moment/src/backend/media_cache.py

import asyncio
import functools
import io
import re
import shutil
import sys
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, DefaultDict, Dict, Optional
from urllib.parse import urlparse

import aiofiles
from PIL import Image as PILImage

import nio

from .backend import Backend
from .utils import Size

if sys.version_info < (3, 8):
    import pyfastcopy  # noqa

CryptDict = Optional[Dict[str, Any]]

CONCURRENT_DOWNLOADS_LIMIT                   = asyncio.BoundedSemaphore(8)
ACCESS_LOCKS: DefaultDict[str, asyncio.Lock] = DefaultDict(asyncio.Lock)


@dataclass
class Media:
    cache:      "MediaCache" = field()
    mxc:        str          = field()
    crypt_dict: CryptDict    = field(repr=False)


    def __post_init__(self) -> None:
        self.mxc = re.sub(r"#auto$", "", self.mxc)

        if not re.match(r"^mxc://.+/.+", self.mxc):
            raise ValueError(f"Invalid mxc URI: {self.mxc}")


    @property
    def local_path(self) -> Path:
        parsed = urlparse(self.mxc)
        name   = parsed.path.lstrip("/")
        return self.cache.downloads_dir / parsed.netloc / name


    async def get(self) -> Path:
        async with ACCESS_LOCKS[self.mxc]:
            try:
                return await self._get_local_existing_file()
            except FileNotFoundError:
                return await self.create()


    async def _get_local_existing_file(self) -> Path:
        if not self.local_path.exists():
            raise FileNotFoundError()

        return self.local_path


    async def create(self) -> Path:
        async with CONCURRENT_DOWNLOADS_LIMIT:
            data = await self._get_remote_data()

        self.local_path.parent.mkdir(parents=True, exist_ok=True)

        async with aiofiles.open(self.local_path, "wb") as file:
            await file.write(data)

        return self.local_path


    async def _get_remote_data(self) -> bytes:
        parsed = urlparse(self.mxc)

        resp = await self.cache.backend.download(
            server_name = parsed.netloc,
            media_id    = parsed.path.lstrip("/"),
        )

        return await self._decrypt(resp.body)


    async def _decrypt(self, data: bytes) -> bytes:
        if not self.crypt_dict:
            return data

        func = functools.partial(
            nio.crypto.attachments.decrypt_attachment,
            data,
            self.crypt_dict["key"]["k"],
            self.crypt_dict["hashes"]["sha256"],
            self.crypt_dict["iv"],
        )

        # Run in a separate thread
        return await asyncio.get_event_loop().run_in_executor(None, func)


    @classmethod
    async def from_existing_file(
        cls,
        cache:     "MediaCache",
        mxc:       str,
        existing:  Path,
        overwrite: bool = False,
        **kwargs,
    ) -> "Media":

        media = cls(cache, mxc, {}, **kwargs)  # type: ignore
        media.local_path.parent.mkdir(parents=True, exist_ok=True)

        if not media.local_path.exists() or overwrite:
            func = functools.partial(shutil.copy, existing, media.local_path)
            await asyncio.get_event_loop().run_in_executor(None, func)

        return media


    @classmethod
    async def from_bytes(
        cls,
        cache:     "MediaCache",
        mxc:       str,
        data:      bytes,
        overwrite: bool = False,
        **kwargs,
    ) -> "Media":

        media = cls(cache, mxc, {}, **kwargs)  # type: ignore
        media.local_path.parent.mkdir(parents=True, exist_ok=True)

        if not media.local_path.exists() or overwrite:
            async with aiofiles.open(media.local_path, "wb") as file:
                await file.write(data)

        return media


@dataclass
class Thumbnail(Media):
    cache:       "MediaCache" = field()
    mxc:         str          = field()
    crypt_dict:  CryptDict    = field(repr=False)
    wanted_size: Size         = field()

    server_size: Optional[Size] = field(init=False, repr=False, default=None)


    @staticmethod
    def normalize_size(size: Size) -> Size:
        # https://matrix.org/docs/spec/client_server/latest#thumbnails

        if size[0] > 640 or size[1] > 480:
            return (800, 600)

        if size[0] > 320 or size[1] > 240:
            return (640, 480)

        if size[0] > 96 or size[1] > 96:
            return (320, 240)

        if size[0] > 32 or size[1] > 32:
            return (96, 96)

        return (32, 32)


    @property
    def local_path(self) -> Path:
        # example: thumbnails/matrix.org/32x32/<mxc id>

        parsed = urlparse(self.mxc)
        size   = self.normalize_size(self.server_size or self.wanted_size)
        name   = "%dx%d/%s" % (size[0], size[1], parsed.path.lstrip("/"))

        return self.cache.thumbs_dir / parsed.netloc / name


    async def _get_local_existing_file(self) -> Path:
        if self.local_path.exists():
            return self.local_path

        # If we have a bigger size thumbnail than the wanted_size for this pic,
        # return it instead of asking the server for a smaller thumbnail.

        try_sizes = ((32, 32), (96, 96), (320, 240), (640, 480), (800, 600))
        parts     = list(self.local_path.parts)
        size      = self.normalize_size(self.server_size or self.wanted_size)

        for width, height in try_sizes:
            if width < size[0] or height < size[1]:
                continue

            parts[-2] = f"{width}x{height}"
            path      = Path("/".join(parts))

            if path.exists():
                return path

        raise FileNotFoundError()


    async def _get_remote_data(self) -> bytes:
        parsed = urlparse(self.mxc)

        if self.crypt_dict:
            # Matrix makes encrypted thumbs only available through the download
            # end-point, not the thumbnail one
            resp = await self.cache.backend.download(
                server_name = parsed.netloc,
                media_id    = parsed.path.lstrip("/"),
            )
        else:
            resp = await self.cache.backend.thumbnail(
                server_name = parsed.netloc,
                media_id    = parsed.path.lstrip("/"),
                width       = self.wanted_size[0],
                height      = self.wanted_size[1],
            )

        decrypted = await self._decrypt(resp.body)

        with io.BytesIO(decrypted) as img:
            # The server may return a thumbnail bigger than what we asked for
            self.server_size = PILImage.open(img).size

        return decrypted


@dataclass
class MediaCache:
    backend:  Backend = field()
    base_dir: Path    = field()


    def __post_init__(self) -> None:
        self.thumbs_dir    = self.base_dir / "thumbnails"
        self.downloads_dir = self.base_dir / "downloads"

        self.thumbs_dir.mkdir(parents=True, exist_ok=True)
        self.downloads_dir.mkdir(parents=True, exist_ok=True)


    # These methods are for conveniant usage from QML

    async def get_media(self, mxc: str, crypt_dict: CryptDict = None) -> Path:
        return await Media(self, mxc, crypt_dict).get()


    async def get_thumbnail(
        self, mxc: str, width: int, height: int, crypt_dict: CryptDict = None,
    ) -> Path:

        thumb = Thumbnail(
            # QML sometimes pass float sizes, which matrix API doesn't like.
            self, mxc, crypt_dict, (round(width), round(height)),
        )
        return await thumb.get()