[v0.1.0] - Implement Minimum Viable Product

src/lib.rs

@@ -1,16 +1,24 @@
+use std::fs;
+use std::path::{Path, PathBuf};
+
+use aho_corasick::AhoCorasick;
+use anyhow::Context;
 use fancy_regex::{CaptureMatches, Captures, Regex};
 use lazy_static::lazy_static;
-use log::info;
+use log::{error, warn};
 use mdbook::book::Book;
 use mdbook::errors::Result;
 use mdbook::preprocess::{Preprocessor, PreprocessorContext};
 use mdbook::BookItem;
-use toml::Value;
+
+const ESCAPE_CHAR: char = '\\';
+const MAX_LINK_NESTED_DEPTH: usize = 10;
 
 lazy_static! {
+    // https://stackoverflow.com/questions/22871602/optimizing-regex-to-fine-key-value-pairs-space-delimited
     static ref ARGS: Regex = Regex::new(r"(?<=\s|\A)([^\s=]+)=(.*?)(?=(?:\s[^\s=]+=|$))").unwrap();
-    static ref WHOLE_TEMPLATE: Regex = Regex::new(r"\\\{\{\#.*\}\}|\{\{\s*\#([a-zA-Z0-9_]+)\s+([a-zA-Z0-9_.-/]+)\s*([^}]+)\}\}").unwrap();
-    // static ref RE: Regex = Regex::new(r"\\\{\{\#.*\}\}|\{\{\s*\#([a-zA-Z0-9_]+)\s+([a-zA-Z0-9-_.]+)\s*((?<=\s|\A)([^\s=]+)=(.*?)(?=(?:\s[^\s=]+=|$)))*\}\}").unwrap();
+    // TODO: Explain This Horrible Mess
+    static ref WHOLE_TEMPLATE: Regex = Regex::new(r"\\\{\{\#.*\}\}|\{\{\s*\#(template)\s+([a-zA-Z0-9_.\/-]+)\s*([^}]+)\}\}").unwrap();
 }
 
 #[derive(Default)]
@@ -28,29 +36,20 @@ impl Preprocessor for Template {
     }
 
     fn run(&self, ctx: &PreprocessorContext, mut book: Book) -> Result<Book> {
-        /*
-        TODO - 29/04/2022
-         Store All Files in Key/Value Pairs
-         Start iterating through each chapter in the book
-            1. Get template string
-            2. Remove }} at the end of template string
-            3. Store template string arguments in Key/Value Pairs
-            4. Get the template and dynamically find/replace
-            5. Set the chapter content to the new one
-         Return the book to mdbook
-         */
-
         env_logger::init_from_env(env_logger::Env::default().default_filter_or("info"));
-
-        if let Some(config) = ctx.config.get_preprocessor(self.name()) {
-            let default = Value::String(String::from("templates/"));
-            let template_dir = config.get("templates-dir").unwrap_or(&default);
-            info!("Reading from directory {}", template_dir);
+        let src_dir = ctx.root.join(&ctx.config.book.src);
+
+        book.for_each_mut(|section| {
+            if let BookItem::Chapter(ref mut chapter) = section {
+                if let Some(ref source) = chapter.path {
+                    let base = source
+                        .parent()
+                        .map(|dir| src_dir.join(dir))
+                        .expect("All book items have a parent");
+
+                    let content = replace(&chapter.content, base, source, 0);
+                    chapter.content = content;
                 }
-
-        book.for_each_mut(|book_item| {
-            if let BookItem::Chapter(ref mut chapter) = book_item {
-                chapter.content = String::from("All content is now replaced");
             }
         });
 
@@ -62,24 +61,149 @@ impl Preprocessor for Template {
     }
 }
 
+fn replace<P1, P2>(chapter_content: &str, base: P1, source: P2, depth: usize) -> String
+where
+    P1: AsRef<Path>,
+    P2: AsRef<Path>,
+{
+    let path = base.as_ref();
+    let source = source.as_ref();
+    // Must keep track of indices as they will not correspond after string substitution
+    let mut previous_end_index = 0;
+    let mut replaced = String::with_capacity(chapter_content.len());
+
+    for link in extract_template_links(chapter_content) {
+        replaced.push_str(&chapter_content[previous_end_index..link.start_index]);
+
+        match link.substitute_args_in_template(&path) {
+            Ok(new_content) => {
+                if depth < MAX_LINK_NESTED_DEPTH {
+                    if let Some(rel_path) = link.link_type.relative_path(path) {
+                        replaced.push_str(&replace(&new_content, rel_path, source, depth + 1));
+                    } else {
+                        replaced.push_str(&new_content);
+                    }
+                } else {
+                    error!(
+                        "Stack Overflow! {}. Check For Cyclic Templates",
+                        source.display()
+                    );
+                }
+                previous_end_index = link.end_index;
+            }
+            Err(err) => {
+                error!("Error updating \"{}\", {}", link.link_text, err);
+                for cause in err.chain().skip(1) {
+                    warn!("Caused By: {}", cause);
+                }
+
+                // Include `{{# ... }}` snippet when errors occur
+                previous_end_index = link.start_index;
+            }
+        }
+    }
+
+    replaced.push_str(&chapter_content[previous_end_index..]);
+    replaced
+}
+
+#[derive(PartialEq, Debug, Clone)]
+enum LinkType {
+    Escaped,
+    Template(PathBuf),
+}
+
+impl LinkType {
+    fn relative_path<P: AsRef<Path>>(self, base: P) -> Option<PathBuf> {
+        match self {
+            LinkType::Escaped => None,
+            LinkType::Template(p) => Some(return_relative_path(base.as_ref(), &p)),
+        }
+    }
+}
+
+fn return_relative_path<P: AsRef<Path>>(base: P, relative: P) -> PathBuf {
+    base.as_ref()
+        .join(relative)
+        .parent()
+        .expect("Included file should not be /")
+        .to_path_buf()
+}
+
+#[derive(PartialEq, Debug, Clone)]
+struct VecPair(Vec<String>, Vec<String>);
+
 #[derive(PartialEq, Debug, Clone)]
-pub struct Link<'a> {
+struct Link<'a> {
     start_index: usize,
     end_index: usize,
-    pub link_text: &'a str,
+    args: VecPair,
+    link_type: LinkType,
+    link_text: &'a str,
 }
 
 impl<'a> Link<'a> {
     fn from_capture(cap: Captures<'a>) -> Option<Link<'a>> {
+        let mut keys: Vec<String> = vec![];
+        let mut values: Vec<String> = vec![];
+
+        let link_type = match (cap.get(0), cap.get(1), cap.get(2), cap.get(3)) {
+            (_, _, Some(file), Some(args)) => {
+                let matches = ARGS.captures_iter(args.as_str());
+                for mat in matches {
+                    let capture = mat.unwrap().get(0).unwrap().as_str().splitn(2, '=');
+                    for (i, capt) in capture.enumerate() {
+                        if i % 2 == 0 {
+                            keys.push(format!("{{{}}}", capt));
+                        } else {
+                            values.push(capt.to_string());
+                        }
+                    }
+                }
+                Some(LinkType::Template(PathBuf::from(file.as_str())))
+            }
+            (Some(mat), _, _, _) if mat.as_str().starts_with(ESCAPE_CHAR) => {
+                Some(LinkType::Escaped)
+            }
+            _ => None,
+        };
+
+        link_type.and_then(|lnk_type| {
             cap.get(0).map(|mat| Link {
                 start_index: mat.start(),
                 end_index: mat.end(),
+                args: VecPair(keys, values),
+                link_type: lnk_type,
                 link_text: mat.as_str(),
             })
+        })
+    }
+
+    fn substitute_args_in_template<P: AsRef<Path>>(&self, base: P) -> Result<String> {
+        match self.link_type {
+            LinkType::Escaped => Ok((&self.link_text[1..]).to_owned()),
+            LinkType::Template(ref pat) => {
+                let target = base.as_ref().join(pat);
+
+                fs::read_to_string(&target)
+                    .with_context(|| {
+                        format!(
+                            "Could not read file for link {} ({})",
+                            self.link_text,
+                            target.display(),
+                        )
+                    })
+                    .map(|hay| {
+                        let pair = &self.args;
+                        let ac = AhoCorasick::new_auto_configured(pair.0.as_slice());
+                        ac.replace_all(hay.as_str(), pair.1.as_slice())
+                    })
+            }
+        }
     }
 }
 
-pub struct LinkIter<'a>(CaptureMatches<'a, 'a>);
+struct LinkIter<'a>(CaptureMatches<'a, 'a>);
 
 impl<'a> Iterator for LinkIter<'a> {
     type Item = Link<'a>;
@@ -93,10 +217,6 @@ impl<'a> Iterator for LinkIter<'a> {
     }
 }
 
-pub fn extract_template_links(contents: &str) -> LinkIter<'_> {
+fn extract_template_links(contents: &str) -> LinkIter<'_> {
     LinkIter(WHOLE_TEMPLATE.captures_iter(contents))
 }
-
-pub fn extract_template_arguments(contents: &str) -> LinkIter<'_> {
-    LinkIter(ARGS.captures_iter(contents))
-}