BadIfNodeTransformer.cs

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using System.Collections.Generic;
 
using BadScript2.Runtime;
using BadScript2.Runtime.Error;
using BadScript2.Runtime.Objects;
using BadScript2.Runtime.Objects.Native;
 
using HtmlAgilityPack;
 
namespace BadHtml.Transformer;
 
public class BadIfNodeTransformer : BadHtmlNodeTransformer
{
    protected override bool CanTransform(BadHtmlContext context)
    {
        return context.InputNode.Name == "bs:if";
    }
 
    private static List<(HtmlAttribute, IEnumerable<HtmlNode>)> DissectContent(BadHtmlContext context,
                                                                               HtmlNode node,
                                                                               out IEnumerable<HtmlNode>? elseBranch)
    {
        List<(HtmlAttribute, IEnumerable<HtmlNode>)> branches = new List<(HtmlAttribute, IEnumerable<HtmlNode>)>();
        List<HtmlNode> currentBranch = new List<HtmlNode>();
        HtmlAttribute? conditionAttribute = node.Attributes["test"];
 
        if (conditionAttribute == null)
        {
            throw BadRuntimeException.Create(context.ExecutionContext.Scope,
                                             "Missing 'test' attribute in 'bs:if' node",
                                             context.CreateOuterPosition()
                                            );
        }
 
        if (string.IsNullOrEmpty(conditionAttribute.Value))
        {
            throw BadRuntimeException.Create(context.ExecutionContext.Scope,
                                             "Empty 'test' attribute in 'bs:if' node",
                                             context.CreateAttributePosition(conditionAttribute)
                                            );
        }
 
        foreach (HtmlNode child in node.ChildNodes)
        {
            if (child.Name == "bs:else")
            {
                branches.Add((conditionAttribute!, currentBranch));
 
                currentBranch = new List<HtmlNode>();
                HtmlAttribute? nextCondition = child.Attributes["test"];
 
                if (conditionAttribute == null)
                {
                    if (nextCondition != null)
                    {
                        throw BadRuntimeException.Create(context.ExecutionContext.Scope,
                                                         "Found bs:else node with attribute 'test' after bs:else node without 'test' attribute",
                                                         context.CreateAttributePosition(nextCondition)
                                                        );
                    }
 
                    throw BadRuntimeException.Create(context.ExecutionContext.Scope,
                                                     "Found bs:else node after bs:else node without 'test' attribute",
                                                     context.CreateInnerPosition()
                                                    );
                }
 
                conditionAttribute = child.Attributes["test"];
 
                if (conditionAttribute == null)
                {
                    continue;
                }
 
                if (string.IsNullOrEmpty(conditionAttribute.Value))
                {
                    throw BadRuntimeException.Create(context.ExecutionContext.Scope,
                                                     "Empty 'test' attribute in 'bs:else' node",
                                                     context.CreateAttributePosition(conditionAttribute)
                                                    );
                }
            }
            else
            {
                currentBranch.Add(child);
            }
        }
 
        if (conditionAttribute == null)
        {
            elseBranch = currentBranch;
        }
        else
        {
            elseBranch = null;
            branches.Add((conditionAttribute, currentBranch));
        }
 
        return branches;
    }
 
    private static bool EvaluateCondition(BadHtmlContext context, HtmlAttribute conditionAttribute)
    {
        BadObject resultObj = context.ParseAndExecuteSingle(conditionAttribute.Value,
                                                            context.CreateAttributePosition(conditionAttribute)
                                                           );
 
        if (resultObj is not IBadBoolean result)
        {
            throw BadRuntimeException.Create(context.ExecutionContext.Scope,
                                             "Result of 'test' attribute in 'bs:if' node is not a boolean",
                                             context.CreateAttributePosition(conditionAttribute)
                                            );
        }
 
        return result.Value;
    }
 
    protected override void TransformNode(BadHtmlContext context)
    {
        List<(HtmlAttribute, IEnumerable<HtmlNode>)> branches =
            DissectContent(context, context.InputNode, out IEnumerable<HtmlNode>? elseBranch);
 
        bool executedAny = false;
 
        foreach ((HtmlAttribute condition, IEnumerable<HtmlNode> block) branch in branches)
        {
            if (!EvaluateCondition(context, branch.condition))
            {
                continue;
            }
 
            executedAny = true;
 
            using BadExecutionContext branchContext =
                new BadExecutionContext(context.ExecutionContext.Scope.CreateChild("bs:if",
                                             context.ExecutionContext.Scope,
                                             null
                                            )
                                       );
 
            foreach (HtmlNode? child in branch.block)
            {
                BadHtmlContext childContext = context.CreateChild(child, context.OutputNode, branchContext);
 
                Transform(childContext);
            }
        }
 
        if (executedAny || elseBranch == null)
        {
            return;
        }
 
        using BadExecutionContext elseContext =
            new BadExecutionContext(context.ExecutionContext.Scope.CreateChild("bs:if",
                                                                               context.ExecutionContext.Scope,
                                                                               null
                                                                              )
                                   );
 
        foreach (HtmlNode? child in elseBranch)
        {
            BadHtmlContext childContext = context.CreateChild(child, context.OutputNode, elseContext);
 
            Transform(childContext);
        }
    }
}