#!/usr/bin/env python3
"""Fetch holidays from gov.cn  """

import argparse
import json
import re
from datetime import date, timedelta
from typing import Iterator, List, Optional, Tuple

import bs4
import requests

SEARCH_URL = ('http://sousuo.gov.cn/s.htm'
              '?t=paper&advance=true&sort=&title={year}+%E8%8A%82%E5%81%87%E6%97%A5'
              '&puborg=%E5%9B%BD%E5%8A%A1%E9%99%A2%E5%8A%9E%E5%85%AC%E5%8E%85'
              '&pcodeJiguan=%E5%9B%BD%E5%8A%9E%E5%8F%91%E6%98%8E%E7%94%B5')


def get_paper_urls(year: int) -> List[str]:
    """Find year related paper urls.

    Args:
        year (int): eg. 2018

    Returns:
        List[str]: Urls
    """

    url = SEARCH_URL.format(year=year)
    body = requests.get(url).text
    ret = re.findall(
        r'<li class="res-list".*?<a href="(.+?)".*?</li>', body, flags=re.S)

    return ret


def get_paper(url: str) -> str:
    """Extract paper text from url.

    Args:
        url (str): Paper url.

    Returns:
        str: Extracted paper text.
    """

    assert re.match(r'http://www.gov.cn/zhengce/content/\d{4}-\d{2}/\d{2}/content_\d+.htm',
                    url), 'Site changed, need human verify'

    response = requests.get(url)
    response.encoding = 'utf-8'
    soup = bs4.BeautifulSoup(response.text, features='html.parser')
    container = soup.find('td', class_='b12c')
    assert container, f'Can not get paper container from url: {url}'
    ret = container.get_text().replace('\u3000\u3000', '\n')
    assert ret, f'Can not get paper context from url: {url}'
    return ret


def get_rules(paper: str) -> Iterator[Tuple[str, str]]:
    """Extract rules from paper.

    Args:
        paper (str): Paper text

    Raises:
        NotImplementedError: When find no rules.

    Returns:
        Iterator[Tuple[str, str]]: (name, description)
    """

    lines: list = paper.splitlines()
    count = 0
    for i in sorted(set(lines), key=lines.index):
        match = re.match(r'[一二三四五六七八九十]、(.+?)：(.+)', i)
        if match:
            count += 1
            yield match.groups()

    if not count:
        raise NotImplementedError(lines)


def _cast_int(value):
    return int(value) if value else None


class SentenceParser:
    """Parser for holiday shift description sentence. """

    def __init__(self, sentence, year):
        self.sentence = sentence
        self.year = year
        self._date_memory = set()

    def extract_dates(self, text: str) -> Iterator[date]:
        """Extract date from text.

        Args:
            text (str): Text to extract

        Returns:
            Iterator[date]: Extracted dates.
        """

        count = 0
        for method in self.date_extraction_methods:
            for i in method(self, text):
                count += 1
                if i in self._date_memory:
                    continue
                self._date_memory.add(i)
                yield i

        if not count:
            raise NotImplementedError(text)

    def get_date(self, year: Optional[int], month: int, day: int) -> date:
        """Get date in context.

        Args:
            year (Optional[int]): year
            month (int): month
            day (int): day

        Returns:
            date: Date result
        """

        # Special case: 12 month may mean previous year
        if (year is None
                and month == 12
                and self._date_memory
                and max(self._date_memory) < date(year=self.year, month=2, day=1)):
            year = self.year - 1

        year = year or self.year
        return date(year=year, month=month, day=day)

    def _extract_dates_1(self, value):
        match = re.match(r'(?:(\d+)年)?(?:(\d+)月)(\d+)日', value)
        if match:
            groups = [_cast_int(i) for i in match.groups()]
            assert len(groups) == 3, groups
            yield self.get_date(year=groups[0], month=groups[1], day=groups[2])

    def _extract_dates_2(self, value):
        match = re.match(
            r'(?:(\d+)年)?(?:(\d+)月)(\d+)日(?:至|-|—)(?:(\d+)年)?(?:(\d+)月)?(\d+)日', value)
        if match:
            groups = [_cast_int(i) for i in match.groups()]
            assert len(groups) == 6, groups
            start = self.get_date(year=groups[0],
                                  month=groups[1], day=groups[2])
            end = self.get_date(year=groups[3],
                                month=groups[4] or groups[1], day=groups[5])
            for i in range((end - start).days + 1):
                yield start + timedelta(days=i)

    def _extract_dates_3(self, value):
        match = re.match(
            r'(?:(\d+)年)?(?:(\d+)月)(\d+)日(?:（[^）]+）)?'
            r'(?:、(?:(\d+)年)?(?:(\d+)月)?(\d+)日(?:（[^）]+）)?)+',
            value.replace('(', '（').replace(')', '）'))
        if match:
            groups = [_cast_int(i) for i in match.groups()]
            assert not (len(groups) % 3), groups
            year = self.year
            month = None
            day = None
            for i in range(0, len(groups), 3):
                year = groups[i]
                month = groups[i+1] or month
                day = groups[i+2]
                assert month
                assert day
                yield self.get_date(year=year, month=month, day=day)

    date_extraction_methods = [
        _extract_dates_1,
        _extract_dates_2,
        _extract_dates_3
    ]

    def parse(self, memory: set) -> Iterator[dict]:
        """Parse days with memory

        Args:
            memory (set): Date memory

        Returns:
            Iterator[dict]: Days without name field.
        """

        self._date_memory = memory
        for method in self.parsing_methods:
            for i in method(self):
                yield i

    def _parse_rest_1(self):
        match = re.match(r'(.+)(放假|补休|调休|公休)+(?:\d+天)?$', self.sentence)
        if match:
            for i in self.extract_dates(match.group(1)):
                yield {
                    'date': i,
                    'isOffDay': True
                }

    def _parse_work_1(self):
        match = re.match('(.+)上班$', self.sentence)
        if match:
            for i in self.extract_dates(match.group(1)):
                yield {
                    'date': i,
                    'isOffDay': False
                }

    def _parse_shift_1(self):
        match = re.match('(.+)公休日调至(.+)', self.sentence)
        if match:
            for i in self.extract_dates(match.group(1)):
                yield {
                    'date': i,
                    'isOffDay': False
                }
            for i in self.extract_dates(match.group(2)):
                yield {
                    'date': i,
                    'isOffDay': True
                }

    parsing_methods = [
        _parse_rest_1,
        _parse_work_1,
        _parse_shift_1,
    ]


class DescriptionParser:
    """Parser for holiday shift description.  """

    def __init__(self, description):
        self.description = description
        self._date_memory = set()

    def parse(self, year: int) -> Iterator[dict]:
        """Generator for description parsing result.

        Args:
            year (int): Context year
        """

        self._date_memory.clear()
        for i in re.split('，|。', self.description):
            for j in SentenceParser(i, year).parse(self._date_memory):
                yield j

        if not self._date_memory:
            raise NotImplementedError(self.description)


def fetch_holiday(year: int):
    """Fetch holiday data.  """

    papers = get_paper_urls(year)

    days = []
    for i in papers:
        paper = get_paper(i)
        rules = get_rules(paper)
        for name, description in rules:
            days.extend({
                'name': name,
                **j
            } for j in DescriptionParser(description).parse(year))
    return {
        'year': year,
        'papers': papers,
        'days': sorted(days, key=lambda x: x['date'])
    }


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('year', type=int)
    args = parser.parse_args()
    year = args.year

    print(json.dumps(fetch_holiday(year),
                     indent=4,
                     ensure_ascii=False,
                     cls=CustomJSONEncoder))


class CustomJSONEncoder(json.JSONEncoder):
    """Custom json encoder. """

    def default(self, o):
        # pylint:disable=method-hidden
        if isinstance(o, date):
            return o.isoformat()

        return super().default(o)


if __name__ == '__main__':
    main()