Keep what was typed when a target or webhook edit is refused (closes #381)

A refused save on the target edit page answered with a bare text page, losing the form and everything typed, and the webhook edit page came back with the stored values instead of the submitted ones. A refused target edit now shows the edit form again with the reason above it and every value submitted, with the same status codes as before; a refused webhook edit keeps the submitted name, description and retention. Target edits use the same validation as new targets, with no second copy; an encoding or database failure stays a logged 500. The browser test covers a refused save on both pages, and its main function is now a plain list of checks.

Model: opus-5-5

internal/handlers/target_edit.go

@@ -3,6 +3,7 @@ package handlers
 import (
 	"errors"
 	"net/http"
+	"strconv"
 
 	"github.com/go-chi/chi"
 	"sneak.berlin/go/webhooker/internal/database"
@@ -13,10 +14,13 @@ import (
 const targetEditTemplate = "target_edit.html"
 
 // tmplKeyTarget is the template data key for the target being
-// edited, and tmplKeyMaxTimeout for the timeout ceiling the form
-// tells the user about.
+// edited, tmplKeyTargetForm for the values its form shows, and
+// tmplKeyMaxTimeout for the timeout ceiling the form tells the user
+// about. The add target form on the webhook page takes its values
+// under the same key as the edit form.
 const (
 	tmplKeyTarget     = "Target"
+	tmplKeyTargetForm = "TargetForm"
 	tmplKeyMaxTimeout = "MaxTimeout"
 )
 
@@ -28,20 +32,19 @@ const configUnreadableMessage = "The stored configuration for this " +
 	"target could not be read. Enter the values below; saving " +
 	"replaces the stored configuration."
 
-// targetEditView is the display model for the target edit page.
+// targetEditView is the display model for the target edit page: the
+// target's row fields as stored. The values the form shows, the
+// UNMASKED configuration among them, come separately, as a
+// targetFormInput.
 //
-// It carries the target's row fields alongside its UNMASKED
-// configuration, and deliberately omits database.Target's raw
-// Config blob: the form renders named fields, and giving the
-// template the blob as well would put an unreviewed second path to
-// the credential on the page.
+// It deliberately omits database.Target's raw Config blob: the form
+// renders named fields, and giving the template the blob as well
+// would put an unreviewed second path to the credential on the page.
 type targetEditView struct {
-	ID         string
-	Name       string
-	Type       database.TargetType
-	Active     bool
-	MaxRetries int
-	Config     delivery.TargetConfigForm
+	ID     string
+	Name   string
+	Type   database.TargetType
+	Active bool
 }
 
 // HandleTargetEdit shows the form to edit a target.
@@ -73,7 +76,18 @@ func (h *Handlers) HandleTargetEdit() http.HandlerFunc {
 			msg = configUnreadableMessage
 		}
 
-		h.renderTargetEdit(w, r, webhook, target, cfg, msg)
+		form := targetFormInput{
+			Name:       target.Name,
+			URL:        cfg.URL,
+			Headers:    cfg.Headers,
+			Timeout:    cfg.Timeout,
+			MaxRetries: strconv.Itoa(target.MaxRetries),
+			Expiry:     cfg.Expiry,
+		}
+
+		h.renderTargetEdit(
+			w, r, webhook, target, form, msg, http.StatusOK,
+		)
 	}
 }
 
@@ -101,11 +115,12 @@ func (h *Handlers) HandleTargetEditSubmit() http.HandlerFunc {
 	}
 }
 
-// applyTargetEdit validates and saves target edits.
+// applyTargetEdit validates and saves target edits. A refused save
+// shows the edit form again with the values submitted and the reason.
 //
-// The submitted configuration goes through buildTargetConfig, the
-// same builder the create path uses, so an edited destination is
-// SSRF-validated exactly as a new one is.
+// The submission goes through setTargetFromForm, as a new target
+// does, so an edited destination is SSRF-validated exactly as a new
+// one is.
 //
 // The target's type is not editable. Each type stores a different
 // configuration shape and its delivery history is recorded against
@@ -118,16 +133,13 @@ func (h *Handlers) applyTargetEdit(
 	webhook database.Webhook,
 	target *database.Target,
 ) {
-	name := r.PostFormValue("name")
-	if name == "" {
-		http.Error(w, "Name is required", http.StatusBadRequest)
+	in := targetFormInputFrom(r)
 
-		return
-	}
+	// edited is the target as the submission leaves it; target stays
+	// as stored, for the page shown again when the save is refused.
+	edited := *target
 
-	configJSON, errMsg, err := h.buildTargetConfig(
-		r.Context(), target.Type, targetFormInputFrom(r),
-	)
+	errMsg, err := h.setTargetFromForm(r.Context(), &edited, in)
 	if err != nil {
 		h.serverError(w, r, "failed to encode target config", err)
 
@@ -135,45 +147,26 @@ func (h *Handlers) applyTargetEdit(
 	}
 
 	if errMsg != "" {
-		http.Error(w, errMsg, http.StatusBadRequest)
+		h.renderTargetEdit(
+			w, r, webhook, target, in, errMsg, http.StatusBadRequest,
+		)
 
 		return
 	}
 
-	// Retries are offered only by the forms for target types that
-	// retry, so an absent field means "this form does not edit
-	// retries" rather than "set them to zero". Reading it
-	// unconditionally would silently disable retries on any target
-	// saved from a form that does not render the input.
-	//
-	// A field that IS submitted but does not parse is a 400, through
-	// the same validator the create path uses. It is rejected before
-	// anything is written, so a typo cannot destroy the retry count
-	// the target is already delivering with.
-	if r.PostForm.Has("max_retries") {
-		retries, ok := targetMaxRetries(w, r, target.MaxRetries)
-		if !ok {
-			return
-		}
-
-		target.MaxRetries = retries
-	}
-
-	oldName := target.Name
-	target.Name = name
-	target.Config = configJSON
-
 	// A new name renames the archive file before it is saved (see
 	// delivery.Engine.Rename). If either step fails, it goes back to
 	// the name that is still stored.
-	err = h.renameTargetArchive(target, webhook.Name, oldName, name)
+	err = h.renameTargetArchive(
+		target, webhook.Name, target.Name, edited.Name,
+	)
 	if err == nil {
-		err = h.db.DB().Save(target).Error
+		err = h.db.DB().Save(&edited).Error
 	}
 
 	if err != nil {
 		restoreErr := h.renameTargetArchive(
-			target, webhook.Name, name, oldName,
+			target, webhook.Name, edited.Name, target.Name,
 		)
 		if restoreErr != nil {
 			h.log.Error(
@@ -184,8 +177,8 @@ func (h *Handlers) applyTargetEdit(
 		}
 
 		if errors.Is(err, delivery.ErrArchiveNameTaken) {
-			http.Error(
-				w,
+			h.renderTargetEdit(
+				w, r, webhook, target, in,
 				"Not saved: "+err.Error()+
 					". Move that archive out of the data directory, "+
 					"its .db together with any -wal and -shm beside "+
@@ -222,15 +215,17 @@ func (h *Handlers) renameTargetArchive(
 	return h.archives.Rename(target.ID, webhookName, newName)
 }
 
-// renderTargetEdit renders the target edit page with an optional
-// error message.
+// renderTargetEdit renders the target edit page for the target as
+// stored, its form showing form's values, with an optional error
+// message above it.
 func (h *Handlers) renderTargetEdit(
 	w http.ResponseWriter,
 	r *http.Request,
 	webhook database.Webhook,
 	target *database.Target,
-	cfg delivery.TargetConfigForm,
+	form targetFormInput,
 	errMsg string,
+	status int,
 ) {
 	// The template calls Webhook methods, which take pointer
 	// receivers; html/template cannot address a value stored in a
@@ -238,18 +233,17 @@ func (h *Handlers) renderTargetEdit(
 	data := map[string]any{
 		tmplKeyWebhook: &webhook,
 		tmplKeyTarget: targetEditView{
-			ID:         target.ID,
-			Name:       target.Name,
-			Type:       target.Type,
-			Active:     target.Active,
-			MaxRetries: target.MaxRetries,
-			Config:     cfg,
+			ID:     target.ID,
+			Name:   target.Name,
+			Type:   target.Type,
+			Active: target.Active,
 		},
+		tmplKeyTargetForm: form,
 		tmplKeyMaxTimeout: delivery.MaxTargetTimeoutSeconds,
 		tmplKeyError:      errMsg,
 	}
 
-	h.renderTemplate(w, r, targetEditTemplate, data)
+	h.renderTemplateStatus(w, r, targetEditTemplate, data, status)
 }
 
 // ownedTarget resolves the request's sourceID and targetID