Behavioral to Structural Conversion Problems VHDL

I designed a primality testing for Rabin Miller algorithm in behavioral type. I used functions to create my modules. Unfortunately, when I tried to synthesize it by my Altera Kit via Quartus, I realized that function are not synthesize. Here I will write my whole program, and I really need you help to give me at least some hints to change it to structural as it is my senior design project. Here is my program:

 library ieee;
 use ieee.std_logic_1164.all;
 use ieee.numeric_std.all;

 entity PrimeTest is
 port( N: in integer;
 Test1 : out std_logic);
 end PrimeTest;  

  Architecture Behavior1 of PrimeTest is


  function integer_binary (b1:std_logic_vector(31 downto 0)) return integer is
  variable a: integer:=0;
  variable i: integer;
   begin
    i:=0;

     while (i<32) loop
if b1(i) = '1' then
a:=a+2**i; 
end if;
i:=i+1;   
end loop;
     return a;
    end integer_binary;

       function integer_binary1 (b1:std_logic) return integer is
        variable a: integer;

       begin
if b1 = '1' then
a:= 1; 
else
  a:=0;
end if;
     return a;
     end integer_binary1;

     function binary1 (int1:integer) return std_logic_vector is
     variable int2: integer;
     variable a:std_logic_vector(31 downto 0);
  variable i: integer;

   begin
   int2:=int1;
  i:=0;
 while (i<32) loop    
  if (int2 mod 2 = 0) then
    a(i):='0';
  else
    a(i):='1';
  end if;
  i:=i+1;
    int2:=int2/2;
  end loop;
  return a;
  end binary1;

 function mul_mod (x1,y1,m1: std_logic_vector (31 downto 0)) return std_logic_vector is
variable p1: std_logic_vector (31 downto 0);
variable k: integer;
variable n: integer;
variable i: integer;
 variable j: std_logic_vector (31 downto 0);
 begin
n:=32;
i:=31;
p1:="00000000000000000000000000000000";
while(i>=0) loop

  p1:=binary1((integer_binary(p1))*2);

j:=binary1((integer_binary(y1))*((integer_binary1 (x1(i)))));

p1:=binary1((integer_binary(p1))+((integer_binary (j))));

if (p1 >= m1) then
  p1:=binary1(((integer_binary(p1))-(integer_binary (m1))));
end if;

    if (p1 >= m1) then
  p1:=binary1(((integer_binary(p1))-(integer_binary (m1))));
end if;
i:=i-1; 

end loop;
return p1;
end mul_mod;



 FUNCTION modexp3 (exp_m,exp_n: integer; 
                      exp_e: std_logic_vector(31 downto 0)) return integer is 
                 variable s:integer; 
                  variable result: integer:=1;
                        begin
    S := exp_m;

   L1: for I in 0 to 31 loop

    I2:    if (exp_e(I) = '1') then
        result := integer_binary(mul_mod(binary1(result),binary1(s),binary1(exp_n)));
       S := integer_binary(mul_mod(binary1(s),binary1(s),binary1(exp_n)));
   else
       S := integer_binary(mul_mod(binary1(s),binary1(s),binary1(exp_n)));
   end if I2;

    end loop L1 ;
    return result; 
  end modexp3;


 FUNCTION park1 (in_seed1,max1: integer) return integer is 
                 variable hi:integer;
                 variable lo:integer; 
                  variable out_seed:integer;
                  variable test:integer;
                  variable random1: integer;
                   variable rejected: integer;
                   variable a:integer:=16807;
                  variable m:integer:=2147483647;
                  variable q: integer:=127773;
                  variable r: integer:=2836;
                  variable seed:integer;

                        begin
                          seed:=in_seed1;

              for en in 0 to 1 loop
                if (en = 0) then
                  hi:=in_seed1 / q;
                 else
                  hi:=out_seed / q;
               end if;

lo:=in_seed1 mod q;
test:=((a*lo) - (r*hi));

if test > 0 then
Out_seed:= test;

else
Out_seed:= test + m;

    end if;
  end loop;
 random1:=out_seed mod max1;
 if random1 = 0 then
   seed:=(seed-1)**2;
   random1:= park1(seed,max1);
 end if;
    return random1; 
  end park1;

-- Primality Test Function
Function IS_Prime(number: integer) return STD_Logic is
Variable d: integer;
Variable d_binary: std_logic_vector(31 downto 0);
Variable s_1: integer :=0;
Variable iteration: integer :=1;
Variable x: integer;
Variable a: integer;
variable two:std_logic_vector(31 downto 0):="00000000000000000000000000000010";
Variable fake: integer;


Begin
d:= number -1; 
if ( number < 2) then
Return '0';
end if;  
if ( number = 2) then
Return '1';
end if;
if ( number /= 2 and number mod 2 = 0) then
 return '0';
end if;
while ( d mod 2 = 0 ) loop 
d:=d/2;
s_1:=s_1+1;
end loop;
d_binary:=binary1(d);
ii_loop: for ii in 0 to iteration-1 loop
a:=park1((ii+(s_1*100000))+number,(number-2));
x:=modexp3 (a,number,d_binary);
z4: if ((x /= 1) and (x /= number -1)) then 
 R_LOOP:         for r in 0 to s_1-1 loop
        fake:=0;
        x:=modexp3(x,number,two);
            z0: if (x = number -1) then
                fake:=1;
                 exit R_LOOP when fake = 1;
            end if z0;
            z1: if (x = 1) then 
                    return '0';
                end if z1;
    end loop R_LOOP;

        z2: if (fake/=1) then
            return '0'; 
        end if z2;

end if z4;
end loop ii_loop;
return '1';
End IS_Prime;
Begin

Test1 <= IS_Prime(N);


end Behavior1;

I am new to VHDL and this is really confusing me where I have no progress in my project. Please, I need that program to be in structural type (port mapping).

You asked for some hints, so I'll just write some things that come to mind from looking at your code, hoping it will be helpful.

There is no problem in using functions; they are a good way to organize your design. They are synthesizable, as long as the statements you use in the function body are synthesizable as well.
Don't reinvent the wheel. Most of the functions you wrote are already predefined in the standard libraries. Do some research before implementing, and try to think whether it is a common subprogram, one that would be useful to most designers. If this is the case, there is probably a ready solution, especially if it involves type conversions or math.
As Brian Drummond said, try to avoid while loops because they are harder for the compiler to guess the total number of iterations. for loops with constant limits are easier on the synthesizer. And forget about nested loops with variable ranges.
Jerry Coffin is also right when he says that there may be some confusion between how you implement an algorithm in hardware vs. in software. Most of the times, drawing a hardware diagram before writing any code helps sort things out. Many times, it at least reveals that the designer does not have a very good idea of what it takes to implement the algorithm in hardware.
You want to make the transition from software to hardware. A big part of it is to decide what you need to do instantly (within a single clock cycle), and what you want to do sequentially (spread over several clock cycles). So, suppose you have some behavioral (non-synthesizable) code that calculates something using a loop, and you want to make this calculation in hardware.
- If you need to calculate it in a syngle clock cycle, the compiler will have replicate the hardware for all loop iterations, which might be huge.
- If you can spread the calculation over several clock cycles, your best bet is to design a finite state machine (FSM) for this calculation. Again, draw a diagram before writing the code, this will help a lot in your case.

Hope this helps point you in the right direction.