using System;
using System.Text;

using Server.Accounting;
using Server.Commands;
using Server.Mobiles;

namespace Server.Custom.Bridge
{
    /// <summary>
    ///     EventSink subscriptions. Every handler runs on the Core thread, synchronously, inside
    ///     the code path that raised it. Three rules, all load-bearing:
    ///
    ///       1. Never block. Emit() enqueues and returns; that is the only I/O allowed here.
    ///       2. Never throw. A bridge exception escaping into a game code path is a shard bug,
    ///          so every handler body is wrapped.
    ///       3. Never mutate the args. Several of these are veto hooks — AccountLogin has
    ///          Accepted/RejectReason, FastWalk has Blocked — and we are an observer, not a
    ///          participant.
    ///
    ///     Copy primitives out synchronously. Some args objects are pooled and freed immediately
    ///     after the event returns.
    /// </summary>
    public static class BridgeEvents
    {
        public static void Initialize()
        {
            if (!BridgeConfig.Enabled)
                return;

            // Session
            EventSink.Login += OnLogin;
            EventSink.Logout += OnLogout;
            EventSink.AccountLogin += OnAccountLogin;

            // Economy
            EventSink.AccountGoldChange += OnGoldChange;
            EventSink.ValidVendorPurchase += OnVendorPurchase;
            EventSink.ValidVendorSell += OnVendorSell;
            EventSink.PlacePlayerVendor += OnVendorPlaced;

            // Progression
            EventSink.SkillGain += OnSkillGain;
            EventSink.FameChange += OnFameChange;
            EventSink.KarmaChange += OnKarmaChange;
            EventSink.QuestComplete += OnQuestComplete;

            // Death
            EventSink.PlayerDeath += OnPlayerDeath;
            EventSink.PlayerMurdered += OnPlayerMurdered;
            EventSink.OnKilledBy += OnKilledBy;

            // Cheat detection and staff audit
            EventSink.FastWalk += OnFastWalk;
            EventSink.OnPropertyChanged += OnStaffPropertySet;
            EventSink.Command += OnStaffCommand;

            // Save boundaries
            EventSink.BeforeWorldSave += OnBeforeWorldSave;
            EventSink.AfterWorldSave += OnAfterWorldSave;

            Console.WriteLine("[Bridge] event streams attached");
        }

        // ---- helpers ----

        /// <summary>Writes a nested actor object: serial, name, and account when there is one.</summary>
        private static StringBuilder Mob(this StringBuilder sb, string field, Mobile m)
        {
            sb.Append(",\"").Append(field).Append("\":");

            if (m == null)
            {
                sb.Append("null");
                return sb;
            }

            sb.Append("{\"serial\":\"0x").Append(m.Serial.Value.ToString("X")).Append('"');

            sb.Append(",\"name\":");
            BridgeJson.Escape(sb, m.Name ?? "");

            var acct = m.Account as Account;

            if (acct != null)
            {
                sb.Append(",\"acct\":");
                BridgeJson.Escape(sb, acct.Username);
            }

            sb.Append(",\"player\":").Append(m.Player ? "true" : "false");
            sb.Append('}');

            return sb;
        }

        private static long ToGold(double currency)
        {
            return (long)(currency * Account.CurrencyThreshold);
        }

        private static void Guard(string kind, Action body)
        {
            try
            {
                body();
            }
            catch (Exception ex)
            {
                // Swallow: we are inside a game code path and must not disturb it.
                Console.WriteLine("[Bridge] handler '{0}' threw: {1}", kind, ex.Message);
            }
        }

        // ---- session ----

        private static void OnLogin(LoginEventArgs e)
        {
            Guard("mob.login", () =>
            {
                var m = e.Mobile;

                if (m == null)
                    return;

                // Carry the linked website id on the login anchor so the sidecar can attribute
                // this session (and everything after it) to a site user without a lookup.
                var webId = BridgeAccountLink.WebIdFor(m.Account as Account);

                var sb = BridgeJson.Begin("mob.login")
                    .Mob("who", m)
                    .Str("map", m.Map == null ? null : m.Map.Name)
                    .Num("x", m.X).Num("y", m.Y).Num("z", m.Z);

                if (webId != null)
                    sb.Str("webId", webId);

                BridgeLink.Emit(sb.End());
            });
        }

        private static void OnLogout(LogoutEventArgs e)
        {
            Guard("mob.logout", () =>
            {
                var m = e.Mobile;

                if (m == null)
                    return;

                BridgeLink.Emit(BridgeJson.Begin("mob.logout").Mob("who", m).End());
            });
        }

        /// <summary>
        ///     Veto hook: AccountLoginEventArgs carries Accepted and RejectReason, and a plaintext
        ///     Password. We read the username only. The password must never leave the process.
        ///     Fires before the auth decision, so this is an attempt, not a result.
        /// </summary>
        private static void OnAccountLogin(AccountLoginEventArgs e)
        {
            Guard("account.login.attempt", () =>
            {
                string address = null;

                if (e.State != null && e.State.Address != null)
                    address = e.State.Address.ToString();

                BridgeLink.Emit(BridgeJson.Begin("account.login.attempt")
                    .Str("acct", e.Username)
                    .Str("ip", address)
                    .End());
            });
        }

        // ---- economy ----

        private static void OnGoldChange(AccountGoldChangeEventArgs e)
        {
            Guard("gold.change", () =>
            {
                var acct = e.Account as Account;

                if (acct == null)
                    return;

                long oldGold = ToGold(e.OldAmount);
                long newGold = ToGold(e.NewAmount);

                BridgeLink.Emit(BridgeJson.Begin("gold.change")
                    .Str("acct", acct.Username)
                    .Num("old", oldGold)
                    .Num("new", newGold)
                    .Num("delta", newGold - oldGold)
                    .End());
            });
        }

        /// <summary>
        ///     ValidVendorPurchase is a validation-stage hook, not a committed sale. Treat as
        ///     "attempted". Total is AmountPerUnit times the stack size, not AmountPerUnit.
        /// </summary>
        private static void OnVendorPurchase(ValidVendorPurchaseEventArgs e)
        {
            Guard("vendor.buy", () => EmitVendorTrade("vendor.buy", e.Mobile, e.Vendor, e.Bought, e.AmountPerUnit));
        }

        private static void OnVendorSell(ValidVendorSellEventArgs e)
        {
            Guard("vendor.sell", () => EmitVendorTrade("vendor.sell", e.Mobile, e.Vendor, e.Sold, e.AmountPerUnit));
        }

        private static void EmitVendorTrade(string kind, Mobile who, Mobile vendor, IEntity entity, int perUnit)
        {
            int amount = 1;
            var item = entity as Item;

            if (item != null)
                amount = Math.Max(1, item.Amount);

            var sb = BridgeJson.Begin(kind)
                .Mob("who", who)
                .Mob("vendor", vendor)
                .Str("item", entity == null ? null : entity.GetType().Name)
                .Num("amount", amount)
                .Num("perUnit", perUnit)
                .Num("total", (long)perUnit * amount)
                .Bool("committed", false); // validation stage; reconcile against gold.change

            if (entity != null)
                sb.Ser("itemSerial", entity.Serial);

            BridgeLink.Emit(sb.End());
        }

        private static void OnVendorPlaced(PlacePlayerVendorEventArgs e)
        {
            Guard("vendor.placed", () =>
                BridgeLink.Emit(BridgeJson.Begin("vendor.placed")
                    .Mob("owner", e.Mobile)
                    .Mob("vendor", e.Vendor)
                    .End()));
        }

        // ---- progression ----

        /// <summary>
        ///     Player-only. SkillGain fires for creatures too, and they train constantly: on this
        ///     shard a single boot produced 115 gains in four seconds, every one of them an NPC
        ///     grinding Meditation. Unfiltered this is a firehose of noise.
        /// </summary>
        private static void OnSkillGain(SkillGainEventArgs e)
        {
            Guard("skill.gain", () =>
            {
                if (e.Skill == null || e.From == null || !e.From.Player)
                    return;

                BridgeLink.Emit(BridgeJson.Begin("skill.gain")
                    .Mob("who", e.From)
                    .Str("skill", e.Skill.SkillName.ToString())
                    .Num("gained", e.Gained)
                    .Num("base", e.Skill.Base)
                    .Num("cap", e.Skill.Cap)
                    .End());
            });
        }

        private static void OnFameChange(FameChangeEventArgs e)
        {
            Guard("fame.change", () =>
            {
                if (e.Mobile == null || !e.Mobile.Player)
                    return;

                BridgeLink.Emit(BridgeJson.Begin("fame.change")
                    .Mob("who", e.Mobile)
                    .Num("old", e.OldValue)
                    .Num("new", e.NewValue)
                    .End());
            });
        }

        private static void OnKarmaChange(KarmaChangeEventArgs e)
        {
            Guard("karma.change", () =>
            {
                if (e.Mobile == null || !e.Mobile.Player)
                    return;

                BridgeLink.Emit(BridgeJson.Begin("karma.change")
                    .Mob("who", e.Mobile)
                    .Num("old", e.OldValue)
                    .Num("new", e.NewValue)
                    .End());
            });
        }

        private static void OnQuestComplete(QuestCompleteEventArgs e)
        {
            Guard("quest.complete", () =>
                BridgeLink.Emit(BridgeJson.Begin("quest.complete")
                    .Mob("who", e.Mobile)
                    .Str("quest", e.QuestType == null ? null : e.QuestType.Name)
                    .End()));
        }

        // ---- death ----

        private static void OnPlayerDeath(PlayerDeathEventArgs e)
        {
            Guard("player.death", () =>
                BridgeLink.Emit(BridgeJson.Begin("player.death")
                    .Mob("who", e.Mobile)
                    .Mob("killer", e.Killer)
                    .End()));
        }

        private static void OnPlayerMurdered(PlayerMurderedEventArgs e)
        {
            Guard("player.murdered", () =>
                BridgeLink.Emit(BridgeJson.Begin("player.murdered")
                    .Mob("victim", e.Victim)
                    .Mob("murderer", e.Murderer)
                    .End()));
        }

        /// <summary>
        ///     Fires for creatures too. Only a kill involving a player is interesting, and filtering
        ///     here rather than in the sidecar keeps the mob-grinding firehose off the socket.
        /// </summary>
        private static void OnKilledBy(OnKilledByEventArgs e)
        {
            Guard("mob.killed", () =>
            {
                var killed = e.Killed;
                var killer = e.KilledBy;

                bool involvesPlayer = (killed != null && killed.Player) || (killer != null && killer.Player);

                if (!involvesPlayer)
                    return;

                BridgeLink.Emit(BridgeJson.Begin("mob.killed")
                    .Mob("killed", killed)
                    .Mob("killer", killer)
                    .End());
            });
        }

        // ---- cheat detection and staff audit ----

        /// <summary>
        ///     Veto hook: FastWalkEventArgs.Blocked gates the move. Read only. The args carry only
        ///     a NetState, and NetState.Mobile can be null mid-handshake.
        /// </summary>
        private static void OnFastWalk(FastWalkEventArgs e)
        {
            Guard("cheat.fastwalk", () =>
            {
                var state = e.NetState;

                if (state == null)
                    return;

                var sb = BridgeJson.Begin("cheat.fastwalk")
                    .Mob("who", state.Mobile);

                if (state.Address != null)
                    sb.Str("ip", state.Address.ToString());

                BridgeLink.Emit(sb.End());
            });
        }

        /// <summary>
        ///     Raised only from Scripts/Commands/Properties.cs, i.e. staff `[set`. This is a
        ///     GM-abuse audit trail, not a stat-change stream. One of its three raise sites passes
        ///     a null Mobile, so the staffer is not always known.
        /// </summary>
        private static void OnStaffPropertySet(OnPropertyChangedEventArgs e)
        {
            Guard("audit.set", () =>
            {
                if (e.Property == null)
                    return;

                var sb = BridgeJson.Begin("audit.set")
                    .Mob("staff", e.Mobile)
                    .Str("prop", e.Property.Name)
                    .Str("target", e.Instance == null ? null : e.Instance.GetType().Name)
                    .Str("old", e.OldValue == null ? null : e.OldValue.ToString())
                    .Str("new", e.NewValue == null ? null : e.NewValue.ToString());

                var ent = e.Instance as IEntity;

                if (ent != null)
                    sb.Ser("targetSerial", ent.Serial);

                BridgeLink.Emit(sb.End());
            });
        }

        private static void OnStaffCommand(CommandEventArgs e)
        {
            Guard("audit.command", () =>
            {
                if (e.Mobile == null || e.Mobile.AccessLevel <= AccessLevel.Player)
                    return; // player commands are noise; staff commands are the audit trail

                BridgeLink.Emit(BridgeJson.Begin("audit.command")
                    .Mob("staff", e.Mobile)
                    .Str("command", e.Command)
                    .Str("args", e.ArgString)
                    .End());
            });
        }

        // ---- save boundaries ----

        private static void OnBeforeWorldSave(BeforeWorldSaveEventArgs e)
        {
            Guard("world.save.before", () =>
                BridgeLink.Emit(BridgeJson.Begin("world.save.before").End()));
        }

        /// <summary>
        ///     A natural checkpoint: the sidecar can treat this as a consistency boundary. Note that
        ///     timers and inbound commands do not run during the save itself.
        /// </summary>
        private static void OnAfterWorldSave(AfterWorldSaveEventArgs e)
        {
            Guard("world.save.after", () =>
                BridgeLink.Emit(BridgeJson.Begin("world.save.after")
                    .Num("items", World.Items.Count)
                    .Num("mobiles", World.Mobiles.Count)
                    .End()));
        }
    }
}