using Blog.Models;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Rendering;

namespace Blog.Components.Pages.Git;

/// <summary>
/// One line of code, as the spans git.css can tell apart.
/// </summary>
/// <remarks>
/// A render tree rather than markup because the cell this lands in is <c>white-space: pre</c>: any
/// newline or indentation a .razor file left between two tokens would be rendered as part of the
/// file. A render tree emits exactly the nodes it is handed, and <c>AddContent</c> escapes them.
/// </remarks>
public sealed class GitCode : ComponentBase
{
    [Parameter]
    public IReadOnlyList<SyntaxToken> Tokens { get; set; } = [];

    /// <summary>
    /// A diff's <c>+</c> or <c>-</c>, repeated out of the gutter into the line so the diff still
    /// reads as one when it is copied or read without colour. git.css marks it unselectable, so
    /// copying gives back the code rather than the patch.
    /// </summary>
    [Parameter]
    public char? Sign { get; set; }

    protected override void BuildRenderTree(RenderTreeBuilder builder)
    {
        // Sequence numbers exist for diffing one render against the next, which these pages never
        // do - they are rendered once, statically, and thrown away.
        var sequence = 0;

        if (Sign is { } sign)
        {
            builder.OpenElement(sequence++, "span");
            builder.AddAttribute(sequence++, "class", "sign");
            builder.AddContent(sequence++, sign);
            builder.CloseElement();
        }

        foreach (var token in Tokens)
        {
            if (token.Kind is SyntaxKind.Text)
            {
                builder.AddContent(sequence++, token.Text);
                continue;
            }

            builder.OpenElement(sequence++, "span");
            builder.AddAttribute(sequence++, "class", Class(token.Kind));
            builder.AddContent(sequence++, token.Text);
            builder.CloseElement();
        }
    }

    private static string Class(SyntaxKind kind) => kind switch
    {
        SyntaxKind.Comment => "tok-comment",
        SyntaxKind.String => "tok-string",
        SyntaxKind.Number => "tok-number",
        SyntaxKind.Keyword => "tok-keyword",
        SyntaxKind.Meta => "tok-meta",
        _ => ""
    };
}