From 2e5403d07f86171939ab85f7b3c5e47724091ad7 Mon Sep 17 00:00:00 2001
From: Facundo Olano <facundo.olano@gmail.com>
Date: Mon, 16 Sep 2024 20:16:30 -0300
Subject: [PATCH] Add a jorge meta command to get site metadata in scripts
 (#49)

* add a jorge meta command

* add a basic metadata eval test

* fix staticcheck
---
 commands/commands.go | 22 ++++++++++++++++++++++
 main.go              |  1 +
 markup/templates.go  |  5 +++++
 site/site.go         | 34 ++++++++++++++++++++++++----------
 site/site_test.go    | 36 ++++++++++++++++++++++++++++++++++++
 5 files changed, 88 insertions(+), 10 deletions(-)

diff --git a/commands/commands.go b/commands/commands.go
index 8446c71..d4a0c20 100644
--- a/commands/commands.go
+++ b/commands/commands.go
@@ -49,3 +49,25 @@ func Prompt(label string) string {
 	}
 	return strings.TrimSpace(s)
 }
+
+type Meta struct {
+	Expression string `arg:"" name:"expression" default:"site" help:"liquid expression to be evaluated (what goes inside of {{ ... }} in templates)"`
+}
+
+// Load the site metadata and use it as context to evaluate a liquid expression
+func (cmd *Meta) Run(ctx *kong.Context) error {
+
+	config, err := config.Load(".")
+	if err != nil {
+		return err
+	}
+
+	// remove optional {{}} wrapper
+	expression := strings.Trim(cmd.Expression, " {}")
+
+	result, err := site.EvalMetadata(*config, expression)
+	if err == nil {
+		fmt.Println(result)
+	}
+	return err
+}
diff --git a/main.go b/main.go
index 898d5de..880cff6 100644
--- a/main.go
+++ b/main.go
@@ -10,6 +10,7 @@ var cli struct {
 	Build   commands.Build   `cmd:"" help:"Build a website project." aliases:"b"`
 	Post    commands.Post    `cmd:"" help:"Initialize a new post template file." aliases:"p"`
 	Serve   commands.Serve   `cmd:"" help:"Run a local server for the website." aliases:"s"`
+	Meta    commands.Meta    `cmd:"" help:"Get the JSON results from evaluating a liquid template expression within the site context." aliases:"m"`
 	Version kong.VersionFlag `short:"v"`
 }
 
diff --git a/markup/templates.go b/markup/templates.go
index 09e1aa2..32e77dc 100644
--- a/markup/templates.go
+++ b/markup/templates.go
@@ -42,6 +42,11 @@ func NewEngine(siteUrl string, includesDir string) *Engine {
 	return e
 }
 
+func EvalExpression(engine *Engine, expression string, context map[string]interface{}) (string, error) {
+	template := fmt.Sprintf("{{ %s | json }}", expression)
+	return engine.ParseAndRenderString(template, context)
+}
+
 // Try to parse a liquid template at the given location.
 // Files starting with front matter (--- sorrrounded yaml)
 // are considered templates. If the given file is not headed by front matter
diff --git a/site/site.go b/site/site.go
index ddd783c..0229a4f 100644
--- a/site/site.go
+++ b/site/site.go
@@ -49,6 +49,16 @@ func Build(config config.Config) error {
 	return site.build()
 }
 
+// Parse and render the given liquid expression, eg. " site.posts | map:title "
+// and return the results as a json string.
+func EvalMetadata(config config.Config, expression string) (string, error) {
+	site, err := load(config)
+	if err != nil {
+		return "", err
+	}
+	return markup.EvalExpression(site.templateEngine, expression, site.AsContext())
+}
+
 // Create a new site instance by scanning the project directories
 // pointed by `config`, loading layouts, templates and data files.
 func load(config config.Config) (*site, error) {
@@ -374,16 +384,7 @@ func (site *site) buildFile(path string) error {
 }
 
 func (site *site) render(templ *markup.Template) ([]byte, error) {
-	ctx := map[string]interface{}{
-		"site": map[string]interface{}{
-			"config":       site.config.AsContext(),
-			"posts":        site.posts,
-			"tags":         site.tags,
-			"pages":        site.pages,
-			"static_files": site.static_files,
-			"data":         site.data,
-		},
-	}
+	ctx := site.AsContext()
 
 	ctx["page"] = templ.Metadata
 	content, err := templ.RenderWith(ctx, site.config.HighlightTheme)
@@ -410,6 +411,19 @@ func (site *site) render(templ *markup.Template) ([]byte, error) {
 	return content, nil
 }
 
+func (site *site) AsContext() map[string]interface{} {
+	return map[string]interface{}{
+		"site": map[string]interface{}{
+			"config":       site.config.AsContext(),
+			"posts":        site.posts,
+			"tags":         site.tags,
+			"pages":        site.pages,
+			"static_files": site.static_files,
+			"data":         site.data,
+		},
+	}
+}
+
 func checkFileError(err error) error {
 	// When walking the source dir it can happen that a file is present when walking starts
 	// but missing or inaccessible when trying to open it (this is particularly frequent with
diff --git a/site/site_test.go b/site/site_test.go
index d7bbcd8..417ffdd 100644
--- a/site/site_test.go
+++ b/site/site_test.go
@@ -271,6 +271,42 @@ date: 2023-01-01
 </ul>`)
 }
 
+func TestEvalMetadata(t *testing.T) {
+	config := newProject()
+	defer os.RemoveAll(config.RootDir)
+
+	content := `---
+title: hello world!
+date: 2024-01-01
+---
+<p>Hello world!</p>`
+	file := newFile(config.SrcDir, "hello.html", content)
+	defer os.Remove(file.Name())
+
+	content = `---
+title: goodbye!
+date: 2024-02-01
+---
+<p>goodbye world!</p>`
+	file = newFile(config.SrcDir, "goodbye.html", content)
+	defer os.Remove(file.Name())
+
+	content = `---
+title: an oldie!
+date: 2023-01-01
+---
+<p>oldie</p>`
+	file = newFile(config.SrcDir, "an-oldie.html", content)
+	defer os.Remove(file.Name())
+
+	output, err := EvalMetadata(*config, "site.posts | map:'title'")
+	assertEqual(t, err, nil)
+	assertEqual(t, output, `["goodbye!","hello world!","an oldie!"]`)
+
+	_, err = EvalMetadata(*config, "site.posts | map:'title")
+	assert(t, strings.Contains(err.Error(), "Liquid error"))
+}
+
 func TestRenderTags(t *testing.T) {
 	config := newProject()
 	defer os.RemoveAll(config.RootDir)