switch config to env vars, add nix module

src/config.rs

@@ -1,9 +1,9 @@
-use serde::Deserialize;
+use std::env;
 use std::path::PathBuf;
 
-#[derive(Debug, Deserialize)]
+#[derive(Debug)]
 pub struct Config {
-    pub listen: String,
+    pub port: u16,
     pub data_dir: PathBuf,
     pub site_title: String,
     pub site_url: String,
@@ -12,10 +12,28 @@ pub struct Config {
 }
 
 impl Config {
-    pub fn load(path: &str) -> Result<Self, Box<dyn std::error::Error>> {
-        let content = std::fs::read_to_string(path)?;
-        let config: Config = toml::from_str(&content)?;
-        Ok(config)
+    pub fn listen_addr(&self) -> String {
+        format!("127.0.0.1:{}", self.port)
+    }
+
+    pub fn from_env() -> Result<Self, String> {
+        Ok(Config {
+            port: env::var("BOOK_PORT")
+                .unwrap_or_else(|_| "8123".into())
+                .parse()
+                .map_err(|_| "BOOK_PORT must be a number")?,
+            data_dir: env::var("BOOK_DATA_DIR")
+                .map(PathBuf::from)
+                .unwrap_or_else(|_| PathBuf::from("./data")),
+            site_title: env::var("BOOK_SITE_TITLE").unwrap_or_else(|_| "guestbook".into()),
+            site_url: env::var("BOOK_SITE_URL").map_err(|_| "BOOK_SITE_URL is required")?,
+            telegram_bot_token: env::var("BOOK_TELEGRAM_BOT_TOKEN")
+                .map_err(|_| "BOOK_TELEGRAM_BOT_TOKEN is required")?,
+            telegram_chat_id: env::var("BOOK_TELEGRAM_CHAT_ID")
+                .map_err(|_| "BOOK_TELEGRAM_CHAT_ID is required")?
+                .parse()
+                .map_err(|_| "BOOK_TELEGRAM_CHAT_ID must be an integer")?,
+        })
     }
 }
 
@@ -24,20 +42,54 @@ mod tests {
     use super::*;
 
     #[test]
-    fn test_parse_config() {
-        let toml_str = r#"
-listen = "127.0.0.1:8123"
-data_dir = "/var/lib/guestbook"
-site_title = "ily.rs"
-site_url = "https://ily.rs"
-telegram_bot_token = "123:ABC"
-telegram_chat_id = 12345
-"#;
-        let config: Config = toml::from_str(toml_str).unwrap();
-        assert_eq!(config.listen, "127.0.0.1:8123");
-        assert_eq!(config.data_dir, PathBuf::from("/var/lib/guestbook"));
-        assert_eq!(config.site_title, "ily.rs");
-        assert_eq!(config.site_url, "https://ily.rs");
+    fn test_from_env() {
+        env::set_var("BOOK_PORT", "9999");
+        env::set_var("BOOK_DATA_DIR", "/tmp/gb");
+        env::set_var("BOOK_SITE_TITLE", "test.rs");
+        env::set_var("BOOK_SITE_URL", "https://test.rs");
+        env::set_var("BOOK_TELEGRAM_BOT_TOKEN", "123:ABC");
+        env::set_var("BOOK_TELEGRAM_CHAT_ID", "12345");
+
+        let config = Config::from_env().unwrap();
+        assert_eq!(config.port, 9999);
+        assert_eq!(config.listen_addr(), "127.0.0.1:9999");
+        assert_eq!(config.data_dir, PathBuf::from("/tmp/gb"));
+        assert_eq!(config.site_title, "test.rs");
+        assert_eq!(config.site_url, "https://test.rs");
         assert_eq!(config.telegram_chat_id, 12345);
+
+        // Clean up
+        env::remove_var("BOOK_PORT");
+        env::remove_var("BOOK_DATA_DIR");
+        env::remove_var("BOOK_SITE_TITLE");
+        env::remove_var("BOOK_SITE_URL");
+        env::remove_var("BOOK_TELEGRAM_BOT_TOKEN");
+        env::remove_var("BOOK_TELEGRAM_CHAT_ID");
+    }
+
+    #[test]
+    fn test_defaults() {
+        env::set_var("BOOK_SITE_URL", "https://test.rs");
+        env::set_var("BOOK_TELEGRAM_BOT_TOKEN", "123:ABC");
+        env::set_var("BOOK_TELEGRAM_CHAT_ID", "12345");
+
+        let config = Config::from_env().unwrap();
+        assert_eq!(config.port, 8123);
+        assert_eq!(config.data_dir, PathBuf::from("./data"));
+        assert_eq!(config.site_title, "guestbook");
+
+        env::remove_var("BOOK_SITE_URL");
+        env::remove_var("BOOK_TELEGRAM_BOT_TOKEN");
+        env::remove_var("BOOK_TELEGRAM_CHAT_ID");
+    }
+
+    #[test]
+    fn test_missing_required() {
+        env::remove_var("BOOK_SITE_URL");
+        env::remove_var("BOOK_TELEGRAM_BOT_TOKEN");
+        env::remove_var("BOOK_TELEGRAM_CHAT_ID");
+
+        let result = Config::from_env();
+        assert!(result.is_err());
     }
 }