optimize template loading

src/main.rs

@@ -20,7 +20,7 @@ fn main() {
         specs::compile(&args.devices, &args.env.spec_path, dbg);
 
     for spec in specifications {
-        let result = tmpls::process_templates(&spec, dbg).ok().unwrap();
+        let result = RenderedConfig::from_spec(&spec, dbg).ok().unwrap();
         output_rendered_configs(result, &args.env.out_path, dbg)
     }
 }

src/tmpls.rs

@@ -21,88 +21,87 @@ pub struct Configuration {
     pub data: String,
 }
 
-pub fn process_templates(
-    spec: &Specification,
-    dbg: LogLevel,
-) -> Result<RenderedConfig, Box<dyn std::error::Error>> {
-    // Create Tera context from spec.compiled
-    let mut context = Context::new();
-    if let Value::Object(map) = &spec.compiled {
-        if let Some(Value::Object(data_map)) = map.get("data") {
-            for (key, value) in data_map {
-                context.insert(key, value);
+impl RenderedConfig {
+    pub fn from_spec(
+        spec: &Specification,
+        dbg: LogLevel,
+    ) -> Result<Self, Box<dyn std::error::Error>> {
+        let mut context = Context::new();
+
+        // Flatten "data" map into Tera context
+        if let Some(data_map) = spec.compiled.get("data").and_then(|v| v.as_object()) {
+            for (key, val) in data_map {
+                context.insert(key, val);
             }
         }
-    }
 
-    let device_name = match context.get("hostname") {
-        Some(value) => value.as_str().unwrap_or("default_hostname"),
-        None => "default_hostname",
-    };
+        let hostname = context
+            .get("hostname")
+            .and_then(|v| v.as_str())
+            .unwrap_or("default_hostname")
+            .to_string();
 
-    // Get the base directory path
-    let base_dir = format!("./tmpl/{}", spec.get_layer());
+        let base_dir = std::path::Path::new("./tmpl").join(spec.get_layer());
 
-    // Read structure.yaml
-    let structure_path = format!("{}/structure.yaml", base_dir);
-    let structure_content: String = match fs::read_to_string(&structure_path) {
-        Ok(content) => content,
-        Err(e) => {
-            eprintln!(
-                "while attempting to read {}: {}, skipping",
-                &structure_path, e
-            );
-            String::new()
-        }
-    };
-    let config: TemplateConfig = yaml_serde::from_str(&structure_content)?;
+        // Read structure.yaml
+        let structure_path = base_dir.join("structure.yaml");
+        let structure_data = fs::read_to_string(&structure_path)
+            .map_err(|e| format!("Failed to read {}: {}", structure_path.display(), e))?;
 
-    // Initialize Tera with the specific directory
-    let mut tera = Tera::default();
+        let config_meta: TemplateConfig = yaml_serde::from_str(&structure_data)?;
 
-    // Process each template
-    info!(dbg, "Rendering {}", &device_name);
-    let mut configs = Vec::new();
-    for template_name in config.files {
-        // Read the template file directly
-        let template_path = format!("{}/{}.tera", base_dir, template_name);
-        verb!(dbg, " | {}", &template_path);
-        let template_content = match fs::read_to_string(&template_path) {
-            Ok(content) => content,
-            Err(e) => {
-                eprintln!(
-                    "while attempting to read {}: {}, skipping",
-                    &template_path, e
-                );
-                String::new()
-            }
-        };
+        let mut tera = Tera::default();
+        let mut configs = Vec::new();
 
-        // Add this specific template to Tera
-        tera.add_raw_template(&template_name, &template_content)?;
+        info!(dbg, "Rendering {}", hostname);
 
-        // Render the template
-        let rendered = tera
-            .render(&template_name, &context)
-            .inspect_err(|e| {
-                let mut chain = format!("{}", e);
-                let mut next_source = std::error::Error::source(e);
-                while let Some(source) = next_source {
-                    chain.push_str(&format!(" -> {}", source));
-                    next_source = source.source();
+        let template_data: Vec<(String, String)> = config_meta
+            .files
+            .iter()
+            .filter_map(|name| {
+                let path = base_dir.join(format!("{}.tera", name));
+                match fs::read_to_string(&path) {
+                    Ok(content) => Some((name.clone(), content)),
+                    Err(e) => {
+                        eprintln!("Skipping {}: {}", path.display(), e);
+                        None
+                    }
                 }
-                eprintln!("[tera] {}", chain);
             })
-            .unwrap_or_default();
-        configs.push(Configuration {
-            name: String::from(&template_name),
-            data: rendered,
-        });
+            .collect();
+
+        tera.add_raw_templates(template_data)?;
+
+        for template_name in &config_meta.files {
+            verb!(dbg, " | {}", &template_name);
+            if !tera.get_template_names().any(|n| n == template_name) {
+                continue;
+            }
+
+            match tera.render(template_name, &context) {
+                Ok(rendered) => configs.push(Configuration {
+                    name: template_name.clone(),
+                    data: rendered,
+                }),
+                Err(e) => Self::log_tera_error(template_name, &e),
+            }
+        }
+
+        Ok(Self {
+            hostname,
+            configs,
+            spec: spec.compiled.clone(),
+        })
     }
 
-    Ok(RenderedConfig {
-        hostname: String::from(device_name),
-        configs,
-        spec: spec.compiled.clone(),
-    })
+    /// walk the error chain
+    fn log_tera_error(name: &str, e: &tera::Error) {
+        let mut chain = e.to_string();
+        let mut source = std::error::Error::source(e);
+        while let Some(s) = source {
+            chain.push_str(&format!(" -> {}", s));
+            source = s.source();
+        }
+        eprintln!("[tera] {}: {}", name, chain);
+    }
 }