feat(参照标准): 规范资源处理，完善版本编辑

ofdgo_version_extract.go

@@ -0,0 +1,140 @@
+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// 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 ofdgo
+
+import (
+	"archive/zip"
+	"fmt"
+)
+
+// ExtractVersion 将当前文档的指定版本提取为独立阅读器，可继续编辑或另存，不改变原包
+// 仅保留版本文件清单中的文件并重建单文档入口，不保留版本列表；原签名可能因入口变化而失效
+// 文件内容按需读取，使用期间不得关闭持有输入文件的原阅读器；返回值不关闭输入文件
+// 入参: id 版本标识，空值选择唯一的Current版本，没有默认版本或存在歧义时返回错误
+// 返回: *Reader 版本阅读器, error 选择、读取或文件缺失错误
+func (r *Reader) ExtractVersion(id string) (*Reader, error) {
+	entries, err := r.documentVersionEntries()
+	if err != nil {
+		return nil, err
+	}
+	var selected *DocumentVersionInfo
+	for i := range entries {
+		entry := &entries[i]
+		if id != "" && entry.ID == id || id == "" && entry.Current {
+			if selected != nil {
+				return nil, fmt.Errorf("multiple current document versions")
+			}
+			selected = entry
+		}
+	}
+	if selected == nil {
+		if id == "" {
+			return nil, fmt.Errorf("no current document version")
+		}
+		return nil, fmt.Errorf("document version not found: %s", id)
+	}
+	version, err := r.readDocumentVersion(selected.ID, selected.Location)
+	if err != nil {
+		return nil, fmt.Errorf("version %s: %w", selected.ID, err)
+	}
+	files := make(map[string]bool, len(version.Files))
+	for _, file := range version.Files {
+		if !r.fileNames[file.Location] {
+			return nil, fmt.Errorf("version %s file not found: %s", selected.ID, file.Location)
+		}
+		files[file.Location] = true
+	}
+	root, err := r.extractedVersionRoot(version, files)
+	if err != nil {
+		return nil, err
+	}
+	next := &Reader{Path: r.Path, files: map[string][]byte{"OFD.xml": root}, encryption: r.encryption}
+	for name := range files {
+		if name != "OFD.xml" {
+			if data, ok := r.files[name]; ok {
+				next.files[name] = data
+			}
+		}
+	}
+	if r.Zip != nil {
+		next.Zip = &zip.Reader{Comment: r.Zip.Comment}
+		for _, file := range r.Zip.File {
+			name := cleanPackagePath(file.Name)
+			if name != "OFD.xml" && files[name] && !file.FileInfo().IsDir() {
+				next.Zip.File = append(next.Zip.File, file)
+			}
+		}
+	}
+	if err := next.initRoot(); err != nil {
+		return nil, err
+	}
+	if _, err := next.docStructure(); err != nil {
+		return nil, err
+	}
+	return next, nil
+}
+
+// extractedVersionRoot 重建版本副本入口，保留元数据及命名空间，移除其他文档与版本列表
+// 入参: version 版本描述, files 版本包含的文件
+// 返回: []byte 主入口XML, error 读取或结构错误
+func (r *Reader) extractedVersionRoot(version DocumentVersionInfo, files map[string]bool) ([]byte, error) {
+	data, err := r.readFile("OFD.xml")
+	if err != nil {
+		return nil, err
+	}
+	root, err := parseEditorXML(data)
+	if err != nil {
+		return nil, err
+	}
+	body := root.childAt("DocBody", r.documentIndex)
+	if body == nil || body.child("DocRoot") == nil {
+		return nil, fmt.Errorf("document entry not found: %d", r.documentIndex)
+	}
+	var patches []editorXMLPatch
+	for _, child := range root.children {
+		if child.matchesOFD("DocBody") && child != body {
+			patches = append(patches, editorXMLPatch{start: child.start, end: child.end})
+		}
+	}
+	entry := body.child("DocRoot")
+	patches = append(patches, editorXMLContent(data, entry, editorFontXMLText(version.DocRoot)))
+	if versions := body.child("Versions"); versions != nil {
+		patches = append(patches, editorXMLPatch{start: versions.start, end: versions.end})
+	}
+	references := []*editorXML{body.child("Signatures")}
+	if info := body.child("DocInfo"); info != nil {
+		references = append(references, info.child("Cover"))
+	}
+	for _, node := range references {
+		if node == nil {
+			continue
+		}
+		name := resolveResourcePath("OFD.xml", "", editorImportText(data, node))
+		if files[name] {
+			patches = append(patches, editorXMLContent(data, node, editorFontXMLText("/"+name)))
+		} else {
+			patches = append(patches, editorXMLPatch{start: node.start, end: node.end})
+		}
+	}
+	data = editorPatchXML(data, patches)
+	if version.Version != "" {
+		root, err = parseEditorXML(data)
+		if err != nil {
+			return nil, err
+		}
+		data, err = editorXMLAttribute(data, root, "Version", version.Version)
+	}
+	return data, err
+}