godns/hosts/hosts.go

package hosts

import (
	"github.com/miekg/dns"
	"time"
)

type HostMap map[string][]Host

type Host struct {
	Type uint16 `json:"type"`
	TTL time.Duration `json:"ttl"`
	Values []string `json:"values"`
}

func (h *Host) TypeString() string {
	return dns.TypeToString[h.Type]
}

type ProviderList struct {
	providers       []Provider
}

// Provider is an interface specifying a host source
// Each source should support AT LEAST List and Get, but can support Writer as well
type Provider interface {
	List() (HostMap, error)
	Get(queryType uint16, domain string) (*Host, error)
}

// Writer is an interface to modify hosts.
// Examples of this include Redis, Bolt, MySQL, etc.
type Writer interface {
	Set(domain string, host *Host) error
	Delete(domain string) error
}

type ProviderWriter interface {
	Provider
	Writer
}

func NewHosts(providers []Provider) *ProviderList {
	return &ProviderList{providers}
}

// List returns all results, merged into one HostMap
func (h *ProviderList) List() (HostMap, error) {
	hostMap := make(HostMap)

	for _, provider := range h.providers {
		hosts, err := provider.List()

		if err != nil {
			continue
		}

		for k, v := range hosts {
			if existing, ok := hostMap[k]; ok {
				existing = append(existing, v...)

				hostMap[k] = existing
			} else {
				hostMap[k] = v
			}
		}
	}

	return hostMap, nil
}

// Get Matches values to providers, loping each in order
func (h *ProviderList) Get(queryType uint16, domain string) (*Host, error) {
	var host *Host
	var err error

	for _, provider := range h.providers {
		host, err = provider.Get(queryType, domain)

		if host != nil {
			break
		}
	}

	return host, err
}

// Set invokes each provider, setting the host on the first one to return a nil error
func (h *ProviderList) Set(domain string, host *Host) (err error) {
	for _, provider := range h.providers {
		if writer, ok := provider.(Writer); ok {
			err = writer.Set(domain, host)

			if err == nil {
				return
			}
		}
	}

	err = errUnsupportedOperation
	return
}

// Delete invokes each provider, removing the host on the first one to return a nil error
func (h *ProviderList) Delete(domain string) (err error) {
	for _, provider := range h.providers {
		if writer, ok := provider.(Writer); ok {
			err = writer.Delete(domain)

			if err == nil {
				return
			}
		}
	}

	err = errUnsupportedOperation
	return
}