#!/usr/bin/env python3

import hashlib
import os
from typing import Any, Optional


class DirectoryFileFilter(object):
    """A predicate that will return False if when a proposed file's
    content to-be-written is identical to the contents of the file;
    skip the write.
    """

    def __init__(self, directory: str):
        import file_utils
        super().__init__()
        if not file_utils.does_directory_exist(directory):
            raise ValueError(directory)
        self.directory = directory
        self.md5_by_filename = {}
        self.mtime_by_filename = {}
        self._update()

    def _update(self):
        for direntry in os.scandir(self.directory):
            if direntry.is_file(follow_symlinks=True):
                mtime = direntry.stat(follow_symlinks=True).st_mtime
                path = f'{self.directory}/{direntry.name}'
                self._update_file(path, mtime)

    def _update_file(self, filename: str, mtime: Optional[float] = None):
        import file_utils
        assert file_utils.does_file_exist(filename)
        if mtime is None:
            mtime = file_utils.get_file_raw_mtime(filename)
        if self.mtime_by_filename.get(filename, 0) != mtime:
            md5 = file_utils.get_file_md5(filename)
            self.mtime_by_filename[filename] = mtime
            self.md5_by_filename[filename] = md5

    def apply(self, item: Any, filename: str) -> bool:
        self._update_file(filename)
        file_md5 = self.md5_by_filename.get(filename, 0)
        mem_hash = hashlib.md5()
        mem_hash.update(item)
        md5 = mem_hash.hexdigest()
        return md5 != file_md5


class DirectoryAllFilesFilter(DirectoryFileFilter):
    """A predicate that will return False if a file to-be-written to a
    particular directory is identical to any other file in that same
    directory.
    """

    def __init__(self, directory: str):
        self.all_md5s = set()
        super().__init__(directory)
        print(self.all_md5s)

    def _update_file(self, filename: str, mtime: Optional[float] = None):
        import file_utils
        assert file_utils.does_file_exist(filename)
        if mtime is None:
            mtime = file_utils.get_file_raw_mtime(filename)
        if self.mtime_by_filename.get(filename, 0) != mtime:
            md5 = file_utils.get_file_md5(filename)
            self.mtime_by_filename[filename] = mtime
            self.md5_by_filename[filename] = md5
            self.all_md5s.add(md5)

    def apply(self, item: Any) -> bool:
        self._update()
        mem_hash = hashlib.md5()
        mem_hash.update(item)
        md5 = mem_hash.hexdigest()
        return md5 not in self.all_md5s