local math_random = math.random

script.on_init(function()
    local nauvis = game.surfaces[1]

    local mgs = nauvis.map_gen_settings
    mgs.autoplace_controls.water = {
        frequency = 6,
        richness = 1,
        size = 6
    }
    mgs.property_expression_names = {
        elevation = 'elevation_lakes'
    }
    nauvis.map_gen_settings = mgs
    nauvis.clear(true)
end)

script.on_event(defines.events.on_chunk_generated, function(event)
    local surface = event.surface
    local create_entity = surface.create_entity
    local set_hidden_tile = surface.set_hidden_tile
    local can_place_entity = surface.can_place_entity

    local entities = {}
    local tiles = {}

    for _, tile in pairs(surface.find_tiles_filtered{ area = event.area }) do
        local position = tile.position

        if tile.collides_with('water_tile') then
            tiles[#tiles + 1] = { name = 'landfill', position = position }
            set_hidden_tile(position, 'water')
            entities[#entities + 1] = { name = 'coal', position = position, enable_tree_removal = false, amount = math_random(10, 100) }
        else
            entities[#entities + 1] = { name = 'iron-ore', position = position, enable_tree_removal = false, amount = math_random(1000, 2000) }
        end

        if math_random() > 0.90 then
            entities[#entities + 1] = { name = 'tree-0'..math_random(1, 9), position = position, enable_tree_removal = false }
        elseif math_random() > 0.95 then
            entities[#entities + 1] = { name = 'big-rock', position = position, enable_tree_removal = false }
        end
    end

    surface.set_tiles(tiles, true)

    for _, entity in pairs(entities) do
        if can_place_entity(entity) then
            create_entity(entity)
        end
    end
end)