using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

using Myriad.Builders;

using PluralKit.Core;

namespace PluralKit.Bot
{
    public class MemberGroup
    {
        private readonly IDatabase _db;
        private readonly ModelRepository _repo;

        public MemberGroup(IDatabase db, ModelRepository repo)
        {
            _db = db;
            _repo = repo;
        }

        public async Task AddRemove(Context ctx, PKMember target, Groups.AddRemoveOperation op)
        {
            ctx.CheckSystem().CheckOwnMember(target);

            var groups = (await ctx.ParseGroupList(ctx.System.Id))
                .Select(g => g.Id)
                .Distinct()
                .ToList();

            await using var conn = await _db.Obtain();
            var existingGroups = (await _repo.GetMemberGroups(conn, target.Id).ToListAsync())
                .Select(g => g.Id)
                .Distinct()
                .ToList();

            List<GroupId> toAction;

            if (op == Groups.AddRemoveOperation.Add)
            {
                toAction = groups
                    .Where(group => !existingGroups.Contains(group))
                    .ToList();

                await _repo.AddGroupsToMember(conn, target.Id, toAction);
            }
            else if (op == Groups.AddRemoveOperation.Remove)
            {
                toAction = groups
                    .Where(group => existingGroups.Contains(group))
                    .ToList();

                await _repo.RemoveGroupsFromMember(conn, target.Id, toAction);
            }
            else return; // otherwise toAction "may be unassigned"

            await ctx.Reply(GroupAddRemoveResponseService.GenerateResponse(op, 1, groups.Count, toAction.Count, groups.Count - toAction.Count));
        }

        public async Task List(Context ctx, PKMember target)
        {
            await using var conn = await _db.Obtain();

            var pctx = ctx.LookupContextFor(target.System);

            var groups = await _repo.GetMemberGroups(conn, target.Id)
                .Where(g => g.Visibility.CanAccess(pctx))
                .OrderBy(g => g.Name, StringComparer.InvariantCultureIgnoreCase)
                .ToListAsync();

            var description = "";
            var msg = "";

            if (groups.Count == 0)
                description = "This member has no groups.";
            else
                description = string.Join("\n", groups.Select(g => $"[`{g.Hid}`] **{g.DisplayName ?? g.Name}**"));

            if (pctx == LookupContext.ByOwner)
            {
                msg += $"\n\nTo add this member to one or more groups, use `pk;m {target.Reference()} group add <group> [group 2] [group 3...]`";
                if (groups.Count > 0)
                    msg += $"\nTo remove this member from one or more groups, use `pk;m {target.Reference()} group remove <group> [group 2] [group 3...]`";
            }

            await ctx.Reply(msg, (new EmbedBuilder().Title($"{target.Name}'s groups").Description(description)).Build());
        }
    }
}