sql-utilities/src/Strata.SqlTools.Markdown/LinqToSql/QueryBreakdownGenerator.cs

using Strata.SqlTools.Breakdowns.LinqToSql;

namespace Strata.SqlTools.Markdown.LinqToSql;

/// <summary>
/// Generates Mermaid diagram markdown from LINQ to SQL QueryBreakdown objects.
/// Creates flowchart visualizations showing the LINQ query structure and flow.
/// </summary>
public class QueryBreakdownGenerator
{
    /// <summary>
    /// Generates a Mermaid flowchart diagram from a LINQ to SQL QueryBreakdown.
    /// </summary>
    /// <param name="queryBreakdown">The LINQ QueryBreakdown to visualize.</param>
    /// <param name="title">Optional title for the diagram.</param>
    /// <returns>A string containing the Mermaid markdown diagram.</returns>
    public static string GenerateMermaidDiagram(LinqQueryBreakdown queryBreakdown, string? title = null)
    {
        // Since LinqQueryBreakdown inherits from SqlServer.QueryBreakdown,
        // we can use the base generator which works with the shared properties
        return SqlServer.QueryBreakdownGenerator.GenerateMermaidDiagram(queryBreakdown, title);
    }

    /// <summary>
    /// Generates a Mermaid diagram showing the LINQ method call chain.
    /// </summary>
    /// <param name="queryBreakdown">The LINQ QueryBreakdown to visualize.</param>
    /// <param name="title">Optional title for the diagram.</param>
    /// <returns>A string containing the Mermaid flowchart showing method calls.</returns>
    public static string GenerateMethodChainDiagram(LinqQueryBreakdown queryBreakdown, string? title = null)
    {
        var sb = new System.Text.StringBuilder();

        if (!string.IsNullOrWhiteSpace(title))
        {
            sb.AppendLine($"### {title}");
            sb.AppendLine();
        }

        sb.AppendLine("```mermaid");
        sb.AppendLine("flowchart LR");
        sb.AppendLine();

        if (queryBreakdown.MethodCallChain.Count == 0)
        {
            sb.AppendLine("    Start([IQueryable]) --> End([Result])");
        }
        else
        {
            sb.AppendLine("    Start([IQueryable])");

            for (int i = 0; i < queryBreakdown.MethodCallChain.Count; i++)
            {
                var method = queryBreakdown.MethodCallChain[i];
                var nodeId = $"M{i}";
                var prevNodeId = i == 0 ? "Start" : $"M{i - 1}";

                sb.AppendLine($"    {nodeId}[\"{method}\"]");
                sb.AppendLine($"    {prevNodeId} --> {nodeId}");
            }

            var lastNodeId = $"M{queryBreakdown.MethodCallChain.Count - 1}";
            sb.AppendLine($"    {lastNodeId} --> End([Result])");
        }

        sb.AppendLine("```");
        sb.AppendLine();

        return sb.ToString();
    }

    /// <summary>
    /// Generates a combined diagram showing both the query structure and method chain.
    /// </summary>
    /// <param name="queryBreakdown">The LINQ QueryBreakdown to visualize.</param>
    /// <param name="title">Optional title for the diagram.</param>
    /// <returns>A string containing both diagrams.</returns>
    public static string GenerateCombinedDiagram(LinqQueryBreakdown queryBreakdown, string? title = null)
    {
        var sb = new System.Text.StringBuilder();

        if (!string.IsNullOrWhiteSpace(title))
        {
            sb.AppendLine($"## {title}");
            sb.AppendLine();
        }

        // Method chain
        sb.AppendLine("### LINQ Method Chain");
        sb.AppendLine();
        sb.Append(GenerateMethodChainDiagram(queryBreakdown));

        // SQL Structure
        sb.AppendLine("### SQL Query Structure");
        sb.AppendLine();
        sb.Append(GenerateMermaidDiagram(queryBreakdown));

        return sb.ToString();
    }
}