#!/usr/bin/env bash
set -euo pipefail

die() {
  echo "$*" >&2
  exit 1
}

usage() {
  cat <<'EOF' >&2
Usage: convert-to-video.sh /path/to/audio.file
Creates a slideshow video from stormux images and the provided audio.
EOF
  exit 1
}

require_commands() {
  for cmd in "$@"; do
    command -v "$cmd" >/dev/null 2>&1 || die "Missing dependency: $cmd"
  done
}

locate_images() {
  local candidate="."
  local have_all=true

  for i in 1 2 3 4 5; do
    [ -f "$candidate/stormux${i}.png" ] || have_all=false
  done

  if [ "$have_all" = true ]; then
    printf '%s\n' "$candidate"
    return
  fi

  candidate="/usr/share/stormux/slideshow"
  for i in 1 2 3 4 5; do
    [ -f "$candidate/stormux${i}.png" ] || die "Missing image: $candidate/stormux${i}.png"
  done

  printf '%s\n' "$candidate"
}

detect_container() {
  local audio_file="$1"
  local codec

  codec="$(ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -of csv=p=0 "$audio_file" || true)"
  case "$codec" in
    aac|mp3) echo "mp4" ;;
    *) echo "mkv" ;;
  esac
}

build_video() {
  local audio_file="$1"
  local image_dir="$2"
  local container="$3"
  local output_filename="$4"
  local output_dir="$HOME/Videos"

  mkdir -p "$output_dir"

  ffmpeg -y \
    -stream_loop -1 -framerate 1/35 -start_number 1 -i "$image_dir/stormux%d.png" \
    -i "$audio_file" \
    -map 0:v:0 -map 1:a:0 \
    -c:v libx264 -crf 18 -preset veryfast -r 30 -pix_fmt yuv420p \
    -c:a copy \
    -shortest \
    "$output_dir/${output_filename##*/}"
}

[ "$#" -eq 1 ] || usage

audio="$1"
[ -f "$audio" ] || die "Audio file not found: $audio"

require_commands ffmpeg ffprobe

image_dir="$(locate_images)"
container="$(detect_container "$audio")"
base="$(basename "$audio")"
name="${base%.*}"
output="${name}.${container}"

build_video "$audio" "$image_dir" "$container" "$output"

echo "Wrote $HOME/Videos/$output"