using System.Text.Json.Serialization;

namespace WebDrop.Core;

/// <summary>服务端限制,由配置绑定。</summary>
public sealed class ServerLimits
{
    public int MaxPayloadBytes { get; set; } = (1 << 20) + 16;
    public int MaxFramesPerItem { get; set; } = 65_536;
    public long MaxChannelBytes { get; set; } = 1L << 30;
    public long MaxWorkspaceBytes { get; set; } = 1L << 40;
    public long MaxWorkspaceChannelBytes { get; set; } = 10L << 30;
    /// <summary>最大账号成员数。属性名和 info 字段保持旧线格式兼容。</summary>
    public int MaxMembers { get; set; } = 64;
    public int MaxVisitors { get; set; } = 10_000;
    public int MinTtlSeconds { get; set; } = 60;
    public int MaxTtlSeconds { get; set; } = 604_800;
    public int MaxItemsLimit { get; set; } = 10_000;
    public int InlineThresholdBytes { get; set; } = 64 * 1024;
    public int DownloadGraceSeconds { get; set; } = 300;
    public int TombstoneRetentionSeconds { get; set; } = 604_800;
}

public static class ServerSettingChoices
{
    public static readonly int[] FileMaxDownloads = [0, 1, 3, 5, 10, 20];
    public static bool IsFileMaxDownloadsAllowed(long value, int currentDefault) => value == currentDefault
        || value is >= int.MinValue and <= int.MaxValue && Array.IndexOf(FileMaxDownloads, (int)value) >= 0;
}

public sealed class ChannelSettings
{
    [JsonPropertyName("join_policy")] public JoinPolicy JoinPolicy { get; set; } = JoinPolicy.Open;
    [JsonPropertyName("name")] public string? Name { get; set; }
    /// <summary>成员人数上限;线字段名保留为 seats 以兼容已有频道设置。</summary>
    [JsonPropertyName("max_members")] public int MaxMembers { get; set; } = 2;
    [JsonPropertyName("members_can_upload")] public bool MembersCanUpload { get; set; } = true;
    [JsonPropertyName("delete_policy")] public DeletePolicy DeletePolicy { get; set; } = DeletePolicy.Own;
    [JsonPropertyName("ttl_seconds")] public int TtlSeconds { get; set; } = 86_400;
    [JsonPropertyName("max_items")] public int MaxItems { get; set; } = 1000;
    [JsonPropertyName("file_max_downloads")] public int FileMaxDownloads { get; set; } = 10;
    [JsonPropertyName("ui_restrict_copy_download")] public bool UiRestrictCopyDownload { get; set; }

    public void Validate(ServerLimits limits)
    {
        if (!Enum.IsDefined(JoinPolicy)) throw new WebDropException(ErrorCode.BadRequest);
        if (Name is { } name && (name.Length > 48 || name.Any(char.IsControl))) throw new WebDropException(ErrorCode.BadRequest);
        if (MaxMembers < 1 || MaxMembers > limits.MaxMembers) throw new WebDropException(ErrorCode.BadRequest);
        if (TtlSeconds < limits.MinTtlSeconds || TtlSeconds > limits.MaxTtlSeconds) throw new WebDropException(ErrorCode.BadRequest);
        if (MaxItems < 1 || MaxItems > limits.MaxItemsLimit) throw new WebDropException(ErrorCode.BadRequest);
        if (FileMaxDownloads < 0) throw new WebDropException(ErrorCode.BadRequest);
    }
}

public sealed class ChannelSettingsPatch
{
    [JsonPropertyName("join_policy")] public JoinPolicy? JoinPolicy { get; init; }
    [JsonPropertyName("join_password")] public string? JoinPassword { get; init; }
    [JsonPropertyName("name")] public string? Name { get; init; }
    [JsonPropertyName("max_members")] public int? MaxMembers { get; init; }
    [JsonPropertyName("members_can_upload")] public bool? MembersCanUpload { get; init; }
    [JsonPropertyName("delete_policy")] public DeletePolicy? DeletePolicy { get; init; }
    [JsonPropertyName("ttl_seconds")] public int? TtlSeconds { get; init; }
    [JsonPropertyName("max_items")] public int? MaxItems { get; init; }
    [JsonPropertyName("file_max_downloads")] public int? FileMaxDownloads { get; init; }
    [JsonPropertyName("ui_restrict_copy_download")] public bool? UiRestrictCopyDownload { get; init; }
    /// <summary>空间头像 data URL;不传表示不改,空字符串表示移除。只有空间主能改。</summary>
    [JsonPropertyName("avatar")] public string? Avatar { get; init; }
    /// <summary>空间头像的有损小图(data URL):空间列表、标题默认只分发它,原图在预览时才下载</summary>
    [JsonPropertyName("avatar_thumb")] public string? AvatarThumb { get; init; }

    public ChannelSettings ApplyTo(ChannelSettings s) => new()
    {
        JoinPolicy = JoinPolicy ?? s.JoinPolicy,
        Name = Name is null ? s.Name : string.IsNullOrWhiteSpace(Name) ? null : Name.Trim(),
        MaxMembers = MaxMembers ?? s.MaxMembers,
        MembersCanUpload = MembersCanUpload ?? s.MembersCanUpload,
        DeletePolicy = DeletePolicy ?? s.DeletePolicy,
        TtlSeconds = TtlSeconds ?? s.TtlSeconds,
        MaxItems = MaxItems ?? s.MaxItems,
        FileMaxDownloads = FileMaxDownloads ?? s.FileMaxDownloads,
        UiRestrictCopyDownload = UiRestrictCopyDownload ?? s.UiRestrictCopyDownload,
    };
}

public sealed class ShareSettings
{
    [JsonPropertyName("ttl_seconds")] public int TtlSeconds { get; set; } = 86_400;
    [JsonPropertyName("max_visitors")] public int MaxVisitors { get; set; }
    [JsonPropertyName("file_max_downloads")] public int FileMaxDownloads { get; set; } = 10;

    public void Validate(ServerLimits limits)
    {
        if (TtlSeconds < limits.MinTtlSeconds || TtlSeconds > limits.MaxTtlSeconds
            || MaxVisitors < 0 || MaxVisitors > limits.MaxVisitors
            || FileMaxDownloads < 0)
            throw new WebDropException(ErrorCode.BadRequest);
    }
}

public sealed class ShareSettingsPatch
{
    [JsonPropertyName("ttl_seconds")] public int? TtlSeconds { get; init; }
    [JsonPropertyName("max_visitors")] public int? MaxVisitors { get; init; }
    [JsonPropertyName("file_max_downloads")] public int? FileMaxDownloads { get; init; }

    public ShareSettings ApplyTo(ShareSettings s) => new()
    {
        TtlSeconds = TtlSeconds ?? s.TtlSeconds,
        MaxVisitors = MaxVisitors ?? s.MaxVisitors,
        FileMaxDownloads = FileMaxDownloads ?? s.FileMaxDownloads,
    };
}

/// <summary>创建接口与 /info 使用同一个配置来源；旧存储对象的字段默认值不作迁移。</summary>
public static class CreationDefaults
{
    public const ChannelMode ChannelMode = WebDrop.Core.ChannelMode.Enc;

    public static ChannelSettings Channel(ServerLimits limits) => new()
    {
        JoinPolicy = JoinPolicy.Invite,
        MaxMembers = Math.Min(10, limits.MaxMembers),
        TtlSeconds = Math.Clamp(86_400, limits.MinTtlSeconds, limits.MaxTtlSeconds),
        MaxItems = Math.Min(1000, limits.MaxItemsLimit),
    };
    public static ShareSettings Share(ServerLimits limits) => new()
    {
        TtlSeconds = Math.Clamp(86_400, limits.MinTtlSeconds, limits.MaxTtlSeconds),
        MaxVisitors = Math.Min(10, limits.MaxVisitors),
    };
}