flood_fill.lua

local function clear_tile_teams()
    for i = 1, conf_map_num do
        local tile = g_map[i]
        local tile_type = tile.tile_type
        if tile_type ~= 'water' and
            tile_type ~= 'bridge' and
            tile_type ~= 'rocks' and
            tile_type ~= 'building' then
            tile.team = nil
        end
    end
end

local flood_fill
flood_fill = function(x, y, team, touched)
    local tile = get_tile(x, y)
    if tile == nil then return end
    local tile_type = tile.tile_type
    if tile_type == 'water' or
        tile_type == 'bridge' or
        tile_type == 'rocks' then
        return
    end

    if touched[tile] then return end
    touched[tile] = true

    if tile_type ~= 'building' then
        tile.team = team
    end

    local flood_fill = flood_fill
    flood_fill(x - 1, y - 1, team, touched)
    flood_fill(x + 1, y + 1, team, touched)
    flood_fill(x + 1, y - 1, team, touched)
    flood_fill(x - 1, y + 1, team, touched)
    flood_fill(x    , y - 1, team, touched)
    flood_fill(x    , y + 1, team, touched)
    flood_fill(x - 1, y    , team, touched)
    return flood_fill(x + 1, y, team, touched)
end

local function recalculate_tile_teams()
    clear_tile_teams()
    local touched = {}
    for i, building in ipairs(g_buildings) do
        if building.building_type == 'keep' then
            flood_fill(building.x, building.y, building.team, touched)
        end
    end
    touched = {}
    for i = 1, #g_water_border_indexes do
        local x, y = make_xy(g_water_border_indexes[i])
        flood_fill(x, y, nil, touched)
    end
end