#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Needs freetype-py>=1.0

# For more info see:
# http://dbader.org/blog/monochrome-font-rendering-with-freetype-and-python

# The MIT License (MIT)
#
# Copyright (c) 2013 Daniel Bader (http://dbader.org)
# Copyright (c) 2019 Max Regan (http://git.maxregan.me)
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

import freetype


class Bitmap(object):
    """
    A 2D bitmap image represented as a list of byte values. Each byte indicates the state
    of a single pixel in the bitmap. A value of 0 indicates that the pixel is `off`
    and any other value indicates that it is `on`.
    """
    def __init__(self, width, height, pixels=None):
        self.width = width
        self.height = height
        self.pixels = pixels or bytearray(width * height)

    def __repr__(self):
        """Return a string representation of the bitmap's pixels."""
        rows = ''
        for y in range(self.height):
            for x in range(self.width):
                rows += '#' if self.pixels[y * self.width + x] else ' '
            rows += '\n'
        return rows

    def bitblt(self, src, x, y):
        """Copy all pixels from `src` into this bitmap"""
        srcpixel = 0
        dstpixel = y * self.width + x
        row_offset = self.width - src.width

        for sy in range(src.height):
            for sx in range(src.width):
                # Perform an OR operation on the destination pixel and the source pixel
                # because glyph bitmaps may overlap if character kerning is applied, e.g.
                # in the string "AVA", the "A" and "V" glyphs must be rendered with
                # overlapping bounding boxes.
                self.pixels[dstpixel] = self.pixels[dstpixel] or src.pixels[srcpixel]
                srcpixel += 1
                dstpixel += 1
            dstpixel += row_offset


class Glyph(object):
    def __init__(self, pixels, width, height, top, left, advance_width):
        self.bitmap = Bitmap(width, height, pixels)

        # The glyph bitmap's top-side bearing, i.e. the vertical distance from the
        # baseline to the bitmap's top-most scanline.
        self.top = top
        self.left = left

        # Ascent and descent determine how many pixels the glyph extends
        # above or below the baseline.
        self.descent = max(0, self.height - self.top)
        self.ascent = max(0, max(self.top, self.height) - self.descent)

        # The advance width determines where to place the next character horizontally,
        # that is, how many pixels we move to the right to draw the next glyph.
        self.advance_width = advance_width

    @property
    def width(self):
        return self.bitmap.width

    @property
    def height(self):
        return self.bitmap.height

    @staticmethod
    def from_glyphslot(slot):
        """Construct and return a Glyph object from a FreeType GlyphSlot."""
        pixels = Glyph.unpack_mono_bitmap(slot.bitmap)
        width, height = slot.bitmap.width, slot.bitmap.rows
        top = slot.bitmap_top
        left = slot.bitmap_left

        # The advance width is given in FreeType's 26.6 fixed point format,
        # which means that the pixel values are multiples of 64.
        assert slot.advance.x % 64 == 0
        advance_width = slot.advance.x // 64

        return Glyph(pixels, width, height, top, left, advance_width)

    @staticmethod
    def unpack_mono_bitmap(bitmap):
        """
        Unpack a freetype FT_LOAD_TARGET_MONO glyph bitmap into a bytearray where each
        pixel is represented by a single byte.
        """
        # Allocate a bytearray of sufficient size to hold the glyph bitmap.
        data = bytearray(bitmap.rows * bitmap.width)

        # Iterate over every byte in the glyph bitmap. Note that we're not
        # iterating over every pixel in the resulting unpacked bitmap --
        # we're iterating over the packed bytes in the input bitmap.
        for y in range(bitmap.rows):
            for byte_index in range(bitmap.pitch):

                # Read the byte that contains the packed pixel data.
                byte_value = bitmap.buffer[y * bitmap.pitch + byte_index]

                # We've processed this many bits (=pixels) so far. This determines
                # where we'll read the next batch of pixels from.
                num_bits_done = byte_index * 8

                # Pre-compute where to write the pixels that we're going
                # to unpack from the current byte in the glyph bitmap.
                rowstart = y * bitmap.width + byte_index * 8

                # Iterate over every bit (=pixel) that's still a part of the
                # output bitmap. Sometimes we're only unpacking a fraction of a byte
                # because glyphs may not always fit on a byte boundary. So we make sure
                # to stop if we unpack past the current row of pixels.
                for bit_index in range(min(8, bitmap.width - num_bits_done)):

                    # Unpack the next pixel from the current glyph byte.
                    bit = byte_value & (1 << (7 - bit_index))

                    # Write the pixel to the output bytearray. We ensure that `off`
                    # pixels have a value of 0 and `on` pixels have a value of 1.
                    data[rowstart + bit_index] = 1 if bit else 0

        return data


class FixedFont(object):
    def __init__(self, filename, width=0, height=0):
        self.face = freetype.Face(filename)
        if not width and not height:
            raise ValueError("Width or height must be set non-zero")
        self.face.set_pixel_sizes(width, height)

        # if not self.face.is_fixed_width:
        #     raise ValueError("Font is not fixed width")

        self.face.load_char('A', freetype.FT_LOAD_RENDER | freetype.FT_LOAD_TARGET_MONO)
        self.advance = self.face.glyph.advance.x // 64

    def glyph_for_character(self, char):
        # Let FreeType load the glyph for the given character and tell it to render
        # a monochromatic bitmap representation.
        self.face.load_char(char, freetype.FT_LOAD_RENDER | freetype.FT_LOAD_TARGET_MONO)
        return Glyph.from_glyphslot(self.face.glyph)

    def render_character(self, char):
        glyph = self.glyph_for_character(char)
        return glyph.bitmap

    def text_dimensions(self, text):
        """Return (width, height, baseline) of `text` rendered in the current font."""
        width = 0
        max_ascent = 0
        max_descent = 0
        previous_char = None

        # For each character in the text string we get the glyph
        # and update the overall dimensions of the resulting bitmap.
        for char in text:
            glyph = self.glyph_for_character(char)
            max_ascent = max(max_ascent, glyph.ascent)
            max_descent = max(max_descent, glyph.descent)

            # With kerning, the advance width may be less than the width of the glyph's bitmap.
            # Make sure we compute the total width so that all of the glyph's pixels
            # fit into the returned dimensions.
            width += self.advance

            previous_char = char

        height = max_ascent + max_descent
        return (width, height, max_descent)

    def render_text(self, text, width=None, height=None, baseline=None):
        """
        Render the given `text` into a Bitmap and return it.

        If `width`, `height`, and `baseline` are not specified they are computed using
        the `text_dimensions' method.
        """
        if None in (width, height, baseline):
            width, height, baseline = self.text_dimensions(text)

        x = 0
        previous_char = None
        outbuffer = Bitmap(width, height)

        for char in text:
            glyph = self.glyph_for_character(char)

            # The vertical drawing position should place the glyph
            # on the baseline as intended.
            y = height - glyph.ascent - baseline

            outbuffer.bitblt(glyph.bitmap, x, y)

            x += glyph.advance_width
            previous_char = char

        return outbuffer

if __name__ == '__main__':
    # Be sure to place 'helvetica.ttf' (or any other ttf / otf font file) in the working directory.
    fnt = FixedFont('/usr/share/fonts/truetype/ubuntu/UbuntuMono-R.ttf', 24)

    print(repr(fnt.render_text('AV Wa')))
