equal.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 model

import (
	"bytes"
	"fmt"
	"strings"

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

// EqualObjects returns true if two objects are equal in the context of given xrefTable.
// Some object and an indirect reference to it are treated as equal.
// Objects may in fact be object trees.
func EqualObjects(o1, o2 types.Object, xRefTable *XRefTable) (ok bool, err error) {

	//log.Debug.Printf("equalObjects: comparing %T with %T \n", o1, o2)

	ir1, ok := o1.(types.IndirectRef)
	if ok {
		ir2, ok := o2.(types.IndirectRef)
		if ok && ir1 == ir2 {
			return true, nil
		}
	}

	o1, err = xRefTable.Dereference(o1)
	if err != nil {
		return false, err
	}

	o2, err = xRefTable.Dereference(o2)
	if err != nil {
		return false, err
	}

	if o1 == nil {
		return o2 != nil, nil
	}

	o1Type := fmt.Sprintf("%T", o1)
	o2Type := fmt.Sprintf("%T", o2)
	//log.Debug.Printf("equalObjects: comparing dereferenced %s with %s \n", o1Type, o2Type)

	if o1Type != o2Type {
		return false, nil
	}

	switch o1.(type) {

	case types.Name, types.StringLiteral, types.HexLiteral,
		types.Integer, types.Float, types.Boolean:
		ok = o1 == o2

	case types.Dict:
		ok, err = equalDicts(o1.(types.Dict), o2.(types.Dict), xRefTable)

	case types.StreamDict:
		sd1 := o1.(types.StreamDict)
		sd2 := o2.(types.StreamDict)
		ok, err = EqualStreamDicts(&sd1, &sd2, xRefTable)

	case types.Array:
		ok, err = equalArrays(o1.(types.Array), o2.(types.Array), xRefTable)

	default:
		err = errors.Errorf("equalObjects: unhandled compare for type %s\n", o1Type)
	}

	return ok, err
}

func equalArrays(a1, a2 types.Array, xRefTable *XRefTable) (bool, error) {

	if len(a1) != len(a2) {
		return false, nil
	}

	for i, o1 := range a1 {

		ok, err := EqualObjects(o1, a2[i], xRefTable)
		if err != nil {
			return false, err
		}

		if !ok {
			return false, nil
		}
	}

	return true, nil
}

// EqualStreamDicts returns true if two stream dicts are equal and contain the same bytes.
func EqualStreamDicts(sd1, sd2 *types.StreamDict, xRefTable *XRefTable) (bool, error) {

	ok, err := equalDicts(sd1.Dict, sd2.Dict, xRefTable)
	if err != nil {
		return false, err
	}

	if !ok {
		return false, nil
	}

	if sd1.Raw == nil || sd2 == nil {
		return false, errors.New("pdfcpu: EqualStreamDicts: stream dict not loaded")
	}

	return bytes.Equal(sd1.Raw, sd2.Raw), nil
}

func equalFontNames(v1, v2 types.Object, xRefTable *XRefTable) (bool, error) {

	v1, err := xRefTable.Dereference(v1)
	if err != nil {
		return false, err
	}
	bf1, ok := v1.(types.Name)
	if !ok {
		return false, errors.Errorf("equalFontNames: type cast problem")
	}

	v2, err = xRefTable.Dereference(v2)
	if err != nil {
		return false, err
	}
	bf2 := v2.(types.Name)
	if !ok {
		return false, errors.Errorf("equalFontNames: type cast problem")
	}

	// Ignore fontname prefix
	i := strings.Index(string(bf1), "+")
	if i > 0 {
		bf1 = bf1[i+1:]
	}

	i = strings.Index(string(bf2), "+")
	if i > 0 {
		bf2 = bf2[i+1:]
	}

	//log.Debug.Printf("equalFontNames: bf1=%s fb2=%s\n", bf1, bf2)

	return bf1 == bf2, nil
}

func equalDicts(d1, d2 types.Dict, xRefTable *XRefTable) (bool, error) {

	//log.Debug.Printf("equalDicts: %v\n%v\n", d1, d2)

	if d1.Len() != d2.Len() {
		return false, nil
	}

	t1, t2 := d1.Type(), d2.Type()
	fontDicts := (t1 != nil && *t1 == "Font") && (t2 != nil && *t2 == "Font")

	for key, v1 := range d1 {

		v2, found := d2[key]
		if !found {
			//log.Debug.Printf("equalDict: return false, key=%s\n", key)
			return false, nil
		}

		// Special treatment for font dicts
		if fontDicts && (key == "BaseFont" || key == "FontName" || key == "Name") {

			ok, err := equalFontNames(v1, v2, xRefTable)
			if err != nil {
				//log.Debug.Printf("equalDict: return2 false, key=%s v1=%v\nv2=%v\n", key, v1, v2)
				return false, err
			}

			if !ok {
				//log.Debug.Printf("equalDict: return3 false, key=%s v1=%v\nv2=%v\n", key, v1, v2)
				return false, nil
			}

			continue
		}

		ok, err := EqualObjects(v1, v2, xRefTable)
		if err != nil {
			//log.Debug.Printf("equalDict: return4 false, key=%s v1=%v\nv2=%v\n%v\n", key, v1, v2, err)
			return false, err
		}

		if !ok {
			//log.Debug.Printf("equalDict: return5 false, key=%s v1=%v\nv2=%v\n", key, v1, v2)
			return false, nil
		}

	}

	//log.Debug.Println("equalDict: return true")

	return true, nil
}

// EqualFontDicts returns true, if two font dicts are equal.
func EqualFontDicts(fd1, fd2 types.Dict, xRefTable *XRefTable) (bool, error) {

	//log.Debug.Printf("EqualFontDicts: %v\n%v\n", fd1, fd2)

	if fd1 == nil {
		return fd2 == nil, nil
	}

	if fd2 == nil {
		return false, nil
	}

	ok, err := equalDicts(fd1, fd2, xRefTable)
	if err != nil {
		return false, err
	}

	return ok, nil
}