using System;
using System.Linq;
using EpicGames.UHT.Types;

namespace UnrealSharpScriptGenerator.Tooltip;

public static class TooltipParser
{
    private static void ParseTooltip(string inTooltip, ref ParsedTooltip outParsedTooltip)
    {
        string sourceTooltip = inTooltip;
        int sourceTooltipParseIndex = 0;

        void SkipToNextToken()
        {
            while (sourceTooltipParseIndex < sourceTooltip.Length && 
                   (char.IsWhiteSpace(sourceTooltip[sourceTooltipParseIndex]) ||
                    sourceTooltip[sourceTooltipParseIndex] == '-'))
            {
                ++sourceTooltipParseIndex;
            }
        }

        var tokenStartIndex = sourceTooltipParseIndex;

        void ParseSimpleToken(ref ParsedTooltip.TokenString outToken)
        {
            while (sourceTooltipParseIndex < sourceTooltip.Length && !char.IsWhiteSpace(sourceTooltip[sourceTooltipParseIndex]))
            {
                ++sourceTooltipParseIndex;
            }
            
            outToken.SimpleValue = sourceTooltip.Substring(tokenStartIndex, sourceTooltipParseIndex - tokenStartIndex);
        }

        void ParseComplexToken(ref ParsedTooltip.TokenString outToken)
        {
            int startIndex = sourceTooltipParseIndex;
            while (sourceTooltipParseIndex < sourceTooltip.Length && sourceTooltip[sourceTooltipParseIndex] != '@')
            {
                if (char.IsWhiteSpace(sourceTooltip[sourceTooltipParseIndex]))
                {
                    if (startIndex != -1)
                    {
                        outToken.ComplexValue = sourceTooltip.Substring(startIndex, sourceTooltipParseIndex - startIndex);
                        startIndex = -1;
                    }

                    while (sourceTooltipParseIndex < sourceTooltip.Length && char.IsWhiteSpace(sourceTooltip[sourceTooltipParseIndex]))
                    {
                        ++sourceTooltipParseIndex;
                    }
                    
                    while (sourceTooltipParseIndex < sourceTooltip.Length && char.IsWhiteSpace(sourceTooltip[sourceTooltipParseIndex]))
                    {
                        ++sourceTooltipParseIndex;
                    }

                    outToken.ComplexValue += ' ';
                }

                if (sourceTooltipParseIndex < sourceTooltip.Length && sourceTooltip[sourceTooltipParseIndex] != '@')
                {
                    if (startIndex == -1)
                    {
                        outToken.ComplexValue += sourceTooltip[sourceTooltipParseIndex];
                    }

                    ++sourceTooltipParseIndex;
                }
            }

            if (startIndex == -1)
            {
                outToken.ComplexValue = outToken.ComplexValue.TrimEnd();
            }
            else
            {
                outToken.SimpleValue =
                    sourceTooltip.Substring(startIndex, sourceTooltipParseIndex - startIndex);
                outToken.SimpleValue = outToken.SimpleValue.TrimEnd();
            }
        }

        while (sourceTooltipParseIndex < sourceTooltip.Length)
        {
            if (sourceTooltip[sourceTooltipParseIndex] == '@')
            {
                ++sourceTooltipParseIndex;
                if (sourceTooltipParseIndex < sourceTooltip.Length && sourceTooltip[sourceTooltipParseIndex] == '@')
                {
                    outParsedTooltip.BasicTooltipText += '@';
                    ++sourceTooltipParseIndex;
                    continue;
                }

                var tokenName = new ParsedTooltip.TokenString();
                SkipToNextToken();
                ParseSimpleToken(ref tokenName);

                if (tokenName.Value == "param")
                {
                    var paramToken = new ParsedTooltip.ParamToken();

                    SkipToNextToken();
                    ParseSimpleToken(ref paramToken.ParamName);

                    SkipToNextToken();
                    ParseComplexToken(ref paramToken.ParamComment);

                    outParsedTooltip.ParamTokens.Add(paramToken);
                }
                else if (tokenName.Value is "return" or "returns")
                {
                    SkipToNextToken();
                    ParseComplexToken(ref outParsedTooltip.ReturnToken.ParamComment);
                }
                else
                {
                    var miscToken = new ParsedTooltip.MiscToken
                    {
                        TokenName = tokenName
                    };

                    SkipToNextToken();
                    ParseComplexToken(ref miscToken.TokenValue);

                    outParsedTooltip.MiscTokens.Add(miscToken);
                }
            }
            else
            {
                outParsedTooltip.BasicTooltipText += sourceTooltip[sourceTooltipParseIndex++];
            }
        }
    }

    public static void AppendTooltip(this GeneratorStringBuilder builder, string toolTip)
    {
        if (string.IsNullOrEmpty(toolTip))
        {
            return;
        }

        ParsedTooltip parsedTooltip = new();
        ParseTooltip(toolTip, ref parsedTooltip);

        if (!string.IsNullOrEmpty(parsedTooltip.BasicTooltipText))
        {
            string[] lines = parsedTooltip.BasicTooltipText.Split(new[] { '\n' }, StringSplitOptions.None);
            
            builder.AppendLine("/// <summary>");
            foreach (var line in lines)
            {
                builder.AppendLine($"/// {line}");
            }
            builder.AppendLine("/// </summary>");
        }

        if (parsedTooltip.ParamTokens.Any())
        {
            foreach (var miscToken in parsedTooltip.ParamTokens)
            {
                builder.AppendLine($"/// <param name=\"{miscToken.ParamName.Value}\">{miscToken.ParamComment.Value}</param>");
            }
        }

        var returnToolTip = parsedTooltip.ReturnToken.ParamComment.Value;
        if (string.IsNullOrEmpty(returnToolTip))
        {
            return;
        }

        builder.AppendLine("/// <returns>");
        builder.Append(returnToolTip);
        builder.Append("</returns>");
    }

    public static void AppendTooltip(this GeneratorStringBuilder builder, UhtType type)
    {
        string toolTip = type.GetToolTipText();
        
        // Skip if the tooltip is just the same as the source name. UHT automatically generates these.
        if (toolTip == type.SourceName)
        {
            return;
        }
        
        AppendTooltip(builder, toolTip);
    }
}