Use SQLite to store counter

2 files changed, 188 insertions, 9 deletions

diff --git a/src/main/rust/store/mod.rs b/src/main/rust/store/mod.rs
index 42f1809..7c7d9ce 100644
--- a/src/main/rust/store/mod.rs
+++ b/src/main/rust/store/mod.rs
@@ -1,11 +1,23 @@
-pub mod sqlite;
+mod sqlite;
 
-use miette::Result;
+use std::num::TryFromIntError;
+
+use ::sqlite::Error as SQLiteLibraryError;
+use miette::{Diagnostic, Result};
+use thiserror::Error;
 
 pub enum Context {
     SQLite(sqlite::SQLite),
 }
 
+#[derive(Debug, Diagnostic, Error)]
+pub enum ContextError {
+    #[error("SQLite error")]
+    SQLiteError(#[from] SQLiteLibraryError),
+    #[error("Int conversion error")]
+    ConversionError(#[from] TryFromIntError),
+}
+
 impl Default for Context {
     fn default() -> Self {
         Context::SQLite(sqlite::SQLite::default())
@@ -13,7 +25,23 @@ impl Default for Context {
 }
 
 pub trait Store {
-    fn init(&mut self) -> Result<()>;
+    fn init(&mut self) -> Result<(), ContextError>;
+    fn get_counter(&self) -> Result<u8, ContextError>;
+    fn set_counter(&mut self, new_count: u8) -> Result<u8, ContextError>;
+}
+
+impl Context {
+    pub fn unwrap_store(&mut self) -> &mut impl Store {
+        match self {
+            Context::SQLite(store) => store,
+        }
+    }
+
+    pub fn get_store(&self) -> &impl Store {
+        match self {
+            Context::SQLite(store) => store,
+        }
+    }
 }
 
 #[cfg(test)]
diff --git a/src/main/rust/store/sqlite.rs b/src/main/rust/store/sqlite.rs
index 734c635..6033494 100644
--- a/src/main/rust/store/sqlite.rs
+++ b/src/main/rust/store/sqlite.rs
@@ -1,5 +1,5 @@
-use crate::store::Store;
-use miette::{IntoDiagnostic, Result};
+use crate::store::{ContextError, Store};
+use miette::Result;
 use sqlite::Connection;
 
 pub struct SQLite {
@@ -7,6 +7,49 @@ pub struct SQLite {
     connection: Option<Connection>,
 }
 
+impl SQLite {
+    /// Wrap connection in a Result to make it easier to unwrap later
+    fn get_connection(&self) -> Result<&Connection, sqlite::Error> {
+        match &self.connection {
+            Some(conn) => Ok(conn),
+            None => Err(sqlite::Error {
+                code: None,
+                message: Some("Uninitialized".into()),
+            }),
+        }
+    }
+
+    fn create_table(&self) -> Result<(), sqlite::Error> {
+        let conn = self.get_connection()?;
+        let mut statement = conn.prepare("CREATE TABLE RATAT ( COUNTER SMALLINT )")?;
+        statement.next()?;
+        Ok(())
+    }
+
+    fn insert_counter(&self, counter: i64) -> Result<(), sqlite::Error> {
+        let conn = self.get_connection()?;
+        let mut statement = conn.prepare("INSERT INTO RATAT ( COUNTER ) VALUES ( :counter )")?;
+        statement.bind((":counter", counter))?;
+        statement.next()?;
+        Ok(())
+    }
+
+    fn select_counter(&self) -> Result<i64, sqlite::Error> {
+        let conn = self.get_connection()?;
+        let mut statement = conn.prepare("SELECT COUNTER FROM RATAT")?;
+        statement.next()?;
+        statement.read("COUNTER")
+    }
+
+    fn update_counter(&self, counter: i64) -> Result<(), sqlite::Error> {
+        let conn = self.get_connection()?;
+        let mut statement = conn.prepare("UPDATE RATAT SET COUNTER = :counter")?;
+        statement.bind((":counter", counter))?;
+        statement.next()?;
+        Ok(())
+    }
+}
+
 impl Default for SQLite {
     fn default() -> Self {
         SQLite {
@@ -17,19 +60,47 @@ impl Default for SQLite {
 }
 
 impl Store for SQLite {
-    fn init(&mut self) -> Result<()> {
+    /// Init SQLite for counting. Creates `RATAT` table with single row, with
+    /// counter set to `0`
+    fn init(&mut self) -> Result<(), ContextError> {
         let conn_path = self.location.clone();
-        self.connection = sqlite::open(conn_path).into_diagnostic().ok();
+        let conn = sqlite::open(conn_path)?;
+        self.connection = Option::Some(conn);
+
+        self.create_table()?;
+        self.insert_counter(0)?;
+
         Ok(())
     }
+
+    /// Selects counter from `RATAT` table. Since sqlite doesn't scrutinize the
+    /// value and we have a more restricted datatype (i64 -> u8), we use
+    /// `try_from` which may produce an error result.
+    fn get_counter(&self) -> Result<u8, ContextError> {
+        let result = self.select_counter()?;
+
+        let count = u8::try_from(result)?;
+        Ok(count)
+    }
+
+    /// Updates row with counter value on `RATAT` table
+    fn set_counter(&mut self, new_count: u8) -> Result<u8, ContextError> {
+        self.update_counter(i64::from(new_count))?;
+
+        Ok(new_count)
+    }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    // Practically, the `Store` trait is what we interface with externally, and
+    // provides the more general `Result` interface we want to work with so
+    // that's what we test here
+
     #[test]
-    fn sqlite_default() {
+    fn default() {
         let context = SQLite::default();
 
         assert_eq!(context.location, ":memory:");
@@ -37,7 +108,7 @@ mod tests {
     }
 
     #[test]
-    fn sqlite_init() {
+    fn init() {
         let mut context = SQLite::default();
 
         let res = context.init();
@@ -45,4 +116,84 @@ mod tests {
         assert!(res.is_ok());
         assert!(context.connection.is_some());
     }
+
+    #[test]
+    fn get_counter() {
+        let mut context = SQLite::default();
+        assert!(context.init().is_ok());
+
+        let res = context.get_counter();
+
+        assert!(res.is_ok());
+        assert_eq!(res.unwrap(), 0);
+    }
+
+    #[test]
+    fn get_counter_error() {
+        let context = SQLite::default();
+        // don't initialize
+
+        let res = context.get_counter();
+
+        assert!(res.is_err());
+    }
+
+    #[test]
+    fn get_counter_outside_range() {
+        let mut context = SQLite::default();
+        assert!(context.init().is_ok());
+
+        let new_value = -1;
+        if let Some(conn) = &context.connection {
+            let mut statement = conn.prepare("UPDATE RATAT SET COUNTER = ?").unwrap();
+            statement.bind((1, new_value)).unwrap();
+            statement.next().unwrap();
+        }
+        let res = context.get_counter();
+
+        assert!(res.is_err());
+    }
+
+    #[test]
+    fn set_counter() {
+        let mut context = SQLite::default();
+        assert!(context.init().is_ok());
+
+        let expected = 240;
+        let res = context.set_counter(expected);
+
+        assert!(res.is_ok());
+        assert_eq!(res.unwrap(), expected);
+    }
+
+    #[test]
+    fn set_counter_error() {
+        let mut context = SQLite::default();
+        // don't initialize
+
+        let res = context.set_counter(1);
+
+        assert!(res.is_err());
+    }
+
+    #[test]
+    fn set_and_get() {
+        let mut context = SQLite::default();
+        assert!(context.init().is_ok());
+
+        let count_0 = context.get_counter().unwrap();
+
+        assert_eq!(count_0, 0);
+
+        let new_num = 244;
+        let res = context.set_counter(new_num);
+
+        assert!(res.is_ok());
+        assert_eq!(res.unwrap(), new_num);
+
+        let count_1 = context.get_counter().unwrap();
+
+        assert_eq!(count_1, new_num);
+        assert_ne!(count_0, count_1);
+    }
 }