cli: header and footer support

main.go

@@ -1,22 +1,31 @@
 package main
 
 import (
+	"flag"
 	"fmt"
+	"io/ioutil"
 	"os"
 
 	"git.r23s.eu/wojciech/gm2html/blockparser"
 )
 
 func main() {
-	if len(os.Args) != 3 {
+	flag.Usage = func() {
 		fmt.Println("usage:")
-		fmt.Printf("  %s input.gmi output.html\n", os.Args[0])
+		fmt.Printf("  %s [-header=path/to/header.html -footer=path/to/footer.html] input.gmi output.html\n", os.Args[0])
+	}
+	header := flag.String("header", "", "A path to a file, whose contents will be prepended to the output file.")
+	footer := flag.String("footer", "", "A path to a file, whose contents will be appended to the output file.")
+	flag.Parse()
+
+	if flag.NArg() != 2 {
+		flag.Usage()
 		os.Exit(-1)
 		return
 	}
 
-	inputPath := os.Args[1]
-	outputPath := os.Args[2]
+	inputPath := flag.Args()[0]
+	outputPath := flag.Args()[1]
 
 	inputFile, err := os.Open(inputPath)
 	if err != nil {
@@ -24,12 +33,52 @@ func main() {
 		os.Exit(-2)
 		return
 	}
+	defer inputFile.Close()
+
 	outputFile, err := os.Create(outputPath)
 	if err != nil {
 		fmt.Printf("Couldn't open the output file: %s\n", err.Error())
 		os.Exit(-2)
 		return
 	}
+	defer outputFile.Close()
+
+	var headerFile *os.File = nil
+	if *header != "" {
+		headerFile, err = os.Open(*header)
+		if err != nil {
+			fmt.Printf("Couldn't open the header file: %s\n", err.Error())
+			os.Exit(-2)
+			return
+		}
+		defer headerFile.Close()
+	}
+
+	var footerFile *os.File = nil
+	if *footer != "" {
+		footerFile, err = os.Open(*footer)
+		if err != nil {
+			fmt.Printf("Couldn't open the footer file: %s\n", err.Error())
+			os.Exit(-2)
+			return
+		}
+		defer footerFile.Close()
+	}
+
+	if headerFile != nil {
+		header, err := ioutil.ReadAll(headerFile)
+		if err != nil {
+			fmt.Printf("An error occured while reading the header: %s\n", err.Error())
+			os.Exit(-2)
+			return
+		}
+		_, err = outputFile.Write(header)
+		if err != nil {
+			fmt.Printf("An error occured while writing the header: %s\n", err.Error())
+			os.Exit(-2)
+			return
+		}
+	}
 
 	bp, err := blockparser.NewBlockParser(inputFile)
 	if err != nil {
@@ -46,12 +95,25 @@ func main() {
 			return
 		}
 		if block == nil {
-			inputFile.Close()
-			outputFile.Close()
-			return
+			break
 		}
 
 		fmt.Fprint(outputFile, block.RenderHTML())
 		fmt.Fprint(outputFile, "\n")
 	}
+
+	if footerFile != nil {
+		footer, err := ioutil.ReadAll(footerFile)
+		if err != nil {
+			fmt.Printf("An error occured while reading the footer: %s\n", err.Error())
+			os.Exit(-2)
+			return
+		}
+		_, err = outputFile.Write(footer)
+		if err != nil {
+			fmt.Printf("An error occured while writing the footer: %s\n", err.Error())
+			os.Exit(-2)
+			return
+		}
+	}
 }