feat(service): Adds Mattermost service

service/http/README.md

@@ -42,6 +42,7 @@ func main() {
 	// from the given subject and message.
 	httpService.AddReceivers(&http.Webhook{
 		URL:         "http://localhost:8080",
+		Header:      stdhttp.Header{},
 		ContentType: "text/plain",
 		Method:      stdhttp.MethodPost,
 		BuildPayload: func(subject, message string) (payload any) {

service/http/doc.go

@@ -40,6 +40,7 @@ Usage:
 			// from the given subject and message.
 			httpService.AddReceivers(&http.Webhook{
 				URL:         "http://localhost:8080",
+				Header:      stdhttp.Header{},
 				ContentType: "text/plain",
 				Method:      stdhttp.MethodPost,
 				BuildPayload: func(subject, message string) (payload any) {

service/mattermost/README.md

@@ -0,0 +1,80 @@
+# Mattermost Usage
+
+Ensure that you have already navigated to your GOPATH and installed the following packages:
+
+* `go get -u github.com/nikoksr/notify`
+
+## Steps for Mattermost Server
+
+These are general and very high level instructions
+
+1. Create a new Mattermost server / Join existing Mattermost server
+2. Make sure your Username/loginID have the OAuth permission scope(s): `create_post`
+3. Copy the *Channel ID* of the channel you want to post a message to. You can grab the *Channel ID* in channel info. example: *yfgstwuisnshydhd*
+4. Now you should be good to use the code below
+
+## Sample Code
+
+```go
+package main
+
+import (
+    "os"
+
+    "github.com/nikoksr/notify"
+    "github.com/nikoksr/notify/service/mattermost"
+)
+
+func main() {
+
+    // Init notifier
+    notifier := notify.New()
+    ctx := context.Background()
+
+    // Provide your Mattermost server url
+    mattermostService := mattermost.New("https://myserver.cloud.mattermost.com")
+
+    // Provide username as loginID and password to login into above server.
+    // NOTE: This generates auth token which will get expired, invoking this method again
+    // after expiry will generate new token and uses for further requests.
+    err := mattermostService.LoginWithCredentials(ctx, "someone@gmail.com", "somepassword")
+    if err != nil {
+        fmt.Println(err)
+        os.Exit(1)
+    }
+
+    // Passing a Mattermost channel/chat id as receiver for our messages.
+    // Where to send our messages.
+    mattermostService.AddReceivers("CHANNEL_ID")
+
+    // Tell our notifier to use the Mattermost service. You can repeat the above process
+    // for as many services as you like and just tell the notifier to use them.
+    notifier.UseServices(mattermostService)
+
+    // Add presend and postsend hooks that you need to execute before every requests and after
+    // every response respectively. Multiple presend and postsend are executed in the order defined here.
+    // refer service/http for the more info.
+    // PreSend hook
+    mattermostService.PreSend(func(req *stdhttp.Request) error {
+        log.Printf("Sending message to %s server", req.URL)
+        return nil
+    })
+    // PostSend hook
+    mattermostService.PostSend(func(req *stdhttp.Request, resp *stdhttp.Response) error {
+        log.Printf("Message sent to %s server with status %d", req.URL, resp.StatusCode)
+        return nil
+    })
+
+    // Send a message
+    err = notifier.Send(
+        ctx,
+        "Hello from notify :wave:\n",
+        "Message written in Go!",
+    )
+    if err != nil {
+        fmt.Println(err)
+        os.Exit(1)
+    }
+
+}
+```

service/mattermost/doc.go

@@ -0,0 +1,67 @@
+/*
+Package mattermost provides message notification integration for mattermost.com.
+
+Usage:
+
+	package main
+
+	import (
+		"os"
+
+		"github.com/nikoksr/notify"
+		"github.com/nikoksr/notify/service/mattermost"
+	)
+
+	func main() {
+
+		// Init notifier
+		notifier := notify.New()
+		ctx := context.Background()
+
+		// Provide your Mattermost server url
+		mattermostService := mattermost.New("https://myserver.cloud.mattermost.com")
+
+		// Provide username as loginID and password to login into above server.
+		// NOTE: This generates auth token which will get expired, invoking this method again
+		// after expiry will generate new token and uses for further requests.
+		err := mattermostService.LoginWithCredentials(ctx, "someone@gmail.com", "somepassword")
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+
+		// Passing a Mattermost channel/chat id as receiver for our messages.
+		// Where to send our messages.
+		mattermostService.AddReceivers("CHANNEL_ID")
+
+		// Tell our notifier to use the Mattermost service. You can repeat the above process
+		// for as many services as you like and just tell the notifier to use them.
+		notifier.UseServices(mattermostService)
+
+		// Add presend and postsend hooks that you need to execute before every requests and after
+		// every response respectively. Multiple presend and postsend are executed in the order defined here.
+		// refer service/http for the more info.
+		// PreSend hook
+		mattermostService.PreSend(func(req *stdhttp.Request) error {
+			log.Printf("Sending message to %s server", req.URL)
+			return nil
+		})
+		// PostSend hook
+		mattermostService.PostSend(func(req *stdhttp.Request, resp *stdhttp.Response) error {
+			log.Printf("Message sent to %s server with status %d", req.URL, resp.StatusCode)
+			return nil
+		})
+
+		// Send a message
+		err = notifier.Send(
+			ctx,
+			"Hello from notify :wave:",
+			"Message written in Go!",
+		)
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+	}
+*/
+package mattermost

service/mattermost/mattermost.go

@@ -0,0 +1,155 @@
+// Package mattermost provides message notification integration for mattermost.com.
+package mattermost
+
+import (
+	"context"
+	"io"
+	stdhttp "net/http"
+
+	"github.com/pkg/errors"
+
+	"github.com/nikoksr/notify/service/http"
+)
+
+//go:generate mockery --name=httpClient --output=. --case=underscore --inpackage
+type httpClient interface {
+	AddReceivers(wh ...*http.Webhook)
+	PreSend(prefn http.PreSendHookFn)
+	Send(ctx context.Context, subject, message string) error
+	PostSend(postfn http.PostSendHookFn)
+}
+
+// Service encapsulates the notify httpService client and contains mattermost channel ids.
+type Service struct {
+	loginClient   httpClient
+	messageClient httpClient
+	channelIDs    map[string]bool
+}
+
+// New returns a new instance of a Mattermost notification service.
+func New(url string) *Service {
+	httpService := setupMsgService(url)
+	return &Service{
+		setupLoginService(url, httpService),
+		httpService,
+		make(map[string]bool),
+	}
+}
+
+// LoginWithCredentials provides helper for authentication using Mattermost user/admin credentials.
+func (s *Service) LoginWithCredentials(ctx context.Context, loginID, password string) error {
+	// request login
+	if err := s.loginClient.Send(ctx, loginID, password); err != nil {
+		return errors.Wrapf(err, "failed login to Mattermost server")
+	}
+	return nil
+}
+
+// AddReceivers takes Mattermost channel IDs or Chat IDs and adds them to the internal channel ID list.
+// The Send method will send a given message to all these channels.
+func (s *Service) AddReceivers(channelIDs ...string) {
+	for i := range channelIDs {
+		s.channelIDs[channelIDs[i]] = true
+	}
+}
+
+// Send takes a message subject and a message body and send them to added channel ids.
+// you will need a 'create_post' permission for your username.
+// refer https://api.mattermost.com/ for more info
+func (s *Service) Send(ctx context.Context, subject, message string) error {
+	for id := range s.channelIDs {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+			// create post
+			if err := s.messageClient.Send(ctx, id, subject+"\n"+message); err != nil {
+				return errors.Wrapf(err, "failed to send message")
+			}
+		}
+	}
+	return nil
+}
+
+// PreSend adds a pre-send hook to the service. The hook will be executed before sending a request to a receiver.
+func (s *Service) PreSend(hook http.PreSendHookFn) {
+	s.messageClient.PreSend(hook)
+}
+
+// PostSend adds a post-send hook to the service. The hook will be executed after sending a request to a receiver.
+func (s *Service) PostSend(hook http.PostSendHookFn) {
+	s.messageClient.PostSend(hook)
+}
+
+// setups main message service for creating posts
+func setupMsgService(url string) *http.Service {
+	// create new http client for sending messages/notifications
+	httpService := http.New()
+
+	// add custom payload builder
+	httpService.AddReceivers(&http.Webhook{
+		URL:         url + "/api/v4/posts",
+		Header:      stdhttp.Header{},
+		ContentType: "application/json",
+		Method:      stdhttp.MethodPost,
+		BuildPayload: func(channelID, subjectAndMessage string) (payload any) {
+			return map[string]string{
+				"channel_id": channelID,
+				"message":    subjectAndMessage,
+			}
+		},
+	})
+
+	// add post-send hook for error checks
+	httpService.PostSend(func(req *stdhttp.Request, resp *stdhttp.Response) error {
+		if resp.StatusCode != stdhttp.StatusCreated {
+			b, _ := io.ReadAll(resp.Body)
+			return errors.New("failed to create post with status: " + resp.Status + " body: " + string(b))
+		}
+		return nil
+	})
+	return httpService
+}
+
+// setups login service to get token
+func setupLoginService(url string, msgService *http.Service) *http.Service {
+	// create another new http client for login request call.
+	httpService := http.New()
+
+	// append login path for the given mattermost server with custom payload builder.
+	httpService.AddReceivers(&http.Webhook{
+		URL:         url + "/api/v4/users/login",
+		Header:      stdhttp.Header{},
+		ContentType: "application/json",
+		Method:      stdhttp.MethodPost,
+		BuildPayload: func(loginID, password string) (payload any) {
+			return map[string]string{
+				"login_id": loginID,
+				"password": password,
+			}
+		},
+	})
+
+	// Add post-send hook to do error checks and log the response after it is received.
+	// Also extract token from response header and set it as part of pre-send hook of main http client for further requests.
+	httpService.PostSend(func(req *stdhttp.Request, resp *stdhttp.Response) error {
+		if resp.StatusCode != stdhttp.StatusOK {
+			b, _ := io.ReadAll(resp.Body)
+			return errors.New("login failed with status: " + resp.Status + " body: " + string(b))
+		}
+
+		// get token from header
+		token := resp.Header.Get("Token")
+		if token == "" {
+			return errors.New("received empty token")
+		}
+
+		// set token as pre-send hook
+		msgService.PreSend(func(req *stdhttp.Request) error {
+			req.Header.Set("Authorization", "Bearer "+token)
+			return nil
+		})
+		return nil
+	})
+	return httpService
+}