How do I switch the IF...ELSE..END <pre>literal expression</pre> to tie into the <b>CTE</b>

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SQL-Server-2008R2

Need to change and include the undernoted IF...ELSE...END Literal expression in a CTE- Common table expression.

IF @CINCIDENT <>'ALL'
            BEGIN
              IF @CINCIDENT = 'OPENED'
                  SET @sql = @sql + ' AND A.COMP_DATE+P.PROD_SERV_TAT >= GETDATE()'
              ELSE IF @CINCIDENT = 'CLOSED'
                  SET @sql = @sql + ' AND A.COMP_DATE+P.PROD_SERV_TAT <  GETDATE()
                                      AND A.RESOLUTION_STAT_FRONT NOT IN ("BAD","UNHAPPY","UNSATISFACTORY")'
              ELSE IF @CINCIDENT = 'UNRESOLVED'
                  SET @sql = @sql + ' AND A.COMP_DATE+P.PROD_SERV_TAT <  GETDATE()
                                    AND A.RESOLUTION_STAT_FRONT     IN ("BAD","UNHAPPY","UNSATISFACTORY")'
             END

CTE -Common Table Expression

;with cte as
(	
		SELECT a.Brn_name AS BRNNAME,A.PTICK_CODE AS TICKET,
		       A.LNAME    AS LNAME   ,A.FNAME      AS FNAME ,
		       A.EMPNO    AS EMPNO  ,A.COMP_TYPE  AS COMP_TYPE,     
		                                b.Attribs AS ATTRIB1  , c.Attribs AS ATTRIB2,
                                        d.Attribs AS ATTRIB3  , e.Attribs AS ATTRIB4
			FROM Response A
			JOIN @REQUEST B ON a.RESPONSE1 = B.Response
			JOIN @REQUEST C ON a.RESPONSE2 = C.Response
			JOIN @REQUEST D ON a.RESPONSE3 = D.Response
			JOIN @REQUEST E ON a.RESPONSE4 = E.Response
	    WHERE A.COMP_DATE BETWEEN @CFROM AND @CTO

         .................(CASE THEN END) STATEMENT..........

)

How do I switch from the IF..ELSE..END

literal expression

to tie into the CTE expression to complete the statement


Thanks

What I have tried:

On going system developmental challenge.

Checked the Internet to no avail