"""Calculate audio stats."""

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,
]


@activity_task_logger(INPUT_FIELDS)
def calculate_audio_stats(inputs):
    """Calculate audio stats.

    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]

    output_options = {
        'vn': None,  # don't process video stream
    }

    video_s3_url = s3_connector.get_url_for_s3_object(s3_bucket, s3_key)

    (stdout, stderr) = (
        ffmpeg
        .input(video_s3_url)
        .filter('astats')
        .output('pipe:', format='null', **output_options)
        .run(capture_stderr=True)
    )
    rms_level_db_regex = r'RMS level dB:\s(.*)'
    left_channel_start_regex = 'Channel: 1'
    right_channel_start_regex = 'Channel: 2'

    stderr_lines = text.bytes_to_lines_of_text(stderr)

    outputs = {
        job_io_fields.LEFT_AUDIO_CHANNEL_RMS_VOLUME_DECIBELS: None,
        job_io_fields.RIGHT_AUDIO_CHANNEL_RMS_VOLUME_DECIBELS: None,
    }
    left_audio_channel_rms_volume = None
    right_audio_channel_rms_volume = None
    current_channel = None

    for line in stderr_lines:
        left_channel_start_match = re.search(left_channel_start_regex, line)
        if left_channel_start_match:
            current_channel = 'left'
            continue

        right_channel_start_match = re.search(right_channel_start_regex, line)
        if right_channel_start_match:
            current_channel = 'right'
            continue

        rms_level_db_match = re.search(rms_level_db_regex, line)
        if not rms_level_db_match:
            continue

        if current_channel == 'left':
            [left_audio_channel_rms_volume] = rms_level_db_match.groups()
            if left_audio_channel_rms_volume == '-inf':
                left_audio_channel_rms_volume = -60
            outputs[job_io_fields.LEFT_AUDIO_CHANNEL_RMS_VOLUME_DECIBELS] = (
                float(left_audio_channel_rms_volume))
        elif current_channel == 'right':
            [right_audio_channel_rms_volume] = rms_level_db_match.groups()
            if right_audio_channel_rms_volume == '-inf':
                right_audio_channel_rms_volume = -60
            outputs[job_io_fields.RIGHT_AUDIO_CHANNEL_RMS_VOLUME_DECIBELS] = (
                float(right_audio_channel_rms_volume))

        if None not in [
                left_audio_channel_rms_volume, right_audio_channel_rms_volume]:
            return outputs

    return outputs