using System;
using System.Collections.Generic;
using System.Numerics;
using AcDream.Core.Net.Messages;
using AcDream.Core.Quests;
using AcDream.Core.Ui;
using AcDream.Runtime.Gameplay;

namespace AcDream.App.UI.Layout;

/// <summary>
/// The Journal panel's Contracts page — retail <c>gmContractsUI</c>
/// (element type <c>0x1000004B</c>, page <c>0x100005D4</c>).
/// </summary>
/// <remarks>
/// <para>
/// A two-column list (Contract / Status) over a detail pane. Rows come from
/// <see cref="IRuntimeContractView"/> — live server state — joined to the
/// authored <see cref="ContractCatalog"/> for every word the player reads;
/// the wire itself carries only an id, a stage and two timers.
/// </para>
/// <para>
/// Rebuilds are revision-gated. The tracker changes rarely (accepting or
/// advancing a quest) while the panel ticks every frame, so polling
/// <see cref="RuntimeContractsSnapshot.Revision"/> is what keeps this from
/// rebuilding a template list continuously.
/// </para>
/// </remarks>
public sealed class JournalContractsPageController
{
    /// <summary>The layout the row template lives in — authored property
    /// <c>0x63</c> on the list's template entry.</summary>
    public const uint RowTemplateLayoutId = 0x21000069u;

    /// <summary>The row template element — authored <c>0x62</c>, and the id
    /// retail passes to <c>AddItemFromTemplateListByID @0x00499747</c>.</summary>
    public const uint RowTemplateElementId = 0x100005D7u;

    private const uint ListId = 0x100005CFu;
    private const uint RowNameId = 0x100005D1u;
    private const uint RowStatusId = 0x100005D2u;

    private const uint StatusValueId = 0x100005DFu;
    private const uint ContactValueId = 0x100005E0u;
    private const uint ContactLocationValueId = 0x100005E1u;
    private const uint QuestLocationValueId = 0x100005E2u;
    private const uint DescriptionId = 0x100005DEu;
    private const uint TimedValueId = 0x100005E3u;
    private const uint AbandonButtonId = 0x100005DCu;

    /// <summary>Live state and services the page reads.</summary>
    /// <param name="Contracts">The canonical tracker view.</param>
    /// <param name="Catalog">The authored contract text.</param>
    /// <param name="Now">
    /// The clock the repeat countdown is measured against. Injected rather
    /// than read from <see cref="DateTime.UtcNow"/> so the countdown is
    /// testable without waiting for it.
    /// </param>
    /// <param name="TemplateResolver">Builds one row from the authored template.</param>
    /// <param name="Abandon">
    /// Sends the abandon action for one contract. The row disappears only when
    /// the SERVER answers with its own delete, so a refused abandon leaves the
    /// quest exactly where it was.
    /// </param>
    public sealed record Bindings(
        IRuntimeContractView Contracts,
        Func<ContractCatalog> Catalog,
        Func<DateTime> Now,
        Func<uint, uint, UiElement?> TemplateResolver,
        Action<uint>? Abandon = null);

    private readonly Bindings _bindings;
    private readonly UiTemplateListBox? _list;
    private readonly UiText? _statusValue;
    private readonly UiText? _contactValue;
    private readonly UiText? _contactLocationValue;
    private readonly UiText? _questLocationValue;
    private readonly UiText? _description;
    private readonly UiText? _timedValue;

    /// <summary>
    /// Retail's own selection highlight for a listbox row. UiTemplateListBox
    /// has no generic selection mechanism (its class doc), so the page opts in
    /// directly — the same precedent
    /// <see cref="CharacterCreationSkillsPage"/> set.
    /// </summary>
    private static readonly Vector4 SelectedNameColor = Vector4.One;

    private readonly List<uint> _rowContractIds = [];
    private readonly List<(uint ContractId, UiText? Name, Vector4 Unselected)> _rows = [];

    private long _renderedRevision = -1;
    private uint _selectedContractId;

    public JournalContractsPageController(UiElement page, Bindings bindings)
    {
        ArgumentNullException.ThrowIfNull(page);
        _bindings = bindings ?? throw new ArgumentNullException(nameof(bindings));

        _list = UiElement.FindDescendant(page, ListId) as UiTemplateListBox;
        if (_list is not null)
            _list.TemplateResolver = bindings.TemplateResolver;

        _statusValue = UiElement.FindDescendant(page, StatusValueId) as UiText;
        _contactValue = UiElement.FindDescendant(page, ContactValueId) as UiText;
        _contactLocationValue =
            UiElement.FindDescendant(page, ContactLocationValueId) as UiText;
        _questLocationValue =
            UiElement.FindDescendant(page, QuestLocationValueId) as UiText;
        _description = UiElement.FindDescendant(page, DescriptionId) as UiText;
        _timedValue = UiElement.FindDescendant(page, TimedValueId) as UiText;

        if (UiElement.FindDescendant(page, AbandonButtonId) is UiButton abandon)
            abandon.OnClick = AbandonSelected;

        Refresh();
    }

    /// <summary>The contract the detail pane is showing, or 0.</summary>
    public uint SelectedContractId => _selectedContractId;

    /// <summary>Contract ids in list order, for tests.</summary>
    public IReadOnlyList<uint> RowContractIds => _rowContractIds;

    public void Tick()
    {
        // Cheap every frame; a rebuild only when the tracker actually moved.
        if (_bindings.Contracts.Snapshot.Revision != _renderedRevision)
            Refresh();
        else
            RefreshDetail();   // the repeat countdown ticks without a rebuild
    }

    public void Refresh()
    {
        RuntimeContractsSnapshot snapshot = _bindings.Contracts.Snapshot;
        _renderedRevision = snapshot.Revision;

        IReadOnlyList<ContractTracker> contracts = _bindings.Contracts.GetContracts();
        ContractCatalog catalog = _bindings.Catalog();
        DateTime now = _bindings.Now();

        // Retail's own default: the server nominates a display contract, and
        // otherwise the first row stands.
        if (snapshot.DisplayContractId != 0u)
            _selectedContractId = snapshot.DisplayContractId;
        if (_selectedContractId == 0u && contracts.Count != 0)
            _selectedContractId = contracts[0].ContractId;
        if (contracts.Count == 0)
            _selectedContractId = 0u;

        _rowContractIds.Clear();
        _rows.Clear();
        _list?.FlushPreservingScroll();

        foreach (ContractTracker tracker in contracts)
        {
            _rowContractIds.Add(tracker.ContractId);
            if (_list is null)
                continue;

            UiElement? row = _list.AddItemFromTemplateList(0);
            if (row is null)
                continue;

            ContractEntry entry = catalog.Lookup(tracker.ContractId);

            var name = UiElement.FindDescendant(row, RowNameId) as UiText;
            if (name is not null)
                SetText(name, entry.ContractName);
            if (UiElement.FindDescendant(row, RowStatusId) is UiText status)
            {
                SetText(status, ContractProgressText.Build(
                    (uint)tracker.Stage, tracker.TimeWhenRepeats,
                    tracker.ReceivedAt, entry, now));
            }

            // Captured AFTER SetText, which never touches DefaultColor (it is
            // read lazily inside the provider closure), so this is the row's
            // own authored colour to restore on deselect.
            _rows.Add((tracker.ContractId, name, name?.DefaultColor ?? Vector4.One));

            uint captured = tracker.ContractId;
            if (row is UiDatElement clickable)
            {
                // A generic Type-3 container is click-THROUGH by default, so
                // without this the handler below never fires and the list looks
                // dead. UiDatElement carries the opt-in seam for exactly this.
                clickable.ClickThrough = false;
                clickable.OnClick = () => Select(captured);
            }
        }

        ApplySelectionHighlight();
        RefreshDetail();
    }

    /// <summary>
    /// Abandons the selected contract — game action <c>0x0316</c>.
    /// </summary>
    /// <remarks>
    /// Nothing is removed locally. The server replies with a <c>0x0315</c>
    /// carrying <c>DeleteContract</c> and the tracker drops the row then, so a
    /// refusal leaves the quest visibly intact rather than vanishing it
    /// optimistically and having it reappear.
    /// </remarks>
    public void AbandonSelected()
    {
        if (_selectedContractId == 0u)
            return;

        _bindings.Abandon?.Invoke(_selectedContractId);
    }

    /// <summary>Points the detail pane at one contract.</summary>
    public void Select(uint contractId)
    {
        _selectedContractId = contractId;
        ApplySelectionHighlight();
        RefreshDetail();
    }

    /// <summary>
    /// Re-painted rather than merely remembered: a rebuild discards the old row
    /// objects, so a preserved selection has to be applied to the new ones.
    /// </summary>
    private void ApplySelectionHighlight()
    {
        foreach ((uint contractId, UiText? name, Vector4 unselected) in _rows)
        {
            if (name is not null)
            {
                name.DefaultColor =
                    contractId == _selectedContractId ? SelectedNameColor : unselected;
            }
        }
    }

    private void RefreshDetail()
    {
        ContractCatalog catalog = _bindings.Catalog();
        DateTime now = _bindings.Now();

        if (_selectedContractId == 0u
            || !_bindings.Contracts.TryGetContract(_selectedContractId, out ContractTracker tracker))
        {
            SetText(_statusValue, string.Empty);
            SetText(_contactValue, string.Empty);
            SetText(_contactLocationValue, string.Empty);
            SetText(_questLocationValue, string.Empty);
            SetText(_description, string.Empty);
            SetText(_timedValue, string.Empty);
            return;
        }

        ContractEntry entry = catalog.Lookup(_selectedContractId);

        SetText(_statusValue, ContractProgressText.Build(
            (uint)tracker.Stage, tracker.TimeWhenRepeats, tracker.ReceivedAt, entry, now));
        SetText(_contactValue, entry.NameNpcStart);
        SetText(_contactLocationValue, LocationText(entry.LocationNpcStartCell));
        SetText(_questLocationValue, LocationText(entry.LocationQuestAreaCell));
        SetText(_description, entry.Description);

        // "Timed:" is the other wire timer — the one FillProgressString never
        // reads. It belongs here, not in the Status column.
        SetText(_timedValue, tracker.TimeWhenDone > 0d
            ? RetailDurationText.Format(
                Math.Max(0d, tracker.TimeWhenDone - (now - tracker.ReceivedAt).TotalSeconds))
            : string.Empty);
    }

    /// <summary>
    /// Coordinates, or retail's literal <c>"Indoors"</c> when the cell has none
    /// (<c>LandDefs::gid_to_lcoord</c> failing, <c>@0x0049937F</c>).
    /// </summary>
    private static string LocationText(uint cellId)
    {
        if (cellId == 0u) return string.Empty;
        return RetailPositionFormatter.FormatOutdoorCell(cellId) ?? "Indoors";
    }

    private static void SetText(UiText? text, string value)
    {
        if (text is null) return;
        text.LinesProvider = () => [new UiText.Line(value, text.DefaultColor)];
    }
}