using System;
using System.Globalization;
using AcDream.Core.Journal;
using AcDream.Core.Ui;
using AcDream.Runtime.Gameplay;

namespace AcDream.App.UI.Layout;

/// <summary>
/// The Journal panel's notes page — retail <c>gmJournalUI</c> (element type
/// <c>0x10000048</c>, page <c>0x10000563</c>).
/// </summary>
/// <remarks>
/// <para>
/// A per-character notebook: label, title, free notes, a recorded location and
/// a countdown timer, paged with First/Previous/Next/Last.
/// </para>
/// <para>
/// <b>Every navigation commits the current page first.</b> Retail's
/// <c>ListenToElementMessage @0x004968D0</c> calls <c>SaveThisPage</c> on the
/// way out of every one of the five navigation buttons, which is why paging
/// away never loses what you just typed. Skipping that is the obvious
/// simplification and it silently eats edits.
/// </para>
/// </remarks>
public sealed class JournalNotesPageController
{
    // Retail switches on (idElement - 0x10000565), so these two carry no
    // caption of their own: they are the prev/next arrows.
    private const uint PreviousButtonId = 0x10000565u;
    private const uint NextButtonId = 0x10000566u;
    private const uint NewButtonId = 0x10000567u;

    private const uint LabelFieldId = 0x10000569u;
    private const uint TitleFieldId = 0x1000056Bu;
    private const uint NotesFieldId = 0x1000056Du;

    private const uint FirstButtonId = 0x1000056Fu;
    private const uint PageNumberId = 0x10000570u;
    private const uint LastButtonId = 0x10000571u;

    private const uint LocationTextId = 0x10000573u;
    private const uint RecordButtonId = 0x10000574u;

    private const uint TimerDaysFieldId = 0x10000576u;
    private const uint TimerHoursFieldId = 0x10000578u;
    private const uint TimerMinutesFieldId = 0x1000057Au;

    // The "d" / "h" / "m" unit labels. Retail's ShowEditableTimer @0x00495770
    // toggles each box AND its label — m_pDaysStaticText, m_pHoursStaticText,
    // m_pMinutesStaticText — so the running readout, which is authored over
    // the same strip, does not draw through them.
    private const uint TimerDaysLabelId = 0x10000577u;
    private const uint TimerHoursLabelId = 0x10000579u;
    private const uint TimerMinutesLabelId = 0x1000057Bu;
    private const uint RunningTimerTextId = 0x1000057Cu;
    private const uint StartButtonId = 0x1000057Du;

    /// <param name="Journal">The canonical owner.</param>
    /// <param name="Commands">Mutations, kept off the read view.</param>
    /// <param name="PlayerCell">
    /// The player's current landcell, for the "Record" button. Returns 0 when
    /// there is no valid cell — indoors, or not in the world.
    /// </param>
    /// <param name="Now">The clock the countdown runs against.</param>
    public sealed record Bindings(
        IRuntimeJournalView Journal,
        RuntimeJournalState Commands,
        Func<uint> PlayerCell,
        Func<DateTime> Now);

    private readonly Bindings _bindings;
    private readonly UiField? _label;
    private readonly UiField? _title;
    private readonly UiField? _notes;
    private readonly UiField? _timerDays;
    private readonly UiField? _timerHours;
    private readonly UiField? _timerMinutes;
    private readonly UiText? _pageNumber;

    /// <summary>
    /// The location readout is authored EDITABLE (<c>0x16</c>), so it builds as
    /// a <see cref="UiField"/> — not the <see cref="UiText"/> its placeholder
    /// text suggests. Resolving it as text yielded null and threw every write
    /// away silently: Record reached the model and the file, and never the
    /// screen.
    /// </summary>
    private readonly UiField? _location;
    private readonly UiText? _runningTimer;
    private readonly UiElement? _timerDaysLabel;
    private readonly UiElement? _timerHoursLabel;
    private readonly UiElement? _timerMinutesLabel;
    private readonly UiButton? _start;

    private long _renderedRevision = -1;

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

        _label = UiElement.FindDescendant(page, LabelFieldId) as UiField;
        _title = UiElement.FindDescendant(page, TitleFieldId) as UiField;
        _notes = UiElement.FindDescendant(page, NotesFieldId) as UiField;
        _timerDays = UiElement.FindDescendant(page, TimerDaysFieldId) as UiField;
        _timerHours = UiElement.FindDescendant(page, TimerHoursFieldId) as UiField;
        _timerMinutes = UiElement.FindDescendant(page, TimerMinutesFieldId) as UiField;
        _pageNumber = UiElement.FindDescendant(page, PageNumberId) as UiText;
        _location = UiElement.FindDescendant(page, LocationTextId) as UiField;
        _runningTimer = UiElement.FindDescendant(page, RunningTimerTextId) as UiText;
        _timerDaysLabel = UiElement.FindDescendant(page, TimerDaysLabelId);
        _timerHoursLabel = UiElement.FindDescendant(page, TimerHoursLabelId);
        _timerMinutesLabel = UiElement.FindDescendant(page, TimerMinutesLabelId);
        _start = UiElement.FindDescendant(page, StartButtonId) as UiButton;

        // The three timer boxes take digits only. Their authored 0x1E is 2, so
        // the width is already handled; this stops a letter reaching an int
        // parse that would silently read as zero.
        foreach (UiField? field in new[] { _timerDays, _timerHours, _timerMinutes })
        {
            if (field is not null)
                field.CharacterFilter = static c => char.IsAsciiDigit(c);
        }

        // Committing on focus loss is what makes clicking straight from a text
        // box to another tab keep the edit.
        foreach (UiField? field in new[] { _label, _title, _notes })
        {
            if (field is not null)
                field.OnFocusLost = _ => CommitText();
        }

        // Retail's ListenToElementMessage @0x004968D0 ends every one of these
        // in Update() — the panel redraws at the moment of the click, not on
        // the next frame. Deferring to Tick would work in the client and makes
        // the behaviour untestable and a frame late.
        Bind(page, NewButtonId, () =>
        {
            CommitText();
            _bindings.Commands.NewPage();
            Refresh();
        });
        Bind(page, FirstButtonId, () => Navigate(1));
        Bind(page, LastButtonId, () => Navigate(_bindings.Journal.Snapshot.PageCount));
        Bind(page, PreviousButtonId,
            () => Navigate(_bindings.Journal.Snapshot.CurrentPage - 1));
        Bind(page, NextButtonId,
            () => Navigate(_bindings.Journal.Snapshot.CurrentPage + 1));
        Bind(page, RecordButtonId, RecordLocation);
        Bind(page, StartButtonId, ToggleTimer);

        Refresh();
    }

    /// <summary>
    /// Commits the edit boxes into the current page — retail's
    /// <c>SaveThisPage @0x00495360</c>.
    /// </summary>
    public void CommitText()
    {
        if (_bindings.Journal.Snapshot.CurrentPage == 0)
            return;

        _bindings.Commands.UpdateCurrent(
            _label?.Text ?? string.Empty,
            _title?.Text ?? string.Empty,
            _notes?.Text ?? string.Empty);

        _bindings.Commands.SetTimer(
            ParseField(_timerDays),
            ParseField(_timerHours),
            ParseField(_timerMinutes));
    }

    public void Tick()
    {
        if (_bindings.Journal.Snapshot.Revision != _renderedRevision)
            Refresh();
        else
            RefreshTimer();     // the countdown ticks without a page rebuild
    }

    /// <summary>Called when the page is hidden — retail saves here.</summary>
    public void OnHidden() => CommitText();

    public void Refresh()
    {
        RuntimeJournalSnapshot snapshot = _bindings.Journal.Snapshot;
        _renderedRevision = snapshot.Revision;

        JournalPage page = _bindings.Journal.Current;

        _label?.SetText(page.Label);
        _title?.SetText(page.Title);
        _notes?.SetText(page.Notes);
        _timerDays?.SetText(Field(page.TimerDays));
        _timerHours?.SetText(Field(page.TimerHours));
        _timerMinutes?.SetText(Field(page.TimerMinutes));

        // Retail's own "~ N ~". An empty journal shows no number rather than
        // "~ 0 ~", which would name a page that does not exist.
        SetText(_pageNumber, snapshot.CurrentPage == 0
            ? string.Empty
            : $"~ {snapshot.CurrentPage.ToString(CultureInfo.InvariantCulture)} ~");

        _location?.SetText(page.HasLocation
            ? FormatLocation(page.LocationX, page.LocationY)
            : string.Empty);

        RefreshTimer();
    }

    /// <summary>
    /// The editable-fields / running-readout swap
    /// (<c>ShowEditableTimer @0x00495770</c> versus <c>ShowRunningTimer</c>).
    /// </summary>
    /// <remarks>
    /// The readout is authored at the SAME x as the three number boxes, so
    /// showing both at once overlaps them illegibly — the strip is one or the
    /// other.
    /// </remarks>
    private void RefreshTimer()
    {
        double remaining = _bindings.Journal.RemainingTimerSeconds(_bindings.Now());
        bool running = remaining > 0d;

        // Each box AND its unit label, exactly the six elements retail toggles.
        // Hiding only the boxes leaves "d h m" drawn underneath the readout,
        // which is authored across the same strip.
        if (_timerDays is not null) _timerDays.Visible = !running;
        if (_timerHours is not null) _timerHours.Visible = !running;
        if (_timerMinutes is not null) _timerMinutes.Visible = !running;
        if (_timerDaysLabel is not null) _timerDaysLabel.Visible = !running;
        if (_timerHoursLabel is not null) _timerHoursLabel.Visible = !running;
        if (_timerMinutesLabel is not null) _timerMinutesLabel.Visible = !running;
        if (_runningTimer is not null) _runningTimer.Visible = running;

        SetText(_runningTimer, running
            ? RetailDurationText.Format(remaining)
            : string.Empty);

        if (_start is not null)
            _start.Label = running ? "Stop" : "Start";
    }

    private void Navigate(int pageNumber)
    {
        CommitText();
        _bindings.Commands.GotoPage(pageNumber);
        Refresh();
    }

    private void RecordLocation()
    {
        uint cell = _bindings.PlayerCell();
        if (cell == 0u)
            return;

        // Indoors, retail's own gid_to_lcoord fails and nothing is recorded —
        // UpdateLocation @0x004958F0 only ever formats coordinates already
        // stored, so there is no "you are indoors" message to port. Silence
        // here is faithful, not an omission.
        if (!AcDream.Core.Ui.RadarCoordinates.TryFromCell(cell, out var coordinates))
            return;

        _bindings.Commands.RecordLocation((float)coordinates.X, (float)coordinates.Y);
        Refresh();
    }

    private void ToggleTimer()
    {
        if (_bindings.Journal.RemainingTimerSeconds(_bindings.Now()) > 0d)
        {
            _bindings.Commands.ResetTimer();
            Refresh();
            return;
        }

        CommitText();       // the fields the countdown reads
        _bindings.Commands.StartTimer(_bindings.Now());
        Refresh();
    }

    /// <summary>
    /// The journal's own authored placeholder is <c>"00.0S, 00.0W"</c> — with
    /// a space after the comma, unlike the radar's own combined form.
    /// </summary>
    private static string FormatLocation(float x, float y)
    {
        var coordinates = new AcDream.Core.Ui.RadarCoordinates(x, y);
        return $"{coordinates.YText}, {coordinates.XText}";
    }

    private void Bind(UiElement page, uint elementId, Action action)
    {
        if (UiElement.FindDescendant(page, elementId) is UiButton button)
            button.OnClick = action;
    }

    private static int ParseField(UiField? field) =>
        int.TryParse(
            field?.Text,
            NumberStyles.Integer,
            CultureInfo.InvariantCulture,
            out int value) && value >= 0
            ? value
            : 0;

    private static string Field(int value) =>
        value == 0 ? string.Empty : value.ToString(CultureInfo.InvariantCulture);

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