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const std = @import("std");
const tokenizer = @import("tokenizer.zig");
const ParserError = error{
Error,
};
const NodeType = enum {
PROGRAM,
VARIABLE_STATEMENT,
PRINT_STATEMENT,
NUMBER,
IDENTIFIER,
};
pub const Node = union(NodeType) {
PROGRAM: struct {
statements: []*Node,
},
VARIABLE_STATEMENT: struct {
is_declaration: bool,
name: []const u8,
expression: *Node,
},
PRINT_STATEMENT: struct {
expression: *Node,
},
NUMBER: struct {
value: i64,
},
IDENTIFIER: struct {
name: []const u8,
},
};
pub const Parser = struct {
tokens: []tokenizer.Token,
offset: u32,
pub fn init(tokens: []tokenizer.Token) *Parser {
return @constCast(&Parser{
.tokens = tokens,
.offset = 0,
});
}
pub fn parse(parser: *Parser) ParserError!Node {
return parser.parse_program();
}
fn parse_program(_: *Parser) ParserError!Node {
return Node{
.NUMBER = .{ .value = 9 },
};
}
fn parse_identifier(self: *Parser) ParserError!Node {
const token = self.peek_token() orelse return ParserError.Error;
if (token != .IDENTIFIER) return ParserError.Error;
_ = self.consume_token();
return Node{ .IDENTIFIER = .{
.name = token.IDENTIFIER,
} };
}
fn parse_number(self: *Parser) ParserError!Node {
const token = self.peek_token() orelse return ParserError.Error;
if (token != .NUMBER) return ParserError.Error;
_ = self.consume_token();
return Node{ .NUMBER = .{
.value = token.NUMBER,
} };
}
fn parse_print_statement(self: *Parser) ParserError!Node {
// print + ( + statement + ) + ;
var token = self.consume_token() orelse return ParserError.Error;
if (token != .PRINT) return ParserError.Error;
token = self.consume_token() orelse return ParserError.Error;
if (token != .LPAREN) return ParserError.Error;
const expression = try self.parse_expression();
token = self.consume_token() orelse return ParserError.Error;
if (token != .RPAREN) return ParserError.Error;
token = self.consume_token() orelse return ParserError.Error;
if (token != .SEMICOLON) return ParserError.Error;
return Node{
.PRINT_STATEMENT = .{
.expression = @constCast(&expression), //TODO: Warning ptr
},
};
}
fn parse_expression(self: *Parser) ParserError!Node {
const token = self.peek_token() orelse return ParserError.Error;
if (token == .NUMBER) {
return self.parse_number();
} else if (token == .IDENTIFIER) {
return self.parse_identifier();
} else if (token == .PRINT) {
return self.parse_print_statement();
} else {
return ParserError.Error;
}
}
fn consume_token(self: *Parser) ?tokenizer.Token {
if (self.offset >= self.tokens.len) return null;
defer self.offset += 1;
return self.tokens[self.offset];
}
fn peek_token(self: Parser) ?tokenizer.Token {
if (self.offset >= self.tokens.len) return null;
return self.tokens[self.offset];
}
};
test "parse print" {
const tokens: []tokenizer.Token = @constCast(&[_]tokenizer.Token{
tokenizer.Token{ .PRINT = void{} },
tokenizer.Token{ .LPAREN = void{} },
tokenizer.Token{ .NUMBER = 7 },
tokenizer.Token{ .RPAREN = void{} },
tokenizer.Token{ .SEMICOLON = void{} },
});
var parser = Parser.init(tokens);
const print = try parser.parse_print_statement();
//TODO: Warning ptr
try std.testing.expectEqualDeep(Node{ .PRINT_STATEMENT = .{ .expression = @constCast(&Node{ .NUMBER = .{
.value = 7,
} }) } }, print);
}
test "parse identifier" {
const tokens: []tokenizer.Token = @constCast(&[_]tokenizer.Token{
tokenizer.Token{ .IDENTIFIER = @constCast("i") },
});
var parser = Parser.init(tokens);
const ident = try parser.parse_identifier();
try std.testing.expectEqualDeep(Node{ .IDENTIFIER = .{
.name = @constCast("i"),
} }, ident);
}
test "parse number" {
const tokens: []tokenizer.Token = @constCast(&[_]tokenizer.Token{
tokenizer.Token{ .NUMBER = 7 },
});
var parser = Parser.init(tokens);
const number = try parser.parse_number();
try std.testing.expectEqualDeep(Node{ .NUMBER = .{
.value = 7,
} }, number);
}
test "simple e2e" {
const tokens: []tokenizer.Token = @constCast(&[_]tokenizer.Token{
tokenizer.Token{ .LET = void{} },
tokenizer.Token{ .IDENTIFIER = @constCast("i") },
tokenizer.Token{ .EQUALS = void{} },
tokenizer.Token{ .NUMBER = 2 },
tokenizer.Token{ .SEMICOLON = void{} },
});
const ast = try Parser.init(tokens).parse();
try std.testing.expectEqualDeep(Node{ .PROGRAM = .{ .statements = @constCast(&[_]*Node{
@constCast(&Node{ .VARIABLE_STATEMENT = .{ .is_declaration = true, .name = @constCast("i"), .expression = @constCast(&Node{
.NUMBER = .{ .value = 2 },
}) } }),
}) } }, ast);
}
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