using System;
using System.Collections;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;
using ServiceStack.Model;
using ServiceStack.Text;
using ServiceStack.Web;

namespace ServiceStack.Script
{
    public enum InvokerType
    {
        Filter,
        ContextFilter,
        ContextBlock,
    }

    public interface IResultInstruction {}
    public class IgnoreResult : IResultInstruction
    {
        public static readonly IgnoreResult Value = new IgnoreResult();
        private IgnoreResult(){}
    }

    public class StopExecution : IResultInstruction
    {
        public static StopExecution Value = new StopExecution();
        private StopExecution() { }
    }

    public class StopFilterExecutionException : StopExecutionException, IResponseStatusConvertible
    {
        public ScriptScopeContext Scope { get; }
        public object Options { get; }

        public StopFilterExecutionException(ScriptScopeContext scope, object options, Exception innerException) 
            : base(nameof(StopFilterExecutionException), innerException)
        {
            Scope = scope;
            Options = options;
        }

        public ResponseStatus ToResponseStatus()
        {
            var ex = InnerException ?? this;
            return new ResponseStatus {
                ErrorCode = ex.GetType().Name,
                Message = ex.Message,
                StackTrace = ex.StackTrace.LeftPart('\n'),
                Meta = new Dictionary<string, string> {
                    [GetType().Name] = Message + "\n" + this.StackTrace.LeftPart('\n')
                }
            };
        }
    }

    public class ScriptException : Exception
    {
        public PageResult PageResult { get; }
        public string PageStackTrace => PageResult.LastFilterStackTrace.Map(x => "   at " + x).Join(Environment.NewLine);

        public ScriptException(PageResult pageResult) : base(
            pageResult.LastFilterError?.Message ?? throw new ArgumentNullException(nameof(pageResult)),
            pageResult.LastFilterError)
        {
            PageResult = pageResult;
        }
    }

    public class ScriptMethods
    {
        public ScriptContext Context { get; set; }
        public ISharpPages Pages { get; set; }
        
        private readonly Dictionary<string, MethodInfo> lookupIndex = new Dictionary<string, MethodInfo>();

        public ScriptMethods()
        {
            var methods = GetType().GetMethods(BindingFlags.Instance | BindingFlags.Public);
            foreach (var method in methods)
            {
                var paramType = method.GetParameters().FirstOrDefault()?.ParameterType;
                var hasScope = paramType == typeof(ScriptScopeContext) || paramType == typeof(Templates.TemplateScopeContext);
                var hasTaskReturnType = method.ReturnType == typeof(Task);
                var isFilter = !hasScope && !hasTaskReturnType;
                var isContextFilter = hasScope && !hasTaskReturnType;
                var isBlockFilter = hasScope && hasTaskReturnType;
                if (!isFilter && !isContextFilter && !isBlockFilter)
                    continue;

                var filterType = isBlockFilter
                    ? InvokerType.ContextBlock
                    : isContextFilter
                        ? InvokerType.ContextFilter
                        : InvokerType.Filter;

                var key = CacheKey(filterType, method.Name, method.GetParameters().Length);
                lookupIndex[key] = method;
            }
        }

        private string CacheKey(InvokerType type, string methodName, int argsCount) =>
            type + "::" + methodName + "`" + argsCount;

        private MethodInfo GetFilterMethod(string cacheKey) => lookupIndex.TryGetValue(cacheKey, out MethodInfo method) ? method : null;

        public List<MethodInfo> QueryFilters(string filterName)
        {
            var filters = GetType().GetMethods(BindingFlags.Instance | BindingFlags.Public)
                .Where(x => x.Name.IndexOf(filterName, StringComparison.OrdinalIgnoreCase) >= 0)
                .ToList();
            return filters;
        }

        public ConcurrentDictionary<string, MethodInvoker> InvokerCache { get; } = new ConcurrentDictionary<string, MethodInvoker>();

        public MethodInvoker GetInvoker(string name, int argsCount, InvokerType type)
        {
            if (name == null)
                throw new ArgumentNullException(nameof(name));

            var key = CacheKey(type, name, argsCount);
            if (InvokerCache.TryGetValue(key, out MethodInvoker invoker))
                return invoker;

            var method = GetFilterMethod(key);
            if (method == null)
                return null;

            return InvokerCache[key] = TypeExtensions.GetInvokerToCache(method);
        }
    }

    public static class TemplateFilterUtils
    {
        public static Dictionary<string, object> AssertOptions(this ScriptScopeContext scope, string filterName, object scopedParams)
        {
            var pageParams = scopedParams as Dictionary<string, object>;
            if (pageParams == null && scopedParams != null)
                throw new ArgumentException(
                    $"{filterName} in '{scope.PageResult.VirtualPath}' only accepts an Object dictionary as an argument but received a '{scopedParams.GetType().Name}' instead");

            return pageParams ?? new Dictionary<string, object>();
        }
        
        public static Dictionary<string, object> AssertOptions(this object scopedParams, string filterName)
        {
            var pageParams = scopedParams as Dictionary<string, object>;
            if (pageParams == null && scopedParams != null)
                throw new ArgumentException(
                    $"{filterName} only accepts an Object dictionary as an argument but received a '{scopedParams.GetType().Name}' instead");

            return pageParams ?? new Dictionary<string, object>();
        }

        public static object AssertNoCircularDeps(this object value)
        {
            if (value != null && TypeSerializer.HasCircularReferences(value))
                throw new NotSupportedException($"Cannot serialize type '{value.GetType().Name}' with cyclical dependencies");
            return value;
        }

        public static IEnumerable<object> AssertEnumerable(this object items, string filterName)
        {
            var enumObjects = items as IEnumerable<object>;
            if (enumObjects == null && items != null)
            {
                if (items is IEnumerable enumItems)
                {
                    var to = new List<object>();
                    foreach (var item in enumItems)
                    {
                        to.Add(item);
                    }
                    return to;
                }
                
                throw new ArgumentException(
                    $"{filterName} expects an IEnumerable but received a '{items.GetType().Name}' instead");
            }

            return enumObjects ?? TypeConstants.EmptyObjectArray;
        }

        public static string AssertExpression(this ScriptScopeContext scope, string filterName, object expression)
        {
            if (!(expression is string literal)) 
                throw new NotSupportedException($"'{filterName}' in '{scope.PageResult.VirtualPath}' requires a string Expression but received a '{expression?.GetType()?.Name}' instead");
            return literal;
        }

        public static JsToken AssertExpression(this ScriptScopeContext scope, string filterName, object expression, object scopeOptions, out string itemBinding)
        {
            if (expression is JsArrowFunctionExpression arrowExpr)
            {
                itemBinding = arrowExpr.Params[0].Name;
                return arrowExpr.Body;
            }
            
            var literal = scope.AssertExpression(filterName, expression);
            var scopedParams = scope.GetParamsWithItemBinding(filterName, scopeOptions, out itemBinding);

            var token = literal.GetCachedJsExpression(scope);
            return token;
        }

        public static Dictionary<string, object> GetParamsWithItemBinding(this ScriptScopeContext scope, string filterName, object scopedParams, out string itemBinding) =>
            GetParamsWithItemBinding(scope, filterName, null, scopedParams, out itemBinding);

        public static Dictionary<string, object> GetParamsWithItemBinding(this ScriptScopeContext scope, string filterName, SharpPage page, object scopedParams, out string itemBinding)
        {
            var scopeParams = scope.GetParamsWithItemBindingOnly(filterName, page, scopedParams, out itemBinding);
            scopeParams.Each((key, val) => scope.ScopedParams[key] = val);
            return scopeParams;
        }

        public static Dictionary<string, object> GetParamsWithItemBindingOnly(this ScriptScopeContext scope, string filterName, SharpPage page, object scopedParams, out string itemBinding)
        {
            var pageParams = scope.AssertOptions(filterName, scopedParams);
            itemBinding = pageParams.TryGetValue("it", out object bindingName) && bindingName is string binding
                ? binding
                : "it";
            
            if (bindingName != null && !(bindingName is string))
                throw new NotSupportedException($"'it' option in filter '{filterName}' should contain the name to bind to but contained a '{bindingName.GetType().Name}' instead");

            // page vars take precedence
            if (page != null && page.Args.TryGetValue("it", out object pageBinding))
                itemBinding = (string)pageBinding;
            
            return pageParams;
        }

        public static ScriptScopeContext AddItemToScope(this ScriptScopeContext scope, string itemBinding, object item, int index)
        {
            scope.ScopedParams[ScriptConstants.Index] = index;
            return SetItemInScope(itemBinding, item, scope);
        }

        public static ScriptScopeContext AddItemToScope(this ScriptScopeContext scope, string itemBinding, object item)
        {
            return SetItemInScope(itemBinding, item, scope);
        }

        private static ScriptScopeContext SetItemInScope(string itemBinding, object item, ScriptScopeContext newScope)
        {
            newScope.ScopedParams[itemBinding] = item;

            if (item is ScopeVars explodeBindings)
            {
                foreach (var entry in explodeBindings)
                {
                    newScope.ScopedParams[entry.Key] = entry.Value;
                }
            }

            return newScope;
        }

        public static T GetValueOrEvaluateBinding<T>(this ScriptScopeContext scope, object valueOrBinding) =>
            (T)GetValueOrEvaluateBinding(scope, valueOrBinding, typeof(T));

        public static object GetValueOrEvaluateBinding(this ScriptScopeContext scope, object valueOrBinding, Type returnType)
        {
            if (valueOrBinding is string literal)
            {
                literal.ParseJsExpression(out var token);
                var oValue = token.Evaluate(scope);
                return oValue.ConvertTo(returnType);
            }
            
            return valueOrBinding.ConvertTo(returnType);
        }

        public static bool TryGetPage(this ScriptScopeContext scope, string virtualPath, out SharpPage page, out SharpCodePage codePage)
        {
            if (scope.PageResult.Partials.TryGetValue(virtualPath, out page))
            {
                codePage = null;
                return true;
            }
            
            if (!scope.Context.TryGetPage(scope.PageResult.VirtualPath, virtualPath, out page, out codePage))
                return false;
            
            codePage?.Init();

            if (codePage is IRequiresRequest requiresRequest)
            {
                if (scope.GetValue(ScriptConstants.Request) is IRequest request)
                    requiresRequest.Request = request;
            }

            return true;
        }
        
        public static ScriptContext CreateNewContext(this ScriptScopeContext scope, Dictionary<string, object> args)
        {
            if (args == null)
                return new ScriptContext().Init();
            
            var context = new ScriptContext();
            if (args.TryGetValue("use", out var oUse))
            {
                var use = (Dictionary<string, object>) oUse;
                if (use.TryGetValue("context", out var oContext) && oContext is bool useContext && useContext)
                {
                    return scope.Context;
                }

                // Use same ThreadSafe plugin instance to preserve configuration 
                var plugins = use.TryGetValue("plugins", out var oPlugins)
                    ? ViewUtils.ToStrings("plugins", oPlugins)
                    : null;
                if (plugins != null)
                {
                    foreach (var name in plugins)
                    {
                        var plugin = scope.Context.Plugins.FirstOrDefault(x => x.GetType().Name == name);
                        if (plugin == null)
                            throw new NotSupportedException($"Plugin '{name}' is not registered in parent context");
                            
                        context.Plugins.Add(plugin);
                    }
                }

                // Use new filter and block instances which cannot be shared between contexts
                var methods = use.TryGetValue("methods", out var oMethods)
                    ? ViewUtils.ToStrings("methods", oMethods)
                    : use.TryGetValue("filters", out var oFilters)
                        ? ViewUtils.ToStrings("filters", oFilters)
                        : null;
                if (methods != null)
                {
                    foreach (var name in methods)
                    {
                        var filter = scope.Context.ScriptMethods.FirstOrDefault(x => x.GetType().Name == name);
                        if (filter == null)
                            throw new NotSupportedException($"Filter '{name}' is not registered in parent context");
                            
                        context.ScriptMethods.Add(filter.GetType().CreateInstance<ScriptMethods>());
                    }
                }
                    
                var blocks = use.TryGetValue("blocks", out var oBlocks)
                    ? ViewUtils.ToStrings("blocks", oBlocks)
                    : null;
                if (blocks != null)
                {
                    foreach (var name in blocks)
                    {
                        var useBlock = scope.Context.ScriptBlocks.FirstOrDefault(x => x.GetType().Name == name);
                        if (useBlock == null)
                            throw new NotSupportedException($"Block '{name}' is not registered in parent context");
                            
                        context.ScriptBlocks.Add(useBlock.GetType().CreateInstance<ScriptBlock>());
                    }
                }

                args.Remove(nameof(use));
            }
            context.Init();

            return context;
        }
        
    }
}