using System.Collections.Generic;
using Esprima.Ast;
using Jint.Runtime.Modules;

namespace Jint
{
    internal readonly struct HoistingScope
    {
        internal readonly List<FunctionDeclaration> _functionDeclarations;

        internal readonly List<VariableDeclaration> _variablesDeclarations;
        internal readonly List<Key> _varNames;

        internal readonly List<Declaration> _lexicalDeclarations;
        internal readonly List<string> _lexicalNames;

        private HoistingScope(
            List<FunctionDeclaration> functionDeclarations,
            List<Key> varNames,
            List<VariableDeclaration> variableDeclarations,
            List<Declaration> lexicalDeclarations,
            List<string> lexicalNames)
        {
            _functionDeclarations = functionDeclarations;
            _varNames = varNames;
            _variablesDeclarations = variableDeclarations;
            _lexicalDeclarations = lexicalDeclarations;
            _lexicalNames = lexicalNames;
        }

        public static HoistingScope GetProgramLevelDeclarations(
            Program script,
            bool collectVarNames = false,
            bool collectLexicalNames = false)
        {
            var treeWalker = new ScriptWalker(StrictModeScope.IsStrictModeCode, collectVarNames, collectLexicalNames);
            treeWalker.Visit(script, null);
            return new HoistingScope(
                treeWalker._functions,
                treeWalker._varNames,
                treeWalker._variableDeclarations,
                treeWalker._lexicalDeclarations,
                treeWalker._lexicalNames);
        }

        public static HoistingScope GetFunctionLevelDeclarations(
            IFunction node,
            bool collectVarNames = false,
            bool collectLexicalNames = false)
        {
            var treeWalker = new ScriptWalker(StrictModeScope.IsStrictModeCode, collectVarNames, collectLexicalNames);
            treeWalker.Visit(node.Body, null);

            return new HoistingScope(
                treeWalker._functions,
                treeWalker._varNames,
                treeWalker._variableDeclarations,
                treeWalker._lexicalDeclarations,
                treeWalker._lexicalNames);
        }

        public static HoistingScope GetModuleLevelDeclarations(
            Module module,
            bool collectVarNames = false,
            bool collectLexicalNames = false)
        {
            //Modules area always strict
            var treeWalker = new ScriptWalker(true, collectVarNames, collectLexicalNames);
            treeWalker.Visit(module, null);
            return new HoistingScope(
                treeWalker._functions,
                treeWalker._varNames,
                treeWalker._variableDeclarations,
                treeWalker._lexicalDeclarations,
                treeWalker._lexicalNames);
        }

        public static List<Declaration> GetLexicalDeclarations(BlockStatement statement)
        {
            List<Declaration> lexicalDeclarations = null;
            ref readonly var statementListItems = ref statement.Body;
            for (var i = 0; i < statementListItems.Count; i++)
            {
                var node = statementListItems[i];
                if (node.Type != Nodes.VariableDeclaration && node.Type != Nodes.FunctionDeclaration)
                {
                    continue;
                }

                if (node is VariableDeclaration { Kind: VariableDeclarationKind.Var })
                {
                    continue;
                }

                lexicalDeclarations ??= new List<Declaration>();
                lexicalDeclarations.Add((Declaration)node);
            }

            return lexicalDeclarations;
        }

        public static List<Declaration> GetLexicalDeclarations(SwitchCase statement)
        {
            List<Declaration> lexicalDeclarations = null;
            ref readonly var statementListItems = ref statement.Consequent;
            for (var i = 0; i < statementListItems.Count; i++)
            {
                var node = statementListItems[i];
                if (node.Type != Nodes.VariableDeclaration)
                {
                    continue;
                }

                var rootVariable = (VariableDeclaration)node;
                if (rootVariable.Kind == VariableDeclarationKind.Var)
                {
                    continue;
                }

                lexicalDeclarations ??= new List<Declaration>();
                lexicalDeclarations.Add(rootVariable);
            }

            return lexicalDeclarations;
        }

        public static void GetImportsAndExports(
            Module module,
            out HashSet<string> requestedModules,
            out List<ImportEntry> importEntries,
            out List<ExportEntry> localExportEntries,
            out List<ExportEntry> indirectExportEntries,
            out List<ExportEntry> starExportEntries)
        {
            var treeWalker = new ModuleWalker();
            treeWalker.Visit(module);

            importEntries = treeWalker._importEntries;
            requestedModules = treeWalker._requestedModules ?? new();
            var importedBoundNames = new HashSet<string>();

            if (importEntries != null)
            {
                for (var i = 0; i < importEntries.Count; i++)
                {
                    var ie = importEntries[i];

                    if (ie.LocalName is not null)
                    {
                        importedBoundNames.Add(ie.LocalName);
                    }
                }
            }

            var exportEntries = treeWalker._exportEntries;
            localExportEntries = new();
            indirectExportEntries = new();
            starExportEntries = new();

            if (exportEntries != null)
            {
                for (var i = 0; i < exportEntries.Count; i++)
                {
                    var ee = exportEntries[i];

                    if (ee.ModuleRequest is null)
                    {
                        if (!importedBoundNames.Contains(ee.LocalName))
                        {
                            localExportEntries.Add(ee);
                        }
                        else
                        {
                            for (var j = 0; j < importEntries!.Count; j++)
                            {
                                var ie = importEntries[j];
                                if (ie.LocalName == ee.LocalName)
                                {
                                    if (ie.ImportName == "*")
                                    {
                                        localExportEntries.Add(ee);
                                    }
                                    else
                                    {
                                        indirectExportEntries.Add(new(ee.ExportName, ie.ModuleRequest, ie.ImportName, null));
                                    }

                                    break;
                                }
                            }
                        }
                    }
                    else if (ee.ImportName == "*" && ee.ExportName is null)
                    {
                        starExportEntries.Add(ee);
                    }
                    else
                    {
                        indirectExportEntries.Add(ee);
                    }
                }
            }
        }

        private sealed class ScriptWalker
        {
            internal List<FunctionDeclaration> _functions;

            private readonly bool _strict;
            private readonly bool _collectVarNames;
            internal List<VariableDeclaration> _variableDeclarations;
            internal List<Key> _varNames;

            private readonly bool _collectLexicalNames;
            internal List<Declaration> _lexicalDeclarations;
            internal List<string> _lexicalNames;

            public ScriptWalker(bool strict, bool collectVarNames, bool collectLexicalNames)
            {
                _strict = strict;
                _collectVarNames = collectVarNames;
                _collectLexicalNames = collectLexicalNames;
            }

            public void Visit(Node node, Node parent)
            {
                foreach (var childNode in node.ChildNodes)
                {
                    if (childNode is null)
                    {
                        // array expression can push null nodes in Esprima
                        continue;
                    }

                    if (childNode.Type == Nodes.VariableDeclaration)
                    {
                        var variableDeclaration = (VariableDeclaration)childNode;
                        if (variableDeclaration.Kind == VariableDeclarationKind.Var)
                        {
                            _variableDeclarations ??= new List<VariableDeclaration>();
                            _variableDeclarations.Add(variableDeclaration);
                            if (_collectVarNames)
                            {
                                _varNames ??= new List<Key>();
                                ref readonly var nodeList = ref variableDeclaration.Declarations;
                                foreach (var declaration in nodeList)
                                {
                                    if (declaration.Id is Identifier identifier)
                                    {
                                        _varNames.Add(identifier.Name);
                                    }
                                }
                            }
                        }

                        if ((parent is null or Module) && variableDeclaration.Kind != VariableDeclarationKind.Var)
                        {
                            _lexicalDeclarations ??= new List<Declaration>();
                            _lexicalDeclarations.Add(variableDeclaration);
                            if (_collectLexicalNames)
                            {
                                _lexicalNames ??= new List<string>();
                                ref readonly var nodeList = ref variableDeclaration.Declarations;
                                foreach (var declaration in nodeList)
                                {
                                    if (declaration.Id is Identifier identifier)
                                    {
                                        _lexicalNames.Add(identifier.Name);
                                    }
                                }
                            }
                        }
                    }
                    else if (childNode.Type == Nodes.FunctionDeclaration
                             // in strict mode cannot include function declarations directly under block or case clauses
                             && (!_strict || parent is null || (node.Type != Nodes.BlockStatement && node.Type != Nodes.SwitchCase)))
                    {
                        _functions ??= new List<FunctionDeclaration>();
                        _functions.Add((FunctionDeclaration)childNode);
                    }
                    else if (childNode.Type == Nodes.ClassDeclaration)
                    {
                        _lexicalDeclarations ??= new List<Declaration>();
                        _lexicalDeclarations.Add((Declaration) childNode);
                    }

                    if (childNode.Type != Nodes.FunctionDeclaration
                        && childNode.Type != Nodes.ArrowFunctionExpression
                        && childNode.Type != Nodes.ArrowParameterPlaceHolder
                        && childNode.Type != Nodes.FunctionExpression
                        && childNode.ChildNodes.Count > 0)
                    {
                        Visit(childNode, node);
                    }
                }
            }
        }

        private sealed class ModuleWalker
        {
            internal List<ImportEntry> _importEntries;
            internal List<ExportEntry> _exportEntries;
            internal HashSet<string> _requestedModules;

            internal void Visit(Node node)
            {
                foreach (var childNode in node.ChildNodes)
                {
                    if (childNode is null)
                    {
                        continue;
                    }

                    if (childNode.Type == Nodes.ImportDeclaration)
                    {
                        _importEntries ??= new();
                        _requestedModules ??= new();
                        var import = childNode as ImportDeclaration;
                        import.GetImportEntries(_importEntries, _requestedModules);
                    }
                    else if (childNode.Type == Nodes.ExportAllDeclaration ||
                             childNode.Type == Nodes.ExportDefaultDeclaration ||
                             childNode.Type == Nodes.ExportNamedDeclaration)
                    {
                        _exportEntries ??= new();
                        _requestedModules ??= new();
                        var export = (ExportDeclaration) childNode;
                        export.GetExportEntries(_exportEntries, _requestedModules);
                    }

                    if (childNode.ChildNodes.Count > 0)
                    {
                        Visit(childNode);
                    }
                }
            }
        }
    }
}