roughing out new version

.gitignore

@@ -8,3 +8,6 @@ Cargo.lock
 
 # These are backup files generated by rustfmt
 **/*.rs.bk
+
+# IDEs
+.gitignore

Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "datafusion-sql"
+version = "0.1.0"
+authors = ["Andy Grove <andygrove73@gmail.com>"]
+
+[dependencies]

README.md

@@ -1,2 +1,9 @@
 # datafusion-sql
-DataFusion SQL Parser
+
+DataFusion SQL Parser (v2)
+
+Goals:
+
+- Support for custom SQL dialects, so other projects can implement their own parsers easily
+- Zero-copy of tokens when parsing
+

src/lib.rs

@@ -0,0 +1,151 @@
+
+/* --- TOKENIZER API --- */
+
+enum TokenizerError {
+    WrongToken { expected: SQLToken, actual: SQLToken, line: usize, col: usize },
+    TBD
+}
+
+/// SQL Tokens
+enum SQLToken {
+    Keyword(String),
+    Identifier(String),
+    Eq,
+    Gt,
+    GtEq,
+    Lt,
+    LtEq,
+    LParen,
+    RParen,
+    Comma,
+    Custom(Box<CustomToken>) // extension point for vendor-specific tokens
+}
+
+trait CustomToken {
+    //TODO: ???
+}
+
+trait SQLTokenizer<'a> {
+    // return a reference to the next token without consuming it (look ahead)
+    fn peek_token(&'a mut self) -> Result<Option<&'a SQLToken>, Box<TokenizerError>>;
+    // return a reference to the next token and advance the index
+    fn next_token(&'a mut self) -> Result<Option<&'a SQLToken>, Box<TokenizerError>>;
+}
+
+/* --- PARSER API --- */
+
+/// SQL Operators
+enum SQLOperator {
+    Plus,
+    Minus,
+    Mult,
+    Div,
+    Eq,
+    Gt,
+    GtEq,
+    Lt,
+    LtEq,
+    Custom(Box<CustomOperator>) // extension point for vendor-specific operators
+}
+
+trait CustomOperator {
+    //TODO: ???
+}
+
+/// SQL Expressions
+enum SQLExpr {
+    /// Identifier e.g. table name or column name
+    Identifier(String),
+    /// Literal value
+    Literal(String),
+    /// Binary expression e.g. `1 + 2` or `fname LIKE "A%"`
+    Binary(Box<SQLExpr>, SQLOperator, Box<SQLExpr>),
+    /// Function invocation with function name and list of argument expressions
+    FunctionCall(String, Vec<SQLExpr>),
+    /// Custom expression (vendor-specific)
+    Custom(Box<CustomExpr>)
+}
+
+trait CustomExpr {
+    //TODO: ???
+}
+
+enum ParserError {
+    TBD
+}
+
+trait Parser<'a> {
+    fn parse_expr(&mut self) -> Result<Box<SQLExpr>, Box<ParserError>>;
+    fn parse_expr_list(&mut self) -> Result<Vec<SQLExpr>, Box<ParserError>>;
+    fn parse_identifier(&mut self) -> Result<String, Box<ParserError>>;
+    fn parse_keywords(&mut self, keywords: Vec<&str>) -> Result<bool, Box<ParserError>>;
+}
+
+/* --- KUDU PARSER IMPL --- */
+
+struct KuduParser<'a> {
+    generic_parser: Box<Parser<'a>>
+}
+
+impl<'a> Parser<'a> for KuduParser<'a> {
+
+    fn parse_expr(&mut self) -> Result<Box<SQLExpr>, Box<ParserError>> {
+        self.generic_parser.parse_expr()
+    }
+
+    fn parse_expr_list(&mut self) -> Result<Vec<SQLExpr>, Box<ParserError>> {
+        self.generic_parser.parse_expr_list()
+    }
+
+    fn parse_identifier(&mut self) -> Result<String, Box<ParserError>> {
+        self.generic_parser.parse_identifier()
+    }
+
+    fn parse_keywords(&mut self, keywords: Vec<&str>) -> Result<bool, Box<ParserError>> {
+        self.parse_keywords(keywords)
+    }
+}
+
+/* --- PRATT PARSER IMPL --- */
+
+struct PrattParser<'a> {
+    parser: Box<Parser<'a>>
+}
+
+impl<'a> PrattParser<'a> {
+
+    fn parse_expr(&'a mut self, precedence: u8) -> SQLExpr {
+        unimplemented!()
+    }
+
+//
+//        // Not complete/accurate, but enough to demonstrate the concept that the pratt parser
+//        // does not need knowledge of the specific tokenizer or parser to operate
+//
+//        loop {
+//            match self.tokenizer.peek_token() {
+//                Ok(Some(token)) => {
+//                    let next_precedence = self.parser.get_precedence(&token);
+//                    unimplemented!()
+//                },
+//                _ => {
+//                }
+//            }
+//        }
+//
+//
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+    #[test]
+    fn it_works() {
+        let tokens = vec![
+            SQLToken::Keyword("CREATE".to_string()),
+            SQLToken::Keyword("TABLE".to_string()),
+            SQLToken::Keyword("test".to_string()),
+        ];
+    }
+}