Add support for Markdown

.gitignore

@@ -1,2 +1,3 @@
 out.asciidoc
+out.md
 .idea

README.md

@@ -18,17 +18,34 @@ Pre-built Linux binaries can be downloaded from the Github Releases tab. Alterna
 go get -u github.com/elastic/crd-ref-docs
 ```
 
-The tool can be invoked as follows to generate documentation in Asciidoc format:
+The tool can be invoked as follows to generate documentation:
+
+```
+crd-ref-docs \
+    --source-path=$GOPATH/src/github.com/elastic/cloud-on-k8s/pkg/apis \
+    --config=config.yaml
+```
+
+By default, documentation is rendered in Asciidoc format.
+In order to generate documentation in Markdown format, you will have to specify the `markdown` renderer:
 
 ```
 crd-ref-docs \
     --source-path=$GOPATH/src/github.com/elastic/cloud-on-k8s/pkg/apis \
     --config=config.yaml \
-    --renderer=asciidoctor \
-    --templates-dir=templates/asciidoctor \
-    --output-path=out.asciidoc
+    --renderer=markdown
 ```
 
+Default templates are embedded in the binary.
+You may provide your own templates by specifying the templates directory:
+
+```
+crd-ref-docs \
+    --source-path=$GOPATH/src/github.com/elastic/cloud-on-k8s/pkg/apis \
+    --config=config.yaml \
+    --renderer=asciidoctor \
+    --templates-dir=templates/asciidoctor
+```
 
 ### Configuration
 
@@ -50,5 +67,5 @@ processor:
 
 render:
   # Version of Kubernetes to use when generating links to Kubernetes API documentation.
-  kubernetesVersion: 1.15
+  kubernetesVersion: 1.22
 ```

config.yaml

@@ -10,4 +10,4 @@ processor:
     - "TypeMeta$"
 
 render:
-  kubernetesVersion: 1.15
+  kubernetesVersion: 1.22

main.go

@@ -43,8 +43,8 @@ func main() {
 	cmd.Flags().StringVar(&args.Config, "config", "config.yaml", "Path to config file")
 	cmd.Flags().StringVar(&args.SourcePath, "source-path", "", "Path to source directory containing CRDs")
 	cmd.Flags().StringVar(&args.TemplatesDir, "templates-dir", "", "Path to the directory containing template files")
-	cmd.Flags().StringVar(&args.Renderer, "renderer", "asciidoctor", "Renderer to use")
-	cmd.Flags().StringVar(&args.OutputPath, "output-path", "out.asciidoc", "Path to output the rendered result")
+	cmd.Flags().StringVar(&args.Renderer, "renderer", "asciidoctor", "Renderer to use ('asciidoctor' or 'markdown')")
+	cmd.Flags().StringVar(&args.OutputPath, "output-path", ".", "Path to output the rendered result")
 	cmd.Flags().IntVar(&args.MaxDepth, "max-depth", 6, "Maximum recursion level for type discovery")
 
 	cmd.Execute()

renderer/asciidoctor.go

@@ -20,7 +20,6 @@ import (
 	"fmt"
 	"io/fs"
 	"os"
-	"path/filepath"
 	"strings"
 	"text/template"
 
@@ -66,20 +65,7 @@ func (adr *AsciidoctorRenderer) Render(gvd []types.GroupVersionDetails) error {
 		return err
 	}
 
-	outputFile := adr.conf.OutputPath
-	finfo, err := os.Stat(outputFile)
-	if err != nil && !os.IsNotExist(err) {
-		return err
-	}
-
-	if finfo != nil && finfo.IsDir() {
-		outputFile = filepath.Join(outputFile, "out.asciidoc")
-	}
-
-	f, err := os.Create(outputFile)
-	if err != nil {
-		return err
-	}
+	f, err := createOutFile(adr.conf.OutputPath, "out.asciidoc")
 	defer f.Close()
 
 	return tmpl.ExecuteTemplate(f, mainTemplate, gvd)

renderer/markdown.go

@@ -0,0 +1,142 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+package renderer
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"strings"
+	"text/template"
+
+	"github.com/Masterminds/sprig"
+	"github.com/elastic/crd-ref-docs/config"
+	"github.com/elastic/crd-ref-docs/templates"
+	"github.com/elastic/crd-ref-docs/types"
+)
+
+type MarkdownRenderer struct {
+	conf *config.Config
+	*Functions
+}
+
+func NewMarkdownRenderer(conf *config.Config) (*MarkdownRenderer, error) {
+	baseFuncs, err := NewFunctions(conf)
+	if err != nil {
+		return nil, err
+	}
+	return &MarkdownRenderer{conf: conf, Functions: baseFuncs}, nil
+}
+
+func (m *MarkdownRenderer) Render(gvd []types.GroupVersionDetails) error {
+	funcMap := combinedFuncMap(funcMap{prefix: "markdown", funcs: m.ToFuncMap()}, funcMap{funcs: sprig.TxtFuncMap()})
+
+	var tpls fs.FS
+	if m.conf.TemplatesDir != "" {
+		tpls = os.DirFS(m.conf.TemplatesDir)
+	} else {
+		sub, err := fs.Sub(templates.Root, "markdown")
+		if err != nil {
+			return err
+		}
+		tpls = sub
+	}
+
+	tmpl, err := loadTemplate(tpls, funcMap)
+	if err != nil {
+		return err
+	}
+
+	f, err := createOutFile(m.conf.OutputPath, "out.md")
+	defer f.Close()
+
+	return tmpl.ExecuteTemplate(f, mainTemplate, gvd)
+}
+
+func (m *MarkdownRenderer) ToFuncMap() template.FuncMap {
+	return template.FuncMap{
+		"GroupVersionID":     m.GroupVersionID,
+		"RenderExternalLink": m.RenderExternalLink,
+		"RenderGVLink":       m.RenderGVLink,
+		"RenderLocalLink":    m.RenderLocalLink,
+		"RenderType":         m.RenderType,
+		"RenderTypeLink":     m.RenderTypeLink,
+		"SafeID":             m.SafeID,
+		"ShouldRenderType":   m.ShouldRenderType,
+		"TypeID":             m.TypeID,
+	}
+}
+
+func (m *MarkdownRenderer) ShouldRenderType(t *types.Type) bool {
+	return t != nil && (t.GVK != nil || len(t.References) > 0)
+}
+
+func (m *MarkdownRenderer) RenderType(t *types.Type) string {
+	var sb strings.Builder
+	switch t.Kind {
+	case types.MapKind:
+		sb.WriteString("object (")
+		sb.WriteString("keys:")
+		sb.WriteString(m.RenderTypeLink(t.KeyType))
+		sb.WriteString(", values:")
+		sb.WriteString(m.RenderTypeLink(t.ValueType))
+		sb.WriteString(")")
+	case types.ArrayKind, types.SliceKind:
+		sb.WriteString(m.RenderTypeLink(t.UnderlyingType))
+		sb.WriteString(" array")
+	default:
+		sb.WriteString(m.RenderTypeLink(t))
+	}
+
+	return sb.String()
+}
+
+func (m *MarkdownRenderer) RenderTypeLink(t *types.Type) string {
+	text := m.SimplifiedTypeName(t)
+
+	link, local := m.LinkForType(t)
+	if link == "" {
+		return text
+	}
+
+	if local {
+		return m.RenderLocalLink(text)
+	} else {
+		return m.RenderExternalLink(link, text)
+	}
+}
+
+func (m *MarkdownRenderer) RenderLocalLink(text string) string {
+	anchor := strings.ToLower(
+		strings.NewReplacer(
+			" ", "-",
+			".", "",
+			"/", "",
+			"(", "",
+			")", "",
+		).Replace(text),
+	)
+	return fmt.Sprintf("[%s](#%s)", text, anchor)
+}
+
+func (m *MarkdownRenderer) RenderExternalLink(link, text string) string {
+	return fmt.Sprintf("[%s](%s)", text, link)
+}
+
+func (m *MarkdownRenderer) RenderGVLink(gv types.GroupVersionDetails) string {
+	return m.RenderLocalLink(gv.GroupVersionString())
+}

renderer/renderer.go

@@ -19,6 +19,8 @@ package renderer
 import (
 	"fmt"
 	"io/fs"
+	"os"
+	"path/filepath"
 	"text/template"
 
 	"github.com/elastic/crd-ref-docs/config"
@@ -35,6 +37,8 @@ func New(conf *config.Config) (Renderer, error) {
 	switch conf.Renderer {
 	case "asciidoctor":
 		return NewAsciidoctorRenderer(conf)
+	case "markdown":
+		return NewMarkdownRenderer(conf)
 	default:
 		return nil, fmt.Errorf("unknown renderer: %s", conf.Renderer)
 	}
@@ -59,3 +63,16 @@ func combinedFuncMap(funcs ...funcMap) template.FuncMap {
 
 	return m
 }
+
+func createOutFile(outputPath string, defaultFileName string) (*os.File, error) {
+	finfo, err := os.Stat(outputPath)
+	if err != nil && !os.IsNotExist(err) {
+		return nil, err
+	}
+
+	if finfo != nil && finfo.IsDir() {
+		outputPath = filepath.Join(outputPath, defaultFileName)
+	}
+
+	return os.Create(outputPath)
+}

templates/markdown/gv_details.tpl

@@ -0,0 +1,19 @@
+{{- define "gvDetails" -}}
+{{- $gv := . -}}
+
+## {{ $gv.GroupVersionString }}
+
+{{ $gv.Doc }}
+
+{{- if $gv.Kinds  }}
+### Resource Types
+{{- range $gv.SortedKinds }}
+- {{ $gv.TypeForKind . | markdownRenderTypeLink }}
+{{- end }}
+{{ end }}
+
+{{ range $gv.SortedTypes }}
+{{ template "type" . }}
+{{ end }}
+
+{{- end -}}

templates/markdown/gv_list.tpl

@@ -0,0 +1,15 @@
+{{- define "gvList" -}}
+{{- $groupVersions := . -}}
+
+# API Reference
+
+## Packages
+{{- range $groupVersions }}
+- {{ markdownRenderGVLink . }}
+{{- end }}
+
+{{ range $groupVersions }}
+{{ template "gvDetails" . }}
+{{ end }}
+
+{{- end -}}

templates/markdown/type.tpl

@@ -0,0 +1,33 @@
+{{- define "type" -}}
+{{- $type := . -}}
+{{- if markdownShouldRenderType $type -}}
+
+#### {{ $type.Name }}
+
+{{ if $type.IsAlias }}_Underlying type:_ `{{ markdownRenderTypeLink $type.UnderlyingType  }}`{{ end }}
+
+{{ $type.Doc }}
+
+{{ if $type.References -}}
+_Appears in:_
+{{- range $type.SortedReferences }}
+- {{ markdownRenderTypeLink . }}
+{{- end }}
+{{- end }}
+
+{{ if $type.Members -}}
+| Field | Description |
+| --- | --- |
+{{ if $type.GVK -}}
+| `apiVersion` _string_ | `{{ $type.GVK.Group }}/{{ $type.GVK.Version }}`
+| `kind` _string_ | `{{ $type.GVK.Kind }}`
+{{ end -}}
+
+{{ range $type.Members -}}
+| `{{ .Name  }}` _{{ markdownRenderType .Type }}_ | {{ template "type_members" . }} |
+{{ end -}}
+
+{{ end -}}
+
+{{- end -}}
+{{- end -}}

templates/markdown/type_members.tpl

@@ -0,0 +1,8 @@
+{{- define "type_members" -}}
+{{- $field := . -}}
+{{- if eq $field.Name "metadata" -}}
+Refer to Kubernetes API documentation for fields of `metadata`.
+{{- else -}}
+{{ $field.Doc }}
+{{- end -}}
+{{- end -}}

templates/templates.go

@@ -3,4 +3,5 @@ package templates
 import "embed"
 
 //go:embed asciidoctor
+//go:embed markdown
 var Root embed.FS