feat(归并文件): 归并文件下沉通用能力

ofdgo_version_reader.go

@@ -15,6 +15,7 @@
 package ofdgo
 
 import (
+	"archive/zip"
 	"context"
 	"fmt"
 )
@@ -153,3 +154,157 @@ func (r *Reader) versionSignatures(location string) string {
 	}
 	return ""
 }
+
+// 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) {
+	return r.ExtractVersionContext(context.Background(), id)
+}
+
+// ExtractVersionContext 将指定版本提取为独立阅读器，扫描、读取和解析时响应取消
+// 文件保留范围、入口选择和输入文件生命周期与ExtractVersion相同，取消或失败不改变原包
+// 入参: ctx 取消上下文, id 版本标识，空值选择唯一的Current版本
+// 返回: *Reader 版本阅读器, error 选择、读取或取消错误
+func (r *Reader) ExtractVersionContext(ctx context.Context, id string) (*Reader, error) {
+	entries, err := r.documentVersionEntriesContext(ctx)
+	if err != nil {
+		return nil, err
+	}
+	var selected *DocumentVersionInfo
+	for i := range entries {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		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.readDocumentVersionContext(ctx, 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 err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		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(ctx, 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 err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		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 {
+			if err := ctx.Err(); err != nil {
+				return nil, err
+			}
+			name := cleanPackagePath(file.Name)
+			if name != "OFD.xml" && files[name] && !file.FileInfo().IsDir() {
+				next.Zip.File = append(next.Zip.File, file)
+			}
+		}
+	}
+	if err := next.initRootContext(ctx); err != nil {
+		return nil, err
+	}
+	if _, err := next.docStructureContext(ctx); 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: ctx 取消上下文, version 版本描述, files 版本包含的文件
+// 返回: []byte 主入口XML, error 读取、结构或取消错误
+func (r *Reader) extractedVersionRoot(ctx context.Context, version DocumentVersionInfo, files map[string]bool) ([]byte, error) {
+	data, err := r.readFileViewContext(ctx, "OFD.xml")
+	if err != nil {
+		return nil, err
+	}
+	root, err := parseEditorXMLContext(ctx, data)
+	if err != nil {
+		return nil, err
+	}
+	body := root.childAt("DocBody", r.documentIndex)
+	if body == nil {
+		return nil, fmt.Errorf("document entry not found: %d", r.documentIndex)
+	}
+	var patches []editorXMLPatch
+	for _, child := range root.children {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		if child.matchesOFD("DocBody") && child != body {
+			patches = append(patches, editorXMLPatch{start: child.start, end: child.end})
+		}
+	}
+	entry := body.child("DocRoot")
+	if entry != nil {
+		patches = append(patches, editorXMLContent(data, entry, editorFontXMLText(version.DocRoot)))
+	}
+	if versions := body.child("Versions"); versions != nil {
+		var replacement []byte
+		if entry == nil {
+			replacement = body.textXML("DocRoot", version.DocRoot)
+		}
+		patches = append(patches, editorXMLPatch{versions.start, versions.end, replacement})
+	} else if entry == nil {
+		return nil, fmt.Errorf("document entry not found: %d", r.documentIndex)
+	}
+	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 = parseEditorXMLContext(ctx, data)
+		if err != nil {
+			return nil, err
+		}
+		data, err = editorXMLAttribute(data, root, "Version", version.Version)
+	}
+	if err == nil {
+		err = ctx.Err()
+	}
+	return data, err
+}