry(xRefTable, d, dictName, "Parent", OPTIONAL, model.V10)
	if err != nil {
		return nil, false, err
	}

	// T, optional, text string
	_, err = validateStringEntry(xRefTable, d, dictName, "T", OPTIONAL, model.V10, nil)
	if err != nil {
		return nil, false, err
	}

	// TU, optional, text string, since V1.3
	_, err = validateStringEntry(xRefTable, d, dictName, "TU", OPTIONAL, model.V13, nil)
	if err != nil {
		return nil, false, err
	}

	// TM, optional, text string, since V1.3
	_, err = validateStringEntry(xRefTable, d, dictName, "TM", OPTIONAL, model.V13, nil)
	if err != nil {
		return nil, false, err
	}

	// Ff, optional, integer
	_, err = validateIntegerEntry(xRefTable, d, dictName, "Ff", OPTIONAL, model.V10, nil)
	if err != nil {
		return nil, false, err
	}

	// V, optional, various
	_, err = validateEntry(xRefTable, d, dictName, "V", OPTIONAL, model.V10)
	if err != nil {
		return nil, false, err
	}

	// DV, optional, various
	_, err = validateEntry(xRefTable, d, dictName, "DV", OPTIONAL, model.V10)
	if err != nil {
		return nil, false, err
	}

	// AA, optional, dict, since V1.2
	err = validateAdditionalActions(xRefTable, d, dictName, "AA", OPTIONAL, model.V12, "fieldOrAnnot")
	if err != nil {
		return nil, false, err
	}

	// DA, required for text fields, since ?
	// The default appearance string containing a sequence of valid page-content graphics or text state operators that define such properties as the field’s text size and colour.
	hasDA, err = validateFormFieldDA(xRefTable, d, dictName, terminalNode, outFieldType, requiresDA)

	return outFieldType, hasDA, err
}

func validateFormFieldParts(xRefTable *model.XRefTable, d types.Dict, inFieldType *types.Name, requiresDA bool) error {
	// dict represents a terminal field and must have Subtype "Widget"
	if _, err := validateNameEntry(xRefTable, d, "formFieldDict", "Subtype", REQUIRED, model.V10, func(s string) bool { return s == "Widget" }); err != nil {
		return err
	}

	// Validate field dict entries.
	if _, _, err := validateFormFieldDictEntries(xRefTable, d, true, inFieldType, requiresDA); err != nil {
		return err
	}

	// Validate widget annotation - Validation of AA redundant because of merged acrofield with widget annotation.
	_, err := validateAnnotationDict(xRefTable, d)
	return err
}

func validateFormFieldKids(xRefTable *model.XRefTable, d types.Dict, o types.Object, inFieldType *types.Name, requiresDA bool) error {
	var err error
	// dict represents a non terminal field.
	if d.Subtype() != nil && *d.Subtype() == "Widget" {
		return errors.New("pdfcpu: validateFormFieldKids: non terminal field can not be widget annotation")
	}

	// Validate field entries.
	var xInFieldType *types.Name
	var hasDA bool
	if xInFieldType, hasDA, err = validateFormFieldDictEntries(xRefTable, d, false, inFieldType, requiresDA); err != nil {
		return err
	}
	if requiresDA && hasDA {
		requiresDA = false
	}

	// Recurse over kids.
	a, err := xRefTable.DereferenceArray(o)
	if err != nil || a == nil {
		return err
	}

	for _, value := range a {
		ir, ok := value.(types.IndirectRef)
		if !ok {
			return errors.New("pdfcpu: validateFormFieldKids: corrupt kids array: entries must be indirect reference")
		}
		valid, err := xRefTable.IsValid(ir)
		if err != nil {
			return err
		}

		if !valid {
			if err = validateFormFieldDict(xRefTable, ir, xInFieldType, requiresDA); err != nil {
				return err
			}
		}
	}

	return nil
}

func validateFormFieldDict(xRefTable *model.XRefTable, ir types.IndirectRef, inFieldType *types.Name, requiresDA bool) error {
	d, err := xRefTable.DereferenceDict(ir)
	if err != nil || d == nil {
		return err
	}

	if xRefTable.ValidationMode == model.ValidationRelaxed {
		if len(d) == 0 {
			return nil
		}
	}

	if err := xRefTable.SetValid(ir); err != nil {
		return err
	}

	if o, ok := d.Find("Kids"); ok {
		return validateFormFieldKids(xRefTable, d, o, inFieldType, requiresDA)
	}

	return validateFormFieldParts(xRefTable, d, inFieldType, requiresDA)
}

func validateFormFields(xRefTable *model.XRefTable, o types.Object, requiresDA bool) error {

	a, err := xRefTable.DereferenceArray(o)
	if err != nil || len(a) == 0 {
		return err
	}

	for _, value := range a {

		ir, ok := value.(types.IndirectRef)
		if !ok {
			return errors.New("pdfcpu: validateFormFields: corrupt form field array entry")
		}

		valid, err := xRefTable.IsValid(ir)
		if err != nil {
			return err
		}

		if !valid {
			if err = validateFormFieldDict(xRefTable, ir, nil, requiresDA); err != nil {
				return err
			}
		}

	}

	return nil
}

func validateFormCO(xRefTable *model.XRefTable, o types.Object, sinceVersion model.Version, requiresDA bool) error {

	// see 12.6.3 Trigger Events
	// Array of indRefs to field dicts with calculation actions, since V1.3

	// Version check
	err := xRefTable.ValidateVersion("AcroFormCO", sinceVersion)
	if err != nil {
		return err
	}

	return validateFormFields(xRefTable, o, requiresDA)
}

func validateFormXFA(xRefTable *model.XRefTable, d types.Dict, sinceVersion model.Version) error {

	// see 12.7.8

	o, ok := d.Find("XFA")
	if !ok {
		return nil
	}

	// streamDict or array of text,streamDict pairs

	o, err := xRefTable.Dereference(o)
	if err != nil || o == nil {
		return err
	}

	switch o := o.(type) {

	case types.StreamDict:
		// no further processing

	case types.Array:

		i := 0

		for _, v := range o {

			if v == nil {
				return errors.New("pdfcpu: validateFormXFA: array entry is nil")
			}

			o, err := xRefTable.Dereference(v)
			if err != nil {
				return err
			}

			if i%2 == 0 {

				_, ok := o.(types.StringLiteral)
				if !ok {
					return errors.New("pdfcpu: validateFormXFA: even array must be a string")
				}

			} else {

				_, ok := o.(types.StreamDict)
				if !ok {
					return errors.New("pdfcpu: validateFormXFA: odd array entry must be a streamDict")
				}

			}

			i++
		}

	default:
		return errors.New("pdfcpu: validateFormXFA: needs to be streamDict or array")
	}

	return xRefTable.ValidateVersion("AcroFormXFA", sinceVersion)
}

func validateQ(i int) bool { return i >= 0 && i <= 2 }

func validateFormEntryCO(xRefTable *model.XRefTable, d types.Dict, sinceVersion model.Version, requiresDA bool) error {

	o, ok := d.Find("CO")
	if !ok {
		return nil
	}

	return validateFormCO(xRefTable, o, sinceVersion, requiresDA)
}

func validateFormEntryDR(xRefTable *model.XRefTable, d types.Dict) error {

	o, ok := d.Find("DR")
	if !ok {
		return nil
	}

	_, err := validateResourceDict(xRefTable, o)

	return err
}

func validateForm(xRefTable *model.XRefTable, rootDict types.Dict, required bool, sinceVersion model.Version) error {

	// => 12.7.2 Interactive Form Dictionary

	d, err := validateDictEntry(xRefTable, rootDict, "rootDict", "AcroForm", OPTIONAL, sinceVersion, nil)
	if err != nil || d == nil {
		return err
	}

	// Version check
	if err = xRefTable.ValidateVersion("AcroForm", sinceVersion); err != nil {
		return err
	}

	// Fields, required, array of indirect references
	o, ok := d.Find("Fields")
	if !ok {
		// Fix empty AcroForm dict.
		rootDict.Delete("AcroForm")
		return nil
	}

	xRefTable.Form = d

	dictName := "acroFormDict"

	// DA: optional, string
	validate := validateDA
	if xRefTable.ValidationMode == model.ValidationRelaxed {
		validate = validateDARelaxed
	}
	da, err := validateStringEntry(xRefTable, d, dictName, "DA", OPTIONAL, model.V10, validate)
	if err != nil {
		return err
	}
	if xRefTable.ValidationMode == model.ValidationRelaxed && da != nil {
		// Repair
		d["DA"] = types.StringLiteral(*da)
	}

	requiresDA := da == nil || len(*da) == 0

	err = validateFormFields(xRefTable, o, requiresDA)
	if err != nil {
		return err
	}

	// NeedAppearances: optional, boolean
	_, err = validateBooleanEntry(xRefTable, d, dictName, "NeedAppearances", OPTIONAL, model.V10, nil)
	if err != nil {
		return err
	}

	// SigFlags: optional, since 1.3, integer
	sinceV := model.V13
	if xRefTable.ValidationMode == model.ValidationRelaxed {
		sinceV = model.V12
	}
	sf, err := validateIntegerEntry(xRefTable, d, dictName, "SigFlags", OPTIONAL, sinceV, nil)
	if err != nil {
		return err
	}
	if sf != nil {
		i := sf.Value()
		xRefTable.SignatureExist = i&1 > 0
		xRefTable.AppendOnly = i&2 > 0
	}

	// CO: arra
	err = validateFormEntryCO(xRefTable, d, model.V13, requiresDA)
	if err != nil {
		return err
	}

	// DR, optional, resource dict
	err = validateFormEntryDR(xRefTable, d)
	if err != nil {
		return err
	}

	// Q: optional, integer
	_, err = validateIntegerEntry(xRefTable, d, dictName, "Q", OPTIONAL, model.V10, validateQ)
	if err != nil {
		return err
	}

	// XFA: optional, since 1.5, stream or array
	return validateFormXFA(xRefTable, d, sinceVersion)
}