#!/bin/bash
#
# Timelapse Tuner - tt
# Copyright (C) 2024 Roger Gonzalez

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.
#


# Function to check if a command exists
command_exists() {
    command -v "$1" >/dev/null 2>&1
}

# Function to print usage information
print_usage() {
    echo "Usage: $0 --video <video_file> --output <output_file> [--fade <fade_duration>]"
    echo "Options:"
    echo "  --video  Specify the input video file"
    echo "  --output Specify the output MP4 file name (default: output_video.mp4)"
    echo "  --fade   Specify the fade duration in seconds (default: 2)"
}

# Function to log messages with timestamps
log_message() {
    echo "[$(date +'%Y-%m-%d %H:%M:%S')] $1"
}

# Initialize variables
video_file=""
output_file="output_video.mp4"
fade_duration=2

# Parse command-line arguments
while [[ $# -gt 0 ]]; do
    case $1 in
        --video)
            video_file="$2"
            shift 2
            ;;
        --output)
            output_file="$2"
            shift 2
            ;;
        --fade)
            fade_duration="$2"
            shift 2
            ;;
        *)
            log_message "Error: Unknown option: $1"
            print_usage
            exit 1
            ;;
    esac
done

# Check if required programs exist
log_message "Checking for required programs..."
for cmd in ffmpeg ffprobe bc; do
    if ! command_exists "$cmd"; then
        log_message "Error: $cmd is not installed or not in PATH"
        exit 1
    fi
done
log_message "All required programs found"

# Check if a video file is provided
if [ -z "$video_file" ]; then
    log_message "Error: No video file specified"
    print_usage
    exit 1
fi

# Check if the video file exists
if [ ! -f "$video_file" ]; then
    log_message "Error: Video file '$video_file' not found"
    exit 1
fi
log_message "Input video file: $video_file"

# Pick a random .mp3 file from the current directory
log_message "Selecting a random MP3 file..."
audio_file=$(ls *.mp3 2>/dev/null | shuf -n 1)

# Check if an audio file was found
if [ -z "$audio_file" ]; then
    log_message "Error: No .mp3 files found in the current directory"
    exit 1
fi
log_message "Selected audio file: $audio_file"

# Get the length of the audio file in seconds
log_message "Calculating audio file length..."
audio_length=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$audio_file")
log_message "Audio length: $audio_length seconds"

log_message "Fade duration set to $fade_duration seconds"

# Get the length of the video file in seconds
log_message "Calculating video file length..."
video_length=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$video_file")
log_message "Video length: $video_length seconds"

# Use the shorter of the two lengths for fade-out calculation
log_message "Calculating minimum length for fade-out..."
min_length=$(echo "if ($video_length < $audio_length) $video_length else $audio_length" | bc)
log_message "Minimum length: $min_length seconds"

# Ensure fade-out starts at a valid time
log_message "Calculating fade-out start time..."
fade_out_start=$(echo "$min_length - $fade_duration" | bc)
if (( $(echo "$fade_out_start < 0" | bc -l) )); then
    fade_out_start=0
fi
log_message "Fade-out starts at: $fade_out_start seconds"

# Calculate a random start time within the audio length minus the video length
log_message "Calculating random start time for audio..."
max_start=$(echo "$audio_length - $video_length" | bc | cut -d'.' -f1)
if [ "$max_start" -lt 0 ]; then
    random_start=0
else
    random_start=$(shuf -i 0-"$max_start" -n 1)
fi
log_message "Random start time: $random_start seconds"

# Run ffmpeg with audio fade-in, fade-out, and random start
log_message "Starting ffmpeg process..."
ffmpeg -loglevel error -stats -i "$video_file" -ss "$random_start" -i "$audio_file" -filter_complex \
"[1:a]afade=t=in:st=0:d=$fade_duration,afade=t=out:st=$fade_out_start:d=$fade_duration[a]" \
-map 0:v -map "[a]" -c:v libx264 -c:a aac -shortest "$output_file"

# Check if ffmpeg was successful
if [ $? -eq 0 ]; then
    log_message "ffmpeg process completed successfully"
    log_message "Merged $video_file with random audio: $audio_file"
    log_message "Audio starts at $random_start seconds, with fade-in/out effects"
    log_message "Output saved as: $output_file"
else
    log_message "Error: ffmpeg process failed"
    exit 1
fi