Basic .csmrc parsing

Cargo.toml

@@ -7,3 +7,5 @@ edition = "2024"
 clap = { version = "4.5.50", features = ["derive", "wrap_help"] }
 env_logger = "0.11.8"
 log = "0.4.28"
+serde = { version = "1.0.228", features = ["derive"] }
+serde_yaml_ng = "0.10.0"

README.md

@@ -0,0 +1,13 @@
+# csm - Checkmk synthetic monitoring
+
+(Under active development, not yet usable.)
+
+## Configuration: `~/.csmrc`
+
+You can optionally create a file, `~/.csmrc` (`%UserProfile%\.csmrc` on Windows)
+to override certain defaults. This is a YAML file with the following keys
+available:
+
+* `mamba_root_prefix` - A string which sets where the Mamba environment(s) will
+  be created on disk. By default, this is left up to `micromamba` and its
+  default root prefix is used.

src/csmrc.rs

@@ -0,0 +1,37 @@
+/// Module for reading a user's ~/.csmrc, if it exists.
+use crate::util;
+
+use log::debug;
+use serde::Deserialize;
+use std::default::Default;
+use std::io::{Error, ErrorKind};
+use std::path::PathBuf;
+
+#[derive(Debug, Default, Deserialize)]
+pub struct Config {
+    /// Override the $MAMBA_ROOT_PREFIX when shelling out to micromamba.
+    #[serde(default)]
+    #[allow(dead_code)]
+    pub mamba_root_prefix: Option<String>,
+}
+
+impl Config {
+    /// Read the user's ~/.csmrc if it exists, merging with the Default instance for
+    /// Config. Return Err if a config file was found but failed to parse, otherwise
+    /// Ok with the result of merging the config file values with the Default (and
+    /// simply the Default if no config file exists).
+    pub fn from_csmrc() -> Result<Self, std::io::Error> {
+        let Ok(home) = util::homedir() else {
+            return Ok(Self::default());
+        };
+        let csmrc_path = PathBuf::from(home).join(".csmrc");
+        let Ok(csmrc_data) = std::fs::read_to_string(csmrc_path) else {
+            debug!("No .csmrc found, using defaults");
+            return Ok(Config::default());
+        };
+        let config =
+            serde_yaml_ng::from_str(&csmrc_data).map_err(|e| Error::new(ErrorKind::InvalidData, e));
+        debug!("config: {:?}", config);
+        config
+    }
+}

src/env.rs

@@ -1,3 +1,5 @@
+use crate::csmrc::Config;
+
 #[derive(Debug, clap::Subcommand)]
 pub enum Subcommand {
     /// Create an environment
@@ -27,6 +29,7 @@ pub struct CreateArgs {
     name: Option<String>,
 }
 
-pub fn run(subcommand: Subcommand) {
+pub fn run(config: Config, subcommand: Subcommand) {
+    println!("{:?}", config);
     println!("{:?}", subcommand);
 }

src/main.rs

@@ -1,8 +1,10 @@
+mod csmrc;
 mod env;
 mod robot;
+mod util;
 
 use clap::{Parser, Subcommand};
-use log::{LevelFilter, debug};
+use log::{LevelFilter, debug, error};
 use std::fs::File;
 use std::io::Write;
 use std::path::PathBuf;
@@ -29,7 +31,7 @@ enum Command {
     Robot(robot::Subcommand),
 }
 
-fn main() {
+fn main() -> Result<(), std::io::Error> {
     let cli = Cli::parse();
 
     // Set up logging
@@ -41,15 +43,26 @@ fn main() {
     let mut env_logger_builder = env_logger::Builder::new();
     env_logger_builder.filter_level(default_verbosity);
     env_logger_builder.parse_default_env();
+    env_logger_builder.format_timestamp(None);
     env_logger_builder.init();
 
     let _ = create_mambarc();
+    let config = match csmrc::Config::from_csmrc() {
+        Ok(config) => config,
+        Err(err) => {
+            error!("Failed to parse .csmrc: {}", err);
+            panic!("Failed to parse .csmrc as valid YAML");
+        }
+    };
     match cli.command {
-        Command::Env(sub) => env::run(sub),
-        Command::Robot(sub) => robot::run(sub),
+        Command::Env(sub) => env::run(config, sub),
+        Command::Robot(sub) => robot::run(config, sub),
     }
+    Ok(())
 }
 
+/// Create a ~/.mambarc (%UserProfile%\.mambarc on Windows) if it does not
+/// exist.
 fn create_mambarc() -> std::io::Result<()> {
     let mambarc = r#"
 # Show the active environment in the shell prompt
@@ -64,9 +77,7 @@ changeps1: True
 # ssl_verify: mycorpcert.crt
 # ssl_no_revoke: true
 "#;
-    let home = std::env::var("HOME")
-        .or_else(|_| std::env::var("USERPROFILE"))
-        .expect("Cannot determine home directory");
+    let home = util::homedir().expect("Cannot determine home directory");
     let mambarc_path = PathBuf::from(home).join(".mambarc");
     match File::create_new(&mambarc_path) {
         Ok(mut file) => file.write_all(mambarc.trim_start().as_bytes())?,

src/robot.rs

@@ -1,3 +1,5 @@
+use crate::csmrc::Config;
+
 #[derive(Debug, clap::Subcommand)]
 pub enum Subcommand {
     /// Create a Robotmk robot
@@ -13,6 +15,7 @@ pub struct CreateArgs {
     path: String,
 }
 
-pub fn run(subcommand: Subcommand) {
+pub fn run(config: Config, subcommand: Subcommand) {
+    println!("{:?}", config);
     println!("{:?}", subcommand);
 }

src/util.rs

@@ -0,0 +1,5 @@
+use std::env;
+
+pub fn homedir() -> Result<String, env::VarError> {
+    env::var("HOME").or_else(|_| env::var("USERPROFILE"))
+}