cmd/resolver: implement command to add new record to hosts file

The command has the following signature,

  resolver hosts.d rr add <name> <domain> <value>

Given the hosts file name "hosts" and domain "my.hosts" with value
"127.0.0.1", it will add new line "127.0.0.1 my.hosts" to the "hosts"
file.
If the domain name already exists, the new record will be appended
instead of replaced.

5 files changed, 116 insertions, 1 deletions

diff --git a/_doc/resolver.adoc b/_doc/resolver.adoc
index 98bb5e3..f0d40de 100644
--- a/_doc/resolver.adoc
+++ b/_doc/resolver.adoc
@@ -171,6 +171,16 @@ Get the content of hosts file inside the hosts.d directory by file name.
 --
 
 
+hosts.d rr add <name> <domain> <value>::
++
+--
+Insert a new record and save it to the hosts file identified by
+"name".
+If the domain name already exists, the new record will be appended
+instead of replaced.
+--
+
+
 == EXIT STATUS
 
 Upon exit and success +resolver+ will return 0, or 1 otherwise.
@@ -259,6 +269,17 @@ Get the content of hosts file named "myhosts" inside the hosts.d directory,
 	  }
 	]
 
+Add new record "127.0.0.1 my.hosts" to hosts file named "hosts",
+
+	$ resolver hosts.d rr add hosts my.hosts 127.0.0.1
+	{
+	  "Value": "127.0.0.1",
+	  "Name": "my.hosts",
+	  "Type": 1,
+	  "Class": 1,
+	  "TTL": 604800
+	}
+
 
 == AUTHOR
 
diff --git a/_sys/usr/share/man/man1/resolver.1.gz b/_sys/usr/share/man/man1/resolver.1.gz
index 635cd25..61dc96c 100644
--- a/_sys/usr/share/man/man1/resolver.1.gz
+++ b/_sys/usr/share/man/man1/resolver.1.gz
diff --git a/client.go b/client.go
index bfea21a..cc4399e 100644
--- a/client.go
+++ b/client.go
@@ -348,3 +348,35 @@ func (cl *Client) HostsdGet(name string) (listrr []*dns.ResourceRecord, err erro
 	}
 	return listrr, nil
 }
+
+// HostsdRecordAdd add new resource record to the hosts file.
+func (cl *Client) HostsdRecordAdd(hostsName, domain, value string) (record *dns.ResourceRecord, err error) {
+	var (
+		logp = "HostsdRecordAdd"
+		res  = libhttp.EndpointResponse{
+			Data: &record,
+		}
+		params = url.Values{}
+
+		resb []byte
+	)
+
+	params.Set(paramNameName, hostsName)
+	params.Set(paramNameDomain, domain)
+	params.Set(paramNameValue, value)
+
+	_, resb, err = cl.PostForm(apiHostsdRR, nil, params)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", logp, err)
+	}
+
+	err = json.Unmarshal(resb, &res)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", logp, err)
+	}
+	if res.Code != http.StatusOK {
+		return nil, fmt.Errorf("%s: %d %s", logp, res.Code, res.Message)
+	}
+
+	return record, nil
+}
diff --git a/cmd/resolver/main.go b/cmd/resolver/main.go
index 284c521..2c40b90 100644
--- a/cmd/resolver/main.go
+++ b/cmd/resolver/main.go
@@ -21,11 +21,13 @@ const (
 	cmdHostsd = "hosts.d"
 	cmdQuery  = "query"
 
+	subCmdAdd     = "add"
 	subCmdCreate  = "create"
 	subCmdDelete  = "delete"
 	subCmdDisable = "disable"
 	subCmdEnable  = "enable"
 	subCmdGet     = "get"
+	subCmdRR      = "rr"
 	subCmdRemove  = "remove"
 	subCmdSearch  = "search"
 	subCmdUpdate  = "update"
@@ -197,6 +199,13 @@ hosts.d get <name>
 	Get the content of hosts file inside the hosts.d directory by file
 	name.
 
+hosts.d rr add <name> <domain> <value>
+
+	Insert a new record and save it to the hosts file identified by
+	"name".
+	If the domain name already exists, the new record will be appended
+	instead of replaced.
+
 
 ==  Examples
 
@@ -280,5 +289,15 @@ Get the content of hosts file named "myhosts" inside the hosts.d directory,
 	    "TTL": 604800
 	  }
 	]
-`)
+
+Add new record "127.0.0.1 my.hosts" to hosts file named "hosts",
+
+	$ resolver hosts.d rr add hosts my.hosts 127.0.0.1
+	{
+	  "Value": "127.0.0.1",
+	  "Name": "my.hosts",
+	  "Type": 1,
+	  "Class": 1,
+	  "TTL": 604800
+	}`)
 }
diff --git a/cmd/resolver/resolver.go b/cmd/resolver/resolver.go
index 1c55669..62ce953 100644
--- a/cmd/resolver/resolver.go
+++ b/cmd/resolver/resolver.go
@@ -319,11 +319,54 @@ func (rsol *resolver) doCmdHostsd(args []string) {
 
 		fmt.Println(string(jsonb))
 
+	case subCmdRR:
+		rsol.doCmdHostsdRecord(args[1:])
+
 	default:
 		log.Fatalf("resolver: %s: unknown sub command: %s", rsol.cmd, subCmd)
 	}
 }
 
+func (rsol *resolver) doCmdHostsdRecord(args []string) {
+	if len(args) == 0 {
+		log.Fatalf("resolver: %s %s %s: missing arguments", rsol.cmd, cmdHostsd, subCmdRR)
+	}
+
+	var (
+		subCmd = strings.ToLower(args[0])
+
+		resc   *rescached.Client
+		record *dns.ResourceRecord
+		jsonb  []byte
+		err    error
+	)
+
+	switch subCmd {
+	case subCmdAdd:
+		args = args[1:]
+		if len(args) < 3 {
+			log.Fatalf("resolver: missing arguments")
+		}
+
+		resc = rsol.newRescachedClient()
+		record, err = resc.HostsdRecordAdd(args[0], args[1], args[2])
+		if err != nil {
+			log.Fatalf("resolver: %s", err)
+		}
+
+		jsonb, err = json.MarshalIndent(record, "", "  ")
+		if err != nil {
+			log.Fatalf("resolver: %s", err)
+		}
+
+		fmt.Println(string(jsonb))
+
+	case subCmdDelete:
+	default:
+		log.Fatalf("resolver: %s %s: unknown command %s", rsol.cmd, subCmdRR, subCmd)
+	}
+}
+
 func (rsol *resolver) doCmdQuery(args []string) {
 	var (
 		maxAttempts = defAttempts