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("GET /api/admin/labels", s.authAdmin(s.handleGetAdminLabels))
	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.labelTenantIDInt64(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
	}

	tenantIDPtr := s.labelTenantID(sess)
	if tenantIDPtr == nil {
		writeError(w, http.StatusBadRequest, "superadmin cannot create personal labels without a tenant")
		return
	}
	ownerID := sess.UserID
	label, err := s.labels.CreateLabel(r.Context(), req.Name, req.Color, &ownerID, *tenantIDPtr)
	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 ──────────────────────────────────────────────────

// handleGetAdminLabels returns all global labels (owner_id IS NULL) for the admin's tenant.
// Superadmins (no tenant) see labels where tenant_id IS NULL.
// GET /api/admin/labels
func (s *Server) handleGetAdminLabels(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)

	labels, err := s.labels.GetAdminLabels(r.Context(), tenantID)
	if err != nil {
		s.logger.Error("get admin labels failed", "err", err)
		writeError(w, http.StatusInternalServerError, "failed to load labels")
		return
	}
	if labels == nil {
		labels = []labelstore.Label{}
	}
	writeJSON(w, http.StatusOK, labels)
}

// 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.labelTenantIDInt64(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,
		"from_domain": true, "has_attachment": true,
	}
	if !allowed[req.ConditionField] {
		writeError(w, http.StatusBadRequest, "invalid condition_field")
		return
	}

	tenantIDPtr := s.labelTenantID(sess)
	if tenantIDPtr == nil {
		writeError(w, http.StatusBadRequest, "superadmin cannot create label rules without a tenant")
		return
	}
	rule, err := s.labels.CreateLabelRule(r.Context(), req.ConditionField, req.ConditionValue, req.LabelID, *tenantIDPtr)
	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.labelTenantIDInt64(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.
// Returns nil for superadmins without a tenant (stored as NULL in DB).
func (s *Server) labelTenantID(sess *auth.Session) *int64 {
	return sess.TenantID
}

// labelTenantIDInt64 returns tenant_id as int64 (0 for superadmin with no tenant).
// Only use for read queries where a zero result is acceptable (returns empty list).
func (s *Server) labelTenantIDInt64(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
}