Implement support for .avi files, via ffmpeg

- This commit introduces optional dependencies (namely ffmpeg):
  mat2 will spit a warning when trying to process an .avi file
  if ffmpeg isn't installed.
- Since metadata are obtained via exiftool, this commit
  also refactors a bit our exfitool wrapper.

6 files changed, 134 insertions, 56 deletions

diff --git a/libmat2/__init__.py b/libmat2/__init__.py
index f55a14c..399a364 100644
--- a/libmat2/__init__.py
+++ b/libmat2/__init__.py
@@ -1,11 +1,12 @@
 #!/usr/bin/env python3
 
-import os
 import collections
 import enum
 import importlib
 from typing import Dict, Optional
 
+from . import exiftool, video
+
 # make pyflakes happy
 assert Dict
 assert Optional
@@ -37,24 +38,13 @@ DEPENDENCIES = {
     'mutagen': 'Mutagen',
     }
 
-def _get_exiftool_path() -> str:  # pragma: no cover
-    exiftool_path = '/usr/bin/exiftool'
-    if os.path.isfile(exiftool_path):
-        if os.access(exiftool_path, os.X_OK):
-            return exiftool_path
-
-    # ArchLinux
-    exiftool_path = '/usr/bin/vendor_perl/exiftool'
-    if os.path.isfile(exiftool_path):
-        if os.access(exiftool_path, os.X_OK):
-            return exiftool_path
 
-    raise ValueError
 
 def check_dependencies() -> dict:
     ret = collections.defaultdict(bool)  # type: Dict[str, bool]
 
-    ret['Exiftool'] = True if _get_exiftool_path() else False
+    ret['Exiftool'] = True if exiftool._get_exiftool_path() else False
+    ret['Ffmpeg'] = True if video._get_ffmpeg_path() else False
 
     for key, value in DEPENDENCIES.items():
         ret[value] = True
diff --git a/libmat2/abstract.py b/libmat2/abstract.py
index 0084796..414a68b 100644
--- a/libmat2/abstract.py
+++ b/libmat2/abstract.py
@@ -7,7 +7,8 @@ assert Set  # make pyflakes happy
 
 class AbstractParser(abc.ABC):
     """ This is the base class of every parser.
-    It might yield `ValueError` on instantiation on invalid files.
+    It might yield `ValueError` on instantiation on invalid files,
+    and `RuntimeError` when something went wrong in `remove_all`.
     """
     meta_list = set()  # type: Set[str]
     mimetypes = set()  # type: Set[str]
@@ -27,4 +28,7 @@ class AbstractParser(abc.ABC):
 
     @abc.abstractmethod
     def remove_all(self) -> bool:
+        """
+        :raises RuntimeError: Raised if the cleaning process went wrong.
+        """
         pass  # pragma: no cover
diff --git a/libmat2/exiftool.py b/libmat2/exiftool.py
new file mode 100644
index 0000000..e17d31b
--- /dev/null
+++ b/libmat2/exiftool.py
@@ -0,0 +1,61 @@
+import json
+import os
+import re
+import shutil
+import subprocess
+import tempfile
+
+from typing import Dict, Union, Set
+
+from . import abstract
+
+# Make pyflakes happy
+assert Set
+
+
+class ExiftoolParser(abstract.AbstractParser):
+    """ Exiftool is often the easiest way to get all the metadata
+    from a import file, hence why several parsers are re-using its `get_meta`
+    method.
+    """
+    meta_whitelist = set()  # type: Set[str]
+
+    @staticmethod
+    def __handle_problematic_filename(filename: str, callback) -> bytes:
+        """ This method takes a filename with a problematic name,
+        and safely applies it a `callback`."""
+        tmpdirname = tempfile.mkdtemp()
+        fname = os.path.join(tmpdirname, "temp_file")
+        shutil.copy(filename, fname)
+        out = callback(fname)
+        shutil.rmtree(tmpdirname)
+        return out
+
+    def get_meta(self) -> Dict[str, Union[str, dict]]:
+        """ There is no way to escape the leading(s) dash(es) of the current
+        self.filename to prevent parameter injections, so we need to take care
+        of this.
+        """
+        fun = lambda f: subprocess.check_output([_get_exiftool_path(), '-json', f])
+        if re.search('^[a-z0-9/]', self.filename) is None:
+            out = self.__handle_problematic_filename(self.filename, fun)
+        else:
+            out = fun(self.filename)
+        meta = json.loads(out.decode('utf-8'))[0]
+        for key in self.meta_whitelist:
+            meta.pop(key, None)
+        return meta
+
+def _get_exiftool_path() -> str:  # pragma: no cover
+    exiftool_path = '/usr/bin/exiftool'
+    if os.path.isfile(exiftool_path):
+        if os.access(exiftool_path, os.X_OK):
+            return exiftool_path
+
+    # ArchLinux
+    exiftool_path = '/usr/bin/vendor_perl/exiftool'
+    if os.path.isfile(exiftool_path):
+        if os.access(exiftool_path, os.X_OK):
+            return exiftool_path
+
+    raise RuntimeError("Unable to find exiftool")
diff --git a/libmat2/images.py b/libmat2/images.py
index a29cbb7..ad80892 100644
--- a/libmat2/images.py
+++ b/libmat2/images.py
@@ -1,11 +1,6 @@
-import subprocess
 import imghdr
-import json
 import os
-import shutil
-import tempfile
-import re
-from typing import Set, Dict, Union
+from typing import Set
 
 import cairo
 
@@ -13,44 +8,12 @@ import gi
 gi.require_version('GdkPixbuf', '2.0')
 from gi.repository import GdkPixbuf
 
-from . import abstract, _get_exiftool_path
+from . import exiftool
 
 # Make pyflakes happy
 assert Set
 
-class _ImageParser(abstract.AbstractParser):
-    """ Since we use `exiftool` to get metadata from
-    all images fileformat, `get_meta` is implemented in this class,
-    and all the image-handling ones are inheriting from it."""
-    meta_whitelist = set()  # type: Set[str]
-
-    @staticmethod
-    def __handle_problematic_filename(filename: str, callback) -> bytes:
-        """ This method takes a filename with a problematic name,
-        and safely applies it a `callback`."""
-        tmpdirname = tempfile.mkdtemp()
-        fname = os.path.join(tmpdirname, "temp_file")
-        shutil.copy(filename, fname)
-        out = callback(fname)
-        shutil.rmtree(tmpdirname)
-        return out
-
-    def get_meta(self) -> Dict[str, Union[str, dict]]:
-        """ There is no way to escape the leading(s) dash(es) of the current
-        self.filename to prevent parameter injections, so we need to take care
-        of this.
-        """
-        fun = lambda f: subprocess.check_output([_get_exiftool_path(), '-json', f])
-        if re.search('^[a-z0-9/]', self.filename) is None:
-            out = self.__handle_problematic_filename(self.filename, fun)
-        else:
-            out = fun(self.filename)
-        meta = json.loads(out.decode('utf-8'))[0]
-        for key in self.meta_whitelist:
-            meta.pop(key, None)
-        return meta
-
-class PNGParser(_ImageParser):
+class PNGParser(exiftool.ExiftoolParser):
     mimetypes = {'image/png', }
     meta_whitelist = {'SourceFile', 'ExifToolVersion', 'FileName',
                       'Directory', 'FileSize', 'FileModifyDate',
@@ -77,7 +40,7 @@ class PNGParser(_ImageParser):
         return True
 
 
-class GdkPixbufAbstractParser(_ImageParser):
+class GdkPixbufAbstractParser(exiftool.ExiftoolParser):
     """ GdkPixbuf can handle a lot of surfaces, so we're rending images on it,
         this has the side-effect of completely removing metadata.
     """
diff --git a/libmat2/parser_factory.py b/libmat2/parser_factory.py
index 621640b..4a0ca0d 100644
--- a/libmat2/parser_factory.py
+++ b/libmat2/parser_factory.py
@@ -18,6 +18,8 @@ def __load_all_parsers():
             continue
         elif fname.endswith('__init__.py'):
             continue
+        elif fname.endswith('exiftool.py'):
+            continue
         basename = os.path.basename(fname)
         name, _ = os.path.splitext(basename)
         importlib.import_module('.' + name, package='libmat2')
diff --git a/libmat2/video.py b/libmat2/video.py
new file mode 100644
index 0000000..b9f3687
--- /dev/null
+++ b/libmat2/video.py
@@ -0,0 +1,58 @@
+import os
+import subprocess
+
+from . import exiftool
+
+
+class AVIParser(exiftool.ExiftoolParser):
+    mimetypes = {'video/x-msvideo', }
+    meta_whitelist = {'SourceFile', 'ExifToolVersion', 'FileName', 'Directory',
+                      'FileSize', 'FileModifyDate', 'FileAccessDate',
+                      'FileInodeChangeDate', 'FilePermissions', 'FileType',
+                      'FileTypeExtension', 'MIMEType', 'FrameRate', 'MaxDataRate',
+                      'FrameCount', 'StreamCount', 'StreamType', 'VideoCodec',
+                      'VideoFrameRate', 'VideoFrameCount', 'Quality',
+                      'SampleSize', 'BMPVersion', 'ImageWidth', 'ImageHeight',
+                      'Planes', 'BitDepth', 'Compression', 'ImageLength',
+                      'PixelsPerMeterX', 'PixelsPerMeterY', 'NumColors',
+                      'NumImportantColors', 'NumColors', 'NumImportantColors',
+                      'RedMask', 'GreenMask', 'BlueMask', 'AlphaMask',
+                      'ColorSpace', 'AudioCodec', 'AudioCodecRate',
+                      'AudioSampleCount', 'AudioSampleCount',
+                      'AudioSampleRate', 'Encoding', 'NumChannels',
+                      'SampleRate', 'AvgBytesPerSec', 'BitsPerSample',
+                      'Duration', 'ImageSize', 'Megapixels'}
+
+    def remove_all(self) -> bool:
+        """
+            TODO: handle problematic filenames starting with `-` and `--`,
+            check exiftool.py
+        """
+        cmd = [_get_ffmpeg_path(),
+               '-i', self.filename,      # input file
+               '-y',                     # overwrite existing output file
+               '-loglevel', 'panic',     # Don't show log
+               '-hide_banner',           # hide the banner
+               '-codec', 'copy',         # don't decode anything, just copy (speed!)
+               '-map_metadata', '-1',    # remove supperficial metadata
+               '-map_chapters', '-1',    # remove chapters
+               '-fflags', '+bitexact',   # don't add any metadata
+               '-flags:v', '+bitexact',  # don't add any metadata
+               '-flags:a', '+bitexact',  # don't add any metadata
+               self.output_filename]
+
+        try:
+            subprocess.check_call(cmd)
+        except subprocess.CalledProcessError:  # pragma: no cover
+            return False
+
+        return True
+
+
+def _get_ffmpeg_path() -> str:  # pragma: no cover
+    ffmpeg_path = '/usr/bin/ffmpeg'
+    if os.path.isfile(ffmpeg_path):
+        if os.access(ffmpeg_path, os.X_OK):
+            return ffmpeg_path
+
+    raise RuntimeError("Unable to find ffmpeg")