#!/usr/bin/env python

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

from collections import namedtuple
from io import BytesIO
from struct import pack

from calibre.ebooks.mobi.utils import CNCX, align_block, encint
from calibre.ebooks.mobi.writer8.header import Header

TagMeta_ = namedtuple('TagMeta', 'name number values_per_entry bitmask end_flag')


def TagMeta(x):
    return TagMeta_(*x)


EndTagTable = TagMeta(('eof', 0, 0, 0, 1))

# map of mask to number of shifts needed, works with 1 bit and two-bit wide masks
# could also be extended to 4 bit wide ones as well
mask_to_bit_shifts = {1:0, 2:1, 3:0, 4:2, 8:3, 12:2, 16:4, 32:5, 48:4, 64:6,
        128:7, 192: 6}


class IndexHeader(Header):  # {{{

    HEADER_NAME = b'INDX'
    ALIGN_BLOCK = True
    HEADER_LENGTH = 192

    DEFINITION = f'''
    # 4 - 8: Header Length
    header_length = {HEADER_LENGTH}

    # 8 - 16: Unknown
    unknown1 = zeroes(8)

    # 16 - 20: Index type: 0 - normal 2 - inflection
    type = 2

    # 20 - 24: IDXT offset (filled in later)
    idxt_offset

    # 24 - 28: Number of index records
    num_of_records = DYN

    # 28 - 32: Index encoding (65001 = utf-8)
    encoding = 65001

    # 32 - 36: Unknown
    unknown2 = NULL

    # 36 - 40: Number of Index entries
    num_of_entries = DYN

    # 40 - 44: ORDT offset
    ordt_offset

    # 44 - 48: LIGT offset
    ligt_offset

    # 48 - 52: Number of ORDT/LIGT? entries
    num_of_ordt_entries

    # 52 - 56: Number of CNCX records
    num_of_cncx = DYN

    # 56 - 180: Unknown
    unknown3 = zeroes(124)

    # 180 - 184: TAGX offset
    tagx_offset = {HEADER_LENGTH}

    # 184 - 192: Unknown
    unknown4 = zeroes(8)

    # TAGX
    tagx = DYN

    # Geometry of index records
    geometry = DYN

    # IDXT
    idxt = DYN
    '''

    POSITIONS = {'idxt_offset':'idxt'}
# }}}


class Index:  # {{{

    control_byte_count = 1
    cncx = CNCX()
    tag_types = (EndTagTable,)

    HEADER_LENGTH = IndexHeader.HEADER_LENGTH

    @classmethod
    def generate_tagx(cls):
        header = b'TAGX'
        byts = bytearray()
        for tag_meta in cls.tag_types:
            byts.extend(tag_meta[1:])
        # table length, control byte count
        header += pack(b'>II', 12+len(byts), cls.control_byte_count)
        return header + bytes(byts)

    @classmethod
    def calculate_control_bytes_for_each_entry(cls, entries):
        control_bytes = []
        for lead_text, tags in entries:
            cbs = []
            ans = 0
            for (name, number, vpe, mask, endi) in cls.tag_types:
                if endi == 1:
                    cbs.append(ans)
                    ans = 0
                    continue
                try:
                    nvals = len(tags.get(name, ()))
                except TypeError:
                    nvals = 1
                nentries = nvals // vpe
                shifts = mask_to_bit_shifts[mask]
                ans |= mask & (nentries << shifts)
            if len(cbs) != cls.control_byte_count:
                raise ValueError(f'The entry {[lead_text, tags]!r} is invalid')
            control_bytes.append(cbs)
        return control_bytes

    def __call__(self):
        self.control_bytes = self.calculate_control_bytes_for_each_entry(
                self.entries)

        index_blocks, idxt_blocks, record_counts, last_indices = [BytesIO()], [BytesIO()], [0], [b'']
        buf = BytesIO()

        RECORD_LIMIT = 0x10000 - self.HEADER_LENGTH - 1048  # kindlegen uses 1048 (there has to be some margin because of block alignment)

        for i, (index_num, tags) in enumerate(self.entries):
            control_bytes = self.control_bytes[i]
            buf.seek(0), buf.truncate(0)
            index_num = (index_num.encode('utf-8') if isinstance(index_num, str) else index_num)
            raw = bytearray(index_num)
            raw.insert(0, len(index_num))
            buf.write(bytes(raw))
            buf.write(bytes(bytearray(control_bytes)))
            for tag in self.tag_types:
                values = tags.get(tag.name, None)
                if values is None:
                    continue
                try:
                    len(values)
                except TypeError:
                    values = [values]
                if values:
                    for val in values:
                        try:
                            buf.write(encint(val))
                        except ValueError:
                            raise ValueError(f'Invalid values for {tag!r}: {values!r}')
            raw = buf.getvalue()
            offset = index_blocks[-1].tell()
            idxt_pos = idxt_blocks[-1].tell()
            if offset + idxt_pos + len(raw) + 2 > RECORD_LIMIT:
                index_blocks.append(BytesIO())
                idxt_blocks.append(BytesIO())
                record_counts.append(0)
                offset = idxt_pos = 0
                last_indices.append(b'')
            record_counts[-1] += 1
            idxt_blocks[-1].write(pack(b'>H', self.HEADER_LENGTH+offset))
            index_blocks[-1].write(raw)
            last_indices[-1] = index_num

        index_records = []
        for index_block, idxt_block, record_count in zip(index_blocks, idxt_blocks, record_counts):
            index_block = align_block(index_block.getvalue())
            idxt_block = align_block(b'IDXT' + idxt_block.getvalue())
            # Create header for this index record
            header = b'INDX'
            buf.seek(0), buf.truncate(0)
            buf.write(pack(b'>I', self.HEADER_LENGTH))
            buf.write(b'\0'*4)  # Unknown
            buf.write(pack(b'>I', 1))  # Header type (0 for Index header record and 1 for Index records)
            buf.write(b'\0'*4)  # Unknown

            # IDXT block offset
            buf.write(pack(b'>I', self.HEADER_LENGTH + len(index_block)))

            # Number of index entries in this record
            buf.write(pack(b'>I', record_count))

            buf.write(b'\xff'*8)  # Unknown

            buf.write(b'\0'*156)  # Unknown

            header += buf.getvalue()
            index_records.append(header + index_block + idxt_block)
            if len(index_records[-1]) > 0x10000:
                raise ValueError('Failed to rollover index blocks for very large index.')

        # Create the Index Header record
        tagx = self.generate_tagx()

        # Geometry of the index records is written as index entries pointed to
        # by the IDXT records
        buf.seek(0), buf.truncate()
        idxt = [b'IDXT']
        pos = IndexHeader.HEADER_LENGTH + len(tagx)
        for last_idx, num in zip(last_indices, record_counts):
            start = buf.tell()
            idxt.append(pack(b'>H', pos))
            buf.write(bytes(bytearray([len(last_idx)])) + last_idx)
            buf.write(pack(b'>H', num))
            pos += buf.tell() - start

        header = {
                'num_of_entries': sum(r for r in record_counts),
                'num_of_records': len(index_records),
                'num_of_cncx': len(self.cncx),
                'tagx':align_block(tagx),
                'geometry':align_block(buf.getvalue()),
                'idxt':align_block(b''.join(idxt)),
        }
        header = IndexHeader()(**header)
        self.records = [header] + index_records
        self.records.extend(self.cncx.records)
        return self.records
# }}}


class SkelIndex(Index):

    tag_types = tuple(map(TagMeta, (
        ('chunk_count', 1, 1, 3, 0),
        ('geometry',    6, 2, 12, 0),
        EndTagTable
    )))

    def __init__(self, skel_table):
        self.entries = [
                (s.name, {
                    # Don't ask me why these entries have to be repeated twice
                    'chunk_count':(s.chunk_count, s.chunk_count),
                    'geometry':(s.start_pos, s.length, s.start_pos, s.length),
                    }) for s in skel_table
        ]


class ChunkIndex(Index):

    tag_types = tuple(map(TagMeta, (
        ('cncx_offset',     2, 1, 1, 0),
        ('file_number',     3, 1, 2, 0),
        ('sequence_number', 4, 1, 4, 0),
        ('geometry',        6, 2, 8, 0),
        EndTagTable
    )))

    def __init__(self, chunk_table):
        self.cncx = CNCX(c.selector for c in chunk_table)

        self.entries = [
                (f'{c.insert_pos:010}', {

                    'cncx_offset':self.cncx[c.selector],
                    'file_number':c.file_number,
                    'sequence_number':c.sequence_number,
                    'geometry':(c.start_pos, c.length),
                    }) for c in chunk_table
        ]


class GuideIndex(Index):

    tag_types = tuple(map(TagMeta, (
        ('title',   1, 1, 1, 0),
        ('pos_fid', 6, 2, 2, 0),
        EndTagTable
    )))

    def __init__(self, guide_table):
        self.cncx = CNCX(c.title for c in guide_table)

        self.entries = [
                (r.type, {

                    'title':self.cncx[r.title],
                    'pos_fid':r.pos_fid,
                    }) for r in guide_table
        ]


class NCXIndex(Index):
    ''' The commented out parts have been seen in NCX indexes from MOBI 6
    periodicals. Since we have no MOBI 8 periodicals to reverse engineer, leave
    it for now. '''
    # control_byte_count = 2
    tag_types = tuple(map(TagMeta, (
        ('offset',             1, 1, 1, 0),
        ('length',             2, 1, 2, 0),
        ('label',              3, 1, 4, 0),
        ('depth',              4, 1, 8, 0),
        ('parent',             21, 1, 16, 0),
        ('first_child',        22, 1, 32, 0),
        ('last_child',         23, 1, 64, 0),
        ('pos_fid',            6, 2, 128, 0),
        EndTagTable,
        # ('image',              69, 1, 1, 0),
        # ('description',        70, 1, 2, 0),
        # ('author',             71, 1, 4, 0),
        # ('caption',            72, 1, 8, 0),
        # ('attribution',        73, 1, 16, 0),
        # EndTagTable
    )))

    def __init__(self, toc_table):
        strings = []
        for entry in toc_table:
            strings.append(entry['label'])
            aut = entry.get('author', None)
            if aut:
                strings.append(aut)
            desc = entry.get('description', None)
            if desc:
                strings.append(desc)
            kind = entry.get('kind', None)
            if kind:
                strings.append(kind)
        self.cncx = CNCX(strings)

        try:
            largest = max(x['index'] for x in toc_table)
        except ValueError:
            largest = 0
        fmt = '%0{}X'.format(max(2, len(f'{largest:X}')))

        def to_entry(x):
            ans = {}
            for f in ('offset', 'length', 'depth', 'pos_fid', 'parent',
                    'first_child', 'last_child'):
                if f in x:
                    ans[f] = x[f]
            for f in ('label', 'description', 'author', 'kind'):
                if f in x:
                    ans[f] = self.cncx[x[f]]
            return (fmt % x['index'], ans)

        self.entries = list(map(to_entry, toc_table))


class NonLinearNCXIndex(NCXIndex):
    control_byte_count = 2
    tag_types = tuple(map(TagMeta, (
        ('offset',             1, 1, 1, 0),
        ('length',             2, 1, 2, 0),
        ('label',              3, 1, 4, 0),
        ('depth',              4, 1, 8, 0),
        ('kind',               5, 1, 16, 0),
        ('parent',             21, 1, 32, 0),
        ('first_child',        22, 1, 64, 0),
        ('last_child',         23, 1, 128, 0),
        EndTagTable,
        ('pos_fid',            6, 2, 1, 0),
        EndTagTable
    )))


if __name__ == '__main__':
    # Generate a document with a large number of index entries using both
    # calibre and kindlegen and compare the output
    import os
    import subprocess
    os.chdir('/t')
    paras = [f'<p>{i}</p>' for i in range(4000)]
    raw = '<html><body>' + '\n\n'.join(paras) + '</body></html>'

    src = 'index.html'
    with open(src, 'wb') as f:
        f.write(raw.encode('utf-8'))

    subprocess.check_call(['ebook-convert', src, '.epub', '--level1-toc', '//h:p', '--no-default-epub-cover', '--flow-size', '1000000'])
    subprocess.check_call(['ebook-convert', src, '.azw3', '--level1-toc', '//h:p', '--no-inline-toc', '--extract-to=x'])
    subprocess.call(['kindlegen', 'index.epub'])  # kindlegen exit code is not 0 as we don't have a cover
    subprocess.check_call(['calibre-debug', 'index.mobi'])

    from calibre.gui2.tweak_book.diff.main import main
    main(['cdiff', 'decompiled_index/mobi8/ncx.record', 'x/ncx.record'])
