From 517cabe8ec54d0bf5f5f9cc9089d76a1fad7bb6a Mon Sep 17 00:00:00 2001
From: Minijackson <minijackson@riseup.net>
Date: Sun, 7 Nov 2021 23:09:34 +0100
Subject: initial commit with PoC

---
 src/filters.rs | 115 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 src/filters.rs

(limited to 'src/filters.rs')

diff --git a/src/filters.rs b/src/filters.rs
new file mode 100644
index 0000000..1b06920
--- /dev/null
+++ b/src/filters.rs
@@ -0,0 +1,115 @@
+use std::{collections::HashMap, path::Path};
+
+use log::trace;
+use pandoc_ast::MutVisitor;
+
+// If a link points to `./a/b/c.ext`, and a file in the output directory `pdbook/./a/b/c.html`
+// exists, rewrite that link.
+pub struct RelativizeUrls<'a> {
+    pub config: &'a crate::config::Config,
+    pub extension: &'a str,
+    pub build_dir: &'a Path,
+    pub source_dir: &'a Path,
+}
+
+impl<'a> pandoc_ast::MutVisitor for RelativizeUrls<'a> {
+    fn walk_inline(&mut self, inline: &mut pandoc_ast::Inline) {
+        let link = match inline {
+            pandoc_ast::Inline::Link(_, _, target) => &mut target.0,
+            _ => return,
+        };
+
+        if link.starts_with('#') || link.contains("://") {
+            return;
+        }
+
+        let link_path = self.source_dir.join(&link);
+
+        if link_path.is_absolute() {
+            return;
+        }
+
+        let mut output_path = self.build_dir.join(&link_path);
+        if !output_path.set_extension(self.extension) {
+            return;
+        }
+
+        trace!("Checking output_path: {:?}", output_path);
+
+        // TODO: warn when referencing a "markdown or other" file not specified in the summary
+        if output_path.exists() {
+            // TODO: relativize from URL root
+
+            trace!("Relativizing link '{}'", link_path.display());
+
+            *link = Path::new(link)
+                .with_extension(&self.extension)
+                .to_str()
+                .expect("Path constructed from UTF-8 valid strings in not UTF-8 valid")
+                .to_string();
+
+            trace!("-> into '{}'", link);
+        }
+    }
+}
+
+// Applied just to the summary
+pub struct RelativizeSummary {
+    level: usize,
+}
+
+impl pandoc_ast::MutVisitor for RelativizeSummary {
+    fn walk_inline(&mut self, inline: &mut pandoc_ast::Inline) {
+        if self.level == 0 {
+            return;
+        }
+
+        let link = match inline {
+            pandoc_ast::Inline::Link(_, _, target) => &mut target.0,
+            _ => return,
+        };
+
+        // Assume link is to a managed file
+        for _ in 0..self.level {
+            link.insert_str(0, "../");
+        }
+    }
+}
+
+pub fn relativize_summary(summary: &pandoc_ast::Pandoc, level: usize) -> pandoc_ast::Pandoc {
+    use std::sync::RwLock;
+
+    lazy_static::lazy_static! {
+        static ref CACHE: RwLock<HashMap<usize, pandoc_ast::Pandoc>> = RwLock::new(HashMap::new());
+    }
+
+    CACHE
+        .write()
+        .expect("Relativized summary cache poison")
+        .entry(level)
+        .or_insert_with(|| {
+            let mut summary = summary.clone();
+            RelativizeSummary { level }.walk_pandoc(&mut summary);
+            summary
+        })
+        .clone()
+}
+
+pub struct InsertSummary<'a> {
+    pub summary: &'a pandoc_ast::Pandoc,
+    pub level: usize,
+}
+
+impl<'a> pandoc_ast::MutVisitor for InsertSummary<'a> {
+    fn walk_pandoc(&mut self, pandoc: &mut pandoc_ast::Pandoc) {
+        let summary = relativize_summary(self.summary, self.level);
+
+        pandoc.blocks.insert(
+            0,
+            pandoc_ast::Block::Div(
+                (String::new(), vec!["summary".to_string()], vec![]),
+                summary.blocks,
+            ),
+        );
+    }
+}
-- 
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