using System.Text;

namespace SQLLinter.Infrastructure.Diagram;

public static class MermaidRenderer
{
    public static string ToMermaidContent(BpmnDiagram diagram)
    {
        var sb = new StringBuilder();
        sb.AppendLine("flowchart TB");

        // main: print Start, then tasks/gateways, then End
        var mainStart = diagram.Main.Nodes.Where(n => n.Type == BpmnNodeType.Start).ToList();
        var mainTasks = diagram.Main.Nodes.Where(n => n.Type == BpmnNodeType.Task || n.Type == BpmnNodeType.Gateway).ToList();
        var mainEnd = diagram.Main.Nodes.Where(n => n.Type == BpmnNodeType.End).ToList();

        foreach (var node in mainStart)
        {
            var nid = SanitizeId(node.Id);
            var label = Escape(node.Label);
            sb.AppendLine($"  {nid}((\"{label}\"))");
        }
        foreach (var node in mainTasks)
        {
            var nid = SanitizeId(node.Id);
            var label = Escape(node.Label);
            if (node.Type == BpmnNodeType.Gateway)
                sb.AppendLine($"  {nid}{{\"{label}\"}}");
            else
                sb.AppendLine($"  {nid}[\"{label}\"]");
        }
        foreach (var node in mainEnd)
        {
            var nid = SanitizeId(node.Id);
            var label = Escape(node.Label);
            sb.AppendLine($"  {nid}((\"{label}\"))");
        }

        sb.AppendLine();

        // subprocesses as subgraphs: pool label, start, tasks/gateways, end
        foreach (var proc in diagram.Subprocesses)
        {
            var procId = SanitizeId(proc.Id);
            sb.AppendLine($"  subgraph {procId} [\"{Escape(proc.Name)}\"]");

            var startNodes = proc.Nodes.Where(n => n.Type == BpmnNodeType.Start).ToList();
            var taskNodes = proc.Nodes.Where(n => n.Type == BpmnNodeType.Task || n.Type == BpmnNodeType.Gateway).ToList();
            var endNodes = proc.Nodes.Where(n => n.Type == BpmnNodeType.End).ToList();
            var poolNodes = proc.Nodes.Where(n => n.Type == BpmnNodeType.Subprocess).ToList();

            // pool label nodes (usually first)
            foreach (var node in poolNodes)
            {
                var nid = SanitizeId(node.Id);
                var label = Escape(node.Label);
                sb.AppendLine($"    {nid}[\"{label}\"]");
            }

            foreach (var node in startNodes)
            {
                var nid = SanitizeId(node.Id);
                var label = Escape(node.Label);
                sb.AppendLine($"    {nid}((\"{label}\"))");
            }
            foreach (var node in taskNodes)
            {
                var nid = SanitizeId(node.Id);
                var label = Escape(node.Label);
                if (node.Type == BpmnNodeType.Gateway)
                    sb.AppendLine($"    {nid}{{\"{label}\"}}");
                else
                    sb.AppendLine($"    {nid}[\"{label}\"]");
            }
            foreach (var node in endNodes)
            {
                var nid = SanitizeId(node.Id);
                var label = Escape(node.Label);
                sb.AppendLine($"    {nid}((\"{label}\"))");
            }

            // edges inside subprocess
            foreach (var e in proc.Edges)
            {
                var from = SanitizeId(e.From);
                var to = SanitizeId(e.To);
                var arrow = e.Dashed ? "-.->" : "-->";
                var lbl = string.IsNullOrWhiteSpace(e.Label) ? string.Empty : $" |{Escape(e.Label)}|";
                sb.AppendLine($"    {from} {arrow} {to}{lbl}");
            }

            sb.AppendLine("  end");
            sb.AppendLine();
        }

        // main edges
        foreach (var e in diagram.Main.Edges)
        {
            var from = SanitizeId(e.From);
            var to = SanitizeId(e.To);
            var arrow = e.Dashed ? "-.->" : "-->";
            var lbl = string.IsNullOrWhiteSpace(e.Label) ? string.Empty : $" |{Escape(e.Label)}|";
            sb.AppendLine($"  {from} {arrow} {to}{lbl}");
        }

        return sb.ToString();
    }

    public static string RenderMarkdown(BpmnDiagram diagram)
    {
        var content = ToMermaidContent(diagram);
        var sb = new StringBuilder();
        sb.AppendLine("```mermaid");
        sb.Append(content);
        sb.AppendLine("```");
        return sb.ToString();
    }

    public static string RenderHtml(BpmnDiagram diagram)
    {
        var content = ToMermaidContent(diagram);
        var sb = new StringBuilder();

        // Put raw mermaid text inside .mermaid container so mermaid.js can render it
        sb.AppendLine("<div class=\"mermaid\">\n" + content + "\n</div>");

        return sb.ToString();
    }

    private static string Escape(string s)
    {
        if (s == null) return string.Empty;
        return s.Replace("\"", "\\\"").Replace("\n", " ").Replace("\r", " ");
    }

    private static string SanitizeId(string s)
    {
        if (string.IsNullOrEmpty(s)) return "id";
        var sb = new StringBuilder();
        foreach (var ch in s)
        {
            if (char.IsLetterOrDigit(ch)) sb.Append(ch);
            else sb.Append('_');
        }
        return sb.ToString();
    }
}