From 5a84e1bde773bdc782c1db5a633ef8765f220253 Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Mon, 30 Oct 2023 18:45:13 +0200
Subject: feat: allow .subplot to list CSS files to embed in HTML output

This is in the meta data field "css_embed".

Signed-off-by: Lars Wirzenius <liw@liw.fi>
Sponsored-by: author
---
 src/doc.rs      |  3 +++
 src/metadata.rs | 19 +++++++++++++++++++
 subplot.md      | 45 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 67 insertions(+)

diff --git a/src/doc.rs b/src/doc.rs
index f3f9641..83b5ec2 100644
--- a/src/doc.rs
+++ b/src/doc.rs
@@ -155,6 +155,9 @@ impl Document {
 
         let mut css = Element::new(ElementTag::Style);
         css.push_child(Content::Text(CSS.into()));
+        for css_file in self.meta.css_embed() {
+            css.push_child(Content::Text(css_file.into()));
+        }
         head.push_child(Content::Elt(css));
 
         self.meta.set_date(date.into());
diff --git a/src/metadata.rs b/src/metadata.rs
index e3463b3..dc28ac4 100644
--- a/src/metadata.rs
+++ b/src/metadata.rs
@@ -50,6 +50,7 @@ pub struct YamlMetadata {
     documentclass: Option<String>,
     #[serde(default)]
     impls: BTreeMap<String, Vec<PathBuf>>,
+    css_embed: Option<Vec<PathBuf>>,
 }
 
 impl YamlMetadata {
@@ -167,6 +168,7 @@ pub struct Metadata {
     impls: HashMap<String, DocumentImpl>,
     /// Extra class names which should be considered 'correct' for this document
     classes: Vec<String>,
+    css_embed: Vec<String>,
 }
 
 #[derive(Debug)]
@@ -208,6 +210,17 @@ impl Metadata {
             vec![]
         };
 
+        let mut css_embed = vec![];
+        if let Some(filenames) = &yaml.css_embed {
+            for filename in filenames.iter() {
+                let css = std::fs::read(filename)
+                    .map_err(|e| SubplotError::ReadFile(filename.into(), e))?;
+                let css = String::from_utf8(css)
+                    .map_err(|e| SubplotError::FileUtf8(filename.into(), e))?;
+                css_embed.push(css);
+            }
+        }
+
         let meta = Self {
             basedir: basedir.as_ref().to_path_buf(),
             title: yaml.title().into(),
@@ -218,6 +231,7 @@ impl Metadata {
             bindings,
             impls,
             classes,
+            css_embed,
         };
         trace!("metadata: {:#?}", meta);
 
@@ -278,6 +292,11 @@ impl Metadata {
     pub fn classes(&self) -> impl Iterator<Item = &str> {
         self.classes.iter().map(Deref::deref)
     }
+
+    /// Contents of CSS files to embed into the HTML output.
+    pub fn css_embed(&self) -> impl Iterator<Item = &str> {
+        self.css_embed.iter().map(Deref::deref)
+    }
 }
 
 impl DocumentImpl {
diff --git a/subplot.md b/subplot.md
index 06e9e38..6532614 100644
--- a/subplot.md
+++ b/subplot.md
@@ -3639,6 +3639,51 @@ markdowns:
 ~~~
 ~~~~~~
 
+## HTML output
+
+### Embedded CSS
+
+_Requirement:_ The user can specify CSS files to embed in the HTML
+output.
+
+Justification: We want to allow production of self-standing output
+with user-defined styling.
+
+~~~scenario
+given file embedded-css.subplot
+given file embedded-css.md
+given file embedded-css.css
+given file b.yaml
+given an installed subplot
+when I run subplot docgen embedded-css.subplot -o foo.html
+then file foo.html contains "silly: property;"
+~~~
+
+~~~{#embedded-css.subplot .file .yaml .numberLines}
+title: Embedded CSS
+markdowns:
+  - embedded-css.md
+bindings:
+  - b.yaml
+css_embed:
+ - embedded-css.css
+~~~
+
+~~~~~~{#embedded-css.md .file .markdown .numberLines}
+# This is a title
+
+~~~scenario
+given precondition
+~~~
+~~~~~~
+
+~~~{#embedded-css.css .file .css .numberLines}
+html {
+    silly: property;
+}
+~~~
+
+
 ## Running Subplot
 
 The scenarios in this section verify that the Subplot tool can be run
-- 
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