#!/usr/bin/env python


__license__   = 'GPL v3'
__copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
__docformat__ = 'restructuredtext en'

import array
import sys
from itertools import repeat
from operator import itemgetter

from calibre.utils.fonts.sfnt import UnknownTable


def four_byte_type_code():
    for c in 'IL':
        a = array.array(c)
        if a.itemsize == 4:
            return c


def read_array(data, fmt='H'):
    ans = array.array(fmt, data)
    if sys.byteorder != 'big':
        ans.byteswap()
    return ans


class LocaTable(UnknownTable):

    def load_offsets(self, head_table, maxp_table):
        fmt = 'H' if head_table.index_to_loc_format == 0 else four_byte_type_code()
        locs = read_array(self.raw, fmt)
        self.offset_map = locs.tolist()
        if fmt == 'H':
            self.offset_map = [2*i for i in self.offset_map]
        self.fmt = fmt

    def glyph_location(self, glyph_id):
        offset = self.offset_map[glyph_id]
        next_offset = self.offset_map[glyph_id+1]
        return offset, next_offset - offset

    def update(self, resolved_glyph_map):
        '''
        Update this table to contain pointers only to the glyphs in
        resolved_glyph_map which must be a map of glyph_ids to (offset, sz)
        Note that the loca table is generated for all glyphs from 0 to the
        largest glyph that is either in resolved_glyph_map or was present
        originally. The pointers to glyphs that have no data will be set to
        zero. This preserves glyph ids.
        '''
        current_max_glyph_id = len(self.offset_map) - 2
        max_glyph_id = max(resolved_glyph_map or (0,))
        max_glyph_id = max(max_glyph_id, current_max_glyph_id)
        self.offset_map = list(repeat(0, max_glyph_id + 2))
        glyphs = [(glyph_id, x[0], x[1]) for glyph_id, x in resolved_glyph_map.items()]
        glyphs.sort(key=itemgetter(1))
        for glyph_id, offset, sz in glyphs:
            self.offset_map[glyph_id] = offset
            self.offset_map[glyph_id+1] = offset + sz
        # Fix all zero entries to be the same as the previous entry, which
        # means that if the ith entry is zero, the i-1 glyph is not present.
        for i in range(1, len(self.offset_map)):
            if self.offset_map[i] == 0:
                self.offset_map[i] = self.offset_map[i-1]

        vals = self.offset_map
        max_offset = max(vals) if vals else 0
        if max_offset < 0x20000 and all(l % 2 == 0 for l in vals):
            self.fmt = 'H'
            vals = array.array(self.fmt, (i // 2 for i in vals))
        else:
            self.fmt = four_byte_type_code()
            vals = array.array(self.fmt, vals)

        if sys.byteorder != 'big':
            vals.byteswap()
        self.raw = vals.tobytes()
    subset = update

    def dump_glyphs(self, sfnt):
        if not hasattr(self, 'offset_map'):
            self.load_offsets(sfnt[b'head'], sfnt[b'maxp'])
        for i in range(len(self.offset_map)-1):
            off, noff = self.offset_map[i], self.offset_map[i+1]
            if noff != off:
                print('Glyph id:', i, 'size:', noff-off)
