Feature: Allow overwriting the Host header for all request.

This is to work around situations where DNS isn't available (yet) but Gotify is behind a reverse-proxy which is routing traffic based on Hostnames. For these scenarios, we can simply use the static IP as the Endpoint and overwrite the `Host` header to what the reverse proxy requires to correctly route the request.

client.go

@@ -15,12 +15,32 @@ type AuthedGotifyClient struct {
 	auth   runtime.ClientAuthInfoWriter
 }
 
-func NewAuthedClient(endpoint string, username string, password string) (*AuthedGotifyClient, error) {
+type OverwriteHostTransport struct {
+	Host string
+	Next http.RoundTripper
+}
+
+func (hot *OverwriteHostTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	req.Host = hot.Host
+	return hot.Next.RoundTrip(req)
+}
+
+func wrapWithHost(host string, wrap http.RoundTripper) http.RoundTripper {
+	return &OverwriteHostTransport{Host: host, Next: wrap}
+}
+
+func NewAuthedClient(endpoint string, username string, password string, host *string) (*AuthedGotifyClient, error) {
 	url, err := url.Parse(endpoint)
 	if err != nil {
 		return nil, err
 	}
-	client := gotify.NewClient(url, &http.Client{})
+
+	transport := http.DefaultTransport
+	if host != nil {
+		transport = wrapWithHost(*host, transport)
+	}
+
+	client := gotify.NewClient(url, &http.Client{Transport: transport})
 	auth := auth.BasicAuth(username, password)
 
 	return &AuthedGotifyClient{client: client, auth: auth}, nil

client_test.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/gotify/go-api-client/v2/client/application"
+)
+
+const (
+	testHost = "my.coolapp.local"
+	// the httptest.NewServer always listens on this address
+	localHost = "127.0.0.1"
+)
+
+func TestClientHostOverwrite(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		if req.Host != testHost {
+			t.Errorf("Expected \"Host\" to be %q, got %q", testHost, req.Host)
+		}
+
+		// Return valid response for test endpoint
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprintln(w, "[]")
+	}))
+	defer ts.Close()
+
+	host := testHost
+	client, err := NewAuthedClient(ts.URL, "test", "test", &host)
+	if err != nil {
+		t.Fatalf("Could not construct client: %v", err.Error())
+	}
+
+	params := application.NewGetAppsParams()
+	_, err = client.client.Application.GetApps(params, client.auth)
+	if err != nil {
+		t.Fatalf("Error during test request: %v", err.Error())
+	}
+}
+
+func TestClientHostDefault(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		if !strings.HasPrefix(req.Host, localHost) {
+			t.Errorf("Expected \"Host\" to start with %q, got %q", localHost, req.Host)
+		}
+
+		// Return valid response for test endpoint
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprintln(w, "[]")
+	}))
+	defer ts.Close()
+
+	client, err := NewAuthedClient(ts.URL, "test", "test", nil)
+	if err != nil {
+		t.Fatalf("Could not construct client: %v", err.Error())
+	}
+
+	params := application.NewGetAppsParams()
+	_, err = client.client.Application.GetApps(params, client.auth)
+	if err != nil {
+		t.Fatalf("Error during test request: %v", err.Error())
+	}
+}

docs/index.md

@@ -16,11 +16,18 @@ For each client that wants to read messages from Gotify, you want a new `gotify_
 ## Example Usage
 
 ```terraform
+# Required configuration
 provider "gotify" {
   endpoint = "http://my.gotify.local" # or GOTIFY_ENDPOINT
   username = "admin"                  # or GOTIFY_USERNAME
   password = "admin"                  # or GOTIFY_PASSWORD
 }
+
+# When Gotify is behind a reverse proxy and DNS isn't setup yet
+provider "gotify" {
+  endpoint    = "http://192.168.1.4" # public, static IP of deployment
+  host_header = "my.gotify.local"    # Host header expected by reverse proxy
+}
 ```
 
 <!-- schema generated by tfplugindocs -->
@@ -29,5 +36,6 @@ provider "gotify" {
 ### Optional
 
 - `endpoint` (String) Endpoint with Protocol to send requests to.
+- `host_header` (String) This is useful when Gotify is deployed behind a reverse proxy and this provider is used in your infrastructure setup where DNS might not be available yet. You can then set the endpoint to an IP address and the Host to what your reverse Proxy expects.
 - `password` (String, Sensitive) The Password to authenticate against the server. Gotify's default "admin" user has "admin" as their password.
 - `username` (String) The Username to authenticate against the server. Gotify has a default "admin" user

examples/provider/provider.tf

@@ -1,5 +1,13 @@
+# Required configuration
 provider "gotify" {
   endpoint = "http://my.gotify.local" # or GOTIFY_ENDPOINT
   username = "admin"                  # or GOTIFY_USERNAME
   password = "admin"                  # or GOTIFY_PASSWORD
 }
+
+# When Gotify is behind a reverse proxy and DNS isn't setup yet
+provider "gotify" {
+  endpoint    = "http://192.168.1.4" # public, static IP of deployment
+  host_header = "my.gotify.local"    # Host header expected by reverse proxy
+}
+

provider.go

@@ -22,9 +22,10 @@ type GotifyProvider struct {
 
 // Map Terraform HCL schema to Go types.
 type GotifyProviderModel struct {
-	Endpoint types.String `tfsdk:"endpoint"`
-	Username types.String `tfsdk:"username"`
-	Password types.String `tfsdk:"password"`
+	Endpoint   types.String `tfsdk:"endpoint"`
+	HostHeader types.String `tfsdk:"host_header"`
+	Username   types.String `tfsdk:"username"`
+	Password   types.String `tfsdk:"password"`
 }
 
 func (p *GotifyProvider) Metadata(_ context.Context, _ provider.MetadataRequest, resp *provider.MetadataResponse) {
@@ -52,6 +53,11 @@ func (p *GotifyProvider) Schema(_ context.Context, _ provider.SchemaRequest, res
 				Sensitive:   true,
 				Description: "The Password to authenticate against the server. Gotify's default \"admin\" user has \"admin\" as their password.",
 			},
+			"host_header": schema.StringAttribute{
+				Optional:            true,
+				Description:         "Allows overwriting the Host header in all HTTP requests made to the Gotify REST API.",
+				MarkdownDescription: "This is useful when Gotify is deployed behind a reverse proxy and this provider is used in your infrastructure setup where DNS might not be available yet. You can then set the endpoint to an IP address and the Host to what your reverse Proxy expects.",
+			},
 		},
 	}
 }
@@ -107,7 +113,7 @@ func (p *GotifyProvider) Configure(ctx context.Context, req provider.ConfigureRe
 		return
 	}
 
-	client, err := NewAuthedClient(endpoint, username, password)
+	client, err := NewAuthedClient(endpoint, username, password, model.HostHeader.ValueStringPointer())
 	if err != nil {
 		resp.Diagnostics.AddError(
 			"Failed while constructing client", err.Error(),