Have a config file for gng_db

gng-build/src/main.rs

@@ -41,14 +41,8 @@ struct Args {
     db_dir: PathBuf,
 
     /// the repository configuration directory
-    #[clap(
-        long,
-        parse(from_os_str),
-        env = "GNG_REPO_CONFIG_DIR",
-        value_name = "DIR",
-        default_value = "/etc/gng/repositories"
-    )]
-    repository_config_dir: PathBuf,
+    #[clap(long, parse(from_os_str), env = "GNG_CONFIG_FILE", value_name = "FILE")]
+    config_file: Option<PathBuf>,
 
     /// the repository to use
     #[clap(long, value_name = "REPO")]
@@ -110,10 +104,9 @@ fn main() -> Result<()> {
         .wrap_err("Failed to get current work directory.")?
         .join(args.pkgsrc_dir);
 
-    let repo_db = gng_db::RepositoryDb::open(&args.repository_config_dir).wrap_err(format!(
-        "Failed to read repositories in {}.",
-        &args.repository_config_dir.display()
-    ))?;
+    let config = gng_db::Config::new(&args.config_file)?;
+
+    let repo_db = config.repository_db()?;
 
     let repo = match &args.repository {
         Some(rin) => repo_db.resolve_repository(rin),

gng_db/src/config.rs

@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (C) 2020 Tobias Hunger <tobias.hunger@gmail.com>
+
+//! A object representing a `Repository`
+
+use crate::{Error, Result};
+
+// ----------------------------------------------------------------------
+// - Constants:
+// ----------------------------------------------------------------------
+
+const REPOSITORY_DIR_KEY: &str = "repository_dir";
+const REMOTES_DIR_KEY: &str = "remotes_dir";
+const LOCALS_DIR_KEY: &str = "locals_dir";
+const PACKET_DB_DIR_KEY: &str = "packet_db_dir";
+
+// ----------------------------------------------------------------------
+// - Helpers:
+// ----------------------------------------------------------------------
+
+fn env_path(env_var: &str, default_prefix: &str, fallback: &str) -> std::path::PathBuf {
+    std::env::var(env_var).map_or_else(
+        |_| {
+            std::env::var("HOME").map_or_else(
+                |_| std::path::PathBuf::from(fallback),
+                |p| std::path::PathBuf::from(p).join(default_prefix),
+            )
+        },
+        std::path::PathBuf::from,
+    )
+}
+
+fn config_path() -> std::path::PathBuf {
+    env_path("XDG_CONFIG_HOME", ".config", "/etc")
+}
+
+fn cache_path() -> std::path::PathBuf {
+    env_path("XDG_CACHE_HOME", ".cache", "/var/cache")
+}
+
+fn data_path() -> std::path::PathBuf {
+    env_path("XDG_DATA_HOME", ".local/share", "/var/lib")
+}
+
+// Fill in default config file path if possible
+fn default_config_file_path(
+    config_file: &Option<std::path::PathBuf>,
+) -> Option<std::path::PathBuf> {
+    if config_file.is_some() {
+        config_file.clone()
+    } else {
+        let config_file_path = config_path().join("gng/config");
+        if config_file_path.exists() {
+            Some(config_file_path)
+        } else {
+            None
+        }
+    }
+}
+
+fn create_config_file_parser(
+    config_file: &Option<std::path::PathBuf>,
+) -> Result<justconfig::Config> {
+    let mut conf = justconfig::Config::default();
+
+    // Open the configuration file
+    if let Some(config_file) = &config_file {
+        let file = std::fs::File::open(config_file)?;
+        conf.add_source(
+            justconfig::sources::text::ConfigText::new(
+                file,
+                config_file.to_string_lossy().as_ref(),
+            )
+            .map_err(|e| Error::Config(e.to_string()))?,
+        );
+    };
+
+    // Allow some environment variables to override configuration values read
+    // from the configuration file.
+    let config_env = justconfig::sources::env::Env::new(&[
+        (
+            justconfig::ConfPath::from(&[REPOSITORY_DIR_KEY]),
+            std::ffi::OsStr::new("GNG_REPOSITORY_DIR"),
+        ),
+        (
+            justconfig::ConfPath::from(&[REMOTES_DIR_KEY]),
+            std::ffi::OsStr::new("GNG_REMOTES_DIR"),
+        ),
+        (
+            justconfig::ConfPath::from(&[LOCALS_DIR_KEY]),
+            std::ffi::OsStr::new("GNG_LOCALS_DIR"),
+        ),
+        (
+            justconfig::ConfPath::from(&[PACKET_DB_DIR_KEY]),
+            std::ffi::OsStr::new("GNG_PACKET_DB_DIR"),
+        ),
+    ]);
+    conf.add_source(config_env);
+
+    // Defaults:
+    let mut defaults = justconfig::sources::defaults::Defaults::default();
+    defaults.set(
+        conf.root().push_all(&[REPOSITORY_DIR_KEY]),
+        config_path()
+            .join("gng/repositories")
+            .to_string_lossy()
+            .as_ref(),
+        "default",
+    );
+    defaults.set(
+        conf.root().push_all(&[REMOTES_DIR_KEY]),
+        cache_path().join("gng/remotes").to_string_lossy().as_ref(),
+        "default",
+    );
+    defaults.set(
+        conf.root().push_all(&[LOCALS_DIR_KEY]),
+        data_path().join("gng/locals").to_string_lossy().as_ref(),
+        "default",
+    );
+    defaults.set(
+        conf.root().push_all(&[PACKET_DB_DIR_KEY]),
+        cache_path().join("gng/packets").to_string_lossy().as_ref(),
+        "default",
+    );
+    conf.add_source(defaults);
+
+    Ok(conf)
+}
+
+// ----------------------------------------------------------------------
+// - Config:
+// ----------------------------------------------------------------------
+
+/// A Configuration object that can be read from a configuration file.
+#[derive(Debug)]
+pub struct Config {
+    /// The directory holding repository definition files
+    pub repository_dir: std::path::PathBuf,
+    /// The directory holding cached data from remote repositories
+    pub remotes_dir: std::path::PathBuf,
+    /// The directory containing all data from local repositories
+    pub locals_dir: std::path::PathBuf,
+    /// The directory holding the packet DB
+    pub packet_db_directory: std::path::PathBuf,
+}
+
+impl Config {
+    /// Parse a config file and create a `Config` object from it.
+    ///
+    /// # Errors
+    /// May return an `Error::Config` if opening the `config_file` or parsing the necessary values fails.
+    #[tracing::instrument(level = "debug")]
+    pub fn new(config_file: &Option<std::path::PathBuf>) -> Result<Self> {
+        use justconfig::item::ValueExtractor;
+
+        // Fill in default config file
+        let config_file = default_config_file_path(config_file);
+
+        let conf = create_config_file_parser(&config_file)?;
+
+        Ok(Self {
+            repository_dir: conf
+                .get(conf.root().push(REPOSITORY_DIR_KEY))
+                .value()
+                .map_err(|e| Error::Config(e.to_string()))?,
+            remotes_dir: conf
+                .get(conf.root().push(REMOTES_DIR_KEY))
+                .value()
+                .map_err(|e| Error::Config(e.to_string()))?,
+            locals_dir: conf
+                .get(conf.root().push(LOCALS_DIR_KEY))
+                .value()
+                .map_err(|e| Error::Config(e.to_string()))?,
+            packet_db_directory: conf
+                .get(conf.root().push(PACKET_DB_DIR_KEY))
+                .value()
+                .map_err(|e| Error::Config(e.to_string()))?,
+        })
+    }
+
+    /// Open the `RepositoryDB` pointed to by this `Config`
+    ///
+    /// # Errors
+    /// May return a `Error::Repository` if opening the Repository DB failed.
+    #[tracing::instrument(level = "debug")]
+    pub fn repository_db(&self) -> Result<crate::repository_db::RepositoryDb> {
+        crate::repository_db::RepositoryDb::open(&self.repository_dir)
+    }
+}

gng_db/src/lib.rs

@@ -24,6 +24,10 @@
 /// Repository related Errors
 #[derive(thiserror::Error, Debug)]
 pub enum Error {
+    /// A generic `Error` about the `RepositoryDb`.
+    #[error("Configuration error: {}", .0)]
+    Config(String),
+
     /// A generic `Error` about the `RepositoryDb`.
     #[error("General repository DB error: {}", .0)]
     Db(String),
@@ -52,6 +56,7 @@ pub type Result<T> = std::result::Result<T, Error>;
 // - Modules:
 // ----------------------------------------------------------------------
 
+pub mod config;
 pub mod packet_db;
 pub mod repository_db;
 
@@ -61,6 +66,8 @@ pub mod repository_db;
 
 pub use uuid::Uuid; // Reexport Uuid from uuid crate!
 
+pub use config::Config;
+// FIXME: Are the following needed?
 pub use packet_db::PacketDb;
 pub use repository_db::RepositoryDb;