Replace lexer, add parser

pkg/search/ast.go

@@ -0,0 +1,53 @@
+package search
+
+import "strings"
+
+type Expression interface {
+	String() string
+}
+
+type PrefixExpression struct {
+	Operator TokenType
+	Right    Expression
+}
+
+func (pe *PrefixExpression) expressionNode() {}
+func (pe *PrefixExpression) String() string {
+	b := strings.Builder{}
+	b.WriteString("(")
+	b.WriteString(pe.Operator.String())
+	b.WriteString(" ")
+	b.WriteString(pe.Right.String())
+	b.WriteString(")")
+
+	return b.String()
+}
+
+type InfixExpression struct {
+	Operator TokenType
+	Left     Expression
+	Right    Expression
+}
+
+func (ie *InfixExpression) expressionNode() {}
+func (ie *InfixExpression) String() string {
+	b := strings.Builder{}
+	b.WriteString("(")
+	b.WriteString(ie.Left.String())
+	b.WriteString(" ")
+	b.WriteString(ie.Operator.String())
+	b.WriteString(" ")
+	b.WriteString(ie.Right.String())
+	b.WriteString(")")
+
+	return b.String()
+}
+
+type StringLiteral struct {
+	Value string
+}
+
+func (sl *StringLiteral) expressionNode() {}
+func (sl *StringLiteral) String() string {
+	return sl.Value
+}