--[[
--  Music will get called with a string parameter indicating status.
--  Valid Parameters:
--    load    - game is loading.
--    land    - player landed.
--    takeoff - player took off.
--    combat  - Player just got a hostile on screen.
--    idle    - Current playing music ran out.
]]--
last = "idle"
function choose(str)
  -- Means to only change song if needed.
  if str == nil then
    str = "ambient"
  end

  if str == "load" then
    choose_load()

  elseif str == "intro" then
    choose_intro()

  elseif str == "credits" then
    choose_credits()

  elseif str == "land" then
    choose_land()

  elseif str == "takeoff" then
    choose_takeoff()

  elseif str == "ambient" then
    choose_ambient()

  elseif str == "combat" then
    choose_combat()

  elseif str == "idle" and last ~= "idle" then
    -- We'll play the same as last unless it was takeoff.
    if last == "takeoff" then
      choose_ambient()
    else
      choose(last)
    end
  end

  if str ~= "idle" then
    last = str -- Save the last string so we can use it.
  end
end

function checkIfPlayingOrStop(song)
  if music.isPlaying() then
    if music.current() ~= song then
      music.stop()
    end
    return true
  end
  return false
end

-- Loading songs.
function choose_load()
  load_song = "machina"
  -- Don't play again if needed.
  if checkIfPlayOrStop(load_song) then
    return
  end
  music.load(load_song)
  music.play()
  music.play()
end

-- Intro music.
function choose_intro()
  intro_song = "intro"
  -- Don't play again if needed.
  if checkIfPlayingOrStop(intro_song) then
    return
  end
  music.load(intro_song)
  music.play()
end

-- Credits music.
function choose_credits()
  credits_song = "empire1"
  -- Don't play again if needed.
  if checkIfPlayingOrStop(credits_song) then
    return
  end
  music.load(credits_song)
  music.play()
end

-- Landing songs.
function choose_land()
  planet = space.getPlanet()
  class = planet:class()

  if class == "M" then
    mus = "agriculture"
  elseif name == "Anecu" then -- TODO: We need a way to differenciate aquatics.
    mus = "ocean"
  elseif class == "P" then
    mus = "snow"
  else
    if planet:services() > 0 then
      mus = "cosmostation"
    else
      mus = "agriculture"
    end
  end

  music.load(mus)
  music.play()
end

-- Takeoff songs.
function choose_takeoff()
  -- No need to restart.
  if last == "takeoff" and music.isPlaying() then
    return
  end
  takeoff = { "liftoff", "launch2", "launch3chatstart" }
  music.load(takeoff[rnd.int(1, #takeoff)])
  music.play()
end

-- Save old data.
last_sysFaction   = nil
last_sysNebuDens  = nil
last_sysNebuVol   = nil
ambient_neutral = { "ambient2", "mission",
    "peace1", "peace2", "peace4", "peace6" }
-- Choose ambient songs.
function choose_ambient()
  force = true

  -- Check to see if we want to update.
  if music.isPlaying() then
    if last == "takeoff" then
      return
    elseif last == "ambient" then
      force = false
    end
  end

  -- Get information about the current system.
  sys = space.getSystem()
  factions = sys:faction()
  nebu_dens, nebu_vol = sys:nebulae()

  -- Check to see if changing faction zone.
  if not factions[last_sysFaction] then
    -- Table must not be empty.
    if next(factions) ~= nil then
      force = true
    end

    if force then
      -- Give first value to last faction.
      for k, v in pairs(factions) do
        last_sysFaction = k
        break
      end
    end
  end

  -- Check to see if entering nebulae.
  nebu = nebu_dens > 0
  if nebu ~= last_sysNebuDens then
    force = true
    last_sysNebuDens = nebu
  end

  -- Must be forced.
  if force then
    -- Choose the music, bias by faction first.
    add_neatral = false
    if factions["Collective"] then
      ambient = { "collective1" }
    elseif factions["Empire"] then
      ambient = { "empire1", "empire1", "empire1", "empire1" }
      add_neutral = true
    elseif nebu then
      ambient = { "ambient1", "ambient1", "ambient1", "ambient1" }
      add_neutral = true
    else
      ambient = ambient_neutral
    end

    -- Check if we need to append neutral ambient songs.
    if add_neutral then
      for k,v in pairs(ambient_neutral) do
        table.insert(ambient, v)
      end
    end

    -- Make sure it's not already in the list or that we have to stop the
    -- currently playing song.
    if music.isPlaying() then
      cur = music.current()
      for k,v in pairs(ambient) do
        if cur == v then
          return
        end
      end
      
      music.stop()
      return
    end

    -- Load music and play.
    music.load(ambient[rnd.int(1, #ambient)])
    music.play()
  end
end

-- Battle songs.
function choose_combat()
  -- Stop music first, but since it'll get saved it'll run this next.
  if music.isPlaying() then
    music.stop()
    return
  end

  -- Get some data about the system.
  sys = space.getSystem()
  nebu_dens, nebu_vol = sys:nebulae()

  nebu = nebu_dens > 0
  if nebu then
    combat = { "nebu_battle1" }
  else
    combat = { "galacticbattle" }
  end

  music.load(combat[rnd.int(1, #combat)])
  music.play()
end