# 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 os

try:
    import xxhash

    hasher = xxhash.xxh128
except ImportError:
    import hashlib

    hasher = hashlib.md5

from math import floor
import logging
import sqlite3
from threading import Lock
from typing import Any, AnyStr, Union

from pathlib 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 hashing is not used
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:
    schema_version = 1
    schema_version_description = "Changed from md5 to xxhash if available."

    create_table_query = "CREATE TABLE IF NOT EXISTS files (path TEXT PRIMARY KEY, size INTEGER, mtime_ns INTEGER, entry_dt DATETIME, digest BLOB, digest_partial BLOB, digest_samples BLOB)"
    drop_table_query = "DROP TABLE IF EXISTS 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: Union[AnyStr, os.PathLike]) -> None:
        self.conn = sqlite3.connect(path, check_same_thread=False)
        self.cur = self.conn.cursor()
        self.lock = Lock()
        self._check_upgrade()

    def _check_upgrade(self) -> None:
        with self.lock:
            has_schema = self.cur.execute(
                "SELECT NAME FROM sqlite_master WHERE type='table' AND name='schema_version'"
            ).fetchall()
            version = None
            if has_schema:
                version = self.cur.execute("SELECT version FROM schema_version ORDER BY version DESC").fetchone()[0]
            else:
                self.cur.execute("CREATE TABLE schema_version (version int PRIMARY KEY, description TEXT)")
            if version != self.schema_version:
                self.cur.execute(self.drop_table_query)
                self.cur.execute(
                    "INSERT OR REPLACE INTO schema_version VALUES (:version, :description)",
                    {"version": self.schema_version, "description": self.schema_version_description},
                )
            self.cur.execute(self.create_table_query)
            self.conn.commit()

    def clear(self) -> None:
        with self.lock:
            self.cur.execute(self.drop_table_query)
            self.cur.execute(self.create_table_query)

    def get(self, path: Path, key: str) -> Union[bytes, None]:
        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: Path, key: str, value: 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) -> None:
        with self.lock:
            self.conn.commit()

    def close(self) -> 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, "digest": b"", "digest_partial": b"", "digest_samples": 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_digest(self):
        # type: () -> bytes

        with self.path.open("rb") as fp:
            file_hash = hasher()
            # 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:
                file_hash.update(filedata)
                filedata = fp.read(CHUNK_SIZE)
            return file_hash.digest()

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

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

        with self.path.open("rb") as fp:
            fp.seek(offset)
            partial_data = fp.read(size)
            return hasher(partial_data).digest()

    def _calc_digest_samples(self) -> bytes:
        size = self.size
        with self.path.open("rb") as fp:
            # Chunk at 25% of the file
            fp.seek(floor(size * 25 / 100), 0)
            file_data = fp.read(CHUNK_SIZE)
            file_hash = hasher(file_data)

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

            # Last chunk of the file
            fp.seek(-CHUNK_SIZE, 2)
            file_data = fp.read(CHUNK_SIZE)
            file_hash.update(file_data)
            return file_hash.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 == "digest_partial":
            try:
                self.digest_partial = filesdb.get(self.path, "digest_partial")
                if self.digest_partial is None:
                    self.digest_partial = self._calc_digest_partial()
                    filesdb.put(self.path, "digest_partial", self.digest_partial)
            except Exception as e:
                logging.warning("Couldn't get digest_partial for %s: %s", self.path, e)
        elif field == "digest":
            try:
                self.digest = filesdb.get(self.path, "digest")
                if self.digest is None:
                    self.digest = self._calc_digest()
                    filesdb.put(self.path, "digest", self.digest)
            except Exception as e:
                logging.warning("Couldn't get digest for %s: %s", self.path, e)
        elif field == "digest_samples":
            size = self.size
            # Might as well hash such small files entirely.
            if size <= MIN_FILE_SIZE:
                setattr(self, field, self.digest)
                return
            try:
                self.digest_samples = filesdb.get(self.path, "digest_samples")
                if self.digest_samples is None:
                    self.digest_samples = self._calc_digest_samples()
                    filesdb.put(self.path, "digest_samples", self.digest_samples)
            except Exception as e:
                logging.warning(f"Couldn't get digest_samples for {self.path}: {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.is_symlink() and path.is_file()

    def rename(self, newname):
        if newname == self.name:
            return
        destpath = self.path.parent.joinpath(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/digest 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 {"digest", "digest_partial", "digest_samples"}:
            # What's sensitive here is that we must make sure that subfiles'
            # digest are always added up in the same order, but we also want a
            # different digest if a file gets moved in a different subdirectory.

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

            digest = hasher(get_dir_digest_concat()).digest()
            setattr(self, field, digest)

    @property
    def subfolders(self):
        if self._subfolders is None:
            with os.scandir(self.path) as iter:
                subfolders = [p.path for p in iter if not p.is_symlink() and p.is_dir()]
            self._subfolders = [self.__class__(p) for p in subfolders]
        return self._subfolders

    @classmethod
    def can_handle(cls, path):
        return not path.is_symlink() and path.is_dir()


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):
            if type(path) is os.DirEntry:
                return fileclass(path.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 = []
        with os.scandir(path) as iter:
            for item in iter:
                file = get_file(item, fileclasses=fileclasses)
                if file is not None:
                    result.append(file)
        return result
    except EnvironmentError:
        raise InvalidPath(path)