-- ===================================================================

local function is_empty (s)
    if (s == nil) or (s == '') then return true end
    return false
end

-- ===================================================================

update_formspec_internal = function (pos)
    local this_node   = minetest.get_node (pos)
    if this_node == nil then return end

    local is_elevator = false
    if this_node.name == "travelnet:elevator" then
          is_elevator = true
    end

    local  meta = minetest.get_meta (pos)
    if not meta then return end

    local owner_name      = meta:get_string ("owner"           )
    local station_name    = meta:get_string ("station_name"    )
    local station_network = meta:get_string ("station_network" )

    if is_empty (owner_name      ) or
       is_empty (station_name    ) or
       is_empty (station_network ) then
        return
    end

    -- add name of station + network + owner + update-button

    local zusatzstr = ""
    local trheight  = "10"

    if this_node and this_node.name == "locked_travelnet:travelnet" then
        zusatzstr = "field[0.3,11;6,0.7;locks_sent_lock_command;Locked travelnet. Type /help for help:;]"
        trheight  = "11.5"
    end

    local update_msg = ""
    if not travelnet.enable_abm then
          update_msg = "label[6.3,0.0;Exit and left-punch to update]"
    end
    local formspec   = "size[12," .. trheight .. "]" ..

    -- 1st row
    "label[3.3,0.0;Travelnet-Box:]"                         ..
    update_msg                                              ..

    -- 2nd row
    "label[0.3,0.4;Name of this station:]"                  ..
    "label[3.3,0.4;" .. (station_name or "?") .. "]"        ..
    "label[6.3,0.4;Click on target to travel there]"        ..

    -- 3rd row
    "label[0.3,0.8;Assigned to Network:]"                   ..
    "label[3.3,0.8;" .. (station_network or "?") .. "]"     ..

    -- 4th row
    "label[0.3,1.2;Owned by:]"                              ..
    "label[3.3,1.2;" .. (owner_name or "?") .. "]"          ..
    "button_exit[6.3,1.2;3,0.8;station_dig;Remove station]" ..
    zusatzstr

    local x = 0;
    local y = 0;
    local i = 0;

    -- collect all station names in a table
    local stations = {};

    for k,v in pairs (travelnet.targets [owner_name][station_network]) do
        table.insert (stations, k)
    end

    if is_elevator then
        local ground_level = 1

        table.sort (stations,
            function (a,b) return
travelnet.targets [owner_name][station_network][a].pos.y >
travelnet.targets [owner_name][station_network][b].pos.y
end)
        -- find ground level
        local vgl_timestamp = 999999999999

        for index,k in ipairs (stations) do
            if not travelnet.targets [owner_name][station_network][k].timestamp then
                   travelnet.targets [owner_name][station_network][k].timestamp = os.time()
            end

            if( travelnet.targets [owner_name][station_network][k].timestamp < vgl_timestamp ) then
                vgl_timestamp = travelnet.targets [owner_name][station_network][k].timestamp;
                ground_level  = index
            end
        end

        for index,k in ipairs (stations) do
            if index == ground_level then
                travelnet.targets [owner_name][station_network][k].nr = 'G'
            else
                travelnet.targets [owner_name][station_network][k].nr = tostring (ground_level - index)
            end
        end
    else
        if travelnet.enable_legacy_sort then
            table.sort (stations,
                function (a,b) return
travelnet.targets [owner_name][station_network][a].timestamp <
travelnet.targets [owner_name][station_network][b].timestamp
            end)
        else
            table.sort (stations, function (a,b) return a < b end)
        end
    end

   -- If there are only 8 stations (plus this one)
   -- center them in the formspec
   --
   if #stations < 10 then x = 4 end

   for index,k in ipairs (stations) do

      -- check if there is an elevator door in front that
      -- needs to be opened
      --
      local open_door_cmd = false
      if k == station_name then
            open_door_cmd = true
      end

      if k ~= station_name or open_door_cmd then
         i = i+1

         -- new column
         if y == 8 then
            x = x+4
            y = 0
         end

         if( open_door_cmd ) then
            formspec = formspec .."button_exit["..(x)..","..(y+2.5)..";1,0.5;open_door;<>]"..
"label["..(x+0.9)..","..(y+2.35)..";"..tostring( k ).."]";
         elseif( is_elevator ) then
            formspec = formspec .."button_exit["..(x)..","..(y+2.5)..";1,0.5;target;"..tostring( travelnet.targets [owner_name][station_network][k].nr ).."]"..
"label["..(x+0.9)..","..(y+2.35)..";"..tostring( k ).."]";
         else
formspec = formspec .."button_exit["..(x)..","..(y+2.5)..";4,0.5;target;"..k.."]";
         end

         y = y+1
      end
   end

   meta:set_string ("formspec", formspec)

   meta:set_string ("infotext",
"Station '"        .. tostring (station_name   ) ..
"' on travelnet '" .. tostring (station_network) ..
"' (owned by "     .. tostring (owner_name     ) ..
") ready for usage. Right-click to travel, punch to update.")
end

-- ===================================================================

minetest.register_abm ({
    nodenames = { "group:travelnet" } ,
    catch_up  = false ,
    chance    = 1     ,
    interval  = 1     ,

    action = function (pos, node)
        local  meta = minetest.get_meta (pos)
        if not meta then return end

        local owner_name      = meta:get_string ("owner"           )
        local station_name    = meta:get_string ("station_name"    )
        local station_network = meta:get_string ("station_network" )

        if is_empty (owner_name      ) or
           is_empty (station_name    ) or
           is_empty (station_network ) then
            return
        end

        if not travelnet.targets or
           not travelnet.targets [owner_name] or
           not travelnet.targets [owner_name][station_network] or
           not travelnet.targets [owner_name][station_network][station_name] then

            travelnet.add_target (station_name,
                station_network, pos, owner_name, meta, owner_name)
        end

        update_formspec_internal (pos)
    end
})

-- ===================================================================
--                         "mapgen tour" code
-- ===================================================================

-- This  code implements a  mapgen-related  tool that is essential for
-- world  hosts  who'd  like to use "travelnet" in  captured copies of
-- worlds.  For more information,  see this mod's  copy  of "oldcoder.
-- txt".

-- ===================================================================

local tp          = {}
local pp          = minetest.string_to_pos
local tp_index    = 1
local emerge_busy = false

-- ===================================================================

local function tn_emerge_callback (blockpos, action, numleft, param)
    if collectgarbage ("count") > 307200 then collectgarbage() end
    minetest.log ("action", "tn_emerge: " .. numleft)
    if numleft ~= 0 then return end
    emerge_busy = false
end

-- ===================================================================

-- Optional: Add statements similar to the following here:
--
-- table.insert (tp, pp("-889.8,23.5,829"))
-- table.insert (tp, pp("-520,45.5,200.4"))
-- table.insert (tp, pp("-11093.2,15.5,11107.02"))
-- table.insert (tp, pp("-22200,4.5,22200"))
--
-- This will populate a table used by "/mapgentour". For more informa-
-- tion, see this mod's copy of "oldcoder.txt".

-- ===================================================================

travelnet.nexttn = function (player)
    if collectgarbage ("count") > 307200 then collectgarbage() end
    local name = player:get_player_name()

    if tp_index > #tp then
        minetest.chat_send_player (name, "End of list")
        return
    else
        minetest.chat_send_player (name,
            "#" .. tp_index .. " of " .. #tp)
    end

    if (emerge_busy) then
        minetest.chat_send_player (name, "Emerge is busy")
    else
        local delta = travelnet.mapgen_radius
        local pos   = tp [tp_index]
        tp_index    = tp_index + 1
        player:setpos (pos)

        local apos  = { x=pos.x - delta ,
                        y=pos.y - travelnet.mapgen_below ,
                        z=pos.z - delta }

        local bpos  = { x=pos.x + delta ,
                        y=pos.y + travelnet.mapgen_above ,
                        z=pos.z + delta }

        emerge_busy = true
        minetest.emerge_area (apos, bpos, tn_emerge_callback, nil)
    end

    minetest.after (5, travelnet.nexttn, player)
end

-- ===================================================================

minetest.register_chatcommand ("fixtn", {
    description = "Internal admin command" ,
    params      = ""                       ,
    privs       = { give = true }          ,

    func = function (name, params)
        local player = minetest.env:get_player_by_name (name)

        if tp_index > #tp then
            minetest.chat_send_player (name, "End of list")
            return
        else
            minetest.chat_send_player (name,
                "#" .. tp_index .. " of " .. #tp)
        end

        local pos = tp [tp_index]
        tp_index  = tp_index + 1
        player:setpos (pos)
    end
})

-- ===================================================================

minetest.register_chatcommand ("mapgentour" , {
    description  = "Internal admin command" ,
    params       = ""                       ,
    privs        = { give=true }            ,

    func = function (name, params)
        tp_index = 1
        local player = minetest.env:get_player_by_name (name)
        travelnet.nexttn (player)
    end
})