using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime;
using System.Text;
using System.Threading.Tasks;
using NTERA.Engine.Compiler;

namespace NTERA.Engine.Runtime
{
	public class JITCompiler : IExecutionProvider
	{
		public ICollection<FunctionDefinition> DefinedProcedures { get; protected set; }
		public ICollection<FunctionDefinition> DefinedFunctions { get; protected set; }
		public ICollection<FunctionVariable> DefinedConstants { get; protected set; }
		public CSVDefinition CSVDefinition { get; protected set; }

		protected Dictionary<FunctionDefinition, string> ProcedureFiles { get; set; }
		public Dictionary<FunctionDefinition, ExecutionNode[]> CompiledProcedures { get; protected set; } = new Dictionary<FunctionDefinition, ExecutionNode[]>();

		public string InputDirectory { get; }

		public static int Threads = 4;

		public JITCompiler(string path)
		{
			InputDirectory = path;

			Compile();
		}

		protected void Compile()
		{
			string csvPath = Path.Combine(InputDirectory, "CSV");
			string erbPath = Path.Combine(InputDirectory, "ERB");

			var csvDefinition = new CSVDefinition();

			Console.WriteLine("Preprocessing CSV files...");


			foreach (var file in Directory.EnumerateFiles(csvPath, "*.csv", SearchOption.AllDirectories))
			{
				string path = Path.GetFileNameWithoutExtension(file);

				if (path.EndsWith("_TR"))
					continue;

				Preprocessor.ProcessCSV(csvDefinition, path, File.ReadLines(file, Encoding.UTF8));
			}

			Console.WriteLine("Preprocessing header files...");

			ConcurrentBag<FunctionVariable> preprocessedConstants = new ConcurrentBag<FunctionVariable>();

#if DEBUG
			foreach (var file in Directory.EnumerateFiles(erbPath, "*.erh", SearchOption.AllDirectories))
#else
			Parallel.ForEach(Directory.EnumerateFiles(erbPath, "*.erh", SearchOption.AllDirectories), new ParallelOptions
			{
				MaxDegreeOfParallelism = Threads
			}, file =>
#endif
			{
				foreach (var variable in Preprocessor.PreprocessHeaderFile(File.ReadAllText(file)))
					preprocessedConstants.Add(variable);
#if DEBUG
			}
#else
			});
#endif

			DefinedConstants = preprocessedConstants.ToArray();

			Console.WriteLine("Preprocessing functions...");

			ProcedureFiles = new Dictionary<FunctionDefinition, string>();
			ConcurrentDictionary<FunctionDefinition, string> preprocessedFunctions = new ConcurrentDictionary<FunctionDefinition, string>();

#if DEBUG
			foreach (var file in Directory.EnumerateFiles(erbPath, "*.erb", SearchOption.AllDirectories))
#else
			Parallel.ForEach(Directory.EnumerateFiles(erbPath, "*.erb", SearchOption.AllDirectories), new ParallelOptions
			{
				MaxDegreeOfParallelism = Threads
			}, file =>
#endif
			{
				foreach (var kv in Preprocessor.PreprocessCodeFile(File.ReadAllText(file), Path.GetFileName(file), DefinedConstants))
				{
					preprocessedFunctions[kv.Key] = kv.Value;
					ProcedureFiles[kv.Key] = file;
				}
#if DEBUG
			}
#else
			});
#endif
			DefinedProcedures = preprocessedFunctions.Select(kv => kv.Key).ToArray();

			var declaredFunctions = BaseDefinitions.DefaultGlobalFunctions.ToList();
			declaredFunctions.AddRange(DefinedProcedures.Where(x => x.IsReturnFunction));
			DefinedFunctions = declaredFunctions;

			GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce;
			GC.Collect();
		}

		public IEnumerable<ExecutionNode> GetExecutionNodes(FunctionDefinition function)
		{
			if (CompiledProcedures.ContainsKey(function))
				return CompiledProcedures[function];

			string filename = ProcedureFiles[function];
			var preprocessed = Preprocessor.PreprocessCodeFile(File.ReadAllText(filename), Path.GetFileName(filename), DefinedConstants);

			Parser parser = new Parser(preprocessed.Single(x => x.Key.Name == function.Name).Value, function, DefinedFunctions, DefinedProcedures.Where(x => !x.IsReturnFunction).ToArray(), BaseDefinitions.DefaultGlobalVariables, function.Variables, BaseDefinitions.DefaultKeywords, CSVDefinition, DefinedConstants);

			var nodes = parser.Parse(out var localErrors, out var localWarnings)?.ToArray();

			if (localErrors.Count > 0)
				throw new ParserException($"Failed to compile '{function.Name}'");

			CompiledProcedures.Add(function, nodes);

			return nodes;
		}
	}
}