feat: implement ntfy-discord bridge in Go

- SSE subscription to ntfy with auto-reconnect
- Discord webhook integration with embed formatting
- Priority to color mapping, tag to emoji conversion
- Native HashiCorp Vault support (Kubernetes + token auth)
- Hot reload secrets via fsnotify or Vault polling
- Prometheus metrics (/metrics endpoint)
- Health/ready endpoints for Kubernetes probes
- Comprehensive unit tests and fuzz tests
- Multi-stage Docker build (~10MB scratch image)
- CI/CD pipeline for Gitea Actions

internal/discord/webhook.go

@@ -0,0 +1,203 @@
+package discord
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"git.daviestechlabs.io/daviestechlabs/ntfy-discord/internal/ntfy"
+)
+
+// Priority to Discord embed color mapping
+var priorityColors = map[int]int{
+	5: 15158332, // Red - Max/Urgent
+	4: 15105570, // Orange - High
+	3: 3066993,  // Blue - Default
+	2: 9807270,  // Gray - Low
+	1: 12370112, // Light Gray - Min
+}
+
+// Tag to emoji mapping
+var tagEmojis = map[string]string{
+	"white_check_mark": "✅",
+	"heavy_check_mark": "✅",
+	"check":            "✅",
+	"x":                "❌",
+	"skull":            "❌",
+	"warning":          "⚠️",
+	"rotating_light":   "🚨",
+	"rocket":           "🚀",
+	"package":          "📦",
+	"tada":             "🎉",
+	"fire":             "🔥",
+	"bug":              "🐛",
+	"wrench":           "🔧",
+	"gear":             "⚙️",
+	"lock":             "🔒",
+	"key":              "🔑",
+	"bell":             "🔔",
+	"mega":             "📢",
+	"eyes":             "👀",
+	"sos":              "🆘",
+	"no_entry":         "⛔",
+	"construction":     "🚧",
+}
+
+// Embed represents a Discord embed
+type Embed struct {
+	Title       string  `json:"title,omitempty"`
+	Description string  `json:"description,omitempty"`
+	Color       int     `json:"color,omitempty"`
+	Fields      []Field `json:"fields,omitempty"`
+	Timestamp   string  `json:"timestamp,omitempty"`
+	Footer      *Footer `json:"footer,omitempty"`
+}
+
+// Field represents a Discord embed field
+type Field struct {
+	Name   string `json:"name"`
+	Value  string `json:"value"`
+	Inline bool   `json:"inline,omitempty"`
+}
+
+// Footer represents a Discord embed footer
+type Footer struct {
+	Text string `json:"text"`
+}
+
+// WebhookPayload is the Discord webhook request body
+type WebhookPayload struct {
+	Embeds []Embed `json:"embeds"`
+}
+
+// Client sends messages to Discord webhooks
+type Client struct {
+	httpClient *http.Client
+}
+
+// NewClient creates a new Discord webhook client
+func NewClient() *Client {
+	return &Client{
+		httpClient: &http.Client{
+			Timeout: 30 * time.Second,
+		},
+	}
+}
+
+// Send converts an ntfy message to Discord format and sends it
+func (c *Client) Send(ctx context.Context, webhookURL string, msg ntfy.Message) error {
+	if webhookURL == "" {
+		return fmt.Errorf("no webhook URL configured")
+	}
+
+	embed := c.buildEmbed(msg)
+	payload := WebhookPayload{
+		Embeds: []Embed{embed},
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return fmt.Errorf("marshal payload: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, webhookURL, bytes.NewReader(body))
+	if err != nil {
+		return fmt.Errorf("create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("send request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	// Handle rate limiting
+	if resp.StatusCode == http.StatusTooManyRequests {
+		retryAfter := resp.Header.Get("Retry-After")
+		if retryAfter != "" {
+			if seconds, err := strconv.Atoi(retryAfter); err == nil {
+				slog.Warn("Discord rate limited", "retry_after", seconds)
+				time.Sleep(time.Duration(seconds) * time.Second)
+				return c.Send(ctx, webhookURL, msg) // Retry
+			}
+		}
+		return fmt.Errorf("rate limited")
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 1024))
+		return fmt.Errorf("unexpected status %d: %s", resp.StatusCode, string(respBody))
+	}
+
+	return nil
+}
+
+func (c *Client) buildEmbed(msg ntfy.Message) Embed {
+	// Get color from priority
+	color := priorityColors[3] // Default
+	if msg.Priority >= 1 && msg.Priority <= 5 {
+		color = priorityColors[msg.Priority]
+	}
+
+	// Build title with emoji prefix
+	title := msg.Title
+	if title == "" {
+		title = msg.Topic
+	}
+	emoji := c.extractEmoji(msg.Tags)
+	if emoji != "" {
+		title = emoji + " " + title
+	}
+
+	// Build timestamp
+	timestamp := ""
+	if msg.Time > 0 {
+		timestamp = time.Unix(msg.Time, 0).UTC().Format(time.RFC3339)
+	}
+
+	embed := Embed{
+		Title:       title,
+		Description: msg.Message,
+		Color:       color,
+		Timestamp:   timestamp,
+		Footer:      &Footer{Text: "ntfy"},
+	}
+
+	// Add topic as field
+	if msg.Topic != "" {
+		embed.Fields = append(embed.Fields, Field{
+			Name:   "Topic",
+			Value:  msg.Topic,
+			Inline: true,
+		})
+	}
+
+	// Add click URL if present
+	if msg.Click != "" {
+		embed.Fields = append(embed.Fields, Field{
+			Name:   "Link",
+			Value:  msg.Click,
+			Inline: false,
+		})
+	}
+
+	return embed
+}
+
+func (c *Client) extractEmoji(tags []string) string {
+	for _, tag := range tags {
+		tag = strings.ToLower(tag)
+		if emoji, ok := tagEmojis[tag]; ok {
+			return emoji
+		}
+	}
+	return ""
+}