feat(osdb): parse insert and select statements

src/main.rs

@@ -29,28 +29,138 @@ impl std::str::FromStr for MetaCommand {
     }
 }
 
+enum Statement {
+    Insert,
+    Select,
+}
+
+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(),
+            })
+        }
+    }
+}
+
+enum Command {
+    MetaCommand(MetaCommand),
+    Statement(Statement),
+}
+
+enum CommandParseError {
+    MetaCommand(MetaCommandParseError),
+    Statement(StatementParseError),
+}
+
+impl std::fmt::Display for CommandParseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            CommandParseError::MetaCommand(meta_command_parse_error) => {
+                write!(f, "{meta_command_parse_error}")
+            }
+            CommandParseError::Statement(statement_parse_error) => {
+                write!(f, "{statement_parse_error}")
+            }
+        }
+    }
+}
+
+impl From<MetaCommand> for Command {
+    fn from(value: MetaCommand) -> Self {
+        Command::MetaCommand(value)
+    }
+}
+
+impl From<MetaCommandParseError> for CommandParseError {
+    fn from(value: MetaCommandParseError) -> Self {
+        CommandParseError::MetaCommand(value)
+    }
+}
+
+impl From<Statement> for Command {
+    fn from(value: Statement) -> Self {
+        Command::Statement(value)
+    }
+}
+
+impl From<StatementParseError> for CommandParseError {
+    fn from(value: StatementParseError) -> Self {
+        CommandParseError::Statement(value)
+    }
+}
+
+impl std::str::FromStr for Command {
+    type Err = CommandParseError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if s.starts_with(".") {
+            s.parse::<MetaCommand>()
+                .map(|x| x.into())
+                .map_err(|x| x.into())
+        } else {
+            s.parse::<Statement>()
+                .map(|x| x.into())
+                .map_err(|x| x.into())
+        }
+    }
+}
+
 fn main() {
     startup_msg();
     while let Some(input) = read_input() {
         match input.parse() {
             Ok(cmd) => match cmd {
-                MetaCommand::Exit => {
+                Command::MetaCommand(cmd) => match cmd {
-                    println!("Good-bye");
+                    MetaCommand::Exit => {
-                    break;
+                        println!("Good-bye");
-                }
+                        break;
+                    }
+                },
+                Command::Statement(stmt) => execute_statment(stmt),
             },
             Err(err) => eprintln!("{err}"),
         }
     }
 }
 
+fn execute_statment(stmt: Statement) {
+    match stmt {
+        Statement::Insert => println!("insert"),
+        Statement::Select => println!("select"),
+    }
+}
+
 fn startup_msg() {
     let name = env!("CARGO_PKG_NAME");
     let version = env!("CARGO_PKG_VERSION");
     let authors = env!("CARGO_PKG_AUTHORS");
 
     println!("{name} v{version} started.",);
-    println!("Copyright 2024 {authors}. All rights reserved.")
+    println!("Copyright 2025 {authors}. All rights reserved.")
 }
 
 fn read_input() -> Option<String> {