transpiler handling rfc822 and yaml metadata

cmd/transpile/main.go

@@ -0,0 +1,136 @@
+package main
+
+import (
+	"gopkg.in/russross/blackfriday.v2"
+	"gopkg.in/yaml.v2"
+	"bufio"
+	"bytes"
+	"flag"
+	"fmt"
+	"log"
+	"io"
+	"os"
+	"net/mail"
+	"strings"
+)
+
+type Header struct {
+	Pre struct {
+		Authors []string
+	}
+	Answers []string
+	Post struct {
+		Objective string
+	}
+	Debug struct {
+		Log []string
+		Error string
+	}
+}
+
+type HeaderParser func([]byte) (*Header, error)
+
+func YamlParser(input []byte) (*Header, error) {
+	header := new(Header)
+	
+	err := yaml.Unmarshal(input, header)
+	if err != nil {
+		return nil, err
+	}
+	return header, nil
+}
+
+func Rfc822Parser(input []byte) (*Header, error) {
+	msgBytes := append(input, '\n')
+	r := bytes.NewReader(msgBytes)
+	m, err := mail.ReadMessage(r)
+	if err != nil {
+		return nil, err
+	}
+	
+	header := new(Header)
+	for key, val := range m.Header {
+		key = strings.ToLower(key)
+		switch key {
+			case "author":
+				header.Pre.Authors = val
+			case "answer":
+				header.Answers = val
+			default:
+				return nil, fmt.Errorf("Unknown header field: %s", key)
+		}
+	}
+
+	return header, nil
+}
+
+
+func parse(r io.Reader) (error) {
+	headerEnd := ""
+	headerBuf := new(bytes.Buffer)
+	headerParser := Rfc822Parser
+
+	scanner := bufio.NewScanner(r)
+	lineNo := 0
+	for scanner.Scan() {
+		line := scanner.Text()
+		lineNo += 1
+		if lineNo == 1 {
+			if line == "---" {
+				headerParser = YamlParser
+				headerEnd = "---"
+				continue
+			} else {
+				headerParser = Rfc822Parser
+			}
+		}
+		if line == headerEnd {
+			break
+		}
+		headerBuf.WriteString(line)
+		headerBuf.WriteRune('\n')
+	}
+	
+	bodyBuf := new(bytes.Buffer)
+	for scanner.Scan() {
+		line := scanner.Text()
+		lineNo += 1
+		bodyBuf.WriteString(line)
+		bodyBuf.WriteRune('\n')
+	}
+	
+	header, err := headerParser(headerBuf.Bytes())
+	if err != nil {
+		return err
+	}
+	
+	headerB, _ := yaml.Marshal(header)
+	bodyB := blackfriday.Run(bodyBuf.Bytes())
+	fmt.Println(string(headerB))
+	fmt.Println("")
+	fmt.Println(string(bodyB))
+
+	return nil
+}
+
+func main() {
+	flag.Parse()
+	
+	if flag.NArg() < 1 {
+		fmt.Fprintf(flag.CommandLine.Output(), "Error: no files to parse\n\n")
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+	
+	for _,filename := range flag.Args() {
+		f, err := os.Open(filename)
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer f.Close()
+		
+		if err := parse(f); err != nil {
+			log.Fatal(err)
+		}
+	}
+}