# Created By: Virgil Dupras
# Created On: 2009-10-22
# Copyright 2015 Hardcoded Software (http://www.hardcoded.net)
#
# This software is licensed under the "GPLv3" License as described in the "LICENSE" file,
# which should be included with this package. The terms are also available at
# http://www.gnu.org/licenses/gpl-3.0.html

# This is a fork from hsfs. The reason for this fork is that hsfs has been designed for musicGuru
# and was re-used for dupeGuru. The problem is that hsfs is way over-engineered for dupeGuru,
# resulting needless complexity and memory usage. It's been a while since I wanted to do that fork,
# and I'm doing it now.

import hashlib
from math import floor
import logging
import sqlite3
from threading import Lock
from typing import Any

from hscommon.path import Path
from hscommon.util import nonone, get_file_ext

__all__ = [
    "File",
    "Folder",
    "get_file",
    "get_files",
    "FSError",
    "AlreadyExistsError",
    "InvalidPath",
    "InvalidDestinationError",
    "OperationError",
]

NOT_SET = object()

# The goal here is to not run out of memory on really big files. However, the chunk
# size has to be large enough so that the python loop isn't too costly in terms of
# CPU.
CHUNK_SIZE = 1024 * 1024  # 1 MiB

# Minimum size below which partial hashes don't need to be computed
MIN_FILE_SIZE = 3 * CHUNK_SIZE  # 3MiB, because we take 3 samples


class FSError(Exception):
    cls_message = "An error has occured on '{name}' in '{parent}'"

    def __init__(self, fsobject, parent=None):
        message = self.cls_message
        if isinstance(fsobject, str):
            name = fsobject
        elif isinstance(fsobject, File):
            name = fsobject.name
        else:
            name = ""
        parentname = str(parent) if parent is not None else ""
        Exception.__init__(self, message.format(name=name, parent=parentname))


class AlreadyExistsError(FSError):
    "The directory or file name we're trying to add already exists"
    cls_message = "'{name}' already exists in '{parent}'"


class InvalidPath(FSError):
    "The path of self is invalid, and cannot be worked with."
    cls_message = "'{name}' is invalid."


class InvalidDestinationError(FSError):
    """A copy/move operation has been called, but the destination is invalid."""

    cls_message = "'{name}' is an invalid destination for this operation."


class OperationError(FSError):
    """A copy/move/delete operation has been called, but the checkup after the
    operation shows that it didn't work."""

    cls_message = "Operation on '{name}' failed."


class FilesDB:

    create_table_query = "CREATE TABLE IF NOT EXISTS files (path TEXT PRIMARY KEY, size INTEGER, mtime_ns INTEGER, entry_dt DATETIME, md5 BLOB, md5partial BLOB)"
    drop_table_query = "DROP TABLE files;"
    select_query = "SELECT {key} FROM files WHERE path=:path AND size=:size and mtime_ns=:mtime_ns"
    insert_query = """
        INSERT INTO files (path, size, mtime_ns, entry_dt, {key}) VALUES (:path, :size, :mtime_ns, datetime('now'), :value)
        ON CONFLICT(path) DO UPDATE SET size=:size, mtime_ns=:mtime_ns, entry_dt=datetime('now'), {key}=:value;
    """

    def __init__(self):
        self.conn = None
        self.cur = None
        self.lock = None

    def connect(self, path):
        # type: (str, ) -> None

        self.conn = sqlite3.connect(path, check_same_thread=False)
        self.cur = self.conn.cursor()
        self.cur.execute(self.create_table_query)
        self.lock = Lock()

    def clear(self):
        # type: () -> None

        with self.lock:
            self.cur.execute(self.drop_table_query)
            self.cur.execute(self.create_table_query)

    def get(self, path, key):
        # type: (Path, str) -> bytes

        stat = path.stat()
        size = stat.st_size
        mtime_ns = stat.st_mtime_ns

        with self.lock:
            self.cur.execute(self.select_query.format(key=key), {"path": str(path), "size": size, "mtime_ns": mtime_ns})
            result = self.cur.fetchone()

        if result:
            return result[0]

        return None

    def put(self, path, key, value):
        # type: (Path, str, Any) -> None

        stat = path.stat()
        size = stat.st_size
        mtime_ns = stat.st_mtime_ns

        with self.lock:
            self.cur.execute(
                self.insert_query.format(key=key),
                {"path": str(path), "size": size, "mtime_ns": mtime_ns, "value": value},
            )

    def commit(self):
        # type: () -> None

        with self.lock:
            self.conn.commit()

    def close(self):
        # type: () -> None

        with self.lock:
            self.cur.close()
            self.conn.close()


filesdb = FilesDB()  # Singleton


class File:
    """Represents a file and holds metadata to be used for scanning."""

    INITIAL_INFO = {"size": 0, "mtime": 0, "md5": b"", "md5partial": b"", "md5samples": b""}
    # Slots for File make us save quite a bit of memory. In a memory test I've made with a lot of
    # files, I saved 35% memory usage with "unread" files (no _read_info() call) and gains become
    # even greater when we take into account read attributes (70%!). Yeah, it's worth it.
    __slots__ = ("path", "is_ref", "words") + tuple(INITIAL_INFO.keys())

    def __init__(self, path):
        self.path = path
        for attrname in self.INITIAL_INFO:
            setattr(self, attrname, NOT_SET)

    def __repr__(self):
        return "<{} {}>".format(self.__class__.__name__, str(self.path))

    def __getattribute__(self, attrname):
        result = object.__getattribute__(self, attrname)
        if result is NOT_SET:
            try:
                self._read_info(attrname)
            except Exception as e:
                logging.warning("An error '%s' was raised while decoding '%s'", e, repr(self.path))
            result = object.__getattribute__(self, attrname)
            if result is NOT_SET:
                result = self.INITIAL_INFO[attrname]
        return result

    def _calc_md5(self):
        # type: () -> bytes

        with self.path.open("rb") as fp:
            md5 = hashlib.md5()
            # The goal here is to not run out of memory on really big files. However, the chunk
            # size has to be large enough so that the python loop isn't too costly in terms of
            # CPU.
            CHUNK_SIZE = 1024 * 1024  # 1 mb
            filedata = fp.read(CHUNK_SIZE)
            while filedata:
                md5.update(filedata)
                filedata = fp.read(CHUNK_SIZE)
            return md5.digest()

    def _calc_md5partial(self):
        # type: () -> bytes

        # This offset is where we should start reading the file to get a partial md5
        # For audio file, it should be where audio data starts
        offset, size = (0x4000, 0x4000)

        with self.path.open("rb") as fp:
            fp.seek(offset)
            partialdata = fp.read(size)
            return hashlib.md5(partialdata).digest()

    def _read_info(self, field):
        # print(f"_read_info({field}) for {self}")
        if field in ("size", "mtime"):
            stats = self.path.stat()
            self.size = nonone(stats.st_size, 0)
            self.mtime = nonone(stats.st_mtime, 0)
        elif field == "md5partial":
            try:
                self.md5partial = filesdb.get(self.path, "md5partial")
                if self.md5partial is None:
                    self.md5partial = self._calc_md5partial()
                    filesdb.put(self.path, "md5partial", self.md5partial)
            except Exception as e:
                logging.warning("Couldn't get md5partial for %s: %s", self.path, e)
        elif field == "md5":
            try:
                self.md5 = filesdb.get(self.path, "md5")
                if self.md5 is None:
                    self.md5 = self._calc_md5()
                    filesdb.put(self.path, "md5", self.md5)
            except Exception as e:
                logging.warning("Couldn't get md5 for %s: %s", self.path, e)
        elif field == "md5samples":
            try:
                with self.path.open("rb") as fp:
                    size = self.size
                    # Might as well hash such small files entirely.
                    if size <= MIN_FILE_SIZE:
                        setattr(self, field, self.md5)
                        return

                    # Chunk at 25% of the file
                    fp.seek(floor(size * 25 / 100), 0)
                    filedata = fp.read(CHUNK_SIZE)
                    md5 = hashlib.md5(filedata)

                    # Chunk at 60% of the file
                    fp.seek(floor(size * 60 / 100), 0)
                    filedata = fp.read(CHUNK_SIZE)
                    md5.update(filedata)

                    # Last chunk of the file
                    fp.seek(-CHUNK_SIZE, 2)
                    filedata = fp.read(CHUNK_SIZE)
                    md5.update(filedata)
                    setattr(self, field, md5.digest())
            except Exception as e:
                logging.error(f"Error computing md5samples: {e}")

    def _read_all_info(self, attrnames=None):
        """Cache all possible info.

        If `attrnames` is not None, caches only attrnames.
        """
        if attrnames is None:
            attrnames = self.INITIAL_INFO.keys()
        for attrname in attrnames:
            getattr(self, attrname)

    # --- Public
    @classmethod
    def can_handle(cls, path):
        """Returns whether this file wrapper class can handle ``path``."""
        return not path.islink() and path.isfile()

    def rename(self, newname):
        if newname == self.name:
            return
        destpath = self.path.parent()[newname]
        if destpath.exists():
            raise AlreadyExistsError(newname, self.path.parent())
        try:
            self.path.rename(destpath)
        except EnvironmentError:
            raise OperationError(self)
        if not destpath.exists():
            raise OperationError(self)
        self.path = destpath

    def get_display_info(self, group, delta):
        """Returns a display-ready dict of dupe's data."""
        raise NotImplementedError()

    # --- Properties
    @property
    def extension(self):
        return get_file_ext(self.name)

    @property
    def name(self):
        return self.path.name

    @property
    def folder_path(self):
        return self.path.parent()


class Folder(File):
    """A wrapper around a folder path.

    It has the size/md5 info of a File, but its value is the sum of its subitems.
    """

    __slots__ = File.__slots__ + ("_subfolders",)

    def __init__(self, path):
        File.__init__(self, path)
        self._subfolders = None

    def _all_items(self):
        folders = self.subfolders
        files = get_files(self.path)
        return folders + files

    def _read_info(self, field):
        # print(f"_read_info({field}) for Folder {self}")
        if field in {"size", "mtime"}:
            size = sum((f.size for f in self._all_items()), 0)
            self.size = size
            stats = self.path.stat()
            self.mtime = nonone(stats.st_mtime, 0)
        elif field in {"md5", "md5partial", "md5samples"}:
            # What's sensitive here is that we must make sure that subfiles'
            # md5 are always added up in the same order, but we also want a
            # different md5 if a file gets moved in a different subdirectory.

            def get_dir_md5_concat():
                items = self._all_items()
                items.sort(key=lambda f: f.path)
                md5s = [getattr(f, field) for f in items]
                return b"".join(md5s)

            md5 = hashlib.md5(get_dir_md5_concat())
            digest = md5.digest()
            setattr(self, field, digest)

    @property
    def subfolders(self):
        if self._subfolders is None:
            subfolders = [p for p in self.path.listdir() if not p.islink() and p.isdir()]
            self._subfolders = [self.__class__(p) for p in subfolders]
        return self._subfolders

    @classmethod
    def can_handle(cls, path):
        return not path.islink() and path.isdir()


def get_file(path, fileclasses=[File]):
    """Wraps ``path`` around its appropriate :class:`File` class.

    Whether a class is "appropriate" is decided by :meth:`File.can_handle`

    :param Path path: path to wrap
    :param fileclasses: List of candidate :class:`File` classes
    """
    for fileclass in fileclasses:
        if fileclass.can_handle(path):
            return fileclass(path)


def get_files(path, fileclasses=[File]):
    """Returns a list of :class:`File` for each file contained in ``path``.

    :param Path path: path to scan
    :param fileclasses: List of candidate :class:`File` classes
    """
    assert all(issubclass(fileclass, File) for fileclass in fileclasses)
    try:
        result = []
        for path in path.listdir():
            file = get_file(path, fileclasses=fileclasses)
            if file is not None:
                result.append(file)
        return result
    except EnvironmentError:
        raise InvalidPath(path)