class Observable:
    def __init__(self):
        self.Callbacks = []

    def addHandler(self, h):
        if h not in self.Callbacks:
            self.Callbacks.append(h)

    def notify(self, rows, cols):
        for cbk in self.Callbacks:
            cbk.update_geometry(rows, cols)


class ViewMode(Observable):
    SPACER = 4

    def __init__(self):
        super().__init__()
        self.selector = None
        self._edit = False

    """
    Convert IBM437 character codes 0x00 - 0xFF into Unicode.
    http://svn.openmoko.org/trunk/src/host/qemu-neo1973/phonesim/lib/serial/qatutils.cpp
    """
    cp437ToUnicode = [0x0020, 0x0001, 0x0002, 0x0003, 0x0004, 0x0005, 0x0006, 0x0007,
                      0x0008, 0x0009, 0x000a, 0x000b, 0x000c, 0x000d, 0x000e, 0x000f,
                      0x0010, 0x0011, 0x0012, 0x0013, 0x0014, 0x0015, 0x0016, 0x0017,
                      0x0018, 0x0019, 0x001c, 0x001b, 0x007f, 0x001d, 0x001e, 0x001f,
                      0x0020, 0x0021, 0x0022, 0x0023, 0x0024, 0x0025, 0x0026, 0x0027,
                      0x0028, 0x0029, 0x002a, 0x002b, 0x002c, 0x002d, 0x002e, 0x002f,
                      0x0030, 0x0031, 0x0032, 0x0033, 0x0034, 0x0035, 0x0036, 0x0037,
                      0x0038, 0x0039, 0x003a, 0x003b, 0x003c, 0x003d, 0x003e, 0x003f,
                      0x0040, 0x0041, 0x0042, 0x0043, 0x0044, 0x0045, 0x0046, 0x0047,
                      0x0048, 0x0049, 0x004a, 0x004b, 0x004c, 0x004d, 0x004e, 0x004f,
                      0x0050, 0x0051, 0x0052, 0x0053, 0x0054, 0x0055, 0x0056, 0x0057,
                      0x0058, 0x0059, 0x005a, 0x005b, 0x005c, 0x005d, 0x005e, 0x005f,
                      0x0060, 0x0061, 0x0062, 0x0063, 0x0064, 0x0065, 0x0066, 0x0067,
                      0x0068, 0x0069, 0x006a, 0x006b, 0x006c, 0x006d, 0x006e, 0x006f,
                      0x0070, 0x0071, 0x0072, 0x0073, 0x0074, 0x0075, 0x0076, 0x0077,
                      0x0078, 0x0079, 0x007a, 0x007b, 0x007c, 0x007d, 0x007e, 0x001a,
                      0x00c7, 0x00fc, 0x00e9, 0x00e2, 0x00e4, 0x00e0, 0x00e5, 0x00e7,
                      0x00ea, 0x00eb, 0x00e8, 0x00ef, 0x00ee, 0x00ec, 0x00c4, 0x00c5,
                      0x00c9, 0x00e6, 0x00c6, 0x00f4, 0x00f6, 0x00f2, 0x00fb, 0x00f9,
                      0x00ff, 0x00d6, 0x00dc, 0x00a2, 0x00a3, 0x00a5, 0x20a7, 0x0192,
                      0x00e1, 0x00ed, 0x00f3, 0x00fa, 0x00f1, 0x00d1, 0x00aa, 0x00ba,
                      0x00bf, 0x2310, 0x00ac, 0x00bd, 0x00bc, 0x00a1, 0x00ab, 0x00bb,
                      0x2591, 0x2592, 0x2593, 0x2502, 0x2524, 0x2561, 0x2562, 0x2556,
                      0x2555, 0x2563, 0x2551, 0x2557, 0x255d, 0x255c, 0x255b, 0x2510,
                      0x2514, 0x2534, 0x252c, 0x251c, 0x2500, 0x253c, 0x255e, 0x255f,
                      0x255a, 0x2554, 0x2569, 0x2566, 0x2560, 0x2550, 0x256c, 0x2567,
                      0x2568, 0x2564, 0x2565, 0x2559, 0x2558, 0x2552, 0x2553, 0x256b,
                      0x256a, 0x2518, 0x250c, 0x2588, 0x2584, 0x258c, 0x2590, 0x2580,
                      0x03b1, 0x00df, 0x0393, 0x03c0, 0x03a3, 0x03c3, 0x03bc, 0x03c4,
                      0x03a6, 0x0398, 0x03a9, 0x03b4, 0x221e, 0x03c6, 0x03b5, 0x2229,
                      0x2261, 0x00b1, 0x2265, 0x2264, 0x2320, 0x2321, 0x00f7, 0x2248,
                      0x00b0, 0x2219, 0x00b7, 0x221a, 0x207f, 0x00b2, 0x25a0, 0x00a0]

    def cp437(self, c):
        return chr(self.cp437ToUnicode[c])

    def getPageOffset(self):
        NotImplementedError('method not implemented.')

    # return cols, rows of the view
    def getGeometry(self):
        NotImplementedError('method not implemented.')

    def startSelection(self):
        NotImplementedError('method not implemented.')

    def stopSelection(self):
        NotImplementedError('method not implemented.')

    def draw(self, refresh=False):
        NotImplementedError('method not implemented.')

    # returns x,y cursor position in page
    def getCursorOffsetInPage(self):
        x, y = self.cursor.getPosition()
        return y * self.COLUMNS + x

    def handleKeyPressEvent(self, modifier, key):
        raise Exception("not implemented")

    def handleKeyReleaseEvent(self, modifier, key):
        raise Exception("not implemented")

    # get what's on the screen
    # pageOffset - which page. None - current page
    #
    # return bytearray containing what it is displayed currently on the screen
    def getDisplayablePage(self, pageOffset=None):
        data = self.dataModel.getData()
        dataOffset = self.dataModel.getOffset()
        cols, rows = self.getGeometry()
        if pageOffset:
            return bytearray(data[dataOffset:dataOffset + rows * cols * pageOffset])

        return bytearray(data[dataOffset:dataOffset + rows * cols])

    # moves cursor to offset in page, or moves to page
    def goTo(self, offset):
        # typical goTo

        if self.dataModel.offsetInPage(offset):
            # if in current page, move cursore
            x, y = self.dataModel.getXYInPage(offset)
            self.cursor.moveAbsolute(y, x)
            self.draw(refresh=False)
        else:
            # else, move page
            self.dataModel.goTo(offset)
            self.cursor.moveAbsolute(0, 0)
            self.draw(refresh=True)

        # self.draw(refresh=False)
        if self.widget:
            self.widget.update()

    def isEditable(self):
        return False

    def setEditMode(self, value):
        self._edit = value

    def isInEditMode(self):
        return self._edit

    def getHeaderInfo(self):
        return ''
