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

class Program {
    static int Main(string[] args) {
        if (args.Length < 1) {
            Console.WriteLine("Usage: StSim <file.stbc>");
            return 1;
        }
        var path = args[0];
        if (!File.Exists(path)) { Console.WriteLine("File not found: " + path); return 2; }
        var data = File.ReadAllBytes(path);
        try { Simulate(data); } catch(Exception ex) { Console.WriteLine("Error: " + ex.Message); return 3; }
        return 0;
    }

    static void Simulate(byte[] data) {
        using var ms = new MemoryStream(data);
        using var r = new BinaryReader(ms);

        string magic = System.Text.Encoding.ASCII.GetString(r.ReadBytes(4));
        if (magic != Bytecode.Magic) throw new Exception("Invalid magic");
        ushort ver = r.ReadUInt16();
        if (ver != Bytecode.Version) throw new Exception($"Unsupported version {ver}");

        ushort nConsts = r.ReadUInt16();
        var consts = new List<object>();
        for (int i = 0; i < nConsts; i++) {
            byte t = r.ReadByte();
            switch(t) {
                case 1: consts.Add(r.ReadInt64()); break;
                case 2: consts.Add(r.ReadDouble()); break;
                case 3: consts.Add(r.ReadSingle()); break;
                case 4: consts.Add(r.ReadInt32()); break;
                default: throw new Exception($"Unknown const type {t}");
            }
        }

        ushort nVars = r.ReadUInt16();
        var varTypes = new VarType[nVars];
        for (int i = 0; i < nVars; i++) varTypes[i] = (VarType)r.ReadByte();

        ushort codeLen = r.ReadUInt16();
        var code = r.ReadBytes(codeLen);

        var stack = new Stack<object>();
        var vars = new object[nVars];
        int ip = 0;
        while (ip < code.Length) {
            byte op = code[ip++];
            switch(op) {
                case Bytecode.OpCodes.NOP: break;
                case Bytecode.OpCodes.PUSH_CONST: {
                    ushort ci = (ushort)(code[ip++] | (code[ip++] << 8));
                    stack.Push(consts[ci]);
                    break;
                }
                case Bytecode.OpCodes.PUSH_REAL_CONST: {
                    ushort ci = (ushort)(code[ip++] | (code[ip++] << 8));
                    stack.Push(consts[ci]);
                    break;
                }
                case Bytecode.OpCodes.LOAD_VAR: {
                    ushort vi = (ushort)(code[ip++] | (code[ip++] << 8));
                    stack.Push(vars[vi]);
                    break;
                }
                case Bytecode.OpCodes.STORE_VAR: {
                    ushort vi = (ushort)(code[ip++] | (code[ip++] << 8));
                    vars[vi] = stack.Pop();
                    break;
                }
                case Bytecode.OpCodes.JZ: {
                    ushort target = (ushort)(code[ip++] | (code[ip++] << 8));
                    var cond = stack.Pop();
                    bool isFalse = cond is int ci ? ci == 0 : cond is long cl ? cl == 0L : cond is double cd ? cd == 0.0 : cond == null;
                    if (isFalse) ip = target;
                    break;
                }
                case Bytecode.OpCodes.JMP: {
                    ushort target = (ushort)(code[ip++] | (code[ip++] << 8));
                    ip = target;
                    break;
                }
                case Bytecode.OpCodes.HALT:
                    Console.WriteLine("HALT");
                    return;
                default:
                    // Simple arithmetic handlers for some opcodes
                    if (Bytecode.OpName(op).StartsWith("ADD_")) {
                        dynamic b = stack.Pop(); dynamic a = stack.Pop(); stack.Push(a + b); break;
                    }
                    if (Bytecode.OpName(op).StartsWith("SUB_")) {
                        dynamic b = stack.Pop(); dynamic a = stack.Pop(); stack.Push(a - b); break;
                    }
                    if (Bytecode.OpName(op).StartsWith("MUL_")) {
                        dynamic b = stack.Pop(); dynamic a = stack.Pop(); stack.Push(a * b); break;
                    }
                    if (Bytecode.OpName(op).StartsWith("DIV_")) {
                        dynamic b = stack.Pop(); dynamic a = stack.Pop(); stack.Push(a / b); break;
                    }
                    if (Bytecode.OpName(op).StartsWith("LT_") || Bytecode.OpName(op).StartsWith("GT_") || Bytecode.OpName(op).StartsWith("LE_") || Bytecode.OpName(op).StartsWith("GE_") || Bytecode.OpName(op).StartsWith("EQ_") || Bytecode.OpName(op).StartsWith("NEQ_")) {
                        // comparisons: pop r, pop l, push int 0/1
                        dynamic rVal = stack.Pop(); dynamic lVal = stack.Pop();
                        bool res = Bytecode.OpName(op).StartsWith("LT_") ? (lVal < rVal) :
                                   Bytecode.OpName(op).StartsWith("GT_") ? (lVal > rVal) :
                                   Bytecode.OpName(op).StartsWith("LE_") ? (lVal <= rVal) :
                                   Bytecode.OpName(op).StartsWith("GE_") ? (lVal >= rVal) :
                                   Bytecode.OpName(op).StartsWith("EQ_") ? (lVal == rVal) :
                                   (lVal != rVal);
                        stack.Push(res ? 1 : 0);
                        break;
                    }
                    throw new Exception($"Unknown opcode 0x{op:X2}");
            }
        }

        Console.WriteLine("Execution finished");
        for (int i = 0; i < vars.Length; i++) Console.WriteLine($"Var[{i}] = {vars[i]}");
    }
}