using System.Text;
using Strata.SqlTools.Breakdowns.SqlServer;
using Strata.SqlTools.SqlBreakdown.Interfaces;

namespace Strata.SqlTools.Markdown.SqlServer;

/// <summary>
/// Generates Mermaid diagram markdown from SQL QueryBreakdown objects.
/// Creates flowchart visualizations showing the query structure and flow.
/// </summary>
public class QueryBreakdownGenerator
{
    /// <summary>
    /// Generates a Mermaid flowchart diagram from a QueryBreakdown.
    /// </summary>
    /// <param name="queryBreakdown">The 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(QueryBreakdown queryBreakdown, string? title = null)
    {
        var sb = new StringBuilder();

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

        // Start Mermaid flowchart
        sb.AppendLine("```mermaid");
        sb.AppendLine("flowchart TD");
        sb.AppendLine();

        int nodeId = 1;

        // Start node
        sb.AppendLine($"    Start([Query Start]) --> Node{nodeId}");
        sb.AppendLine();

        // WITH clause (CTE)
        if (queryBreakdown.IsUsingWithClause)
        {
            sb.AppendLine($"    Node{nodeId}[\"WITH Clause<br/>Common Table Expressions\"]");
            foreach (var withClause in queryBreakdown.WithClauses)
            {
                sb.AppendLine($"    Node{nodeId} --> CTE{nodeId}[\"{EscapeMermaidText(withClause.TableName)}\"]");
                nodeId++;
            }
            sb.AppendLine($"    Node{nodeId - 1} --> Node{nodeId}");
            sb.AppendLine();
            nodeId++;
        }

        // SELECT clause
        if (!string.IsNullOrEmpty(queryBreakdown.SelectClause.Clause))
        {
            var selectText = TruncateText(queryBreakdown.SelectClause.Clause, 50);
            sb.AppendLine($"    Node{nodeId}[\"SELECT<br/>{EscapeMermaidText(selectText)}\"]");
            sb.AppendLine($"    Node{nodeId - 1} --> Node{nodeId}");
            sb.AppendLine();
            nodeId++;
        }

        // FROM clause
        if (queryBreakdown.IsUsingFromClause && !string.IsNullOrWhiteSpace(queryBreakdown.FromClause?.Clause))
        {
            var fromText = TruncateText(queryBreakdown.FromClause.Clause, 50);
            sb.AppendLine($"    Node{nodeId}[\"FROM<br/>{EscapeMermaidText(fromText)}\"]");
            sb.AppendLine($"    Node{nodeId - 1} --> Node{nodeId}");
            sb.AppendLine();
            nodeId++;
        }

        // WHERE clause
        if (queryBreakdown.IsUsingWhereClause && !string.IsNullOrWhiteSpace(queryBreakdown.WhereClause?.Clause))
        {
            var whereText = TruncateText(queryBreakdown.WhereClause.Clause, 50);
            sb.AppendLine($"    Node{nodeId}{{\"WHERE<br/>{EscapeMermaidText(whereText)}\"}}");
            sb.AppendLine($"    Node{nodeId - 1} --> Node{nodeId}");
            sb.AppendLine();
            nodeId++;
        }

        // GROUP BY clause
        if (queryBreakdown.IsUsingGroupByClause && !string.IsNullOrWhiteSpace(queryBreakdown.GroupByClause?.Clause))
        {
            var groupByText = TruncateText(queryBreakdown.GroupByClause.Clause, 50);
            sb.AppendLine($"    Node{nodeId}[\"GROUP BY<br/>{EscapeMermaidText(groupByText)}\"]");
            sb.AppendLine($"    Node{nodeId - 1} --> Node{nodeId}");
            sb.AppendLine();
            nodeId++;
        }

        // HAVING clause
        if (queryBreakdown.IsUsingHavingClause && !string.IsNullOrWhiteSpace(queryBreakdown.HavingClause?.Clause))
        {
            var havingText = TruncateText(queryBreakdown.HavingClause.Clause, 50);
            sb.AppendLine($"    Node{nodeId}{{\"HAVING<br/>{EscapeMermaidText(havingText)}\"}}");
            sb.AppendLine($"    Node{nodeId - 1} --> Node{nodeId}");
            sb.AppendLine();
            nodeId++;
        }

        // ORDER BY clause
        if (queryBreakdown.IsUsingOrderByClause && !string.IsNullOrWhiteSpace(queryBreakdown.OrderByClause?.Clause))
        {
            var orderByText = TruncateText(queryBreakdown.OrderByClause.Clause, 50);
            sb.AppendLine($"    Node{nodeId}[\"ORDER BY<br/>{EscapeMermaidText(orderByText)}\"]");
            sb.AppendLine($"    Node{nodeId - 1} --> Node{nodeId}");
            sb.AppendLine();
            nodeId++;
        }

        // End node
        sb.AppendLine($"    Node{nodeId - 1} --> End([Query End])");

        // End Mermaid diagram
        sb.AppendLine("```");

        return sb.ToString();
    }

    /// <summary>
    /// Generates a Mermaid flowchart diagram from any SQL breakdown implementing ISqlBreakdown.
    /// </summary>
    /// <param name="sqlBreakdown">The SQL breakdown 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(ISqlBreakdown sqlBreakdown, string? title = null)
    {
        // If it's a QueryBreakdown, use the specialized method
        if (sqlBreakdown is QueryBreakdown qb)
        {
            return GenerateMermaidDiagram(qb, title);
        }

        // For other SQL breakdowns, generate a simple diagram
        var sb = new StringBuilder();

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

        sb.AppendLine("```mermaid");
        sb.AppendLine("flowchart TD");
        sb.AppendLine();
        sb.AppendLine("    Start([SQL Statement Start])");

        if (sqlBreakdown.IsUsingSetupClause)
        {
            sb.AppendLine("    Start --> Setup[\"Setup Clauses\"]");
            sb.AppendLine("    Setup --> Main[\"Main Statement\"]");
        }
        else
        {
            sb.AppendLine("    Start --> Main[\"Main Statement\"]");
        }

        if (sqlBreakdown.IsUsingFinishClause)
        {
            sb.AppendLine("    Main --> Finish[\"Finish Clauses\"]");
            sb.AppendLine("    Finish --> End([SQL Statement End])");
        }
        else
        {
            sb.AppendLine("    Main --> End([SQL Statement End])");
        }

        sb.AppendLine("```");

        return sb.ToString();
    }

    /// <summary>
    /// Escapes text for Mermaid diagram labels to prevent syntax errors.
    /// </summary>
    private static string EscapeMermaidText(string text)
    {
        return text
            .Replace("\"", "&quot;")
            .Replace("[", "&#91;")
            .Replace("]", "&#93;")
            .Replace("{", "&#123;")
            .Replace("}", "&#125;")
            .Replace("(", "&#40;")
            .Replace(")", "&#41;")
            .Replace("<", "&lt;")
            .Replace(">", "&gt;");
    }

    /// <summary>
    /// Truncates text to a maximum length and adds ellipsis if needed.
    /// </summary>
    private static string TruncateText(string text, int maxLength)
    {
        if (string.IsNullOrWhiteSpace(text) || text.Length <= maxLength)
        {
            return text;
        }

        return string.Concat(text.AsSpan(0, maxLength), "...");
    }
}