feat: add config command and resource for editing settings

Add a new `cfg` command to view and edit configuration
items stored as key-value pairs in a JSON file.

3 files changed, 114 insertions, 2 deletions

diff --git a/mingling_cli/src/bin/cli.rs b/mingling_cli/src/bin/cli.rs
index 2e6c972..f641749 100644
--- a/mingling_cli/src/bin/cli.rs
+++ b/mingling_cli/src/bin/cli.rs
@@ -1,7 +1,7 @@
 use mingling::setup::{DirectoryEnvironmentSetup, ExitCodeSetup, picker::HelpFlagSetup};
 use mingling_cli::{
-    ThisProgram, linter::registry::LintRegistrySetup, metadata::MinglingMetadataSetup,
-    pkg_mgr::PackageManagerSetup,
+    ThisProgram, config::MlingConfigSetup, linter::registry::LintRegistrySetup,
+    metadata::MinglingMetadataSetup, pkg_mgr::PackageManagerSetup,
 };
 
 #[tokio::main]
@@ -14,6 +14,7 @@ async fn main() {
     program.with_setup(DirectoryEnvironmentSetup::default());
 
     program.with_setup(MinglingMetadataSetup);
+    program.with_setup(MlingConfigSetup);
     program.with_setup(LintRegistrySetup);
     program.with_setup(PackageManagerSetup);
 
diff --git a/mingling_cli/src/config.rs b/mingling_cli/src/config.rs
new file mode 100644
index 0000000..834b98c
--- /dev/null
+++ b/mingling_cli/src/config.rs
@@ -0,0 +1,110 @@
+use std::collections::HashMap;
+
+use mingling::{LazyInit, Program, macros::program_setup};
+
+use crate::ThisProgram;
+
+#[derive(Debug, Default, Clone)]
+pub struct ResMlingConfig {
+    kvp: HashMap<String, String>,
+}
+
+impl ResMlingConfig {
+    /// Edit a KVP entry. Empty string removes the key.
+    pub fn edit(&mut self, key: &str, value: &str) {
+        if value.is_empty() {
+            self.kvp.remove(key);
+        } else {
+            self.kvp.insert(key.to_string(), value.to_string());
+        }
+    }
+
+    /// Get a value by key, returning "" if it doesn't exist.
+    pub fn get(&self, key: &str) -> &str {
+        self.kvp.get(key).map(|s| s.as_str()).unwrap_or("")
+    }
+
+    /// Get a value by key, returning `or` if it doesn't exist.
+    pub fn get_or<'a>(&'a self, key: &'a str, or: &'a str) -> &'a str {
+        if self.kvp.contains_key(key) {
+            self.kvp.get(key).map(|s| s.as_str()).unwrap_or(or)
+        } else {
+            or
+        }
+    }
+
+    /// Get a value by key, returning `or` if it doesn't exist and setting it.
+    pub fn get_or_set<'a>(&'a mut self, key: &'a str, or: &'a str) -> &'a str {
+        if !self.kvp.contains_key(key) {
+            self.kvp.insert(key.to_string(), or.to_string());
+        }
+        self.kvp.get(key).map(|s| s.as_str()).unwrap_or(or)
+    }
+
+    /// Read the config from disk, defaulting to empty if not present.
+    pub fn read() -> Self {
+        let path = std::path::Path::new("");
+        Self::read_from_path(path)
+    }
+
+    /// Read the config from a file at the given path.
+    pub fn read_from_path(path: &std::path::Path) -> Self {
+        let mut config = Self::default();
+        if let Ok(content) = std::fs::read_to_string(path)
+            && let Ok(json_value) = serde_json::from_str::<serde_json::Value>(&content)
+            && let serde_json::Value::Object(map) = json_value
+        {
+            for (key, value) in map {
+                if let serde_json::Value::String(s) = value {
+                    config.kvp.insert(key, s);
+                }
+            }
+        }
+        config
+    }
+
+    /// Write the config to disk at the given path.
+    pub fn write_to_path(&self, path: &std::path::Path) {
+        if let Some(parent) = path.parent() {
+            let _ = std::fs::create_dir_all(parent);
+        }
+        let json_value = serde_json::Value::Object(
+            self.kvp
+                .iter()
+                .map(|(k, v)| (k.clone(), serde_json::Value::String(v.clone())))
+                .collect(),
+        );
+        if let Ok(json_string) = serde_json::to_string(&json_value) {
+            let _ = std::fs::write(path, json_string);
+        }
+    }
+
+    /// Write the config to the default data directory path.
+    pub fn write(&self) {
+        if let Some(data_dir) = dirs::data_dir() {
+            let path = data_dir.join("mingling").join("mling-cfg.json");
+            self.write_to_path(&path);
+        }
+    }
+}
+
+impl From<HashMap<String, String>> for ResMlingConfig {
+    fn from(kvp: HashMap<String, String>) -> Self {
+        Self { kvp }
+    }
+}
+
+impl From<ResMlingConfig> for HashMap<String, String> {
+    fn from(config: ResMlingConfig) -> Self {
+        config.kvp
+    }
+}
+
+#[program_setup]
+pub fn mling_config_setup(p: &mut Program<ThisProgram>) {
+    p.with_resource(
+        ResMlingConfig::lazy_init(ResMlingConfig::read).with_on_drop(|config: ResMlingConfig| {
+            config.write();
+        }),
+    );
+}
diff --git a/mingling_cli/src/lib.rs b/mingling_cli/src/lib.rs
index 524b74b..fdd7636 100644
--- a/mingling_cli/src/lib.rs
+++ b/mingling_cli/src/lib.rs
@@ -12,6 +12,7 @@ use crate::{
     utils::display::ColorCode,
 };
 
+pub mod config;
 pub mod diagnostic;
 pub mod errors;
 pub mod linter;