#
#            PySceneDetect: Python-Based Video Scene Detector
#   -------------------------------------------------------------------
#     [  Site:    https://scenedetect.com                           ]
#     [  Docs:    https://scenedetect.com/docs/                     ]
#     [  Github:  https://github.com/Breakthrough/PySceneDetect/    ]
#
# Copyright (C) 2014-2024 Brandon Castellano <http://www.bcastell.com>.
# PySceneDetect is licensed under the BSD 3-Clause License; see the
# included LICENSE file, or visit one of the above pages for details.
#
# This software may also invoke mkvmerge or FFmpeg, if available.
# FFmpeg is a trademark of Fabrice Bellard.
# mkvmerge is Copyright (C) 2005-2016, Matroska.
# Certain distributions of PySceneDetect may include the above software;
# see the included LICENSE-FFMPEG and LICENSE-MKVMERGE files.
#
"""``scenedetect.video_splitter`` Module

The `scenedetect.video_splitter` module contains functions to split existing videos into clips
using ffmpeg or mkvmerge.

These programs can be obtained from following URLs (note that mkvmerge is a part mkvtoolnix):

 * FFmpeg:   [ https://ffmpeg.org/download.html ]
 * mkvmerge: [ https://mkvtoolnix.download/downloads.html ]

If you are a Linux user, you can likely obtain the above programs from your package manager.

Once installed, ensure the program can be accessed system-wide by calling the `mkvmerge` or `ffmpeg`
command from a terminal/command prompt. PySceneDetect will automatically use whichever program is
available on the computer, depending on the specified command-line options.
"""

import logging
import math
import subprocess
import time
import typing as ty
from dataclasses import dataclass
from pathlib import Path

from scenedetect.frame_timecode import FrameTimecode
from scenedetect.platform import CommandTooLong, Template, get_ffmpeg_path, invoke_command, tqdm

logger = logging.getLogger("pyscenedetect")

TimecodePair = ty.Tuple[FrameTimecode, FrameTimecode]
"""Named type for pairs of timecodes, which typically represents the start/end of a scene."""

COMMAND_TOO_LONG_STRING = """
Cannot split video due to too many scenes (resulting command
is too large to process). To work around this issue, you can
split the video manually by exporting a list of cuts with the
`list-scenes` command.
See https://github.com/Breakthrough/PySceneDetect/issues/164
for details.  Sorry about that!
"""

FFMPEG_PATH: ty.Optional[str] = get_ffmpeg_path()
"""Relative path to the ffmpeg binary on this system, if any (will be None if not available)."""

DEFAULT_FFMPEG_ARGS = (
    "-map 0:v:0 -map 0:a? -map 0:s? -c:v libx264 -preset veryfast -crf 22 -c:a aac"
)
"""Default arguments passed to ffmpeg when invoking the `split_video_ffmpeg` function."""

##
## Command Availability Checking Functions
##


def is_mkvmerge_available() -> bool:
    """Is mkvmerge Available: Gracefully checks if mkvmerge command is available.

    Returns:
        True if `mkvmerge` can be invoked, False otherwise.
    """
    ret_val = None
    try:
        ret_val = subprocess.call(["mkvmerge", "--quiet"])
    except OSError:
        return False
    if ret_val is not None and ret_val != 2:
        return False
    return True


def is_ffmpeg_available() -> bool:
    """Is ffmpeg Available: Gracefully checks if ffmpeg command is available.

    Returns:
        True if `ffmpeg` can be invoked, False otherwise.
    """
    return FFMPEG_PATH is not None


##
## Output Naming
##


@dataclass
class VideoMetadata:
    """Information about the video being split."""

    name: str
    """Expected name of the video. May differ from `path`."""
    path: Path
    """Path to the input file."""
    total_scenes: int
    """Total number of scenes that will be written."""


@dataclass
class SceneMetadata:
    """Information about the scene being extracted."""

    index: int
    """0-based index of this scene."""
    start: FrameTimecode
    """First frame."""
    end: FrameTimecode
    """Last frame."""


PathFormatter = ty.Callable[[VideoMetadata, SceneMetadata], ty.AnyStr]


def default_formatter(template: str) -> PathFormatter:
    """Formats filenames using a template string which allows the following variables:

    `$VIDEO_NAME`, `$SCENE_NUMBER`, `$START_TIME`, `$END_TIME`, `$START_FRAME`, `$END_FRAME`
    """
    MIN_DIGITS = 3
    format_scene_number: PathFormatter = lambda video, scene: (
        ("%0" + str(max(MIN_DIGITS, math.floor(math.log(video.total_scenes, 10)) + 1)) + "d")
        % (scene.index + 1)
    )
    formatter: PathFormatter = lambda video, scene: Template(template).safe_substitute(
        VIDEO_NAME=video.name,
        SCENE_NUMBER=format_scene_number(video, scene),
        START_TIME=str(scene.start.get_timecode().replace(":", ";")),
        END_TIME=str(scene.end.get_timecode().replace(":", ";")),
        START_FRAME=str(scene.start.get_frames()),
        END_FRAME=str(scene.end.get_frames()),
    )
    return formatter


##
## Split Video Functions
##


def split_video_mkvmerge(
    input_video_path: str,
    scene_list: ty.Iterable[TimecodePair],
    output_dir: ty.Optional[ty.Union[str, Path]] = None,
    output_file_template: ty.Optional[ty.Union[str, Path]] = "$VIDEO_NAME.mkv",
    video_name: ty.Optional[str] = None,
    show_output: bool = False,
    suppress_output=None,
) -> int:
    """Calls the mkvmerge command on the input video, splitting it at the
    passed timecodes, where each scene is written in sequence from 001.

    Arguments:
        input_video_path: Path to the video to be split.
        scene_list : List of scenes as pairs of FrameTimecodes denoting the start/end times.
        output_dir: Directory to output videos. If not set, output will be in working directory.
        output_file_template: Template to use for generating output files. Note that mkvmerge always
            adds the suffix "-$SCENE_NUMBER" to the output paths. Only the $VIDEO_NAME variable
            is supported by this function.
        video_name (str): Name of the video to be substituted in output_file_template for
            $VIDEO_NAME. If not specified, will be obtained from the filename.
        show_output: If False, adds the --quiet flag when invoking `mkvmerge`.
        suppress_output: [DEPRECATED] DO NOT USE. For backwards compatibility only.
    Returns:
        Return code of invoking mkvmerge (0 on success). If scene_list is empty, will
        still return 0, but no commands will be invoked.
    """
    # Handle backwards compatibility with v0.5 API.
    if isinstance(input_video_path, list):
        logger.error("Using a list of paths is deprecated. Pass a single path instead.")
        if len(input_video_path) > 1:
            raise ValueError("Concatenating multiple input videos is not supported.")
        input_video_path = input_video_path[0]
    if suppress_output is not None:
        logger.error("suppress_output is deprecated, use show_output instead.")
        show_output = not suppress_output

    if not scene_list:
        return 0

    if video_name is None:
        video_name = Path(input_video_path).stem

    # mkvmerge doesn't support adding scene metadata to filenames. It always adds the scene
    # number prefixed with a dash to the filenames.
    template = Template(output_file_template)
    output_path = template.safe_substitute(VIDEO_NAME=video_name)
    if output_dir:
        output_path = Path(output_dir) / output_path
    output_path = Path(output_path)
    logger.info(f"Splitting video with mkvmerge, path template: {output_path}")
    # If there is only one scene, mkvmerge omits the suffix for the output. To make the filenames
    # consistent with the output when there are multiple scenes present, we append "-001".
    if len(scene_list) == 1:
        output_path = output_path.with_stem(output_path.stem + "-001")
    output_path.parent.mkdir(parents=True, exist_ok=True)

    call_list = ["mkvmerge"]
    if not show_output:
        call_list.append("--quiet")
    call_list += [
        "-o",
        str(output_path),
        "--split",
        "parts:%s"
        % ",".join(
            [
                "%s-%s" % (start_time.get_timecode(), end_time.get_timecode())
                for start_time, end_time in scene_list
            ]
        ),
        input_video_path,
    ]
    total_frames = scene_list[-1][1].get_frames() - scene_list[0][0].get_frames()
    processing_start_time = time.time()
    ret_val = 0
    try:
        # TODO: Capture stdout/stderr and show that if the command fails.
        ret_val = invoke_command(call_list)
        if show_output:
            logger.info(
                "Average processing speed %.2f frames/sec.",
                float(total_frames) / (time.time() - processing_start_time),
            )
    except CommandTooLong:
        logger.error(COMMAND_TOO_LONG_STRING)
    except OSError:
        logger.error(
            "mkvmerge could not be found on the system."
            " Please install mkvmerge to enable video output support."
        )
    if ret_val != 0:
        logger.error("Error splitting video (mkvmerge returned %d).", ret_val)
    return ret_val


def split_video_ffmpeg(
    input_video_path: str,
    scene_list: ty.Iterable[TimecodePair],
    output_dir: ty.Optional[Path] = None,
    output_file_template: str = "$VIDEO_NAME-Scene-$SCENE_NUMBER.mp4",
    video_name: ty.Optional[str] = None,
    arg_override: str = DEFAULT_FFMPEG_ARGS,
    show_progress: bool = False,
    show_output: bool = False,
    suppress_output=None,
    hide_progress=None,
    formatter: ty.Optional[PathFormatter] = None,
) -> int:
    """Calls the ffmpeg command on the input video, generating a new video for
    each scene based on the start/end timecodes.

    Arguments:
        input_video_path: Path to the video to be split.
        scene_list (List[ty.Tuple[FrameTimecode, FrameTimecode]]): List of scenes
            (pairs of FrameTimecodes) denoting the start/end frames of each scene.
        output_dir: Directory to output videos. If not set, output will be in working directory.
        output_file_template (str): Template to use for generating output filenames.
            The following variables will be replaced in the template for each scene:
            $VIDEO_NAME, $SCENE_NUMBER, $START_TIME, $END_TIME, $START_FRAME, $END_FRAME
        video_name (str): Name of the video to be substituted in output_file_template. If not
            passed will be calculated from input_video_path automatically.
        arg_override (str): Allows overriding the arguments passed to ffmpeg for encoding.
        show_progress (bool): If True, will show progress bar provided by tqdm (if installed).
        show_output (bool): If True, will show output from ffmpeg for first split.
        suppress_output: [DEPRECATED] DO NOT USE. For backwards compatibility only.
        hide_progress: [DEPRECATED] DO NOT USE. For backwards compatibility only.
        formatter: Custom formatter callback. Overrides `output_file_template`.

    Returns:
        Return code of invoking ffmpeg (0 on success). If scene_list is empty, will
        still return 0, but no commands will be invoked.
    """
    # Handle backwards compatibility with v0.5 API.
    if isinstance(input_video_path, list):
        logger.error("Using a list of paths is deprecated. Pass a single path instead.")
        if len(input_video_path) > 1:
            raise ValueError("Concatenating multiple input videos is not supported.")
        input_video_path = input_video_path[0]
    if suppress_output is not None:
        logger.error("suppress_output is deprecated, use show_output instead.")
        show_output = not suppress_output
    if hide_progress is not None:
        logger.error("hide_progress is deprecated, use show_progress instead.")
        show_progress = not hide_progress

    if not scene_list:
        return 0

    logger.info("Splitting video with ffmpeg, output path template:\n  %s", output_file_template)
    if output_dir:
        logger.info("Output folder:\n  %s", output_file_template)

    if video_name is None:
        video_name = Path(input_video_path).stem

    arg_override = arg_override.replace('\\"', '"')

    ret_val = 0
    arg_override = arg_override.split(" ")
    scene_num_format = "%0"
    scene_num_format += str(max(3, math.floor(math.log(len(scene_list), 10)) + 1)) + "d"

    if formatter is None:
        formatter = default_formatter(output_file_template)
    video_metadata = VideoMetadata(
        name=video_name, path=input_video_path, total_scenes=len(scene_list)
    )

    try:
        progress_bar = None
        total_frames = scene_list[-1][1].get_frames() - scene_list[0][0].get_frames()
        if show_progress:
            progress_bar = tqdm(total=total_frames, unit="frame", miniters=1, dynamic_ncols=True)
        processing_start_time = time.time()
        for i, (start_time, end_time) in enumerate(scene_list):
            duration = end_time - start_time
            scene_metadata = SceneMetadata(index=i, start=start_time, end=end_time)
            output_path = Path(formatter(scene=scene_metadata, video=video_metadata))
            if output_dir:
                output_path = Path(output_dir) / output_path
            output_path.parent.mkdir(parents=True, exist_ok=True)

            # Gracefully handle case where FFMPEG_PATH might be unset.
            call_list = [FFMPEG_PATH if FFMPEG_PATH is not None else "ffmpeg"]
            if not show_output:
                call_list += ["-v", "quiet"]
            elif i > 0:
                # Only show ffmpeg output for the first call, which will display any
                # errors if it fails, and then break the loop. We only show error messages
                # for the remaining calls.
                call_list += ["-v", "error"]
            call_list += [
                "-nostdin",
                "-y",
                "-ss",
                str(start_time.get_seconds()),
                "-i",
                input_video_path,
                "-t",
                str(duration.get_seconds()),
            ]
            call_list += arg_override
            call_list += ["-sn"]
            call_list += [str(output_path)]
            ret_val = invoke_command(call_list)
            if show_output and i == 0 and len(scene_list) > 1:
                logger.info(
                    "Output from ffmpeg for Scene 1 shown above, splitting remaining scenes..."
                )
            if ret_val != 0:
                # TODO: Capture stdout/stderr and display it on any failed calls.
                logger.error("Error splitting video (ffmpeg returned %d).", ret_val)
                break
            if progress_bar:
                progress_bar.update(duration.get_frames())

        if progress_bar:
            progress_bar.close()
        if show_output:
            logger.info(
                "Average processing speed %.2f frames/sec.",
                float(total_frames) / (time.time() - processing_start_time),
            )

    except CommandTooLong:
        logger.error(COMMAND_TOO_LONG_STRING)
    except OSError:
        logger.error(
            "ffmpeg could not be found on the system."
            " Please install ffmpeg to enable video output support."
        )
    return ret_val