#!/usr/bin/env python


__license__ = 'GPL v3'
__copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'

import regex


class Parser:
    ''' See epubcfi.ebnf for the specification that this parser tries to
    follow. I have implemented it manually, since I don't want to depend on
    grako, and the grammar is pretty simple. This parser is thread-safe, i.e.
    it can be used from multiple threads simultaneously. '''

    def __init__(self):
        # All allowed unicode characters + escaped special characters
        special_char = r'[\[\](),;=^]'
        unescaped_char = f'[[\t\n\r -\ud7ff\ue000-\ufffd\U00010000-\U0010ffff]--{special_char}]'
        # calibre used to escape hyphens as well, so recognize them even though
        # not strictly spec compliant
        escaped_char = r'\^' + special_char[:-1] + '-]'
        chars = fr'(?:{unescaped_char}|(?:{escaped_char}))+'
        chars_no_space = chars.replace('0020', '0021')
        # No leading zeros allowed for integers
        integer = r'(?:[1-9][0-9]*)|0'
        # No leading zeros, except for numbers in (0, 1) and no trailing zeros for the fractional part
        frac = r'\.[0-9]{1,}'
        number = rf'(?:[1-9][0-9]*(?:{frac})?)|(?:0{frac})|(?:0)'
        def c(x):
            return regex.compile(x, flags=regex.VERSION1)

        # A step of the form /integer
        self.step_pat = c(rf'/({integer})')
        # An id assertion of the form [characters]
        self.id_assertion_pat = c(rf'\[({chars})\]')

        # A text offset of the form :integer
        self.text_offset_pat = c(rf':({integer})')
        # A temporal offset of the form ~number
        self.temporal_offset_pat = c(rf'~({number})')
        # A spatial offset of the form @number:number
        self.spatial_offset_pat = c(rf'@({number}):({number})')
        # A spatio-temporal offset of the form ~number@number:number
        self.st_offset_pat = c(rf'~({number})@({number}):({number})')

        # Text assertion patterns
        self.ta1_pat = c(rf'({chars})(?:,({chars})){{0,1}}')
        self.ta2_pat = c(rf',({chars})')
        self.parameters_pat = c(fr'(?:;({chars_no_space})=((?:{chars},?)+))+')
        self.csv_pat = c(rf'(?:({chars}),?)+')

        # Unescape characters
        unescape_pat = c(fr'{escaped_char[:2]}({escaped_char[2:]})')
        self.unescape = lambda x: unescape_pat.sub(r'\1', x)

    def parse_epubcfi(self, raw):
        ' Parse a full epubcfi of the form epubcfi(path [ , path , path ]) '
        null = {}, {}, {}, raw
        if not raw:
            return null

        if not raw.startswith('epubcfi('):
            return null
        raw = raw[len('epubcfi('):]
        parent_cfi, raw = self.parse_path(raw)
        if not parent_cfi:
            return null
        start_cfi, end_cfi = {}, {}
        if raw.startswith(','):
            start_cfi, raw = self.parse_path(raw[1:])
            if raw.startswith(','):
                end_cfi, raw = self.parse_path(raw[1:])
            if not start_cfi or not end_cfi:
                return null
        if raw.startswith(')'):
            raw = raw[1:]
        else:
            return null

        return parent_cfi, start_cfi, end_cfi, raw

    def parse_path(self, raw):
        ' Parse the path component of an epubcfi of the form /step... '
        path = {'steps':[]}
        raw = self._parse_path(raw, path)
        if not path['steps']:
            path = {}
        return path, raw

    def do_match(self, pat, raw):
        m = pat.match(raw)
        if m is not None:
            raw = raw[len(m.group()):]
        return m, raw

    def _parse_path(self, raw, ans):
        m, raw = self.do_match(self.step_pat, raw)
        if m is None:
            return raw
        ans['steps'].append({'num':int(m.group(1))})
        m, raw = self.do_match(self.id_assertion_pat, raw)
        if m is not None:
            ans['steps'][-1]['id'] = self.unescape(m.group(1))
        if raw.startswith('!'):
            ans['redirect'] = r = {'steps':[]}
            return self._parse_path(raw[1:], r)
        else:
            remaining_raw = self.parse_offset(raw, ans['steps'][-1])
            return self._parse_path(raw, ans) if remaining_raw is None else remaining_raw

    def parse_offset(self, raw, ans):
        m, raw = self.do_match(self.text_offset_pat, raw)
        if m is not None:
            ans['text_offset'] = int(m.group(1))
            return self.parse_text_assertion(raw, ans)
        m, raw = self.do_match(self.st_offset_pat, raw)
        if m is not None:
            t, x, y = m.groups()
            ans['temporal_offset'] = float(t)
            ans['spatial_offset'] = tuple(map(float, (x, y)))
            return raw
        m, raw = self.do_match(self.temporal_offset_pat, raw)
        if m is not None:
            ans['temporal_offset'] = float(m.group(1))
            return raw
        m, raw = self.do_match(self.spatial_offset_pat, raw)
        if m is not None:
            ans['spatial_offset'] = tuple(map(float, m.groups()))
            return raw

    def parse_text_assertion(self, raw, ans):
        oraw = raw
        if not raw.startswith('['):
            return oraw
        raw = raw[1:]
        ta = {}
        m, raw = self.do_match(self.ta1_pat, raw)
        if m is not None:
            before, after = m.groups()
            ta['before'] = self.unescape(before)
            if after is not None:
                ta['after'] = self.unescape(after)
        else:
            m, raw = self.do_match(self.ta2_pat, raw)
            if m is not None:
                ta['after'] = self.unescape(m.group(1))

        # parse parameters
        m, raw = self.do_match(self.parameters_pat, raw)
        if m is not None:
            params = {}
            for name, value in zip(m.captures(1), m.captures(2)):
                params[name] = tuple(map(self.unescape, self.csv_pat.match(value).captures(1)))
            if params:
                ta['params'] = params

        if not raw.startswith(']'):
            return oraw  # no closing ] or extra content in the assertion

        if ta:
            ans['text_assertion'] = ta
        return raw[1:]


_parser = None


def parser():
    global _parser
    if _parser is None:
        _parser = Parser()
    return _parser


def get_steps(pcfi):
    ans = tuple(pcfi['steps'])
    if 'redirect' in pcfi:
        ans += get_steps(pcfi['redirect'])
    return ans


def cfi_sort_key(cfi, only_path=True):
    p = parser()
    try:
        if only_path:
            pcfi = p.parse_path(cfi)[0]
        else:
            parent, start = p.parse_epubcfi(cfi)[:2]
            pcfi = start or parent
    except Exception:
        import traceback
        traceback.print_exc()
        return (), (0, (0, 0), 0)
    if not pcfi:
        import sys
        print(f'Failed to parse CFI: {cfi!r}', file=sys.stderr)
        return (), (0, (0, 0), 0)
    steps = get_steps(pcfi)
    step_nums = tuple(s.get('num', 0) for s in steps)
    step = steps[-1] if steps else {}
    offsets = (step.get('temporal_offset', 0), tuple(reversed(step.get('spatial_offset', (0, 0)))), step.get('text_offset', 0), )
    return step_nums, offsets


def decode_cfi(root, cfi):
    from lxml.etree import XPathEvalError
    p = parser()
    try:
        pcfi = p.parse_path(cfi)[0]
    except Exception:
        import traceback
        traceback.print_exc()
        return
    if not pcfi:
        import sys
        print(f'Failed to parse CFI: {pcfi!r}', file=sys.stderr)
        return
    steps = get_steps(pcfi)
    ans = root
    for step in steps:
        num = step.get('num', 0)
        node_id = step.get('id')
        try:
            match = ans.xpath(f'descendant::*[@id="{node_id}"]')
        except XPathEvalError:
            match = ()
        if match:
            ans = match[0]
            continue
        index = 0
        for child in ans.iterchildren('*'):
            index |= 1  # increment index by 1 if it is even
            index += 1
            if index == num:
                ans = child
                break
        else:
            return
    return ans


if __name__ == '__main__':
    import sys
    print(cfi_sort_key(sys.argv[-1], only_path=False))
