"""Detect black intervals at beginning and end of video."""

import re

import ffmpeg

from video.connectors import s3 as s3_connector
from video.constants import job_io_fields
from video.logic.activity_task_logger import activity_task_logger
from video.utils import text


INPUT_FIELDS = [
    job_io_fields.INPUT_VIDEO_S3_BUCKET,
    job_io_fields.INPUT_VIDEO_S3_KEY,
    job_io_fields.VIDEO_STREAM_FRAME_RATE_FRAMES_PER_SECOND,
    job_io_fields.VIDEO_STREAM_DURATION_SECONDS,
]


@activity_task_logger(INPUT_FIELDS)
def detect_black_intervals_at_beginning_and_end_of_video(inputs):
    """Detect black intervals at beginning and end of video.

    Args:
        inputs (dict): Inputs.

    Returns:
        dict: Outputs.
    """
    s3_bucket = inputs[job_io_fields.INPUT_VIDEO_S3_BUCKET]
    s3_key = inputs[job_io_fields.INPUT_VIDEO_S3_KEY]
    frames_per_second = inputs[
        job_io_fields.VIDEO_STREAM_FRAME_RATE_FRAMES_PER_SECOND]
    seconds_per_frame = 1 / frames_per_second
    duration_seconds = inputs[job_io_fields.VIDEO_STREAM_DURATION_SECONDS]
    last_frame_start_time = duration_seconds - seconds_per_frame
    # blackdetect parameters
    # https://ffmpeg.org/ffmpeg-filters.html#blackdetect
    black_min_duration = seconds_per_frame
    picture_black_ratio_th = 1
    pixel_black_th = 0
    output_options = {
        'an': None,  # don't process audio stream
    }

    video_s3_url = s3_connector.get_url_for_s3_object(s3_bucket, s3_key)

    (stdout, stderr) = (
        ffmpeg
        .input(video_s3_url)
        .filter(
            'blackdetect',
            black_min_duration=black_min_duration,
            picture_black_ratio_th=picture_black_ratio_th,
            pixel_black_th=pixel_black_th,
        )
        .output('pipe:', format='null', **output_options)
        .run(capture_stderr=True)
    )
    black_start_regex = r'black_start:\s*(\S*)'
    black_end_regex = r'black_end:\s*(\S*)'

    stderr_lines = text.bytes_to_lines_of_text(stderr)

    outputs = {
        job_io_fields.BLACK_INTERVAL_AT_BEGINNING_ENDS_AT_SECONDS: None,
        job_io_fields.BLACK_INTERVAL_AT_END_BEGINS_AT_SECONDS: None,
    }
    black_start = None
    black_end = None

    for line in stderr_lines:
        black_start_match = re.search(black_start_regex, line)
        if black_start_match:
            black_start = float(black_start_match.group(1))
            black_end_match = re.search(black_end_regex, line)
            black_end = float(black_end_match.group(1))

        if black_start == 0:
            outputs[
                job_io_fields.BLACK_INTERVAL_AT_BEGINNING_ENDS_AT_SECONDS
            ] = black_end

        if black_end == last_frame_start_time:
            outputs[
                job_io_fields.BLACK_INTERVAL_AT_END_BEGINS_AT_SECONDS
            ] = black_start

    return outputs