Auto detect line ending on startup

assets/template/reveal-markdown.tmpl

@@ -18,8 +18,8 @@
 <div class="reveal">
     <div class="slides">
         <section data-markdown="/content.md"
-                 data-separator="^{{ .Reveal.LineEnding -}}{{ .Reveal.HorizontalSeparator }}{{- .Reveal.LineEnding }}"
+                 data-separator="^{{ .Reveal.LineEnding.Escaped -}}{{ .Reveal.HorizontalSeparator }}{{- .Reveal.LineEnding.Escaped }}"
-                 data-separator-vertical="^{{ .Reveal.LineEnding -}}{{ .Reveal.VerticalSeparator }}{{- .Reveal.LineEnding }}"
+                 data-separator-vertical="^{{ .Reveal.LineEnding.Escaped -}}{{ .Reveal.VerticalSeparator }}{{- .Reveal.LineEnding.Escaped }}"
                  data-separator-notes="^Note:"
                  data-charset="iso-8859-15">
         </section>

go.sum

@@ -49,8 +49,6 @@ github.com/Masterminds/goutils v1.1.1 h1:5nUrii3FMTL5diU80unEVvNevw1nH4+ZV4DSLVJ
 github.com/Masterminds/goutils v1.1.1/go.mod h1:8cTjp+g8YejhMuvIA5y2vz3BpJxksy863GQaJW2MFNU=
 github.com/Masterminds/semver/v3 v3.1.1 h1:hLg3sBzpNErnxhQtUy/mmLR2I9foDujNK030IGemrRc=
 github.com/Masterminds/semver/v3 v3.1.1/go.mod h1:VPu/7SZ7ePZ3QOrcuXROw5FAcLl4a0cBrbBpGY/8hQs=
-github.com/Masterminds/sprig/v3 v3.2.1 h1:n6EPaDyLSvCEa3frruQvAiHuNp2dhBlMSmkEr+HuzGc=
-github.com/Masterminds/sprig/v3 v3.2.1/go.mod h1:UoaO7Yp8KlPnJIYWTFkMaqPUYKTfGFPhxNuwnnxkKlk=
 github.com/Masterminds/sprig/v3 v3.2.2 h1:17jRggJu518dr3QaafizSXOjKYp94wKfABxUmyxvxX8=
 github.com/Masterminds/sprig/v3 v3.2.2/go.mod h1:UoaO7Yp8KlPnJIYWTFkMaqPUYKTfGFPhxNuwnnxkKlk=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=

internal/app/rendering/const_other.go

@@ -1,8 +0,0 @@
-//go:build !windows
-// +build !windows
-
-package rendering
-
-const (
-	LineEnding string = "\\n"
-)

internal/app/rendering/const_windows.go

@@ -1,5 +0,0 @@
-package rendering
-
-const (
-	LineEnding string = "\\r\\n"
-)

internal/app/rendering/reveal_params.go

@@ -21,6 +21,8 @@ import (
 	"github.com/bmatcuk/doublestar/v2"
 	"github.com/imdario/mergo"
 	"github.com/spf13/viper"
+
+	"github.com/baez90/goveal/internal/encoding"
 )
 
 var defaultParams = RevealParams{
@@ -32,7 +34,6 @@ var defaultParams = RevealParams{
 	VerticalSeparator:     "---",
 	SlideNumberVisibility: "all",
 	SlideNumberFormat:     "h.v",
-	LineEnding:            LineEnding,
 	StyleSheets:           make([]string, 0),
 	FilesToMonitor:        make([]string, 0),
 }
@@ -49,7 +50,7 @@ type RevealParams struct {
 	StyleSheets           []string            `mapstructure:"stylesheets"`
 	FilesToMonitor        []string            `mapstructure:"filesToMonitor"`
 	WorkingDirectory      string              `mapstructure:"working-dir"`
-	LineEnding            string   `mapstructure:"-"`
+	LineEnding            encoding.LineEnding `mapstructure:"-"`
 }
 
 func (params *RevealParams) Load() error {

internal/app/server/http_server.go

@@ -5,27 +5,31 @@ import (
 	"io/fs"
 	"net"
 	"net/http"
+	"os"
 
 	"github.com/baez90/goveal/assets"
 	"github.com/baez90/goveal/internal/app/rendering"
 	"github.com/baez90/goveal/internal/app/routing"
+	"github.com/baez90/goveal/internal/encoding"
 )
 
 const (
 	markdownFilePath = "/content.md"
 )
 
-type Config struct {
+type (
+	Config struct {
 		Host         string
 		Port         uint16
 		MarkdownPath string
 		RevealParams *rendering.RevealParams
-}
+	}
 
-type HTTPServer struct {
+	HTTPServer struct {
 		listener net.Listener
 		handler  http.Handler
-}
+	}
+)
 
 func (srv HTTPServer) Serve() error {
 	return http.Serve(srv.listener, srv.handler)
@@ -37,6 +41,9 @@ func (srv HTTPServer) ListenAddress() string {
 
 func NewHTTPServer(config Config) (srv *HTTPServer, err error) {
 	noCacheFiles := append(config.RevealParams.FilesToMonitor, markdownFilePath)
+	if err := detectMarkdownFileEnding(config.MarkdownPath, config.RevealParams); err != nil {
+		return nil, err
+	}
 
 	router := &routing.RegexpRouter{}
 	var tmplRenderer rendering.RevealRenderer
@@ -92,3 +99,20 @@ func NewHTTPServer(config Config) (srv *HTTPServer, err error) {
 
 	return
 }
+
+func detectMarkdownFileEnding(filePath string, params *rendering.RevealParams) error {
+	f, err := os.Open(filePath)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		_ = f.Close()
+	}()
+
+	if le, err := encoding.Detect(f); err != nil {
+		return err
+	} else {
+		params.LineEnding = le
+	}
+	return nil
+}

internal/encoding/line_ending.go

@@ -0,0 +1,44 @@
+package encoding
+
+import (
+	"bufio"
+	"io"
+)
+
+const (
+	LineEndingUnknown LineEnding = ""
+	LineEndingWindows LineEnding = "\r\n"
+	LineEndingUnix    LineEnding = "\n"
+)
+
+type LineEnding string
+
+func (e LineEnding) String() string {
+	return string(e)
+}
+
+func (e LineEnding) Escaped() string {
+	switch e {
+	case LineEndingUnix:
+		return "\\n"
+	case LineEndingWindows:
+		return "\\r\\n"
+	default:
+		return ""
+	}
+}
+
+func Detect(reader io.Reader) (LineEnding, error) {
+	bufferedReader := bufio.NewReader(reader)
+	line, err := bufferedReader.ReadString(byte('\n'))
+	if err != nil {
+		return LineEndingUnknown, err
+	}
+
+	lineLength := len(line)
+	if lineLength <= 1 || line[lineLength-2:] != LineEndingWindows.String() {
+		return LineEndingUnix, nil
+	}
+
+	return LineEndingWindows, nil
+}

internal/encoding/line_ending_test.go

@@ -0,0 +1,74 @@
+package encoding_test
+
+import (
+	"io"
+	"strings"
+	"testing"
+
+	"github.com/baez90/goveal/internal/encoding"
+)
+
+func TestDetect(t *testing.T) {
+	type args struct {
+		reader io.Reader
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    encoding.LineEnding
+		wantErr bool
+	}{
+		{
+			name: "Empty file expect unknown",
+			args: args{
+				reader: strings.NewReader(""),
+			},
+			want:    encoding.LineEndingUnknown,
+			wantErr: true,
+		},
+		{
+			name: "File with only Unix line ending",
+			args: args{
+				reader: strings.NewReader("\n"),
+			},
+			want:    encoding.LineEndingUnix,
+			wantErr: false,
+		},
+		{
+			name: "File with only Windows line ending",
+			args: args{
+				reader: strings.NewReader("\r\n"),
+			},
+			want:    encoding.LineEndingWindows,
+			wantErr: false,
+		},
+		{
+			name: "File with multiple lines - Unix file ending",
+			args: args{
+				reader: strings.NewReader("Hello, World\nThis comes from Unix!\n"),
+			},
+			want:    encoding.LineEndingUnix,
+			wantErr: false,
+		},
+		{
+			name: "File with multiple lines - Windows file ending",
+			args: args{
+				reader: strings.NewReader("Hello, World\r\nThis comes from Windows!\r\n"),
+			},
+			want:    encoding.LineEndingWindows,
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := encoding.Detect(tt.args.reader)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Detect() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("Detect() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}