new handlebars helper for custom components: app_config

CHANGELOG.md

@@ -8,6 +8,7 @@
    - allow using `FALSE as tile_source` to completely remove the base map. This makes the map component useful to display even non-geographical geometric data.
  - Fix a bug that occured when no `database_url` was provided in the configuration file. SQLPage would generate an incorrect default SQLite database URL.
  - Add a new `background_color` attribute to the [card](https://sql.ophir.dev/documentation.sql?component=card#component) component to set the background color of the card.
+ - new handlebars helper for [custom components](https://sql.ophir.dev/custom_components.sql): `{{app_config 'property'}}` to access the configuration object from the handlebars template.
 
 ## 0.23.0 (2024-06-09)
 

examples/official-site/custom_components.sql

@@ -129,6 +129,8 @@ and SQLPage adds a few more:
    - if the argument is a string containing a valid json list, returns the parsed list,
    - otherwise returns a list containing only the argument
 - `array_contains`: returns true if a list contains a value
+- `static_path`: returns the path to one of the static files bundled with SQLPage. Accepts arguments like `sqlpage.js`, `sqlpage.css`, `apexcharts.js`, etc.
+- `app_config`: returns the value of a configuration parameter from sqlpage''s configuration file, such as `max_uploaded_file_size`, `site_prefix`, etc.
 - `icon_img`: generate an svg icon from a *tabler* icon name
 - `markdown`: renders markdown text
 - `each_row`: iterates over the rows of a query result

src/app_config.rs

@@ -2,7 +2,7 @@ use anyhow::Context;
 use config::Config;
 use percent_encoding::AsciiSet;
 use serde::de::Error;
-use serde::{Deserialize, Deserializer};
+use serde::{Deserialize, Deserializer, Serialize};
 use std::net::{SocketAddr, ToSocketAddrs};
 use std::path::{Path, PathBuf};
 
@@ -280,7 +280,7 @@ fn default_https_acme_directory_url() -> String {
     "https://acme-v02.api.letsencrypt.org/directory".to_string()
 }
 
-#[derive(Debug, Deserialize, PartialEq, Clone, Copy, Eq, Default)]
+#[derive(Debug, Deserialize, Serialize, PartialEq, Clone, Copy, Eq, Default)]
 #[serde(rename_all = "lowercase")]
 pub enum DevOrProd {
     #[default]

src/template_helpers.rs

@@ -8,6 +8,8 @@ use handlebars::{
 };
 use serde_json::Value as JsonValue;
 
+/// Simple static json helper
+type H0 = fn() -> JsonValue;
 /// Simple json to json helper
 type H = fn(&JsonValue) -> JsonValue;
 /// Simple json to json helper with error handling
@@ -41,6 +43,7 @@ pub fn register_all_helpers(h: &mut Handlebars<'_>, config: &AppConfig) {
 
     // static_path helper: generate a path to a static file. Replaces sqpage.js by sqlpage.<hash>.js
     register_helper(h, "static_path", StaticPathHelper(site_prefix.clone()));
+    register_helper(h, "app_config", AppConfigHelper(config.clone()));
 
     // icon helper: generate an image with the specified icon
     h.register_helper("icon_img", Box::new(IconImgHelper(site_prefix)));
@@ -154,6 +157,27 @@ impl CanHelp for StaticPathHelper {
     }
 }
 
+/// Generate the full path to a builtin sqlpage asset. Struct Param is the site prefix
+struct AppConfigHelper(AppConfig);
+
+impl CanHelp for AppConfigHelper {
+    fn call(&self, args: &[PathAndJson]) -> Result<JsonValue, String> {
+        let static_file = match args {
+            [v] => v.value(),
+            _ => return Err("expected one argument".to_string()),
+        };
+        let name = static_file
+            .as_str()
+            .ok_or_else(|| format!("app_config: not a string: {static_file}"))?;
+        match name {
+            "max_uploaded_file_size" => Ok(JsonValue::Number(self.0.max_uploaded_file_size.into())),
+            "environment" => serde_json::to_value(self.0.environment).map_err(|e| e.to_string()),
+            "site_prefix" => Ok(self.0.site_prefix.clone().into()),
+            other => Err(format!("unknown app config property: {other:?}")),
+        }
+    }
+}
+
 /// Generate an image with the specified icon. Struct Param is the site prefix
 struct IconImgHelper(String);
 impl HelperDef for IconImgHelper {
@@ -333,6 +357,15 @@ trait CanHelp: Send + Sync + 'static {
     fn call(&self, v: &[PathAndJson]) -> Result<JsonValue, String>;
 }
 
+impl CanHelp for H0 {
+    fn call(&self, args: &[PathAndJson]) -> Result<JsonValue, String> {
+        match args {
+            [] => Ok(self()),
+            _ => Err("expected no arguments".to_string()),
+        }
+    }
+}
+
 impl CanHelp for H {
     fn call(&self, args: &[PathAndJson]) -> Result<JsonValue, String> {
         match args {