Update version.

Add `directives` explanation to README. Fix that markdown directive wasn't being added to Vector. Abstract markdown mutation out of `create_variable` into the main method to handle mutating of any variable, not just content. Change parser to always add markdown if variable is named `content`.
BritishWerewolf · Mar 27, 2024 · 092580e · 092580e
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diff --git a/Cargo.toml b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "blogs-md-easy"
 description = "Iteratively convert a collection of Markdown files into a respective HTML template."
-version = "0.1.5"
+version = "0.2.0"
 edition = "2021"
 keywords = ["markdown", "html", "template", "blog"]
 categories = ["command-line-interface", "config", "web-programming"]

diff --git a/README.md b/README.md
@@ -66,6 +66,62 @@ Variables can be reused as many times as required, and will be replaced, providi
 
 Finally, the `£content` variable is automatically generated based on the entire body of the Markdown file.
 
+#### Directives
+It's possible to mutate the placeholders during rendering by providing directives.  
+A directive is just a way of applying a pre-defined function to any placeholder variable.
+
+Let's use our previous template, and apply a simple directive to the `£title` variable.
+```html
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="description" content="{{ £description }}">
+
+    <title>{{ £title }}</title>
+</head>
+<body>
+    <section>
+        <h1>{{ £title | uppercase }}</h1>
+        <p>Authored by {{ £author }}</p>
+    </section>
+    <section>{{ £content }}</section>
+</body>
+</html>
+```
+By providing the function after a pipe (`|`) character, we can mutate that variable in that particular location. This is particularly useful in cases where a placeholder is required multiple times through a template, but the formatting should be different in all cases.
+
+There are currently three supported directives:
+* `lowercase` - Convert the value to lowercase.
+* `uppercase` - Convert the value to uppercase.
+* `markdown` - Convert the value from Markdown into HTML.
+
+By default, no directives will be provided, unless specified within the template, with the exception of `£content` which will have `markdown` applied.
+
+Directives are case insensitive, meaning `| uppercase` is the same as `| UPPERCASE`. They can also be chained together, such as in the following example.
+```html
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="description" content="{{ £description }}">
+
+    <title>{{ £title }}</title>
+</head>
+<body>
+    <section>
+        {{ £title | uppercase | markdown }}
+        <p>Authored by {{ £author }}</p>
+    </section>
+    <section>{{ £content }}</section>
+</body>
+</html>
+```
+Here we are converting the title to uppercase, and then mutating the value into markdown.  
+Chained directives are evaluated from left to right.
+
 ### Markdowns
 [Markdowns](https://daringfireball.net/projects/markdown) are simple text files that contain any text, and an optional `meta` section.
 
@@ -171,7 +227,8 @@ Currently, a new line is placed before all headings (from `h2` to to `h6`), but
 
 ## Todo List
 - [ ] Add if statements to render content based on a condition.
-- [ ] Add directives to placeholders.
+- [x] Add directives to placeholders.
+    - [ ] Add directives that support arguments.
 - [ ] Add tag filter to prevent parsing scripts.
 - [ ] Add better handling for errors in meta sections.
     - For example if a key is passed without a value, then no meta values are parsed.

diff --git a/src/main.rs b/src/main.rs
@@ -361,6 +361,7 @@ fn parse_placeholder_directive_enum(input: Span) -> IResult<Span, Option<Directi
         "date" => arg.and_then(|arg| Some(Directive::Date(arg.to_string()))),
         "lowercase" => Some(Directive::Lowercase),
         "uppercase" => Some(Directive::Uppercase),
+        "markdown"  => Some(Directive::Markdown),
         _ => None,
     };
     Ok((input, directive))
@@ -411,7 +412,12 @@ fn parse_placeholder(input: Span) -> IResult<Span, Placeholder> {
         many0(parse_placeholder_directive),
         tuple((multispace0, tag("}}"))),
     ))(input)
-    .map(|(input, (start, variable, directives, end))| {
+    .map(|(input, (start, variable, mut directives, end))| {
+        // By default, £content will always be parsed as Markdown.
+        if variable.to_ascii_lowercase().as_str() == "content" && !directives.contains(&Some(Directive::Markdown)) {
+            directives.push(Some(Directive::Markdown));
+        }
+
         (input, Placeholder {
             name: variable.to_string(),
             directives: directives.into_iter().filter_map(|d| d).collect(),
@@ -535,14 +541,6 @@ fn create_variables(markdown: Span, meta_values: Vec<Option<Meta>>) -> Result<Ha
     }
     if !variables.contains_key("content") {
         let content = markdown.fragment().trim().to_string();
-        let content = markdown::to_html_with_options(&content, &markdown::Options {
-            compile: markdown::CompileOptions {
-                allow_dangerous_html: true,
-                allow_dangerous_protocol: false,
-                ..Default::default()
-            },
-            ..Default::default()
-        }).unwrap_or_default();
         variables.insert("content".to_string(), content);
     }
 
@@ -567,7 +565,7 @@ fn main() -> Result<(), anyhow::Error> {
     // Get only existing markdowns.
     let markdown_urls: Vec<PathBuf> = cli.markdowns
         .into_iter()
-        .filter(|file| file.exists() && file.extension().unwrap_or_default() == "md" )
+        .filter(|file| file.exists() && file.extension().unwrap_or_default() == "md")
         .collect();
     let markdowns: Vec<String> = markdown_urls
         .iter()
@@ -602,6 +600,27 @@ fn main() -> Result<(), anyhow::Error> {
 
         for placeholder in &placeholders {
             if let Some(variable) = variables.get(&placeholder.name) {
+                // Used to deref the variable.
+                let mut variable = variable.to_owned();
+
+                for directive in &placeholder.directives {
+                    variable = match directive {
+                        Directive::Lowercase => variable.to_lowercase(),
+                        Directive::Uppercase => variable.to_uppercase(),
+                        Directive::Markdown  => {
+                            markdown::to_html_with_options(&variable, &markdown::Options {
+                                compile: markdown::CompileOptions {
+                                    allow_dangerous_html: true,
+                                    allow_dangerous_protocol: false,
+                                    ..Default::default()
+                                },
+                                ..Default::default()
+                            }).unwrap_or_default()
+                        }
+                        _ => unimplemented!(),
+                    }
+                }
+
                 html_doc = replace_substring(&html_doc, placeholder.selection.start.offset, placeholder.selection.end.offset, &variable);
             } else {
                 let url = markdown_url.to_str().unwrap_or_default();