require "erb"
require "netaddr"
require "pathname"
require "fileutils"

module Lxc
  class Container
    def initialize(data, name:, ipv4: nil, ipv6: nil, ula: nil, **options)
      @data = data
      @data["network"] ||= {}
      @data["network"][name] = {}

      zone = @data["zone"] || {}
      @ipv4_subnet = NetAddr::CIDR.create(zone["v4_subnet"] || "192.168.10.0/24")
      @ipv6_subnet = NetAddr::CIDR.create(zone["v6_subnet"] || "fd7d:aed0:18aa::/48")
      @ula_subnet  = NetAddr::CIDR.create(zone["ula_subnet"] || "fdc5:bdb8:b81::/48")

      @container_root = Pathname.new(zone["lxc_root"]).join(name)

      network = data["network"]
      @name = name
      @ipv4 = ipv4 || find_address(@ipv4_subnet, collect_subnets(network, "ipv4"))
      @ipv6 = ipv6 || find_address(@ipv6_subnet, collect_subnets(network, "ipv6"))
      @ula  = ula  || find_address(@ula_subnet,  collect_subnets(network, "ula"))
      @options = options
    end

    def write_config(config_path)
      c = @data["network"][@name] || {}
      c["ipv4"] = NetAddr::CIDR.create(@ipv4).to_s(Short: true)
      c["ipv6"] = NetAddr::CIDR.create(@ipv6).to_s(Short: true)
      c["ula"] = NetAddr::CIDR.create(@ula).to_s(Short: true)
      c["group"] = @options[:group] if @options[:group]
      c["vars"] = @options[:vars] if @options[:vars]

      opts = @options.merge(name: @name,
                            ipv4: format_address(@ipv4, @ipv4_subnet.to_i(:netmask)),
                            ipv6: format_address(@ipv6, @ipv6_subnet.to_i(:netmask)),
                            ula: format_address(@ula, @ula_subnet.to_i(:netmask)))

      config_dir = File.dirname(config_path)
      local_conf = File.join(config_dir, "local.conf")
      unless File.exists?(local_conf)
        FileUtils.touch(local_conf)
      end
      opts[:local_conf] = local_conf
      opts[:global_conf] = @data["zone"]["lxc-config"]

      fstab = @container_root.join("fstab")
      opts[:fstab]  = fstab if File.exists?(fstab)
      opts[:rootfs] = @data["zone"]["shared_rootfs"] || opts[:rootfs] || @container_root.join("rootfs")

      templ = Template.new(CONFIG_ROOT.join("hooks", "templates", "config.erb"))
      templ.write(config_path, opts)
    end

    private
    def format_address(address, netmask)
      NetAddr::CIDR.create(address, Mask: netmask).desc(IP: true, Short: true)
    end

    def collect_subnets(network, type)
      addrs = []
      network.each do |k,v|
        if v[type]
          addrs << NetAddr::CIDR.create(v[type])
        end
      end
      addrs
    end

    def find_address(subnet, assigned_subnets)
      subnet.enumerate(Limit: 1E4, Short: true)[1..1E4].each do |cidr|
        assigned = assigned_subnets.find { |s| s.contains?(cidr) || s == cidr }
        return cidr unless assigned
      end
    end
  end
end