// Copyright 2026 GitCover Commons gUG (haftungsbeschränkt)
// Author: Axel Druschel
// SPDX-License-Identifier: Apache-2.0

using System.Text;
using System.Text.RegularExpressions;
using Markdig;
using Markdig.Extensions.Tables;
using Markdig.Syntax;
using Markdig.Syntax.Inlines;

namespace GitCover.WebStaticBuilder;

/// <summary>
/// Renders a Markdig AST to ANSI-styled console output. No external
/// dependency beyond Markdig (already referenced). Supports headings,
/// paragraphs, lists, code blocks, blockquotes, tables, thematic breaks,
/// and inline formatting (bold, italic, code, links).
/// </summary>
public static class MarkdownConsoleRenderer
{
    // ANSI SGR codes
    private const string Reset = "\x1b[0m";
    private const string Bold = "\x1b[1m";
    private const string Dim = "\x1b[2m";
    private const string Italic = "\x1b[3m";
    private const string Underline = "\x1b[4m";
    private const string FgCyan = "\x1b[36m";
    private const string FgBrightCyan = "\x1b[96m";
    private const string FgBrightYellow = "\x1b[93m";
    private const string FgBrightRed = "\x1b[91m";
    private const string FgBrightGreen = "\x1b[92m";
    private const string FgBrightBlack = "\x1b[90m";

    /// <summary>Render a Markdown document to the console.</summary>
    public static void Render(string markdown, TextWriter writer)
    {
        var pipeline = new MarkdownPipelineBuilder()
            .UseAdvancedExtensions()
            .Build();
        var doc = Markdig.Markdown.Parse(markdown, pipeline);
        RenderBlocks(doc, writer, 0);
    }

    private static void RenderBlocks(ContainerBlock container, TextWriter w, int indent)
    {
        foreach (var block in container)
            RenderBlock(block, w, indent);
    }

    private static void RenderBlock(Block block, TextWriter w, int indent)
    {
        var pad = new string(' ', indent * 2);
        switch (block)
        {
            case HeadingBlock h:
                RenderHeading(h, w);
                break;
            case ParagraphBlock p:
                w.WriteLine(pad + RenderInlines(p.Inline!));
                w.WriteLine();
                break;
            case ListBlock lb:
                RenderList(lb, w, indent);
                break;
            case QuoteBlock qb:
                RenderQuote(qb, w, indent);
                break;
            case FencedCodeBlock fc:
                RenderCodeBlock(fc.Lines.ToString(), w, indent, fc.Info);
                break;
            case CodeBlock cb:
                RenderCodeBlock(cb.Lines.ToString(), w, indent, null);
                break;
            case ThematicBreakBlock:
                w.WriteLine(pad + $"{Dim}{'─'.ToString().PadLeft(Console.BufferWidth > 0 ? Math.Min(Console.BufferWidth, 60) : 60, '─')}{Reset}");
                w.WriteLine();
                break;
            case Table table:
                RenderTable(table, w, indent);
                break;
            default:
                // Fallback: try to extract text content
                if (block is ContainerBlock cb2)
                    RenderBlocks(cb2, w, indent);
                break;
        }
    }

    private static void RenderHeading(HeadingBlock h, TextWriter w)
    {
        var text = RenderInlines(h.Inline!);
        var prefix = h.Level switch
        {
            1 => $"{Bold}{FgBrightYellow}",
            2 => $"{Bold}{FgBrightCyan}",
            3 => $"{Bold}{FgBrightGreen}",
            _ => $"{Bold}",
        };
        w.WriteLine($"{prefix}{text}{Reset}");
        w.WriteLine();
    }

    private static void RenderList(ListBlock lb, TextWriter w, int indent)
    {
        var pad = new string(' ', indent * 2);
        int idx = 1;
        foreach (ListItemBlock item in lb)
        {
            var marker = lb.IsOrdered ? $"{idx}{lb.OrderedDelimiter} " : "• ";
            var firstBlock = item.FirstOrDefault();
            if (firstBlock is ParagraphBlock p)
            {
                w.WriteLine($"{pad}{marker}{RenderInlines(p.Inline!)}");
            }
            else if (firstBlock != null)
            {
                w.WriteLine($"{pad}{marker}");
                RenderBlock(firstBlock, w, indent + 1);
            }

            // Sub-blocks beyond the first paragraph (e.g., nested lists)
            for (int i = 1; i < item.Count; i++)
            {
                if (item[i] is ListBlock subList)
                    RenderList(subList, w, indent + 1);
                else
                    RenderBlock(item[i], w, indent + 1);
            }

            if (lb.IsOrdered) idx++;
        }
        w.WriteLine();
    }

    private static void RenderQuote(QuoteBlock qb, TextWriter w, int indent)
    {
        var pad = new string(' ', indent * 2);
        var savedColor = Console.ForegroundColor;
        Console.ForegroundColor = ConsoleColor.DarkGray;
        foreach (var sub in qb)
        {
            if (sub is ParagraphBlock p)
                w.WriteLine($"{pad}{Dim}│ {RenderInlines(p.Inline!)}{Reset}");
            else
                RenderBlock(sub, w, indent + 1);
        }
        Console.ForegroundColor = savedColor;
        w.WriteLine();
    }

    private static void RenderCodeBlock(string code, TextWriter w, int indent, string? lang)
    {
        var pad = new string(' ', indent * 2);
        var lines = code.TrimEnd('\n', '\r').Split('\n');
        w.WriteLine($"{pad}{Dim}```{lang ?? ""}{Reset}");
        foreach (var line in lines)
            w.WriteLine($"{pad}{FgBrightCyan}{line}{Reset}");
        w.WriteLine($"{pad}{Dim}```{Reset}");
        w.WriteLine();
    }

    private static void RenderTable(Table table, TextWriter w, int indent)
    {
        var pad = new string(' ', indent * 2);
        // First pass: collect cell texts and compute column widths
        var rows = new List<List<string>>();
        foreach (TableRow row in table)
        {
            var cells = new List<string>();
            foreach (TableCell cell in row)
            {
                var cellText = new StringBuilder();
                foreach (var sub in cell)
                {
                    if (sub is ParagraphBlock p)
                        cellText.Append(RenderInlines(p.Inline!));
                }
                cells.Add(cellText.ToString().Trim());
            }
            rows.Add(cells);
        }

        if (rows.Count == 0) return;
        var colCount = rows.Max(r => r.Count);
        var widths = new int[colCount];
        foreach (var row in rows)
            for (int c = 0; c < row.Count; c++)
                widths[c] = Math.Max(widths[c], row[c].Length);

        // Render rows
        bool isFirstRow = true;
        foreach (var row in rows)
        {
            var parts = new List<string>();
            for (int c = 0; c < row.Count; c++)
            {
                var cellText = c < row.Count ? row[c] : "";
                var padded = cellText.PadRight(widths[c]);
                parts.Add(isFirstRow ? $"{Bold}{padded}{Reset}" : padded);
            }
            w.WriteLine($"{pad}│ {string.Join(" │ ", parts)} │");

            if (isFirstRow)
            {
                // Separator
                var sep = string.Join("─┬─", widths.Select(wd => new string('─', wd + 2)));
                w.WriteLine($"{pad}├{sep}┤");
                isFirstRow = false;
            }
        }
        w.WriteLine();
    }

    /// <summary>Render inline elements to a single ANSI-styled string.</summary>
    private static string RenderInlines(ContainerInline inlines)
    {
        var sb = new StringBuilder();
        foreach (var il in inlines)
            RenderInline(il, sb);
        return sb.ToString();
    }

    private static void RenderInline(Inline inline, StringBuilder sb)
    {
        switch (inline)
        {
            case LiteralInline lit:
                sb.Append(lit.Content.ToString());
                break;
            case EmphasisInline emp:
                var code = emp.DelimiterCount == 2 ? Bold : Italic;
                sb.Append(code);
                foreach (var child in emp)
                    RenderInline(child, sb);
                sb.Append(Reset);
                if (emp.DelimiterCount == 2) sb.Append(""); // bold doesn't need reset of italic
                break;
            case CodeInline ci:
                sb.Append($"{FgBrightRed}{ci.Content}{Reset}");
                break;
            case LinkInline link:
                var text = new StringBuilder();
                foreach (var child in link)
                    RenderInline(child, text);
                if (link.IsImage)
                    sb.Append($"{Dim}[image: {text}{Reset}{Dim}]{Reset}");
                else if (link.Url != null)
                    sb.Append($"{Underline}{FgCyan}{text}{Reset} {Dim}({link.Url}){Reset}");
                else
                    sb.Append(text.ToString());
                break;
            case LineBreakInline:
                sb.AppendLine();
                break;
            case HtmlInline html:
                sb.Append($"{Dim}{html.Tag}{Reset}");
                break;
            case ContainerInline container:
                foreach (var child in container)
                    RenderInline(child, sb);
                break;
            default:
                // DelimiterInline, etc. — extract literal content
                sb.Append(inline.ToString());
                break;
        }
    }
}