package db

import "strings"

func (s *Store) ListSystemLogsPage(filters SystemLogFilters) (SystemLogPage, error) {
	page := filters.Page
	if page <= 0 {
		page = 1
	}
	perPage := filters.PerPage
	if perPage <= 0 {
		perPage = 35
	}
	if perPage > 100 {
		perPage = 100
	}
	base := systemLogUnionSQL()
	where, args := systemLogWhere(filters)
	var total int
	if err := s.queryRow(`SELECT COUNT(*) FROM (`+base+`) system_logs`+where, args...).Scan(&total); err != nil {
		return SystemLogPage{}, err
	}
	queryArgs := append(append([]any{}, args...), perPage, (page-1)*perPage)
	rows, err := s.query(`SELECT id, category, type, target, status, message, detail, created_at
		FROM (`+base+`) system_logs`+where+` ORDER BY created_at DESC, id DESC LIMIT ? OFFSET ?`, queryArgs...)
	if err != nil {
		return SystemLogPage{}, err
	}
	defer rows.Close()
	items := []SystemLogItem{}
	for rows.Next() {
		var item SystemLogItem
		if err := rows.Scan(&item.ID, &item.Category, &item.Type, &item.Target, &item.Status, &item.Message, &item.Detail, &item.CreatedAt); err != nil {
			return SystemLogPage{}, err
		}
		items = append(items, item)
	}
	if err := rows.Err(); err != nil {
		return SystemLogPage{}, err
	}
	return SystemLogPage{Items: items, Total: total, Page: page, PerPage: perPage}, nil
}

func systemLogUnionSQL() string {
	return `SELECT id, 'operation' AS category, type, target,
		COALESCE(NULLIF(actor, ''), 'system') AS status, message, user_agent AS detail, created_at
		FROM audit_logs
		UNION ALL
		SELECT h.id, 'health' AS category, 'endpoint.health' AS type,
		COALESCE(NULLIF(e.source_id, ''), 'unknown') AS target, h.status,
		COALESCE(NULLIF(e.name, ''), 'unknown endpoint') AS message, h.error AS detail, h.checked_at AS created_at
		FROM endpoint_health_checks h LEFT JOIN source_endpoints e ON e.id = h.source_db_id
		UNION ALL
		SELECT id, 'client' AS category, 'endpoint.call' AS type, source_id AS target,
		status, error AS message, client AS detail, created_at
		FROM endpoint_call_logs
		UNION ALL
		SELECT id, 'database_sync' AS category, direction AS type, direction AS target,
		status, message, tables_json AS detail, COALESCE(NULLIF(finished_at, ''), started_at) AS created_at
		FROM database_sync_jobs
		UNION ALL
		SELECT id, 'legacy_sync' AS category, 'legacy.sync' AS type, 'legacy' AS target,
		status, summary AS message, stats_json AS detail, COALESCE(NULLIF(finished_at, ''), started_at) AS created_at
		FROM legacy_sync_jobs`
}

func systemLogWhere(filters SystemLogFilters) (string, []any) {
	clauses := []string{}
	args := []any{}
	if category := strings.TrimSpace(filters.Category); category != "" {
		clauses = append(clauses, "category = ?")
		args = append(args, sanitize(category))
	}
	if query := strings.TrimSpace(filters.Query); query != "" {
		like := "%" + strings.ToLower(sanitize(query)) + "%"
		clauses = append(clauses, `(LOWER(category) LIKE ? OR LOWER(type) LIKE ? OR LOWER(target) LIKE ? OR
			LOWER(status) LIKE ? OR LOWER(message) LIKE ? OR LOWER(detail) LIKE ? OR LOWER(created_at) LIKE ?)`)
		args = append(args, like, like, like, like, like, like, like)
	}
	if len(clauses) == 0 {
		return "", args
	}
	return " WHERE " + strings.Join(clauses, " AND "), args
}