// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Collections;
using System.Diagnostics;
using System.Xml;
using System.Xml.XPath;

namespace System.Xml.Xsl.XsltOld
{
    internal sealed class ApplyTemplatesAction : ContainerAction
    {
        private const int ProcessedChildren = 2;
        private const int ProcessNextNode = 3;
        private const int PositionAdvanced = 4;
        private const int TemplateProcessed = 5;

        private int _selectKey = Compiler.InvalidQueryKey;
        private XmlQualifiedName? _mode;

        //
        //  <xsl:template match="*|/" [mode="?"]>
        //    <xsl:apply-templates [mode="?"]/>
        //  </xsl:template>
        //

        private static readonly ApplyTemplatesAction s_BuiltInRule = new ApplyTemplatesAction();

        internal static ApplyTemplatesAction BuiltInRule()
        {
            Debug.Assert(s_BuiltInRule != null);
            return s_BuiltInRule;
        }

        internal static ApplyTemplatesAction BuiltInRule(XmlQualifiedName? mode)
        {
            return (mode == null || mode.IsEmpty) ? BuiltInRule() : new ApplyTemplatesAction(mode);
        }

        internal ApplyTemplatesAction() { }

        private ApplyTemplatesAction(XmlQualifiedName mode)
        {
            Debug.Assert(mode != null);
            _mode = mode;
        }

        internal override void Compile(Compiler compiler)
        {
            CompileAttributes(compiler);
            CompileContent(compiler);
        }

        internal override bool CompileAttribute(Compiler compiler)
        {
            string name = compiler.Input.LocalName;
            string value = compiler.Input.Value;
            if (Ref.Equal(name, compiler.Atoms.Select))
            {
                _selectKey = compiler.AddQuery(value);
            }
            else if (Ref.Equal(name, compiler.Atoms.Mode))
            {
                Debug.Assert(_mode == null);
                _mode = compiler.CreateXPathQName(value);
            }
            else
            {
                return false;
            }

            return true;
        }

        private void CompileContent(Compiler compiler)
        {
            NavigatorInput input = compiler.Input;

            if (compiler.Recurse())
            {
                do
                {
                    switch (input.NodeType)
                    {
                        case XPathNodeType.Element:
                            compiler.PushNamespaceScope();
                            string nspace = input.NamespaceURI;
                            string name = input.LocalName;

                            if (Ref.Equal(nspace, input.Atoms.UriXsl))
                            {
                                if (Ref.Equal(name, input.Atoms.Sort))
                                {
                                    AddAction(compiler.CreateSortAction());
                                }
                                else if (Ref.Equal(name, input.Atoms.WithParam))
                                {
                                    WithParamAction par = compiler.CreateWithParamAction();
                                    CheckDuplicateParams(par.Name!);
                                    AddAction(par);
                                }
                                else
                                {
                                    throw compiler.UnexpectedKeyword();
                                }
                            }
                            else
                            {
                                throw compiler.UnexpectedKeyword();
                            }
                            compiler.PopScope();
                            break;

                        case XPathNodeType.Comment:
                        case XPathNodeType.ProcessingInstruction:
                        case XPathNodeType.Whitespace:
                        case XPathNodeType.SignificantWhitespace:
                            break;

                        default:
                            throw XsltException.Create(SR.Xslt_InvalidContents, "apply-templates");
                    }
                }
                while (compiler.Advance());

                compiler.ToParent();
            }
        }

        internal override void Execute(Processor processor, ActionFrame frame)
        {
            Debug.Assert(processor != null && frame != null);

            switch (frame.State)
            {
                case Initialized:
                    processor.ResetParams();
                    processor.InitSortArray();
                    if (this.containedActions != null && this.containedActions.Count > 0)
                    {
                        processor.PushActionFrame(frame);
                        frame.State = ProcessedChildren;
                        break;
                    }
                    goto case ProcessedChildren;
                case ProcessedChildren:
                    if (_selectKey == Compiler.InvalidQueryKey)
                    {
                        if (!frame.Node!.HasChildren)
                        {
                            frame.Finished();
                            break;
                        }
                        frame.InitNewNodeSet(frame.Node.SelectChildren(XPathNodeType.All));
                    }
                    else
                    {
                        frame.InitNewNodeSet(processor.StartQuery(frame.NodeSet!, _selectKey));
                    }
                    if (processor.SortArray.Count != 0)
                    {
                        frame.SortNewNodeSet(processor, processor.SortArray);
                    }
                    frame.State = ProcessNextNode;
                    goto case ProcessNextNode;

                case ProcessNextNode:
                    Debug.Assert(frame.State == ProcessNextNode);
                    Debug.Assert(frame.NewNodeSet != null);

                    if (frame.NewNextNode(processor))
                    {
                        frame.State = PositionAdvanced;
                        goto case PositionAdvanced;
                    }
                    else
                    {
                        frame.Finished();
                        break;
                    }

                case PositionAdvanced:
                    Debug.Assert(frame.State == PositionAdvanced);

                    processor.PushTemplateLookup(frame.NewNodeSet, _mode, /*importsOf:*/null);

                    frame.State = TemplateProcessed;
                    break;

                case TemplateProcessed:
                    frame.State = ProcessNextNode;
                    goto case ProcessNextNode;

                default:
                    Debug.Fail("Invalid ApplyTemplatesAction execution state");
                    break;
            }
        }
    }
}