add config manager

src/config_manager.rs

@@ -0,0 +1,82 @@
+use validator::Validate;
+
+use super::definitions::config::Config;
+use std::error::Error;
+use std::fs;
+
+const CURRENT_CONFIG_PATH: &str = "config.json";
+const PENDING_CONFIG_PATH: &str = "pending.json";
+
+pub struct ConfigManager {
+    current_config: Config,
+    pending_config: Config,
+}
+
+impl ConfigManager {
+    pub fn get_current_config(&self) -> Config {
+        self.current_config.clone()
+    }
+
+    pub fn get_pending_config(&self) -> Config {
+        self.pending_config.clone()
+    }
+
+    pub fn apply_pending_changes(&mut self) -> Result<(), Box<dyn Error>> {
+        // TODO run Apply functions, revert on failure
+        write_config_to_file(CURRENT_CONFIG_PATH, self.pending_config.clone())?;
+        // Also revert if config save fails
+        self.current_config = self.pending_config.clone();
+        Ok(())
+    }
+
+    pub fn discard_pending_changes(&mut self) -> Result<(), Box<dyn Error>> {
+        self.pending_config = self.current_config.clone();
+        Ok(())
+    }
+
+    pub fn start_transaction(&mut self) -> Result<ConfigTransaction, Box<dyn Error>> {
+        Ok(ConfigTransaction {
+            finished: false,
+            //guard: guard,
+            changes: self.pending_config.clone(),
+            config_manager: self,
+        })
+    }
+}
+
+pub struct ConfigTransaction<'a> {
+    finished: bool,
+    config_manager: &'a mut ConfigManager,
+    pub changes: Config,
+}
+
+impl<'a> ConfigTransaction<'a> {
+    pub fn commit(&mut self) -> Result<(), Box<dyn Error>> {
+        let ch = self.changes.clone();
+        ch.validate()?;
+        self.config_manager.pending_config = ch.clone();
+        Ok(())
+    }
+}
+
+pub fn new_config_manager() -> Result<ConfigManager, Box<dyn Error>> {
+    Ok(ConfigManager {
+        current_config: read_file_to_config(CURRENT_CONFIG_PATH)?,
+        pending_config: read_file_to_config(PENDING_CONFIG_PATH)?,
+    })
+}
+
+fn read_file_to_config(path: &str) -> Result<Config, Box<dyn Error>> {
+    let data = fs::read_to_string(path)?;
+    let conf: Config = serde_json::from_str(&data)?;
+    if conf.config_version != 1 {
+        // return Err("Unsupported config Version");
+    }
+    Ok(conf)
+}
+
+fn write_config_to_file(path: &str, conf: Config) -> Result<(), Box<dyn Error>> {
+    let data: String = serde_json::to_string_pretty(&conf)?;
+    fs::write(path, data)?;
+    Ok(())
+}