import datetime
import json
import tempfile
from pathlib import Path
import re
import shutil

import pexpect

from progress_bar import ProgressBar


class ShellCommand(object):
    """A shell command.
    
    _executable contains the full path to the relevant executable.
    
    _base_options is a list of standard general options for this
    command.
    """
    _executable = ""
    _base_options = []
    _expect_patterns = []
    
    @staticmethod
    def shellquote(s):
        """Quote a string so it can be safely pasted into the shell."""
        # Files will arrive as pathlib.Path, so force everything to a
        # string before trying to do any manipulations.
        s = str(s)
        # Note: pipes/shlex.quote() only wraps '' around things,
        # it doesn't do things like \( \), which we also need.
        # We double-quote everything because that makes it easier
        # to deal with single quotes.
        if s:
            regexes = [
                # grouping parentheses for convert
                re.compile(r"^(\(|\))$"),
                # double quote (in middle of string)
                re.compile(r'^(.+".*)$'),
                # quotes around entire string
                re.compile(r"""^((?P<quote>['"]).*(?P=quote))$"""),
                # command line switch (starts with one or two "-")
                re.compile(r"^(--?.+)$"),
                # command path (starts with "/")
                re.compile(r"^(/[\w/]+)$")]
            substitutions = [r"\\\1", r"'\1'", r"\1", r"\1", r"\1"]
            num_matches = 0
            for subst in zip(regexes, substitutions):
                (s, n) = subst[0].subn(subst[1], s)
                num_matches += n
            if num_matches == 0:
                # catch-all for non-word characters when none of the other
                # substitutions apply
                s = re.compile(r"^(.*\W+.*)$").sub(r'"\1"', s)
        return s
    
    def __init__(self, input_options=[], output_options=[], quiet=False):
        self.input_options = input_options
        self.output_options = output_options
        self.progress = None
        self.process = None
    
    def __repr__(self):
        return "<{cls}: {cmd}>".format(
            cls=self.__class__.__name__,
            cmd=self.command_string(quote=True))

    def append_input_options(self, items=[]):
        """Add a list of items to the end of the input options."""
        self.input_options += items
    
    def prepend_input_options(self, items=[]):
        """Add a list of items at the front of the input options."""
        self.input_options = items + self.input_options
    
    def append_output_options(self, items=[]):
        """Add a list of items to the end of the output options."""
        self.output_options += items
    
    def prepend_output_options(self, items=[]):
        """Add a list of items at the front of the output options."""
        self.output_options = items + self.output_options
    
    def executable_string(self, quote=False):
        """Return the executable as a string."""
        if quote:
            return ShellCommand.shellquote(self._executable)
        else:
            return self._executable
    
    def argument_string(self, quote=False):
        """Return the list of arguments as a string."""
        args = self._base_options + self.input_options + self.output_options
        if quote:
            return " ".join([ShellCommand.shellquote(a) for a in args])
        else:
            return " ".join(args)
    
    def argument_list(self):
        """Return a combined list of all arguments."""
        args = self._base_options + self.input_options + self.output_options
        # Ensure everything is a string, especially pathlib.Path.
        return [str(a) for a in args]
    
    def command_string(self, quote=False):
        """Return the entire command as a string."""
        return "{exe} {arg}".format(exe=self.executable_string(quote),
                                    arg=self.argument_string(quote))
    
    def process_pattern(self, pat):
        """Respond to a pexpect pattern. Return True on EOF."""
        return (pat == 0)
    
    def run(self):
        """Execute the command in a subprocess."""
        self.process = pexpect.spawn(self.executable_string(),
                                     self.argument_list())
        # EOF is *always* the first pattern.
        patterns = self.process.compile_pattern_list(
            [pexpect.EOF] + self._expect_patterns)
        try:
            while True:
                i = self.process.expect_list(patterns, timeout=None)
                if self.process_pattern(i):
                    break
        except (KeyboardInterrupt):
            pass
        finally:
            if self.progress:
                self.progress.finish()
            self.process.close()
            return self.process.exitstatus
    
    def get_output(self):
        """Execute the command in a subprocess and return the output."""
        return pexpect.run(self.command_string(quote=True))


class ConvertCommand(ShellCommand):
    """An ImageMagick convert command."""
    _executable = shutil.which("convert")
    _base_options = ["-density", "600",
                     "xc:dimgrey", "null:", # dark grey background
                     "("]
    
    def __init__(self, input_options=[], output_options=[], width=2048, height=1536):
        super().__init__(input_options, output_options)
        self._base_options = (["-size", "{w}x{h}".format(w=width, h=height)] +
                              self._base_options)
        self.append_input_options(
            ["-resize", "{w}x{h}".format(w=width, h=height),
             "-background", "white", 
             "-alpha", "remove",
             "-type", "truecolor", # force RGB (this and next line)
             "-define", "colorspace:auto-grayscale=off"])
        self.prepend_output_options([")",
                                     "-gravity", "center",
                                     "-layers", "composite",
                                     "-flatten"])
    

class FFprobeCommand(ShellCommand):
    """An ffprobe shell command."""
    _executable = shutil.which("ffprobe")
    _base_options = ["-loglevel", "error",
                     "-show_entries", "format:stream",
                     "-print_format", "json"]
    
    def __init__(self, input_options=[], output_options=[]):
        super().__init__(input_options, output_options)
        self.entries = None
        # The input file should be the last input option.
        assert(Path(self.input_options[-1]).exists())
        self.last_modified = Path(self.input_options[-1]).stat().st_mtime
    
    def get_entries(self, section="stream", find_list=[]):
        """Fetch specified attributes from the input file."""
        # Re-fetch if the file's changed since we last looked.
        modified = Path(self.input_options[-1]).stat().st_mtime
        if (not self.entries) or (modified > self.last_modified):
            js = json.loads(self.get_output())
            self.entries = {"format": js["format"], "stream": js["streams"][0]}
        return [self.entries[section][f] for f in find_list]

    
class FFmpegCommand(ShellCommand):
    """A "simple" ffmpeg shell command."""
    _executable = shutil.which("ffmpeg")
    _base_options = ["-y", "-nostdin"]
        

class FFmpegConcatCommand(FFmpegCommand):
    """An ffmpeg shell command with a complex concat filter."""
    _expect_patterns = [r"time=(\d\d):(\d\d):(\d\d\.\d\d)"]
    
    def __init__(self, input_options=[], output_options=[], quiet=False,
                 max_progress=100, has_audio=False, has_video=False,
                 process_audio=True, process_video=True,
                 audio_codec="pcm_s16le", video_codec="h264"):
        super().__init__(input_options, output_options)
        self.progress = ProgressBar(max_value=max_progress, quiet=quiet)
        self.has_video = has_video
        self.process_video = process_video
        self.video_codec = video_codec
        if (self.has_video):
            self.prepend_output_options(["-map", "[vconc]"])
            if (self.process_video):
                self.prepend_output_options(["-pix_fmt", "yuv420p"])
            self.prepend_output_options(["-codec:v", self.video_codec])
        self.has_audio = has_audio
        self.process_audio = process_audio
        self.audio_codec = audio_codec
        if (self.has_audio):
            if (self.process_audio):
                self.prepend_output_options(["-ac", "1",
                                             "-map", "[anorm]"])
            else:
                self.prepend_output_options(["-map", "[aconc]"])
            self.prepend_output_options(["-codec:a", self.audio_codec])
        self.filters = []
    
    def append_filter(self, filter):
        """Append a filter to the filters list."""
        if (filter):
            self.filters.append(filter)
        
    def append_normalisation_filter(self):
        """Append a normalisation audio filter to the complex filter."""
        if (self.has_audio):
            self.append_filter("[aconc] dynaudnorm=r=0.25:f=10:b=1 [anorm]")
    
    def append_concat_filter(self, frame_type, segments=[]):
        """Append a concat filter to the filters list"""
        # Ignore frame segments.
        if frame_type in ["a", "v"]:
            if (len(segments) > 1):
                self.append_filter(
                    "{inspecs} concat=n={n}:v={v}:a={a} [{t}conc]".format(
                        inspecs=" ".join([s.output_stream_specifier()
                                        for s in segments]),
                        n=len(segments), v=int(frame_type == "v"),
                        a=int(frame_type == "a"), t=frame_type))
            elif (len(segments) == 1):
                self.append_filter(
                    "{inspec} {a}null [{t}conc]".format(
                        inspec=segments[0].output_stream_specifier(),
                        a=frame_type if frame_type == "a" else "",
                        t=frame_type))
        
    def build_complex_filter(self):
        """Build the complete complex filter.
        
        Filters in the filtergraph are separated by ";".
        """
        return "{f}".format(f=";".join(self.filters))
    
    def argument_string(self, quote=False):
        """Return the list of arguments as a string."""
        args = (self._base_options + self.input_options +
                ["-filter_complex", self.build_complex_filter()] +
                self.output_options)
        if quote:
            return " ".join([ShellCommand.shellquote(a) for a in args])
        else:
            return " ".join(args)
    
    def argument_list(self):
        """Return a combined list of all arguments."""
        args = (self._base_options + self.input_options +
                ["-filter_complex", self.build_complex_filter()] +
                self.output_options)
        # Ensure everything is a string, especially pathlib.Path.
        return [str(a) for a in args]
    
    def process_pattern(self, pat):
        """Respond to a pexpect pattern. Return True on EOF."""
        if (pat == 1):
            elapsed = datetime.timedelta(
                hours=int(self.process.match.group(1)),
                minutes=int(self.process.match.group(2)),
                seconds=float(self.process.match.group(3)))
            self.progress.update(elapsed.total_seconds())
        return (pat == 0)