#!/usr/bin/env bash
# Download YouTube video(s) at highest quality as merged MP4 (Linux/macOS).
#
#   ./yt-download.sh "https://www.youtube.com/watch?v=xxxx"
#   ./yt-download.sh URL1 URL2 URL3
#
# Env overrides:
#   OUTDIR=/path/to/dir      output directory (default: ~/Downloads)
#   FORMAT="..."             yt-dlp -f selector (default: bestvideo+bestaudio/best)
#   COOKIES=/path/cookies.txt  Netscape cookies file (default: cookies.txt beside this script)
#
# Requirements: yt-dlp, ffmpeg, and a JS runtime (bun/deno/node) must be installed.
#   pipx install yt-dlp   (or: brew install yt-dlp / apt install yt-dlp)
#   brew install ffmpeg   (or: apt install ffmpeg)
#   bun / deno / node any one (needed for YouTube JS challenges)

set -euo pipefail

if [ "$#" -lt 1 ]; then
  echo "usage: $0 <youtube-url> [more urls...]" >&2
  exit 2
fi

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
OUTDIR="${OUTDIR:-$HOME/Downloads}"
FORMAT="${FORMAT:-bestvideo+bestaudio/best}"

# yt-dlp
if ! command -v yt-dlp >/dev/null 2>&1; then
  echo "error: yt-dlp not found. Install it: pipx install yt-dlp" >&2
  exit 1
fi
# ffmpeg
if ! command -v ffmpeg >/dev/null 2>&1; then
  echo "warning: ffmpeg not found; merging video+audio will fail. Install ffmpeg." >&2
fi

# JS runtime for YouTube JS challenges. Prefer bun, fall back to deno/node.
# Override with JS_RUNTIME=bun|deno|node (must be on PATH).
# --no-js-runtimes ensures ONLY the chosen runtime is used (bun won't be
# silently shadowed by yt-dlp's built-in deno preference).
JS_ARGS=()
JS_RUNTIME_NAME=
JS_RUNTIME_BIN=
if [ -n "${JS_RUNTIME:-}" ] && command -v "$JS_RUNTIME" >/dev/null 2>&1; then
  JS_RUNTIME_NAME="$JS_RUNTIME"
  JS_RUNTIME_BIN="$(command -v "$JS_RUNTIME")"
elif command -v bun >/dev/null 2>&1; then
  JS_RUNTIME_NAME="bun"
  JS_RUNTIME_BIN="$(command -v bun)"
elif command -v deno >/dev/null 2>&1; then
  JS_RUNTIME_NAME="deno"
  JS_RUNTIME_BIN="$(command -v deno)"
elif [ -x "$HOME/.deno/bin/deno" ]; then
  JS_RUNTIME_NAME="deno"
  JS_RUNTIME_BIN="$HOME/.deno/bin/deno"
elif command -v node >/dev/null 2>&1; then
  JS_RUNTIME_NAME="node"
  JS_RUNTIME_BIN="$(command -v node)"
fi
if [ -n "$JS_RUNTIME_NAME" ]; then
  JS_ARGS=(--no-js-runtimes --js-runtimes "$JS_RUNTIME_NAME:$JS_RUNTIME_BIN")
else
  echo "warning: no JS runtime (bun/deno/node) found. YouTube may reject the download ('confirm you're not a bot')." >&2
fi

# cookies
COOKIES="${COOKIES:-$SCRIPT_DIR/cookies.txt}"
COOKIE_ARGS=()
if [ -f "$COOKIES" ]; then
  COOKIE_ARGS=(--cookies "$COOKIES")
  echo "[info] using cookies: $COOKIES"
else
  echo "[info] no cookies.txt -- public videos only. See SKILL.md for login-required videos."
fi

mkdir -p "$OUTDIR"

fail=0
for url in "$@"; do
  echo ""
  echo "==== downloading: $url ===="
  if ! yt-dlp "${JS_ARGS[@]}" "${COOKIE_ARGS[@]}" \
        -f "$FORMAT" \
        --merge-output-format mp4 \
        -o "$OUTDIR/%(title)s [%(height)sp].%(ext)s" \
        --no-playlist \
        "$url"; then
    fail=$((fail+1))
    echo "warning: failed: $url" >&2
  fi
done

if [ "$fail" -gt 0 ]; then
  echo "warning: $fail download(s) failed." >&2
  exit 1
fi
echo ""
echo "All done. Saved to: $OUTDIR"