fix: IntervalExpression supports complex expressions

- fixes #2172

Signed-off-by: Andreas Reichel <andreas@manticore-projects.com>

Author: manticore-projects

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -5926,15 +5926,25 @@ JsonAggregateFunction JsonAggregateFunction() : {
 }
 
 IntervalExpression IntervalExpression() : {
-    IntervalExpression interval;
+    IntervalExpression interval = new IntervalExpression();
     Token token = null;
     Expression expr = null;
     boolean signed = false;
 }
 {
 
-{ interval = new IntervalExpression(); }
-    <K_INTERVAL> ["-" {signed=true;}] (token=<S_LONG> | token=<S_DOUBLE> | token=<S_CHAR_LITERAL> | LOOKAHEAD(JdbcParameter()) expr = JdbcParameter() | expr = JdbcNamedParameter() | LOOKAHEAD(Function()) expr = Function() | expr = Column())
+    <K_INTERVAL>
+    (
+
+        LOOKAHEAD(3) (
+            [ "-" {signed=true;}]
+            (token=<S_LONG> | token=<S_DOUBLE>)
+        )
+        |
+        LOOKAHEAD(2) token=<S_CHAR_LITERAL>
+        |
+        expr = Expression()
+    )
     {
         if (expr != null) {
             if (signed) expr = new SignedExpression('-', expr);

src/test/java/net/sf/jsqlparser/expression/IntervalExpressionTest.java

@@ -0,0 +1,18 @@
+package net.sf.jsqlparser.expression;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.test.TestUtils;
+import org.junit.jupiter.api.Test;
+
+
+class IntervalExpressionTest {
+
+    @Test
+    void testExtractExpressionIssue2172() throws JSQLParserException {
+        String sqlStr = "select INTERVAL Extract( DAY from Now()) - 1 DAY";
+        TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+
+        sqlStr = "SELECT UNIX_TIMESTAMP(date_sub(date_sub(date_format(now(),'%y-%m-%d'),interval extract(day from now())-1 day),interval 1 month))*1000";
+        TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+    }
+}