using System;
using System.Collections.Generic;
using System.Linq;

namespace SharpChat {
    public class ChannelsContext {
        private readonly List<ChannelInfo> Channels = new();

        public ChannelInfo? MainChannel { get; private set; }
        public int TotalCount { get; private set; }
        public int PublicCount { get; private set; }

        public ChannelInfo[] All => Channels.ToArray();

        public ChannelInfo? Get(
            string? name,
            Func<string, string>? sanitise = null
        ) {
            if(string.IsNullOrWhiteSpace(name))
                return null;

            foreach(ChannelInfo info in Channels) {
                string chanName = info.Name;
                if(sanitise != null)
                    chanName = sanitise(chanName);
                if(!chanName.Equals(name, StringComparison.InvariantCultureIgnoreCase))
                    continue;

                return info;
            }

            return null;
        }

        public ChannelInfo[] GetMany(
            string[]? names = null,
            Func<string, string>? sanitiseName = null,
            int minRank = 0,
            bool? isPublic = null
        ) {
            List<ChannelInfo> chans = new();

            names ??= Array.Empty<string>();
            for(int i = 0; i < names.Length; ++i)
                names[i] = names[i].ToLowerInvariant();

            foreach(ChannelInfo info in Channels) {
                if(info.Rank > minRank)
                    continue;

                if(isPublic != null && info.IsPublic != isPublic)
                    continue;

                if(names?.Length > 0) {
                    string chanName = info.Name;
                    if(sanitiseName != null)
                        chanName = sanitiseName(chanName);

                    bool match = false;
                    foreach(string name in names)
                        if(match = chanName.Equals(name, StringComparison.InvariantCultureIgnoreCase))
                            break;

                    if(!match)
                        continue;
                }

                chans.Add(info);
            }

            return chans.ToArray();
        }

        public void Add(
            ChannelInfo info,
            bool forceMain = false,
            Func<string, string>? sanitiseName = null
        ) {
            if(Get(info.Name, sanitiseName) != null)
                throw new ArgumentException("A channel with this name has already been registered.", nameof(info));
            if(string.IsNullOrWhiteSpace(info.Name))
                throw new ArgumentException("Channel names may not be blank.", nameof(info));
            // todo: there should be more restrictions on channel names

            Channels.Add(info);

            ++TotalCount;
            if(info.IsPublic)
                ++PublicCount;

            if(forceMain || MainChannel == null)
                MainChannel = info;
        }

        public void Remove(
            ChannelInfo info,
            Func<string, string>? sanitiseName = null
        ) {
            Remove(info.Name, sanitiseName);
        }

        public void Remove(
            string? name,
            Func<string, string>? sanitise = null
        ) {
            if(string.IsNullOrWhiteSpace(name))
                return;

            ChannelInfo? info = Get(name, sanitise);
            if(info == null)
                return;

            Channels.Remove(info);

            --TotalCount;
            if(info.IsPublic)
                --PublicCount;

            if(MainChannel == info)
                MainChannel = Channels.FirstOrDefault(c => !c.IsPublic);
        }
    }
}