import sys,time    
import parallel

SLEEP_TIME = 0
NUM_CHARS = 8

MAX_LENGTH = 2048
MAX_SCROLL_LENGTH = MAX_LENGTH / NUM_CHARS - NUM_CHARS

CHAR_END = 0
CHAR_BLANK = 0x80
ERR_TOO_LONG = 1

#constants for the individual segments

A = 1
B = 2
C = 4
D = 8
E = 16
F = 32
G = 64
H = 256
J = 512
K = 1024
L = 2048
M = 4096
N = 8192
P = 16384

#array of seg patterns for all ascii characters

charcodes = (
    0,              #NUL
    0,              #SOH
    0,              #STX
    0,              #ETX
    0,              #EOT
    0,              #ENQ
    0,              #ACK
    0,              #BEL
    0,              #BS
    0,              #HT
    0,              #LF
    0,              #VT
    0,              #FF
    0,              #CR
    0,              #SO
    0,              #SI
    0,              #DLE
    0,              #DC1
    0,              #DC2
    0,              #DC3
    0,              #DC4
    0,              #NAK
    0,              #SYN
    0,              #ETB
    0,              #CAN
    0,              #EM
    0,              #SUB
    0,              #ESC
    0,              #FS
    0,              #GS
    0,              #RS
    0,              #US
    0,              #SPACE
    0,              #!
    B|F,            #"
    A|B|C|D|E|F|G|H|J|M, ##
    A|F|H|G|C|D|J|M,#$
    C|F|K|N,        #%
    A|D|E|F|G|H|J|M,#&
    J,              #'
    A|F|E|D,        #(
    A|B|C|D,        #)
    G|H|J|K|L|M|P,  #*
    H|G|J|M,        #+
    N,              #,
    H|G,            #-
    0,              #.
    K|N,            #/
    A|B|C|D|E|F|K|N,#0
    B|C,            #1
    A|B|G|H|E|D,    #2
    A|B|H|G|C|D,    #3
    F|G|H|B|C,      #4
    A|P|G|C|D,      #5
    A|F|E|D|C|G|H,  #6
    A|B|C,          #7
    A|B|C|D|E|F|G|H,#8
    A|B|C|D|F|G|H,  #9
    0,              #:
    0,              #;
    K|L,            #<
    H|G|D,          #=
    P|N,            #>
    A|B|G|M,        #?
    F|A|B|C|D|N|L,  #@
    E|F|A|B|G|H|C,  #A
    A|B|C|D|J|M|G,  #B
    A|F|E|D,        #C
    A|B|C|D|J|M,    #D
    A|F|E|D|H,      #E (could also add segment G)
    A|F|E|H,        #F
    A|F|E|D|C|G,    #G
    F|E|B|C|G|H,    #H
    A|D|J|M,        #I
    B|C|D|E,        #J
    F|H|E|K|L,      #K
    F|E|D,          #L
    E|F|P|K|B|C,    #M
    E|F|P|L|B|C,    #N
    A|B|C|D|E|F,    #O
    A|B|G|H|F|E,    #P
    A|B|C|D|E|F|L,  #Q
    L|G|B|A|F|E|H,  #R
    A|F|H|G|C|D,    #S
    A|J|M,          #T
    F|E|D|C|B,      #U
    F|E|N|K,        #V
    F|E|N|L|C|B,    #W
    P|N|K|L,        #X
    P|K|M,          #Y
    A|K|N|D,        #Z
    A|F|E|D,        #[
    P|L,            #\
    A|B|C|D,        #]
    0,              #^
    D,              #_
    P,              #`
    A|B|C|D|N|G,    #a
    F|E|D|C|G|H,    #b
    G|H|E|D,        #c
    B|C|D|E|G|H,    #d
    D|E|F|A|K|H,    #e
    F|E|H|A,        #f
    F|A|B|G|H|C|D,  #g
    F|E|G|H|C,      #h
    M,              #i
    B|C|D|E,        #j
    F|H|E|K|N,      #k
    J|M,            #l
    E|H|M|G|C,      #m
    E|H|G|C,        #n
    E|H|G|C|D,      #o
    E|F|A|B|G|H,    #p
    B|C|A|G|H|F,    #q
    E|H,            #r
    A|F|H|G|C|D,    #s
    F|E|D|H,        #t
    E|D|C,          #u
    L|C,            #v
    E|D|M|C,        #w
    P|K|N|L,        #x
    F|H|G|B|C|D,    #y
    A|K|N|D,        #z
    A|P|H|N|D,      #{
    J|M,            #|
    A|K|G|L|D,      #}
    F|K|P,          #~
    0               #DEL
)

class Sign:
    def __init__(self, port = 0):
        """just initialize some things"""
        self.p = parallel.Parallel(port)
    
    def write(self, n):
        """write a byte to the sign"""
        time.sleep(SLEEP_TIME)
        self.p.setDataStrobe(0)
        time.sleep(SLEEP_TIME)
        self.p.setData(n)
        time.sleep(SLEEP_TIME)
        self.p.setDataStrobe(1)
        time.sleep(SLEEP_TIME)
        self.p.setInitOut(0)
        time.sleep(SLEEP_TIME)
        self.p.setInitOut(1)

    def advance(self):
        """advance() twiddles the Init line of the parallel
        port to increment the address that the next write()
        will write to."""
        time.sleep(SLEEP_TIME)
        self.p.setInitOut(0);
        time.sleep(SLEEP_TIME)
        self.p.setInitOut(1);

    def reset(self):
        """reset() twiddles the Select In line to reset the
        address on the sign to zero. Reset before starting a
        write and after finishing."""
        time.sleep(SLEEP_TIME)
        self.p.setSelect(0)
        time.sleep(SLEEP_TIME)
        self.p.setSelect(1)

    def open(self):
        """open() is somewhat wrongly named, but not terribly.
        it sets all the control lines high (off), then disables
        the external clocks and enables writes to the sign."""
        self.p.setSelect(1)
        self.p.setInitOut(1)
        self.p.setDataStrobe(1)
        self.p.setAutoFeed(0)

    def close(self):
        """close() is the opposite of open(). It enables the
        internal clocks and starts the sign running normally."""
        time.sleep(SLEEP_TIME)
        self.p.setAutoFeed(1)

    def writechar(self, c):
        """writechar() looks up a character (c) in the lookup
        table and writes the corresponding segment patterns two
        the sign."""
        code = charcodes[ord(c)]
        self.write(code & 0xff | CHAR_BLANK)
        self.write((code & 0xff00) >> 8 | CHAR_BLANK)
     
    def writestr(self, str):
        """writestr() writes a string to the sign."""
        if len(str) > MAX_LENGTH:
            print "Maximum length is %i characters; that was %i." % (MAX_LENGTH, len(str))
            sys.exit(ERR_TOO_LONG)
        for char in str:
            self.writechar(char)
        if len(str) <= MAX_LENGTH - NUM_CHARS:
            if len(str) % NUM_CHARS:
                for i in range(0, NUM_CHARS - len(str) % NUM_CHARS):
                    #print "**len(str) is %i, pad by 1**" % len(str)
                    self.write(CHAR_BLANK)
                    self.write(CHAR_BLANK)
            for i in range(0, 16):
                self.write(0)

    def scrollify(self, str):
        """scrollify() converts str to a string that can be written
        to the display that will appear to scroll."""
        
        if len(str) <= NUM_CHARS: return str
        ret = ''
        str = ' ' * NUM_CHARS + str
        for i in range(0, len(str)):
            sub = str[i:i+NUM_CHARS]
            if len(sub) < NUM_CHARS:
                sub += " " * (NUM_CHARS - len(sub) % NUM_CHARS)
            ret += sub

        return ret

    def msg(self, str, scroll):
        """msg() is the only method you actually have to call.
        It enables writes, resets the sign, writes a string, resets
        again, and disables writes. Set scroll to true to make the
        message scroll."""
        
        if (scroll):
            if len(str) > MAX_SCROLL_LENGTH:
                print "Maximum length is %i characters; that was %i." % (MAX_SCROLL_LENGTH, len(str))
                sys.exit(ERR_TOO_LONG)
            str = self.scrollify(str)
        self.open()
        self.reset()
        self.writestr(str)
        self.reset()
        self.close()

s = Sign()

if len(sys.argv) > 1:
    s.msg(sys.argv[1], 1)