import System.Environment
import System.IO

template = "global _start\n\nSECTION .data\n\nSECTION .bss\ntape resb 255\nbuf resb 1\n\nSECTION .text\n_start:"
left_arrow = "\n\tsub rax, 1\n\tand rax, 0x00000000000000FF"
right_arrow = "\n\tadd rax, 1\n\tand rax, 0x00000000000000FF"
add_bf = "\n\tmov bl, [tape+rax]\n\tadd bl, 1\n\tmov [tape+rax], bl"
sub_bf = "\n\tmov bl, [tape+rax]\n\tsub bl, 1\n\tmov [tape+rax], bl"
dot = "\n\tpush rax\n\tpush qword [tape+rax]\n\tmov rax, 1\n\tmov rdi, 1,\n\tmov rsi, rsp\n\tmov rdx, 1\n\tsyscall\n\tpop rax\n\tpop rax"
comma = "\n\tpush rax\n\tmov rax, 0\n\tmov rdi, 0\n\tmov rsi, buf\n\tmov rdx, 1\n\tsyscall\n\tpop rax\n\tmov rbx, [buf]\n\tmov [tape+rax], bl"
end = "\n\n\n\tmov rdi, [tape+rax]\n\tmov rax, 60\n\tsyscall"

opbrack = ":\n\tcmp byte [tape+rax], 0\n\tje close_"
closbrack = ":\n\tcmp byte [tape+rax], 0\n\tjne open_"

append :: [Int] -> Int -> [Int]
append stack val = stack ++ [val]

parse_other :: Char -> String
parse_other char
    | char == '>' = right_arrow 
    | char == '<' = left_arrow 
    | char == '+' = add_bf   
    | char == '-' = sub_bf 
    | char == '.' = dot      
    | char == ',' = comma
    | otherwise   = ""   

parse_bracket :: Char -> Int -> String
parse_bracket char index
    | char == '[' = "\nopen_" ++ show index ++ opbrack ++ show index
    | char == ']' = "\nclose_" ++ show index ++ closbrack ++ show index
    | otherwise = "" -- never

parse :: String -> Int -> [Int] -> String -- the stack contains positions
parse file index brackstack
    | index == (length file) = ""
    | file!!index == '[' = parse_bracket (file!!index) index ++ (parse file (index+1) (append brackstack index))
    | file!!index == ']' = parse_bracket (file!!index) (last brackstack) ++ (parse file (index+1) (init brackstack))
    | otherwise = (parse_other $ file!!index) ++ parse file (index+1) brackstack

main :: IO()
main = do
    -- let file = "/home/coderlol/code/bfhaskell/test/test.bf"
    args <- getArgs
    print("Compiling " ++ (args!!0) ++ "...")
    content <- readFile(args!!0)
    let stuff =  template ++  (parse content 0 []) ++ end
    writeFile "./bf.asm" stuff