refactor(http): consolidate UI list handler filter parsing into BaseFilter (#173)

* refactor(http): consolidate UI list handler filter parsing into BaseFilter

Introduce filters.BaseFilter with shared Q, Enabled, Sort, Dir fields
and a ParseBaseFilter() helper that centralizes common query param
parsing logic. Three filter types now embed BaseFilter instead of
duplicating the same trim/parse patterns:

- iocsFilter: delegates Q and Enabled parsing to BaseFilter
- sitesFilter: delegates Q, Enabled, Sort, Dir parsing to BaseFilter
- sourcesFilters: delegates Q parsing to BaseFilter (keeps IncludeTests)

Removes ~40 lines of duplicated filter parsing code across three files.
All existing tests pass; golangci-lint reports 0 issues.

* chore: remove code-reduction-findings.md from PR

* chore: remove AGENT.md from PR

* refactor(http): use WrapListFetcher for secrets and alert sinks handlers

Add WrapListFetcher generic adapter in list_handler.go that adapts
a service List(ctx, limit, offset) call into a ListFetcher with
consistent pagination bounds and error logging.

Replace inline Fetcher closures in ui_secrets.go and
ui_alert_sinks.go with WrapListFetcher calls, removing ~20 lines
of duplicated boilerplate.

Author: cawalch

services/merrymaker-go/internal/http/filters.go

@@ -5,6 +5,37 @@ import (
 	"strings"
 )
 
+// BaseFilter holds common filter fields shared across list pages.
+// Embed this struct in page-specific filters to avoid duplicating parsing logic.
+type BaseFilter struct {
+	Q       string
+	Enabled *bool
+	Sort    string
+	Dir     string
+}
+
+// ParseBaseFilter parses common fields from URL query parameters.
+// Callers should embed the result and then override/extend with page-specific fields.
+func ParseBaseFilter(q url.Values) BaseFilter {
+	var enabledPtr *bool
+	switch strings.TrimSpace(q.Get("enabled")) {
+	case StrTrue, "1":
+		b := true
+		enabledPtr = &b
+	case StrFalse, "0":
+		b := false
+		enabledPtr = &b
+	}
+	sort, dir := ParseSortParam(q, "sort", "dir")
+
+	return BaseFilter{
+		Q:       strings.TrimSpace(q.Get("q")),
+		Enabled: enabledPtr,
+		Sort:    sort,
+		Dir:     dir,
+	}
+}
+
 const (
 	// StrTrue represents the string "true" for boolean query parameters.
 	StrTrue = "true"

services/merrymaker-go/internal/http/list_handler.go

@@ -2,6 +2,7 @@ package httpx
 
 import (
 	"context"
+	"log/slog"
 	"net/http"
 	"net/url"
 )
@@ -11,6 +12,31 @@ import (
 // Maintains ≤3 parameters per project constraints.
 type ListFetcher[T any] func(ctx context.Context, pg pageOpts) ([]T, error)
 
+// WrapListFetcher adapts a service List method with signature (ctx, limit, offset) -> ([]T, error)
+// into a ListFetcher that handles pagination bounds and error logging.
+//
+// Usage:
+//
+//	Fetcher: WrapListFetcher(h.SecretSvc.List, h.logger(), "failed to load secrets for UI"),
+func WrapListFetcher[T any](
+	listFunc func(ctx context.Context, limit, offset int) ([]T, error),
+	logger *slog.Logger,
+	msg string,
+) ListFetcher[T] {
+	return func(ctx context.Context, pg pageOpts) ([]T, error) {
+		limit, offset := pg.LimitAndOffset()
+		items, err := listFunc(ctx, limit, offset)
+		if err != nil {
+			logger.Error(msg,
+				"error", err,
+				"page", pg.Page,
+				"page_size", pg.PageSize,
+			)
+		}
+		return items, err
+	}
+}
+
 // FilterParser is a function type for parsing URL query parameters into filter data.
 // It takes url.Values and returns the parsed filter of type F, or an error if parsing fails.
 // The error allows the handler to show meaningful validation errors for invalid filter params.

services/merrymaker-go/internal/http/ui_alert_sinks.go

@@ -56,18 +56,9 @@ func (h *UIHandlers) AlertSinks(w http.ResponseWriter, r *http.Request) {
 		Handler: h,
 		W:       w,
 		R:       r,
-		Fetcher: func(ctx context.Context, pg pageOpts) ([]*model.HTTPAlertSink, error) {
-			limit, offset := pg.LimitAndOffset()
-			items, err := h.Sinks.List(ctx, limit, offset)
-			if err != nil {
-				h.logger().Error("failed to load alert sinks for UI",
-					"error", err,
-					"page", pg.Page,
-					"page_size", pg.PageSize,
-				)
-			}
-			return items, err
-		},
+		Fetcher: WrapListFetcher(func(ctx context.Context, limit, offset int) ([]*model.HTTPAlertSink, error) {
+			return h.Sinks.List(ctx, limit, offset)
+		}, h.logger(), "failed to load alert sinks for UI"),
 		BasePath:     alertSinksBasePath,
 		PageMeta:     alertSinkListMeta(),
 		ItemsKey:     "AlertSinks",

services/merrymaker-go/internal/http/ui_iocs.go

@@ -12,9 +12,9 @@ const errMsgUnableLoadIOCs = "Unable to load IOCs."
 
 // iocsFilter holds filter parameters for the IOCs list view.
 type iocsFilter struct {
-	Type    *model.IOCType
-	Enabled *bool
-	Search  *string
+	BaseFilter
+	Type   *model.IOCType
+	Search *string
 }
 
 // IOCs serves the IOCs list page, HTMX-aware.
@@ -85,23 +85,17 @@ func (h *UIHandlers) fetchIOCsWithFilters(ctx context.Context, f iocsFilter, pg
 
 // parseIOCsFilter parses filter parameters from query string.
 func parseIOCsFilter(q url.Values) (iocsFilter, error) {
-	var f iocsFilter
+	f := iocsFilter{BaseFilter: ParseBaseFilter(q)}
 
 	// Type filter
 	if typeStr := q.Get("type"); typeStr != "" {
 		iocType := model.IOCType(typeStr)
 		f.Type = &iocType
 	}
 
-	// Enabled filter
-	if enabledStr := q.Get("enabled"); enabledStr != "" {
-		enabled := enabledStr == StrTrue || enabledStr == "1"
-		f.Enabled = &enabled
-	}
-
-	// Search filter
-	if search := q.Get("q"); search != "" {
-		f.Search = &search
+	// Search filter (use BaseFilter.Q, but keep pointer form for backward compat)
+	if f.Q != "" {
+		f.Search = &f.Q
 	}
 
 	return f, nil
@@ -127,14 +121,10 @@ func (h *UIHandlers) enrichIOCsData() DataEnricher[*model.IOC, iocsFilter] {
 		}
 		builder.With("EnabledFilter", enabledFilter)
 
-		searchQuery := ""
-		if f.Search != nil {
-			searchQuery = *f.Search
-		}
-		builder.With("SearchQuery", searchQuery)
+		builder.With("SearchQuery", f.Q)
 
 		// Add flag to indicate if any filters are active
-		hasActiveFilters := f.Type != nil || f.Enabled != nil || (f.Search != nil && *f.Search != "")
+		hasActiveFilters := f.Type != nil || f.Enabled != nil || f.Q != ""
 		builder.With("HasActiveFilters", hasActiveFilters)
 	}
 }

services/merrymaker-go/internal/http/ui_secrets.go

@@ -25,19 +25,9 @@ func (h *UIHandlers) Secrets(w http.ResponseWriter, r *http.Request) {
 		Handler: h,
 		W:       w,
 		R:       r,
-		Fetcher: func(ctx context.Context, pg pageOpts) ([]*model.Secret, error) {
-			// Fetch pageSize+1 to detect hasNext
-			limit, offset := pg.LimitAndOffset()
-			secrets, err := h.SecretSvc.List(ctx, limit, offset)
-			if err != nil {
-				h.logger().Error("failed to load secrets for UI",
-					"error", err,
-					"page", pg.Page,
-					"page_size", pg.PageSize,
-				)
-			}
-			return secrets, err
-		},
+		Fetcher: WrapListFetcher(func(ctx context.Context, limit, offset int) ([]*model.Secret, error) {
+			return h.SecretSvc.List(ctx, limit, offset)
+		}, h.logger(), "failed to load secrets for UI"),
 		BasePath: "/secrets",
 		PageMeta: PageMeta{
 			Title:       "Merrymaker - Secrets",

services/merrymaker-go/internal/http/ui_sites.go

@@ -19,11 +19,8 @@ type siteRow struct {
 }
 
 type sitesFilter struct {
-	Q       string
-	Enabled *bool
-	Scope   string
-	Sort    string
-	Dir     string
+	BaseFilter
+	Scope string
 }
 
 type pageBounds struct {
@@ -32,18 +29,10 @@ type pageBounds struct {
 }
 
 func parseSitesFilter(q url.Values) (sitesFilter, error) {
-	qv := strings.TrimSpace(q.Get("q"))
-	enabledStr := strings.TrimSpace(q.Get("enabled"))
-	var enabledPtr *bool
-	switch enabledStr {
-	case StrTrue, StrFalse:
-		b := enabledStr == StrTrue
-		enabledPtr = &b
-	}
-	scope := strings.TrimSpace(q.Get("scope"))
-	sort, dir := ParseSortParam(q, "sort", "dir")
-
-	return sitesFilter{Q: qv, Enabled: enabledPtr, Scope: scope, Sort: sort, Dir: dir}, nil
+	return sitesFilter{
+		BaseFilter: ParseBaseFilter(q),
+		Scope:      strings.TrimSpace(q.Get("scope")),
+	}, nil
 }
 
 func toSiteRows(sites []*model.Site) []siteRow {

services/merrymaker-go/internal/http/ui_sources.go

@@ -14,18 +14,17 @@ const errMsgUnableLoadSources = "Unable to load sources."
 // --- helpers to keep handlers small and readable ---
 
 type sourcesFilters struct {
-	Q            string
+	BaseFilter
 	IncludeTests bool
 }
 
 func readSourcesFilters(v url.Values) sourcesFilters {
-	q := strings.TrimSpace(v.Get("q"))
 	inc := false
 	switch strings.ToLower(strings.TrimSpace(v.Get("include_tests"))) {
 	case "1", StrTrue, "on", "yes":
 		inc = true
 	}
-	return sourcesFilters{Q: q, IncludeTests: inc}
+	return sourcesFilters{BaseFilter: ParseBaseFilter(v), IncludeTests: inc}
 }
 
 func (h *UIHandlers) buildSourceCounts(