Code drill feature parity, downloading snippets from github

Phase 1 and 2. Phase 3 will allow custom github repo input.

src/config.rs

@@ -26,6 +26,14 @@ pub struct Config {
     pub passage_paragraphs_per_book: usize,
     #[serde(default = "default_passage_onboarding_done")]
     pub passage_onboarding_done: bool,
+    #[serde(default = "default_code_downloads_enabled")]
+    pub code_downloads_enabled: bool,
+    #[serde(default = "default_code_download_dir")]
+    pub code_download_dir: String,
+    #[serde(default = "default_code_snippets_per_repo")]
+    pub code_snippets_per_repo: usize,
+    #[serde(default = "default_code_onboarding_done")]
+    pub code_onboarding_done: bool,
 }
 
 fn default_target_wpm() -> u32 {
@@ -63,6 +71,23 @@ fn default_passage_paragraphs_per_book() -> usize {
 fn default_passage_onboarding_done() -> bool {
     false
 }
+fn default_code_downloads_enabled() -> bool {
+    false
+}
+fn default_code_download_dir() -> String {
+    dirs::data_dir()
+        .unwrap_or_else(|| PathBuf::from("."))
+        .join("keydr")
+        .join("code")
+        .to_string_lossy()
+        .to_string()
+}
+fn default_code_snippets_per_repo() -> usize {
+    200
+}
+fn default_code_onboarding_done() -> bool {
+    false
+}
 
 impl Default for Config {
     fn default() -> Self {
@@ -77,6 +102,10 @@ impl Default for Config {
             passage_download_dir: default_passage_download_dir(),
             passage_paragraphs_per_book: default_passage_paragraphs_per_book(),
             passage_onboarding_done: default_passage_onboarding_done(),
+            code_downloads_enabled: default_code_downloads_enabled(),
+            code_download_dir: default_code_download_dir(),
+            code_snippets_per_repo: default_code_snippets_per_repo(),
+            code_onboarding_done: default_code_onboarding_done(),
         }
     }
 }
@@ -114,4 +143,97 @@ impl Config {
     pub fn target_cpm(&self) -> f64 {
         self.target_wpm as f64 * 5.0
     }
+
+    /// Validate `code_language` against known options, resetting to default if invalid.
+    /// Call after deserialization to handle stale/renamed keys from old configs.
+    pub fn normalize_code_language(&mut self, valid_keys: &[&str]) {
+        // Backwards compatibility: old "shell" key is now "bash".
+        if self.code_language == "shell" {
+            self.code_language = "bash".to_string();
+        }
+        if !valid_keys.contains(&self.code_language.as_str()) {
+            self.code_language = default_code_language();
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_config_serde_defaults_from_empty() {
+        // Simulates loading an old config file with no code drill fields
+        let config: Config = toml::from_str("").unwrap();
+        assert_eq!(config.code_downloads_enabled, false);
+        assert_eq!(config.code_snippets_per_repo, 200);
+        assert_eq!(config.code_onboarding_done, false);
+        assert!(!config.code_download_dir.is_empty());
+        assert!(config.code_download_dir.contains("code"));
+    }
+
+    #[test]
+    fn test_config_serde_defaults_from_old_fields_only() {
+        // Simulates a config file that only has pre-existing fields
+        let toml_str = r#"
+target_wpm = 60
+theme = "monokai"
+code_language = "go"
+"#;
+        let config: Config = toml::from_str(toml_str).unwrap();
+        assert_eq!(config.target_wpm, 60);
+        assert_eq!(config.theme, "monokai");
+        assert_eq!(config.code_language, "go");
+        // New fields should have defaults
+        assert_eq!(config.code_downloads_enabled, false);
+        assert_eq!(config.code_snippets_per_repo, 200);
+        assert_eq!(config.code_onboarding_done, false);
+    }
+
+    #[test]
+    fn test_config_serde_roundtrip() {
+        let config = Config::default();
+        let serialized = toml::to_string_pretty(&config).unwrap();
+        let deserialized: Config = toml::from_str(&serialized).unwrap();
+        assert_eq!(config.code_downloads_enabled, deserialized.code_downloads_enabled);
+        assert_eq!(config.code_download_dir, deserialized.code_download_dir);
+        assert_eq!(config.code_snippets_per_repo, deserialized.code_snippets_per_repo);
+        assert_eq!(config.code_onboarding_done, deserialized.code_onboarding_done);
+    }
+
+    #[test]
+    fn test_normalize_code_language_valid_key_unchanged() {
+        let mut config = Config::default();
+        config.code_language = "python".to_string();
+        let valid_keys = vec!["rust", "python", "javascript", "go", "all"];
+        config.normalize_code_language(&valid_keys);
+        assert_eq!(config.code_language, "python");
+    }
+
+    #[test]
+    fn test_normalize_code_language_invalid_key_resets() {
+        let mut config = Config::default();
+        config.code_language = "haskell".to_string();
+        let valid_keys = vec!["rust", "python", "javascript", "go", "all"];
+        config.normalize_code_language(&valid_keys);
+        assert_eq!(config.code_language, "rust");
+    }
+
+    #[test]
+    fn test_normalize_code_language_empty_string_resets() {
+        let mut config = Config::default();
+        config.code_language = String::new();
+        let valid_keys = vec!["rust", "python", "javascript", "go", "all"];
+        config.normalize_code_language(&valid_keys);
+        assert_eq!(config.code_language, "rust");
+    }
+
+    #[test]
+    fn test_normalize_code_language_shell_maps_to_bash() {
+        let mut config = Config::default();
+        config.code_language = "shell".to_string();
+        let valid_keys = vec!["rust", "python", "javascript", "go", "bash", "all"];
+        config.normalize_code_language(&valid_keys);
+        assert_eq!(config.code_language, "bash");
+    }
 }