namespace WxAgent.Core;

public sealed record WechatDatabaseGroupMember(long MemberId, string Username, string DisplayName, bool IsOwner);

public sealed record WechatGroupMemberPage(string GroupUsername, IReadOnlyList<WechatDatabaseGroupMember> Members, int? NextOffset)
{
    public bool HasMore => NextOffset is not null;
}

public static class WechatGroupMemberQuery
{
    public const string Sql = """
        SELECT m.member_id, c.username, c.nick_name, c.remark, cr.owner
        FROM chat_room AS cr
        JOIN chatroom_member AS m ON m.room_id = cr.id
        JOIN contact AS c ON c.id = m.member_id
        WHERE cr.username = $group
        ORDER BY m.member_id LIMIT $limit OFFSET $offset;
        """;

    public static IReadOnlyList<KeyValuePair<string, object?>> Parameters(string groupUsername, int limit, int offset)
    {
        if (string.IsNullOrWhiteSpace(groupUsername) || !groupUsername.EndsWith("@chatroom", StringComparison.Ordinal))
            throw new WxAgentException(WxAgentErrorCode.InvalidArgument, "A stable @chatroom username is required.");
        if (limit is < 1 or > 10000 || offset < 0 || offset > int.MaxValue - limit)
            throw new WxAgentException(WxAgentErrorCode.InvalidArgument, "Member limit must be 1-10000 and offset must leave room for the next page.");
        return new KeyValuePair<string, object?>[]
        {
            new("$group", groupUsername), new("$limit", limit + 1), new("$offset", offset)
        };
    }

    public static WechatGroupMemberPage Page(string groupUsername, IReadOnlyList<WechatDatabaseGroupMember> rows, int limit, int offset)
    {
        _ = Parameters(groupUsername, limit, offset);
        return new(groupUsername, rows.Take(limit).ToArray(), rows.Count > limit ? offset + limit : null);
    }
}