From cdc5e5d9eb19ec2550f99b38ed10c85375531438 Mon Sep 17 00:00:00 2001
From: Bastien Riviere <me@babariviere.com>
Date: Fri, 1 Sep 2023 19:06:04 +0200
Subject: [PATCH] feat: add bridge implementation

---
 bridge/bridge.go | 147 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 bridge/bridge.go

diff --git a/bridge/bridge.go b/bridge/bridge.go
new file mode 100644
index 0000000..68d1e7a
--- /dev/null
+++ b/bridge/bridge.go
@@ -0,0 +1,147 @@
+package bridge
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"io"
+	"log/slog"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+type Handler interface {
+	FormatNotification(r io.Reader) (Notification, error)
+}
+
+type NotificationError struct {
+	Code  int    `json:"code"`
+	Error string `json:"error"`
+}
+
+type Notification struct {
+	Title      string
+	Body       string
+	Priority   int
+	Tags       []string
+	IsMarkdown bool
+
+	topic string
+	auth  Auth
+}
+
+func (n Notification) Send(base string) error {
+	req, err := http.NewRequest("POST", base+"/"+n.topic, strings.NewReader(n.Body))
+	if err != nil {
+		return err
+	}
+
+	if n.IsMarkdown {
+		req.Header.Set("Content-Type", "text/markdown")
+	} else {
+		req.Header.Set("Content-Type", "text/plain")
+	}
+
+	if n.Title != "" {
+		req.Header.Set("Title", n.Title)
+	}
+
+	if n.Priority > 0 {
+		req.Header.Set("Priority", strconv.Itoa(n.Priority))
+	}
+
+	if len(n.Tags) > 0 {
+		req.Header.Set("Tags", strings.Join(n.Tags, ","))
+	}
+
+	if n.auth.Username != "" {
+		req.Header.Set("Authorization", n.auth.basic())
+	}
+
+	if n.auth.AccessToken != "" {
+		req.Header.Set("Authorization", n.auth.bearer())
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode >= 400 {
+		var e NotificationError
+		dec := json.NewDecoder(resp.Body)
+		dec.Decode(&e)
+
+		return errors.New(e.Error)
+	}
+
+	return nil
+}
+
+type Auth struct {
+	Username string
+	Password string
+
+	AccessToken string
+}
+
+func (a Auth) IsEmpty() bool {
+	return a.Username == "" && a.AccessToken == ""
+}
+
+func (a Auth) basic() string {
+	return "Basic " + base64.StdEncoding.EncodeToString([]byte(a.Username+":"+a.Password))
+}
+
+func (a Auth) bearer() string {
+	return "Bearer " + a.AccessToken
+}
+
+type Bridge struct {
+	baseURL string
+	topic   string
+	h       Handler
+	auth    Auth
+}
+
+func NewBridge(baseURL, topic string, handler Handler) Bridge {
+	return Bridge{
+		baseURL: baseURL,
+		topic:   topic,
+		h:       handler,
+	}
+}
+
+func (b *Bridge) WithAuth(auth Auth) {
+	b.auth = auth
+}
+
+func (b Bridge) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method != "POST" {
+		w.WriteHeader(http.StatusNotFound)
+		return
+	}
+
+	not, err := b.h.FormatNotification(r.Body)
+	defer r.Body.Close()
+
+	if err != nil {
+		slog.Error("failed to format notification")
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	not.topic = b.topic
+	not.auth = b.auth
+	if err = not.Send(b.baseURL); err != nil {
+		slog.Error("unable to send notification", "error", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	slog.Debug("notification sent with success")
+
+	w.WriteHeader(http.StatusOK)
+}