package org.jruby.runtime.scope;

import org.jruby.parser.StaticScope;
import org.jruby.runtime.DynamicScope;
import org.jruby.runtime.builtin.IRubyObject;
import org.jruby.util.ArraySupport;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;

Represents the the dynamic portion of scoping information.  The variableValues are the
values of assigned local or block variables.  The staticScope identifies which sort of
scope this is (block or local).
Properties of Dynamic Scopes:
1. static and dynamic scopes have the same number of names to values
2. size of variables (and thus names) is determined during parsing.  So those structured do
   not need to change
FIXME: When creating dynamic scopes we sometimes accidentally pass in extra parents.  This
is harmless (other than wasting memory), but we should not do that.  We can fix this in two
ways:
1. Fix all callers
2. Check parent that is passed in and make if new instance is local, then its parent is not local
/**
 * Represents the the dynamic portion of scoping information.  The variableValues are the
 * values of assigned local or block variables.  The staticScope identifies which sort of
 * scope this is (block or local).
 * 
 * Properties of Dynamic Scopes:
 * 1. static and dynamic scopes have the same number of names to values
 * 2. size of variables (and thus names) is determined during parsing.  So those structured do
 *    not need to change
 *
 * FIXME: When creating dynamic scopes we sometimes accidentally pass in extra parents.  This
 * is harmless (other than wasting memory), but we should not do that.  We can fix this in two
 * ways:
 * 1. Fix all callers
 * 2. Check parent that is passed in and make if new instance is local, then its parent is not local
 */
public class ManyVarsDynamicScope extends DynamicScope {
    // Our values holder (name of variables are kept in staticScope)
    private IRubyObject[] variableValues;

    public static final MethodHandle CONSTRUCTOR;
    static {
        try {
            // use lookup() to avoid IllegalAccessException with JRuby embed
            CONSTRUCTOR = MethodHandles.lookup()
                    .findConstructor(ManyVarsDynamicScope.class, MethodType.methodType(void.class, StaticScope.class, DynamicScope.class))
                    .asType(MethodType.methodType(DynamicScope.class, StaticScope.class, DynamicScope.class));
        } catch (Exception e) {
            throw new RuntimeException("BUG: could not initialize constructor handle", e);
        }
    }

    public ManyVarsDynamicScope(StaticScope staticScope, DynamicScope parent) {
        super(staticScope, parent);
        allocate();
    }

    private void allocate() {
        if(variableValues == null) variableValues = IRubyObject.array(staticScope.getNumberOfVariables());
    }

    public IRubyObject[] getValues() {
        return variableValues;
    }
    
    
Get value from current scope or one of its captured scopes.
FIXME: block variables are not getting primed to nil so we need to null check those
 until we prime them properly.  Also add assert back in.
Params:
offset – zero-indexed value that represents where variable lives
depth – how many captured scopes down this variable should be set
Returns:
the value here/**
     * Get value from current scope or one of its captured scopes.
     * 
     * FIXME: block variables are not getting primed to nil so we need to null check those
     *  until we prime them properly.  Also add assert back in.
     * 
     * @param offset zero-indexed value that represents where variable lives
     * @param depth how many captured scopes down this variable should be set
     * @return the value here
     */
    public IRubyObject getValue(int offset, int depth) {
        if (depth > 0) {
            return parent.getValue(offset, depth - 1);
        }

        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, offset) : failGet(this, offset, depth);

        return variableValues[offset];
    }

    public IRubyObject getValueDepthZero(int offset) {
        return variableValues[offset];
    }

    public IRubyObject getValueZeroDepthZero() {
        return variableValues[0];
    }

    public IRubyObject getValueOneDepthZero() {
        return variableValues[1];
    }

    public IRubyObject getValueTwoDepthZero() {
        return variableValues[2];
    }

    public IRubyObject getValueThreeDepthZero() {
        return variableValues[3];
    }
    
    
Variation of getValue that checks for nulls, returning and setting the given value (presumably nil)
/**
     * Variation of getValue that checks for nulls, returning and setting the given value (presumably nil)
     */
    public IRubyObject getValueOrNil(int offset, int depth, IRubyObject nil) {
        if (depth > 0) {
            return parent.getValueOrNil(offset, depth - 1, nil);
        } else {
            return getValueDepthZeroOrNil(offset, nil);
        }
    }
    
    public IRubyObject getValueDepthZeroOrNil(int offset, IRubyObject nil) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, offset) : failGet(this, offset);

        IRubyObject value = variableValues[offset];
        return value == null ? setValueDepthZero(nil, offset) : value;
    }

    public IRubyObject getValueZeroDepthZeroOrNil(IRubyObject nil) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 0) : failGet(this, 0);

        IRubyObject value = variableValues[0];
        return value == null ? setValueZeroDepthZero(nil) : value;
    }
    
    public IRubyObject getValueOneDepthZeroOrNil(IRubyObject nil) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 1) : failGet(this, 1);

        IRubyObject value = variableValues[1];
        return value == null ? setValueOneDepthZero(nil) : value;
    }
    
    public IRubyObject getValueTwoDepthZeroOrNil(IRubyObject nil) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 2) : failGet(this, 2);

        IRubyObject value = variableValues[2];
        return value == null ? setValueTwoDepthZero(nil) : value;
    }
    
    public IRubyObject getValueThreeDepthZeroOrNil(IRubyObject nil) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 3) : failGet(this, 3);

        IRubyObject value = variableValues[3];
        return value == null ? setValueThreeDepthZero(nil) : value;
    }

    
Set value in current dynamic scope or one of its captured scopes.
Params:
offset – zero-indexed value that represents where variable lives
value – to set
depth – how many captured scopes down this variable should be set/**
     * Set value in current dynamic scope or one of its captured scopes.
     * 
     * @param offset zero-indexed value that represents where variable lives
     * @param value to set
     * @param depth how many captured scopes down this variable should be set
     */
    public void setValueVoid(IRubyObject value, int offset, int depth) {
        if (depth > 0) {
            DynamicScope parent = this.parent;

            assert parent != null : "If depth > 0, then parent should not ever be null";

            parent.setValueVoid(value, offset, depth - 1);
        } else {
            IRubyObject[] variableValues = this.variableValues;

            assert checkOffset(variableValues, offset) : failSet(this, value, offset);

            setValueDepthZeroVoid(value, offset);
        }
    }

    public void setValueDepthZeroVoid(IRubyObject value, int offset) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, offset) : failSet(this, value, offset);

        variableValues[offset] = value;
    }
    public void setValueZeroDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 0) : failSet(this, value, 0);

        variableValues[0] = value;
    }
    public void setValueOneDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 1) : failSet(this, value, 1);

        variableValues[1] = value;
    }
    public void setValueTwoDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 2) : failSet(this, value, 2);

        variableValues[2] = value;
    }
    public void setValueThreeDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 3) : failSet(this, value, 3);

        variableValues[3] = value;
    }
    public void setValueFourDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 3) : failSet(this, value, 3);

        variableValues[4] = value;
    }
    public void setValueFiveDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 3) : failSet(this, value, 3);

        variableValues[5] = value;
    }
    public void setValueSixDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 3) : failSet(this, value, 3);

        variableValues[6] = value;
    }
    public void setValueSevenDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 3) : failSet(this, value, 3);

        variableValues[7] = value;
    }
    public void setValueEightDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 3) : failSet(this, value, 3);

        variableValues[8] = value;
    }
    public void setValueNineDepthZeroVoid(IRubyObject value) {
        IRubyObject[] variableValues = this.variableValues;

        assert checkOffset(variableValues, 3) : failSet(this, value, 3);

        variableValues[9] = value;
    }

    private static boolean checkOffset(IRubyObject[] variableValues, int offset) {
        return variableValues != null && offset < variableValues.length;
    }

    private static String failGet(ManyVarsDynamicScope scope, int offset) {
        return failGet(scope, offset, 0);
    }

    private static String failGet(ManyVarsDynamicScope scope, int offset, int depth) {
        return "No variables or index too big for getValue off: " + offset + ", Dep: " + depth + ", O: " + scope;
    }

    private static String failSet(ManyVarsDynamicScope scope, IRubyObject value, int offset) {
        return "Setting " + offset + " to " + value + ", O: " + scope;
    }

    
Make a larger dynamic scope if the static scope grew.
Eval's with bindings require us to possibly change the size of the dynamic scope if
things like 'eval "b = 2", binding' happens.
/**
     * 
     * Make a larger dynamic scope if the static scope grew.
     * 
     * Eval's with bindings require us to possibly change the size of the dynamic scope if
     * things like 'eval "b = 2", binding' happens.
     *
     */
    public void growIfNeeded() {
        int dynamicSize = variableValues == null ? 0: variableValues.length;
        
        if (staticScope.getNumberOfVariables() > dynamicSize) {
            IRubyObject values[] = new IRubyObject[staticScope.getNumberOfVariables()];
            
            if (dynamicSize > 0) {
                ArraySupport.copy(variableValues, 0, values, 0, dynamicSize);
            }
            
            variableValues = values;
        }
    }

    @Deprecated
    public DynamicScope cloneScope() {
        // we construct new rather than clone to avoid sharing variableValues
        return new ManyVarsDynamicScope(staticScope, parent);
    }
}