#!/usr/bin/env ruby
# frozen_string_literal: true
#
# Face detection daemon for Albumen.
#
# Polls MEDIA_ROOT for images not yet in a per-directory faces.json sidecar
# and runs faces.py (dlib CNN model) on them.  Never touches album.json —
# zero write contention with update.rb.
#
# faces.json schema (per directory):
#   filename → null              error during detection; will retry next pass
#   filename → []                processed, no faces found
#   filename → [{box,encoding}]  face data
#   (key absent)                 not yet processed
#
# Configuration — from ENV or /opt/albumen/config.yml (under `faces:` key):
#   workers:        20   # ThreadPoolExecutor workers passed to faces.py
#   poll_interval: 300   # seconds between full-tree sweeps
#
# Signal handling: SIGTERM / SIGINT triggers graceful shutdown between dirs.

require 'json'
require 'yaml'
require 'fileutils'
require 'open3'

MEDIA_ROOT   = (ENV['MEDIA_ROOT']   || '/var/albumen').freeze
CONFIG_PATH  = (ENV['CONFIG_PATH']  || '/opt/albumen/config.yml').freeze
LOG_PATH     = (ENV['LOG_PATH']     || '/opt/albumen/log/albumen.log').freeze
VENV_PYTHON  = (ENV['VENV_PYTHON']  || '/opt/albumen/venv/bin/python3').freeze
FACES_SCRIPT = (ENV['FACES_SCRIPT'] || '/opt/albumen/scripts/faces.py').freeze

IMAGE_EXTS = %w[jpg jpeg png gif webp heic heif tiff bmp].freeze

_cfg           = File.exist?(CONFIG_PATH) ? (YAML.load_file(CONFIG_PATH, symbolize_names: true) rescue {}) : {}
FACES_WORKERS  = (_cfg.dig(:faces, :workers)       || 20).to_i.freeze
POLL_INTERVAL  = (_cfg.dig(:faces, :poll_interval) || 300).to_i.freeze

$shutdown = false
Signal.trap('TERM') { $shutdown = true }
Signal.trap('INT')  { $shutdown = true }

# ── Logging ───────────────────────────────────────────────────────────────────

def log(msg)
  $stdout.puts msg
  $stdout.flush
  ts = Time.now.strftime('%Y-%m-%d %H:%M:%S')
  File.open(LOG_PATH, 'a') { |f| f.puts "[#{ts}] [faces] #{msg}" }
rescue StandardError
  # never crash on log failure
end

# ── faces.json helpers ────────────────────────────────────────────────────────

def load_faces_json(path)
  return {} unless File.exist?(path)
  JSON.parse(File.read(path))
rescue JSON::ParserError
  {}
end

def save_faces_atomic(path, data)
  tmp = "#{path}.tmp.#{Process.pid}"
  File.write(tmp, JSON.generate(data))
  File.rename(tmp, path)
rescue StandardError => e
  File.unlink(tmp) rescue nil
  log "  Error saving #{path}: #{e.message}"
end

# Returns image filenames that still need processing.
# null-valued entries (prior errors) are retried; [] entries are done.
def pending_images(dir)
  faces = load_faces_json(File.join(dir, 'faces.json'))
  Dir.children(dir)
     .select { |n| IMAGE_EXTS.include?(File.extname(n).downcase.delete_prefix('.')) }
     .reject { |n| faces.key?(n) && !faces[n].nil? }
     .sort
end

# ── Core processing ───────────────────────────────────────────────────────────

def process_dir(dir)
  pending = pending_images(dir)
  return if pending.empty?

  rel   = dir.delete_prefix(MEDIA_ROOT).delete_prefix('/')
  label = rel.empty? ? '(root)' : rel
  log "#{label}: #{pending.size} image(s) pending"

  paths = pending.map { |n| File.join(dir, n) }
  cmd   = [VENV_PYTHON, FACES_SCRIPT, '--workers', FACES_WORKERS.to_s, *paths]

  stdout, stderr, status = Open3.capture3(*cmd)

  unless status.success? || stdout.strip.start_with?('{')
    log "  faces.py error (exit #{status.exitstatus}): #{stderr.strip}"
    return
  end

  begin
    results = JSON.parse(stdout)
  rescue JSON::ParserError => e
    log "  faces.py output is not valid JSON: #{e.message}"
    return
  end

  faces_path = File.join(dir, 'faces.json')
  faces = load_faces_json(faces_path)  # re-read before writing (pick up concurrent changes)

  pending.each do |name|
    full          = File.join(dir, name)
    faces[name]   = results[full]
    detail = faces[name].nil? ? 'error (will retry)' :
             faces[name].empty? ? 'no faces' :
             "#{faces[name].length} face(s)"
    log "  #{name}: #{detail}"
  end

  save_faces_atomic(faces_path, faces)
end

def run_pass
  dirs = [MEDIA_ROOT] + Dir.glob("#{MEDIA_ROOT}/**/*/").sort
  dirs.each do |dir|
    return if $shutdown
    process_dir(dir)
  end
end

# ── Main loop ─────────────────────────────────────────────────────────────────

log "Starting (workers=#{FACES_WORKERS}, poll_interval=#{POLL_INTERVAL}s, media=#{MEDIA_ROOT})"

loop do
  break if $shutdown
  run_pass
  break if $shutdown

  # Sleep in 1-second increments so SIGTERM/SIGINT takes effect promptly
  POLL_INTERVAL.times do
    break if $shutdown
    sleep 1
  end
end

log 'Shutting down.'