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

namespace ytLive.Models;

/// <summary>The session's scoreboard tallies — the facts a creator puts on screen to prove the
/// channel is moving.
///
/// <para>Scope is the RUNNING SESSION (creator ruling 2026-10-30): the counts start at zero when a
/// session starts and die with it. No persistence, nothing to reconcile, and every number is true
/// for exactly what this session saw — a stored "today" that survives a Windows restart would be
/// right only for the hours the app happened to be running, which is a lie the creator cannot
/// check.</para>
///
/// <para>The two polled tiles (subscribers, watch hours) are NOT here: they are channel state, not
/// session events, and live on the polled side of the scoreboard.</para></summary>
public sealed class ScoreboardState
{
    /// <summary>Super Chat + Super Sticker money, per currency. Adding across currencies would be
    /// the one arithmetic nobody forgives, so totals are keyed and only the dominant one is shown.</summary>
    private readonly Dictionary<string, double> _moneyByCurrency = new(StringComparer.OrdinalIgnoreCase);

    public string? LastMemberName { get; private set; }
    public string? LastSuperChatAuthor { get; private set; }
    public string? LastSuperChatDisplay { get; private set; }
    public double LastSuperChatAmount { get; private set; }
    public string? LastSuperChatCurrency { get; private set; }
    public string? LastGifterName { get; private set; }
    public int LastGiftCount { get; private set; }

    /// <summary>Members gained this session: paid memberships plus gifted ones (counted once, from
    /// the GIFT PURCHASE — see <see cref="Apply"/>).</summary>
    public int NewMembers { get; private set; }

    public int MilestoneCount { get; private set; }

    public IReadOnlyDictionary<string, double> MoneyByCurrency => _moneyByCurrency;

    /// <summary>The session's dominant currency (most money) and its total, or ("", 0) when nothing
    /// has come in. Chosen by VALUE so a single EUR tip beside ten USD cents cannot flip the display
    /// to the smaller currency.</summary>
    public (string Currency, double Total) SessionTotal =>
        _moneyByCurrency.Count == 0
            ? (string.Empty, 0)
            : _moneyByCurrency.OrderByDescending(pair => pair.Value).First() is var top
                ? (top.Key, top.Value)
                : (string.Empty, 0);

    public bool HasMixedCurrencies => _moneyByCurrency.Count > 1;

    /// <summary>Folds one chat message into the tallies. Every event kind the poll decodes is
    /// handled; plain chat is ignored.
    ///
    /// <para><b>giftMembershipReceivedEvent deliberately does nothing.</b> It is the RECIPIENT's view
    /// of a purchase already counted by membershipGiftingEvent, so counting it would double both the
    /// members and the money (creator ruling 2026-10-30: "come on").</para></summary>
    public void Apply(ChatMessage message)
    {
        switch (message.Kind)
        {
            case ChatEventKind.NewMember:
                NewMembers++;
                LastMemberName = message.AuthorName;
                break;

            case ChatEventKind.MemberGift:
                // The purchase: one event carrying how many memberships were bought.
                var count = Math.Max(1, message.GiftNewMembersCount);
                NewMembers += count;
                LastGiftCount = count;
                LastGifterName = message.AuthorName;
                break;

            case ChatEventKind.GiftReceived:
                break;   // recipient side of the event above — never counted

            case ChatEventKind.MemberMilestone:
                MilestoneCount++;
                break;

            case ChatEventKind.SuperChat:
            case ChatEventKind.SuperSticker:
                LastSuperChatAuthor = message.AuthorName;
                LastSuperChatAmount = message.SuperChatAmount;
                LastSuperChatCurrency = string.IsNullOrWhiteSpace(message.SuperChatCurrency)
                    ? "USD"
                    : message.SuperChatCurrency!;
                LastSuperChatDisplay = message.SuperChatDisplayString
                    ?? FormatMoney(LastSuperChatAmount, LastSuperChatCurrency);
                if (message.SuperChatAmount > 0)
                {
                    _moneyByCurrency.TryGetValue(LastSuperChatCurrency!, out var running);
                    _moneyByCurrency[LastSuperChatCurrency!] = running + message.SuperChatAmount;
                }
                break;
        }
    }

    /// <summary>A new session starts from zero.</summary>
    public void Reset() => CopyFrom(new ScoreboardState());

    private void CopyFrom(ScoreboardState other)
    {
        _moneyByCurrency.Clear();
        foreach (var pair in other._moneyByCurrency) _moneyByCurrency[pair.Key] = pair.Value;
        LastMemberName = other.LastMemberName;
        LastSuperChatAuthor = other.LastSuperChatAuthor;
        LastSuperChatDisplay = other.LastSuperChatDisplay;
        LastSuperChatAmount = other.LastSuperChatAmount;
        LastSuperChatCurrency = other.LastSuperChatCurrency;
        LastGifterName = other.LastGifterName;
        LastGiftCount = other.LastGiftCount;
        NewMembers = other.NewMembers;
        MilestoneCount = other.MilestoneCount;
    }

    private static string FormatMoney(double amount, string? currency) =>
        string.IsNullOrEmpty(currency) ? amount.ToString("0.00") : $"{currency} {amount:0.00}";
}