VHDL：简单的交通灯管理，编程出错，求救啊啊啊啊啊，错误在最后

LIBRARY IEEE;  
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY traffic_control IS
PORT(  
clk  :IN STD_LOGIC;
c1,c2,c3:OUT STD_LOGIC;
w1,w2,w3:IN STD_LOGIC;
r1,r2 :OUT STD_LOGIC;
y1,y2 :OUT STD_LOGIC;
g1,g2 :OUT STD_LOGIC;  
reset :IN  STD_LOGIC);
END traffic_control;
ARCHITECTURE a OF traffic_control IS  
TYPE STATE_SPACE IS(S0,S1,S2,S3);
SIGNAL state:STATE_SPACE;
BEGIN
PROCESS(clk)
BEGIN
IF reset='1' THEN  
state      
   IF w1='1' THEN   
     state      
   IF w2='1' THEN   
     state       
  IF w3='1' THEN
        state       
IF w2='1' THEN   
      state<=S0;   
      END IF;   
END CASE;   
END IF;
  END PROCESS;  
  c1<='1'  WHEN state=S0 ELSE '0';
  c2<='1'  WHEN state=S1 OR state=S3 ELSE '0';
  c3<='1'  WHEN state=S2 ELSE '0';  
  r1<='1'  WHEN state=S1 OR state=S0  ELSE '0';
  y1<='1'  WHEN state=S3 ELSE '0';
  g1<='1'  WHEN state=S2 ELSE '0';
  r2<='1'  WHEN state=S2 OR state=S3  ELSE '0';
  y2<='1'  WHEN state=S1 ELSE '0';
  g2<='1'  WHEN state=S0 ELSE '0';
  END a;
Error (10500): VHDL syntax error at traffic_control.vhd(15) near text "SIGNAL?";  expecting "begin", or a declaration statement
Error (10500): VHDL syntax error at traffic_control.vhd(17) near text "?";  expecting "begin", or a declaration statement
Error: Quartus II 64-Bit Create Symbol File was unsuccessful. 2 errors, 0 warnings