From 4c2e14acdcddd2726ef5026b7a2be4b477b6d648 Mon Sep 17 00:00:00 2001
From: Yuriy Dupyn <2153100+omedusyo@users.noreply.github.com>
Date: Mon, 5 Feb 2024 20:31:43 +0100
Subject: [PATCH] Introduce a global database lock (for table creation)

---
 minisql/src/error.rs        |  2 +
 minisql/src/interpreter2.rs | 77 +++++++++++++++++++++++++++++++++----
 2 files changed, 72 insertions(+), 7 deletions(-)

diff --git a/minisql/src/error.rs b/minisql/src/error.rs
index 827de93..db2d416 100644
--- a/minisql/src/error.rs
+++ b/minisql/src/error.rs
@@ -13,6 +13,8 @@ pub enum RuntimeError {
     AttemptToIndexNonIndexableColumn(TableName, ColumnName),
     #[error("table {0} already indexes column {1}")]
     AttemptToIndexAlreadyIndexedColumn(TableName, ColumnName),
+    #[error("File-System Error: {0}")]
+    IoError(std::io::Error),
     #[error("Storage Engine error for table {0}: {1}")]
     StorageEngineError(TableName, storage_engine::error::Error),
     #[error("runtime anyhow error: {0}")]
diff --git a/minisql/src/interpreter2.rs b/minisql/src/interpreter2.rs
index dfcd568..f09c4e8 100644
--- a/minisql/src/interpreter2.rs
+++ b/minisql/src/interpreter2.rs
@@ -7,7 +7,10 @@ use crate::response_writer::{ResponseWriter, CompleteStatus};
 use crate::internals::row::Row;
 
 use bimap::BiMap;
-use std::path::Path;
+use std::path::{Path, PathBuf};
+
+use tokio::sync::RwLock;
+use tokio::fs;
 
 use storage_engine::store::Store;
 use storage_engine::cursor::{ReadCursor, WriteCursor};
@@ -21,6 +24,12 @@ pub struct State {
     tables: Tables,
 }
 
+
+pub struct StateHandler {
+    db_path: PathBuf,
+    state: RwLock<State>,
+}
+
 pub type Tables = Vec<Table>;
 
 #[derive(Debug)]
@@ -166,6 +175,61 @@ impl State {
     }
 }
 
+impl StateHandler {
+    pub async fn new(db_path: PathBuf) -> DbResult<Self> {
+        fs::create_dir(db_path.clone()).await.map_err(|e| RuntimeError::IoError(e))?;
+
+        let state = Self {
+            db_path,
+            state: RwLock::new(State::new()),
+        };
+        Ok(state)
+    }
+
+    pub async fn connect(db_path: PathBuf) -> Self {
+        todo!()
+    }
+
+    pub async fn interpret<Writer: ResponseWriter>(&self, response_writer: &mut Writer, operation: Operation) -> DbResult<()> {
+        use Operation::*;
+
+        match operation {
+            Select(table_position, column_selection, maybe_condition) => {
+                let state = self.state.read().await;
+
+                let table: &Table = state.table_at(table_position);
+                let cursor = table.read().await?;
+
+                response_writer.write_table_header(&table.schema, &column_selection).await.map_err(|e| RuntimeError::AnyhowError(e))?;
+                let count = match maybe_condition {
+                    None => State::select_all_rows(&table, cursor, response_writer, column_selection).await?,
+                    Some(Condition::Eq(eq_column, value)) => State::select_eq(&table, cursor, response_writer, column_selection, eq_column, value).await?
+                };
+                response_writer.write_command_complete(CompleteStatus::Select(count)).await.map_err(|e| RuntimeError::AnyhowError(e))
+            }
+            Insert(table_position, values) => {
+                let state = self.state.read().await;
+                todo!()
+            }
+            Delete(table_position, maybe_condition) => {
+                let state = self.state.read().await;
+
+                todo!()
+            }
+            CreateTable(table_schema) => {
+                let mut state = self.state.write().await;
+                let table = Table::new(table_schema, &self.db_path).await?;
+                state.attach_table(table).await;
+                response_writer.write_command_complete(CompleteStatus::CreateTable).await.map_err(|e| RuntimeError::AnyhowError(e))
+            }
+            CreateIndex(table_position, column) => {
+                let state = self.state.read().await;
+                todo!()
+            }
+        }
+    }
+}
+
 
 
 
@@ -202,22 +266,21 @@ mod tests {
 
     #[tokio::test]
     async fn test_table_creation() {
-        let mut state = State::new();
+        let db_path = Path::new("db-test-0");
+        let state = StateHandler::new(db_path.to_path_buf()).await.unwrap();
+
         let users_schema = users_schema();
         let users = users_schema.table_name().clone();
 
-        let db_path = Path::new("db-test-0");
-        fs::create_dir(db_path).await.unwrap();
-
         let mut response_writer = ResponseWriterStub::new();
 
         state
-            .interpret(db_path, &mut response_writer, Operation::CreateTable(users_schema.clone())).await
+            .interpret(&mut response_writer, Operation::CreateTable(users_schema.clone())).await
             .unwrap();
 
         let users_position: TablePosition = 0;
         state
-            .interpret(db_path, &mut response_writer, Operation::Select(
+            .interpret(&mut response_writer, Operation::Select(
                 users_position,
                 users_schema.all_selection(),
                 None,