import base64
import itertools
import logging
import os
from datetime import datetime
from enum import Enum
from pathlib import Path
from typing import Dict, Iterable, List

import tomlkit

from feeluown.consts import COLLECTIONS_DIR
from feeluown.utils.dispatch import Signal
from feeluown.models.uri import resolve, reverse, ResolverNotFound, \
    ResolveFailed, ModelExistence
from feeluown.utils.utils import elfhash

logger = logging.getLogger(__name__)

COLL_LIBRARY_IDENTIFIER = 'library'
COLL_POOL_IDENTIFIER = 'pool'
# for backward compat, we should never change these filenames
LIBRARY_FILENAME = f'{COLL_LIBRARY_IDENTIFIER}.fuo'
POOL_FILENAME = f'{COLL_POOL_IDENTIFIER}.fuo'
DEPRECATED_FUO_FILENAMES = (
    'Songs.fuo', 'Albums.fuo', 'Artists.fuo', 'Videos.fuo'
)

TOML_DELIMLF = "+++\n"


class CollectionAlreadyExists(Exception):
    pass


class CollectionType(Enum):
    sys_library = 16
    sys_pool = 13

    mixed = 8


class Collection:

    def __init__(self, fpath):
        # TODO: 以后考虑添加 identifier 字段，identifier
        # 字段应该尽量设计成可以跨电脑使用
        self.fpath = str(fpath)
        # TODO: 目前还没想好 collection identifier 计算方法，故添加这个函数
        # 现在把 fpath 当作 identifier 使用，但对外透明
        self.identifier = elfhash(base64.b64encode(bytes(self.fpath, 'utf-8')))

        # these variables should be inited during loading
        self.type = None
        self.name = None  # Collection title.
        self.models = []
        self.updated_at = None
        self.created_at = None
        self.description = None
        self._has_nonexistent_models = False

        #: tomkit.toml_document.Document
        self._metadata = None

    def load(self):
        """解析文件，初始化自己"""
        # pylint: disable=too-many-branches
        self.models = []
        filepath = Path(self.fpath)
        name = filepath.stem
        stat_result = filepath.stat()
        self.updated_at = datetime.fromtimestamp(stat_result.st_mtime)
        self.name = name
        if name == COLL_LIBRARY_IDENTIFIER:
            self.type = CollectionType.sys_library
        elif name == COLL_POOL_IDENTIFIER:
            self.type = CollectionType.sys_pool
        else:
            self.type = CollectionType.mixed

        # parse file content
        with filepath.open(encoding='utf-8') as f:
            first = f.readline()
            lines = []
            if first == TOML_DELIMLF:
                is_valid = False
                for line in f:
                    if line == TOML_DELIMLF:
                        is_valid = True
                        break
                    lines.append(line)
                if is_valid is True:
                    toml_str = ''.join(lines)
                    metadata = tomlkit.parse(toml_str)
                    self._loads_metadata(metadata)
                    lines = []
                else:
                    logger.warning('the metadata is invalid, will ignore it')
            else:
                lines.append(first)

            for line in itertools.chain(lines, f):
                if not line.strip():  # ignore empty lines
                    continue
                try:
                    model = resolve(line)
                except ResolverNotFound:
                    logger.warning('resolver not found for line:%s', line)
                    model = None
                except ResolveFailed as e:
                    logger.warning('resolve failed, file:%s, line:%s, error:%s',
                                   str(filepath), line, str(e))
                    model = None
                if model is not None:
                    if model.exists is ModelExistence.no:
                        self._has_nonexistent_models = True
                    self.models.append(model)

    @classmethod
    def create_empty(cls, fpath, title=''):
        """Create an empty collection."""
        if os.path.exists(fpath):
            raise CollectionAlreadyExists()

        doc = tomlkit.document()
        if title:
            doc.add('title', title)
        doc.add('created', datetime.now())
        doc.add('updated', datetime.now())
        with open(fpath, 'w', encoding='utf-8') as f:
            f.write(TOML_DELIMLF)
            f.write(tomlkit.dumps(doc))
            f.write(TOML_DELIMLF)

        coll = cls(fpath)
        coll._loads_metadata(doc)
        coll.type = CollectionType.mixed
        return coll

    def add(self, model):
        """add model to collection

        :param model: :class:`feeluown.models.BaseModel`
        :return: True means succeed, False means failed
        """
        if model not in self.models:
            line = reverse(model, as_line=True)
            with open(self.fpath, 'r+', encoding='utf-8') as f:
                content = f.read()
                parts = content.split(TOML_DELIMLF, maxsplit=2)
                body = parts[-1]
                f.seek(0, 0)
                self._write_metadata_if_needed(f)
                f.write(f'{line}\n{body}')
                f.truncate()
            self.models.insert(0, model)
        return True

    def remove(self, model):
        if model in self.models:
            url = reverse(model)
            with open(self.fpath, 'r+', encoding='utf-8') as f:
                content = f.read()
                parts = content.split(TOML_DELIMLF, maxsplit=2)
                body = parts[-1]
                lines = []
                for line in body.split('\n'):
                    if line.startswith(url):
                        continue
                    if line:
                        lines.append(line)

                f.seek(0)
                self._write_metadata_if_needed(f)
                f.write('\n'.join(lines))
                f.truncate()
                # 确保最后写入一个换行符，让文件更加美观
                if lines and not lines[-1].endswith('\n'):
                    f.write('\n')
            self.models.remove(model)
        return True

    def on_provider_added(self, provider):
        if not self._has_nonexistent_models:
            return
        for i, model in enumerate(self.models.copy()):
            if model.exists is ModelExistence.no and model.source == provider.identifier:
                new_model = resolve(reverse(model, as_line=True))
                # TODO: emit data changed signal
                self.models[i] = new_model
        # TODO: set _has_nonexistent_models to proper value

    def on_provider_removed(self, provider):
        for model in self.models:
            if model.source == provider.identifier:
                model.exists = ModelExistence.no
                self._has_nonexistent_models = True

    def _loads_metadata(self, metadata):
        self._metadata = metadata
        self.created_at = metadata.get('created')
        self.updated_at = metadata.get('updated', self.updated_at)
        self.name = metadata.get('title', self.name)
        self.description = metadata.get('description')

    def _write_metadata_if_needed(self, f):
        # write metadata only if it had before
        if self._metadata:
            self.updated_at = self._metadata['updated'] = datetime.now()
            s = tomlkit.dumps(self._metadata)
            f.write(TOML_DELIMLF)
            f.write(s)
            if not s.endswith('\n'):
                f.write('\n')
            f.write(TOML_DELIMLF)


class CollectionManager:

    def __init__(self, app):
        self._app = app
        self.scan_finished = Signal()
        self._library = app.library
        self.default_dir = COLLECTIONS_DIR

        self._id_coll_mapping: Dict[int, Collection] = {}
        self._sys_colls = {}

    def get(self, identifier):
        if identifier in (CollectionType.sys_pool, CollectionType.sys_library):
            return self._sys_colls[identifier]
        return self._id_coll_mapping[int(identifier)]

    def get_coll_library(self):
        for coll in self._id_coll_mapping.values():
            if coll.type == CollectionType.sys_library:
                return coll
        assert False, "collection 'library' must exists."

    def create(self, fname, title) -> Collection:
        first_valid_dir = ''
        for d, exists in self._get_dirs():
            if exists:
                first_valid_dir = d
                break

        assert first_valid_dir, 'there must be a valid collection dir'
        normalized_name = fname.replace(' ', '_')
        fpath = os.path.join(first_valid_dir, normalized_name)
        filepath = f'{fpath}.fuo'
        logger.info(f'Create collection:{title} at {filepath}')
        return Collection.create_empty(filepath, title)

    def remove(self, collection: Collection):
        coll_id = collection.identifier
        if coll_id in self._id_coll_mapping:
            self._id_coll_mapping.pop(coll_id)
            os.remove(collection.fpath)

    def _get_dirs(self, ):
        directorys = [self.default_dir]
        if self._app.config.COLLECTIONS_DIR:
            if isinstance(self._app.config.COLLECTIONS_DIR, list):
                directorys += self._app.config.COLLECTIONS_DIR
            else:
                directorys.append(self._app.config.COLLECTIONS_DIR)
        expanded_dirs = []
        for directory in directorys:
            directory = os.path.expanduser(directory)
            expanded_dirs.append((directory, os.path.exists(directory)))
        return expanded_dirs

    def scan(self):
        colls: List[Collection] = []
        for coll in self._scan():
            if coll.type == CollectionType.sys_library:
                self._sys_colls[CollectionType.sys_library] = coll
            elif coll.type == CollectionType.sys_pool:
                self._sys_colls[CollectionType.sys_pool] = coll
            else:
                colls.append(coll)

        if CollectionType.sys_pool not in self._sys_colls:
            pool_fpath = os.path.join(self.default_dir, POOL_FILENAME)
            assert not os.path.exists(pool_fpath)
            logger.info('Generating collection pool.')
            coll = Collection.create_empty(pool_fpath, '想听')
            self._sys_colls[CollectionType.sys_pool] = coll

        pool_coll = self._sys_colls[CollectionType.sys_pool]
        library_coll = self._sys_colls[CollectionType.sys_library]
        colls.insert(0, pool_coll)
        colls.insert(0, library_coll)
        for collection in colls:
            coll_id = collection.identifier
            assert coll_id not in self._id_coll_mapping, collection.fpath
            self._id_coll_mapping[coll_id] = collection
        self.scan_finished.emit()

    def refresh(self):
        self.clear()
        self.scan()

    def listall(self):
        return self._id_coll_mapping.values()

    def clear(self):
        self._id_coll_mapping.clear()

    def _scan(self) -> Iterable[Collection]:
        """Scan collections directories for valid fuo files, yield
        Collection instance for each file.
        """
        default_fpaths = []
        valid_dirs = self._get_dirs()
        for directory, exists in valid_dirs:
            if not exists:
                logger.warning('Collection directory %s does not exist', directory)
                continue
            for filename in os.listdir(directory):
                if not filename.endswith('.fuo'):
                    continue
                filepath = os.path.join(directory, filename)
                if filename in DEPRECATED_FUO_FILENAMES:
                    default_fpaths.append(filepath)
                    continue
                coll = Collection(filepath)
                coll.load()
                self._app.library.provider_added.connect(coll.on_provider_added)
                self._app.library.provider_removed.connect(coll.on_provider_removed)
                yield coll

        fpath, generated = self.generate_library_coll_if_needed(default_fpaths)
        # Avoid to yield a duplicated collection.
        if generated is True:
            coll = Collection(fpath)
            coll.load()
            self._app.library.provider_added.connect(coll.on_provider_added)
            self._app.library.provider_removed.connect(coll.on_provider_removed)
            yield coll

    def generate_library_coll_if_needed(self, default_fpaths):
        """
        :return: (library file path, generated)
        """
        library_fpath = os.path.join(self.default_dir, LIBRARY_FILENAME)
        if os.path.exists(library_fpath):
            if default_fpaths:
                paths_str = ','.join(default_fpaths)
                logger.warning(f'{paths_str} are ignored since {library_fpath} exists')
            return library_fpath, False

        logger.info('Generating collection library')
        lines = [TOML_DELIMLF,
                 'title = "Library"',
                 TOML_DELIMLF]
        if default_fpaths:
            for fpath in default_fpaths:
                with open(fpath, 'r', encoding='utf-8') as f:
                    for line in f:
                        if line.startswith('fuo://'):
                            lines.append(line)
        with open(library_fpath, 'w', encoding='utf-8') as f:
            f.write('\n'.join(lines))

        # backup old sys collections if they exists
        for fpath in default_fpaths:
            dirname = os.path.dirname(fpath)
            filename = os.path.basename(fpath)
            filename += '.bak'
            new_fpath = os.path.join(dirname, filename)
            logger.info(f'Rename {fpath} to {new_fpath}')
            os.rename(fpath, new_fpath)
        return library_fpath, True
