@page "/"
@implements IDisposable
@using System.Threading
@using System.Net.Http.Json
@inject HttpClient Http
@inject LocalizationService Loc

<PageTitle>@Loc["app.title"]</PageTitle>

<div class="container">
    <h1 class="mb-4">@Loc["app.title"]</h1>

    <!-- READ-ONLY SECTION (Top) -->
    <div class="card mb-4">
        <div class="card-header bg-light">
            <strong>@Loc["section.visualization"]</strong>
        </div>
        <div class="card-body">
            <div class="status-panel mb-3">
                <span class="badge bg-info text-dark me-2">@Loc["status.currentState"]: @Machine.CurrentState</span>
                <span class="badge bg-secondary me-2">@Loc["status.steps"]: @Steps</span>
                <span class="badge @(Machine.IsHalted ? "bg-danger" : "bg-success")">@Loc["status.status"]: @(Machine.IsHalted ? Loc["status.halted"] : Loc["status.ready"])</span>
            </div>

            <TapeVisualizer Tape="@Machine.Tape" HeadPosition="@Machine.HeadPosition" />

            <Controls
                OnStep="Step"
                OnRunToggle="ToggleRun"
                OnReset="Reset"
                IsRunning="@IsRunning"
                @bind-Speed="Speed" />

            <TransitionTableVisualizer
                Transitions="@Machine.Transitions"
                CurrentState="@Machine.CurrentState"
                CurrentReadSymbol="@Machine.Tape[Machine.HeadPosition]" />

            <div class="mt-2">
                <button class="btn btn-primary" @onclick="SetTape" disabled="@IsRunning">@Loc["button.loadConfig"]</button>
            </div>
        </div>
    </div>

    <!-- EDITABLE SECTION (Bottom) -->
    <div class="card">
        <div class="card-header bg-warning text-dark">
            <strong>@Loc["section.config"]</strong>
        </div>
        <div class="card-body">

            <!-- Examples -->
            <div class="mb-3">
                <label class="form-label fw-bold">@Loc["label.examples"]</label>
                <div @attributes="InertWhenRunning">
                    <select class="form-select @(IsRunning ? "input-disabled" : "")" value="@SelectedExampleIndex" @onchange="OnExampleChanged">
                        <option value="-1">@Loc["option.none"]</option>
                        @for (int i = 0; i < Examples.Count; i++)
                        {
                            <option value="@i">@(i + 1). @GetLocalizedText(Examples[i].Name)</option>
                        }
                    </select>
                </div>
            </div>

            <hr />

            <!-- Tape Configuration -->
            <div class="mb-4">
                <label class="form-label fw-bold">@Loc["label.tapeState"]</label>
                <div class="input-group">
                    <span class="input-group-text">@Loc["label.tapeValue"]</span>
                    <input type="text" class="form-control" @bind="TapeInput" placeholder="e.g. 1011" />
                    <span class="input-group-text">@Loc["label.headIndex"]</span>
                    <input type="number" class="form-control" @bind="HeadInput" style="max-width: 100px;" />
                    <button class="btn btn-primary" @onclick="SetTape" disabled="@IsRunning">@Loc["button.applyTape"]</button>
                </div>
                <small class="text-muted">@Loc["hint.tape"]</small>
            </div>

            <hr />

            <!-- Action Table Configuration -->
            <div class="mb-3">
                <label class="form-label fw-bold">@Loc["label.actionTable"]</label>
                <p class="text-muted small mb-1">@Loc["hint.format"] <code>@Loc["hint.csvFormat"]</code></p>
                <textarea class="form-control mb-2 font-monospace" rows="6" @bind="CsvRulesInput" placeholder="q0, 1, q0, 0, L"></textarea>

                @if (!string.IsNullOrEmpty(RuleParseError))
                {
                    <div class="alert alert-danger py-2">@RuleParseError</div>
                }
            </div>
        </div>
    </div>
</div>

@code {
    private Machine Machine { get; set; } = new();
    private bool IsRunning { get; set; }
    private int Speed { get; set; } = 500;
    private int Steps { get; set; }
    private CancellationTokenSource? _cts;

    // UI Bindings
    private string TapeInput { get; set; } = "";
    private int HeadInput { get; set; } = 0;

    // CSV Rules
    private string CsvRulesInput { get; set; } = "";
    private string RuleParseError { get; set; } = "";

    // Add inert attribute to block all interaction while running
    private Dictionary<string, object> InertWhenRunning =>
        IsRunning ? new Dictionary<string, object> { ["inert"] = "" } : new();

    // Example list loaded from server
    private List<ExampleConfig> Examples { get; set; } = new();
    private int SelectedExampleIndex { get; set; } = 0;

    protected override async Task OnInitializedAsync()
    {
        Loc.OnLanguageChanged += OnLanguageChanged;

        // Load example list from server
        try
        {
            var examples = await Http.GetFromJsonAsync<List<ExampleConfig>>("api/examples");
            if (examples != null && examples.Count > 0)
            {
                Examples = examples;
                // Apply the first example as default
                ApplyExample(Examples[0]);
            }
        }
        catch
        {
            // Start with empty state if example loading fails
        }
    }

    /// <summary>
    /// Called when an example is selected from the ComboBox.
    /// </summary>
    private void OnExampleChanged(ChangeEventArgs e)
    {
        if (IsRunning) return;
        if (int.TryParse(e.Value?.ToString(), out int index))
        {
            SelectedExampleIndex = index;
            if (index >= 0 && index < Examples.Count)
            {
                ApplyExample(Examples[index]);
            }
            else
            {
                // Clear all values when "None" is selected
                ClearConfiguration();
            }
        }
    }

    /// <summary>
    /// Resets all control values in the Configuration section.
    /// </summary>
    private void ClearConfiguration()
    {
        _cts?.Cancel();
        IsRunning = false;

        TapeInput = "";
        HeadInput = 0;
        CsvRulesInput = "";
        RuleParseError = "";

        Machine = new Machine();
        Steps = 0;
        StateHasChanged();
    }

    /// <summary>
    /// Applies an example configuration to the UI.
    /// </summary>
    private void ApplyExample(ExampleConfig example)
    {
        _cts?.Cancel();
        IsRunning = false;

        TapeInput = example.TapeInput;
        HeadInput = example.HeadPosition;
        CsvRulesInput = BuildCsvFromActions(example.Actions);

        LoadRules();
        SetTape();

        Steps = 0;
        StateHasChanged();
    }

    /// <summary>
    /// Returns the value matching the current language from a localized text list.
    /// </summary>
    private string GetLocalizedText(List<LocalizedText> texts)
    {
        return texts.FirstOrDefault(t => t.Language == Loc.CurrentLanguage)?.Value
            ?? texts.FirstOrDefault()?.Value
            ?? "";
    }

    /// <summary>
    /// Converts the Actions array to a CSV string with comments in the current language.
    /// </summary>
    private string BuildCsvFromActions(List<ActionEntry> actions)
    {
        var lines = new List<string>();
        foreach (var action in actions)
        {
            var comment = GetLocalizedText(action.Comment);
            lines.Add(string.IsNullOrEmpty(comment)
                ? action.Value
                : $"{action.Value}, {comment}");
        }
        return string.Join("\n", lines);
    }

    private void LoadRules()
    {
        RuleParseError = "";
        var newTransitions = new List<(string, char, string, char, MoveDirection, string)>();
        var seenKeys = new Dictionary<(string, char), int>();
        var lines = CsvRulesInput.Split('\n', StringSplitOptions.RemoveEmptyEntries);
        int lineNum = 0;

        foreach (var line in lines)
        {
            lineNum++;
            if (string.IsNullOrWhiteSpace(line)) continue;

            var parts = line.Split(',', 6);
            if (parts.Length < 5 || parts.Length > 6)
            {
                RuleParseError = Loc["error.columnCount", lineNum, parts.Length];
                return;
            }

            var state = parts[0].Trim();
            var readStr = parts[1].Trim();
            var newState = parts[2].Trim();
            var writeStr = parts[3].Trim();
            var moveStr = parts[4].Trim();

            if (readStr.Length != 1)
            {
                RuleParseError = Loc["error.readSymbol", lineNum, readStr];
                return;
            }
            if (writeStr.Length != 1)
            {
                RuleParseError = Loc["error.writeSymbol", lineNum, writeStr];
                return;
            }

            MoveDirection move;
            if (moveStr.Equals("L", StringComparison.OrdinalIgnoreCase) || moveStr.Equals("Left", StringComparison.OrdinalIgnoreCase))
                move = MoveDirection.Left;
            else if (moveStr.Equals("R", StringComparison.OrdinalIgnoreCase) || moveStr.Equals("Right", StringComparison.OrdinalIgnoreCase))
                move = MoveDirection.Right;
            else if (moveStr.Equals("S", StringComparison.OrdinalIgnoreCase) || moveStr.Equals("Stay", StringComparison.OrdinalIgnoreCase))
                move = MoveDirection.Stay;
            else
            {
                RuleParseError = Loc["error.moveDirection", lineNum, moveStr];
                return;
            }

            // 6th column is an optional comment
            string comment = parts.Length > 5 ? parts[5].Trim() : "";

            var key = (state, readStr[0]);
            if (seenKeys.TryGetValue(key, out int prevLine))
            {
                RuleParseError = Loc["error.duplicateKey", lineNum, state, readStr, prevLine];
                return;
            }
            seenKeys[key] = lineNum;

            newTransitions.Add((state, readStr[0], newState, writeStr[0], move, comment));
        }

        if (newTransitions.Count == 0)
        {
            RuleParseError = Loc["error.noRules"];
            return;
        }

        // Assume initial state is the first state mentioned in the rules
        string initialState = newTransitions.First().Item1;

        Machine.LoadProgram(initialState, newTransitions);
        StateHasChanged();
    }

    private void SetTape()
    {
        _cts?.Cancel();
        IsRunning = false;

        // Also apply CSV rules
        LoadRules();

        Machine.Reset();

        // Apply initial tape values
        if (!string.IsNullOrEmpty(TapeInput))
        {
            for (int i = 0; i < TapeInput.Length; i++)
            {
                Machine.Tape[i] = TapeInput[i];
            }
        }

        Machine.ForceHeadPosition(HeadInput);
        Steps = 0;
        StateHasChanged();
    }

    private void Step()
    {
        if (Machine.IsHalted) return;

        Machine.Step();
        Steps++;
        StateHasChanged();
    }

    private async Task ToggleRun(bool shouldRun)
    {
        IsRunning = shouldRun;
        if (IsRunning)
        {
            _cts = new CancellationTokenSource();
            try
            {
                await RunLoop(_cts.Token);
            }
            catch (OperationCanceledException)
            {
                // Stopped
            }
            finally
            {
                IsRunning = false;
                _cts = null;
                StateHasChanged();
            }
        }
        else
        {
            _cts?.Cancel();
        }
    }

    private async Task RunLoop(CancellationToken token)
    {
        while (!token.IsCancellationRequested && !Machine.IsHalted)
        {
            Step();
            await Task.Delay(Speed, token);
        }
    }

    private void Reset()
    {
        // Re-apply the current inputs to simulate a "Reset to Initial"
        SetTape();
    }

    private void OnLanguageChanged()
    {
        // Rebuild comments in the new language if an example is selected
        if (SelectedExampleIndex >= 0 && SelectedExampleIndex < Examples.Count)
        {
            CsvRulesInput = BuildCsvFromActions(Examples[SelectedExampleIndex].Actions);
        }
        InvokeAsync(StateHasChanged);
    }

    public void Dispose()
    {
        Loc.OnLanguageChanged -= OnLanguageChanged;
    }
}