From ebc18e92a648650f3f4781ab3b015b987cf262b8 Mon Sep 17 00:00:00 2001
From: Federico Igne <git@federicoigne.com>
Date: Fri, 27 May 2022 00:42:12 +0100
Subject: feat: add maximum recursion depth on code generation

---
 src/main.rs | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 23789b6..ea4e4f7 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -17,7 +17,11 @@ type Blocks<'a> = HashMap<String,Cow<'a,str>>;
 #[derive(Parser, Debug)]
 #[clap(author, version, about, long_about = None)]
 struct Config {
-    /// Base output directory (default: './code')
+    /// Maximum substitution depth
+    #[clap(short, long, default_value_t = 10)]
+    depth: u32,
+
+    /// Base output directory [default: './code']
     #[clap(short, long)]
     output: Option<PathBuf>,
 
@@ -91,23 +95,28 @@ fn indent<'a>(input: Cow<'a,str>, indent: usize) -> Cow<'a,str> {
  * of the borrowed value `text`. Moreover `text` takes ownership of `new_text: String` using
  * the `Cow::from()` function. No heap allocation is performed, and the string is not copied.
  */
-fn build(base: &Option<PathBuf>, blocks: &Blocks) {
+fn build(base: &Option<PathBuf>, blocks: &Blocks, depth: u32) {
     lazy_static! {
         static ref PATH: Regex = Regex::new(r"^(?:[[:word:]\.-]+/)*[[:word:]\.-]+\.[[:alpha:]]+$").unwrap();
         static ref MACRO: Regex = Regex::new(r"(?m)^([[:blank:]]*)<<([^>\s]+)>>").unwrap();
     }
     blocks.iter().for_each(|(k,v)| if PATH.is_match(k) { 
+        let mut d = 0;
         let mut code = v.clone(); // No clone is happening because the value is a `Borrowed`
         // Here `replace_all` returns a `Owned` value only when a replacement takes place.
         // We can use it to recursively build blocks of code until no more substitutions are
         // necessary (i.e., `replace_all` returns a `Borrowed`).
         while let Cow::Owned(step) = MACRO.replace_all(&code, |caps: &Captures| {
-            indent(
-                blocks.get(&caps[2]).expect("Block not present").clone(),
-                caps[1].len()
-            )
+            let block = if d < depth {
+                blocks.get(&caps[2]).expect("Block not present").clone()
+            } else {
+                eprintln!("Reached maximum depth, output might be truncated. Increase `--depth` accordingly.");
+                Cow::Owned(String::from(""))
+            };
+            indent(block, caps[1].len())
         }) {
             code = Cow::from(step);
+            d += 1;
         }
         write_to_file(base, k, &code).expect("Unable to write to file");
     })
@@ -153,7 +162,7 @@ fn main() -> Result<()> {
                 }
             }
         );
-        build(&config.output, &blocks);
+        build(&config.output, &blocks, config.depth);
         pandoc
     }));
     pandoc.execute().unwrap();
-- 
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