refactor: pull things into own files, have a library

src/statements.rs

@@ -0,0 +1,45 @@
+pub enum Statement {
+    Insert,
+    Select,
+}
+
+pub enum StatementParseError {
+    Unrecognized { stmt: String },
+}
+
+impl std::fmt::Display for StatementParseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            StatementParseError::Unrecognized { stmt } => {
+                write!(f, "unrecognized statement {stmt:?}")
+            }
+        }
+    }
+}
+
+impl std::str::FromStr for Statement {
+    type Err = StatementParseError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let s = s.trim();
+        let lower = s.to_lowercase();
+        if lower.starts_with("insert") {
+            Ok(Statement::Insert)
+        } else if lower.starts_with("select") {
+            Ok(Statement::Select)
+        } else {
+            Err(StatementParseError::Unrecognized {
+                stmt: s.to_string(),
+            })
+        }
+    }
+}
+
+impl Statement {
+    pub fn execute(&self) {
+        match self {
+            Statement::Insert => println!("insert"),
+            Statement::Select => println!("select"),
+        }
+    }
+}