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

module Lxc
  class Container
    def initialize(data, name:, ipv4: nil, ipv6: nil,
                   dn42_ipv4: nil, dn42_ipv6: 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")

      if subnet = zone["dn42_ipv4_subnet"]
        @dn42_ipv4_netmask = NetAddr::CIDR.create(subnet).to_i(:netmask)
      else
        @dn42_ipv4_netmask = 24
      end

      if subnet = zone["dn42_ipv6_subnet"]
        @dn42_ipv6_netmask = NetAddr::CIDR.create(subnet).to_i(:netmask)
      else
        @dn42_ipv6_netmask = 48
      end

      network = data["network"]
      @name = name
      @ipv4 = ipv4 ||= ipv4 || find_address(@ipv4_subnet, collect_subnets(network, "ipv4"))
      @ipv6 = ipv6 ||= find_address(@ipv6_subnet, collect_subnets(network, "ipv6"))
      @dn42_ipv4 = dn42_ipv4
      @dn42_ipv6 = dn42_ipv6
      @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["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)))
      if @dn42_ipv4
        opts[:dn42_ipv4] = format_address(dn42_ipv6, dn42_ipv4_netmask)
        c["dn42_ipv4"] = NetAddr::CIDR.create(@dn42_ipv4).to_s(Short: true)
      end

      if @dn42_ipv6
        opts[:dn42_ipv6] = format_address(dn42_ipv4, dn42_ipv6_netmask)
        c["dn42_ipv6"] = NetAddr::CIDR.create(@dn42_ipv6).to_s(Short: true)
      end

      templ = Template.new(CONFIG_ROOT.join("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)
      network.map do |k,v|
        NetAddr::CIDR.create(v[type]) if v[type]
      end.compact
    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