From 0263a643215f983030d52b03b79c43a0d56f92a6 Mon Sep 17 00:00:00 2001
From: celogeek <65178+celogeek@users.noreply.github.com>
Date: Wed, 26 Apr 2023 16:23:38 +0200
Subject: [PATCH] comments the code

---
 internal/converter/converter.go               |  39 +++++--
 internal/converter/converter_order.go         |  15 ++-
 .../converter/options/converter_options.go    |  25 ++--
 .../converter/profiles/converter_profiles.go  |   7 ++
 internal/epub/epub.go                         |  28 +++--
 .../epub/filters/epub_filters_autorotate.go   |   3 +
 .../epub/filters/epub_filters_cover_title.go  |   5 +
 internal/epub/filters/epub_filters_crop.go    |   5 +
 internal/epub/filters/epub_filters_pixel.go   |   6 +
 internal/epub/filters/epub_filters_resize.go  |   8 +-
 internal/epub/image/epub_image.go             |  20 +++-
 internal/epub/image/epub_image_filters.go     |   2 +
 internal/epub/image/epub_image_options.go     |   1 +
 internal/epub/imagedata/epub_image_data.go    |   6 +
 .../epub_image_processing.go                  |   9 +-
 .../epub_image_processing_helpers.go          |   3 +
 .../epub_image_processing_loader.go           |   5 +
 internal/epub/progress/epub_progress.go       |   3 +
 internal/epub/templates/epub_templates.go     |   3 +
 .../epub/templates/epub_templates_content.go  |   4 +
 .../{epub_toc.go => epub_templates_toc.go}    |   1 +
 internal/epub/tree/epub_tree.go               |  22 ++++
 internal/epub/zip/epub_zip.go                 |  11 ++
 internal/sortpath/sortpath.go                 | 108 +++++-------------
 internal/sortpath/sortpath_parser.go          |  83 ++++++++++++++
 main.go                                       |  17 ++-
 26 files changed, 318 insertions(+), 121 deletions(-)
 rename internal/epub/{image_processing => imageprocessing}/epub_image_processing.go (93%)
 rename internal/epub/{image_processing => imageprocessing}/epub_image_processing_helpers.go (90%)
 rename internal/epub/{image_processing => imageprocessing}/epub_image_processing_loader.go (96%)
 rename internal/epub/templates/{epub_toc.go => epub_templates_toc.go} (99%)
 create mode 100644 internal/sortpath/sortpath_parser.go

diff --git a/internal/converter/converter.go b/internal/converter/converter.go
index 4b23170..cfadda1 100644
--- a/internal/converter/converter.go
+++ b/internal/converter/converter.go
@@ -1,3 +1,10 @@
+/*
+Converter Helper to parse and prepare options for go-comic-converter.
+
+It use goflag with additional feature:
+  - Keep original order
+  - Support section
+*/
 package converter
 
 import (
@@ -17,17 +24,18 @@ type Converter struct {
 	Options *options.Options
 	Cmd     *flag.FlagSet
 
-	order           []Order
+	order           []converterOrder
 	isZeroValueErrs []error
 }
 
+// Create a new parser
 func New() *Converter {
 	options := options.New()
 	cmd := flag.NewFlagSet("go-comic-converter", flag.ExitOnError)
 	conv := &Converter{
 		Options: options,
 		Cmd:     cmd,
-		order:   make([]Order, 0),
+		order:   make([]converterOrder, 0),
 	}
 
 	var cmdOutput strings.Builder
@@ -36,9 +44,9 @@ func New() *Converter {
 		fmt.Fprintf(os.Stderr, "Usage of %s:\n", filepath.Base(os.Args[0]))
 		for _, o := range conv.order {
 			switch v := o.(type) {
-			case OrderSection:
+			case converterOrderSection:
 				fmt.Fprintf(os.Stderr, "\n%s:\n", o.Value())
-			case OrderName:
+			case converterOrderName:
 				fmt.Fprintln(os.Stderr, conv.Usage(v.isString, cmd.Lookup(v.Value())))
 			}
 		}
@@ -50,29 +58,35 @@ func New() *Converter {
 	return conv
 }
 
+// Load default options (config + default)
 func (c *Converter) LoadConfig() error {
-	return c.Options.LoadDefault()
+	return c.Options.LoadConfig()
 }
 
+// Create a new section of config
 func (c *Converter) AddSection(section string) {
-	c.order = append(c.order, OrderSection{value: section})
+	c.order = append(c.order, converterOrderSection{value: section})
 }
 
+// Add a string parameter
 func (c *Converter) AddStringParam(p *string, name string, value string, usage string) {
 	c.Cmd.StringVar(p, name, value, usage)
-	c.order = append(c.order, OrderName{value: name, isString: true})
+	c.order = append(c.order, converterOrderName{value: name, isString: true})
 }
 
+// Add an integer parameter
 func (c *Converter) AddIntParam(p *int, name string, value int, usage string) {
 	c.Cmd.IntVar(p, name, value, usage)
-	c.order = append(c.order, OrderName{value: name})
+	c.order = append(c.order, converterOrderName{value: name})
 }
 
+// Add a boolean parameter
 func (c *Converter) AddBoolParam(p *bool, name string, value bool, usage string) {
 	c.Cmd.BoolVar(p, name, value, usage)
-	c.order = append(c.order, OrderName{value: name})
+	c.order = append(c.order, converterOrderName{value: name})
 }
 
+// Initialize the parser with all section and parameter.
 func (c *Converter) InitParse() {
 	c.AddSection("Output")
 	c.AddStringParam(&c.Options.Input, "input", "", "Source of comic to convert: directory, cbz, zip, cbr, rar, pdf")
@@ -110,6 +124,7 @@ func (c *Converter) InitParse() {
 	c.AddBoolParam(&c.Options.Help, "help", false, "Show this help message")
 }
 
+// Customize version of FlagSet.PrintDefaults
 func (c *Converter) Usage(isString bool, f *flag.Flag) string {
 	var b strings.Builder
 	fmt.Fprintf(&b, "  -%s", f.Name) // Two spaces before -; see next two comments.
@@ -144,6 +159,8 @@ func (c *Converter) Usage(isString bool, f *flag.Flag) string {
 	return b.String()
 }
 
+// Taken from flag package as it is private and needed for usage.
+//
 // isZeroValue determines whether the string represents the zero
 // value for a flag.
 func (c *Converter) isZeroValue(f *flag.Flag, value string) (ok bool, err error) {
@@ -171,6 +188,7 @@ func (c *Converter) isZeroValue(f *flag.Flag, value string) (ok bool, err error)
 	return value == z.Interface().(flag.Value).String(), nil
 }
 
+// Parse all parameters
 func (c *Converter) Parse() {
 	c.Cmd.Parse(os.Args[1:])
 	if c.Options.Help {
@@ -184,6 +202,7 @@ func (c *Converter) Parse() {
 	}
 }
 
+// Check parameters
 func (c *Converter) Validate() error {
 	// Check input
 	if c.Options.Input == "" {
@@ -262,6 +281,7 @@ func (c *Converter) Validate() error {
 		return errors.New("contrast should be between -100 and 100")
 	}
 
+	// SortPathMode
 	if c.Options.SortPathMode < 0 || c.Options.SortPathMode > 2 {
 		return errors.New("sort should be 0, 1 or 2")
 	}
@@ -269,6 +289,7 @@ func (c *Converter) Validate() error {
 	return nil
 }
 
+// Helper to show usage, err and exit 1
 func (c *Converter) Fatal(err error) {
 	c.Cmd.Usage()
 	fmt.Fprintf(os.Stderr, "\nError: %s\n", err)
diff --git a/internal/converter/converter_order.go b/internal/converter/converter_order.go
index a454c9b..df431dd 100644
--- a/internal/converter/converter_order.go
+++ b/internal/converter/converter_order.go
@@ -1,22 +1,27 @@
 package converter
 
-type Order interface {
+// Name or Section
+type converterOrder interface {
 	Value() string
 }
 
-type OrderSection struct {
+// Section
+type converterOrderSection struct {
 	value string
 }
 
-func (s OrderSection) Value() string {
+func (s converterOrderSection) Value() string {
 	return s.value
 }
 
-type OrderName struct {
+// Name
+//
+// isString is used to quote the default value.
+type converterOrderName struct {
 	value    string
 	isString bool
 }
 
-func (s OrderName) Value() string {
+func (s converterOrderName) Value() string {
 	return s.value
 }
diff --git a/internal/converter/options/converter_options.go b/internal/converter/options/converter_options.go
index 782b6b6..c16cb90 100644
--- a/internal/converter/options/converter_options.go
+++ b/internal/converter/options/converter_options.go
@@ -1,3 +1,6 @@
+/*
+Manage options with default value from config.
+*/
 package options
 
 import (
@@ -50,6 +53,7 @@ type Options struct {
 	profiles profiles.Profiles
 }
 
+// Initialize default options.
 func New() *Options {
 	return &Options{
 		Profile:                    "",
@@ -89,16 +93,18 @@ func (o *Options) String() string {
 		o.Author,
 		o.Title,
 		o.Workers,
-		o.ShowDefault(),
+		o.ShowConfig(),
 	)
 }
 
+// Config file: ~/.go-comic-converter.yaml
 func (o *Options) FileName() string {
 	home, _ := os.UserHomeDir()
 	return filepath.Join(home, ".go-comic-converter.yaml")
 }
 
-func (o *Options) LoadDefault() error {
+// Load config files
+func (o *Options) LoadConfig() error {
 	f, err := os.Open(o.FileName())
 	if err != nil {
 		return nil
@@ -112,7 +118,8 @@ func (o *Options) LoadDefault() error {
 	return nil
 }
 
-func (o *Options) ShowDefault() string {
+// Get current settings for fields that can be saved
+func (o *Options) ShowConfig() string {
 	var profileDesc, viewDesc string
 	profile := o.GetProfile()
 	if profile != nil {
@@ -180,12 +187,14 @@ func (o *Options) ShowDefault() string {
 	)
 }
 
-func (o *Options) ResetDefault() error {
-	New().SaveDefault()
-	return o.LoadDefault()
+// reset all settings to default value
+func (o *Options) ResetConfig() error {
+	New().SaveConfig()
+	return o.LoadConfig()
 }
 
-func (o *Options) SaveDefault() error {
+// save all current settings as futur default value
+func (o *Options) SaveConfig() error {
 	f, err := os.Create(o.FileName())
 	if err != nil {
 		return err
@@ -194,10 +203,12 @@ func (o *Options) SaveDefault() error {
 	return yaml.NewEncoder(f).Encode(o)
 }
 
+// shortcut to get current profile
 func (o *Options) GetProfile() *profiles.Profile {
 	return o.profiles.Get(o.Profile)
 }
 
+// all available profiles
 func (o *Options) AvailableProfiles() string {
 	return o.profiles.String()
 }
diff --git a/internal/converter/profiles/converter_profiles.go b/internal/converter/profiles/converter_profiles.go
index 49c68a0..a1672ea 100644
--- a/internal/converter/profiles/converter_profiles.go
+++ b/internal/converter/profiles/converter_profiles.go
@@ -1,3 +1,6 @@
+/*
+Manage supported profiles for go-comic-converter.
+*/
 package profiles
 
 import (
@@ -12,8 +15,10 @@ type Profile struct {
 	Height      int
 }
 
+// Recommended ratio of image for perfect rendering Portrait or Landscape.
 const PerfectRatio = 1.5
 
+// Compute best dimension based on device size
 func (p Profile) PerfectDim() (int, int) {
 	width, height := float64(p.Width), float64(p.Height)
 	perfectWidth, perfectHeight := height/PerfectRatio, width*PerfectRatio
@@ -27,6 +32,7 @@ func (p Profile) PerfectDim() (int, int) {
 
 type Profiles []Profile
 
+// Initialize list of all supported profiles.
 func New() Profiles {
 	return []Profile{
 		{"K1", "Kindle 1", 600, 670},
@@ -70,6 +76,7 @@ func (p Profiles) String() string {
 	return strings.Join(s, "\n")
 }
 
+// Lookup profile by code
 func (p Profiles) Get(name string) *Profile {
 	for _, profile := range p {
 		if profile.Code == name {
diff --git a/internal/epub/epub.go b/internal/epub/epub.go
index 0a5641d..319c41d 100644
--- a/internal/epub/epub.go
+++ b/internal/epub/epub.go
@@ -1,3 +1,6 @@
+/*
+Tools to create epub from images.
+*/
 package epub
 
 import (
@@ -11,7 +14,7 @@ import (
 	"time"
 
 	epubimage "github.com/celogeek/go-comic-converter/v2/internal/epub/image"
-	epubimageprocessing "github.com/celogeek/go-comic-converter/v2/internal/epub/image_processing"
+	epubimageprocessing "github.com/celogeek/go-comic-converter/v2/internal/epub/imageprocessing"
 	epubprogress "github.com/celogeek/go-comic-converter/v2/internal/epub/progress"
 	epubtemplates "github.com/celogeek/go-comic-converter/v2/internal/epub/templates"
 	epubtree "github.com/celogeek/go-comic-converter/v2/internal/epub/tree"
@@ -48,6 +51,7 @@ type epubPart struct {
 	Images []*epubimage.Image
 }
 
+// initialize epub
 func New(options *Options) *ePub {
 	uid := uuid.Must(uuid.NewV4())
 	tmpl := template.New("parser")
@@ -65,7 +69,8 @@ func New(options *Options) *ePub {
 	}
 }
 
-func (e *ePub) render(templateString string, data any) string {
+// render templates
+func (e *ePub) render(templateString string, data map[string]any) string {
 	var result strings.Builder
 	tmpl := template.Must(e.templateProcessor.Parse(templateString))
 	if err := tmpl.Execute(&result, data); err != nil {
@@ -74,6 +79,7 @@ func (e *ePub) render(templateString string, data any) string {
 	return regexp.MustCompile("\n+").ReplaceAllString(result.String(), "\n")
 }
 
+// write image to the zip
 func (e *ePub) writeImage(wz *epubzip.EpubZip, img *epubimage.Image) error {
 	err := wz.WriteFile(
 		fmt.Sprintf("OEBPS/%s", img.TextPath()),
@@ -92,6 +98,7 @@ func (e *ePub) writeImage(wz *epubzip.EpubZip, img *epubimage.Image) error {
 	return err
 }
 
+// write blank page
 func (e *ePub) writeBlank(wz *epubzip.EpubZip, img *epubimage.Image) error {
 	return wz.WriteFile(
 		fmt.Sprintf("OEBPS/Text/%d_sp.xhtml", img.Id),
@@ -102,6 +109,7 @@ func (e *ePub) writeBlank(wz *epubzip.EpubZip, img *epubimage.Image) error {
 	)
 }
 
+// extract image and split it into part
 func (e *ePub) getParts() ([]*epubPart, error) {
 	images, err := epubimageprocessing.LoadImages(&epubimageprocessing.Options{
 		Input:        e.Input,
@@ -116,14 +124,12 @@ func (e *ePub) getParts() ([]*epubPart, error) {
 		return nil, err
 	}
 
+	// sort result by id and part
 	sort.Slice(images, func(i, j int) bool {
-		if images[i].Id < images[j].Id {
-			return true
-		} else if images[i].Id == images[j].Id {
+		if images[i].Id == images[j].Id {
 			return images[i].Part < images[j].Part
-		} else {
-			return false
 		}
+		return images[i].Id < images[j].Id
 	})
 
 	parts := make([]*epubPart, 0)
@@ -140,8 +146,8 @@ func (e *ePub) getParts() ([]*epubPart, error) {
 		return parts, nil
 	}
 
+	// compute size of the epub part and try to be as close as possible of the target
 	maxSize := uint64(e.LimitMb * 1024 * 1024)
-
 	xhtmlSize := uint64(1024)
 	// descriptor files + title
 	baseSize := uint64(16*1024) + cover.Data.CompressedSize()
@@ -180,6 +186,9 @@ func (e *ePub) getParts() ([]*epubPart, error) {
 	return parts, nil
 }
 
+// create a tree from the directories.
+//
+// this is used to simulate the toc.
 func (e *ePub) getTree(images []*epubimage.Image, skip_files bool) string {
 	t := epubtree.New()
 	for _, img := range images {
@@ -197,6 +206,7 @@ func (e *ePub) getTree(images []*epubimage.Image, skip_files bool) string {
 	return c.WriteString("")
 }
 
+// create the zip
 func (e *ePub) Write() error {
 	type zipContent struct {
 		Name    string
@@ -285,7 +295,7 @@ func (e *ePub) Write() error {
 				return err
 			}
 		}
-		if err := wz.WriteImage(epubimageprocessing.LoadCoverData(part.Cover, title, e.Image.Quality)); err != nil {
+		if err := wz.WriteImage(epubimageprocessing.LoadCoverTitleData(part.Cover, title, e.Image.Quality)); err != nil {
 			return err
 		}
 
diff --git a/internal/epub/filters/epub_filters_autorotate.go b/internal/epub/filters/epub_filters_autorotate.go
index b0561bc..1460c01 100644
--- a/internal/epub/filters/epub_filters_autorotate.go
+++ b/internal/epub/filters/epub_filters_autorotate.go
@@ -1,3 +1,6 @@
+/*
+Rotate image if the source width > height.
+*/
 package epubfilters
 
 import (
diff --git a/internal/epub/filters/epub_filters_cover_title.go b/internal/epub/filters/epub_filters_cover_title.go
index 51ce8b9..546f790 100644
--- a/internal/epub/filters/epub_filters_cover_title.go
+++ b/internal/epub/filters/epub_filters_cover_title.go
@@ -1,3 +1,6 @@
+/*
+Create a title with the cover image
+*/
 package epubfilters
 
 import (
@@ -19,10 +22,12 @@ type coverTitle struct {
 	title string
 }
 
+// size is the same as source
 func (p *coverTitle) Bounds(srcBounds image.Rectangle) (dstBounds image.Rectangle) {
 	return srcBounds
 }
 
+// blur the src image, and create a box with the title in the middle
 func (p *coverTitle) Draw(dst draw.Image, src image.Image, options *gift.Options) {
 	// Create a blur version of the cover
 	g := gift.New(gift.GaussianBlur(4))
diff --git a/internal/epub/filters/epub_filters_crop.go b/internal/epub/filters/epub_filters_crop.go
index 87905f0..a3044a5 100644
--- a/internal/epub/filters/epub_filters_crop.go
+++ b/internal/epub/filters/epub_filters_crop.go
@@ -1,3 +1,8 @@
+/*
+cut a double page in 2 part: left and right.
+
+this will cut in the middle of the page.
+*/
 package epubfilters
 
 import (
diff --git a/internal/epub/filters/epub_filters_pixel.go b/internal/epub/filters/epub_filters_pixel.go
index 61b0a9a..ecb4b6f 100644
--- a/internal/epub/filters/epub_filters_pixel.go
+++ b/internal/epub/filters/epub_filters_pixel.go
@@ -1,3 +1,8 @@
+/*
+generate a blank pixel 1x1, if the size of the image is 0x0.
+
+An image 0x0 is not a valid image, and failed to read.
+*/
 package epubfilters
 
 import (
@@ -27,6 +32,7 @@ func (p *pixel) Bounds(srcBounds image.Rectangle) (dstBounds image.Rectangle) {
 func (p *pixel) Draw(dst draw.Image, src image.Image, options *gift.Options) {
 	if dst.Bounds().Dx() == 1 && dst.Bounds().Dy() == 1 {
 		dst.Set(0, 0, color.White)
+		return
 	}
 	draw.Draw(dst, dst.Bounds(), src, src.Bounds().Min, draw.Src)
 }
diff --git a/internal/epub/filters/epub_filters_resize.go b/internal/epub/filters/epub_filters_resize.go
index ddde7d4..a91f179 100644
--- a/internal/epub/filters/epub_filters_resize.go
+++ b/internal/epub/filters/epub_filters_resize.go
@@ -1,3 +1,8 @@
+/*
+Resize image by keeping aspect ratio.
+
+This will reduce or enlarge image to fit into the viewWidth and viewHeight.
+*/
 package epubfilters
 
 import (
@@ -42,6 +47,5 @@ func (p *resizeFilter) Bounds(srcBounds image.Rectangle) image.Rectangle {
 }
 
 func (p *resizeFilter) Draw(dst draw.Image, src image.Image, options *gift.Options) {
-	b := p.Bounds(src.Bounds())
-	gift.Resize(b.Dx(), b.Dy(), p.resampling).Draw(dst, src, options)
+	gift.Resize(dst.Bounds().Dx(), dst.Bounds().Dy(), p.resampling).Draw(dst, src, options)
 }
diff --git a/internal/epub/image/epub_image.go b/internal/epub/image/epub_image.go
index e47b019..21eb47c 100644
--- a/internal/epub/image/epub_image.go
+++ b/internal/epub/image/epub_image.go
@@ -1,3 +1,6 @@
+/*
+Image helpers to transform image.
+*/
 package epubimage
 
 import (
@@ -20,22 +23,35 @@ type Image struct {
 	Name       string
 }
 
+// key name of the image
 func (i *Image) Key(prefix string) string {
 	return fmt.Sprintf("%s_%d_p%d", prefix, i.Id, i.Part)
 }
 
+// key name of the blank plage after the image
 func (i *Image) SpaceKey(prefix string) string {
 	return fmt.Sprintf("%s_%d_sp", prefix, i.Id)
 }
 
+// path of the blank page
+func (i *Image) SpacePath() string {
+	return fmt.Sprintf("Text/%d_sp.xhtml", i.Id)
+}
+
+// text path linked to the image
 func (i *Image) TextPath() string {
 	return fmt.Sprintf("Text/%d_p%d.xhtml", i.Id, i.Part)
 }
 
+// image path
 func (i *Image) ImgPath() string {
 	return fmt.Sprintf("Images/%d_p%d.jpg", i.Id, i.Part)
 }
 
+// style to apply to the image.
+//
+// center by default.
+// align to left or right if it's part of the splitted double page.
 func (i *Image) ImgStyle(viewWidth, viewHeight int, manga bool) string {
 	marginW, marginH := float64(viewWidth-i.Width)/2, float64(viewHeight-i.Height)/2
 	left, top := marginW*100/float64(viewWidth), marginH*100/float64(viewHeight)
@@ -65,7 +81,3 @@ func (i *Image) ImgStyle(viewWidth, viewHeight int, manga bool) string {
 		align,
 	)
 }
-
-func (i *Image) SpacePath() string {
-	return fmt.Sprintf("Text/%d_sp.xhtml", i.Id)
-}
diff --git a/internal/epub/image/epub_image_filters.go b/internal/epub/image/epub_image_filters.go
index 718e3fd..f44f2e3 100644
--- a/internal/epub/image/epub_image_filters.go
+++ b/internal/epub/image/epub_image_filters.go
@@ -5,6 +5,7 @@ import (
 	"github.com/disintegration/gift"
 )
 
+// create filter to apply to the source
 func NewGift(options *Options) *gift.GIFT {
 	g := gift.New()
 	g.SetParallelization(false)
@@ -25,6 +26,7 @@ func NewGift(options *Options) *gift.GIFT {
 	return g
 }
 
+// create filters to cut image into 2 equal pieces
 func NewGiftSplitDoublePage(options *Options) []*gift.GIFT {
 	gifts := make([]*gift.GIFT, 2)
 
diff --git a/internal/epub/image/epub_image_options.go b/internal/epub/image/epub_image_options.go
index 26ed66d..3797036 100644
--- a/internal/epub/image/epub_image_options.go
+++ b/internal/epub/image/epub_image_options.go
@@ -1,5 +1,6 @@
 package epubimage
 
+// options for image transformation
 type Options struct {
 	Crop                bool
 	ViewWidth           int
diff --git a/internal/epub/imagedata/epub_image_data.go b/internal/epub/imagedata/epub_image_data.go
index 517ee52..60ce499 100644
--- a/internal/epub/imagedata/epub_image_data.go
+++ b/internal/epub/imagedata/epub_image_data.go
@@ -1,3 +1,6 @@
+/*
+prepare image to be store in a zip file.
+*/
 package epubimagedata
 
 import (
@@ -17,6 +20,7 @@ type ImageData struct {
 	Data   []byte
 }
 
+// compressed size of the image with the header
 func (img *ImageData) CompressedSize() uint64 {
 	return img.Header.CompressedSize64 + 30 + uint64(len(img.Header.Name))
 }
@@ -26,11 +30,13 @@ func exitWithError(err error) {
 	os.Exit(1)
 }
 
+// create a new data image with file name based on id and part
 func New(id int, part int, img image.Image, quality int) *ImageData {
 	name := fmt.Sprintf("OEBPS/Images/%d_p%d.jpg", id, part)
 	return NewRaw(name, img, quality)
 }
 
+// create gzip encoded jpeg
 func NewRaw(name string, img image.Image, quality int) *ImageData {
 	var (
 		data, cdata bytes.Buffer
diff --git a/internal/epub/image_processing/epub_image_processing.go b/internal/epub/imageprocessing/epub_image_processing.go
similarity index 93%
rename from internal/epub/image_processing/epub_image_processing.go
rename to internal/epub/imageprocessing/epub_image_processing.go
index 2aa1d70..fdafe59 100644
--- a/internal/epub/image_processing/epub_image_processing.go
+++ b/internal/epub/imageprocessing/epub_image_processing.go
@@ -1,3 +1,6 @@
+/*
+Extract and transform image into a compressed jpeg.
+*/
 package epubimageprocessing
 
 import (
@@ -26,6 +29,7 @@ type tasks struct {
 	Name   string
 }
 
+// extract and convert images
 func LoadImages(o *Options) ([]*epubimage.Image, error) {
 	images := make([]*epubimage.Image, 0)
 
@@ -39,6 +43,7 @@ func LoadImages(o *Options) ([]*epubimage.Image, error) {
 		imageInput chan *tasks
 	)
 
+	// get all images though a channel of bytes
 	if fi.IsDir() {
 		imageCount, imageInput, err = o.loadDir()
 	} else {
@@ -57,6 +62,7 @@ func LoadImages(o *Options) ([]*epubimage.Image, error) {
 		return nil, err
 	}
 
+	// dry run, skip convertion
 	if o.Dry {
 		for img := range imageInput {
 			images = append(images, &epubimage.Image{
@@ -178,7 +184,8 @@ func LoadImages(o *Options) ([]*epubimage.Image, error) {
 	return images, nil
 }
 
-func LoadCoverData(img *epubimage.Image, title string, quality int) *epubimagedata.ImageData {
+// create a title page with the cover
+func LoadCoverTitleData(img *epubimage.Image, title string, quality int) *epubimagedata.ImageData {
 	// Create a blur version of the cover
 	g := gift.New(epubfilters.CoverTitle(title))
 	dst := image.NewGray(g.Bounds(img.Raw.Bounds()))
diff --git a/internal/epub/image_processing/epub_image_processing_helpers.go b/internal/epub/imageprocessing/epub_image_processing_helpers.go
similarity index 90%
rename from internal/epub/image_processing/epub_image_processing_helpers.go
rename to internal/epub/imageprocessing/epub_image_processing_helpers.go
index 6c5a5d5..067da84 100644
--- a/internal/epub/image_processing/epub_image_processing_helpers.go
+++ b/internal/epub/imageprocessing/epub_image_processing_helpers.go
@@ -7,6 +7,7 @@ import (
 	"strings"
 )
 
+// only accept jpg, png and webp as source file
 func isSupportedImage(path string) bool {
 	switch strings.ToLower(filepath.Ext(path)) {
 	case ".jpg", ".jpeg", ".png", ".webp":
@@ -17,11 +18,13 @@ func isSupportedImage(path string) bool {
 	return false
 }
 
+// check if the color is blank enough
 func colorIsBlank(c color.Color) bool {
 	g := color.GrayModel.Convert(c).(color.Gray)
 	return g.Y >= 0xf0
 }
 
+// lookup for margin (blank) around the image
 func findMarging(img image.Image) image.Rectangle {
 	imgArea := img.Bounds()
 
diff --git a/internal/epub/image_processing/epub_image_processing_loader.go b/internal/epub/imageprocessing/epub_image_processing_loader.go
similarity index 96%
rename from internal/epub/image_processing/epub_image_processing_loader.go
rename to internal/epub/imageprocessing/epub_image_processing_loader.go
index b19c2d5..6c9def8 100644
--- a/internal/epub/image_processing/epub_image_processing_loader.go
+++ b/internal/epub/imageprocessing/epub_image_processing_loader.go
@@ -30,6 +30,7 @@ type Options struct {
 
 var errNoImagesFound = errors.New("no images found")
 
+// ensure copy image into a buffer
 func (o *Options) mustExtractImage(imageOpener func() (io.ReadCloser, error)) *bytes.Buffer {
 	var b bytes.Buffer
 	if o.Dry {
@@ -51,6 +52,7 @@ func (o *Options) mustExtractImage(imageOpener func() (io.ReadCloser, error)) *b
 	return &b
 }
 
+// load a directory of images
 func (o *Options) loadDir() (totalImages int, output chan *tasks, err error) {
 	images := make([]string, 0)
 
@@ -101,6 +103,7 @@ func (o *Options) loadDir() (totalImages int, output chan *tasks, err error) {
 	return
 }
 
+// load a zip file that include images
 func (o *Options) loadCbz() (totalImages int, output chan *tasks, err error) {
 	r, err := zip.OpenReader(o.Input)
 	if err != nil {
@@ -150,6 +153,7 @@ func (o *Options) loadCbz() (totalImages int, output chan *tasks, err error) {
 	return
 }
 
+// load a rar file that include images
 func (o *Options) loadCbr() (totalImages int, output chan *tasks, err error) {
 	// listing and indexing
 	rl, err := rardecode.OpenReader(o.Input, "")
@@ -233,6 +237,7 @@ func (o *Options) loadCbr() (totalImages int, output chan *tasks, err error) {
 	return
 }
 
+// extract image from a pdf
 func (o *Options) loadPdf() (totalImages int, output chan *tasks, err error) {
 	pdf := pdfread.Load(o.Input)
 	if pdf == nil {
diff --git a/internal/epub/progress/epub_progress.go b/internal/epub/progress/epub_progress.go
index a29d8a3..21dd011 100644
--- a/internal/epub/progress/epub_progress.go
+++ b/internal/epub/progress/epub_progress.go
@@ -1,3 +1,6 @@
+/*
+create a progress bar with custom settings.
+*/
 package epubprogress
 
 import (
diff --git a/internal/epub/templates/epub_templates.go b/internal/epub/templates/epub_templates.go
index 6976e6c..8256639 100644
--- a/internal/epub/templates/epub_templates.go
+++ b/internal/epub/templates/epub_templates.go
@@ -1,3 +1,6 @@
+/*
+Templates use to create xml files of the epub.
+*/
 package epubtemplates
 
 import _ "embed"
diff --git a/internal/epub/templates/epub_templates_content.go b/internal/epub/templates/epub_templates_content.go
index d1b513c..6c4589f 100644
--- a/internal/epub/templates/epub_templates_content.go
+++ b/internal/epub/templates/epub_templates_content.go
@@ -28,6 +28,7 @@ type tag struct {
 	value string
 }
 
+// create the content file
 func Content(o *ContentOptions) string {
 	doc := etree.NewDocument()
 	doc.CreateProcInst("xml", `version="1.0" encoding="UTF-8"`)
@@ -76,6 +77,7 @@ func Content(o *ContentOptions) string {
 	return r
 }
 
+// metadata part of the content
 func getMeta(o *ContentOptions) []tag {
 	metas := []tag{
 		{"meta", tagAttrs{"property": "dcterms:modified"}, o.UpdatedAt},
@@ -152,6 +154,7 @@ func getManifest(o *ContentOptions) []tag {
 	return items
 }
 
+// spine part of the content
 func getSpine(o *ContentOptions) []tag {
 	isOnTheRight := !o.ImageOptions.Manga
 	getSpread := func(doublePageNoBlank bool) string {
@@ -196,6 +199,7 @@ func getSpine(o *ContentOptions) []tag {
 	return spine
 }
 
+// guide part of the content
 func getGuide(o *ContentOptions) []tag {
 	guide := []tag{}
 	if o.Cover != nil {
diff --git a/internal/epub/templates/epub_toc.go b/internal/epub/templates/epub_templates_toc.go
similarity index 99%
rename from internal/epub/templates/epub_toc.go
rename to internal/epub/templates/epub_templates_toc.go
index 7fc2842..be3d612 100644
--- a/internal/epub/templates/epub_toc.go
+++ b/internal/epub/templates/epub_templates_toc.go
@@ -8,6 +8,7 @@ import (
 	epubimage "github.com/celogeek/go-comic-converter/v2/internal/epub/image"
 )
 
+// create toc
 func Toc(title string, stripFirstDirectoryFromToc bool, images []*epubimage.Image) string {
 	doc := etree.NewDocument()
 	doc.CreateProcInst("xml", `version="1.0" encoding="UTF-8"`)
diff --git a/internal/epub/tree/epub_tree.go b/internal/epub/tree/epub_tree.go
index 84253cf..c4d5217 100644
--- a/internal/epub/tree/epub_tree.go
+++ b/internal/epub/tree/epub_tree.go
@@ -1,3 +1,21 @@
+/*
+Organize a list of filename with their path into a tree of directories.
+
+Example:
+  - A/B/C/D.jpg
+  - A/B/C/E.jpg
+  - A/B/F/G.jpg
+
+This is transformed like:
+
+	A
+	 B
+	  C
+	   D.jpg
+	   E.jpg
+	 F
+	  G.jpg
+*/
 package epubtree
 
 import (
@@ -14,16 +32,19 @@ type node struct {
 	Children []*node
 }
 
+// initilize tree with a root node
 func New() *tree {
 	return &tree{map[string]*node{
 		".": {".", []*node{}},
 	}}
 }
 
+// root node
 func (n *tree) Root() *node {
 	return n.Nodes["."]
 }
 
+// add the filename to the tree
 func (n *tree) Add(filename string) {
 	cn := n.Root()
 	cp := ""
@@ -37,6 +58,7 @@ func (n *tree) Add(filename string) {
 	}
 }
 
+// string version of the tree
 func (n *node) WriteString(indent string) string {
 	r := strings.Builder{}
 	if indent != "" {
diff --git a/internal/epub/zip/epub_zip.go b/internal/epub/zip/epub_zip.go
index 6f4ee54..8698d10 100644
--- a/internal/epub/zip/epub_zip.go
+++ b/internal/epub/zip/epub_zip.go
@@ -1,3 +1,8 @@
+/*
+Helper to write epub files.
+
+We create a zip with the magic epub mimetype.
+*/
 package epubzip
 
 import (
@@ -13,6 +18,7 @@ type EpubZip struct {
 	wz *zip.Writer
 }
 
+// create a new epub
 func New(path string) (*EpubZip, error) {
 	w, err := os.Create(path)
 	if err != nil {
@@ -22,6 +28,7 @@ func New(path string) (*EpubZip, error) {
 	return &EpubZip{w, wz}, nil
 }
 
+// close compress pipe and file.
 func (e *EpubZip) Close() error {
 	if err := e.wz.Close(); err != nil {
 		return err
@@ -29,6 +36,8 @@ func (e *EpubZip) Close() error {
 	return e.w.Close()
 }
 
+// Write mimetype, in a very specific way.
+// This will be valid with epubcheck tools.
 func (e *EpubZip) WriteMagic() error {
 	t := time.Now()
 	fh := &zip.FileHeader{
@@ -51,6 +60,7 @@ func (e *EpubZip) WriteMagic() error {
 	return err
 }
 
+// Write image. They are already compressed, so we write them down directly.
 func (e *EpubZip) WriteImage(image *epubimagedata.ImageData) error {
 	m, err := e.wz.CreateRaw(image.Header)
 	if err != nil {
@@ -60,6 +70,7 @@ func (e *EpubZip) WriteImage(image *epubimagedata.ImageData) error {
 	return err
 }
 
+// Write file. Compressed it using deflate.
 func (e *EpubZip) WriteFile(file string, content []byte) error {
 	m, err := e.wz.CreateHeader(&zip.FileHeader{
 		Name:     file,
diff --git a/internal/sortpath/sortpath.go b/internal/sortpath/sortpath.go
index bcefb6d..9b29c31 100644
--- a/internal/sortpath/sortpath.go
+++ b/internal/sortpath/sortpath.go
@@ -1,95 +1,45 @@
+/*
+sortpath support sorting of path that may include number.
+
+A series of path can looks like:
+  - Tome1/Chap1/Image1.jpg
+  - Tome1/Chap2/Image1.jpg
+  - Tome1/Chap10/Image2.jpg
+
+The module will split the string by path,
+and compare them by decomposing the string and number part.
+
+The module support 3 mode:
+  - mode=0 alpha for path and file
+  - mode=1 alphanum for path and alpha for file
+  - mode=2 alphanum for path and file
+
+Example:
+
+	files := []string{
+		'T1/C1/Img1.jpg',
+		'T1/C2/Img1.jpg',
+		'T1/C10/Img1.jpg',
+	}
+
+	sort.Sort(sortpath.By(files, 1))
+*/
 package sortpath
 
-import (
-	"path/filepath"
-	"regexp"
-	"strconv"
-	"strings"
-)
-
-// Strings follow with numbers like: s1, s1.2, s2-3, ...
-var split_path_regex = regexp.MustCompile(`^(.*?)(\d+(?:\.\d+)?)(?:-(\d+(?:\.\d+)?))?$`)
-
-type part struct {
-	fullname string
-	name     string
-	number   float64
-}
-
-func (a part) compare(b part) float64 {
-	if a.number == 0 || b.number == 0 {
-		return float64(strings.Compare(a.fullname, b.fullname))
-	}
-	if a.name == b.name {
-		return a.number - b.number
-	} else {
-		return float64(strings.Compare(a.name, b.name))
-	}
-}
-
-func parsePart(p string) part {
-	r := split_path_regex.FindStringSubmatch(p)
-	if len(r) == 0 {
-		return part{p, p, 0}
-	}
-	n, err := strconv.ParseFloat(r[2], 64)
-	if err != nil {
-		return part{p, p, 0}
-	}
-	return part{p, r[1], n}
-}
-
-// mode=0 alpha for path and file
-// mode=1 alphanum for path and alpha for file
-// mode=2 alphanum for path and file
-func parse(filename string, mode int) []part {
-	pathname, name := filepath.Split(strings.ToLower(filename))
-	pathname = strings.TrimSuffix(pathname, string(filepath.Separator))
-	ext := filepath.Ext(name)
-	name = name[0 : len(name)-len(ext)]
-
-	f := []part{}
-	for _, p := range strings.Split(pathname, string(filepath.Separator)) {
-		if mode > 0 { // alphanum for path
-			f = append(f, parsePart(p))
-		} else {
-			f = append(f, part{p, p, 0})
-		}
-	}
-	if mode == 2 { // alphanum for file
-		f = append(f, parsePart(name))
-	} else {
-		f = append(f, part{name, name, 0})
-	}
-	return f
-}
-
-func comparePart(a, b []part) float64 {
-	m := len(a)
-	if m > len(b) {
-		m = len(b)
-	}
-	for i := 0; i < m; i++ {
-		c := a[i].compare(b[i])
-		if c != 0 {
-			return c
-		}
-	}
-	return float64(len(a) - len(b))
-}
-
+// struct that implement interface for sort.Sort
 type by struct {
 	filenames []string
 	paths     [][]part
 }
 
 func (b by) Len() int           { return len(b.filenames) }
-func (b by) Less(i, j int) bool { return comparePart(b.paths[i], b.paths[j]) < 0 }
+func (b by) Less(i, j int) bool { return compareParts(b.paths[i], b.paths[j]) < 0 }
 func (b by) Swap(i, j int) {
 	b.filenames[i], b.filenames[j] = b.filenames[j], b.filenames[i]
 	b.paths[i], b.paths[j] = b.paths[j], b.paths[i]
 }
 
+// use sortpath.By with sort.Sort
 func By(filenames []string, mode int) by {
 	p := [][]part{}
 	for _, filename := range filenames {
diff --git a/internal/sortpath/sortpath_parser.go b/internal/sortpath/sortpath_parser.go
new file mode 100644
index 0000000..a8524ba
--- /dev/null
+++ b/internal/sortpath/sortpath_parser.go
@@ -0,0 +1,83 @@
+package sortpath
+
+import (
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// Strings follow with numbers like: s1, s1.2, s2-3, ...
+var split_path_regex = regexp.MustCompile(`^(.*?)(\d+(?:\.\d+)?)(?:-(\d+(?:\.\d+)?))?$`)
+
+type part struct {
+	fullname string
+	name     string
+	number   float64
+}
+
+// compare part, first check if both include a number,
+// if so, compare string part then number part, else compare there as string.
+func (a part) compare(b part) float64 {
+	if a.number == 0 || b.number == 0 {
+		return float64(strings.Compare(a.fullname, b.fullname))
+	}
+	if a.name == b.name {
+		return a.number - b.number
+	} else {
+		return float64(strings.Compare(a.name, b.name))
+	}
+}
+
+// separate from the string the number part.
+func parsePart(p string) part {
+	r := split_path_regex.FindStringSubmatch(p)
+	if len(r) == 0 {
+		return part{p, p, 0}
+	}
+	n, err := strconv.ParseFloat(r[2], 64)
+	if err != nil {
+		return part{p, p, 0}
+	}
+	return part{p, r[1], n}
+}
+
+// mode=0 alpha for path and file
+// mode=1 alphanum for path and alpha for file
+// mode=2 alphanum for path and file
+func parse(filename string, mode int) []part {
+	pathname, name := filepath.Split(strings.ToLower(filename))
+	pathname = strings.TrimSuffix(pathname, string(filepath.Separator))
+	ext := filepath.Ext(name)
+	name = name[0 : len(name)-len(ext)]
+
+	f := []part{}
+	for _, p := range strings.Split(pathname, string(filepath.Separator)) {
+		if mode > 0 { // alphanum for path
+			f = append(f, parsePart(p))
+		} else {
+			f = append(f, part{p, p, 0})
+		}
+	}
+	if mode == 2 { // alphanum for file
+		f = append(f, parsePart(name))
+	} else {
+		f = append(f, part{name, name, 0})
+	}
+	return f
+}
+
+// compare 2 fullpath splitted into parts
+func compareParts(a, b []part) float64 {
+	m := len(a)
+	if m > len(b) {
+		m = len(b)
+	}
+	for i := 0; i < m; i++ {
+		c := a[i].compare(b[i])
+		if c != 0 {
+			return c
+		}
+	}
+	return float64(len(a) - len(b))
+}
diff --git a/main.go b/main.go
index f2e87ba..a0f937b 100644
--- a/main.go
+++ b/main.go
@@ -1,3 +1,10 @@
+/*
+Convert CBZ/CBR/Dir into Epub for e-reader devices (Kindle Devices, ...)
+
+My goal is to make a simple, crossplatform, and fast tool to convert comics into epub.
+
+Epub is now support by Amazon through [SendToKindle](https://www.amazon.com/gp/sendtokindle/), by Email or by using the App. So I've made it simple to support the size limit constraint of those services.
+*/
 package main
 
 import (
@@ -57,29 +64,29 @@ $ go install github.com/celogeek/go-comic-converter/v%d@%s
 	}
 
 	if cmd.Options.Save {
-		cmd.Options.SaveDefault()
+		cmd.Options.SaveConfig()
 		fmt.Fprintf(
 			os.Stderr,
 			"%s%s\n\nSaving to %s\n",
 			cmd.Options.Header(),
-			cmd.Options.ShowDefault(),
+			cmd.Options.ShowConfig(),
 			cmd.Options.FileName(),
 		)
 		return
 	}
 
 	if cmd.Options.Show {
-		fmt.Fprintln(os.Stderr, cmd.Options.Header(), cmd.Options.ShowDefault())
+		fmt.Fprintln(os.Stderr, cmd.Options.Header(), cmd.Options.ShowConfig())
 		return
 	}
 
 	if cmd.Options.Reset {
-		cmd.Options.ResetDefault()
+		cmd.Options.ResetConfig()
 		fmt.Fprintf(
 			os.Stderr,
 			"%s%s\n\nReset default to %s\n",
 			cmd.Options.Header(),
-			cmd.Options.ShowDefault(),
+			cmd.Options.ShowConfig(),
 			cmd.Options.FileName(),
 		)
 		return