#!/bin/bash
# Sourced helper: regenerate one playlist's .m3u8 from the beets library.
#
#   regen_m3u <playlist_name> <out_path>
#
# Writes atomically (temp file in the same dir, then rename over the target):
# rename(2) is atomic for a reader like Navidrome, and needs write access only
# on the directory, so it also replaces a stray wrong-owner leftover .m3u8 (e.g.
# from a pre-container run) without a host-side chown.
#
# Relies on the caller's log() function and $LOG. Always returns 0 (an empty
# result is a warning, not a failure), so it is safe to call as a standalone
# statement under set -euo pipefail.
regen_m3u() {
  local playlist_name="$1"
  local out="$2"
  mkdir -p "$(dirname "$out")"

  local beet_output
  # || true: beet ls exits non-zero on no match, which would trip set -e.
  beet_output=$(beet ls -f '$path' "grouping:${playlist_name}" 2>>"$LOG" || true)
  local track_count=0
  [[ -n "$beet_output" ]] && track_count=$(printf '%s\n' "$beet_output" | wc -l)

  if [[ "$track_count" -gt 0 ]]; then
    local tmp="${out}.tmp.$$"
    {
      echo "#EXTM3U"
      echo "$beet_output"
    } > "$tmp"
    mv "$tmp" "$out"
    log "M3U updated with $track_count tracks"
  else
    log "WARNING: beet list returned no tracks for grouping:${playlist_name} — not updating M3U"
  fi
  return 0
}