feat: Add support for external JSON config file

Fixes #68

crates/lsp-ai/src/main.rs

@@ -11,7 +11,7 @@ use std::sync::Mutex;
 use std::{
     collections::HashMap,
     fs,
-    path::Path,
+    path::{Path, PathBuf},
     sync::{mpsc, Arc},
     thread,
 };
@@ -68,6 +68,9 @@ struct Args {
     // A dummy argument for now
     #[arg(long, default_value_t = true)]
     stdio: bool,
+    // JSON configuration file location
+    #[arg(long, value_parser = utils::validate_file_exists, required = false)]
+    config: Option<PathBuf>,
 }
 
 fn create_log_file(base_path: &Path) -> anyhow::Result<fs::File> {
@@ -109,6 +112,17 @@ fn init_logger(args: &Args) {
     }
 }
 
+fn load_config(args: &Args, init_args: serde_json::Value) -> anyhow::Result<serde_json::Value> {
+    if let Some(config_path) = &args.config {
+        let config_data = fs::read_to_string(config_path)?;
+        let mut config = serde_json::from_str(&config_data)?;
+        utils::merge_json(&mut config, &init_args);
+        Ok(config)
+    } else {
+        Ok(init_args)
+    }
+}
+
 fn main() -> Result<()> {
     let args = Args::parse();
     init_logger(&args);
@@ -130,7 +144,7 @@ fn main() -> Result<()> {
     })?;
     let initialization_args = connection.initialize(server_capabilities)?;
 
-    if let Err(e) = main_loop(connection, initialization_args) {
+    if let Err(e) = main_loop(connection, load_config(&args, initialization_args)?) {
         error!("{e:?}");
     }
 

crates/lsp-ai/src/utils.rs

@@ -1,6 +1,9 @@
-use anyhow::Context;
+use std::path::PathBuf;
+
+use anyhow::{anyhow, Context};
 use lsp_server::ResponseError;
 use once_cell::sync::Lazy;
+use serde_json::Value;
 use tokio::runtime;
 use tree_sitter::Tree;
 
@@ -93,3 +96,28 @@ pub(crate) fn format_file_chunk(uri: &str, excerpt: &str, root_uri: Option<&str>
 {excerpt}"#,
     )
 }
+
+pub(crate) fn validate_file_exists(path: &str) -> anyhow::Result<PathBuf> {
+    let path = PathBuf::from(path);
+    if path.is_file() {
+        Ok(path)
+    } else {
+        Err(anyhow!("File doesn't exist: {}", path.display()))
+    }
+}
+
+pub(crate) fn merge_json(a: &mut Value, b: &Value) {
+    match (a, b) {
+        (&mut Value::Object(ref mut a), &Value::Object(ref b)) => {
+            for (k, v) in b {
+                merge_json(a.entry(k.clone()).or_insert(Value::Null), v);
+            }
+        }
+        (&mut Value::Array(ref mut a), &Value::Array(ref b)) => {
+            a.extend(b.clone());
+        }
+        (a, b) => {
+            *a = b.clone();
+        }
+    }
+}