package Torello.JSON;

import Torello.Java.Function.FloatConsumer;

import java.util.function.IntConsumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.DoubleConsumer;
import java.util.function.ObjIntConsumer;

import java.math.BigDecimal;

import javax.json.JsonNumber;

import static javax.json.JsonValue.ValueType.NUMBER;


// This class in invoked ONLY once.  The SettingsRec<T, U> Constructor calls it.
// Once this class a returned a "Json-Number Handler", only the selected handler
// itself will ever be invoked during the Main-Loop-Processing
// 
// Though this may look like the most ascinine thing that has ever been written
// in Java.  Over a period of three years it has, indeed, been testing and retested
// to the point of being extremely feasible.
//
// All this class does is generate an "Object-Int-Consumer".
// This "Consumer" is just a method that accepts:
// 
// 1) JsonNumber
// 2) Array-Index as an Integer (the 'int i' you see in the Lambda-Expressions)
// 
// All this conumer does is generate a Valid Java-Number, and insert it into the
// user's consumer.  If the user has actually requested a "Stream<SomeNumberType>",
// Then the Stream.Builder<SomeType> is converted into a consumer and used by the
// Lambda's inside this method.
// 
// 
// *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
// The 'ja' instance declared in class "SettingsRec" **IS NOT** declared final.  It can be reset !
// *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
// 
// IMPORTANT NOTE: The 'ja' that is passed to the Functional-Interface Implementatons which are 
// constructed in this method is "de-referenced" from the SettingsRec -- It **IS NOT** passed as
// a parameter to this method.  If it **WERE NOT** retrieved from the 'SettingsRec', then 'sr'
// instance, then the 'ja' that would be used would be permanently-solidified to the 'ja' 
// referenced that were passed right at the beginning, upon construction of the SettingsRec
// instance.

@Torello.JavaDoc.Annotations.StaticFunctional
public class ChooseNumberHandler
{
    private ChooseNumberHandler() {}


    // handlerNumber: **ONLY USED BY** ProcessJsonArray.numericToJava
    // 
    // This makes the method ProcessJsonArray.numericJsonArrayTo look a million times better
    // It is also slightly more efficient this way... slightly - since the 'if-statements'
    // are "outside" of the lambda's, not inside.

    @SuppressWarnings({"unchecked"})
    // Consumer<Number> c = (Consumer<Number>) this.acceptor;
    static <T> ObjIntConsumer<JsonNumber> choose(
            final SettingsRec<T, ?> sr,
            final ACCEPTOR<T>       acceptor,
            final byte              whichType,

            // BASIC_TYPES: bt.whichType,
            final boolean refOrPrim,

            // BASIC_TYPES: bt.referenceOrPrimitive,
            final Function<Number, T> numberConverter,

            // BASIC_TYPES: bt.numberConverter,
            final Function<BigDecimal, T> numberConverterExThrow,

            // BASIC_TYPES: bt.jsonNumWillFit
            final Predicate<JsonNumber> jsonNumWillFit,

            // BASIC_TYPES: bt.numberConverterExThrow,
            final boolean RJA_AEX,

            final IntConsumer handlerAEX
        )
    {
        // The Type-Checking Downside... There is no way I can 'prove' that this
        // Consumer *REALLY* is a 'Number' consumer... but it must be!

        if (whichType == BASIC_TYPES.NUMBER) return (JsonNumber jn, int i) -> 
            ((ACCEPTOR<Number>) acceptor).accept(ReadNumberJSON.convertToNumber(jn), i);

        else if (RJA_AEX)
            return (JsonNumber jn, int i) ->
                acceptor.accept(numberConverter.apply(jn.numberValue()), i);

        else if (handlerAEX == null)
        {
            if (whichType == BASIC_TYPES.FLOAT) return (JsonNumber jn, int i) ->
            {
                // IMPORTANT NOTE: See the comment at the top of this class regarding the 'sr.ja'
                // versus 'ja' (being passed as a parameter to this method).

                if (! handleFloat(acceptor, jn, i)) throw new JsonArithmeticArrException(
                    ChooseNumberHandler.getAEX(jn, numberConverterExThrow),
                    sr.ja, i, NUMBER, /* used to be 'jv' */ jn, sr.CLASS
                );
            };

            else if (whichType == BASIC_TYPES.DOUBLE) return (JsonNumber jn, int i) ->
            {
                // IMPORTANT NOTE: See the comment at the top of this class regarding the 'sr.ja'
                // versus 'ja' (being passed as a parameter to this method).

                if (! handleDouble(acceptor, jn, i)) throw new JsonArithmeticArrException(
                    ChooseNumberHandler.getAEX(jn, numberConverterExThrow),
                    sr.ja, i, NUMBER, jn, sr.CLASS
                );
            };

            else return (JsonNumber jn, int i) ->
            {
                if (jsonNumWillFit.test(jn))
                    acceptor.accept(numberConverter.apply(jn.numberValue()), i);


                // IMPORTANT NOTE: See the comment at the top of this class regarding the 'sr.ja'
                // versus 'ja' (being passed as a parameter to this method).

                else throw new JsonArithmeticArrException(
                    ChooseNumberHandler.getAEX(jn, numberConverterExThrow),
                    sr.ja, i, NUMBER, /* used to be 'jv' */ jn, sr.CLASS
                );
            };
        }

        else 
        {
            if (whichType == BASIC_TYPES.FLOAT) return (JsonNumber jn, int i) ->
            { if (! handleFloat(acceptor, jn, i)) handlerAEX.accept(i); };

            else if (whichType == BASIC_TYPES.DOUBLE) return (JsonNumber jn, int i) ->
            { if (! handleDouble(acceptor, jn, i)) handlerAEX.accept(i); };

            else return (JsonNumber jn, int i) ->
            {
                if (jsonNumWillFit.test(jn))
                    acceptor.accept(numberConverter.apply(jn.numberValue()), i);
                else 
                    handlerAEX.accept(i);
            };
        }
    }


    // As a part of the Java-HTML experience is the need to make sure that the types
    // which are converted do not accidentally do any "rounding" or "truncation" unless the user 
    // has explicitly requested it.
    // 
    // This method simply puts a JsonNumber into a Double-Consumer....
    // **HOWEVER** It checks that no rounding & truncation is necesary before doing this.
    // 
    // NOTE: The Class "PREDICATES" hasL
    //  * shortTypePred
    //  * longTypePred
    //  * byteTypePred
    // 
    // Note that the *ONLY WAY* to actually check if the `BigDecimal.doubleValue` is actually 
    // returning a number that has been properly fit into a Valid Double-Value is to go ahead and
    // generate the `Double`, and the check (using the static BigDecimal.valueOf(d) Method) to 
    // convert it *BACK INTO A BigDecimal INSTANCE*.
    // 
    // As a Result, since the 'double' is generated during the processing of checking whether the
    // double is a Valid-Conversion or not, it would be somewhat inefficient to do this conversion
    // **TWICE** - Once in the class PREDICATES, and then a Second-Time (dircectly) above in the 
    // 'choose(..)' method.

    @SuppressWarnings({"rawtypes", "unchecked"})
    private static boolean handleDouble
        (final ACCEPTOR acceptor, final JsonNumber jn, final int i)
    {
        final BigDecimal    bd  = jn.bigDecimalValue();
        final double        d   = bd.doubleValue();

        if ((!Double.isInfinite(d)) && BigDecimal.valueOf(d).compareTo(bd) == 0)
        {
            ((ACCEPTOR<Double>) acceptor).accept(d, i);
            return true;
        }

        return false;
    }

    // Same as above, but for Float's instead of Double's.
    @SuppressWarnings({"rawtypes", "unchecked"})
    private static boolean handleFloat
        (final ACCEPTOR acceptor, final JsonNumber jn, final int i)
    {
        final BigDecimal    bd = jn.bigDecimalValue();
        final float         f   = bd.floatValue();

        if ((!Float.isInfinite(f)) && BigDecimal.valueOf(f).compareTo(bd) == 0)
        {
            ((ACCEPTOR<Float>) acceptor).accept(f, i);
            return true;
        }

        return false;
    }

    // NOTE: It is **A LOT** Smarter to check for the exception instead of using the try-catch
    //       since I have read that generating an exception is one of the most costly-expensive
    //       things the JRE does.  It isn't the Exception-Constructor that costs a lot - it is the
    //       creating of the **STACK-TRACE** that costs well over 100 to 1,000 times the number of
    //       of CPU-Cycles that the cost of a simple constructor.  This is an "Only if abolutely"
    //       necessary things.

    private static <T extends Number> ArithmeticException getAEX
        (JsonNumber jn, Function<BigDecimal, ?> converter)
    {
        try
            { converter.apply(jn.bigDecimalValue()); }

        catch (ArithmeticException aex)
            { return aex; }

        throw new Torello.Java.UnreachableError();
    }
}