fix: add or replace MediaMTX paths idempotently (#54)

Sense/server/app/sense/adapters/mediamtx/client.go

@@ -20,6 +20,7 @@ type Source struct {
 }
 type PathStatus struct {
 	Name          string `json:"name"`
+	Exists        bool   `json:"exists"`
 	Ready         bool   `json:"ready"`
 	Readers       int    `json:"readers"`
 	BytesReceived int64  `json:"bytes_received"`
@@ -46,7 +47,15 @@ func (c *HTTPController) Apply(ctx context.Context, source Source) error {
 	}
 	payload := map[string]any{"source": parsed.String(), "sourceOnDemand": true, "rtspTransport": "tcp"}
 	data, _ := json.Marshal(payload)
-	endpoint := c.base + "/v3/config/paths/replace/" + url.PathEscape(source.Path)
+	configured, err := c.configured(ctx, source.Path)
+	if err != nil {
+		return err
+	}
+	action := "add"
+	if configured {
+		action = "replace"
+	}
+	endpoint := c.base + "/v3/config/paths/" + action + "/" + url.PathEscape(source.Path)
 	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewReader(data))
 	if err != nil {
 		return err
@@ -63,6 +72,39 @@ func (c *HTTPController) Apply(ctx context.Context, source Source) error {
 	}
 	return nil
 }
+
+func (c *HTTPController) configured(ctx context.Context, path string) (bool, error) {
+	endpoint := c.base + "/v3/config/paths/get/" + url.PathEscape(path)
+	deadline := time.Now().Add(5 * time.Second)
+	var res *http.Response
+	for {
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
+		if err != nil {
+			return false, err
+		}
+		res, err = c.client.Do(req)
+		if err == nil {
+			break
+		}
+		if !time.Now().Before(deadline) {
+			return false, fmt.Errorf("mediamtx control unavailable: %w", err)
+		}
+		select {
+		case <-ctx.Done():
+			return false, ctx.Err()
+		case <-time.After(100 * time.Millisecond):
+		}
+	}
+	defer res.Body.Close()
+	io.Copy(io.Discard, io.LimitReader(res.Body, 1<<20))
+	if res.StatusCode == http.StatusNotFound {
+		return false, nil
+	}
+	if res.StatusCode < 200 || res.StatusCode >= 300 {
+		return false, fmt.Errorf("mediamtx config lookup returned %d", res.StatusCode)
+	}
+	return true, nil
+}
 func (c *HTTPController) Status(ctx context.Context, path string) (PathStatus, error) {
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.base+"/v3/paths/get/"+url.PathEscape(path), nil)
 	if err != nil {
@@ -74,7 +116,7 @@ func (c *HTTPController) Status(ctx context.Context, path string) (PathStatus, e
 	}
 	defer res.Body.Close()
 	if res.StatusCode == http.StatusNotFound {
-		return PathStatus{Name: path}, nil
+		return PathStatus{Name: path, Exists: false}, nil
 	}
 	if res.StatusCode < 200 || res.StatusCode >= 300 {
 		return PathStatus{}, fmt.Errorf("mediamtx status returned %d", res.StatusCode)
@@ -88,5 +130,6 @@ func (c *HTTPController) Status(ctx context.Context, path string) (PathStatus, e
 	if err := json.NewDecoder(io.LimitReader(res.Body, 1<<20)).Decode(&raw); err != nil {
 		return PathStatus{}, err
 	}
-	return PathStatus{Name: raw.Name, Ready: raw.Ready, Readers: len(raw.Readers), BytesReceived: raw.BytesReceived}, nil
+	return PathStatus{Name: raw.Name, Exists: true, Ready: raw.Ready, Readers: len(raw.Readers), BytesReceived: raw.BytesReceived}, nil
 }
+