using System.Text;
using Strata.SqlTools.SqlBreakdown.Classes;
using Strata.SqlTools.SqlBreakdown.Expressions;
using Strata.SqlTools.SqlBreakdown.Expressions.Arithmetic;
using Strata.SqlTools.SqlBreakdown.Expressions.Conditional;
using Strata.SqlTools.SqlBreakdown.Expressions.Conditional.Comparisons;
using Strata.SqlTools.SqlBreakdown.Expressions.Conditional.Logical;
using Strata.SqlTools.SqlBreakdown.Expressions.Functions;
using Strata.SqlTools.SqlBreakdown.Expressions.Functions.Aggregate;
using Strata.SqlTools.SqlBreakdown.Expressions.Functions.Conditional;
using Strata.SqlTools.SqlBreakdown.Expressions.Literals;
using Strata.SqlTools.SqlBreakdown.Interfaces.Core;

namespace Strata.SqlTools.Markdown.Expressions;

/// <summary>
/// Generates markdown documentation for Expression trees.
/// Creates human-readable documentation with expression structure, type information, and visual representations.
/// </summary>
public class ExpressionGenerator : IVisitor<string>
{
    private int _indentLevel = 0;
    private readonly string _indentString = "  ";

    /// <summary>
    /// Generates markdown documentation from an Expression tree.
    /// </summary>
    /// <param name="expression">The expression to document.</param>
    /// <param name="title">Optional title for the documentation.</param>
    /// <returns>A markdown formatted string documenting the expression.</returns>
    public string GenerateMarkdown(Expression expression, string? title = null)
    {
        var sb = new StringBuilder();

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

        sb.AppendLine("## Expression Structure");
        sb.AppendLine();
        sb.AppendLine("```");
        _indentLevel = 0;
        sb.AppendLine(expression.Accept(this));
        sb.AppendLine("```");
        sb.AppendLine();

        sb.AppendLine("## Expression Type");
        sb.AppendLine();
        sb.AppendLine($"**Type:** `{expression.GetType().Name}`");
        sb.AppendLine();

        sb.AppendLine("## Mermaid Diagram");
        sb.AppendLine();
        sb.AppendLine(GenerateMermaidDiagram(expression));

        sb.AppendLine();
        sb.AppendLine("## Mathematical Expression");
        sb.AppendLine();
        sb.AppendLine(GenerateMathematicalExpression(expression));

        return sb.ToString();
    }

    /// <summary>
    /// Generates a mathematical expression using LaTeX notation for GitHub markdown.
    /// </summary>
    /// <param name="expression">The expression to convert to mathematical notation.</param>
    /// <param name="inline">If true, generates inline math ($...$), otherwise block math ($$...$$).</param>
    /// <returns>A string containing the LaTeX mathematical expression.</returns>
    public static string GenerateMathematicalExpression(Expression expression, bool inline = false)
    {
        var latex = ConvertToLatex(expression);
        return inline ? $"${latex}$" : $"$$\n{latex}\n$$";
    }

    /// <summary>
    /// Generates a mathematical expression from raw LaTeX in markdown format.
    /// </summary>
    /// <param name="latex">The LaTeX expression.</param>
    /// <param name="format">The format to use: "dollar" for $/$$ delimiters, "math" for ```math code fence.</param>
    /// <param name="inline">If true and format is "dollar", generates inline math ($...$), otherwise block math ($$...$$). Ignored for "math" format.</param>
    /// <returns>A string containing the formatted mathematical expression.</returns>
    public static string GenerateRawMathematicalExpression(string latex, string format = "dollar", bool inline = false)
    {
        return format.ToLower() switch
        {
            "math" => $"```math\n{latex}\n```",
            _ => inline ? $"${latex}$" : $"$$\n{latex}\n$$"
        };
    }

    private static string ConvertToLatex(Expression expression)
    {
        return expression switch
        {
            // Arithmetic expressions
            ArithmeticExpression arith => ConvertArithmeticToLatex(arith),

            // Comparison expressions
            ComparisonOperatorExpression comp => ConvertComparisonToLatex(comp),

            // Logical expressions
            AndExpression and => $"({ConvertToLatex(and.ExpressionA)} \\land {ConvertToLatex(and.ExpressionB)})",
            OrExpression or => $"({ConvertToLatex(or.ExpressionA)} \\lor {ConvertToLatex(or.ExpressionB)})",
            NotExpression not => $"\\neg({ConvertToLatex(not.ExpressionA)})",

            // Literals
            NumberLiteralExpression num => num.Value.ToString() ?? "0",
            StringLiteralExpression str => $"\\text{{\"{EscapeLatex(str.Value)}\"}}",
            BooleanLiteralExpression b => b.Value ? "\\text{true}" : "\\text{false}",
            NullLiteralExpression => "\\text{NULL}",

            // Column expressions
            ColumnExpression col => $"\\text{{{EscapeLatex(col.ColumnName)}}}",

            // Parameter expressions
            ParameterExpression param => $"@{EscapeLatex(param.ParameterName)}",

            // Case expressions (before FunctionExpression since it's a subclass)
            CaseExpression caseExpr => ConvertCaseToLatex(caseExpr),

            // Functions
            FunctionExpression func => ConvertFunctionToLatex(func),

            // Between expressions
            BetweenExpression between => $"{ConvertToLatex(between.Expression)} \\in [{ConvertToLatex(between.LowerBound)}, {ConvertToLatex(between.UpperBound)}]",

            // IN expressions
            InExpression inExpr => $"{ConvertToLatex(inExpr.SearchExpression)} \\in \\{{{string.Join(", ", inExpr.ValuesToCompare.Select(ConvertToLatex))}\\}}",

            // LIKE expressions
            LikeExpression like => $"{ConvertToLatex(like.Subject)} \\approx \\text{{\"{EscapeLatex(ConvertExpressionToString(like.Pattern))}\"}}",
            _ => $"\\text{{{EscapeLatex(expression.GetType().Name)}}}"
        };
    }

    private static string ConvertArithmeticToLatex(ArithmeticExpression arith)
    {
        var left = ConvertToLatex(arith.ExpressionA);
        var right = ConvertToLatex(arith.ExpressionB);

        var op = arith.ArithmeticOperator switch
        {
            "+" => "+",
            "-" => "-",
            "*" => "\\times",
            "/" => "\\div",
            "%" => "\\bmod",
            _ => "?"
        };

        return $"({left} {op} {right})";
    }

    private static string ConvertComparisonToLatex(ComparisonOperatorExpression comp)
    {
        var left = ConvertToLatex(comp.ExpressionA);
        var right = ConvertToLatex(comp.ExpressionB);

        var op = comp.Operator switch
        {
            "=" => "=",
            "<>" => "\\neq",
            "!=" => "\\neq",
            ">" => ">",
            ">=" => "\\geq",
            "<" => "<",
            "<=" => "\\leq",
            _ => "?"
        };

        return $"({left} {op} {right})";
    }

    private static string ConvertFunctionToLatex(FunctionExpression func)
    {
        var args = string.Join(", ", func.Arguments.Select(ConvertToLatex));
        var funcName = EscapeLatex(func.FunctionName);

        return func.FunctionName.ToUpper() switch
        {
            // Aggregate functions
            "COUNT" => $"\\text{{COUNT}}({args})",
            "SUM" => $"\\sum({args})",
            "AVG" => $"\\text{{AVG}}({args})",
            "MIN" => $"\\min({args})",
            "MAX" => $"\\max({args})",

            // Math functions
            "ABS" => $"|{args}|",
            "SQRT" => $"\\sqrt{{{args}}}",
            "POWER" when func.Arguments.Length >= 2 =>
                $"{ConvertToLatex(func.Arguments[0])}^{{{ConvertToLatex(func.Arguments[1])}}}",
            "LOG" => $"\\log({args})",
            "EXP" => $"e^{{{args}}}",

            // Default
            _ => $"\\text{{{funcName}}}({args})"
        };
    }

    private static string ConvertCaseToLatex(CaseExpression caseExpr)
    {
        var sb = new StringBuilder();
        sb.Append("\\begin{cases}\n");

        foreach (var (condition, result) in caseExpr.ConditionResultPairs)
        {
            sb.Append($"  {ConvertToLatex(result)} & \\text{{if }} {ConvertToLatex(condition)} \\\\\n");
        }

        if (caseExpr.ElseResultExpression is not null)
        {
            sb.Append($"  {ConvertToLatex(caseExpr.ElseResultExpression)} & \\text{{otherwise}}\n");
        }

        sb.Append("\\end{cases}");
        return sb.ToString();
    }

    private static string ConvertExpressionToString(Expression expression)
    {
        return expression switch
        {
            StringLiteralExpression str => str.Value,
            _ => expression.ToString() ?? ""
        };
    }

    private static string EscapeLatex(string text)
    {
        return text
            .Replace("\\", "\\\\")
            .Replace("{", "\\{")
            .Replace("}", "\\}")
            .Replace("_", "\\_")
            .Replace("$", "\\$")
            .Replace("%", "\\%")
            .Replace("&", "\\&")
            .Replace("#", "\\#");
    }

    /// <summary>
    /// Generates a Mermaid tree diagram from an Expression tree.
    /// </summary>
    private static string GenerateMermaidDiagram(Expression expression)
    {
        var sb = new StringBuilder();
        sb.AppendLine("```mermaid");
        sb.AppendLine("graph TD");
        sb.AppendLine();

        int nodeCounter = 0;
        var nodeMap = new Dictionary<object, int>();
        GenerateMermaidNodes(expression, sb, nodeMap, ref nodeCounter);

        sb.AppendLine("```");
        return sb.ToString();
    }

    private static int GenerateMermaidNodes(Expression expression, StringBuilder sb, Dictionary<object, int> nodeMap, ref int nodeCounter)
    {
        var currentNode = nodeCounter++;
        nodeMap[expression] = currentNode;

        var nodeLabel = GetNodeLabel(expression);
        var nodeShape = GetNodeShape(expression);

        sb.AppendLine($"    Node{currentNode}{nodeShape[0]}\"{EscapeMarkdown(nodeLabel)}\"{nodeShape[1]}");

        // Process child expressions
        switch (expression)
        {
            case ComparisonOperatorExpression comp:
                var leftId = GenerateMermaidNodes(comp.ExpressionA, sb, nodeMap, ref nodeCounter);
                var rightId = GenerateMermaidNodes(comp.ExpressionB, sb, nodeMap, ref nodeCounter);
                sb.AppendLine($"    Node{currentNode} --> Node{leftId}");
                sb.AppendLine($"    Node{currentNode} --> Node{rightId}");
                break;

            case AndExpression and:
                var andLeftId = GenerateMermaidNodes(and.ExpressionA, sb, nodeMap, ref nodeCounter);
                var andRightId = GenerateMermaidNodes(and.ExpressionB, sb, nodeMap, ref nodeCounter);
                sb.AppendLine($"    Node{currentNode} -->|Left| Node{andLeftId}");
                sb.AppendLine($"    Node{currentNode} -->|Right| Node{andRightId}");
                break;

            case OrExpression or:
                var orLeftId = GenerateMermaidNodes(or.ExpressionA, sb, nodeMap, ref nodeCounter);
                var orRightId = GenerateMermaidNodes(or.ExpressionB, sb, nodeMap, ref nodeCounter);
                sb.AppendLine($"    Node{currentNode} -->|Left| Node{orLeftId}");
                sb.AppendLine($"    Node{currentNode} -->|Right| Node{orRightId}");
                break;

            case NotExpression not:
                var notId = GenerateMermaidNodes(not.ExpressionA, sb, nodeMap, ref nodeCounter);
                sb.AppendLine($"    Node{currentNode} --> Node{notId}");
                break;

            case ArithmeticExpression arith:
                var arithmLeftId = GenerateMermaidNodes(arith.ExpressionA, sb, nodeMap, ref nodeCounter);
                var arithmRightId = GenerateMermaidNodes(arith.ExpressionB, sb, nodeMap, ref nodeCounter);
                sb.AppendLine($"    Node{currentNode} --> Node{arithmLeftId}");
                sb.AppendLine($"    Node{currentNode} --> Node{arithmRightId}");
                break;

            case FunctionExpression func:
                foreach (var arg in func.Arguments)
                {
                    var argId = GenerateMermaidNodes(arg, sb, nodeMap, ref nodeCounter);
                    sb.AppendLine($"    Node{currentNode} --> Node{argId}");
                }
                break;
        }

        return currentNode;
    }

    private static string GetNodeLabel(Expression expression)
    {
        return expression switch
        {
            NumberLiteralExpression num => $"Number: {num.Value}",
            StringLiteralExpression str => $"String: {TruncateText(str.Value, 20)}",
            DateTimeLiteralExpression dt => $"DateTime: {dt.Value:yyyy-MM-dd}",
            BooleanLiteralExpression b => $"Boolean: {b.Value}",
            NullLiteralExpression => "NULL",
            ComparisonOperatorExpression comp => $"Comparison: {comp.Operator}",
            AndExpression => "AND",
            OrExpression => "OR",
            NotExpression => "NOT",
            ArithmeticExpression arith => $"Arithmetic: {arith.ArithmeticOperator}",
            FunctionExpression func => $"Function: {func.FunctionName}",
            ParameterExpression param => $"Parameter: @{param.ParameterName}",
            _ => expression.GetType().Name
        };
    }

    private static string[] GetNodeShape(Expression expression)
    {
        return expression switch
        {
            NumberLiteralExpression or StringLiteralExpression or DateTimeLiteralExpression or BooleanLiteralExpression or NullLiteralExpression => new[] { "[", "]" },
            ComparisonOperatorExpression => new[] { "{", "}" },
            AndExpression or OrExpression or NotExpression => new[] { "{", "}" },
            FunctionExpression => new[] { "[[", "]]" },
            _ => new[] { "(", ")" }
        };
    }

    private string Indent() => new string(' ', _indentLevel * _indentString.Length);

    private static string EscapeMarkdown(string text)
    {
        return text
            .Replace("\"", "&quot;")
            .Replace("[", "&#91;")
            .Replace("]", "&#93;");
    }

    private static string TruncateText(string text, int maxLength)
    {
        if (string.IsNullOrWhiteSpace(text) || text.Length <= maxLength)
        {
            return text;
        }
        return string.Concat(text.AsSpan(0, maxLength), "...");
    }

    #region IVisitor Implementation

    public string VisitTableSource(TableSource tableSource)
    {
        return $"{Indent()}TableSource: {tableSource.TableName}";
    }

    public string VisitColumnExpression<TSource>(ColumnExpression<TSource> column) where TSource : SelectSource
    {
        return $"{Indent()}Column: {column.ColumnName}";
    }

    public string VisitSelectClauseColumn(SelectClauseColumn selectClauseColumn)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}SelectClauseColumn:");
        _indentLevel++;
        sb.AppendLine(selectClauseColumn.Expression.Accept(this));
        if (!string.IsNullOrWhiteSpace(selectClauseColumn.Alias))
        {
            sb.AppendLine($"{Indent()}Alias: {selectClauseColumn.Alias}");
        }
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitParameterExpression(ParameterExpression parameterExpression)
    {
        return $"{Indent()}Parameter: @{parameterExpression.ParameterName}";
    }

    public string VisitNumberLiteralExpression(NumberLiteralExpression numberLiteral)
    {
        return $"{Indent()}Number: {numberLiteral.Value}";
    }

    public string VisitStringLiteralExpression(StringLiteralExpression stringLiteral)
    {
        return $"{Indent()}String: '{stringLiteral.Value}'";
    }

    public string VisitDateTimeLiteralExpression(DateTimeLiteralExpression dateTimeLiteral)
    {
        return $"{Indent()}DateTime: {dateTimeLiteral.Value:yyyy-MM-dd HH:mm:ss}";
    }

    public string VisitNullLiteralExpression(NullLiteralExpression nullLiteral)
    {
        return $"{Indent()}NULL";
    }

    public string VisitBooleanLiteralExpression(BooleanLiteralExpression booleanLiteral)
    {
        return $"{Indent()}Boolean: {booleanLiteral.Value}";
    }

    public string VisitParameterLiteralExpression(ParameterLiteralExpression parameterLiteral)
    {
        return $"{Indent()}Parameter: {parameterLiteral.Value}";
    }

    public string VisitSymbolLiteralExpression(SymbolLiteralExpression symbolLiteral)
    {
        return $"{Indent()}Symbol: {symbolLiteral.Value}";
    }

    public string VisitComparisonExpression(ComparisonOperatorExpression comparison)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}Comparison ({comparison.Operator}):");
        _indentLevel++;
        sb.AppendLine($"{Indent()}Left:");
        _indentLevel++;
        sb.AppendLine(comparison.ExpressionA.Accept(this));
        _indentLevel--;
        sb.AppendLine($"{Indent()}Right:");
        _indentLevel++;
        sb.AppendLine(comparison.ExpressionB.Accept(this));
        _indentLevel--;
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitAndExpression(AndExpression logical)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}AND:");
        _indentLevel++;
        sb.AppendLine(logical.ExpressionA.Accept(this));
        sb.AppendLine(logical.ExpressionB.Accept(this));
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitOrExpression(OrExpression logical)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}OR:");
        _indentLevel++;
        sb.AppendLine(logical.ExpressionA.Accept(this));
        sb.AppendLine(logical.ExpressionB.Accept(this));
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitNotExpression(NotExpression logical)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}NOT:");
        _indentLevel++;
        sb.AppendLine(logical.ExpressionA.Accept(this));
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitInExpression(InExpression inExpression)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}IN:");
        _indentLevel++;
        sb.AppendLine($"{Indent()}Search Expression:");
        _indentLevel++;
        sb.AppendLine(inExpression.SearchExpression.Accept(this));
        _indentLevel--;
        sb.AppendLine($"{Indent()}Values:");
        _indentLevel++;
        foreach (var value in inExpression.ValuesToCompare)
        {
            sb.AppendLine(value.Accept(this));
        }
        _indentLevel--;
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitNotInExpression(NotInExpression inExpression)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}NOT IN:");
        _indentLevel++;
        sb.AppendLine($"{Indent()}Search Expression:");
        _indentLevel++;
        sb.AppendLine(inExpression.SearchExpression.Accept(this));
        _indentLevel--;
        sb.AppendLine($"{Indent()}Values:");
        _indentLevel++;
        foreach (var value in inExpression.ValuesToCompare)
        {
            sb.AppendLine(value.Accept(this));
        }
        _indentLevel--;
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitLikeExpression(LikeExpression likeExpression)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}LIKE (Case {(likeExpression.CaseInsensitive ? "Insensitive" : "Sensitive")}):");
        _indentLevel++;
        sb.AppendLine($"{Indent()}Subject:");
        _indentLevel++;
        sb.AppendLine(likeExpression.Subject.Accept(this));
        _indentLevel--;
        sb.AppendLine($"{Indent()}Pattern:");
        _indentLevel++;
        sb.AppendLine(likeExpression.Pattern.Accept(this));
        _indentLevel--;
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitNotLikeExpression(NotLikeExpression notLikeExpression)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}NOT LIKE:");
        _indentLevel++;
        sb.AppendLine($"{Indent()}Subject:");
        _indentLevel++;
        sb.AppendLine(notLikeExpression.Subject.Accept(this));
        _indentLevel--;
        sb.AppendLine($"{Indent()}Pattern:");
        _indentLevel++;
        sb.AppendLine(notLikeExpression.Pattern.Accept(this));
        _indentLevel--;
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitBetweenExpression(BetweenExpression betweenExpression)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}BETWEEN:");
        _indentLevel++;
        sb.AppendLine($"{Indent()}Expression:");
        _indentLevel++;
        sb.AppendLine(betweenExpression.Expression.Accept(this));
        _indentLevel--;
        sb.AppendLine($"{Indent()}Lower Bound:");
        _indentLevel++;
        sb.AppendLine(betweenExpression.LowerBound.Accept(this));
        _indentLevel--;
        sb.AppendLine($"{Indent()}Upper Bound:");
        _indentLevel++;
        sb.AppendLine(betweenExpression.UpperBound.Accept(this));
        _indentLevel--;
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitFunctionExpression(FunctionExpression function)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}Function: {function.FunctionName}");
        if (function.Arguments.Length != 0)
        {
            _indentLevel++;
            sb.AppendLine($"{Indent()}Arguments:");
            _indentLevel++;
            foreach (var arg in function.Arguments)
            {
                sb.AppendLine(arg.Accept(this));
            }
            _indentLevel--;
            _indentLevel--;
        }
        return sb.ToString();
    }

    public string VisitAggregateFunctionExpression(AggregateFunctionExpression aggregateFunction)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}Aggregate Function: {aggregateFunction.FunctionName}");
        if (aggregateFunction.Arguments.Length != 0)
        {
            _indentLevel++;
            sb.AppendLine($"{Indent()}Arguments:");
            _indentLevel++;
            foreach (var arg in aggregateFunction.Arguments)
            {
                sb.AppendLine(arg.Accept(this));
            }
            _indentLevel--;
            _indentLevel--;
        }
        return sb.ToString();
    }

    public string VisitCaseFunctionExpression(CaseExpression caseFunction)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}CASE:");
        _indentLevel++;
        foreach (var (condition, result) in caseFunction.ConditionResultPairs)
        {
            sb.AppendLine($"{Indent()}WHEN:");
            _indentLevel++;
            sb.AppendLine(condition.Accept(this));
            _indentLevel--;
            sb.AppendLine($"{Indent()}THEN:");
            _indentLevel++;
            sb.AppendLine(result.Accept(this));
            _indentLevel--;
        }
        if (caseFunction.ElseResultExpression is not null)
        {
            sb.AppendLine($"{Indent()}ELSE:");
            _indentLevel++;
            sb.AppendLine(caseFunction.ElseResultExpression.Accept(this));
            _indentLevel--;
        }
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitArithmeticExpression(ArithmeticExpression arithmeticExpression)
    {
        var sb = new StringBuilder();
        sb.AppendLine($"{Indent()}Arithmetic ({arithmeticExpression.ArithmeticOperator}):");
        _indentLevel++;
        sb.AppendLine($"{Indent()}Left:");
        _indentLevel++;
        sb.AppendLine(arithmeticExpression.ExpressionA.Accept(this));
        _indentLevel--;
        sb.AppendLine($"{Indent()}Right:");
        _indentLevel++;
        sb.AppendLine(arithmeticExpression.ExpressionB.Accept(this));
        _indentLevel--;
        _indentLevel--;
        return sb.ToString();
    }

    public string VisitInputPropertyExpression(InputPropertyExpression inputPropertyExpression)
    {
        return $"{Indent()}InputProperty: {inputPropertyExpression.DataKeyLookup}";
    }

    #endregion
}