package org.simantics.scl.compiler.internal.interpreted;

import org.simantics.scl.runtime.function.FunctionImpl1;
import org.simantics.scl.runtime.function.FunctionImpl2;
import org.simantics.scl.runtime.function.FunctionImpl3;
import org.simantics.scl.runtime.function.FunctionImpl4;
import org.simantics.scl.runtime.function.FunctionImplN;

public class ILambda implements IExpression {
    private final int[] inheritedVariableIds;
    private final int arity;
    private final int variableBindingsLength;
    private final IExpression body;
    
    public ILambda(int[] inheritedVariableIds, int arity,
            int variableBindingsLength, IExpression body) {
        this.inheritedVariableIds = inheritedVariableIds;
        this.arity = arity;
        this.variableBindingsLength = variableBindingsLength;
        this.body = body;
    }

    @SuppressWarnings("rawtypes")
    @Override
    public Object execute(Object[] variableBindings) {
        final Object[] inheritedVariableBindings = new Object[inheritedVariableIds.length];
        for(int i=0;i<inheritedVariableIds.length;++i)
            inheritedVariableBindings[i] = variableBindings[inheritedVariableIds[i]];
        switch(arity) {
        case 1:
            return new FunctionImpl1() {
                @Override
                public Object apply(Object param0) {
                    Object[] newVariableBindings = new Object[variableBindingsLength];
                    int i = 0;;
                    for(;i < inheritedVariableBindings.length;++i)
                        newVariableBindings[i] = inheritedVariableBindings[i];
                    newVariableBindings[i] = param0;
                    return body.execute(newVariableBindings);
                }
                
                @Override
                public String toString() {
                	return ILambda.this.toString(inheritedVariableBindings);
                }
            };
        case 2:
            return new FunctionImpl2() {
                @Override
                public Object apply(Object param0, Object param1) {
                    Object[] newVariableBindings = new Object[variableBindingsLength];
                    int i = 0;;
                    for(;i < inheritedVariableBindings.length;++i)
                        newVariableBindings[i] = inheritedVariableBindings[i];
                    newVariableBindings[i++] = param0;
                    newVariableBindings[i] = param1;
                    return body.execute(newVariableBindings);
                }
                
                @Override
                public String toString() {
                	return ILambda.this.toString(inheritedVariableBindings);
                }
            };
        case 3:
            return new FunctionImpl3() {
                @Override
                public Object apply(Object param0, Object param1, Object param2) {
                    Object[] newVariableBindings = new Object[variableBindingsLength];
                    int i = 0;;
                    for(;i < inheritedVariableBindings.length;++i)
                        newVariableBindings[i] = inheritedVariableBindings[i];
                    newVariableBindings[i++] = param0;
                    newVariableBindings[i++] = param1;
                    newVariableBindings[i] = param2;
                    return body.execute(newVariableBindings);
                }
                
                @Override
                public String toString() {
                	return ILambda.this.toString(inheritedVariableBindings);
                }
            };
        case 4:
            return new FunctionImpl4() {
                @Override
                public Object apply(Object param0, Object param1, Object param2, Object param3) {
                    Object[] newVariableBindings = new Object[variableBindingsLength];
                    int i = 0;;
                    for(;i < inheritedVariableBindings.length;++i)
                        newVariableBindings[i] = inheritedVariableBindings[i];
                    newVariableBindings[i++] = param0;
                    newVariableBindings[i++] = param1;
                    newVariableBindings[i++] = param2;
                    newVariableBindings[i] = param3;
                    return body.execute(newVariableBindings);
                }
                
                @Override
                public String toString() {
                	return ILambda.this.toString(inheritedVariableBindings);
                }
            };
        default:
            return new FunctionImplN(arity) {
                @Override
                public Object doApply(Object... ps) {
                    Object[] newVariableBindings = new Object[variableBindingsLength];
                    int i = 0;;
                    for(;i < inheritedVariableBindings.length;++i)
                        newVariableBindings[i] = inheritedVariableBindings[i];
                    for(Object p : ps)
                        newVariableBindings[i++] = p;
                    return body.execute(newVariableBindings);
                }
                
                @Override
                public String toString() {
                	return ILambda.this.toString(inheritedVariableBindings);
                }
            };
        }
    }
    
    @Override
    public String toString() {
        StringBuilder b = new StringBuilder();
        b.append("(\\");
        for(int i=0;i<inheritedVariableIds.length;++i)
            b.append('v').append(i)
            .append("(v").append(inheritedVariableIds[i]).append(") ");
        for(int i=0;i<arity;++i)
            b.append('v').append(i+inheritedVariableIds.length).append(' ');
        b.append("-> ");
        b.append(body);
        b.append(')');
        return b.toString();
    }
    
    public String toString(Object[] variableBindings) {
    	StringBuilder sb = new StringBuilder();
    	appendVariableBindings(sb, variableBindings);
    	sb.append(this.toString());
    	return sb.toString();
    }
    
    private static void appendVariableBindings(StringBuilder sb, Object[] variableBindings) {
    	if (variableBindings.length > 0) {
    		sb.append("(let {");
        	for(int i = 0; i < variableBindings.length; i++) {
        		if (i > 0) sb.append("; ");
        		sb.append("v").append(i).append("=").append(variableBindings[i].toString());
        	}
        	sb.append("} in ");
    	}    	
    }
}