local chapter = { number = 0, title = "", length = 0, available = false }

local function seconds_to_minutes(total_seconds)
  local minutes = math.floor(total_seconds / 60)
  local seconds = total_seconds % 60
  return minutes, seconds
end

local function showChapterTitle()
  local message = ""
  if (chapter.available == true) then
    local minutes, seconds = seconds_to_minutes(chapter.length)
    local formatted_time = string.format("%02d:%02d", minutes, seconds)
    message = string.format("Chapter (%s): %s (%s)", chapter.number, chapter.title, formatted_time)
  else
    message = "No chapters available"
  end
  mp.osd_message(message)
end

local function chapter_info_update()
  local chapterList = mp.get_property_native("chapter-list")
  if not chapterList or #chapterList == 0 then
    chapter.available = false
    return
  end
  chapter.available = true
  local chapterCount = (mp.get_property_number("chapter-list/count") or 0)
  local currentChapterIndex = (mp.get_property_number("chapter") or 0) + 1
  chapter.number = currentChapterIndex
  local currentChapter = chapterList[currentChapterIndex]
  chapter.title = currentChapter.title or ""
  local nextChapterIndex = currentChapterIndex + 1
  if (nextChapterIndex > chapterCount) then
    local durationFull = mp.get_property_number("duration/full") or 0
    if durationFull ~= 0 then
      chapter.length = durationFull - currentChapter.time
    end
  else
    local nextChapter = chapterList[nextChapterIndex]
    chapter.length = nextChapter.time - currentChapter.time
  end
end

local function onChapterChange()
  chapter_info_update()
  showChapterTitle()
end

mp.register_event("file-loaded", chapter_info_update)
mp.observe_property("chapter", nil, function()
  onChapterChange()
end)
mp.add_key_binding(nil, "show-chapter-title", function()
  showChapterTitle()
end)
-- don't display the native OSD
-- when changing chapters as it overlaps
-- with ours but only sometimes
-- so it creates this janky feeling
mp.add_key_binding("PGUP", "next-chapter", function()
  mp.command("no-osd add chapter 1")
end)
mp.add_key_binding("PGDWN", "prev-chapter", function()
  mp.command("no-osd add chapter -1")
end)