add site-wide JS caching through import maps

crates/treehouse/src/import_map.rs

@@ -0,0 +1,64 @@
+use std::{collections::HashMap, ffi::OsStr, path::PathBuf};
+
+use log::warn;
+use serde::{Deserialize, Serialize};
+use walkdir::WalkDir;
+
+use crate::static_urls::StaticUrls;
+
+#[derive(Debug, Clone, Serialize)]
+pub struct ImportMap {
+    pub imports: HashMap<String, String>,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct ImportRoot {
+    pub name: String,
+    pub path: String,
+}
+
+impl ImportMap {
+    pub fn generate(base_url: String, import_roots: &[ImportRoot]) -> Self {
+        let mut import_map = ImportMap {
+            imports: HashMap::new(),
+        };
+
+        for root in import_roots {
+            let static_urls = StaticUrls::new(
+                PathBuf::from(&root.path),
+                format!("{base_url}/{}", root.path),
+            );
+            for entry in WalkDir::new(&root.path) {
+                let entry = match entry {
+                    Ok(entry) => entry,
+                    Err(error) => {
+                        warn!("directory walk failed: {error}");
+                        continue;
+                    }
+                };
+
+                if !entry.file_type().is_dir() && entry.path().extension() == Some(OsStr::new("js"))
+                {
+                    let normalized_path = entry
+                        .path()
+                        .strip_prefix(&root.path)
+                        .unwrap_or(entry.path())
+                        .to_string_lossy()
+                        .replace('\\', "/");
+                    match static_urls.get(&normalized_path) {
+                        Ok(url) => {
+                            import_map
+                                .imports
+                                .insert(format!("{}/{normalized_path}", root.name), url);
+                        }
+                        Err(error) => {
+                            warn!("could not get static url for {normalized_path}: {error}")
+                        }
+                    }
+                }
+            }
+        }
+
+        import_map
+    }
+}