#!/bin/bash

# Number of concurrent ffmpeg processes
N=${1:-4}

# Create a semaphore with a given number of slots
semaphore=$(mktemp)
exec 3<>$semaphore
for ((i=0; i<N; i++)); do
    echo >&3
done

# Debugging function
debug_log() {
    echo "[$(date '+%Y-%m-%d %H:%M:%S')] $@"
}

# Run ffmpeg command with semaphore locking and delete .wav file on success
run_ffmpeg() {
    local file=$1
    local outfile="${file/%.wav/.opus}"

    # Wait for a slot to become available
    read -u 3
    debug_log "Starting conversion: $file"

    if ffmpeg -i "$file" -y -c:a libopus -vbr on -compression_level 5 -ar 48000 -application audio "$outfile"; then
        debug_log "Completed conversion: $file"
        debug_log "Deleting original file: $file"
        rm "$file"
    else
        debug_log "Failed conversion: $file"
    fi

    # Release the slot
    echo >&3
}

export -f run_ffmpeg
export -f debug_log

# Find all .wav files and convert them to .opus in parallel, respecting semaphore, and delete .wav files on success
find . -maxdepth 1 -type f -name '*.wav' -print0 | xargs -0 -I {} -P $N bash -c 'run_ffmpeg "$@"' _ {}

# Cleanup
exec 3>&-
rm -f $semaphore