using System;
using System.Collections.Generic;
using System.Text;

using Server.Items;
using Server.Mobiles;
using Server.Multis;
using Server.Engines.VendorSearching;

namespace Server.Custom.Bridge
{
    /// <summary>
    ///     The shard-wide player-vendor index (https://gitea.whitlocktech.com/RunicGateway/docs/src/branch/main/link/v3.md §8). Every player vendor's
    ///     shop name, owner, location and priced inventory, published as one authoritative
    ///     <c>vendor.listing</c> frame per vendor, so the website can offer the search the in-game
    ///     Vendor Search gump offers — from outside the game.
    ///
    ///     ---- Why this is a sweep and not an RPC ----
    ///
    ///     The obvious shape is a <c>market.snapshot</c> request/reply like vendor.snapshot next
    ///     door. It cannot work: the sidecar's rpc router correlates on the FIRST frame carrying a
    ///     matching reqId and resolves a single oneshot, so a chunked reply sharing one reqId would
    ///     deliver chunk 1 to the HTTP caller and LEAK chunks 2..N onto the broadcast feed. A
    ///     whole-world snapshot in one frame is not an option either — the reply timeout is 10 s and
    ///     40,000 listings do not serialize in time.
    ///
    ///     So it is a diff sweep on the broadcast stream, shaped like <see cref="BridgeHousing"/>:
    ///     one frame per vendor, authoritative for that vendor, plus vendor.listing.remove when one
    ///     goes away. The per-account <c>vendor.snapshot</c> RPC is untouched; the player portal
    ///     keeps using it.
    ///
    ///     ---- The two perf traps, and what this does about them ----
    ///
    ///     1. **VendorSearch.GetItemName is a packet builder, not a field read.** It constructs an
    ///        ObjectPropertyList, calls GetProperties, serialises it and then byte-parses the
    ///        resulting packet — PER ITEM. Across a full pass that is a multi-hundred-millisecond
    ///        stall on the Core thread. It is never called here. The frame carries `itemId`, `hue`,
    ///        `amount`, `price`, the plain `item.Name` field (null for most items) and
    ///        `item.LabelNumber`; the website resolves display names against its own cliloc table,
    ///        exactly as char.profile.equipment already does.
    ///
    ///        (On any modern client the call would not even work: every current client ships its
    ///        Cliloc.* files compressed, ServUO's bundled Ultima.StringList reads only the old plain
    ///        layout, so VendorSearch.StringList is null and GetItemName returns item.Name anyway.
    ///        The in-game gump has the same gap.)
    ///
    ///     2. **A full pass is unbounded in world size.** 500 vendors × 80 listings is ~40,000 item
    ///        reads, and the reusable public GetItems(Container, List&lt;Item&gt;) recurses into
    ///        sub-containers, so the real count runs ABOVE the top-level pack.Items a naive estimate
    ///        would use. So the sweep is amortized: a persistent round-robin cursor over
    ///        PlayerVendor.PlayerVendors advances at most MarketSweepBatch vendors per tick, which
    ///        makes the PER-TICK cost bounded independently of how many vendors exist. Full coverage
    ///        takes ceil(vendors / batch) × MarketSweepSeconds. This is the one genuinely new pattern
    ///        versus the other sweeps, which all walk their whole collection every tick.
    ///
    ///     ---- Privacy ----
    ///
    ///     `pv.VendorSearch` is ServUO's own per-vendor opt-out and DoSearch filters on it, so a
    ///     player who hid their vendor in game is hidden on the website too: an opted-out vendor is
    ///     skipped entirely and the seen-set removal then drops it from the board. Map.Internal and
    ///     a null Backpack are skipped for the same reason DoSearch skips them.
    ///
    ///     Owner is written as flat `ownerSerial`/`ownerName` — never through BridgeJson.Actor,
    ///     which would add `acct` and `webId`. Same argument BridgePoints makes: this is the widest-
    ///     audience surface the bridge has, and the site resolves serial → user from its own
    ///     shard_account_links mirror when staff need it.
    /// </summary>
    public static class BridgeMarket
    {
        private static Timer _timer;

        // vendor serial -> last-emitted signature.
        private static readonly Dictionary<Serial, string> _last = new Dictionary<Serial, string>();

        // Round-robin cursor: an INDEX into PlayerVendor.PlayerVendors, not a serial. The list is
        // mutated by placement/deletion between ticks, so the cursor is a hint, not a promise — it
        // is wrapped and clamped every tick, and a shifted list at worst re-visits or defers a
        // vendor by one cycle. Tracking a serial instead would cost a lookup to find "where was I"
        // and buy nothing: the sweep is idempotent per vendor.
        private static int _cursor;

        private static long _sweeps, _emitted, _removed, _scanned, _skipped, _truncated;

        // Per-tick cost, in milliseconds. Reported by `[bridge status` because the
        // whole design of this sweep is a claim about that number — the batch cap is what makes it
        // independent of world size — and an operator tuning MarketSweepBatch is otherwise tuning
        // blind. `_maxMs` is the one that matters: the Core thread runs this between frames, so the
        // worst tick is the budget, not the average.
        private static double _lastMs, _maxMs;
        private static readonly System.Diagnostics.Stopwatch _clock = new System.Diagnostics.Stopwatch();

        // Reused across ticks. The item walk is single-threaded (Core thread) and the list is
        // cleared before each vendor, so one buffer serves the whole sweep — the alternative is a
        // fresh List<Item> per vendor per tick, which at 25 vendors × every 60 s is pure garbage.
        private static readonly List<Item> _items = new List<Item>();

        public static void Initialize()
        {
            if (!BridgeConfig.Enabled)
                return;

            EventSink.ServerStarted += OnServerStarted;
        }

        private static void OnServerStarted()
        {
            BridgeLink.Connected_Core += OnConnected;
            Rearm();
        }

        private static void OnConnected()
        {
            // A new sidecar knows nothing, so drop the diff state and start the round-robin from
            // the top. The re-emit of the whole world is self-throttled by the batch window — this
            // is the one place the amortized sweep pays for itself twice, because a reconnect on a
            // whole-world sweep would otherwise be the biggest burst the bridge ever produces.
            _last.Clear();
            _cursor = 0;
        }

        /// <summary>Stops and recreates the timer from current config. Called by `[bridge reload`.</summary>
        public static void Rearm()
        {
            Stop();

            _timer = Timer.DelayCall(
                TimeSpan.FromSeconds(BridgeConfig.MarketSweepSeconds),
                TimeSpan.FromSeconds(BridgeConfig.MarketSweepSeconds),
                MarketSweep);
        }

        public static void Stop()
        {
            if (_timer != null) { _timer.Stop(); _timer = null; }
        }

        /// <summary>
        ///     A bare (key-less) string value, or JSON null.
        ///
        ///     <see cref="BridgeJson.Escape"/> takes a non-null string — it dereferences
        ///     <c>value.Length</c> immediately — and <see cref="BridgeJson.Str"/> writes the `,"key":`
        ///     prefix itself, so neither serves a value written inside a hand-built object. Most of
        ///     what this frame writes is legitimately null (an item's plain Name is null for nearly
        ///     every item, a vendor standing in the street has no house), so this is the common path
        ///     rather than an edge case.
        /// </summary>
        private static void Text(StringBuilder sb, string value)
        {
            if (value == null)
                sb.Append("null");
            else
                BridgeJson.Escape(sb, value);
        }

        public static string Status()
        {
            var all = PlayerVendor.PlayerVendors;

            return String.Format(
                "market(enabled={0} sweeps={1} scanned={2} emitted={3} removed={4} skipped={5} truncated={6} tracked={7} vendors={8} cursor={9} batch={10} lastMs={11:F2} maxMs={12:F2})",
                BridgeConfig.MarketEnabled, _sweeps, _scanned, _emitted, _removed, _skipped,
                _truncated, _last.Count, all == null ? 0 : all.Count, _cursor,
                BridgeConfig.MarketSweepBatch, _lastMs, _maxMs);
        }

        /// <summary>Runs one sweep now. Wired into `[bridge sweepnow`.</summary>
        public static void SweepOnce()
        {
            MarketSweep();
        }

        /// <summary>
        ///     One tick: at most <c>MarketSweepBatch</c> vendors starting at the cursor, then the
        ///     removal pass.
        ///
        ///     The removal pass is the part the batching makes subtle. `_last` holds every vendor
        ///     seen in ANY previous tick, but this tick only visited a window — so "not in this
        ///     tick's seen set" does NOT mean gone. Removals are therefore decided against the
        ///     CURRENT vendor list (plus the opt-out/validity rules), not against the window, which
        ///     is a cheap pass over serials rather than a second inventory walk.
        /// </summary>
        private static void MarketSweep()
        {
            try
            {
                if (!BridgeConfig.MarketEnabled)
                    return;

                _sweeps++;

                if (!BridgeLink.Connected)
                    return; // nothing is listening; do not fill the queue with perishable snapshots

                _clock.Restart();

                var all = PlayerVendor.PlayerVendors;

                if (all == null || all.Count == 0)
                {
                    Reap(null);
                    return;
                }

                // A live set of every serial that SHOULD be on the board right now, built as the
                // window is walked plus a cheap pass over the rest. Built here rather than reusing
                // a field so a throwing vendor cannot leave a half-built set behind.
                var present = new HashSet<Serial>();

                var count = all.Count;
                var batch = Math.Min(BridgeConfig.MarketSweepBatch, count);

                if (_cursor >= count)
                    _cursor = 0;

                for (int i = 0; i < count; i++)
                {
                    var vendor = all[i];

                    if (Eligible(vendor))
                        present.Add(vendor.Serial);
                }

                for (int n = 0; n < batch; n++)
                {
                    var index = (_cursor + n) % count;
                    var vendor = all[index];

                    if (!Eligible(vendor))
                    {
                        _skipped++;
                        continue;
                    }

                    // One bad vendor must not cost the rest of the window: the item walk touches
                    // arbitrary Item subclasses on a shard running modified scripts.
                    try
                    {
                        SweepVendor(vendor);
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine("[Bridge] market sweep threw for 0x{0:X}: {1}",
                            vendor.Serial.Value, ex.Message);
                    }
                }

                _cursor = count == 0 ? 0 : (_cursor + batch) % count;

                Reap(present);
            }
            catch (Exception ex)
            {
                Console.WriteLine("[Bridge] market sweep threw: {0}", ex.Message);
            }
            finally
            {
                // In `finally` so a throwing tick still records what it cost — a sweep that blows
                // the budget and then throws is exactly the one worth seeing in the status line.
                if (_clock.IsRunning)
                {
                    _clock.Stop();
                    _lastMs = _clock.Elapsed.TotalMilliseconds;
                    if (_lastMs > _maxMs)
                        _maxMs = _lastMs;

                    WarnIfSlow();
                }
            }
        }

        /// <summary>
        ///     Per-tick budget, milliseconds. The batch cap exists to hold a tick under this
        ///     regardless of world size, so exceeding it means MarketSweepBatch is too large for
        ///     this shard's shops — the one thing an operator needs told, and the one thing
        ///     `[bridge status` cannot tell them unprompted. Generous: a tick is off the frame
        ///     budget, and the alternative to a rare 50 ms tick is a permanently stale market.
        /// </summary>
        private const double SlowTickMs = 50.0;

        // At most one warning a minute. A shard whose batch is genuinely too big would otherwise
        // print every MarketSweepSeconds forever, and a log nobody can read is a log nobody reads.
        private static DateTime _lastWarn = DateTime.MinValue;

        private static void WarnIfSlow()
        {
            if (_lastMs <= SlowTickMs)
                return;

            var now = DateTime.UtcNow;

            if (now - _lastWarn < TimeSpan.FromMinutes(1))
                return;

            _lastWarn = now;

            Console.WriteLine(
                // ASCII only. The ServUO console writes in the OS code page, so an em dash here
                // renders as "???" in the log an operator would paste into an issue.
                "[Bridge] market sweep took {0:F1} ms (budget {1:F0} ms) - lower Bridge.MarketSweepBatch (now {2}) if this persists",
                _lastMs, SlowTickMs, BridgeConfig.MarketSweepBatch);
        }

        /// <summary>
        ///     The same filter DoSearch applies, so the website's index is the in-game index.
        ///     <c>VendorSearch</c> is the player's own opt-out toggle and is honoured first.
        /// </summary>
        private static bool Eligible(PlayerVendor vendor)
        {
            return vendor != null
                && !vendor.Deleted
                && vendor.VendorSearch
                && vendor.Map != null
                && vendor.Map != Map.Internal
                && vendor.Backpack != null;
        }

        /// <summary>
        ///     Drops from the board every tracked vendor that is no longer eligible.
        ///     <paramref name="present"/> null means "there are no vendors at all", which clears it.
        /// </summary>
        private static void Reap(HashSet<Serial> present)
        {
            if (_last.Count == 0)
                return;

            List<Serial> gone = null;

            foreach (var serial in _last.Keys)
            {
                if (present != null && present.Contains(serial))
                    continue;

                if (gone == null)
                    gone = new List<Serial>();

                gone.Add(serial);
            }

            if (gone == null)
                return;

            for (int i = 0; i < gone.Count; i++)
            {
                _last.Remove(gone[i]);
                BridgeLink.Emit(BridgeJson.Begin("vendor.listing.remove").Ser("serial", gone[i]).End());
                _removed++;
            }
        }

        private static void SweepVendor(PlayerVendor vendor)
        {
            _scanned++;

            CollectItems(vendor);

            var sig = Signature(vendor);

            string prior;
            if (_last.TryGetValue(vendor.Serial, out prior) && prior == sig)
                return; // nothing about this shop changed since it was last published

            _last[vendor.Serial] = sig;
            BridgeLink.Emit(WriteVendor(vendor));
            _emitted++;
        }

        /// <summary>
        ///     Every sellable item on one vendor, into the shared buffer.
        ///
        ///     Mirrors VendorSearch's own private GetItems(PlayerVendor): the vendor's own movable
        ///     equipment (minus the backpack itself and hair layers, which are not merchandise)
        ///     followed by a recursive walk of the backpack. The recursion uses the PUBLIC
        ///     GetItems(Container, List&lt;Item&gt;) rather than a hand-rolled one so that ServUO's
        ///     rule about which containers are sold whole (quivers, seed boxes, jewelry boxes, …)
        ///     stays ServUO's to define — the predicate that decides it is private, and a copy here
        ///     would silently diverge the first time that list changes.
        /// </summary>
        private static void CollectItems(PlayerVendor vendor)
        {
            _items.Clear();

            var own = vendor.Items;

            if (own != null)
            {
                for (int i = 0; i < own.Count; i++)
                {
                    var item = own[i];

                    if (item == null || !item.Movable || item == vendor.Backpack)
                        continue;

                    if (item.Layer == Layer.Hair || item.Layer == Layer.FacialHair)
                        continue;

                    _items.Add(item);
                }
            }

            if (vendor.Backpack != null)
                VendorSearch.GetItems(vendor.Backpack, _items);
        }

        /// <summary>
        ///     A listing's price, and whether it was priced by an enclosing container.
        ///
        ///     ServUO prices a container as a unit: an item inside a priced bag has no VendorItem of
        ///     its own and inherits the bag's price, which DoSearch surfaces as `isChild`. Reproduced
        ///     exactly, because a website that priced every item in a 40k bag at 40k would be lying
        ///     about the shard.
        /// </summary>
        private static int PriceOf(PlayerVendor vendor, Item item, out bool child)
        {
            child = false;

            var vi = vendor.GetVendorItem(item);

            if (vi != null)
                return vi.Price;

            var parent = item.Parent as Container;

            while (parent != null)
            {
                vi = vendor.GetVendorItem(parent);

                if (vi != null)
                {
                    child = true;
                    return vi.Price;
                }

                parent = parent.Parent as Container;
            }

            return 0;
        }

        /// <summary>
        ///     The diff key. Location, shop name and owner are in it because they move a vendor's
        ///     row on the site; every listing's serial, price and amount are in it because those are
        ///     what a shopper searches on.
        ///
        ///     Built over the SAME buffer the frame is written from, in the same order, so a
        ///     signature match really does mean an identical frame — a cheaper hash (count + a sum
        ///     of serial^price, as §8.3 first proposed) collides on the common case of two items
        ///     swapping prices, which is exactly what re-pricing a shop looks like.
        /// </summary>
        private static string Signature(PlayerVendor vendor)
        {
            var sb = new StringBuilder(256);

            sb.Append(vendor.ShopName ?? "").Append('|');
            sb.Append(vendor.Owner == null ? 0 : vendor.Owner.Serial.Value).Append('|');
            sb.Append(vendor.Map == null ? "" : vendor.Map.Name).Append('|');
            sb.Append(vendor.X).Append(',').Append(vendor.Y).Append('|');

            var limit = Math.Min(_items.Count, BridgeConfig.MarketMaxListings);

            sb.Append(_items.Count).Append('|');

            for (int i = 0; i < limit; i++)
            {
                var item = _items[i];

                if (item == null || item.Deleted)
                    continue;

                bool child;
                var price = PriceOf(vendor, item, out child);

                if (price <= 0)
                    continue;

                sb.Append(item.Serial.Value.ToString("X")).Append(':')
                  .Append(price).Append(':')
                  .Append(item.Amount).Append(';');
            }

            return sb.ToString();
        }

        /// <summary>
        ///     One vendor frame — authoritative for that vendor, so the website replaces its whole
        ///     listing set from it rather than merging.
        ///
        ///     `location` is one nested object rather than flat map/x/y/region because it is ONE
        ///     admin-configurable field on the site (`market.location`): the visibility projection
        ///     matches literal JSON keys, so a nested object is what lets a single rule hide a
        ///     vendor's whereabouts on both the live frame and the stored read model. Flat keys
        ///     would need five rules that could drift apart.
        ///
        ///     `count` is the number of listings PUBLISHED, and `truncated` says the shop holds
        ///     more. A shop over the cap is a real thing (commodity resellers run thousands of
        ///     stacks) and the site says so rather than quietly showing a partial shop as complete.
        /// </summary>
        private static string WriteVendor(PlayerVendor vendor)
        {
            var sb = BridgeJson.Begin("vendor.listing")
                .Ser("serial", vendor.Serial)
                .Str("shopName", vendor.ShopName);

            var owner = vendor.Owner;

            if (owner != null)
            {
                sb.Ser("ownerSerial", owner.Serial);
                sb.Str("ownerName", owner.Name);
            }

            sb.Append(",\"location\":{\"map\":");
            Text(sb, vendor.Map == null ? null : vendor.Map.Name);
            sb.Append(",\"x\":").Append(vendor.X);
            sb.Append(",\"y\":").Append(vendor.Y);
            sb.Append(",\"z\":").Append(vendor.Z);

            var region = vendor.Region;
            sb.Append(",\"region\":");
            Text(sb, region == null ? null : region.Name);

            // The house name is the sign's, which is what a player would be told to look for
            // ("Bob's Villa"), not the house type. Null for a vendor standing outside one.
            var house = vendor.House;
            var sign = house == null ? null : house.Sign;
            sb.Append(",\"house\":");
            Text(sb, sign == null ? null : sign.GetName());

            sb.Append('}');

            var max = BridgeConfig.MarketMaxListings;
            var published = 0;
            var considered = 0;

            var items = new StringBuilder(512);

            for (int i = 0; i < _items.Count; i++)
            {
                var item = _items[i];

                if (item == null || item.Deleted)
                    continue;

                bool child;
                var price = PriceOf(vendor, item, out child);

                // Unpriced items are inventory, not listings — DoSearch drops them the same way.
                if (price <= 0)
                    continue;

                considered++;

                if (published >= max)
                    continue;

                if (published > 0)
                    items.Append(',');

                items.Append("{\"serial\":\"0x").Append(item.Serial.Value.ToString("X")).Append('"');
                items.Append(",\"itemId\":").Append(item.ItemID);
                items.Append(",\"hue\":").Append(item.Hue);
                items.Append(",\"amount\":").Append(item.Amount);
                items.Append(",\"price\":").Append(price);

                // The PLAIN Name field, which is null for most items — never GetItemName, which
                // builds and parses a property packet per item. LabelNumber is the cliloc the
                // website resolves against its own table.
                items.Append(",\"name\":");
                Text(items, item.Name);
                items.Append(",\"cliloc\":").Append(item.LabelNumber);

                if (child)
                    items.Append(",\"child\":true");

                items.Append('}');

                published++;
            }

            sb.Num("count", published);
            sb.Num("total", considered);
            sb.Bool("truncated", considered > published);

            if (considered > published)
                _truncated++;

            sb.Append(",\"items\":[").Append(items).Append(']');

            return sb.End();
        }
    }
}