using System;
using System.Collections.Generic;
using System.IO;
using TLang.Common;

namespace TLang.VM
{
    public class TVMFile
    {
        public List<Class> Classes {get;set;}=new List<Class>();
        public List<Function> Functions {get;set;}=new List<Function>();
        public List<TLangDependency> Dependencies {get;set;}=new List<TLangDependency>();

        public List<Chunk> Chunks {get;set;}=new List<Chunk>();
        public TLangVersion Version {get;set;}
        public RootEnvironment Environment {get;private set;}

        public ChunkExecuter DefaultChunkExecuter => new ChunkExecuter(this,Chunks[0],Environment);
        public TVMFile(Stream file,RootEnvironment env)
        {
            Environment = env;
            byte[] data=new byte[11];
            int read=file.Read(data,0,data.Length);
            CheckData(data,read);
            int deps=ReadBigEndianIntenger(file);
            for(int i = 0;i<deps;i++)
            {
                int nameLen = ReadBigEndianIntenger(file);
                data = new byte[nameLen];
                EnsureRead(file,data);
                string name = System.Text.Encoding.UTF8.GetString(data);
                data = new byte[4];
                EnsureRead(file,data);
                var version = TLangVersion.FromBytes(data,0);
                Dependencies.Add(new TLangDependency(name,version));
            }
            int funcsLen = ReadBigEndianIntenger(file);
            for(int i = 0;i<funcsLen;i++)
            {
                int nameLen = ReadBigEndianIntenger(file);
                data = new byte[nameLen];
                EnsureRead(file,data);
                string name = System.Text.Encoding.UTF8.GetString(data);
                int chunkId = ReadBigEndianIntenger(file);
                Functions.Add(new Function(){Name = name,ChunkId = chunkId});
            }
            int classLen = ReadBigEndianIntenger(file);
            for(int i = 0;i<classLen;i++)
            {
                int nameLen = ReadBigEndianIntenger(file);
                data = new byte[nameLen];
                EnsureRead(file,data);
                string name = System.Text.Encoding.UTF8.GetString(data);
               nameLen = ReadBigEndianIntenger(file);
                data = new byte[nameLen];
                EnsureRead(file,data);
                string inheritsFrom = System.Text.Encoding.UTF8.GetString(data);
                Class classes = new Class();
                classes.Name = name;
                classes.InheritsFrom = inheritsFrom;

                int classEntryCount = ReadBigEndianIntenger(file);
                for(int j = 0;j<classEntryCount;j++)
                {
                    int modifier = file.ReadByte();
                    if(modifier == -1) throw new IOException("End of file");
                     nameLen = ReadBigEndianIntenger(file);
                    data = new byte[nameLen];
                    EnsureRead(file,data);
                    string name2 = System.Text.Encoding.UTF8.GetString(data);
                    int chunkId = ReadBigEndianIntenger(file);
                    classes.ClassEntries.Add(new ClassEntry(){Modifier = (byte)modifier, Name = name2, ChunkId = chunkId});
                }
                Classes.Add(classes);
            }
            int chunks = ReadBigEndianIntenger(file);
            for(int i = 0;i<chunks;i++)
            {
                Chunk chunk = new Chunk();

                int argCount = ReadBigEndianIntenger(file);
                for(int j = 0;j<argCount;j++)
                {
                     int nameLen = ReadBigEndianIntenger(file);
                    data = new byte[nameLen];
                    EnsureRead(file,data);
                    string name2 = System.Text.Encoding.UTF8.GetString(data);
                    chunk.Arguments.Add(name2);
                }

                int length = ReadBigEndianIntenger(file);
                var code = new byte[length];
                int offset = 0;
                int read0 = 0;
                do{
                    read0 = Math.Min(length-offset,1024);
                    if(read0 > 0)
                        read0=file.Read(code,offset,read0);
                    
                    offset+=read0;
                } while(read0 > 0);
                chunk.Code  = code;
                Chunks.Add(chunk);
            }
        }
        private void EnsureRead(Stream file,byte[] data)
        {
            int i = file.Read(data,0,data.Length);
             if(i != data.Length) throw new IndexOutOfRangeException("Array must be filled");
           
        }
        private int ReadBigEndianIntenger(Stream file)
        {
            byte[] bytes=new byte[4];
            EnsureRead(file,bytes);
            if(BitConverter.IsLittleEndian) Array.Reverse(bytes);
            return BitConverter.ToInt32(bytes,0);
        }

        private void CheckData(byte[] data, int read)
        {
            if(read < 11 || data[0] != 'T' || data[1] != 'V' || data[2] != 'M')  throw new BadImageFormatException("TVM file invalid");
            
            if(TLangVersion.FromBytes(data,3).IntegerVersion > TLangVersion.Version.IntegerVersion) throw new BadImageFormatException("TVM Version is too old");

            Version = TLangVersion.FromBytes(data,7);

        }

        public bool LoadDependencies(IDependencyPool dependencyPool)
        {
            foreach(var dep in Dependencies)
            {
                if(!dependencyPool.DependencyExists(dep))
                {
                    if(!dependencyPool.AddDependency(dep,Environment)) return false;
                }
            }
            foreach(var func in Functions)
            {
                Environment.SetObject(func.Name,new TClosure(this,Chunks[func.ChunkId],Environment));
            }
            foreach(var class0 in Classes)
            {
                Environment.AvailableClasses.Add(class0.Name,new LoadedClassData(class0.InheritsFrom,this,class0.ClassEntries));
                Environment.SetObject(class0.Name,new TExternalMethod(args=>{
                    TClassInstance instance = new TClassInstance(this,class0,Environment);
                    instance.Init(args);
                    return instance;
                }));
            }
            return true;
            
        }

        
    }
}