Initial working stage, but not with all tests, because IF NOT EXISTS is not implemented

sql/parser.go

@@ -0,0 +1,208 @@
+package sql
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"slices"
+)
+
+type Parser struct {
+	s    *Lexer
+	last struct {
+		pos Position
+		tok Token
+		lit string
+	}
+}
+
+func NewParser(r io.Reader) *Parser {
+	return &Parser{s: NewLexer(r)}
+}
+
+func (p *Parser) Parse() (*CreateTableStatement, error) {
+	tok, ok := p.expectOne(CREATE, EOF)
+	if !ok {
+		return nil, p.unexpectedToken()
+	} else if tok == EOF {
+		return nil, io.EOF
+	}
+
+	if !p.expectNext(TABLE) {
+		return nil, errors.New("Expect TABLE token")
+	}
+
+	if !p.expectNext(IDENT) {
+		return nil, errors.New("Expect IDENT token")
+	}
+
+	stmt := CreateTableStatement{
+		TableName: p.last.lit,
+		Columns:   make([]Column, 0),
+	}
+
+	_, tok, _ = p.scan()
+	if tok != LPAREN {
+		return nil, errors.New("Expect LPAREN token")
+	}
+
+	for {
+		lastTok := p.last.tok
+		_, tok, _ := p.scan()
+
+		switch tok {
+		case IDENT:
+			column, err := p.parseColumn()
+			if err != nil {
+				return nil, err
+			}
+			stmt.Columns = append(stmt.Columns, column)
+
+		case RPAREN:
+			if !p.expectNext(SEMI) {
+				return nil, p.unexpectedToken()
+			}
+			return &stmt, nil
+
+		case SEMI:
+			if lastTok != RPAREN {
+				return nil, p.unexpectedToken()
+			}
+
+			return &stmt, nil
+
+		case FOREIGN:
+			if !p.expectNext(KEY) {
+				return nil, p.unexpectedToken()
+			}
+			if !p.expectNext(LPAREN) {
+				return nil, p.unexpectedToken()
+			}
+
+			if !p.expectNext(IDENT) {
+				return nil, p.unexpectedToken()
+			}
+			columnName := p.last.lit
+
+			if !p.expectNext(RPAREN) {
+				return nil, p.unexpectedToken()
+			}
+
+			if !p.expectNext(REFERENCES) {
+				return nil, p.unexpectedToken()
+			}
+
+			ref, err := p.references()
+			if err != nil {
+				return nil, err
+			}
+
+			column := slices.IndexFunc(stmt.Columns, func(c Column) bool {
+				return c.Name == columnName
+			})
+
+			stmt.Columns[column].Extra = append(stmt.Columns[column].Extra, ref)
+
+		default:
+			return nil, p.unexpectedToken()
+		}
+	}
+}
+
+func (p *Parser) parseColumn() (Column, error) {
+	column := Column{Name: p.last.lit, Extra: make([]string, 0)}
+
+	_, tok, lit := p.scan()
+	switch tok {
+	case TEXT:
+		fallthrough
+	case INTEGER:
+		column.Type = lit
+	default:
+		return Column{}, p.unexpectedToken()
+	}
+
+	for {
+		_, tok, lit := p.scan()
+		switch tok {
+		case COMMA:
+			fallthrough
+		case RPAREN:
+			return column, nil
+
+		case PRIMARY:
+			fallthrough
+		case NOT:
+			if _, ok := p.expectOne(NULL, KEY); !ok {
+				return Column{}, p.unexpectedToken()
+			}
+			column.Extra = append(column.Extra, fmt.Sprintf("%v_%v", lit, p.last.lit))
+
+		case REFERENCES:
+			ref, err := p.references()
+			if err != nil {
+				return Column{}, err
+			}
+			column.Extra = append(column.Extra, ref)
+
+		default:
+			return Column{}, p.unexpectedToken()
+		}
+	}
+}
+
+func (p *Parser) unexpectedToken() error {
+	return fmt.Errorf("Encountered unexpected token: %v lit: '%v' on pos: %v", p.last.tok, p.last.lit, p.last.pos)
+}
+
+func (p *Parser) references() (string, error) {
+	if !p.expectNext(IDENT) {
+		return "", p.unexpectedToken()
+	}
+	referenceTableName := p.last.lit
+
+	if !p.expectNext(LPAREN) {
+		return "", p.unexpectedToken()
+	}
+
+	if !p.expectNext(IDENT) {
+		return "", p.unexpectedToken()
+	}
+
+	referenceColumnName := p.last.lit
+
+	if !p.expectNext(RPAREN) {
+		return "", p.unexpectedToken()
+	}
+
+	return fmt.Sprintf("ref %v.%v", referenceTableName, referenceColumnName), nil
+}
+
+func (p *Parser) expectNext(token Token) bool {
+	_, tok, _ := p.scan()
+	return tok == token
+}
+
+func (p *Parser) expectOne(token ...Token) (Token, bool) {
+	_, tok, _ := p.scan()
+	ok := slices.ContainsFunc(token, func(t Token) bool {
+		return tok == t
+	})
+	return tok, ok
+}
+
+func (p *Parser) scan() (Position, Token, string) {
+	pos, tok, lit := p.s.Lex()
+	// fmt.Printf("Scanning next Token: %v | pos: %v | lit: %v\n", tok, pos, lit)
+
+	p.last = struct {
+		pos Position
+		tok Token
+		lit string
+	}{
+		pos,
+		tok,
+		lit,
+	}
+	return pos, tok, lit
+}