using System.Reflection.Metadata.Ecma335;

namespace KumiScript.Interpreter
{
    public class MathPrimitives
    {
        public static NumberExpression Plus(ListExpression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            decimal acc = 0;
            for (int i = 0; i < argl.Count; i++)
            {
                NumberExpression? argin = argl[i] as NumberExpression;
                if (argin is null)
                    throw new InterpreterTypingException();

                acc += argin.GetValueAsFloat();
            }

            return NumberFactory.NormalizeFloat(acc);
        }

        public static NumberExpression Minus(ListExpression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count == 0)
                throw new InterpreterInvalidApplicationException();

            NumberExpression? argn0 = argl[0] as NumberExpression;
            if (argn0 is null)
                throw new InterpreterTypingException();

            decimal acc = argn0.GetValueAsFloat();
            if (argl.Count == 1)
                return NumberFactory.NormalizeFloat(1 - acc);
            
            for (int i = 1; i < argl.Count; i++)
            {
                NumberExpression? argin = argl[i] as NumberExpression;
                if (argin is null)
                    throw new InterpreterTypingException();
                
                acc -= argin.GetValueAsFloat();
            }
            return NumberFactory.NormalizeFloat(acc);
        }

        public static NumberExpression Times(ListExpression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count < 2)
                throw new InterpreterInvalidInvocationException();
            
            NumberExpression? arg0 = argl[0] as NumberExpression;
            if (arg0 is null)
                throw new InterpreterTypingException();

            decimal f = arg0.GetValueAsFloat();
            for (int i = 1; i < argl.Count; i++)
            {
                NumberExpression? argn = argl[i] as NumberExpression;
                if (argn is null)
                    throw new InterpreterTypingException();
                
                f *= argn.GetValueAsFloat();
            }
            return NumberFactory.NormalizeFloat(f);
        }

        public static NumberExpression DividedBy(ListExpression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();

            NumberExpression? arg0 = argl[0] as NumberExpression;
            if (arg0 is null)
                throw new InterpreterTypingException();

            NumberExpression? arg1 = argl[1] as NumberExpression;
            if (arg1 is null)
                throw new InterpreterTypingException();
            
            return NumberFactory.NormalizeFloat(arg0.GetValueAsFloat() / arg1.GetValueAsFloat());
        }

        public static NumberExpression Modulus(ListExpression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();

            NumberExpression? arg0 = argl[0] as NumberExpression;
            if (arg0 is null)
                throw new InterpreterTypingException();

            NumberExpression? arg1 = argl[1] as NumberExpression;
            if (arg1 is null)
                throw new InterpreterTypingException();
            
            return NumberFactory.NormalizeFloat(arg0.GetValueAsFloat() % arg1.GetValueAsFloat());
        }

        public static Expression GreaterThan(ListExpression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            NumberExpression? arg0 = argl[0] as NumberExpression;
            if (arg0 is null)
                throw new InterpreterTypingException();

            NumberExpression? arg1 = argl[1] as NumberExpression;
            if (arg1 is null)
                throw new InterpreterTypingException();

            return arg0.GetValueAsFloat() > arg1.GetValueAsFloat() ? TrueExpression.GetInstance() : NilExpression.GetInstance();
        }
        public static Expression LessThan(ListExpression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            NumberExpression? arg0 = argl[0] as NumberExpression;
            if (arg0 is null)
                throw new InterpreterTypingException();

            NumberExpression? arg1 = argl[1] as NumberExpression;
            if (arg1 is null)
                throw new InterpreterTypingException();

            return arg0.GetValueAsFloat() < arg1.GetValueAsFloat() ? TrueExpression.GetInstance() : NilExpression.GetInstance();
        }

        public static Expression LessThanEquals(ListExpression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            NumberExpression? arg0 = argl[0] as NumberExpression;
            if (arg0 is null)
                throw new InterpreterTypingException();

            NumberExpression? arg1 = argl[1] as NumberExpression;
            if (arg1 is null)
                throw new InterpreterTypingException();

            return arg0.GetValueAsFloat() <= arg1.GetValueAsFloat() ? TrueExpression.GetInstance() : NilExpression.GetInstance();
        }

        public static Expression GreaterThanEquals(ListExpression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            NumberExpression? arg0 = argl[0] as NumberExpression;
            if (arg0 is null)
                throw new InterpreterTypingException();

            NumberExpression? arg1 = argl[1] as NumberExpression;
            if (arg1 is null)
                throw new InterpreterTypingException();

            return arg0.GetValueAsFloat() >= arg1.GetValueAsFloat() ? TrueExpression.GetInstance() : NilExpression.GetInstance();
        }

        public static Expression PlusPlus(ListExpression args, Environment env)
        {
            List<Expression> argl = args.GetMembers();
            if (argl.Count != 1)
                throw new InterpreterInvalidApplicationException();
            
            SymbolExpression? binding = argl[0] as SymbolExpression;
            if (binding is null)
                throw new InterpreterTypingException();

            Symbol name = binding.GetSymbol();
            Expression val = env.Lookup(name);
            NumberExpression? num = val as NumberExpression;
            if (num is null)
                throw new InterpreterTypingException();
            
            NumberExpression nump = NumberFactory.NormalizeFloat(num.GetValueAsFloat() + 1);
            env.RedefineSymbol(name, nump);
            return nump;
        }

        public static Expression MinusMinus(ListExpression args, Environment env)
        {
            List<Expression> argl = args.GetMembers();
            if (argl.Count != 1)
                throw new InterpreterInvalidApplicationException();
            
            SymbolExpression? binding = argl[0] as SymbolExpression;
            if (binding is null)
                throw new InterpreterTypingException();

            Symbol name = binding.GetSymbol();
            Expression val = env.Lookup(name);
            NumberExpression? num = val as NumberExpression;
            if (num is null)
                throw new InterpreterTypingException();
            
            NumberExpression nump = NumberFactory.NormalizeFloat(num.GetValueAsFloat() - 1);
            env.RedefineSymbol(name, nump);
            return nump;
        }

        public static Environment RegisterPrimitives(Environment outer)
        {
            Environment result = new Environment(outer);
            result.AddSymbol(new Symbol("+"), new ProcedureExpression(new PrimitiveProcedure(Plus)));
            result.AddSymbol(new Symbol("-"), new ProcedureExpression(new PrimitiveProcedure(Minus)));
            result.AddSymbol(new Symbol("*"), new ProcedureExpression(new PrimitiveProcedure(Times)));
            result.AddSymbol(new Symbol("/"), new ProcedureExpression(new PrimitiveProcedure(DividedBy)));
            result.AddSymbol(new Symbol("%"), new ProcedureExpression(new PrimitiveProcedure(Modulus)));
            result.AddSymbol(new Symbol(">"), new ProcedureExpression(new PrimitiveProcedure(GreaterThan)));
            result.AddSymbol(new Symbol("<"), new ProcedureExpression(new PrimitiveProcedure(LessThan)));
            result.AddSymbol(new Symbol("<="), new ProcedureExpression(new PrimitiveProcedure(LessThanEquals)));
            result.AddSymbol(new Symbol(">="), new ProcedureExpression(new PrimitiveProcedure(GreaterThanEquals)));
            result.AddSymbol(new Symbol("++!"), new ProcedureExpression(new PrimitiveProcedure(PlusPlus)));
            result.AddSymbol(new Symbol("--!"), new ProcedureExpression(new PrimitiveProcedure(MinusMinus)));
            return result;
        }
    }
}