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

import java.util.Arrays;

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 class Arity1Func extends FunctionImpl1 {
        private final Object[] inheritedVariableBindings;

        private Arity1Func(Object[] inheritedVariableBindings) {
            this.inheritedVariableBindings = inheritedVariableBindings;
        }

        @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);
        }

        @Override
        public int hashCode() {
            return ILambda.this.hashCode() + 31*Arrays.hashCode(inheritedVariableBindings);
        }

        private ILambda getParent() {
            return ILambda.this;
        }
        
        @Override
        public boolean equals(Object obj) {
            if(obj == this)
                return true;
            if(obj == null || obj.getClass() != getClass())
                return false;
            Arity1Func other = (Arity1Func)obj;
            return ILambda.this == other.getParent() && Arrays.equals(inheritedVariableBindings, other.inheritedVariableBindings);
        }
    }

    private final class Arity2Func extends FunctionImpl2 {
        private final Object[] inheritedVariableBindings;

        private Arity2Func(Object[] inheritedVariableBindings) {
            this.inheritedVariableBindings = inheritedVariableBindings;
        }

        @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);
        }
        
        @Override
        public int hashCode() {
            return ILambda.this.hashCode() + 31*Arrays.hashCode(inheritedVariableBindings);
        }

        private ILambda getParent() {
            return ILambda.this;
        }
        
        @Override
        public boolean equals(Object obj) {
            if(obj == this)
                return true;
            if(obj == null || obj.getClass() != getClass())
                return false;
            Arity2Func other = (Arity2Func)obj;
            return ILambda.this == other.getParent() && Arrays.equals(inheritedVariableBindings, other.inheritedVariableBindings);
        }
    }

    private final class Arity3Func extends FunctionImpl3 {
        private final Object[] inheritedVariableBindings;

        private Arity3Func(Object[] inheritedVariableBindings) {
            this.inheritedVariableBindings = inheritedVariableBindings;
        }

        @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);
        }
        
        @Override
        public int hashCode() {
            return ILambda.this.hashCode() + 31*Arrays.hashCode(inheritedVariableBindings);
        }

        private ILambda getParent() {
            return ILambda.this;
        }
        
        @Override
        public boolean equals(Object obj) {
            if(obj == this)
                return true;
            if(obj == null || obj.getClass() != getClass())
                return false;
            Arity3Func other = (Arity3Func)obj;
            return ILambda.this == other.getParent() && Arrays.equals(inheritedVariableBindings, other.inheritedVariableBindings);
        }
    }

    private final class Arity4Func extends FunctionImpl4 {
        private final Object[] inheritedVariableBindings;

        private Arity4Func(Object[] inheritedVariableBindings) {
            this.inheritedVariableBindings = inheritedVariableBindings;
        }

        @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);
        }

        @Override
        public int hashCode() {
            return ILambda.this.hashCode() + 31*Arrays.hashCode(inheritedVariableBindings);
        }

        private ILambda getParent() {
            return ILambda.this;
        }
        
        @Override
        public boolean equals(Object obj) {
            if(obj == this)
                return true;
            if(obj == null || obj.getClass() != getClass())
                return false;
            Arity4Func other = (Arity4Func)obj;
            return ILambda.this == other.getParent() && Arrays.equals(inheritedVariableBindings, other.inheritedVariableBindings);
        }
    }

    private final class ArityNFunc extends FunctionImplN {
        private final Object[] inheritedVariableBindings;

        private ArityNFunc(Object[] inheritedVariableBindings) {
            super(arity);
            this.inheritedVariableBindings = inheritedVariableBindings;
        }

        @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 int hashCode() {
            return ILambda.this.hashCode() + 31*Arrays.hashCode(inheritedVariableBindings);
        }

        private ILambda getParent() {
            return ILambda.this;
        }
        
        @Override
        public boolean equals(Object obj) {
            if(obj == this)
                return true;
            if(obj == null || obj.getClass() != getClass())
                return false;
            ArityNFunc other = (ArityNFunc)obj;
            return ILambda.this == other.getParent() && Arrays.equals(inheritedVariableBindings, other.inheritedVariableBindings);
        }
    }

    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;
    }

    @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 Arity1Func(inheritedVariableBindings);
        case 2:
            return new Arity2Func(inheritedVariableBindings);
        case 3:
            return new Arity3Func(inheritedVariableBindings);
        case 4:
            return new Arity4Func(inheritedVariableBindings);
        default:
            return new ArityNFunc(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 ");
        }    	
    }
}