feat(PROJ-9): implement labels backend - DB schema, labelstore, API handlers, Xapian integration

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/api/label_handlers.go

@@ -0,0 +1,407 @@
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+	"strconv"
+
+	"github.com/archivmail/internal/auth"
+	"github.com/archivmail/internal/labelstore"
+)
+
+// ── PROJ-9: Labels API Handlers ───────────────────────────────────────────
+
+// SetLabels wires the label store into the API server and registers label routes.
+func (s *Server) SetLabels(store *labelstore.Store) {
+	s.labels = store
+
+	// User label routes (all authenticated users)
+	s.mux.HandleFunc("GET /api/labels", s.auth(s.handleGetLabels))
+	s.mux.HandleFunc("POST /api/labels", s.auth(s.handleCreateLabel))
+	s.mux.HandleFunc("PATCH /api/labels/{id}", s.auth(s.handleUpdateLabel))
+	s.mux.HandleFunc("DELETE /api/labels/{id}", s.auth(s.handleDeleteLabel))
+
+	// Email-label assignment routes
+	s.mux.HandleFunc("POST /api/mails/{id}/labels", s.auth(s.handleAssignLabel))
+	s.mux.HandleFunc("DELETE /api/mails/{id}/labels/{label_id}", s.auth(s.handleRemoveLabel))
+
+	// Admin label routes (domain_admin and above)
+	s.mux.HandleFunc("POST /api/admin/labels", s.authAdmin(s.handleAdminCreateLabel))
+	s.mux.HandleFunc("GET /api/admin/label-rules", s.authAdmin(s.handleGetLabelRules))
+	s.mux.HandleFunc("POST /api/admin/label-rules", s.authAdmin(s.handleCreateLabelRule))
+	s.mux.HandleFunc("DELETE /api/admin/label-rules/{id}", s.authAdmin(s.handleDeleteLabelRule))
+}
+
+// handleGetLabels returns labels visible to the authenticated user
+// (own labels + global/admin labels for their tenant).
+// GET /api/labels
+func (s *Server) handleGetLabels(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+	if sess.UserID == 0 {
+		writeError(w, http.StatusUnauthorized, "not authenticated")
+		return
+	}
+
+	tenantID := s.labelTenantID(sess)
+	labels, err := s.labels.GetLabelsForUser(r.Context(), sess.UserID, tenantID)
+	if err != nil {
+		s.logger.Error("get labels failed", "err", err, "user_id", sess.UserID)
+		writeError(w, http.StatusInternalServerError, "failed to load labels")
+		return
+	}
+	if labels == nil {
+		labels = []labelstore.Label{}
+	}
+	writeJSON(w, http.StatusOK, labels)
+}
+
+// handleCreateLabel creates a user-owned label.
+// POST /api/labels
+func (s *Server) handleCreateLabel(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+	if sess.UserID == 0 {
+		writeError(w, http.StatusUnauthorized, "not authenticated")
+		return
+	}
+
+	var req struct {
+		Name  string `json:"name"`
+		Color string `json:"color"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if req.Name == "" {
+		writeError(w, http.StatusBadRequest, "name is required")
+		return
+	}
+	if req.Color == "" {
+		req.Color = "#6366f1"
+	}
+	if !isValidColor(req.Color) {
+		writeError(w, http.StatusBadRequest, "invalid color format")
+		return
+	}
+
+	tenantID := s.labelTenantID(sess)
+	ownerID := sess.UserID
+	label, err := s.labels.CreateLabel(r.Context(), req.Name, req.Color, &ownerID, tenantID)
+	if err != nil {
+		s.logger.Error("create label failed", "err", err, "user_id", sess.UserID)
+		writeError(w, http.StatusInternalServerError, "failed to create label")
+		return
+	}
+	writeJSON(w, http.StatusCreated, label)
+}
+
+// handleUpdateLabel updates a user's own label.
+// PATCH /api/labels/{id}
+func (s *Server) handleUpdateLabel(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+	if sess.UserID == 0 {
+		writeError(w, http.StatusUnauthorized, "not authenticated")
+		return
+	}
+
+	labelID, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid label id")
+		return
+	}
+
+	var req struct {
+		Name  string `json:"name"`
+		Color string `json:"color"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if req.Name == "" {
+		writeError(w, http.StatusBadRequest, "name is required")
+		return
+	}
+	if req.Color == "" {
+		req.Color = "#6366f1"
+	}
+	if !isValidColor(req.Color) {
+		writeError(w, http.StatusBadRequest, "invalid color format")
+		return
+	}
+
+	if err := s.labels.UpdateLabel(r.Context(), labelID, req.Name, req.Color, sess.UserID); err != nil {
+		s.logger.Error("update label failed", "err", err, "label_id", labelID, "user_id", sess.UserID)
+		writeError(w, http.StatusNotFound, "label not found")
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]bool{"ok": true})
+}
+
+// handleDeleteLabel deletes a user's own label.
+// DELETE /api/labels/{id}
+func (s *Server) handleDeleteLabel(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+	if sess.UserID == 0 {
+		writeError(w, http.StatusUnauthorized, "not authenticated")
+		return
+	}
+
+	labelID, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid label id")
+		return
+	}
+
+	if err := s.labels.DeleteLabel(r.Context(), labelID, sess.UserID); err != nil {
+		s.logger.Error("delete label failed", "err", err, "label_id", labelID, "user_id", sess.UserID)
+		writeError(w, http.StatusNotFound, "label not found")
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]bool{"ok": true})
+}
+
+// handleAssignLabel assigns a label to an email.
+// POST /api/mails/{id}/labels
+func (s *Server) handleAssignLabel(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+	if sess.UserID == 0 {
+		writeError(w, http.StatusUnauthorized, "not authenticated")
+		return
+	}
+
+	mailID := r.PathValue("id")
+	// SEC-22: Validate mail ID format to prevent path traversal.
+	if !isValidMailID(mailID) {
+		writeError(w, http.StatusBadRequest, "invalid mail id")
+		return
+	}
+
+	var req struct {
+		LabelID int64 `json:"label_id"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if req.LabelID <= 0 {
+		writeError(w, http.StatusBadRequest, "label_id is required")
+		return
+	}
+
+	if err := s.labels.AssignLabel(r.Context(), mailID, req.LabelID, "user"); err != nil {
+		s.logger.Error("assign label failed", "err", err, "mail_id", mailID, "label_id", req.LabelID)
+		writeError(w, http.StatusInternalServerError, "failed to assign label")
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]bool{"ok": true})
+}
+
+// handleRemoveLabel removes a label assignment from an email.
+// DELETE /api/mails/{id}/labels/{label_id}
+func (s *Server) handleRemoveLabel(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+	if sess.UserID == 0 {
+		writeError(w, http.StatusUnauthorized, "not authenticated")
+		return
+	}
+
+	mailID := r.PathValue("id")
+	// SEC-22: Validate mail ID format to prevent path traversal.
+	if !isValidMailID(mailID) {
+		writeError(w, http.StatusBadRequest, "invalid mail id")
+		return
+	}
+
+	labelID, err := strconv.ParseInt(r.PathValue("label_id"), 10, 64)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid label id")
+		return
+	}
+
+	if err := s.labels.RemoveLabel(r.Context(), mailID, labelID); err != nil {
+		s.logger.Error("remove label failed", "err", err, "mail_id", mailID, "label_id", labelID)
+		writeError(w, http.StatusInternalServerError, "failed to remove label")
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]bool{"ok": true})
+}
+
+// ── Admin Label Handlers ──────────────────────────────────────────────────
+
+// handleAdminCreateLabel creates a global label (no owner) for a tenant.
+// POST /api/admin/labels
+func (s *Server) handleAdminCreateLabel(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+
+	var req struct {
+		Name  string `json:"name"`
+		Color string `json:"color"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if req.Name == "" {
+		writeError(w, http.StatusBadRequest, "name is required")
+		return
+	}
+	if req.Color == "" {
+		req.Color = "#6366f1"
+	}
+	if !isValidColor(req.Color) {
+		writeError(w, http.StatusBadRequest, "invalid color format")
+		return
+	}
+
+	tenantID := s.labelTenantID(sess)
+	label, err := s.labels.CreateAdminLabel(r.Context(), req.Name, req.Color, tenantID)
+	if err != nil {
+		s.logger.Error("admin create label failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to create label")
+		return
+	}
+	writeJSON(w, http.StatusCreated, label)
+}
+
+// handleGetLabelRules returns all auto-label rules for the admin's tenant.
+// GET /api/admin/label-rules
+func (s *Server) handleGetLabelRules(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+	tenantID := s.labelTenantID(sess)
+
+	rules, err := s.labels.GetLabelRules(r.Context(), tenantID)
+	if err != nil {
+		s.logger.Error("get label rules failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to load label rules")
+		return
+	}
+	if rules == nil {
+		rules = []labelstore.LabelRule{}
+	}
+	writeJSON(w, http.StatusOK, rules)
+}
+
+// handleCreateLabelRule creates an auto-label rule.
+// POST /api/admin/label-rules
+func (s *Server) handleCreateLabelRule(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+
+	var req struct {
+		ConditionField string `json:"condition_field"`
+		ConditionValue string `json:"condition_value"`
+		LabelID        int64  `json:"label_id"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if req.ConditionField == "" || req.ConditionValue == "" || req.LabelID <= 0 {
+		writeError(w, http.StatusBadRequest, "condition_field, condition_value, and label_id are required")
+		return
+	}
+
+	// Validate allowed condition fields.
+	allowed := map[string]bool{
+		"from": true, "to": true, "subject": true, "domain": true,
+		"has_attachment": true,
+	}
+	if !allowed[req.ConditionField] {
+		writeError(w, http.StatusBadRequest, "invalid condition_field")
+		return
+	}
+
+	tenantID := s.labelTenantID(sess)
+	rule, err := s.labels.CreateLabelRule(r.Context(), req.ConditionField, req.ConditionValue, req.LabelID, tenantID)
+	if err != nil {
+		s.logger.Error("create label rule failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to create label rule")
+		return
+	}
+	writeJSON(w, http.StatusCreated, rule)
+}
+
+// handleDeleteLabelRule deletes an auto-label rule.
+// DELETE /api/admin/label-rules/{id}
+func (s *Server) handleDeleteLabelRule(w http.ResponseWriter, r *http.Request) {
+	if s.labels == nil {
+		writeError(w, http.StatusServiceUnavailable, "labels not available")
+		return
+	}
+	sess := sessionFromCtx(r.Context())
+
+	ruleID, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid rule id")
+		return
+	}
+
+	tenantID := s.labelTenantID(sess)
+	if err := s.labels.DeleteLabelRule(r.Context(), ruleID, tenantID); err != nil {
+		s.logger.Error("delete label rule failed", "err", err, "rule_id", ruleID)
+		writeError(w, http.StatusNotFound, "rule not found")
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]bool{"ok": true})
+}
+
+// ── Helpers ───────────────────────────────────────────────────────────────
+
+// labelTenantID extracts the tenant ID from the session for label operations.
+// Superadmins without a tenant get tenant_id=0 (global context).
+func (s *Server) labelTenantID(sess *auth.Session) int64 {
+	if sess.TenantID != nil {
+		return *sess.TenantID
+	}
+	return 0
+}
+
+// isValidColor validates a hex color string like "#6366f1".
+func isValidColor(c string) bool {
+	if len(c) != 7 || c[0] != '#' {
+		return false
+	}
+	for _, b := range c[1:] {
+		if !((b >= '0' && b <= '9') || (b >= 'a' && b <= 'f') || (b >= 'A' && b <= 'F')) {
+			return false
+		}
+	}
+	return true
+}
+

internal/api/server.go

@@ -25,6 +25,7 @@ import (
 	"github.com/archivmail/internal/auth"
 	imapstore "github.com/archivmail/internal/imap"
 	"github.com/archivmail/internal/index"
+	"github.com/archivmail/internal/labelstore"
 	ldapcfg "github.com/archivmail/internal/ldapconfig"
 	pop3store "github.com/archivmail/internal/pop3"
 	"github.com/archivmail/internal/smtpd"
@@ -79,6 +80,7 @@ type Server struct {
 	pop3Store     *pop3store.Store
 	pop3Importer  *pop3store.Importer
 	uploadJobs    sync.Map // jobID → *UploadJob
+	labels        *labelstore.Store         // PROJ-9: label management
 	ldapStore         *ldapcfg.Store
 	tenantStore       *tenantstore.Store
 	tenantLdapStore   *ldapcfg.TenantStore   // PROJ-23: per-tenant LDAP config
@@ -600,6 +602,7 @@ func (s *Server) handleSearch(w http.ResponseWriter, r *http.Request) {
 	dateToStr := r.URL.Query().Get("date_to")
 	sortParam := r.URL.Query().Get("sort") // "relevance", "date_asc", "date_desc"
 	hasAttachStr := r.URL.Query().Get("has_attachment") // "true" or "false"
+	labelIDStr := r.URL.Query().Get("label_id")       // PROJ-9: filter by label
 	pageStr := r.URL.Query().Get("page")
 	pageSizeStr := r.URL.Query().Get("page_size")
 
@@ -616,6 +619,13 @@ func (s *Server) handleSearch(w http.ResponseWriter, r *http.Request) {
 		Page:     page,
 	}
 
+	// PROJ-9: Parse label_id filter.
+	if labelIDStr != "" {
+		if lid, err := strconv.ParseInt(labelIDStr, 10, 64); err == nil && lid > 0 {
+			req.LabelID = &lid
+		}
+	}
+
 	if hasAttachStr == "true" {
 		v := true
 		req.HasAttachment = &v
@@ -691,6 +701,25 @@ func (s *Server) handleSearch(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	// PROJ-9: Post-filter by label_id when the label store is available.
+	if req.LabelID != nil && s.labels != nil && len(result.Hits) > 0 {
+		labelEmailIDs, lErr := s.labels.GetEmailIDsByLabel(r.Context(), *req.LabelID)
+		if lErr == nil {
+			allowed := make(map[string]struct{}, len(labelEmailIDs))
+			for _, id := range labelEmailIDs {
+				allowed[id] = struct{}{}
+			}
+			filtered := result.Hits[:0]
+			for _, h := range result.Hits {
+				if _, ok := allowed[h.ID]; ok {
+					filtered = append(filtered, h)
+				}
+			}
+			result.Hits = filtered
+			result.Total = len(filtered)
+		}
+	}
+
 	sess := sessionFromCtx(r.Context())
 	s.audlog.Log(audit.Entry{
 		EventType: audit.EventSearch,
@@ -710,7 +739,19 @@ func (s *Server) handleSearch(w http.ResponseWriter, r *http.Request) {
 		Date           string  `json:"date,omitempty"`
 		Size           int64   `json:"size,omitempty"`
 		HasAttachments bool    `json:"has_attachments"`
+		LabelIDs       []int64 `json:"label_ids,omitempty"` // PROJ-9
 	}
+
+	// PROJ-9: Batch-load label IDs for all hits.
+	var labelMap map[string][]int64
+	if s.labels != nil && len(result.Hits) > 0 {
+		emailIDs := make([]string, len(result.Hits))
+		for i, h := range result.Hits {
+			emailIDs[i] = h.ID
+		}
+		labelMap, _ = s.labels.GetLabelsForEmails(r.Context(), emailIDs)
+	}
+
 	enriched := make([]enrichedHit, 0, len(result.Hits))
 	for _, h := range result.Hits {
 		eh := enrichedHit{ID: h.ID, Score: h.Score}
@@ -728,6 +769,9 @@ func (s *Server) handleSearch(w http.ResponseWriter, r *http.Request) {
 				eh.HasAttachments = len(pm.Attachments) > 0
 			}
 		}
+		if labelMap != nil {
+			eh.LabelIDs = labelMap[h.ID]
+		}
 		enriched = append(enriched, eh)
 	}
 

internal/index/index.go

@@ -28,6 +28,7 @@ type SearchRequest struct {
 	DateFrom      *time.Time
 	DateTo        *time.Time
 	HasAttachment *bool  // nil=no filter, true=only with, false=only without
+	LabelID       *int64 `json:"label_id,omitempty"` // PROJ-9: post-filter by label
 	Sort          string // "relevance", "date_asc", "date_desc" (default: date_desc)
 	PageSize      int
 	Page          int

internal/labelstore/store.go

@@ -0,0 +1,329 @@
+// Package labelstore manages labels, email-label assignments, and auto-label
+// rules in PostgreSQL. Part of PROJ-9: Ordner- & Label-Verwaltung.
+package labelstore
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// Label represents a user-defined or global (admin) label.
+type Label struct {
+	ID        int64     `json:"id"`
+	Name      string    `json:"name"`
+	Color     string    `json:"color"`
+	OwnerID   *int64    `json:"owner_id,omitempty"`
+	TenantID  int64     `json:"tenant_id"`
+	CreatedAt time.Time `json:"created_at"`
+	IsGlobal  bool      `json:"is_global"`
+}
+
+// LabelRule describes an automatic label assignment rule (admin-only).
+type LabelRule struct {
+	ID             int64  `json:"id"`
+	ConditionField string `json:"condition_field"`
+	ConditionValue string `json:"condition_value"`
+	LabelID        int64  `json:"label_id"`
+	TenantID       int64  `json:"tenant_id"`
+}
+
+// Store is a PostgreSQL-backed label store.
+type Store struct {
+	db *pgxpool.Pool
+}
+
+const schemaSQL = `
+CREATE TABLE IF NOT EXISTS labels (
+    id         BIGSERIAL PRIMARY KEY,
+    name       VARCHAR(100) NOT NULL,
+    color      VARCHAR(7) NOT NULL DEFAULT '#6366f1',
+    owner_id   BIGINT REFERENCES users(id) ON DELETE CASCADE,
+    tenant_id  BIGINT REFERENCES tenants(id) ON DELETE CASCADE,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    UNIQUE(name, owner_id, tenant_id)
+);
+
+CREATE TABLE IF NOT EXISTS email_labels (
+    email_id    VARCHAR(64) NOT NULL,
+    label_id    BIGINT NOT NULL REFERENCES labels(id) ON DELETE CASCADE,
+    assigned_at TIMESTAMPTZ DEFAULT NOW(),
+    assigned_by VARCHAR(20) NOT NULL DEFAULT 'user',
+    PRIMARY KEY (email_id, label_id)
+);
+
+CREATE TABLE IF NOT EXISTS label_rules (
+    id               BIGSERIAL PRIMARY KEY,
+    condition_field  VARCHAR(30) NOT NULL,
+    condition_value  VARCHAR(255) NOT NULL,
+    label_id         BIGINT NOT NULL REFERENCES labels(id) ON DELETE CASCADE,
+    tenant_id        BIGINT REFERENCES tenants(id) ON DELETE CASCADE,
+    created_at       TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_email_labels_label_id ON email_labels(label_id);
+CREATE INDEX IF NOT EXISTS idx_email_labels_email_id ON email_labels(email_id);
+CREATE INDEX IF NOT EXISTS idx_label_rules_tenant_id ON label_rules(tenant_id);
+CREATE INDEX IF NOT EXISTS idx_labels_tenant_id ON labels(tenant_id);
+CREATE INDEX IF NOT EXISTS idx_labels_owner_id ON labels(owner_id);
+`
+
+// New connects to PostgreSQL and initialises the labels schema.
+func New(dsn string) (*Store, error) {
+	ctx := context.Background()
+	pool, err := pgxpool.New(ctx, dsn)
+	if err != nil {
+		return nil, fmt.Errorf("labelstore: connect: %w", err)
+	}
+
+	s := &Store{db: pool}
+	if err := s.initSchema(ctx); err != nil {
+		pool.Close()
+		return nil, fmt.Errorf("labelstore: init schema: %w", err)
+	}
+
+	return s, nil
+}
+
+func (s *Store) initSchema(ctx context.Context) error {
+	_, err := s.db.Exec(ctx, schemaSQL)
+	return err
+}
+
+// Close closes the underlying connection pool.
+func (s *Store) Close() error {
+	s.db.Close()
+	return nil
+}
+
+// ── Label CRUD ────────────────────────────────────────────────────────────
+
+// GetLabelsForUser returns the user's own labels plus global labels (owner_id IS NULL)
+// for the given tenant.
+func (s *Store) GetLabelsForUser(ctx context.Context, userID int64, tenantID int64) ([]Label, error) {
+	rows, err := s.db.Query(ctx, `
+		SELECT id, name, color, owner_id, tenant_id, created_at
+		FROM labels
+		WHERE tenant_id = $1 AND (owner_id = $2 OR owner_id IS NULL)
+		ORDER BY name
+	`, tenantID, userID)
+	if err != nil {
+		return nil, fmt.Errorf("labelstore: get labels: %w", err)
+	}
+	defer rows.Close()
+
+	var labels []Label
+	for rows.Next() {
+		var l Label
+		if err := rows.Scan(&l.ID, &l.Name, &l.Color, &l.OwnerID, &l.TenantID, &l.CreatedAt); err != nil {
+			return nil, fmt.Errorf("labelstore: scan label: %w", err)
+		}
+		l.IsGlobal = l.OwnerID == nil
+		labels = append(labels, l)
+	}
+	return labels, rows.Err()
+}
+
+// CreateLabel creates a user-owned label.
+func (s *Store) CreateLabel(ctx context.Context, name, color string, ownerID *int64, tenantID int64) (Label, error) {
+	var l Label
+	err := s.db.QueryRow(ctx, `
+		INSERT INTO labels (name, color, owner_id, tenant_id)
+		VALUES ($1, $2, $3, $4)
+		RETURNING id, name, color, owner_id, tenant_id, created_at
+	`, name, color, ownerID, tenantID).Scan(&l.ID, &l.Name, &l.Color, &l.OwnerID, &l.TenantID, &l.CreatedAt)
+	if err != nil {
+		return Label{}, fmt.Errorf("labelstore: create label: %w", err)
+	}
+	l.IsGlobal = l.OwnerID == nil
+	return l, nil
+}
+
+// UpdateLabel updates name and color of a label owned by the given user.
+func (s *Store) UpdateLabel(ctx context.Context, labelID int64, name, color string, userID int64) error {
+	tag, err := s.db.Exec(ctx, `
+		UPDATE labels SET name = $1, color = $2
+		WHERE id = $3 AND owner_id = $4
+	`, name, color, labelID, userID)
+	if err != nil {
+		return fmt.Errorf("labelstore: update label: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return fmt.Errorf("labelstore: label not found or not owned by user")
+	}
+	return nil
+}
+
+// DeleteLabel deletes a label owned by the given user.
+func (s *Store) DeleteLabel(ctx context.Context, labelID int64, userID int64) error {
+	tag, err := s.db.Exec(ctx, `
+		DELETE FROM labels WHERE id = $1 AND owner_id = $2
+	`, labelID, userID)
+	if err != nil {
+		return fmt.Errorf("labelstore: delete label: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return fmt.Errorf("labelstore: label not found or not owned by user")
+	}
+	return nil
+}
+
+// ── Email-Label Assignment ────────────────────────────────────────────────
+
+// AssignLabel assigns a label to an email. Duplicate assignments are silently ignored.
+func (s *Store) AssignLabel(ctx context.Context, emailID string, labelID int64, assignedBy string) error {
+	_, err := s.db.Exec(ctx, `
+		INSERT INTO email_labels (email_id, label_id, assigned_by)
+		VALUES ($1, $2, $3)
+		ON CONFLICT (email_id, label_id) DO NOTHING
+	`, emailID, labelID, assignedBy)
+	if err != nil {
+		return fmt.Errorf("labelstore: assign label: %w", err)
+	}
+	return nil
+}
+
+// RemoveLabel removes a label assignment from an email.
+func (s *Store) RemoveLabel(ctx context.Context, emailID string, labelID int64) error {
+	_, err := s.db.Exec(ctx, `
+		DELETE FROM email_labels WHERE email_id = $1 AND label_id = $2
+	`, emailID, labelID)
+	if err != nil {
+		return fmt.Errorf("labelstore: remove label: %w", err)
+	}
+	return nil
+}
+
+// GetLabelIDsForEmail returns all label IDs assigned to a given email.
+func (s *Store) GetLabelIDsForEmail(ctx context.Context, emailID string) ([]int64, error) {
+	rows, err := s.db.Query(ctx, `
+		SELECT label_id FROM email_labels WHERE email_id = $1
+	`, emailID)
+	if err != nil {
+		return nil, fmt.Errorf("labelstore: get label ids: %w", err)
+	}
+	defer rows.Close()
+
+	var ids []int64
+	for rows.Next() {
+		var id int64
+		if err := rows.Scan(&id); err != nil {
+			return nil, fmt.Errorf("labelstore: scan label id: %w", err)
+		}
+		ids = append(ids, id)
+	}
+	return ids, rows.Err()
+}
+
+// GetEmailIDsByLabel returns all email IDs that have a specific label assigned.
+func (s *Store) GetEmailIDsByLabel(ctx context.Context, labelID int64) ([]string, error) {
+	rows, err := s.db.Query(ctx, `
+		SELECT email_id FROM email_labels WHERE label_id = $1
+	`, labelID)
+	if err != nil {
+		return nil, fmt.Errorf("labelstore: get email ids by label: %w", err)
+	}
+	defer rows.Close()
+
+	var ids []string
+	for rows.Next() {
+		var id string
+		if err := rows.Scan(&id); err != nil {
+			return nil, fmt.Errorf("labelstore: scan email id: %w", err)
+		}
+		ids = append(ids, id)
+	}
+	return ids, rows.Err()
+}
+
+// ── Admin Labels (Global) ─────────────────────────────────────────────────
+
+// CreateAdminLabel creates a global label (owner_id = NULL) for a tenant.
+func (s *Store) CreateAdminLabel(ctx context.Context, name, color string, tenantID int64) (Label, error) {
+	return s.CreateLabel(ctx, name, color, nil, tenantID)
+}
+
+// ── Label Rules ───────────────────────────────────────────────────────────
+
+// GetLabelRules returns all auto-label rules for a tenant.
+func (s *Store) GetLabelRules(ctx context.Context, tenantID int64) ([]LabelRule, error) {
+	rows, err := s.db.Query(ctx, `
+		SELECT id, condition_field, condition_value, label_id, tenant_id
+		FROM label_rules
+		WHERE tenant_id = $1
+		ORDER BY id
+	`, tenantID)
+	if err != nil {
+		return nil, fmt.Errorf("labelstore: get rules: %w", err)
+	}
+	defer rows.Close()
+
+	var rules []LabelRule
+	for rows.Next() {
+		var r LabelRule
+		if err := rows.Scan(&r.ID, &r.ConditionField, &r.ConditionValue, &r.LabelID, &r.TenantID); err != nil {
+			return nil, fmt.Errorf("labelstore: scan rule: %w", err)
+		}
+		rules = append(rules, r)
+	}
+	return rules, rows.Err()
+}
+
+// CreateLabelRule creates an auto-label rule for a tenant.
+func (s *Store) CreateLabelRule(ctx context.Context, field, value string, labelID int64, tenantID int64) (LabelRule, error) {
+	var r LabelRule
+	err := s.db.QueryRow(ctx, `
+		INSERT INTO label_rules (condition_field, condition_value, label_id, tenant_id)
+		VALUES ($1, $2, $3, $4)
+		RETURNING id, condition_field, condition_value, label_id, tenant_id
+	`, field, value, labelID, tenantID).Scan(&r.ID, &r.ConditionField, &r.ConditionValue, &r.LabelID, &r.TenantID)
+	if err != nil {
+		return LabelRule{}, fmt.Errorf("labelstore: create rule: %w", err)
+	}
+	return r, nil
+}
+
+// DeleteLabelRule deletes an auto-label rule within a tenant.
+func (s *Store) DeleteLabelRule(ctx context.Context, ruleID int64, tenantID int64) error {
+	tag, err := s.db.Exec(ctx, `
+		DELETE FROM label_rules WHERE id = $1 AND tenant_id = $2
+	`, ruleID, tenantID)
+	if err != nil {
+		return fmt.Errorf("labelstore: delete rule: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return fmt.Errorf("labelstore: rule not found")
+	}
+	return nil
+}
+
+// ── Batch Helpers ─────────────────────────────────────────────────────────
+
+// GetLabelsForEmails returns a map of email_id -> []int64 (label IDs) for a
+// batch of email IDs. Useful for enriching search results.
+func (s *Store) GetLabelsForEmails(ctx context.Context, emailIDs []string) (map[string][]int64, error) {
+	if len(emailIDs) == 0 {
+		return nil, nil
+	}
+	rows, err := s.db.Query(ctx, `
+		SELECT email_id, label_id FROM email_labels WHERE email_id = ANY($1)
+	`, emailIDs)
+	if err != nil {
+		return nil, fmt.Errorf("labelstore: get labels for emails: %w", err)
+	}
+	defer rows.Close()
+
+	result := make(map[string][]int64)
+	for rows.Next() {
+		var emailID string
+		var labelID int64
+		if err := rows.Scan(&emailID, &labelID); err != nil {
+			return nil, fmt.Errorf("labelstore: scan: %w", err)
+		}
+		result[emailID] = append(result[emailID], labelID)
+	}
+	return result, rows.Err()
+}

internal/storage/migrations/012_labels.sql

@@ -0,0 +1,32 @@
+-- PROJ-9: Labels, email-label assignments, and auto-label rules.
+-- This file is documentation; the actual schema is applied by labelstore.initSchema().
+
+CREATE TABLE IF NOT EXISTS labels (
+    id         BIGSERIAL PRIMARY KEY,
+    name       VARCHAR(100) NOT NULL,
+    color      VARCHAR(7) NOT NULL DEFAULT '#6366f1',
+    owner_id   BIGINT REFERENCES users(id) ON DELETE CASCADE,
+    tenant_id  BIGINT REFERENCES tenants(id) ON DELETE CASCADE,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    UNIQUE(name, owner_id, tenant_id)
+);
+
+CREATE TABLE IF NOT EXISTS email_labels (
+    email_id    VARCHAR(64) NOT NULL,
+    label_id    BIGINT NOT NULL REFERENCES labels(id) ON DELETE CASCADE,
+    assigned_at TIMESTAMPTZ DEFAULT NOW(),
+    assigned_by VARCHAR(20) NOT NULL DEFAULT 'user',
+    PRIMARY KEY (email_id, label_id)
+);
+
+CREATE TABLE IF NOT EXISTS label_rules (
+    id               BIGSERIAL PRIMARY KEY,
+    condition_field  VARCHAR(30) NOT NULL,
+    condition_value  VARCHAR(255) NOT NULL,
+    label_id         BIGINT NOT NULL REFERENCES labels(id) ON DELETE CASCADE,
+    tenant_id        BIGINT REFERENCES tenants(id) ON DELETE CASCADE,
+    created_at       TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_email_labels_label_id ON email_labels(label_id);
+CREATE INDEX IF NOT EXISTS idx_label_rules_tenant_id ON label_rules(tenant_id);