using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Text.Json;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace WTelegram
{
	public class Generator
	{
		//TODO: generate BinaryReader/Writer serialization for objects too?
		readonly Dictionary<int, string> ctorToTypes = new();
		readonly HashSet<string> allTypes = new();
		readonly Dictionary<int, Dictionary<string, TypeInfo>> typeInfosByLayer = new();
		readonly Dictionary<string, int> knownStyles = new() { ["InitConnection"] = 1, ["Help_GetConfig"] = 0, ["HttpWait"] = -1 };
		Dictionary<string, TypeInfo> typeInfos;
		int currentLayer;
		string tabIndent;
		private string currentJson;

		public async Task FromWeb()
		{
			Console.WriteLine("Fetch web pages...");
#if DEBUG
			currentLayer = await Task.FromResult(0);
#else
			using var http = new HttpClient();
			var html = await http.GetStringAsync("https://core.telegram.org/api/layers");
			currentLayer = int.Parse(Regex.Match(html, @"#layer-(\d+)").Groups[1].Value);
			File.WriteAllBytes("TL.MTProto.json", await http.GetByteArrayAsync("https://core.telegram.org/schema/mtproto-json"));
			File.WriteAllBytes("TL.Schema.json", await http.GetByteArrayAsync("https://core.telegram.org/schema/json"));
			File.WriteAllBytes("TL.Secret.json", await http.GetByteArrayAsync("https://core.telegram.org/schema/end-to-end-json"));
#endif
			FromJson("TL.MTProto.json", "TL.MTProto.cs", @"TL.Table.cs");
			FromJson("TL.Schema.json", "TL.Schema.cs", @"TL.Table.cs");
			FromJson("TL.Secret.json", "TL.Secret.cs", @"TL.Table.cs");
		}

		public void FromJson(string jsonPath, string outputCs, string tableCs = null)
		{
			Console.WriteLine("Parsing " + jsonPath);
			currentJson = Path.GetFileNameWithoutExtension(jsonPath);
			var schema = JsonSerializer.Deserialize<SchemaJson>(File.ReadAllText(jsonPath));
			using var sw = File.CreateText(outputCs);
			sw.WriteLine("// This file is (mainly) generated automatically using the Generator class");
			sw.WriteLine("using System;");
			if (schema.methods.Count != 0) sw.WriteLine("using System.Threading.Tasks;");
			sw.WriteLine();
			sw.WriteLine("namespace TL");
			sw.Write("{");
			tabIndent = "\t";
			var layers = schema.constructors.GroupBy(c => c.layer).OrderBy(g => g.Key);
			foreach (var layer in layers)
			{
				typeInfos = typeInfosByLayer.GetOrCreate(layer.Key);
				if (layer.Key != 0)
				{
					sw.WriteLine();
					sw.WriteLine("\tnamespace Layer" + layer.Key);
					sw.Write("\t{");
					tabIndent += "\t";
				}
				string layerPrefix = layer.Key == 0 ? "" : $"Layer{layer.Key}.";
				foreach (var ctor in layer)
				{
					if (ctorToTypes.ContainsKey(ctor.ID)) continue;
					if (ctor.type == "Vector t") continue;
					var structName = CSharpName(ctor.predicate);
					ctorToTypes[ctor.ID] = layerPrefix + structName;
					var typeInfo = typeInfos.GetOrCreate(ctor.type);
					if (ctor.ID == 0x5BB8E511) { ctorToTypes[ctor.ID] = structName = ctor.predicate = ctor.type = "_Message"; }
					if (typeInfo.ReturnName == null) typeInfo.ReturnName = CSharpName(ctor.type);
					typeInfo.Structs.Add(ctor);
					if (structName == typeInfo.ReturnName) typeInfo.SameName = ctor;
				}
				foreach (var (name, typeInfo) in typeInfos)
				{
					if (allTypes.Contains(typeInfo.ReturnName)) { typeInfo.NeedAbstract = -2; continue; }
					if (typeInfo.SameName == null)
					{
						typeInfo.NeedAbstract = -1;
						if (typeInfo.Structs.Count > 1)
						{
							List<Param> fakeCtorParams = new();
							while (typeInfo.Structs[0].@params.Length > fakeCtorParams.Count)
							{
								fakeCtorParams.Add(typeInfo.Structs[0].@params[fakeCtorParams.Count]);
								if (!typeInfo.Structs.All(ctor => HasPrefix(ctor, fakeCtorParams)))
								{
									fakeCtorParams.RemoveAt(fakeCtorParams.Count - 1);
									break;
								}
							}
							if (fakeCtorParams.Count > 0)
							{
								typeInfo.Structs.Insert(0, typeInfo.SameName = new Constructor
								{ id = null, @params = fakeCtorParams.ToArray(), predicate = typeInfo.ReturnName, type = typeInfo.ReturnName });
								typeInfo.NeedAbstract = fakeCtorParams.Count;
							}
						}
					}
					else if (typeInfo.Structs.Count > 1)
					{
						typeInfo.NeedAbstract = typeInfo.SameName.@params.Length;
						foreach (var ctor in typeInfo.Structs)
						{
							if (ctor == typeInfo.SameName) continue;
							if (!HasPrefix(ctor, typeInfo.SameName.@params)) { typeInfo.NeedAbstract = -1; typeInfo.ReturnName += "Base"; break; }
						}
					}
				}
				foreach (var typeInfo in typeInfos.Values)
					WriteTypeInfo(sw, typeInfo, layerPrefix, false);
				if (layer.Key != 0)
				{
					sw.WriteLine("\t}");
					tabIndent = tabIndent[1..];
				}
			}
			if (typeInfosByLayer[0]["Message"].SameName.ID == 0x5BB8E511) typeInfosByLayer[0].Remove("Message");

			if (schema.methods.Count != 0)
			{
				typeInfos = typeInfosByLayer[0];
				var ping = schema.methods.FirstOrDefault(m => m.method == "ping");
				if (ping != null)
				{
					var typeInfo = new TypeInfo { ReturnName = ping.type };
					typeInfo.Structs.Add(new Constructor { id = ping.id, @params = ping.@params, predicate = ping.method, type = ping.type });
					ctorToTypes[int.Parse(ping.id)] = CSharpName(ping.method);
					WriteTypeInfo(sw, typeInfo, "", false);
				}
				sw.WriteLine("}");
				sw.WriteLine("");
				sw.WriteLine("namespace WTelegram\t\t// ---functions---");
				sw.WriteLine("{");
				sw.WriteLine("\tusing System.IO;");
				sw.WriteLine("\tusing TL;");
				sw.WriteLine();
				sw.WriteLine("\tpublic partial class Client");
				//sw.WriteLine("\tpublic static partial class Fn // ---functions---");
				sw.Write("\t{");
				tabIndent = "\t\t";
				foreach (var method in schema.methods)
				{
					WriteMethod(sw, method);
					//var typeInfo = new TypeInfo { ReturnName = method.type };
					//typeInfo.Structs.Add(new Constructor { id = method.id, @params = method.@params, predicate = method.method, type = method.type });
					//methods.Add(typeInfo);
					//WriteTypeInfo(sw, typeInfo, "", true);
				}
				sw.WriteLine("\t}");
			}
			sw.WriteLine("}");

			if (tableCs != null) UpdateTable(tableCs);
		}

		void WriteTypeInfo(StreamWriter sw, TypeInfo typeInfo, string layerPrefix, bool isMethod)
		{
			var parentClass = typeInfo.NeedAbstract != 0 ? typeInfo.ReturnName : "ITLObject";
			var genericType = typeInfo.ReturnName.Length == 1 ? $"<{typeInfo.ReturnName}>" : null;
			if (isMethod) parentClass = "ITLFunction";
			bool needNewLine = true;
			if (typeInfo.NeedAbstract == -1 && allTypes.Add(layerPrefix + parentClass))
			{
				needNewLine = false;
				sw.WriteLine();
				if (currentJson != "TL.MTProto")
					sw.WriteLine($"{tabIndent}///<summary>See <a href=\"https://core.telegram.org/type/{typeInfo.Structs[0].type}\"/></summary>");
				sw.WriteLine($"{tabIndent}public abstract partial class {parentClass} : ITLObject {{ }}");
			}
			int skipParams = 0;
			foreach (var ctor in typeInfo.Structs)
			{
				string className = CSharpName(ctor.predicate) + genericType;
				//if (typeInfo.ReturnName == "SendMessageAction") System.Diagnostics.Debugger.Break();
				if (layerPrefix != "" && className == parentClass) { className += "_"; ctorToTypes[ctor.ID] = layerPrefix + className; }
				if (!allTypes.Add(layerPrefix + className)) continue;
				if (needNewLine) { needNewLine = false; sw.WriteLine(); }
				if (ctor.id == null)
				{
					if (currentJson != "TL.MTProto")
						sw.WriteLine($"{tabIndent}///<summary>See <a href=\"https://core.telegram.org/type/{typeInfo.Structs[0].type}\"/></summary>");
					sw.Write($"{tabIndent}public abstract partial class {className} : ITLObject");
				}
				else
				{
					if (currentJson != "TL.MTProto")
					{
						sw.WriteLine($"{tabIndent}///<summary>See <a href=\"https://core.telegram.org/constructor/{ctor.predicate}\"/></summary>");
						sw.WriteLine($"{tabIndent}[TLDef(0x{ctor.ID:X8})]");
					}
					else
					{
						sw.Write($"{tabIndent}[TLDef(0x{ctor.ID:X8})] //{ctor.predicate}#{ctor.ID:x8} ");
						if (genericType != null) sw.Write($"{{{typeInfo.ReturnName}:Type}} ");
						foreach (var parm in ctor.@params) sw.Write($"{parm.name}:{parm.type} ");
						sw.WriteLine($"= {ctor.type}");
					}
					sw.Write($"{tabIndent}public partial class {className} : ");
					sw.Write(skipParams == 0 && typeInfo.NeedAbstract > 0 ? "ITLObject" : parentClass);
				}
				var parms = ctor.@params.Skip(skipParams).ToArray();
				if (parms.Length == 0)
				{
					sw.WriteLine(" { }");
					continue;
				}
				var hasFlagEnum = parms.Any(p => p.type.StartsWith("flags."));
				bool multiline = hasFlagEnum || parms.Length > 1;
				if (multiline)
				{
					sw.WriteLine();
					sw.WriteLine(tabIndent + "{");
				}
				else
					sw.Write(" { ");
				if (hasFlagEnum)
				{
					var list = new SortedList<int, string>();
					foreach (var parm in parms)
					{
						if (!parm.type.StartsWith("flags.") || !parm.type.EndsWith("?true")) continue;
						var mask = 1 << int.Parse(parm.type[6..parm.type.IndexOf('?')]);
						if (!list.ContainsKey(mask)) list[mask] = MapName(parm.name);
					}
					foreach (var parm in parms)
					{
						if (!parm.type.StartsWith("flags.") || parm.type.EndsWith("?true")) continue;
						var mask = 1 << int.Parse(parm.type[6..parm.type.IndexOf('?')]);
						if (list.ContainsKey(mask)) continue;
						var name = MapName("has_" + parm.name);
						if (list.Values.Contains(name)) name += "_field";
						list[mask] = name;
					}
					string line = tabIndent + "\t[Flags] public enum Flags { ";
					foreach (var (mask, name) in list)
					{
						var str = $"{name} = 0x{mask:X}, ";
						if (line.Length + str.Length + tabIndent.Length * 3 >= 134) { sw.WriteLine(line); line = tabIndent + "\t\t"; }
						line += str;
					}
					sw.WriteLine(line.TrimEnd(',', ' ') + " }");
				}
				foreach (var parm in parms)
				{
					if (parm.type.EndsWith("?true")) continue;
					if (multiline) sw.Write(tabIndent + "\t");
					if (parm.type == "#")
						sw.Write($"public {(hasFlagEnum ? "Flags" : "int")} {parm.name};");
					else
					{
						if (parm.type.StartsWith("flags."))
						{
							int qm = parm.type.IndexOf('?');
							sw.Write($"[IfFlag({parm.type[6..qm]})] public {MapType(parm.type[(qm + 1)..], parm.name)} {MapName(parm.name)};");
						}
						else
							sw.Write($"public {MapType(parm.type, parm.name)} {MapName(parm.name)};");
					}
					if (multiline) sw.WriteLine();
				}

				if (multiline)
					sw.WriteLine(tabIndent + "}");
				else
					sw.WriteLine(" }");
				skipParams = typeInfo.NeedAbstract;
			}
		}

		private static string MapName(string name) => name switch
		{
			"out" => "out_",
			"static" => "static_",
			"long" => "long_",
			"default" => "default_",
			"public" => "public_",
			"params" => "params_",
			"private" => "private_",
			_ => name
		};

		private string MapType(string type, string name)
		{
			if (type.StartsWith("Vector<", StringComparison.OrdinalIgnoreCase))
				return MapType(type[7..^1], name) + "[]";
			else if (type == "Bool")
				return "bool";
			else if (type == "bytes")
				return "byte[]";
			else if (type == "int128")
				return "Int128";
			else if (type == "int256")
				return "Int256";
			else if (type == "Object")
				return "ITLObject";
			else if (type == "!X")
				return "ITLFunction";
			else if (typeInfos.TryGetValue(type, out var typeInfo))
				return typeInfo.ReturnName;
			else if (type == "int")
			{
				var name2 = '_' + name + '_';
				if (name2.EndsWith("_date_") || name2.EndsWith("_time_") || name2.StartsWith("_valid_") ||
					name2 == "_expires_" || name2 == "_expires_at_" || name2 == "_now_")
					return "DateTime";
				else
					return "int";
			}
			else if (type == "string")
				return name.StartsWith("md5") ? "byte[]" : "string";
			else
				return type;
		}

		private string MapOptionalType(string type, string name)
		{
			if (type == "Bool")
				return "bool?";
			else if (type == "long")
				return "long?";
			else if (type == "double")
				return "double?";
			else if (type == "int128")
				return "Int128?";
			else if (type == "int256")
				return "Int256?";
			else if (type == "int")
			{
				var name2 = '_' + name + '_';
				if (name2.EndsWith("_date_") || name2.EndsWith("_time_") || name2 == "_expires_" || name2 == "_now_" || name2.StartsWith("_valid_"))
					return "DateTime?";
				else
					return "int?";
			}
			else
				return MapType(type, name);
		}

		private void WriteMethod(StreamWriter sw, Method method)
		{
			int ctorNb = int.Parse(method.id);
			var funcName = CSharpName(method.method);
			string returnType = MapType(method.type, "");
			int style = knownStyles.GetValueOrDefault(funcName, 2);
			// styles: 0 = static string, 1 = static ITLFunction<>, 2 = Task<>, -1 = skip method
			if (style == -1) return;
			sw.WriteLine();

			var callAsync = "CallAsync";
			if (method.type.Length == 1 && style != 1) funcName += $"<{returnType}>";
			if (currentJson != "TL.MTProto")
				sw.WriteLine($"{tabIndent}///<summary>See <a href=\"https://core.telegram.org/method/{method.method}\"/></summary>");
			else
			{
				if (method.type is not "FutureSalts" and not "Pong") callAsync = "CallBareAsync";
				sw.Write($"{tabIndent}//{method.method}#{ctorNb:x8} ");
				if (method.type.Length == 1) sw.Write($"{{{method.type}:Type}} ");
				foreach (var parm in method.@params) sw.Write($"{parm.name}:{parm.type} ");
				sw.WriteLine($"= {method.type}");
			}

			if (style == 0) sw.WriteLine($"{tabIndent}public Task<{returnType}> {funcName}() => {callAsync}<{returnType}>({funcName});");
			if (style == 0) sw.Write($"{tabIndent}public static string {funcName}(BinaryWriter writer");
			if (style == 1) sw.Write($"{tabIndent}public static ITLFunction {funcName}(");
			if (style == 2) sw.Write($"{tabIndent}public Task<{returnType}> {funcName}(");
			bool first = style != 0;
			foreach (var parm in method.@params) // output non-optional parameters
			{
				if (parm.type == "#" || parm.type.StartsWith("flags.")) continue;
				if (first) first = false; else sw.Write(", ");
				sw.Write($"{MapType(parm.type, parm.name)} {MapName(parm.name)}");
			}
			string flagExpr = null;
			foreach (var parm in method.@params) // output optional parameters
			{
				if (!parm.type.StartsWith("flags.")) continue;
				var parmName = MapName(parm.name);
				int qm = parm.type.IndexOf('?');
				int bit = int.Parse(parm.type[6..qm]);
				if (first) first = false; else sw.Write(", ");
				if (parm.type.EndsWith("?true"))
				{
					sw.Write($"bool {parmName} = false");
					flagExpr += $" | ({parmName} ? 0x{1 << bit:X} : 0)";
				}
				else
				{
					sw.Write($"{MapOptionalType(parm.type[(qm + 1)..], parm.name)} {parmName} = null");
					flagExpr += $" | ({parmName} != null ? 0x{1 << bit:X} : 0)";
				}
			}
			if (flagExpr != null) flagExpr = flagExpr.IndexOf('|', 3) >= 0 ? flagExpr[3..] : flagExpr[4..^1];
			sw.WriteLine(")");
			if (style != 0) tabIndent += "\t";
			if (style == 1) sw.WriteLine($"{tabIndent}=> writer =>");
			if (style == 2) sw.WriteLine($"{tabIndent}=> {callAsync}<{returnType}>(writer =>");
			sw.WriteLine(tabIndent + "{");
			sw.WriteLine($"{tabIndent}\twriter.Write(0x{ctorNb:X8});");
			foreach (var parm in method.@params) // serialize request
			{
				var parmName = MapName(parm.name);
				var parmType = parm.type;
				if (parmType.StartsWith("flags."))
				{
					if (parmType.EndsWith("?true")) continue;
					int qm = parmType.IndexOf('?');
					parmType = parmType[(qm + 1)..];
					sw.WriteLine($"{tabIndent}\tif ({parmName} != null)");
					sw.Write('\t');
					if (MapOptionalType(parmType, parm.name).EndsWith("?"))
						parmName += ".Value";
				}
				switch (parmType)
				{
					case "Bool":
						sw.WriteLine($"{tabIndent}\twriter.Write({parmName} ? 0x997275B5 : 0xBC799737);");
						break;
					case "bytes":
						sw.WriteLine($"{tabIndent}\twriter.WriteTLBytes({parmName});");
						break;
					case "long": case "int128": case "int256": case "double":
						sw.WriteLine($"{tabIndent}\twriter.Write({parmName});");
						break;
					case "int":
						if (MapType(parmType, parm.name) == "int")
							sw.WriteLine($"{tabIndent}\twriter.Write({parmName});");
						else
							sw.WriteLine($"{tabIndent}\twriter.WriteTLStamp({parmName});");
						break;
					case "string":
						if (parm.name.StartsWith("md5"))
							sw.WriteLine($"{tabIndent}\twriter.WriteTLBytes({parmName});");
						else
							sw.WriteLine($"{tabIndent}\twriter.WriteTLString({parmName});");
						break;
					case "#":
						sw.WriteLine($"{tabIndent}\twriter.Write({flagExpr});");
						break;
					case "!X":
						sw.WriteLine($"{tabIndent}\t{parmName}(writer);");
						break;
					default:
						if (parmType.StartsWith("Vector<", StringComparison.OrdinalIgnoreCase))
							sw.WriteLine($"{tabIndent}\twriter.WriteTLVector({parmName});");
						else
							sw.WriteLine($"{tabIndent}\twriter.WriteTLObject({parmName});");
						break;
				}
			}
			sw.WriteLine($"{tabIndent}\treturn \"{funcName}\";");
			if (style == 0) sw.WriteLine(tabIndent + "}");
			if (style == 1) sw.WriteLine(tabIndent + "};");
			if (style == 2) sw.WriteLine(tabIndent + "});");
			if (style != 0) tabIndent = tabIndent[0..^1];
		}

		void UpdateTable(string tableCs)
		{
			var myTag = $"\t\t\t// from {currentJson}:";
			var seen_ids = new HashSet<int>();
			using (var sr = new StreamReader(tableCs))
			using (var sw = new StreamWriter(tableCs + ".new"))
			{
				string line;
				while ((line = sr.ReadLine()) != null)
				{
					if (currentLayer != 0 && line.StartsWith("\t\tpublic const int Layer"))
						sw.WriteLine($"\t\tpublic const int Layer = {currentLayer};\t\t\t\t\t// fetched {DateTime.UtcNow}");
					else
						sw.WriteLine(line);
					if (line == myTag)
					{
						foreach (var ctor in ctorToTypes)
							if (seen_ids.Add(ctor.Key))
								sw.WriteLine($"\t\t\t[0x{ctor.Key:X8}] = typeof({ctor.Value}),");
						while ((line = sr.ReadLine()) != null)
							if (line.StartsWith("\t\t\t// "))
								break;
						sw.WriteLine(line);
					}
					else if (line.StartsWith("\t\t\t[0x"))
						seen_ids.Add(int.Parse(line[6..14], System.Globalization.NumberStyles.HexNumber));
				}
			}
			File.Replace(tableCs + ".new", tableCs, null);
		}

		private static bool HasPrefix(Constructor ctor, IList<Param> prefixParams)
		{
			if (ctor.@params.Length < prefixParams.Count) return false;
			for (int i = 0; i < prefixParams.Count; i++)
				if (ctor.@params[i].name != prefixParams[i].name || ctor.@params[i].type != prefixParams[i].type)
					return false;
			return true;
		}

		private static string CSharpName(string name)
		{
			name = char.ToUpper(name[0]) + name[1..];
			int i;
			while ((i = name.IndexOf('_')) > 0)
				name = name[..i] + char.ToUpper(name[i + 1]) + name[(i + 2)..];
			while ((i = name.IndexOf('.')) > 0)
				name = name[..i] + '_' + char.ToUpper(name[i + 1]) + name[(i + 2)..];
			return name;
		}

		class TypeInfo
		{
			public string ReturnName;
			public Constructor SameName;
			public List<Constructor> Structs = new();
			internal int NeedAbstract; // 0:no, -1:create auto, n:use first generated constructor and skip n params
		}

#pragma warning disable IDE1006 // Naming Styles
		public class SchemaJson
		{
			public List<Constructor> constructors { get; set; }
			public List<Method> methods { get; set; }
		}

		public class Constructor
		{
			public string id { get; set; }
			public string predicate { get; set; }
			public Param[] @params { get; set; }
			public string type { get; set; }
			public int layer { get; set; }

			public int ID => int.Parse(id);
		}

		public class Param
		{
			public string name { get; set; }
			public string type { get; set; }
		}

		public class Method
		{
			public string id { get; set; }
			public string method { get; set; }
			public Param[] @params { get; set; }
			public string type { get; set; }
		}
#pragma warning restore IDE1006 // Naming Styles
	}
}