using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;

namespace SharpChat.EventStorage {
    public class VirtualEventStorage : IEventStorage {
        private readonly Dictionary<long, StoredEventInfo> Events = new();

        public void AddEvent(
            long id, string type,
            object? data = null,
            StoredEventFlags flags = StoredEventFlags.None
        ) {
            AddEvent(id, type, null, 0, null, ChatColour.None, 0, null, 0, data, flags);
        }

        public void AddEvent(
            long id, string type,
            string? channelName,
            object? data = null,
            StoredEventFlags flags = StoredEventFlags.None
        ) {
            AddEvent(id, type, channelName, 0, null, ChatColour.None, 0, null, 0, data, flags);
        }

        public void AddEvent(
            long id, string type,
            long senderId, string? senderName, ChatColour senderColour, int senderRank, string? senderNick, ChatUserPermissions senderPerms,
            object? data = null,
            StoredEventFlags flags = StoredEventFlags.None
        ) {
            AddEvent(id, type, null, senderId, senderName, senderColour, senderRank, senderNick, senderPerms, data, flags);
        }

        public void AddEvent(
            long id, string type,
            string? channelName,
            long senderId, string? senderName, ChatColour senderColour, int senderRank, string? senderNick, ChatUserPermissions senderPerms,
            object? data = null,
            StoredEventFlags flags = StoredEventFlags.None
        ) {
            if(type == null)
                throw new ArgumentNullException(nameof(type));

            // VES is meant as an emergency fallback but this is something else
            JsonDocument hack = JsonDocument.Parse(data == null ? "{}" : JsonSerializer.Serialize(data));
            Events.Add(id, new(id, type, senderId < 1 ? null : new ChatUser(
                senderId,
                senderName,
                senderColour,
                senderRank,
                senderPerms,
                senderNick
            ), DateTimeOffset.Now, null, channelName, hack, flags));
        }

        public long AddEvent(string type, ChatUser user, ChatChannel channel, object? data = null, StoredEventFlags flags = StoredEventFlags.None) {
            if(type == null)
                throw new ArgumentNullException(nameof(type));

            long id = SharpId.Next();

            AddEvent(
                id, type,
                channel?.Name,
                user?.UserId ?? 0,
                user?.UserName,
                user?.Colour ?? ChatColour.None,
                user?.Rank ?? 0,
                user?.NickName,
                user?.Permissions ?? 0,
                data,
                flags
            );

            return id;
        }

        public StoredEventInfo? GetEvent(long seqId) {
            return Events.TryGetValue(seqId, out StoredEventInfo? evt) ? evt : null;
        }

        public void RemoveEvent(StoredEventInfo evt) {
            Events.Remove(evt.Id);
        }

        public IEnumerable<StoredEventInfo> GetChannelEventLog(string channelName, int amount = 20, int offset = 0) {
            IEnumerable<StoredEventInfo> subset = Events.Values.Where(ev => ev.ChannelName == channelName);

            int start = subset.Count() - offset - amount;
            if(start < 0) {
                amount += start;
                start = 0;
            }

            return subset.Skip(start).Take(amount).ToArray();
        }
    }
}