A few straggling files that got left out of the prior commit

styles/src/engine.rs

@@ -0,0 +1,123 @@
+//! Implements a Theme Engine. This behaves a bit differently depending on 
+//! the mode your application is compiled in.
+//!
+//! - In `debug`, it scans a few places and loads any CSS files that are 
+//! necessary. It will also hot-reload CSS files as they change.
+//! - In `release`, it scans those same places, and compiles your CSS into 
+//! your resulting binary. The hot-reloading functionality is not in release, 
+//! however it can be enabled if desired.
+//!
+
+use std::fs;
+use std::env;
+use std::sync::RwLock;
+use std::path::PathBuf;
+use std::collections::HashMap;
+
+use toml;
+use serde::Deserialize;
+
+use crate::StylesList;
+use crate::styles::Style;
+use crate::stylesheet::StyleSheet;
+
+static CONFIG_FILE_NAME: &str = "alchemy.toml";
+
+#[derive(Debug, Deserialize)]
+struct RawConfig<'d> {
+    #[serde(borrow)]
+    general: Option<General<'d>>,
+}
+
+#[derive(Debug, Deserialize)]
+struct General<'a> {
+    #[serde(borrow)]
+    dirs: Option<Vec<&'a str>>
+}
+
+/// The `ThemeEngine` controls loading themes and registering associated
+/// styles.
+#[derive(Debug)]
+pub struct ThemeEngine {
+    pub dirs: Vec<PathBuf>,
+    pub themes: RwLock<HashMap<String, StyleSheet>>
+}
+
+impl ThemeEngine {
+    /// Creates a new 'ThemeEngine` instance.
+    pub fn new() -> ThemeEngine {
+        // This env var is set by Cargo... so if this code breaks, there's
+        // bigger concerns, lol
+        let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
+
+        let root = PathBuf::from(manifest_dir);
+        let default_dirs = vec![root.join("themes")];
+        
+        let toml_contents = read_config_file();
+        let raw: RawConfig<'_> = toml::from_str(&toml_contents).expect(&format!("Invalid TOML in {}!", CONFIG_FILE_NAME));
+
+        let dirs = match raw.general {
+            Some(General { dirs }) => (
+                dirs.map_or(default_dirs, |v| {
+                    v.into_iter().map(|dir| root.join(dir)).collect()
+                })
+            ),
+
+            None => default_dirs
+        };
+
+        ThemeEngine { dirs, themes: RwLock::new(HashMap::new()) }
+    }
+
+    /// Registers a stylesheet (typically created by the `styles! {}` macro) for a given
+    /// theme.
+    pub fn register_styles(&self, key: &str, stylesheet: StyleSheet) {
+        let mut themes = self.themes.write().unwrap();
+        if !themes.contains_key(key) {
+            themes.insert(key.to_string(), stylesheet);
+            return;
+        }
+
+        // if let Some(existing_stylesheet) = self.themes.get_mut(key) {
+        //    *existing_stylesheet.merge(stylesheet);
+        //}
+    }
+
+    /// Given a theme key, style keys, and a style, configures the style for layout
+    /// and appearance.
+    pub fn configure_style_for_keys_in_theme(&self, theme: &str, keys: &StylesList, style: &mut Style) {
+        let themes = self.themes.read().unwrap();
+
+        match themes.get(theme) {
+            Some(theme) => {
+                for key in &keys.0 {
+                    theme.apply_styles(key, style);
+                }
+            },
+
+            None => {
+                eprintln!("No styles for theme!");
+            }
+        }
+    }
+
+    /// The same logic as `configure_style_for_keys_in_theme`, but defaults to the default theme.
+    pub fn configure_style_for_keys(&self, keys: &StylesList, style: &mut Style) {
+        self.configure_style_for_keys_in_theme("default", keys, style)
+    }
+}
+
+/// Utility method for reading a config file from the `CARGO_MANIFEST_DIR`. Hat tip to 
+/// [askama](https://github.com/djc/askama) for this!
+pub fn read_config_file() -> String {
+    let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
+    let root = PathBuf::from(manifest_dir);
+    let filename = root.join(CONFIG_FILE_NAME);
+
+    if filename.exists() {
+        fs::read_to_string(&filename)
+            .expect(&format!("Unable to read {}", filename.to_str().unwrap()))
+    } else {
+        "".to_string()
+    }
+}