Organize code, begin database implementation

src/database.rs

@@ -0,0 +1,52 @@
+use crate::Word;
+
+use derive_more::From;
+use std::path::PathBuf;
+use rusqlite::{Connection, Result, params};
+
+pub struct Database {
+    conn: Connection,
+}
+
+#[derive(From, Debug)]
+pub enum DatabaseCreationError {
+    RusqliteError(rusqlite::Error),
+    IoError(std::io::Error),
+}
+
+impl Database {
+    pub fn new(
+        testing: bool,
+    ) -> Result<Self, DatabaseCreationError> {
+        let conn = if testing {
+            Connection::open_in_memory()
+        } else {
+            let path = PathBuf::from("shiritori.db");
+            //fs::create_dir_all(path.parent().unwrap())?;
+            Connection::open(path)
+        }?;
+        conn.execute(
+            "CREATE TABLE IF NOT EXISTS word (
+                id        INTEGER PRIMARY KEY,
+                word      TEXT, reading   TEXT,
+                timestamp DATETIME DEFAULT CURRENT_TIMESTAMP,
+            )",
+            params![],
+        )?;
+        Ok(Self { conn })
+    }
+
+    pub fn load_words_before(&self, before_id: i64) -> Result<Vec<Word>> {
+        self.conn
+            .prepare("SELECT id, word, reading, timestamp FROM word WHERE id < ? DESC LIMIT 10")?
+            .query_map(params![before_id], |row| {
+                Ok(Word {
+                    id: row.get(0)?,
+                    word: row.get(1)?,
+                    reading: row.get(2)?,
+                    timestamp: row.get(3)?,
+                })
+            })?
+            .collect::<Result<Vec<Word>>>()
+    }
+}