add(cepgo): import github.com/cloudsigma/cepgo

third_party/github.com/cloudsigma/cepgo/cepgo.go

@@ -0,0 +1,186 @@
+// Cepko implements easy-to-use communication with CloudSigma's VMs through a
+// virtual serial port without bothering with formatting the messages properly
+// nor parsing the output with the specific and sometimes confusing shell tools
+// for that purpose.
+//
+// Having the server definition accessible by the VM can be useful in various
+// ways. For example it is possible to easily determine from within the VM,
+// which network interfaces are connected to public and which to private
+// network. Another use is to pass some data to initial VM setup scripts, like
+// setting the hostname to the VM name or passing ssh public keys through
+// server meta.
+//
+// Example usage:
+//
+//   package main
+//
+//   import (
+//           "fmt"
+//
+//           "github.com/cloudsigma/cepgo"
+//   )
+//
+//   func main() {
+//           c := cepgo.NewCepgo()
+//           result, err := c.Meta()
+//           if err != nil {
+//                   panic(err)
+//           }
+//           fmt.Printf("%#v", result)
+//   }
+//
+// Output:
+//
+//   map[string]string{
+//   	"optimize_for":"custom",
+//   	"ssh_public_key":"ssh-rsa AAA...",
+//   	"description":"[...]",
+//   }
+//
+// For more information take a look at the Server Context section API Docs:
+// http://cloudsigma-docs.readthedocs.org/en/latest/server_context.html
+package cepgo
+
+import (
+	"bufio"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"runtime"
+
+	"github.com/tarm/goserial"
+)
+
+const (
+	requestPattern = "<\n%s\n>"
+	EOT            = '\x04' // End Of Transmission
+)
+
+var (
+	SerialPort string = "/dev/ttyS1"
+	Baud       int    = 115200
+)
+
+// Sets the serial port. If the operating system is windows CloudSigma's server
+// context is at COM2 port, otherwise (linux, freebsd, darwin) the port is
+// being left to the default /dev/ttyS1.
+func init() {
+	if runtime.GOOS == "windows" {
+		SerialPort = "COM2"
+	}
+}
+
+// The default fetcher makes the connection to the serial port,
+// writes given query and reads until the EOT symbol.
+func fetchViaSerialPort(key string) ([]byte, error) {
+	config := &serial.Config{Name: SerialPort, Baud: Baud}
+	connection, err := serial.OpenPort(config)
+	if err != nil {
+		return nil, err
+	}
+
+	query := fmt.Sprintf(requestPattern, key)
+	if _, err := connection.Write([]byte(query)); err != nil {
+		return nil, err
+	}
+
+	reader := bufio.NewReader(connection)
+	answer, err := reader.ReadBytes(EOT)
+	if err != nil {
+		return nil, err
+	}
+
+	return answer[0 : len(answer)-1], nil
+}
+
+// Queries to the serial port can be executed only from instance of this type.
+// The result from each of them can be either interface{}, map[string]string or
+// a single in case of single value is returned. There is also a public metod
+// who directly calls the fetcher and returns raw []byte from the serial port.
+type Cepgo struct {
+	fetcher func(string) ([]byte, error)
+}
+
+// Creates a Cepgo instance with the default serial port fetcher.
+func NewCepgo() *Cepgo {
+	cepgo := new(Cepgo)
+	cepgo.fetcher = fetchViaSerialPort
+	return cepgo
+}
+
+// Creates a Cepgo instance with custom fetcher.
+func NewCepgoFetcher(fetcher func(string) ([]byte, error)) *Cepgo {
+	cepgo := new(Cepgo)
+	cepgo.fetcher = fetcher
+	return cepgo
+}
+
+// Fetches raw []byte from the serial port using directly the fetcher member.
+func (c *Cepgo) FetchRaw(key string) ([]byte, error) {
+	return c.fetcher(key)
+}
+
+// Fetches a single key and tries to unmarshal the result to json and returns
+// it. If the unmarshalling fails it's safe to assume the result it's just a
+// string and returns it.
+func (c *Cepgo) Key(key string) (interface{}, error) {
+	var result interface{}
+
+	fetched, err := c.FetchRaw(key)
+	if err != nil {
+		return nil, err
+	}
+
+	err = json.Unmarshal(fetched, &result)
+	if err != nil {
+		return string(fetched), nil
+	}
+	return result, nil
+}
+
+// Fetches all the server context. Equivalent of c.Key("")
+func (c *Cepgo) All() (interface{}, error) {
+	return c.Key("")
+}
+
+// Fetches only the object meta field and makes sure to return a proper
+// map[string]string
+func (c *Cepgo) Meta() (map[string]string, error) {
+	rawMeta, err := c.Key("/meta/")
+	if err != nil {
+		return nil, err
+	}
+
+	return typeAssertToMapOfStrings(rawMeta)
+}
+
+// Fetches only the global context and makes sure to return a proper
+// map[string]string
+func (c *Cepgo) GlobalContext() (map[string]string, error) {
+	rawContext, err := c.Key("/global_context/")
+	if err != nil {
+		return nil, err
+	}
+
+	return typeAssertToMapOfStrings(rawContext)
+}
+
+// Just a little helper function that uses type assertions in order to convert
+// a interface{} to map[string]string if this is possible.
+func typeAssertToMapOfStrings(raw interface{}) (map[string]string, error) {
+	result := make(map[string]string)
+
+	dictionary, ok := raw.(map[string]interface{})
+	if !ok {
+		return nil, errors.New("Received bytes are formatted badly")
+	}
+
+	for key, rawValue := range dictionary {
+		if value, ok := rawValue.(string); ok {
+			result[key] = value
+		} else {
+			return nil, errors.New("Server context metadata is formatted badly")
+		}
+	}
+	return result, nil
+}