using System.Drawing;
using System.Windows.Forms;
using EnvelopeRenderer.Desktop.Core.Launch;
using EnvelopeRenderer.Desktop.Views;

namespace EnvelopeRenderer.Desktop;

/// <summary>
/// Operator-facing shell: pick a template, CSV, and output PDF path, then launch a render and
/// watch it through to completion. Sprint 1, Batch 4 ("Launch a text-only render from the
/// desktop app") proved the process could be launched without freezing the UI; Batch 5 ("Show
/// render progress and completion summary") adds reading the CLI's `PROGRESS` stream while it
/// runs, showing a non-technical completion summary once it exits, and — since the button is now
/// only re-enabled after the process actually exits rather than as soon as it starts — closes the
/// double-launch gap previously logged in logs/technical_debt_log.md.
///
/// All non-UI logic (input validation, argument construction, CLI discovery, process launch,
/// progress parsing, and summary formatting) lives in EnvelopeRenderer.Desktop.Core.Launch and is
/// unit tested there — this class is intentionally thin event-handler wiring over that logic.
/// </summary>
public sealed class MainForm : Form
{
    private readonly TextBox _templatePathTextBox = new();
    private readonly TextBox _csvPathTextBox = new();
    private readonly TextBox _outputPathTextBox = new();
    private readonly Button _renderButton = new() { Text = "&Render", AutoSize = true };
    private readonly Button _designTemplateButton = new() { Text = "&Design Template...", AutoSize = true };
    private readonly Label _statusLabel = new()
    {
        AutoSize = false,
        Height = 48,
        TextAlign = ContentAlignment.TopLeft,
    };

    private readonly CliProcessLauncher _launcher;

    public MainForm() : this(new CliProcessLauncher())
    {
    }

    /// <summary>Internal constructor allowing a launcher to be injected (used by tests/composition).</summary>
    internal MainForm(CliProcessLauncher launcher)
    {
        _launcher = launcher;

        Text = "Envelope Renderer";
        MinimumSize = new Size(640, 260);
        StartPosition = FormStartPosition.CenterScreen;

        Controls.Add(BuildLayout());
    }

    private Control BuildLayout()
    {
        var layout = new TableLayoutPanel
        {
            Dock = DockStyle.Fill,
            ColumnCount = 3,
            RowCount = 5,
            Padding = new Padding(12),
            AutoSize = true,
        };
        layout.ColumnStyles.Add(new ColumnStyle(SizeType.AutoSize));
        layout.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 100));
        layout.ColumnStyles.Add(new ColumnStyle(SizeType.AutoSize));

        AddPickerRow(
            layout,
            row: 0,
            labelText: "Template (XML):",
            textBox: _templatePathTextBox,
            browse: () => BrowseForOpenFile(_templatePathTextBox, "XML template files (*.xml)|*.xml|All files (*.*)|*.*"));

        AddPickerRow(
            layout,
            row: 1,
            labelText: "CSV data:",
            textBox: _csvPathTextBox,
            browse: () => BrowseForOpenFile(_csvPathTextBox, "CSV files (*.csv)|*.csv|All files (*.*)|*.*"));

        AddPickerRow(
            layout,
            row: 2,
            labelText: "Output PDF:",
            textBox: _outputPathTextBox,
            browse: () => BrowseForSaveFile(_outputPathTextBox, "PDF files (*.pdf)|*.pdf|All files (*.*)|*.*"));

        _renderButton.Click += OnRenderClick;
        _designTemplateButton.Click += (_, _) => OnDesignTemplateClick();
        var buttonPanel = new FlowLayoutPanel { Dock = DockStyle.Fill, FlowDirection = FlowDirection.RightToLeft, AutoSize = true };
        buttonPanel.Controls.Add(_renderButton);
        buttonPanel.Controls.Add(_designTemplateButton);
        layout.Controls.Add(buttonPanel, 1, 3);
        layout.SetColumnSpan(buttonPanel, 2);

        _statusLabel.Dock = DockStyle.Fill;
        layout.Controls.Add(_statusLabel, 0, 4);
        layout.SetColumnSpan(_statusLabel, 3);

        return layout;
    }

    private static void AddPickerRow(TableLayoutPanel layout, int row, string labelText, TextBox textBox, Action browse)
    {
        var label = new Label
        {
            Text = labelText,
            AutoSize = true,
            Anchor = AnchorStyles.Left,
            Margin = new Padding(3, 9, 3, 3),
        };

        textBox.Dock = DockStyle.Fill;
        textBox.Margin = new Padding(3, 6, 3, 3);

        var browseButton = new Button { Text = "Browse...", AutoSize = true, Margin = new Padding(3, 3, 3, 3) };
        browseButton.Click += (_, _) => browse();

        layout.Controls.Add(label, 0, row);
        layout.Controls.Add(textBox, 1, row);
        layout.Controls.Add(browseButton, 2, row);
    }

    private static void BrowseForOpenFile(TextBox target, string filter)
    {
        using var dialog = new OpenFileDialog { Filter = filter, CheckFileExists = true, Title = "Select a file" };
        if (dialog.ShowDialog() == DialogResult.OK)
        {
            target.Text = dialog.FileName;
        }
    }

    private static void BrowseForSaveFile(TextBox target, string filter)
    {
        using var dialog = new SaveFileDialog { Filter = filter, OverwritePrompt = false, Title = "Choose where to save the PDF" };
        if (dialog.ShowDialog() == DialogResult.OK)
        {
            target.Text = dialog.FileName;
        }
    }

    private async void OnRenderClick(object? sender, EventArgs e)
    {
        var inputs = new RenderLaunchInputs(_templatePathTextBox.Text, _csvPathTextBox.Text, _outputPathTextBox.Text);

        var validation = RenderLaunchValidator.Validate(inputs);
        if (!validation.IsValid)
        {
            SetStatus(string.Join(" ", validation.Errors), isError: true);
            return;
        }

        var cliPath = CliExecutablePathResolver.Resolve(AppContext.BaseDirectory);
        if (!cliPath.IsFound)
        {
            SetStatus(cliPath.Error!, isError: true);
            ShowLaunchFailure(cliPath.Error!);
            return;
        }

        // Disabled here and only re-enabled once RunAsync's awaited Task completes below (i.e.
        // once the child process has actually exited) — not the moment it starts — so an
        // operator can't launch a second render against the same output while one is in flight.
        _renderButton.Enabled = false;
        SetStatus("Starting render...", isError: false);

        try
        {
            var arguments = CliArgumentListBuilder.Build(inputs);

            // Constructed on the UI thread so Progress<T> captures this thread's
            // SynchronizationContext and marshals each Report() call back to it automatically —
            // OnRenderProgress can update controls directly without a manual Invoke.
            var progress = new Progress<ProgressEvent>(OnRenderProgress);

            var result = await _launcher.RunAsync(cliPath.Path!, arguments, progress);

            var summary = RenderCompletionSummaryFormatter.Format(result);
            if (result.Succeeded)
            {
                SetStatus(summary, isError: false);
            }
            else if (!result.Started)
            {
                // A launch failure (the process never started) keeps the message-box treatment
                // from Batch 4 — it means something is wrong with the desktop app's own setup,
                // not with the operator's data, and deserves an explicit acknowledgement.
                SetStatus(summary, isError: true);
                ShowLaunchFailure(summary);
            }
            else
            {
                SetStatus(summary, isError: true);
            }
        }
        finally
        {
            _renderButton.Enabled = true;
        }
    }

    private void OnDesignTemplateClick()
    {
        using var designer = new TemplateDesignerForm();
        designer.ShowDialog(this);
    }

    private void OnRenderProgress(ProgressEvent progressEvent)
    {
        SetStatus(RenderProgressStatusFormatter.Format(progressEvent), isError: progressEvent.Kind == ProgressEventKind.Failure);
    }

    private void ShowLaunchFailure(string message)
    {
        MessageBox.Show(this, message, "Could not start render", MessageBoxButtons.OK, MessageBoxIcon.Error);
    }

    private void SetStatus(string message, bool isError)
    {
        _statusLabel.Text = message;
        _statusLabel.ForeColor = isError ? Color.Firebrick : Color.DarkGreen;
    }
}