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

command -v ffmpeg >/dev/null || { echo "ffmpeg is required" >&2; exit 127; }
command -v ffprobe >/dev/null || { echo "ffprobe is required" >&2; exit 127; }

test_dir="$(mktemp -d)"
trap 'rm -rf "$test_dir"' EXIT

make_sample() {
  local output="$1"
  local duration="$2"
  ffmpeg -hide_banner -loglevel error \
    -f lavfi -i "testsrc2=size=320x180:rate=25" \
    -f lavfi -i "sine=frequency=1000:sample_rate=48000" \
    -t "$duration" -c:v libx264 -preset ultrafast -pix_fmt yuv420p \
    -c:a aac -b:a 96k -movflags +faststart -y "$output"
}

make_sample "$test_dir/short-a.mp4" 1.2
make_sample "$test_dir/short-b.mp4" 2.1
make_sample "$test_dir/normal.mp4" 6.4

run_case() {
  local name="$1"
  local minimum_duration="$2"
  shift 2
  local list="$test_dir/$name.txt"
  local output="$test_dir/$name.mp4"
  : > "$list"
  for source in "$@"; do
    printf "file '%s'\n" "$source" >> "$list"
  done

  ffmpeg -hide_banner -loglevel error -f concat -safe 0 -i "$list" \
    -map 0 -c copy -movflags +faststart -y "$output"

  local duration
  duration="$(ffprobe -v error -show_entries format=duration -of default=nw=1:nk=1 "$output")"
  local video_streams
  video_streams="$(ffprobe -v error -select_streams v:0 -show_entries stream=index -of csv=p=0 "$output" | wc -l)"
  awk -v actual="$duration" -v minimum="$minimum_duration" 'BEGIN { exit !(actual >= minimum) }'
  test "$video_streams" -ge 1
  echo "$name ok: duration=${duration}s"
}

run_case short_then_normal 7.0 "$test_dir/short-a.mp4" "$test_dir/normal.mp4"
run_case normal_then_short 7.0 "$test_dir/normal.mp4" "$test_dir/short-a.mp4"
run_case consecutive_shorts 9.0 "$test_dir/short-a.mp4" "$test_dir/short-b.mp4" "$test_dir/normal.mp4"