#!python3
import freetype
import zlib
import sys
import re
import math
import argparse
from collections import namedtuple

# Originally from https://github.com/vroland/epdiy

parser = argparse.ArgumentParser(description="Generate a header file from a font to be used with epdiy.")
parser.add_argument("name", action="store", help="name of the font.")
parser.add_argument("size", type=int, help="font size to use.")
parser.add_argument("fontstack", action="store", nargs='+', help="list of font files, ordered by descending priority.")
parser.add_argument("--2bit", dest="is2Bit", action="store_true", help="generate 2-bit greyscale bitmap instead of 1-bit black and white.")
parser.add_argument("--additional-intervals", dest="additional_intervals", action="append", help="Additional code point intervals to export as min,max. This argument can be repeated.")
parser.add_argument("--compress", dest="compress", action="store_true", help="Compress glyph bitmaps using DEFLATE with group-based compression.")
parser.add_argument("--force-autohint", dest="force_autohint", action="store_true", help="Force FreeType auto-hinter instead of native font hinting. Improves stem width consistency for fonts with weak or no native TrueType hints.")
args = parser.parse_args()

GlyphProps = namedtuple("GlyphProps", ["width", "height", "advance_x", "left", "top", "data_length", "data_offset", "code_point"])

font_stack = [freetype.Face(f) for f in args.fontstack]
is2Bit = args.is2Bit
size = args.size
font_name = args.name
load_flags = freetype.FT_LOAD_RENDER
if args.force_autohint:
    load_flags |= freetype.FT_LOAD_FORCE_AUTOHINT

# inclusive unicode code point intervals
# must not overlap and be in ascending order
intervals = [
    ### Basic Latin ###
    # ASCII letters, digits, punctuation, control characters
    (0x0000, 0x007F),
    ### Latin-1 Supplement ###
    # Accented characters for Western European languages
    (0x0080, 0x00FF),
    ### Latin Extended-A ###
    # Eastern European and Baltic languages
    (0x0100, 0x017F),
    ### General Punctuation (core subset) ###
    # Smart quotes, en dash, em dash, ellipsis, NO-BREAK SPACE
    (0x2000, 0x206F),
    ### Basic Symbols From "Latin-1 + Misc" ###
    # dashes, quotes, prime marks
    (0x2010, 0x203A),
    # misc punctuation
    (0x2040, 0x205F),
    # common currency symbols
    (0x20A0, 0x20CF),
    ### Combining Diacritical Marks (minimal subset) ###
    # Needed for proper rendering of many extended Latin languages
    (0x0300, 0x036F),
    ### Greek & Coptic ###
    # Used in science, maths, philosophy, some academic texts
    # (0x0370, 0x03FF),
    ### Cyrillic ###
    # Russian, Ukrainian, Bulgarian, etc.
    (0x0400, 0x04FF),
    ### Math Symbols (common subset) ###
    # Superscripts and Subscripts
    (0x2070, 0x209F),
    # General math operators
    (0x2200, 0x22FF),
    # Arrows
    (0x2190, 0x21FF),
    ### CJK ###
    # Core Unified Ideographs
    # (0x4E00, 0x9FFF),
    # # Extension A
    # (0x3400, 0x4DBF),
    # # Extension B
    # (0x20000, 0x2A6DF),
    # # Extension C–F
    # (0x2A700, 0x2EBEF),
    # # Extension G
    # (0x30000, 0x3134F),
    # # Hiragana
    # (0x3040, 0x309F),
    # # Katakana
    # (0x30A0, 0x30FF),
    # # Katakana Phonetic Extensions
    # (0x31F0, 0x31FF),
    # # Halfwidth Katakana
    # (0xFF60, 0xFF9F),
    # # Hangul Syllables
    # (0xAC00, 0xD7AF),
    # # Hangul Jamo
    # (0x1100, 0x11FF),
    # # Hangul Compatibility Jamo
    # (0x3130, 0x318F),
    # # Hangul Jamo Extended-A
    # (0xA960, 0xA97F),
    # # Hangul Jamo Extended-B
    # (0xD7B0, 0xD7FF),
    # # CJK Radicals Supplement
    # (0x2E80, 0x2EFF),
    # # Kangxi Radicals
    # (0x2F00, 0x2FDF),
    # # CJK Symbols and Punctuation
    # (0x3000, 0x303F),
    # # CJK Compatibility Forms
    # (0xFE30, 0xFE4F),
    # # CJK Compatibility Ideographs
    # (0xF900, 0xFAFF),
    ### Specials
    # Replacement Character
    (0xFFFD, 0xFFFD),
]

add_ints = []
if args.additional_intervals:
    add_ints = [tuple([int(n, base=0) for n in i.split(",")]) for i in args.additional_intervals]

def norm_floor(val):
    return int(math.floor(val / (1 << 6)))

def norm_ceil(val):
    return int(math.ceil(val / (1 << 6)))

def chunks(l, n):
    for i in range(0, len(l), n):
        yield l[i:i + n]

def load_glyph(code_point):
    face_index = 0
    while face_index < len(font_stack):
        face = font_stack[face_index]
        glyph_index = face.get_char_index(code_point)
        if glyph_index > 0:
            face.load_glyph(glyph_index, load_flags)
            return face
        face_index += 1
    print(f"code point {code_point} ({hex(code_point)}) not found in font stack!", file=sys.stderr)
    return None

unmerged_intervals = sorted(intervals + add_ints)
intervals = []
unvalidated_intervals = []
for i_start, i_end in unmerged_intervals:
    if len(unvalidated_intervals) > 0 and i_start + 1 <= unvalidated_intervals[-1][1]:
        unvalidated_intervals[-1] = (unvalidated_intervals[-1][0], max(unvalidated_intervals[-1][1], i_end))
        continue
    unvalidated_intervals.append((i_start, i_end))

for i_start, i_end in unvalidated_intervals:
    start = i_start
    for code_point in range(i_start, i_end + 1):
        face = load_glyph(code_point)
        if face is None:
            if start < code_point:
                intervals.append((start, code_point - 1))
            start = code_point + 1
    if start != i_end + 1:
        intervals.append((start, i_end))

for face in font_stack:
    face.set_char_size(size << 6, size << 6, 150, 150)

total_size = 0
all_glyphs = []

for i_start, i_end in intervals:
    for code_point in range(i_start, i_end + 1):
        face = load_glyph(code_point)
        bitmap = face.glyph.bitmap

        # Build out 4-bit greyscale bitmap
        pixels4g = []
        px = 0
        for i, v in enumerate(bitmap.buffer):
            y = i / bitmap.width
            x = i % bitmap.width
            if x % 2 == 0:
                px = (v >> 4)
            else:
                px = px | (v & 0xF0)
                pixels4g.append(px);
                px = 0
            # eol
            if x == bitmap.width - 1 and bitmap.width % 2 > 0:
                pixels4g.append(px)
                px = 0

        if is2Bit:
            # 0-3 white, 4-7 light grey, 8-11 dark grey, 12-15 black
            # Downsample to 2-bit bitmap
            pixels2b = []
            px = 0
            pitch = (bitmap.width // 2) + (bitmap.width % 2)
            for y in range(bitmap.rows):
                for x in range(bitmap.width):
                    px = px << 2
                    bm = pixels4g[y * pitch + (x // 2)]
                    bm = (bm >> ((x % 2) * 4)) & 0xF

                    if bm >= 12:
                        px += 3
                    elif bm >= 8:
                        px += 2
                    elif bm >= 4:
                        px += 1

                    if (y * bitmap.width + x) % 4 == 3:
                        pixels2b.append(px)
                        px = 0
            if (bitmap.width * bitmap.rows) % 4 != 0:
                px = px << (4 - (bitmap.width * bitmap.rows) % 4) * 2
                pixels2b.append(px)

            # for y in range(bitmap.rows):
            #     line = ''
            #     for x in range(bitmap.width):
            #         pixelPosition = y * bitmap.width + x
            #         byte = pixels2b[pixelPosition // 4]
            #         bit_index = (3 - (pixelPosition % 4)) * 2
            #         line += '#' if ((byte >> bit_index) & 3) > 0 else '.'
            #     print(line)
            # print('')
        else:
            # Downsample to 1-bit bitmap - treat any 2+ as black
            pixelsbw = []
            px = 0
            pitch = (bitmap.width // 2) + (bitmap.width % 2)
            for y in range(bitmap.rows):
                for x in range(bitmap.width):
                    px = px << 1
                    bm = pixels4g[y * pitch + (x // 2)]
                    px += 1 if ((x & 1) == 0 and bm & 0xE > 0) or ((x & 1) == 1 and bm & 0xE0 > 0) else 0

                    if (y * bitmap.width + x) % 8 == 7:
                        pixelsbw.append(px)
                        px = 0
            if (bitmap.width * bitmap.rows) % 8 != 0:
                px = px << (8 - (bitmap.width * bitmap.rows) % 8)
                pixelsbw.append(px)

            # for y in range(bitmap.rows):
            #     line = ''
            #     for x in range(bitmap.width):
            #         pixelPosition = y * bitmap.width + x
            #         byte = pixelsbw[pixelPosition // 8]
            #         bit_index = 7 - (pixelPosition % 8)
            #         line += '#' if (byte >> bit_index) & 1 else '.'
            #     print(line)
            # print('')

        pixels = pixels2b if is2Bit else pixelsbw

        # Build output data
        packed = bytes(pixels)
        glyph = GlyphProps(
            width = bitmap.width,
            height = bitmap.rows,
            advance_x = norm_floor(face.glyph.advance.x),
            left = face.glyph.bitmap_left,
            top = face.glyph.bitmap_top,
            data_length = len(packed),
            data_offset = total_size,
            code_point = code_point,
        )
        total_size += len(packed)
        all_glyphs.append((glyph, packed))

# pipe seems to be a good heuristic for the "real" descender
face = load_glyph(ord('|'))

glyph_data = []
glyph_props = []
for index, glyph in enumerate(all_glyphs):
    props, packed = glyph
    glyph_data.extend([b for b in packed])
    glyph_props.append(props)

compress = args.compress

# Build groups for compression
if compress:
    # Script-based grouping: glyphs that co-occur in typical text rendering
    # are grouped together for efficient LRU caching on the embedded target.
    # Since glyphs are in codepoint order, glyphs in the same Unicode block
    # are contiguous in the array and form natural groups.
    SCRIPT_GROUP_RANGES = [
        (0x0000, 0x007F),   # ASCII
        (0x0080, 0x00FF),   # Latin-1 Supplement
        (0x0100, 0x017F),   # Latin Extended-A
        (0x0300, 0x036F),   # Combining Diacritical Marks
        (0x0400, 0x04FF),   # Cyrillic
        (0x2000, 0x206F),   # General Punctuation
        (0x2070, 0x209F),   # Superscripts & Subscripts
        (0x20A0, 0x20CF),   # Currency Symbols
        (0x2190, 0x21FF),   # Arrows
        (0x2200, 0x22FF),   # Math Operators
        (0xFFFD, 0xFFFD),   # Replacement Character
    ]

    def get_script_group(code_point):
        for i, (start, end) in enumerate(SCRIPT_GROUP_RANGES):
            if start <= code_point <= end:
                return i
        return -1

    groups = []  # list of (first_glyph_index, glyph_count)
    current_group_id = None
    group_start = 0
    group_count = 0

    for i, (props, packed) in enumerate(all_glyphs):
        sg = get_script_group(props.code_point)
        if sg != current_group_id:
            if group_count > 0:
                groups.append((group_start, group_count))
            current_group_id = sg
            group_start = i
            group_count = 1
        else:
            group_count += 1

    if group_count > 0:
        groups.append((group_start, group_count))

    # Compress each group
    compressed_groups = []  # list of (compressed_bytes, uncompressed_size, glyph_count, first_glyph_index)
    compressed_bitmap_data = []
    compressed_offset = 0

    # Also build modified glyph props with within-group offsets
    modified_glyph_props = list(glyph_props)

    for first_idx, count in groups:
        # Concatenate bitmap data for this group
        group_data = b''
        for gi in range(first_idx, first_idx + count):
            props, packed = all_glyphs[gi]
            # Update glyph's dataOffset to be within-group offset
            within_group_offset = len(group_data)
            old_props = modified_glyph_props[gi]
            modified_glyph_props[gi] = GlyphProps(
                width=old_props.width,
                height=old_props.height,
                advance_x=old_props.advance_x,
                left=old_props.left,
                top=old_props.top,
                data_length=old_props.data_length,
                data_offset=within_group_offset,
                code_point=old_props.code_point,
            )
            group_data += packed

        # Compress with raw DEFLATE (no zlib/gzip header)
        compressor = zlib.compressobj(level=9, wbits=-15)
        compressed = compressor.compress(group_data) + compressor.flush()

        compressed_groups.append((compressed, len(group_data), count, first_idx))
        compressed_bitmap_data.extend(compressed)
        compressed_offset += len(compressed)

    glyph_props = modified_glyph_props
    total_compressed = len(compressed_bitmap_data)
    total_uncompressed = len(glyph_data)
    print(f"// Compression: {total_uncompressed} -> {total_compressed} bytes ({100*total_compressed/total_uncompressed:.1f}%), {len(groups)} groups", file=sys.stderr)

print(f"""/**
 * generated by fontconvert.py
 * name: {font_name}
 * size: {size}
 * mode: {'2-bit' if is2Bit else '1-bit'}{'  compressed: true' if compress else ''}
 * Command used: {' '.join(sys.argv)}
 */
#pragma once
#include "EpdFontData.h"
""")

if compress:
    print(f"static const uint8_t {font_name}Bitmaps[{len(compressed_bitmap_data)}] = {{")
    for c in chunks(compressed_bitmap_data, 16):
        print ("    " + " ".join(f"0x{b:02X}," for b in c))
    print ("};\n");
else:
    print(f"static const uint8_t {font_name}Bitmaps[{len(glyph_data)}] = {{")
    for c in chunks(glyph_data, 16):
        print ("    " + " ".join(f"0x{b:02X}," for b in c))
    print ("};\n");

print(f"static const EpdGlyph {font_name}Glyphs[] = {{")
for i, g in enumerate(glyph_props):
    print ("    { " + ", ".join([f"{a}" for a in list(g[:-1])]),"},", f"// {chr(g.code_point) if g.code_point != 92 else '<backslash>'}")
print ("};\n");

print(f"static const EpdUnicodeInterval {font_name}Intervals[] = {{")
offset = 0
for i_start, i_end in intervals:
    print (f"    {{ 0x{i_start:X}, 0x{i_end:X}, 0x{offset:X} }},")
    offset += i_end - i_start + 1
print ("};\n");

if compress:
    print(f"static const EpdFontGroup {font_name}Groups[] = {{")
    compressed_offset = 0
    for compressed, uncompressed_size, count, first_idx in compressed_groups:
        print(f"    {{ {compressed_offset}, {len(compressed)}, {uncompressed_size}, {count}, {first_idx} }},")
        compressed_offset += len(compressed)
    print("};\n")

print(f"static const EpdFontData {font_name} = {{")
print(f"    {font_name}Bitmaps,")
print(f"    {font_name}Glyphs,")
print(f"    {font_name}Intervals,")
print(f"    {len(intervals)},")
print(f"    {norm_ceil(face.size.height)},")
print(f"    {norm_ceil(face.size.ascender)},")
print(f"    {norm_floor(face.size.descender)},")
print(f"    {'true' if is2Bit else 'false'},")
if compress:
    print(f"    {font_name}Groups,")
    print(f"    {len(compressed_groups)},")
else:
    print(f"    nullptr,")
    print(f"    0,")
print("};")