''' functionality outline for a book data connector '''
from abc import ABC, abstractmethod
from dataclasses import dataclass
import pytz
from urllib3.exceptions import RequestError

from django.db import transaction
from dateutil import parser
import requests
from requests import HTTPError

from bookwyrm import models


class ConnectorException(HTTPError):
    ''' when the connector can't do what was asked '''


class AbstractConnector(ABC):
    ''' generic book data connector '''

    def __init__(self, identifier):
        # load connector settings
        info = models.Connector.objects.get(identifier=identifier)
        self.connector = info

        self.key_mappings = []

        # fields we want to look for in book data to copy over
        # title we handle separately.
        self.book_mappings = []

        # the things in the connector model to copy over
        self_fields = [
            'base_url',
            'books_url',
            'covers_url',
            'search_url',
            'max_query_count',
            'name',
            'identifier',
            'local'
        ]
        for field in self_fields:
            setattr(self, field, getattr(info, field))


    def is_available(self):
        ''' check if you're allowed to use this connector '''
        if self.max_query_count is not None:
            if self.connector.query_count >= self.max_query_count:
                return False
        return True


    def search(self, query, min_confidence=None):
        ''' free text search '''
        resp = requests.get(
            '%s%s' % (self.search_url, query),
            headers={
                'Accept': 'application/json; charset=utf-8',
            },
        )
        if not resp.ok:
            resp.raise_for_status()
        data = resp.json()
        results = []

        for doc in self.parse_search_data(data)[:10]:
            results.append(self.format_search_result(doc))
        return results


    def get_or_create_book(self, remote_id):
        ''' pull up a book record by whatever means possible '''
        # try to load the book
        book = models.Book.objects.select_subclasses().filter(
            origin_id=remote_id
        ).first()
        if book:
            if isinstance(book, models.Work):
                return book.default_edition
            return book

        # no book was found, so we start creating a new one
        data = get_data(remote_id)

        work = None
        edition = None
        if self.is_work_data(data):
            work_data = data
            # if we requested a work and there's already an edition, we're set
            work = self.match_from_mappings(work_data, models.Work)
            if work and work.default_edition:
                return work.default_edition

            # no such luck, we need more information.
            try:
                edition_data = self.get_edition_from_work_data(work_data)
            except KeyError:
                # hack: re-use the work data as the edition data
                # this is why remote ids aren't necessarily unique
                edition_data = data
        else:
            edition_data = data
            edition = self.match_from_mappings(edition_data, models.Edition)
            # no need to figure out about the work if we already know about it
            if edition and edition.parent_work:
                return edition

            # no such luck, we need more information.
            try:
                work_data = self.get_work_from_edition_date(edition_data)
            except KeyError:
                # remember this hack: re-use the work data as the edition data
                work_data = data

        if not work_data or not edition_data:
            raise ConnectorException('Unable to load book data: %s' % remote_id)

        # at this point, we need to figure out the work, edition, or both
        # atomic so that we don't save a work with no edition for vice versa
        with transaction.atomic():
            if not work:
                work_key = self.get_remote_id_from_data(work_data)
                work = self.create_book(work_key, work_data, models.Work)

            if not edition:
                ed_key = self.get_remote_id_from_data(edition_data)
                edition = self.create_book(ed_key, edition_data, models.Edition)
                edition.parent_work = work
                edition.save()
            work.default_edition = edition
            work.save()

        # now's our change to fill in author gaps
        if not edition.authors.exists() and work.authors.exists():
            edition.authors.set(work.authors.all())
            edition.author_text = work.author_text
            edition.save()

        if not edition:
            raise ConnectorException('Unable to create book: %s' % remote_id)

        return edition


    def create_book(self, remote_id, data, model):
        ''' create a work or edition from data '''
        book = model.objects.create(
            origin_id=remote_id,
            title=data['title'],
            connector=self.connector,
        )
        return self.update_book_from_data(book, data)


    def update_book_from_data(self, book, data, update_cover=True):
        ''' for creating a new book or syncing with data '''
        book = update_from_mappings(book, data, self.book_mappings)

        author_text = []
        for author in self.get_authors_from_data(data):
            book.authors.add(author)
            if author.display_name:
                author_text.append(author.display_name)
        book.author_text = ', '.join(author_text)
        book.save()

        if not update_cover:
            return book

        cover = self.get_cover_from_data(data)
        if cover:
            book.cover.save(*cover, save=True)
        return book


    def update_book(self, book, data=None):
        ''' load new data '''
        if not book.sync and not book.sync_cover:
            return book

        if not data:
            key = getattr(book, self.key_name)
            data = self.load_book_data(key)

        if book.sync:
            book = self.update_book_from_data(
                book, data, update_cover=book.sync_cover)
        else:
            cover = self.get_cover_from_data(data)
            if cover:
                book.cover.save(*cover, save=True)

        return book


    def match_from_mappings(self, data, model):
        ''' try to find existing copies of this book using various keys '''
        relevent_mappings = [m for m in self.key_mappings if \
                not m.model or model == m.model]
        for mapping in relevent_mappings:
            # check if this field is present in the data
            value = data.get(mapping.remote_field)
            if not value:
                continue

            # extract the value in the right format
            value = mapping.formatter(value)

            # search our database for a matching book
            kwargs = {mapping.local_field: value}
            match = model.objects.filter(**kwargs).first()
            if match:
                return match
        return None


    @abstractmethod
    def get_remote_id_from_data(self, data):
        ''' otherwise we won't properly set the remote_id in the db '''


    @abstractmethod
    def is_work_data(self, data):
        ''' differentiate works and editions '''


    @abstractmethod
    def get_edition_from_work_data(self, data):
        ''' every work needs at least one edition '''


    @abstractmethod
    def get_work_from_edition_date(self, data):
        ''' every edition needs a work '''


    @abstractmethod
    def get_authors_from_data(self, data):
        ''' load author data '''


    @abstractmethod
    def get_cover_from_data(self, data):
        ''' load cover '''


    @abstractmethod
    def parse_search_data(self, data):
        ''' turn the result json from a search into a list '''


    @abstractmethod
    def format_search_result(self, search_result):
        ''' create a SearchResult obj from json '''


    @abstractmethod
    def expand_book_data(self, book):
        ''' get more info on a book '''


def update_from_mappings(obj, data, mappings):
    ''' assign data to model with mappings '''
    for mapping in mappings:
        # check if this field is present in the data
        value = data.get(mapping.remote_field)
        if not value:
            continue

        # extract the value in the right format
        try:
            value = mapping.formatter(value)
        except:
            continue

        # assign the formatted value to the model
        obj.__setattr__(mapping.local_field, value)
    return obj


def get_date(date_string):
    ''' helper function to try to interpret dates '''
    if not date_string:
        return None

    try:
        return pytz.utc.localize(parser.parse(date_string))
    except ValueError:
        pass

    try:
        return parser.parse(date_string)
    except ValueError:
        return None


def get_data(url):
    ''' wrapper for request.get '''
    try:
        resp = requests.get(
            url,
            headers={
                'Accept': 'application/json; charset=utf-8',
            },
        )
    except RequestError:
        raise ConnectorException()
    if not resp.ok:
        resp.raise_for_status()
    data = resp.json()
    return data


@dataclass
class SearchResult:
    ''' standardized search result object '''
    title: str
    key: str
    author: str
    year: str
    confidence: int = 1

    def __repr__(self):
        return "<SearchResult key={!r} title={!r} author={!r}>".format(
            self.key, self.title, self.author)


class Mapping:
    ''' associate a local database field with a field in an external dataset '''
    def __init__(
            self, local_field, remote_field=None, formatter=None, model=None):
        noop = lambda x: x

        self.local_field = local_field
        self.remote_field = remote_field or local_field
        self.formatter = formatter or noop
        self.model = model