feat(collections): smart (dynamic) collections — rules evaluated live at render

Type is DERIVED, not stored: a saved ruleset makes a collection SMART,
no rules = STATIC (stored collection_items links, unchanged behavior).
No schema change — collections.auto_assign_rules JSONB already carried
the config; user's decision 2026-10-14 (handoff: live-at-render, not
refresh-on-scan; create-time Static/Smart toggle; v1 NO hybrid).

- Rule gains an enabled flag (absent = enabled, legacy rules unaffected).
- Rule CRUD: POST/PUT(DELETE) /api/collections/:id/rules[/:ruleId] — the
  survivor dead effort of the rules-builder UI finally has real
  endpoints (rules were never editable after creation; nothing ever
  re-evaluated them). First rule converts a user collection to smart;
  removing the last reverts it to static. UpdateCollectionRulesJSON
  edits ONLY the rules doc so rule CRUD cannot clobber metadata.
- Live evaluation: candidates from GetVisibleLiveMediaForRules —
  visible-library set (family lens enforced at source) + archived IS
  NULL AND missing_scan_count = 0 — any enabled rule matches, title
  order. Zero refresh hooks by design: always current by construction.
- Membership mutations (add/remove/bulk-add) are 400 on smart — v1 no
  hybrid; collection_items.excluded stays the reserved future hook.
- Rules builder page (/collections/:id/rules) first time ever routable;
  templ whole-attribute interpolation ("{ expr }" inside a quoted attr
  value is literal text, as theme-{ user.Theme } silently proved).
- UI: create modal Static/⚡Smart cards (smart create redirects into the
  rules builder), ⚡ badge + real per-card counts on the grid (smart =
  live matches, static = stored-link count), smart detail renders
  matched books with no hand-pick actions + an Edit Rules button.
- API: GET /:id gains is_smart + live books; GET /: keeps the Android
  app's default exclusion, include_auto=true surfaces smart rows with
  live counts; TestRules previews against the SAME candidates the live
  render uses (visible + live, was raw first-1000).
- FIXED pre-existing regression from 7ce7321: static collection detail
  with NO library_id returned zero books — QueryType != '' caught user
  rows ('filter' default) and routed them to dashboard sections that
  never contain them; now only real system query types go there
  (handlers + SSR). App-visible symptom: /api/collections/:id without
  library_id came back books:[] for every static collection.

Tests: collections_smart_test.go (conversion, disabled rules, mutation
guards, revert-to-static, validation, system-collection prohibition,
include_auto semantics). Full offline integration suite PASS.

internal/services/collection_service.go

@@ -24,8 +24,30 @@ type Rule struct {
 	Operator string `json:"operator"` // "equals", "contains", "starts_with", "ends_with", "greater_than", "less_than"
 	Value    string `json:"value"`
 	Priority int    `json:"priority"` // 1-10, higher values take precedence
+	// Enabled gates the rule in the LIVE evaluation used by smart
+	// collections; absent (JSON omitempty) means enabled — rules written
+	// before the field existed keep matching.
+	Enabled *bool `json:"enabled,omitempty"`
 }
 
+// Known rule fields and operators — the rules builder UI and the
+// persisted JSONB documents must agree with this vocabulary.
+var ruleFields = map[string]bool{
+	"genre": true, "series": true, "author": true, "language": true,
+	"publisher": true, "copyright_year": true, "tags": true,
+}
+
+var ruleOperators = map[string]bool{
+	"equals": true, "not_equals": true, "contains": true, "not_contains": true,
+	"starts_with": true, "ends_with": true, "greater_than": true, "less_than": true,
+}
+
+// RuleValidationError reports a rule payload the evaluator could never
+// honor (unknown field/operator, empty value).
+type RuleValidationError struct{ Msg string }
+
+func (e *RuleValidationError) Error() string { return e.Msg }
+
 // RuleEvaluation represents the result of evaluating a rule
 type RuleEvaluation struct {
 	RuleID     string  `json:"rule_id"`
@@ -244,6 +266,248 @@ func (s *CollectionService) GetBookCollections(ctx context.Context, mediaItemID
 	return collections, nil
 }
 
+// ParseRules decodes a collection's auto_assign_rules JSONB into typed
+// rules. "null", empty, and malformed docs mean "no rules".
+func (s *CollectionService) ParseRules(raw []byte) []Rule {
+	if len(raw) == 0 {
+		return nil
+	}
+	var rules []Rule
+	if err := json.Unmarshal(raw, &rules); err != nil {
+		return nil
+	}
+	return rules
+}
+
+// IsSmartCollection derives the collection type: a non-empty ruleset
+// makes it SMART (live-matched), an empty/absent ruleset makes it STATIC
+// (stored collection_items links).
+func (s *CollectionService) IsSmartCollection(raw []byte) bool {
+	return len(s.ParseRules(raw)) > 0
+}
+
+// EnabledRules filters a ruleset down to the rules that participate in
+// live evaluation (absent enabled = enabled for backward compatibility).
+func (s *CollectionService) EnabledRules(rules []Rule) []Rule {
+	enabled := make([]Rule, 0, len(rules))
+	for _, rule := range rules {
+		if rule.Enabled == nil || *rule.Enabled {
+			enabled = append(enabled, rule)
+		}
+	}
+	return enabled
+}
+
+// validateRule checks a rule payload the evaluator will have to honor.
+func (s *CollectionService) validateRule(rule Rule) error {
+	if !ruleFields[rule.Field] {
+		return &RuleValidationError{Msg: "unknown rule field: " + rule.Field}
+	}
+	if !ruleOperators[rule.Operator] {
+		return &RuleValidationError{Msg: "unknown rule operator: " + rule.Operator}
+	}
+	if strings.TrimSpace(rule.Value) == "" {
+		return &RuleValidationError{Msg: "rule value is required"}
+	}
+	if rule.Priority < 0 || rule.Priority > 10 {
+		return &RuleValidationError{Msg: "priority must be between 0 and 10"}
+	}
+	return nil
+}
+
+// AddRule appends a rule to the collection's ruleset, generating an id
+// when the caller did not supply one. Adding the first rule CONVERTS a
+// static collection to smart (type is derived from rules presence).
+func (s *CollectionService) AddRule(ctx context.Context, collectionID uuid.UUID, rule Rule) (database.Collections, Rule, error) {
+	if err := s.validateRule(rule); err != nil {
+		return database.Collections{}, Rule{}, err
+	}
+
+	collection, err := s.GetCollection(ctx, collectionID)
+	if err != nil {
+		return database.Collections{}, Rule{}, err
+	}
+
+	rules := s.ParseRules(collection.AutoAssignRules)
+	if rule.ID == "" {
+		rule.ID = uuid.NewString()
+	}
+	rules = append(rules, rule)
+
+	rulesJSON, marshalErr := json.Marshal(rules)
+	if marshalErr != nil {
+		return database.Collections{}, Rule{}, fmt.Errorf("failed to marshal rules: %w", marshalErr)
+	}
+
+	updated, err := s.db.UpdateCollectionRulesJSON(ctx, database.UpdateCollectionRulesJSONParams{
+			ID:              pgtype.UUID{Bytes: collectionID, Valid: true},
+			AutoAssignRules: rulesJSON,
+		})
+	if err != nil {
+		return database.Collections{}, Rule{}, fmt.Errorf("failed to save rules: %w", err)
+	}
+	return updated, rule, nil
+}
+
+// SetRuleEnabled flips a single rule's enabled flag in place.
+func (s *CollectionService) SetRuleEnabled(ctx context.Context, collectionID uuid.UUID, ruleID string, enabled bool) (database.Collections, error) {
+	collection, err := s.GetCollection(ctx, collectionID)
+	if err != nil {
+		return database.Collections{}, err
+	}
+	rules := s.ParseRules(collection.AutoAssignRules)
+	found := false
+	for i := range rules {
+		if rules[i].ID == ruleID {
+			rules[i].Enabled = &enabled
+			found = true
+			break
+		}
+	}
+	if !found {
+		return database.Collections{}, fmt.Errorf("rule not found: %s", ruleID)
+	}
+
+	rulesJSON, marshalErr := json.Marshal(rules)
+	if marshalErr != nil {
+		return database.Collections{}, fmt.Errorf("failed to marshal rules: %w", marshalErr)
+	}
+
+	updated, err := s.db.UpdateCollectionRulesJSON(ctx, database.UpdateCollectionRulesJSONParams{
+			ID:              pgtype.UUID{Bytes: collectionID, Valid: true},
+			AutoAssignRules: rulesJSON,
+		})
+	if err != nil {
+		return database.Collections{}, fmt.Errorf("failed to save rules: %w", err)
+	}
+	return updated, nil
+}
+
+// RemoveRule deletes a single rule from the ruleset. Removing the LAST
+// rule converts the collection back to static (type is derived).
+func (s *CollectionService) RemoveRule(ctx context.Context, collectionID uuid.UUID, ruleID string) (database.Collections, error) {
+	collection, err := s.GetCollection(ctx, collectionID)
+	if err != nil {
+		return database.Collections{}, err
+	}
+	rules := s.ParseRules(collection.AutoAssignRules)
+	kept := make([]Rule, 0, len(rules))
+	found := false
+	for _, rule := range rules {
+		if rule.ID == ruleID {
+			found = true
+			continue
+		}
+		kept = append(kept, rule)
+	}
+	if !found {
+		return database.Collections{}, fmt.Errorf("rule not found: %s", ruleID)
+	}
+
+	rulesJSON, marshalErr := json.Marshal(kept)
+	if marshalErr != nil {
+		return database.Collections{}, fmt.Errorf("failed to marshal rules: %w", marshalErr)
+	}
+
+	updated, err := s.db.UpdateCollectionRulesJSON(ctx, database.UpdateCollectionRulesJSONParams{
+			ID:              pgtype.UUID{Bytes: collectionID, Valid: true},
+			AutoAssignRules: rulesJSON,
+		})
+	if err != nil {
+		return database.Collections{}, fmt.Errorf("failed to save rules: %w", err)
+	}
+	return updated, nil
+}
+
+// SmartEvalOptions scopes a smart collection's live evaluation.
+type SmartEvalOptions struct {
+	// LibraryID, when valid, restricts matching to one library (the
+	// detail page's library switcher).
+	LibraryID pgtype.UUID
+	// VisibleIDs is the requesting user's visible-library set (family
+	// lens). Empty means no visible-library filter.
+	VisibleIDs []pgtype.UUID
+}
+
+// EvaluateSmartCollection resolves a smart collection's membership LIVE:
+// every visible live book matched by at least one enabled rule is in.
+// No stored links are consulted — "truly dynamic," always current.
+func (s *CollectionService) EvaluateSmartCollection(ctx context.Context, rules []Rule, opts SmartEvalOptions) ([]database.MediaItems, error) {
+	enabled := s.EnabledRules(rules)
+	if len(enabled) == 0 {
+		return []database.MediaItems{}, nil
+	}
+
+	var visibleArg []pgtype.UUID
+	if len(opts.VisibleIDs) > 0 {
+		visibleArg = opts.VisibleIDs
+	}
+	items, err := s.db.GetVisibleLiveMediaForRules(ctx, database.GetVisibleLiveMediaForRulesParams{
+		LibraryID:         opts.LibraryID,
+		VisibleLibraryIds: visibleArg,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to load candidate books: %w", err)
+	}
+
+	matches := make([]database.MediaItems, 0, len(items))
+	for _, item := range items {
+		if s.mediaItemMatchesAnyRule(item, enabled) {
+			matches = append(matches, item)
+		}
+	}
+	return matches, nil
+}
+
+func (s *CollectionService) mediaItemMatchesAnyRule(item database.MediaItems, rules []Rule) bool {
+	for _, rule := range rules {
+		if s.mediaItemMatchesRule(item, rule) {
+			return true
+		}
+	}
+	return false
+}
+
+func (s *CollectionService) mediaItemMatchesRule(item database.MediaItems, rule Rule) bool {
+	if rule.Enabled != nil && !*rule.Enabled {
+		return false
+	}
+
+	var fieldValue string
+	switch rule.Field {
+	case "genre":
+		if item.Genre.Valid {
+			fieldValue = item.Genre.String
+		}
+	case "series":
+		if item.Series.Valid {
+			fieldValue = item.Series.String
+		}
+	case "author":
+		if item.Author.Valid {
+			fieldValue = item.Author.String
+		}
+	case "language":
+		if item.Language.Valid {
+			fieldValue = item.Language.String
+		}
+	case "publisher":
+		if item.Publisher.Valid {
+			fieldValue = item.Publisher.String
+		}
+	case "copyright_year":
+		if item.CopyrightYear.Valid {
+			fieldValue = fmt.Sprintf("%d", item.CopyrightYear.Int32)
+		}
+	case "tags":
+		if len(item.Tags) > 0 {
+			fieldValue = strings.Join(item.Tags, ", ")
+		}
+	}
+
+	return s.evaluateRule(fieldValue, rule.Operator, rule.Value)
+}
+
 // EvaluateRules evaluates auto-assign rules for a media item
 func (s *CollectionService) EvaluateRules(mediaItem database.ListMediaItemsRow, rules []Rule) []RuleEvaluation {
 	var evaluations []RuleEvaluation
@@ -260,6 +524,11 @@ func (s *CollectionService) EvaluateRules(mediaItem database.ListMediaItemsRow,
 	}
 
 	for _, rule := range sortedRules {
+		// Disabled rules never match (kept for context in the UI only).
+		if rule.Enabled != nil && !*rule.Enabled {
+			evaluations = append(evaluations, RuleEvaluation{RuleID: rule.ID, Matches: false})
+			continue
+		}
 		eval := RuleEvaluation{
 			RuleID:  rule.ID,
 			Matches: false,