using System;
using System.Collections.Generic;

namespace AcDream.Core.Items;

/// <summary>
/// Domain-shaped projection of the wire <c>ApproachVendor</c> GameEvent's
/// fixed profile prefix (buy/sell rates, currency, categories). The
/// wire-shaped equivalent (<c>VendorApproach.VendorProfile</c>) lives in
/// <c>AcDream.Core.Net.Messages</c>, which <c>AcDream.Core</c> cannot
/// reference (dependency runs <c>AcDream.Core.Net</c> -&gt; <c>AcDream.Core</c>,
/// never the other way). This mirrors how <c>ContainerContentEntry</c>
/// (<see cref="ClientObjectTable"/>) is the domain projection of the wire
/// <c>ViewContentsEntry</c>/<c>CreateObject</c> shapes — the Slice 5.3
/// wiring glue (<c>GameEventWiring.cs</c>, which CAN see both layers) does
/// the field-by-field conversion, the same way it already does for
/// <c>ViewContents</c> today.
/// </summary>
public readonly record struct VendorShopProfile(
    uint MerchandiseItemTypes,
    uint MerchandiseMinValue,
    uint MerchandiseMaxValue,
    bool DealMagicalItems,
    float BuyPrice,
    float SellPrice,
    uint AlternateCurrencyWcid,
    uint AlternateCurrencyAmount,
    string AlternateCurrencyPluralName);

/// <summary>
/// Domain-shaped projection of one <c>ApproachVendor</c> shop-list entry —
/// only the fields Slice 5's browse scope needs (display + price math).
/// The full <c>PublicWeenieDesc</c> the wire carries has ~40 optional
/// fields; the rest are Slice 6+ concerns (or already live on the
/// <see cref="ClientObjectTable"/> record once Slice 5.3 registers each
/// shop item there per the research doc's §A.2 point 4 recommendation).
/// </summary>
public readonly record struct VendorShopItem(
    uint ItemGuid,
    // -1 = unlimited supply (retail ItemProfile's sign-extended packed
    // stack-size field).
    int StackSize,
    uint WeenieClassId,
    string? Name,
    uint? ItemType,
    uint IconId,
    int? Value,
    // Slice 5.3 review fix 2: the ITEM'S OWN authored stack depth (retail
    // PublicWeenieDesc::_stackSize, wire AcDream.Core.Net.Messages.
    // PublicWeenieDescBody.StackSize) -- the divisor VendorPricing.PerUnitValue
    // needs to turn Value's STACK-TOTAL wire number into a per-unit display
    // price (VendorProfile::VendorSellPrice/VendorBuyPrice, 0x005D1B00/
    // 0x005D1B70). This is a DIFFERENT wire field from StackSize above:
    // that one is ItemProfile's packed SUPPLY count (how many the vendor has
    // in stock), this one is how many units make up one priced stack (e.g.
    // 50 for a stack of arrows). Nullable because the wire field is
    // conditionally present (weenieFlags-gated) -- absent maps to null here,
    // matching retail's own zeroed-struct default of 0 for the same case
    // (see VendorPricing.PerUnitValue's <= 0 guard).
    int? DescStackSize = null,
    // Grand-gate finding R1, corrected at the 2026-08-08 live-evidence
    // re-fix (register AP-169, second correction): the item TYPE's authored
    // stack ceiling (retail PublicWeenieDesc::_maxStackSize, wire
    // AcDream.Core.Net.Messages.PublicWeenieDescBody.StackSizeMax). This is
    // retail's PRIMARY vendor-owned quantity operand, read literally by
    // VendorItemsUI::UpdateItemsList (0x004c1ea0, pc:201085-201133 — each
    // browse row displays min(remaining, _maxStackSize), plain
    // _maxStackSize for unlimited supply), InqListSlotCount (pc:200052),
    // and the Buying tab's Buy Item/Clear Item removal rule
    // (gmVendorUI::HandleButtonClicks cases 0x100000c9/0x100000cb,
    // pc:203996/204086) — never the instance _stackSize. The live ACE wire
    // (vendor-diag 2026-08-08) carries descStackSize=1 for every browse
    // row, so any desc-first read collapses every vendor stack to 1 — see
    // VendorSplitPolicy.ResolveAuthoredStackSize (max-first, desc
    // fallback) and the register (AP-169).
    int? MaxStackSize = null,
    // Review finding F5 (Slice 5.4 review): PublicWeenieDescBody already
    // carries these three (IconOverlayId/IconUnderlayId/UiEffects) — see
    // AcDream.Core.Net.Messages.PublicWeenieDescBody. Mirrors
    // ClientObjectTable's ClientObject.IconUnderlayId/IconOverlayId/Effects
    // naming exactly, so VendorUiController can forward them to
    // _resolveIcon the same way ExternalContainerController.CreateCell does
    // (item.Type, item.IconId, item.IconUnderlayId, item.IconOverlayId,
    // item.Effects). 0 = "not sent", same as ClientObject's convention.
    uint IconUnderlayId = 0u,
    uint IconOverlayId = 0u,
    uint Effects = 0u,
    // Review finding F2/F3 (Slice 5.4 review): retail's NAME_PLURAL display
    // (ACCWeenieObject::GetObjectName, pc:409056-409132) reads
    // PublicWeenieDesc::_plural_name -- wire AcDream.Core.Net.Messages.
    // PublicWeenieDescBody.PluralName. Null/empty is a real, retail-modeled
    // case (no plural authored): GetObjectName falls back to the singular
    // Name unchanged, not an auto-pluralized "Name+s".
    string? PluralName = null);

public enum VendorStateTransitionKind
{
    /// <summary>A different vendor than whatever was previously open (or nothing) is now open.</summary>
    Opened,
    /// <summary>The SAME vendor id sent a fresh ApproachVendor (post-buy/sell refresh — Slice 6).</summary>
    Refreshed,
    /// <summary>The shop was closed (client-local distance/switch trigger — retail A.3).</summary>
    Closed,
    /// <summary>Session teardown (portal/reconnect/logout).</summary>
    Reset,
}

public readonly record struct VendorTransition(
    VendorStateTransitionKind Kind,
    uint PreviousVendorId,
    uint VendorId);

/// <summary>
/// Owns the currently-open vendor shop snapshot: the vendor's guid, its
/// shop terms, and its item-for-sale list. Structural sibling of
/// <see cref="ExternalContainerState"/> (Slice 5 contract decision 1) — same
/// "authoritative server-driven full-replace view... with a
/// <c>Changed</c> event for presentation observers" shape, widened to also
/// carry the profile + item list <c>ExternalContainerState</c> doesn't need
/// (a container has no rates/currency/categories of its own).
///
/// <para>
/// <b>No request/current id gating.</b> Unlike <see cref="ExternalContainerState"/>
/// (which tracks a <c>RequestedContainerId</c> separate from
/// <c>CurrentContainerId</c> to survive ACE sending ViewContents for nested
/// containers out of order), Slice 5 has no request-correlation token to
/// gate against (contract decision 4 — retail's <c>attemptOpenVendorID</c>
/// mode-2-vs-3 tab selection is deferred to Slice 6's sell-drag UI). Every
/// <c>ApproachVendor</c> is unconditionally authoritative (research doc
/// §A.3: "each ApproachVendor is a COMPLETE replace"), so <see cref="Apply"/>
/// is a single-phase call, not a request/apply pair.
/// </para>
///
/// <para>
/// <see cref="VendorTransition.Kind"/> distinguishes a brand-new vendor
/// (<see cref="VendorStateTransitionKind.Opened"/>) from a same-vendor
/// refresh (<see cref="VendorStateTransitionKind.Refreshed"/>, which will
/// only occur once Slice 6's buy/sell actions trigger a repeat
/// <c>ApproachVendor</c>) so a future UI layer (Slice 5.4) can decide
/// whether to reset its own sub-widgets — mirroring retail's
/// <c>gmVendorUI::OpenVendor</c>, which skips sub-UI teardown on a
/// same-vendor reopen (research doc §A.3/§B.1 point 1) but this class does
/// not itself perform any UI orchestration.
/// </para>
/// </summary>
public sealed class VendorState
{
    public uint VendorId { get; private set; }
    public VendorShopProfile Profile { get; private set; }
    public IReadOnlyList<VendorShopItem> Items { get; private set; } = Array.Empty<VendorShopItem>();

    public event Action<VendorTransition>? Changed;

    /// <summary>
    /// Apply a full ApproachVendor snapshot. Returns <c>false</c> (no-op,
    /// no event) for the sentinel guid 0 — matching
    /// <see cref="ExternalContainerState.RequestOpen"/>'s treatment of a
    /// zero id as "not a real target."
    /// </summary>
    public bool Apply(uint vendorGuid, VendorShopProfile profile, IReadOnlyList<VendorShopItem> items)
    {
        ArgumentNullException.ThrowIfNull(items);
        if (vendorGuid == 0u) return false;

        uint previous = VendorId;
        bool sameVendor = previous != 0u && previous == vendorGuid;

        VendorId = vendorGuid;
        Profile = profile;
        Items = items;

        var transition = new VendorTransition(
            sameVendor ? VendorStateTransitionKind.Refreshed : VendorStateTransitionKind.Opened,
            previous,
            vendorGuid);
        // Review finding F8 (Slice 5.4 review): match Close()'s per-listener
        // isolation + catch-and-log shape instead of a bare Invoke — Apply()
        // is called from the SAME per-frame inbound-message-dispatch boundary
        // (GameEventDispatcher.Dispatch's ApproachVendor handler) that
        // Close()'s doc comment already establishes must survive a broken
        // observer, and a bare Invoke lets the FIRST listener's exception
        // starve every listener registered after it (e.g. a plugin panel
        // wired after the retail VendorUiController).
        Action<VendorTransition>? listeners = Changed;
        if (listeners is not null)
        {
            foreach (Action<VendorTransition> listener in listeners.GetInvocationList())
            {
                try { listener(transition); }
                catch (Exception error)
                {
                    Console.Error.WriteLine(
                        $"[VendorState] Apply() observer threw: {error.Message}");
                }
            }
        }
        return true;
    }

    /// <summary>
    /// Clear the open shop (client-local close — distance watcher or a
    /// different-vendor open superseding this one; see research doc §A.3).
    /// Returns <c>false</c> if no vendor was open.
    /// </summary>
    /// <remarks>
    /// <b>Slice 5.3 review fix 3.</b> Unlike <see cref="Reset"/>, a failing
    /// <see cref="Changed"/> observer here is never rethrown. <c>Close()</c>'s
    /// production caller (<c>RuntimeVendorRangeQuery.EnforceRange</c>) runs
    /// inside the per-frame post-network-command-phase callback
    /// (<c>GameRuntime.CreateLocalPlayerFrameController</c>'s post-network
    /// phase) with no try/catch anywhere up the frame-loop chain — an
    /// <see cref="AggregateException"/> propagating out of here, <see cref="Reset"/>'s
    /// shape, would kill the frame. <see cref="Reset"/> keeps that
    /// collect-and-rethrow shape because ITS callers (session
    /// reset/portal-out/logout — a rare, explicit teardown boundary) already
    /// tolerate/handle it (e.g. <c>RuntimeInventoryState.Dispose</c>'s own
    /// <c>Try(...)</c> wrapper collects <see cref="Reset"/>'s failures
    /// alongside every other child's). This still fans out to every listener
    /// via <c>GetInvocationList()</c> (one broken observer must not starve
    /// another — same resilience as <see cref="Reset"/>), but LOGS each
    /// failure instead of collecting it into an exception, matching
    /// <c>GameEventDispatcher.Dispatch</c>'s own boundary contract
    /// (<c>src/AcDream.Core.Net/Messages/GameEventDispatcher.cs:95-117</c> —
    /// catch, <c>Console.Error.WriteLine</c>, never rethrow, "the decode
    /// thread must survive handler failures"): a per-frame boundary must
    /// survive its own observers' failures the same way. Not silent
    /// swallowing — the failure surfaces on <see cref="Console.Error"/>
    /// exactly the way the dispatcher's do.
    /// </remarks>
    public bool Close()
    {
        if (VendorId == 0u) return false;

        uint previous = VendorId;
        ClearFields();

        var transition = new VendorTransition(VendorStateTransitionKind.Closed, previous, 0u);
        Action<VendorTransition>? listeners = Changed;
        if (listeners is not null)
        {
            foreach (Action<VendorTransition> listener in listeners.GetInvocationList())
            {
                try { listener(transition); }
                catch (Exception error)
                {
                    Console.Error.WriteLine(
                        $"[VendorState] Close() observer threw: {error.Message}");
                }
            }
        }
        return true;
    }

    /// <summary>
    /// Session-lifecycle teardown (portal-out/reconnect/logout). Fans the
    /// transition out to every <see cref="Changed"/> listener even if one
    /// throws, matching <see cref="ExternalContainerState.Reset"/>'s
    /// AggregateException-collecting shape so one broken observer cannot
    /// prevent the others from converging.
    /// </summary>
    public bool Reset()
    {
        uint previous = VendorId;
        bool changed = previous != 0u;
        ClearFields();

        var transition = new VendorTransition(VendorStateTransitionKind.Reset, previous, 0u);
        Action<VendorTransition>? listeners = Changed;
        if (listeners is not null)
        {
            List<Exception>? failures = null;
            foreach (Action<VendorTransition> listener in listeners.GetInvocationList())
            {
                try { listener(transition); }
                catch (Exception error) { (failures ??= []).Add(error); }
            }
            if (failures is not null)
                throw new AggregateException(
                    "One or more vendor-state reset observers failed.",
                    failures);
        }
        return changed;
    }

    private void ClearFields()
    {
        VendorId = 0u;
        Profile = default;
        Items = Array.Empty<VendorShopItem>();
    }
}