-----------------‐---------------------------------------------------------------------------------
--                Advanced Vehicles II API by Andrey01
-----‐---------------------------------------------------------------------------------------------

vehicles = {}

gravity = -9.8

local showed_seats_fspecs = {}     --  pair: ["playername"] and objectref


-----‐---------------------------------------------------------------------
--   API functions
---------------------------------------------------------------------------
vehicles.set_gravity = function(self)
     local obj = self.object
     local acc = obj:get_acceleration()
     local vel = obj:get_velocity()
     local m = minetest.registered_entities[self.name].mass
     obj:set_acceleration({x=acc.x, y=acc.y+(m*gravity-vel.y^2)/m, z=acc.z})   -- vel.y^2 is an air resistance
end

vehicles.register_vehicle = function(name, veh_props, spawner_item_props)
     minetest.register_entity(MOD_NAME .. ":" .. name, {
     	vehicle_type = veh_props.vehicle_type,
     	physical = true,
         mass = veh_props.mass,     -- in kgs
         collide_with_objects = true,
         collisionbox = veh_props.bounding_box or {-0.5, 0.0, -0.5, 0.5, 1.0, 0.5},
         selectionbox = veh_props.bounding_box or {-0.5, 0.0, -0.5, 0.5, 1.0, 0.5},
         visual = veh_props.visual,
         visual_size = veh_props.visual_size or {x=1, y=1, z=1},
         mesh = veh_props.visual == "mesh" and veh_props.model,
         textures = veh_props.textures or {},
         seats = veh_props.seats,
         on_activate = function(self, staticdata, dtime_s)
               local props = minetest.registered_entities[self.name]
               self.seats = props.seats
         end,
         on_step = function(self, dtime)
               vehicles.set_gravity(self)
         end,
         on_death = function(self, killer)
               for i, sdata in ipairs(self.seats) do
                      vehicles.get_out(self, i)
               end
               for n, obj in pairs(showed_seats_fspecs) do
                      if obj == self.object then
                           vehicles.close_seats_formspec(self, n, MOD_NAME .. ":vehicle_seats")
                      end
               end
          end,
          on_rightclick = function(self, clicker)
                vehicles.show_seats_formspec(self, MOD_NAME .. ":vehicle_seats", clicker:get_player_name())
          end

     })

     minetest.register_craftitem(MOD_NAME .. ":" .. name, {
     	description = spawner_item_props.description or "",
         inventory_image = spawner_item_props.inv_image or "",
         on_place = function(itemstack, placer, pointed_thing)
                 if pointed_thing.type =="node" and pointed_thing.above.y >= pointed_thing.under.y then
                       minetest.add_entity(pointed_thing.above, itemstack:get_name())
                 end
         end
      })
end

vehicles.show_seats_formspec = function(self, formspec_name, playername)
      local seats_n = #self.seats
      minetest.debug(seats_n)
      local buts_space_w, buts_space_h = 0.2, 0.3     -- space between buttons along width and height
      local int = math.modf(seats_n/8)
      local columns_n = (seats_n % 8 == 0 and int) or int + 1
      local w_sbut, h_sbut = 2, 0.5
      local fspec_size_w = columns_n * w_sbut + (columns_n + 1) * buts_space_w
      local fspec_size_h = 8 * h_sbut + 9 * buts_space_h + 2    -- + 2 is a space for label text
      local is_player_sit = vehicles.is_player_sit(minetest.get_player_by_name(playername))
      fspec_size_h = (is_player_sit and fspec_size_h + 2) or fspec_size_h    -- if player sits the vehicle, heighten the formspec window still at 2 units
      local fspec_t = {
      	"formspec_version[3]",
          "size[" .. fspec_size_w .. "," .. fspec_size_h .. "]",
          "real_coordinates[true]",
          "label[2,1;" .. minetest.formspec_escape("Select a vacant seat inside the vehicle below:") .. "]"
      }
      local formspec = table.concat(fspec_t)

      local bpos_x, bpos_y = buts_space_w, buts_space_h
      for i = 1, seats_n do
          formspec = formspec .. "button[" .. bpos_x .. "," .. bpos_y .. ";" .. w_sbut .. "," .. h_sbut .. ";seat_" .. i .. ";" .. minetest.formspec_escape("Seat #" .. i) .. "]"
          bpos_x = ((i - 1) % 8 == 0) and bpos_x + w_sbut + buts_space_w
          bpos_y = (((i - 1) % 8 == 0) and buts_space_h) or bpos_y + h_sbut + buts_space_h
      end

      formspec = (is_player_sit and (formspec .. "button[" .. fspec_size_w / 2 - w_sbut / 2 .. ", " .. fspec_size_h - 1.5 .. ";" .. w_sbut .. ", " .. h_sbut .. ";get_out;" .. minetest.formspec_escape("Get out") .. "]")) or formspec
      minetest.debug(formspec)
      showed_seats_fspecs[playername] = self.object
      minetest.show_formspec(playername, formspec_name, formspec)
end

vehicles.sit = function(self, player, seat_id, seat_anim)     -- seat_id is an id of a seat table of 'self.seats'
      local sel_seat = self.seats[seat_id]
      local plname = player:get_player_name()
      if type(sel_seat.is_busy) == "string" and sel_seat.is_busy ~= plname then
            minetest.chat_send_player(plname, "Seat #" .. seat_id .. " is busy by " .. sel_seat.is_busy .. "!")
            return
      end

      if sel_seat.type == "driver" and seat_anim then
            local plmeta = player:get_meta()
            plmeta:set_string("previous_anim", minetest.serialize(player:get_animation()))
            player:set_animation(seat_anim.frange, seat_anim.fspeed, seat_anim.fblend, seat_anim.floop)
      end

      local vrot = self.object:get_rotation()
      player:set_attach(self, "", sel_seat.pos, {x=0, y=0, z=0})

      sel_seat.is_busy = plname
end

vehicles.get_out = function(self, seat_id)
      local seat = self.seats[seat_id]
      if not seat.is_busy then return end

      player:set_detach()

      if seat.type == "driver" then
           local player = minetest.get_player_by_name(self.is_busy)
           local plmeta = player:get_meta()
           local saved_anim = minetest.deserialize(plmeta:get_string("previous_anim"))
           if saved_anim then
                  player:set_animation(saved_anim.frame_range, seat_anim.frame_speed, seat_anim.frame_blend, seat_anim.frame_loop)
                  plmeta:set_string("previous_anim", "")
           end
      end

      seat.is_busy = nil
end

vehicles.on_formspec_event = function(player, formname, fields)
      if formname ~= MOD_NAME .. ":vehicle_seats" then
             return
      end

      local plname = player:get_player_name()
      local obj = showed_seats_fspecs[plname]
      local self = obj:get_luaentity()
      if self then
           for i, sdata in ipairs(self.seats) do
                  local but_name = "seat_" .. i
                  if fields[but_name] then
                       vehicles.close_seats_formspec(self, plname, formname, i, "sit")
                       return true
                  end
           end

           if fields["get_out"] then
                vehicles.close_seats_formspec(self, plname, formname, i, "get_out")
                return true
           end
      else     --   supposed that vehicle is died while the player is viewing the formspec
           vehicles.close_seats_formspec(self, plname, formname)
      end
end




-------‐---------------------------------------------------------------------
--   Helper functions
-----------------------------------------------------------------------------
vehicles.is_player_sit = function(player)
      local self = player:get_attach()
      if not self then return false end

      local name = player:get_player_name()
      for i, sdata in ipairs(self.seats) do
             if sdata.is_busy == name then
                  return true
             end
      end

      return false
end

--   'seat_id' is optional
--   'action' is supposed what to do with the player after closing (sit or go out off the vehicle)  [optional]
vehicles.close_seats_formspec = function(self, playername, formname, seat_id, action)
      minetest.close_formspec(playername, formname)
      showed_seats_fspecs[playername] = nil

      local player = minetest.get_player_by_name(playername)
      if action == "sit" then
           vehicles.sit(self, player, seat_id)
      elseif action == "get_out" then
           vehicles.get_out(self, seat_id)
      end
end


-----------------------------------------------------------------------------
--   Callback Registrations
-----------------------------------------------------------------------------
minetest.register_on_player_receive_fields(vehicles.on_formspec_event)