Added front-matter handler

pkg/yqlib/front_matter.go

@@ -0,0 +1,96 @@
+package yqlib
+
+import (
+	"bufio"
+	"io"
+	"os"
+)
+
+type frontMatterHandler interface {
+	Split() error
+	GetYamlFrontMatterFilename() string
+	GetContentFilename() string
+	CleanUp()
+}
+
+type frontMatterHandlerImpl struct {
+	originalFilename        string
+	yamlFrontMatterFilename string
+	contentFilename         string
+}
+
+func NewFrontMatterHandler(originalFilename string) frontMatterHandler {
+	return &frontMatterHandlerImpl{originalFilename, "", ""}
+}
+
+func (f *frontMatterHandlerImpl) GetYamlFrontMatterFilename() string {
+	return f.yamlFrontMatterFilename
+}
+
+func (f *frontMatterHandlerImpl) GetContentFilename() string {
+	return f.contentFilename
+}
+
+func (f *frontMatterHandlerImpl) CleanUp() {
+	tryRemoveFile(f.yamlFrontMatterFilename)
+	tryRemoveFile(f.contentFilename)
+}
+
+// Splits the given file by yaml front matter
+// yaml content will be saved to first temporary file
+// remaining content will be saved to second temporary file
+func (f *frontMatterHandlerImpl) Split() error {
+	var reader io.Reader
+	var err error
+	if f.originalFilename == "-" {
+		reader = bufio.NewReader(os.Stdin)
+	} else {
+		reader, err = os.Open(f.originalFilename) // #nosec
+		if err != nil {
+			return err
+		}
+	}
+
+	yamlTempFile, err := createTempFile()
+	if err != nil {
+		return err
+	}
+	f.yamlFrontMatterFilename = yamlTempFile.Name()
+	log.Debug("yamlTempFile: %v", yamlTempFile.Name())
+
+	contentTempFile, err := createTempFile()
+	if err != nil {
+		return err
+	}
+	f.contentFilename = contentTempFile.Name()
+	log.Debug("contentTempFile: %v", contentTempFile.Name())
+
+	scanner := bufio.NewScanner(reader)
+
+	lineCount := 0
+	yamlContentBlock := true
+
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		if lineCount > 0 && line == "---" {
+			//we've finished reading the yaml content
+			yamlContentBlock = false
+		}
+		if yamlContentBlock {
+			_, err = yamlTempFile.Write([]byte(line + "\n"))
+		} else {
+			_, err = contentTempFile.Write([]byte(line + "\n"))
+		}
+		if err != nil {
+			return err
+		}
+		lineCount = lineCount + 1
+	}
+
+	safelyCloseFile(yamlTempFile)
+	safelyCloseFile(contentTempFile)
+
+	return scanner.Err()
+
+}