Implement reading and writing of config files

tools/yabridgectl/src/config.rs

@@ -14,13 +14,21 @@
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+use serde_derive::{Deserialize, Serialize};
+use std::fs;
 use std::path::{Path, PathBuf};
 use xdg::BaseDirectories;
 
+/// The name of the config file, relative to `$XDG_CONFIG_HOME/CONFIG_PREFIX`.
+const CONFIG_FILE_NAME: &str = "config.toml";
+/// The name of the configuration directory, relative to `$XDG_CONFIG_HOME`.
+const CONFIG_PREFIX: &str = "yabridgectl";
+
 const LIBYABRIDGE_NAME: &str = "libyabridge.so";
 
 /// The configuration used for yabridgectl. This will be serialized to and deserialized from
 /// `$XDG_CONFIG_HOME/yabridge/config.toml`.
+#[derive(Deserialize, Serialize, Debug)]
 pub struct Config {
     /// The installation method to use. We will default to creating copies since that works
     /// everywehre.
@@ -34,6 +42,55 @@ pub struct Config {
 }
 
 impl Config {
+    /// Try to read the config file, creating a new default file if necessary. This will fail if the
+    /// file could not be created or if it could not be parsed.
+    pub fn read() -> Result<Config, String> {
+        match base_directories()?.find_config_file(CONFIG_FILE_NAME) {
+            Some(path) => {
+                let toml_str = fs::read_to_string(&path).map_err(|err| {
+                    format!(
+                        "Could not read config file at '{}': {}",
+                        path.display(),
+                        err
+                    )
+                })?;
+
+                Ok(toml::from_str(&toml_str)
+                    .map_err(|err| format!("Could not parse TOML: {:#?}", err))?)
+            }
+            None => {
+                let defaults = Config {
+                    method: InstallationMethod::Copy,
+                    yabridge_home: None,
+                    plugin_dirs: Vec::new(),
+                };
+
+                // If no existing config file exists, then write a new config file with default
+                // values
+                defaults.write()?;
+
+                Ok(defaults)
+            }
+        }
+    }
+
+    /// Write the config to disk, creating the file if it does not yet exist.
+    pub fn write(&self) -> Result<(), String> {
+        let toml_str = toml::to_string_pretty(&self)
+            .map_err(|err| format!("Could not format TOML: {}", err))?;
+        let config_file = base_directories()?
+            .place_config_file(CONFIG_FILE_NAME)
+            .map_err(|err| format!("Could not write config file: {}", err))?;
+
+        fs::write(&config_file, toml_str).map_err(|err| {
+            format!(
+                "Could not write config file to '{}': {}",
+                config_file.display(),
+                err
+            )
+        })
+    }
+
     /// Return the path to `libyabridge.so`, or a descriptive error if it can't be found. If
     /// `yabridge_home` is `None`, then we'll search in both `/usr/lib` and
     /// `$XDG_DATA_HOME/yabridge`.
@@ -54,9 +111,7 @@ impl Config {
             None => {
                 // Search in the two common installation locations if no path was set explicitely
                 let system_path = Path::new("/usr/lib");
-                let user_path = BaseDirectories::new()
-                    .map_err(|err| format!("Error while parsing base directories:\n{}", err))?
-                    .get_data_home();
+                let user_path = base_directories()?.get_data_home();
                 for directory in &[system_path, &user_path] {
                     let candidate = directory.join(LIBYABRIDGE_NAME);
                     if candidate.exists() {
@@ -77,6 +132,8 @@ impl Config {
 }
 
 /// Specifies how yabridge will be set up for the found plugins.
+#[derive(Deserialize, Serialize, Debug)]
+#[serde(rename_all = "snake_case")]
 pub enum InstallationMethod {
     /// Create a copy of `libyabridge.so` for every Windows VST2 plugin .dll file found. After
     /// updating yabridge, the user will have to rerun `yabridgectl sync` to copy over the new
@@ -87,3 +144,10 @@ pub enum InstallationMethod {
     /// modify the `PATH` environment variable.
     Symlink,
 }
+
+/// Fetch the XDG base directories, converting any error messages if this somehow fails into a
+/// printable string to reduce boiler plate.
+fn base_directories() -> Result<BaseDirectories, String> {
+    BaseDirectories::with_prefix(CONFIG_PREFIX)
+        .map_err(|err| format!("Error while parsing base directories: {}", err))
+}

tools/yabridgectl/src/main.rs

@@ -16,6 +16,21 @@
 
 mod config;
 
+use config::Config;
+
 fn main() {
-    println!("Hello, world!");
+    // TODO: Remove debug
+    match Config::read() {
+        Ok(config) => {
+            println!("Read config:\n\n{:#?}\n", config);
+            println!(
+                "Searching for libyabridge.toml:\n\n{:?}",
+                config.libyabridge()
+            );
+        }
+        Err(err) => {
+            eprintln!("Error while reading config:\n\n{}", err);
+            std::process::exit(1);
+        }
+    }
 }