refactor: extract helpers, constants, and idiomatic patterns

crates/dkdc-db-cli/src/cli.rs

@@ -1,6 +1,7 @@
 use clap::{Parser, Subcommand};
 
 pub const TMUX_SESSION: &str = "dkdc-db";
+const DEFAULT_LOG_LINES: usize = 50;
 
 #[derive(Parser)]
 #[command(name = "db", about = "dkdc-db: HTAP database")]
@@ -14,11 +15,11 @@ pub enum Commands {
     /// Start the database server (in tmux)
     Serve {
         /// Host to bind to
-        #[arg(long, default_value = "127.0.0.1")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_HOST)]
         host: String,
 
         /// Port to bind to
-        #[arg(long, default_value_t = 4200)]
+        #[arg(long, default_value_t = dkdc_db_core::DEFAULT_PORT)]
         port: u16,
 
         /// Run in foreground (skip tmux)
@@ -30,15 +31,15 @@ pub enum Commands {
     /// Show database server status
     Status {
         /// Port to check
-        #[arg(long, default_value_t = 4200)]
+        #[arg(long, default_value_t = dkdc_db_core::DEFAULT_PORT)]
         port: u16,
     },
     /// Attach to database server tmux session
     Attach,
     /// Show recent logs from tmux session
     Logs {
         /// Number of lines to show
-        #[arg(short, long, default_value_t = 50)]
+        #[arg(short, long, default_value_t = DEFAULT_LOG_LINES)]
         lines: usize,
     },
     /// Generate a starter db.toml in the current directory
@@ -55,7 +56,7 @@ pub enum Commands {
         #[arg()]
         name: String,
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
     },
     /// Drop a database
@@ -64,13 +65,13 @@ pub enum Commands {
         #[arg()]
         name: String,
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
     },
     /// Interactive SQL REPL
     Repl {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
         /// Initial database to use
         #[arg(long)]
@@ -79,7 +80,7 @@ pub enum Commands {
     /// Execute a read query and print results
     Query {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
         /// Database for OLTP query (omit for global analytical)
         #[arg(long)]
@@ -90,7 +91,7 @@ pub enum Commands {
     /// Execute a write statement
     Execute {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
         /// Target database (required)
         #[arg(long)]
@@ -101,7 +102,7 @@ pub enum Commands {
     /// List tables in a database
     Tables {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
         /// Database name (required)
         #[arg(long)]
@@ -110,7 +111,7 @@ pub enum Commands {
     /// List databases
     List {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
     },
 }

crates/dkdc-db-cli/src/lib.rs

@@ -54,12 +54,16 @@ async fn async_main() -> anyhow::Result<()> {
                 // Apply server config (CLI flags override config file)
                 let (effective_host, effective_port) = match &config {
                     Some(c) => {
-                        let h = if host != "127.0.0.1" {
+                        let h = if host != dkdc_db_core::DEFAULT_HOST {
                             host.clone()
                         } else {
                             c.server.host.clone()
                         };
-                        let p = if port != 4200 { port } else { c.server.port };
+                        let p = if port != dkdc_db_core::DEFAULT_PORT {
+                            port
+                        } else {
+                            c.server.port
+                        };
                         (h, p)
                     }
                     None => (host.clone(), port),

crates/dkdc-db-client/src/cli.rs

@@ -12,7 +12,7 @@ pub enum Commands {
     /// Interactive SQL REPL
     Repl {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
         /// Initial database to use
         #[arg(long)]
@@ -21,7 +21,7 @@ pub enum Commands {
     /// Execute a read query and print results
     Query {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
         /// Database for OLTP query (omit for global analytical)
         #[arg(long)]
@@ -32,7 +32,7 @@ pub enum Commands {
     /// Execute a write statement
     Execute {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
         /// Target database (required)
         #[arg(long)]
@@ -43,7 +43,7 @@ pub enum Commands {
     /// List tables in a database
     Tables {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
         /// Database name (required)
         #[arg(long)]
@@ -52,7 +52,7 @@ pub enum Commands {
     /// List databases
     List {
         /// Server URL
-        #[arg(long, default_value = "http://127.0.0.1:4200")]
+        #[arg(long, default_value = dkdc_db_core::DEFAULT_SERVER_URL)]
         url: String,
     },
 }

crates/dkdc-db-client/src/lib.rs

@@ -1,7 +1,7 @@
 #[cfg(feature = "cli")]
 pub mod repl;
 
-use serde::{Deserialize, Serialize};
+use serde::{Deserialize, Serialize, de::DeserializeOwned};
 
 #[derive(thiserror::Error, Debug)]
 pub enum Error {
@@ -74,12 +74,7 @@ impl DbClient {
             .send()
             .await?;
 
-        if resp.status().is_success() {
-            Ok(())
-        } else {
-            let body: ErrorResponse = resp.json().await?;
-            Err(Error::Server(body.error))
-        }
+        self.handle_response_unit(resp).await
     }
 
     /// Drop a database.
@@ -90,12 +85,7 @@ impl DbClient {
             .send()
             .await?;
 
-        if resp.status().is_success() {
-            Ok(())
-        } else {
-            let body: ErrorResponse = resp.json().await?;
-            Err(Error::Server(body.error))
-        }
+        self.handle_response_unit(resp).await
     }
 
     /// List all databases.
@@ -106,12 +96,7 @@ impl DbClient {
             .send()
             .await?;
 
-        if resp.status().is_success() {
-            Ok(resp.json().await?)
-        } else {
-            let body: ErrorResponse = resp.json().await?;
-            Err(Error::Server(body.error))
-        }
+        self.handle_response(resp).await
     }
 
     /// Execute a write statement against a specific database.
@@ -125,13 +110,8 @@ impl DbClient {
             .send()
             .await?;
 
-        if resp.status().is_success() {
-            let body: ExecuteResponse = resp.json().await?;
-            Ok(body.affected)
-        } else {
-            let body: ErrorResponse = resp.json().await?;
-            Err(Error::Server(body.error))
-        }
+        let body: ExecuteResponse = self.handle_response(resp).await?;
+        Ok(body.affected)
     }
 
     /// Analytical query through DataFusion. Supports cross-db joins.
@@ -145,12 +125,7 @@ impl DbClient {
             .send()
             .await?;
 
-        if resp.status().is_success() {
-            Ok(resp.json().await?)
-        } else {
-            let body: ErrorResponse = resp.json().await?;
-            Err(Error::Server(body.error))
-        }
+        self.handle_response(resp).await
     }
 
     /// OLTP fast-path read against a specific database.
@@ -164,12 +139,7 @@ impl DbClient {
             .send()
             .await?;
 
-        if resp.status().is_success() {
-            Ok(resp.json().await?)
-        } else {
-            let body: ErrorResponse = resp.json().await?;
-            Err(Error::Server(body.error))
-        }
+        self.handle_response(resp).await
     }
 
     /// List tables in a specific database.
@@ -180,12 +150,7 @@ impl DbClient {
             .send()
             .await?;
 
-        if resp.status().is_success() {
-            Ok(resp.json().await?)
-        } else {
-            let body: ErrorResponse = resp.json().await?;
-            Err(Error::Server(body.error))
-        }
+        self.handle_response(resp).await
     }
 
     /// Get table schema for a specific database.
@@ -196,12 +161,7 @@ impl DbClient {
             .send()
             .await?;
 
-        if resp.status().is_success() {
-            Ok(resp.json().await?)
-        } else {
-            let body: ErrorResponse = resp.json().await?;
-            Err(Error::Server(body.error))
-        }
+        self.handle_response(resp).await
     }
 
     /// Health check.
@@ -213,4 +173,26 @@ impl DbClient {
             .await?;
         Ok(resp.status().is_success())
     }
+
+    // -- internal --
+
+    /// Deserialize a successful JSON response or extract the server error.
+    async fn handle_response<T: DeserializeOwned>(&self, resp: reqwest::Response) -> Result<T> {
+        if resp.status().is_success() {
+            Ok(resp.json().await?)
+        } else {
+            let body: ErrorResponse = resp.json().await?;
+            Err(Error::Server(body.error))
+        }
+    }
+
+    /// Check for success on responses with no meaningful body.
+    async fn handle_response_unit(&self, resp: reqwest::Response) -> Result<()> {
+        if resp.status().is_success() {
+            Ok(())
+        } else {
+            let body: ErrorResponse = resp.json().await?;
+            Err(Error::Server(body.error))
+        }
+    }
 }

crates/dkdc-db-core/benches/benchmark.rs

@@ -66,8 +66,7 @@ async fn setup_multi_table(size: usize) -> DbManager {
 
     // Insert regions
     mgr.execute("bench", "BEGIN").await.unwrap();
-    for i in 0..10 {
-        let name = REGIONS[i];
+    for (i, name) in REGIONS.iter().enumerate() {
         mgr.execute(
             "bench",
             &format!("INSERT INTO regions VALUES ({i}, '{name}', 'US')"),

crates/dkdc-db-core/src/catalog.rs

@@ -11,6 +11,8 @@ use crate::error::Result;
 use crate::provider::SqliteTableProvider;
 use crate::schema;
 
+const DEFAULT_SCHEMA: &str = "public";
+
 /// One catalog per database. Contains a single "public" schema.
 pub struct SqliteCatalogProvider {
     schema: Arc<SqliteSchemaProvider>,
@@ -40,12 +42,12 @@ impl CatalogProvider for SqliteCatalogProvider {
     }
 
     fn schema_names(&self) -> Vec<String> {
-        vec!["public".to_string()]
+        vec![DEFAULT_SCHEMA.to_string()]
     }
 
     fn schema(&self, name: &str) -> Option<Arc<dyn SchemaProvider>> {
         match name {
-            "public" => Some(self.schema.clone()),
+            DEFAULT_SCHEMA => Some(self.schema.clone()),
             _ => None,
         }
     }

crates/dkdc-db-core/src/db.rs

@@ -7,6 +7,10 @@ use crate::router;
 use crate::schema;
 use crate::write::WriteEngine;
 
+const IN_MEMORY_PATH: &str = ":memory:";
+const WAL_MODE_PRAGMA: &str = "journal_mode";
+const WAL_MODE_VALUE: &str = "'wal'";
+
 /// Try to extract a table name from a simple SELECT query for PRAGMA fallback.
 /// Handles `SELECT ... FROM table_name` patterns.
 fn extract_table_name(sql: &str) -> Option<String> {
@@ -21,6 +25,12 @@ fn extract_table_name(sql: &str) -> Option<String> {
     if name.is_empty() { None } else { Some(name) }
 }
 
+/// Enable WAL mode on a connection for concurrent read+write.
+async fn enable_wal(conn: &turso::Connection) -> Result<()> {
+    conn.pragma_update(WAL_MODE_PRAGMA, WAL_MODE_VALUE).await?;
+    Ok(())
+}
+
 pub struct DkdcDb {
     write: WriteEngine,
     db: turso::Database,
@@ -40,9 +50,7 @@ impl DkdcDb {
             .await?;
 
         let write_conn = db.connect()?;
-
-        // Enable WAL mode for concurrent read+write
-        write_conn.pragma_update("journal_mode", "'wal'").await?;
+        enable_wal(&write_conn).await?;
 
         let write = WriteEngine::new(write_conn);
 
@@ -52,11 +60,9 @@ impl DkdcDb {
     /// Open an in-memory database (for testing).
     /// Turso connections from the same Database share the same in-memory data.
     pub async fn open_in_memory() -> Result<Self> {
-        let db = turso::Builder::new_local(":memory:").build().await?;
+        let db = turso::Builder::new_local(IN_MEMORY_PATH).build().await?;
         let write_conn = db.connect()?;
-
-        // Enable WAL mode
-        write_conn.pragma_update("journal_mode", "'wal'").await?;
+        enable_wal(&write_conn).await?;
 
         let write = WriteEngine::new(write_conn);