Allow user customization for slide themes

Closes #1.

This change allows users to add a configuration section to their slides,
which allows them to specify a different theme if they would like to
change the styles of the default theme.

A user can add
```
---
theme: ascii
---
```

To use an ascii theme or use `theme: ./styles.json` to specify their own
custom JSON theme using glamour styles.

Co-authored-by: Britton Hayes <brittonhayes@users.noreply.github.com>

.gitignore

@@ -1 +1,2 @@
 /slides
+.idea

cmd/root.go

@@ -12,7 +12,9 @@ import (
 	"time"
 
 	tea "github.com/charmbracelet/bubbletea"
+	"github.com/maaslalani/slides/internal/meta"
 	"github.com/maaslalani/slides/internal/model"
+	"github.com/maaslalani/slides/styles"
 	"github.com/spf13/cobra"
 )
 
@@ -47,11 +49,19 @@ var root = &cobra.Command{
 			return errors.New("could not get current user")
 		}
 
+		m, exists := meta.New().ParseHeader(slides[0])
+		// If the user specifies a custom configuration options
+		// skip the first "slide" since this is all configuration
+		if exists {
+			slides = slides[1:]
+		}
+
 		p := tea.NewProgram(model.Model{
 			Slides: slides,
 			Page:   0,
 			Author: user.Name,
 			Date:   time.Now().Format("2006-01-02"),
+			Theme:  styles.SelectTheme(m.Theme),
 		}, tea.WithAltScreen())
 
 		err = p.Start()

examples/ascii_slides.md

@@ -0,0 +1,56 @@
+---
+theme: ascii
+---
+
+# Welcome to Slides
+A terminal based presentation tool
+
+```go
+package main
+
+import "fmt"
+
+func main() {
+  fmt.Println("Written in Go!")
+}
+```
+
+---
+
+## Everything is markdown
+In fact this entire presentation is a markdown file
+
+---
+
+# h1
+## h2
+### h3
+#### h4
+##### h5
+###### h6
+
+# Markdown components
+You can use everything in markdown!
+* Like bulleted list
+* You know the deal
+
+1. Numbered lists too
+
+| Tables | Too    |
+| ------ | ------ |
+| Even   | Tables |
+
+---
+
+All you need to do is separate slides with triple dashes `---` on a separate line,
+like so:
+
+```markdown
+# Slide 1
+Some stuff
+
+--- 
+
+# Slide 2
+Some other stuff
+```

go.mod

@@ -3,9 +3,12 @@ module github.com/maaslalani/slides
 go 1.16
 
 require (
+	github.com/adrg/frontmatter v0.2.0
 	github.com/charmbracelet/bubbles v0.8.0
 	github.com/charmbracelet/bubbletea v0.14.0
 	github.com/charmbracelet/glamour v0.3.0
 	github.com/charmbracelet/lipgloss v0.2.1
 	github.com/spf13/cobra v1.1.3
+	github.com/stretchr/testify v1.7.0
+	gopkg.in/yaml.v2 v2.4.0
 )

go.sum

@@ -11,9 +11,12 @@ cloud.google.com/go/firestore v1.1.0/go.mod h1:ulACoGHTpvq5r8rxGJ4ddJZBZqakUQqCl
 cloud.google.com/go/pubsub v1.0.1/go.mod h1:R0Gpsv3s54REJCy4fxDixWD93lHJMoZTyQ2kNxGRt3I=
 cloud.google.com/go/storage v1.0.0/go.mod h1:IhtSnM/ZTZV8YYJWCY8RULGVqBDmpoyjwiyrjsg+URw=
 dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
+github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
+github.com/adrg/frontmatter v0.2.0 h1:/DgnNe82o03riBd1S+ZDjd43wAmC6W35q67NHeLkPd4=
+github.com/adrg/frontmatter v0.2.0/go.mod h1:93rQCj3z3ZlwyxxpQioRKC1wDLto4aXHrbqIsnH9wmE=
 github.com/alecthomas/assert v0.0.0-20170929043011-405dbfeb8e38 h1:smF2tmSOzy2Mm+0dGI2AIUHY+w0BUc+4tn40djz7+6U=
 github.com/alecthomas/assert v0.0.0-20170929043011-405dbfeb8e38/go.mod h1:r7bzyVFMNntcxPZXK3/+KdruV1H5KSlyVY0gc+NgInI=
 github.com/alecthomas/chroma v0.8.2 h1:x3zkuE2lUk/RIekyAJ3XRqSCP4zwWDfcw/YJCuCAACg=
@@ -58,6 +61,7 @@ github.com/cpuguy83/go-md2man/v2 v2.0.0/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsr
 github.com/danwakefield/fnmatch v0.0.0-20160403171240-cbb64ac3d964 h1:y5HC9v93H5EPKqaS1UYVg1uYah5Xf51mBfIoWehClUQ=
 github.com/danwakefield/fnmatch v0.0.0-20160403171240-cbb64ac3d964/go.mod h1:Xd9hchkHSWYkEqJwUGisez3G1QY8Ryz0sdWrLPMGjLk=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8PWV+bWy6jNmig1y/TA+kYO4g3RSRF0IAv0no=
@@ -130,8 +134,10 @@ github.com/kisielk/errcheck v1.1.0/go.mod h1:EZBBE59ingxPouuu3KfxchcWSUPOHkagtvW
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/lucasb-eyer/go-colorful v1.0.3/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
 github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=
@@ -176,6 +182,7 @@ github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINE
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/posener/complete v1.1.1/go.mod h1:em0nMJCgc9GFtwrmVmEMR/ZL6WyhyjMBndrE9hABlRI=
 github.com/prometheus/client_golang v0.9.1/go.mod h1:7SWBe2y4D6OKWSNQJUaRYU/AaXPKyh/dDVn+NZz0KFw=
@@ -216,6 +223,8 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/subosito/gotenv v1.2.0/go.mod h1:N0PQaV/YGNqwC0u51sEeR/aUtSLEXKX9iv69rRypqCw=
 github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5/go.mod h1:ncp9v5uamzpCO7NfCPTXjqaC+bZgJeR0sMTm6dMHP7U=
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
@@ -351,6 +360,7 @@ google.golang.org/grpc v1.20.1/go.mod h1:10oTOabMzJvdu6/UiuZezV6QK5dSlG84ov/aaiq
 google.golang.org/grpc v1.21.1/go.mod h1:oYelfM1adQP15Ek0mdvEgi9Df8B9CZIaU1084ijfRaM=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/ini.v1 v1.51.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
@@ -358,7 +368,11 @@ gopkg.in/resty.v1 v1.12.0/go.mod h1:mDo4pnntr5jdWRML875a/NmxYqAlA73dVijT2AXvQQo=
 gopkg.in/yaml.v2 v2.0.0-20170812160011-eb3733d160e7/go.mod h1:JAlM8MvJe8wmxCU4Bli9HhUf9+ttbYbLASfIpnQbh74=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190106161140-3f1c8253044a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190418001031-e561f6794a2a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

internal/file/file.go

@@ -0,0 +1,18 @@
+// Package file includes utility functions
+// for working with the filesystem
+package file
+
+import (
+	"os"
+)
+
+// Exists is a helper to verify
+// that the provided filepath exists
+// on the system
+func Exists(filepath string) bool {
+	info, err := os.Stat(filepath)
+	if os.IsNotExist(err) {
+		return false
+	}
+	return !info.IsDir()
+}

internal/file/file_test.go

@@ -0,0 +1,28 @@
+package file_test
+
+import (
+	"testing"
+
+	"github.com/maaslalani/slides/internal/file"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExists(t *testing.T) {
+	tests := []struct {
+		name     string
+		filepath string
+		want     bool
+	}{
+		{name: "Find file exists", filepath: "file.go", want: true},
+		{name: "Return false for missing file", filepath: "afilethatdoesntexist.go", want: false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			isExist := file.Exists(tt.filepath)
+			if isExist {
+				assert.FileExists(t, tt.filepath)
+			}
+			assert.Equal(t, tt.want, isExist)
+		})
+	}
+}

internal/meta/meta.go

@@ -0,0 +1,42 @@
+// Package meta implements markdown frontmatter parsing for simple
+// slides configuration
+package meta
+
+import (
+	"strings"
+
+	"github.com/adrg/frontmatter"
+	"gopkg.in/yaml.v2"
+)
+
+// Meta contains all of the data to be parsed
+// out of a markdown file's header section
+type Meta struct {
+	Theme string `yaml:"theme"`
+}
+
+// New creates a new instance of the
+// slideshow meta header object
+func New() *Meta {
+	return &Meta{}
+}
+
+// ParseHeader parses metadata from a slideshows header slide
+// including theme information
+//
+// If no front matter is provided, it will fallback to the default theme and
+// return false to acknowledge that there is no front matter in this slide
+func (m *Meta) ParseHeader(header string) (*Meta, bool) {
+	fallback := &Meta{Theme: "default"}
+	bytes, err := frontmatter.Parse(strings.NewReader(header), &m)
+	if err != nil {
+		return fallback, false
+	}
+
+	err = yaml.Unmarshal(bytes, &m)
+	if err != nil {
+		return fallback, false
+	}
+
+	return m, true
+}

internal/meta/meta_test.go

@@ -0,0 +1,72 @@
+package meta_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/maaslalani/slides/internal/meta"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMeta_ParseHeader(t *testing.T) {
+	tests := []struct {
+		name      string
+		slideshow string
+		want      *meta.Meta
+	}{
+		{
+			name:      "Parse theme from header",
+			slideshow: fmt.Sprintf("---\ntheme: %q\n", "dark"),
+			want: &meta.Meta{
+				Theme: "dark",
+			},
+		},
+		{
+			name:      "Fallback to default if no theme provided",
+			slideshow: "\n# Header Slide\n > Subtitle\n",
+			want: &meta.Meta{
+				Theme: "default",
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			m := &meta.Meta{}
+			got, hasMeta := m.ParseHeader(tt.slideshow)
+			if !hasMeta {
+				assert.NotNil(t, got)
+			}
+
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}
+
+func TestNew(t *testing.T) {
+	tests := []struct {
+		name string
+		want *meta.Meta
+	}{
+		{name: "Create meta struct", want: &meta.Meta{}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, meta.New(), tt.want)
+		})
+	}
+}
+
+func ExampleMeta_ParseHeader() {
+	header := `
+---
+theme: "dark"
+---
+`
+	// Parse the header from the markdown
+	// file
+	m, _ := meta.New().ParseHeader(header)
+
+	// Print the return theme
+	// meta
+	fmt.Println(m.Theme)
+}

internal/model/model.go

@@ -14,6 +14,7 @@ type Model struct {
 	Page     int
 	Author   string
 	Date     string
+	Theme    glamour.TermRendererOption
 	viewport viewport.Model
 }
 
@@ -42,12 +43,11 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			}
 		}
 	}
-
 	return m, nil
 }
 
 func (m Model) View() string {
-	r, _ := glamour.NewTermRenderer(glamour.WithStylesFromJSONBytes(styles.Theme), glamour.WithWordWrap(0))
+  r, _ := glamour.NewTermRenderer(m.Theme, glamour.WithWordWrap(0))
 	slide, err := r.Render(m.Slides[m.Page])
 	if err != nil {
 		slide = fmt.Sprintf("Error: Could not render markdown! (%v)", err)

styles/styles.go

@@ -1,9 +1,11 @@
+// Package styles implements the theming logic for slides
 package styles
 
 import (
+	_ "embed"
 	"strings"
 
-	_ "embed"
+	"github.com/charmbracelet/glamour"
 	"github.com/charmbracelet/lipgloss"
 )
 
@@ -19,6 +21,11 @@ var (
 	Status = lipgloss.NewStyle().Padding(1)
 )
 
+var (
+	//go:embed theme.json
+	DefaultTheme []byte
+)
+
 func JoinHorizontal(left, right string, width int) string {
 	length := lipgloss.Width(left + right)
 	if width < length {
@@ -37,5 +44,19 @@ func JoinVertical(top, bottom string, height int) string {
 	return top + fill + bottom
 }
 
-//go:embed theme.json
+// SelectTheme picks a glamour style config based
-var Theme []byte
+// on the theme provided in the markdown header
+func SelectTheme(theme string) glamour.TermRendererOption {
+	switch theme {
+	case "ascii":
+		return glamour.WithStyles(glamour.ASCIIStyleConfig)
+	case "light":
+		return glamour.WithStyles(glamour.LightStyleConfig)
+	case "dark":
+		return glamour.WithStyles(glamour.DarkStyleConfig)
+	case "notty":
+		return glamour.WithStyles(glamour.NoTTYStyleConfig)
+	default:
+		return glamour.WithStylesFromJSONBytes(DefaultTheme)
+	}
+}

styles/styles_test.go

@@ -0,0 +1,74 @@
+package styles_test
+
+import (
+	"testing"
+
+	"github.com/charmbracelet/glamour"
+	"github.com/charmbracelet/glamour/ansi"
+	"github.com/maaslalani/slides/styles"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSelectTheme(t *testing.T) {
+	tests := []struct {
+		name    string
+		theme   string
+		want    ansi.StyleConfig
+		wantErr bool
+	}{
+		{name: "Select dark theme", theme: "dark", want: glamour.DarkStyleConfig, wantErr: false},
+		{name: "Select light theme", theme: "light", want: glamour.LightStyleConfig, wantErr: false},
+		{name: "Select ascii theme", theme: "ascii", want: glamour.ASCIIStyleConfig, wantErr: false},
+		{name: "Select notty theme", theme: "notty", want: glamour.NoTTYStyleConfig, wantErr: false},
+		{name: "Select theme with error", theme: "notty", want: glamour.DarkStyleConfig, wantErr: true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Execute the theme selection and ensure
+			// it returns a non-nil theme
+			selectedTheme := styles.SelectTheme(tt.theme)
+			assert.NotNil(t, selectedTheme)
+
+			// Initialize renderers to compare output
+			gotRenderer, _ := glamour.NewTermRenderer(selectedTheme)
+			wantRenderer, _ := glamour.NewTermRenderer(glamour.WithStyles(tt.want))
+
+			// Render a the same string with two different
+			// renderers
+			gotOutput, _ := gotRenderer.Render(tt.name)
+			wantOutput, _ := wantRenderer.Render(tt.name)
+
+			// Inject exception to ensure a style that doesn't match
+			// it's associated string
+			if tt.wantErr {
+				assert.NotEqual(t, wantOutput, gotOutput)
+				return
+			}
+
+			// Ensure they both match
+			assert.Equal(t, wantOutput, gotOutput)
+		})
+	}
+}
+
+func TestSelectTheme_file(t *testing.T) {
+	tests := []struct {
+		name       string
+		theme      string
+		fileExists bool
+	}{
+		{name: "Select custom theme json", theme: "./theme.json", fileExists: true},
+		{name: "Use an invalid filepath", theme: "./someinvalidfile.toml", fileExists: false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Successfully return a theme if a file exists
+			assert.NotNil(t, styles.SelectTheme(tt.theme))
+
+			// Successfully return a theme if a file doesn't exist
+			if !tt.fileExists {
+				assert.NotNil(t, styles.SelectTheme(tt.theme))
+			}
+		})
+	}
+}