Split source_management.go along its CRUD seams (closes #274)

Pure code movement. Every declaration of
internal/handlers/source_management.go moves unchanged into one of:
webhook_list.go, webhook_create.go, webhook_detail.go, webhook_edit.go
and webhook_delete.go for the webhook pages; event_log.go for the event
log; entrypoint.go for the entrypoint handlers; target_create.go and
target.go for the target handlers; and shared.go for the helpers
several of them use. Only each file's package line and imports are new.

Model: opus-5-5

internal/handlers/webhook_list.go

@@ -0,0 +1,178 @@
+package handlers
+
+import (
+	"fmt"
+	"net/http"
+	"time"
+
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// WebhookListItem holds data for the webhook list view.
+type WebhookListItem struct {
+	database.Webhook
+
+	EntrypointCount         int
+	InactiveEntrypointCount int
+	TargetCount             int
+	InactiveTargetCount     int
+
+	// EventCount is how many events the webhook holds, LastEventAt
+	// when the newest arrived (nil before the first), and
+	// FailedLast24Hours how many of its deliveries failed in the last
+	// 24 hours. When the webhook's event database could not be read,
+	// EventsUnreadable is set and these three are not known.
+	EventCount        int64
+	LastEventAt       *time.Time
+	FailedLast24Hours int64
+	EventsUnreadable  bool
+}
+
+// HandleSourceList shows a list of user's webhooks.
+func (h *Handlers) HandleSourceList() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		userID, ok := h.getUserID(r)
+		if !ok {
+			http.Redirect(
+				w, r, "/pages/login", http.StatusSeeOther,
+			)
+
+			return
+		}
+
+		var webhooks []database.Webhook
+
+		err := h.db.DB().Where(
+			"user_id = ?", userID,
+		).Order("created_at DESC").Find(&webhooks).Error
+		if err != nil {
+			h.serverError(w, r, "failed to list webhooks", err)
+
+			return
+		}
+
+		items, err := h.buildWebhookListItems(webhooks)
+		if err != nil {
+			h.serverError(w, r, "failed to list webhooks", err)
+
+			return
+		}
+
+		data := map[string]any{
+			"Webhooks": items,
+		}
+
+		h.renderTemplate(w, r, "sources_list.html", data)
+	}
+}
+
+// buildWebhookListItems builds the list's entry for each webhook. It
+// fails when the main database cannot be read. A webhook whose event
+// database cannot be read is marked on its own entry, and the error is
+// logged.
+func (h *Handlers) buildWebhookListItems(
+	webhooks []database.Webhook,
+) ([]WebhookListItem, error) {
+	items := make([]WebhookListItem, len(webhooks))
+	since := time.Now().Add(-longWindow)
+
+	for i := range webhooks {
+		item := &items[i]
+		item.Webhook = webhooks[i]
+
+		var err error
+
+		item.EntrypointCount, item.InactiveEntrypointCount, err =
+			h.countWithInactive(&database.Entrypoint{}, item.ID)
+		if err != nil {
+			return nil, err
+		}
+
+		item.TargetCount, item.InactiveTargetCount, err =
+			h.countWithInactive(&database.Target{}, item.ID)
+		if err != nil {
+			return nil, err
+		}
+
+		// Opening an event database that does not exist would create
+		// it, and it would hold nothing to count.
+		if !h.dbMgr.DBExists(item.ID) {
+			continue
+		}
+
+		err = h.readListEventFigures(item, since)
+		if err != nil {
+			h.log.Error(
+				"failed to read webhook list figures",
+				"webhook_id", item.ID,
+				"error", err,
+			)
+
+			item.EventsUnreadable = true
+		}
+	}
+
+	return items, nil
+}
+
+// countWithInactive returns how many entrypoints or targets, as model
+// says, a webhook has, and how many of them are inactive.
+func (h *Handlers) countWithInactive(
+	model any, webhookID string,
+) (int, int, error) {
+	var active []bool
+
+	err := h.db.DB().Model(model).
+		Where("webhook_id = ?", webhookID).
+		Pluck("active", &active).Error
+	if err != nil {
+		return 0, 0, fmt.Errorf(
+			"reading active flags of webhook %s: %w", webhookID, err,
+		)
+	}
+
+	inactive := 0
+
+	for _, a := range active {
+		if !a {
+			inactive++
+		}
+	}
+
+	return len(active), inactive, nil
+}
+
+// readListEventFigures fills in the figures the list shows from the
+// webhook's event database, with the statistics pane's own queries:
+// the event count and last arrival from the event totals row, and the
+// deliveries that failed since the given time from the deliveries'
+// status index.
+func (h *Handlers) readListEventFigures(
+	item *WebhookListItem, since time.Time,
+) error {
+	webhookDB, err := h.dbMgr.GetDB(item.ID)
+	if err != nil {
+		return err
+	}
+
+	var totals database.EventTotals
+
+	err = webhookDB.Take(&totals).Error
+	if err != nil {
+		return fmt.Errorf("reading event totals: %w", err)
+	}
+
+	item.EventCount = totals.Events - totals.EventsRemoved
+	item.LastEventAt = totals.LastEventAt
+
+	byTarget, err := finishedByTarget(webhookDB, since)
+	if err != nil {
+		return err
+	}
+
+	for _, f := range byTarget {
+		item.FailedLast24Hours += f.Failed
+	}
+
+	return nil
+}