// Read-only aggregate queries backing the GoBD "Verfahrensdokumentation"
// draft generator (internal/api/compliance_handlers.go). No schema of its own —
// nothing here writes, so there is no initSchema and no migration file.
//
// Every query is strictly scoped to one tenant_id (application-side
// multi-tenancy, no Postgres RLS): the generated document is a per-tenant
// artefact and must never mix data of two tenants.
package storage

import (
	"context"
	"fmt"
)

// ComplianceStats are the aggregate key figures embedded in the generated
// Verfahrensdokumentation draft. All counters refer to exactly one tenant.
type ComplianceStats struct {
	Documents            int64 // active documents (deleted_at IS NULL)
	DocumentsInTrash     int64 // soft-deleted, not yet finally deleted
	DocumentsWithRetain  int64 // active documents carrying a retain_until date
	PermissionGroups     int64
	DocTypeGrants        int64
	TagGrants            int64
	DocumentGrants       int64
	DeleteRequestsByStat map[string]int64 // status -> count
}

// ComplianceStatsForTenant collects the aggregate figures for one tenant.
func (s *Store) ComplianceStatsForTenant(ctx context.Context, tenantID int64) (*ComplianceStats, error) {
	st := &ComplianceStats{DeleteRequestsByStat: map[string]int64{}}

	err := s.db.QueryRow(ctx, `
		SELECT
			COUNT(*) FILTER (WHERE deleted_at IS NULL),
			COUNT(*) FILTER (WHERE deleted_at IS NOT NULL),
			COUNT(*) FILTER (WHERE deleted_at IS NULL AND retain_until IS NOT NULL)
		FROM documents WHERE tenant_id = $1
	`, tenantID).Scan(&st.Documents, &st.DocumentsInTrash, &st.DocumentsWithRetain)
	if err != nil {
		return nil, fmt.Errorf("storage: compliance document stats: %w", err)
	}

	err = s.db.QueryRow(ctx, `
		SELECT
			(SELECT COUNT(*) FROM permission_groups     WHERE tenant_id = $1),
			(SELECT COUNT(*) FROM document_type_grants  WHERE tenant_id = $1),
			(SELECT COUNT(*) FROM tag_grants            WHERE tenant_id = $1),
			(SELECT COUNT(*) FROM document_grants       WHERE tenant_id = $1)
	`, tenantID).Scan(&st.PermissionGroups, &st.DocTypeGrants, &st.TagGrants, &st.DocumentGrants)
	if err != nil {
		return nil, fmt.Errorf("storage: compliance grant stats: %w", err)
	}

	rows, err := s.db.Query(ctx, `
		SELECT status, COUNT(*) FROM document_delete_requests
		WHERE tenant_id = $1 GROUP BY status ORDER BY status
	`, tenantID)
	if err != nil {
		return nil, fmt.Errorf("storage: compliance delete-request stats: %w", err)
	}
	defer rows.Close()
	for rows.Next() {
		var status string
		var n int64
		if err := rows.Scan(&status, &n); err != nil {
			return nil, fmt.Errorf("storage: scan compliance delete-request stats: %w", err)
		}
		st.DeleteRequestsByStat[status] = n
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("storage: compliance delete-request stats: %w", err)
	}
	return st, nil
}