feat: check unused package (#232)

* feat: check unused package

update edganiukov/fcm to appleboy/go-fcm

* update readme

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* update comment

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

vendor/github.com/appleboy/go-fcm/client.go

@@ -0,0 +1,133 @@
+package fcm
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+)
+
+const (
+	// DefaultEndpoint contains endpoint URL of FCM service.
+	DefaultEndpoint = "https://fcm.googleapis.com/fcm/send"
+)
+
+var (
+	// ErrInvalidAPIKey occurs if API key is not set.
+	ErrInvalidAPIKey = errors.New("client API Key is invalid")
+)
+
+// Client abstracts the interaction between the application server and the
+// FCM server via HTTP protocol. The developer must obtain an API key from the
+// Google APIs Console page and pass it to the `Client` so that it can
+// perform authorized requests on the application server's behalf.
+// To send a message to one or more devices use the Client's Send.
+//
+// If the `HTTP` field is nil, a zeroed http.Client will be allocated and used
+// to send messages.
+type Client struct {
+	apiKey   string
+	client   *http.Client
+	endpoint string
+}
+
+// NewClient creates new Firebase Cloud Messaging Client based on API key and
+// with default endpoint and http client.
+func NewClient(apiKey string, opts ...Option) (*Client, error) {
+	if apiKey == "" {
+		return nil, ErrInvalidAPIKey
+	}
+	c := &Client{
+		apiKey:   apiKey,
+		endpoint: DefaultEndpoint,
+		client:   &http.Client{},
+	}
+	for _, o := range opts {
+		if err := o(c); err != nil {
+			return nil, err
+		}
+	}
+
+	return c, nil
+}
+
+// Send sends a message to the FCM server without retrying in case of service
+// unavailability. A non-nil error is returned if a non-recoverable error
+// occurs (i.e. if the response status is not "200 OK").
+func (c *Client) Send(msg *Message) (*Response, error) {
+	// validate
+	if err := msg.Validate(); err != nil {
+		return nil, err
+	}
+
+	// marshal message
+	data, err := json.Marshal(msg)
+	if err != nil {
+		return nil, err
+	}
+
+	return c.send(data)
+}
+
+// SendWithRetry sends a message to the FCM server with defined number of
+// retrying in case of temporary error.
+func (c *Client) SendWithRetry(msg *Message, retryAttempts int) (*Response, error) {
+	// validate
+	if err := msg.Validate(); err != nil {
+		return nil, err
+	}
+	// marshal message
+	data, err := json.Marshal(msg)
+	if err != nil {
+		return nil, err
+	}
+
+	resp := new(Response)
+	err = retry(func() error {
+		var err error
+		resp, err = c.send(data)
+		return err
+	}, retryAttempts)
+	if err != nil {
+		return nil, err
+	}
+
+	return resp, nil
+}
+
+// send sends a request.
+func (c *Client) send(data []byte) (*Response, error) {
+	// create request
+	req, err := http.NewRequest("POST", c.endpoint, bytes.NewBuffer(data))
+	if err != nil {
+		return nil, err
+	}
+
+	// add headers
+	req.Header.Add("Authorization", fmt.Sprintf("key=%s", c.apiKey))
+	req.Header.Add("Content-Type", "application/json")
+
+	// execute request
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, connectionError(err.Error())
+	}
+	defer resp.Body.Close()
+
+	// check response status
+	if resp.StatusCode != http.StatusOK {
+		if resp.StatusCode >= http.StatusInternalServerError {
+			return nil, serverError(fmt.Sprintf("%d error: %s", resp.StatusCode, resp.Status))
+		}
+		return nil, fmt.Errorf("%d error: %s", resp.StatusCode, resp.Status)
+	}
+
+	// build return
+	response := new(Response)
+	if err := json.NewDecoder(resp.Body).Decode(response); err != nil {
+		return nil, err
+	}
+
+	return response, nil
+}