using KumiScript.Reader;

namespace KumiScript.Interpreter
{
    public class MathPrimitives
    {
        public static NumberExpression Plus(Expression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            decimal acc = 0;
            for (int i = 0; i < argl.Count; i++)
            {
                acc += argl[i].GetValueAsFloat();
            }

            return new NumberExpression(acc);
        }

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

            decimal acc = argl[0].GetValueAsFloat();
            if (argl.Count == 1)
                return new NumberExpression(1 - acc);
            
            for (int i = 1; i < argl.Count; i++)
            {
                acc -= argl[i].GetValueAsFloat();
            }
            return new NumberExpression(acc);
        }

        public static NumberExpression Times(Expression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count < 2)
                throw new InterpreterInvalidInvocationException();
            
            decimal f = argl[0].GetValueAsFloat();
            for (int i = 1; i < argl.Count; i++)
            {
                f *= argl[i].GetValueAsFloat();
            }
            return new NumberExpression(f);
        }

        public static NumberExpression DividedBy(Expression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            return new NumberExpression(argl[0].GetValueAsFloat() / argl[1].GetValueAsFloat());
        }

        public static NumberExpression Modulus(Expression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            return new NumberExpression(argl[0].GetValueAsFloat() % argl[1].GetValueAsFloat());
        }

        public static Expression GreaterThan(Expression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            return argl[0].GetValueAsFloat() > argl[1].GetValueAsFloat() ? TrueExpression.GetInstance() : NilExpression.GetInstance();
        }
        public static Expression LessThan(Expression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            return argl[0].GetValueAsFloat() < argl[1].GetValueAsFloat() ? TrueExpression.GetInstance() : NilExpression.GetInstance();
        }

        public static Expression LessThanEquals(Expression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            return argl[0].GetValueAsFloat() <= argl[1].GetValueAsFloat() ? TrueExpression.GetInstance() : NilExpression.GetInstance();
        }

        public static Expression GreaterThanEquals(Expression args, Environment env)
        {
            List<Expression> argl = args.EvalMembers(env);
            if (argl.Count != 2)
                throw new InterpreterInvalidApplicationException();
            
            return argl[0].GetValueAsFloat() >= argl[1].GetValueAsFloat() ? TrueExpression.GetInstance() : NilExpression.GetInstance();
        }

        public static Expression PlusPlus(Expression args, Environment env)
        {
            List<Expression> argl = args.GetMembers();
            if (argl.Count != 1)
                throw new InterpreterInvalidApplicationException();
            
            Symbol name = argl[0].GetSymbol();
            Expression val = env.Lookup(name);
            NumberExpression nump = new NumberExpression(val.GetValueAsFloat() + 1);
            env.RedefineSymbol(name, nump);
            return nump;
        }

        public static Expression MinusMinus(Expression args, Environment env)
        {
            List<Expression> argl = args.GetMembers();
            if (argl.Count != 1)
                throw new InterpreterInvalidApplicationException();
            
            Symbol name = argl[0].GetSymbol();
            Expression val = env.Lookup(name);
            NumberExpression nump = new NumberExpression(val.GetValueAsFloat() - 1);
            env.RedefineSymbol(name, nump);
            return nump;
        }

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