feat(cli): add toml config

- [x] init migra.toml with serialized default config
	parameters
- [x] read and desirealize config from migra.toml

migra-cli/Cargo.toml

@@ -9,3 +9,5 @@ edition = "2018"
 [dependencies]
 migra-core = { path = '../migra-core' }
 structopt = "0.3.21"
+serde = { version = "1.0", features = ["derive"] }
+toml = "0.5.8"

migra-cli/src/config.rs

@@ -0,0 +1,39 @@
+use serde::{Deserialize, Serialize};
+use std::fs;
+use std::path::Path;
+
+const MIGRA_TOML_FILENAME: &str = "migra.toml";
+
+#[derive(Debug, Serialize, Deserialize)]
+pub(crate) struct Config {
+    directory: String,
+}
+
+impl Default for Config {
+    fn default() -> Config {
+        Config {
+            directory: String::from("database"),
+        }
+    }
+}
+
+impl Config {
+    pub fn read() -> Config {
+        fs::read_to_string(MIGRA_TOML_FILENAME)
+            .ok()
+            .and_then(|content| toml::from_str(&content).ok())
+            .unwrap_or_default()
+    }
+
+    pub fn initialize() -> Result<(), Box<dyn std::error::Error>> {
+        if Path::new(MIGRA_TOML_FILENAME).exists() {
+            return Ok(());
+        }
+
+        let config = Config::default();
+        let content = toml::to_string(&config)?;
+        fs::write(MIGRA_TOML_FILENAME, content)?;
+
+        Ok(())
+    }
+}

migra-cli/src/main.rs

@@ -1,16 +1,23 @@
 #![deny(clippy::all)]
 
+mod config;
 mod opts;
 
+use config::Config;
 use opts::{AppOpt, StructOpt};
 
-fn main() {
+fn main() -> Result<(), Box<dyn std::error::Error>> {
     let opt = AppOpt::from_args();
     dbg!(&opt);
 
+    let config = Config::read();
+    dbg!(&config);
+
     match opt {
         AppOpt::Init => {
-            println!("unimplemented");
+            Config::initialize()?;
         }
     }
+
+    Ok(())
 }