path: root/src/main/java/pl/edu/mimuw/cloudatlas/model/Value.java

/**
 * Copyright (c) 2014, University of Warsaw
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of
 * conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
 * conditions and the following disclaimer in the documentation and/or other materials provided
 * with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package pl.edu.mimuw.cloudatlas.model;

import pl.edu.mimuw.cloudatlas.model.Value;

/**
 * A single value stored as an attribute.
 */
public abstract class Value {
    /**
     * An operation that may be performed on values.
     */
    public enum Operation {
        EQUAL, COMPARE, ADD, SUBTRACT, MULTIPLY, DIVIDE, MODULO, AND, OR, REG_EXPR, NEGATE, VALUE_SIZE,
    }

    /**
     * Gets the type of this value.
     *
     * @return type of this value
     */
    public abstract Type getType();

    /**
     * Indicates whether this value is null. Distinct from a <code>Value</code> reference that is <code>null</code>
     * itself.
     *
     * @return true if and only if this value is null
     */
    public abstract boolean isNull();

    protected final void sameTypesOrThrow(Value value, Operation operation) {
        if(!getType().isCompatible(value.getType()))
            throw new IncompatibleTypesException(getType(), value.getType(), operation);
    }

    /**
     * Checks whether this value is equal to the specified one (operator ==).
     *
     * @param value the right side of the operator
     * @return a <code>ValueBoolean</code> representing true if and only if both values are equal
     * @throws UnsupportedValueOperationException if this operation is unsupported for these values
     */
    public Value isEqual(Value value) {
        throw new UnsupportedValueOperationException(getType(), Operation.EQUAL);
    }

    /**
     * Indicates whether this object is equal to another one.
     *
     * @param object the object to check
     * @return whether two objects are equal
     */
    @Override
    public boolean equals(Object object) {
        if(!(object instanceof Value))
            return false;
        return ((ValueBoolean)isEqual((Value)object)).getValue();
    }

    /**
     * Checks whether this value is lower than the specified one (operator <=).
     *
     * @param value the right side of the operator
     * @return a <code>ValueBoolean</code> representing true if and only if this value is lower than the provided one
     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
     * incompatible or non-numeric types)
     */
    public Value isLowerThan(Value value) {
        throw new UnsupportedValueOperationException(getType(), Operation.COMPARE);
    }

    /**
     * Returns a new value created by adding argument to this value (operator +).
     *
     * @param value the right side of the operator
     * @return a sum of two values
     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
     * incompatible or non-numeric types)
     */
    public Value addValue(Value value) {
        // name clash with add from List interface
        throw new UnsupportedValueOperationException(getType(), Operation.ADD);
    }

    /**
     * Returns a new value created by subtracting argument from this value (operator -).
     *
     * @param value the right side of the operator
     * @return a difference of two values
     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
     * incompatible or non-numeric types)
     */
    public Value subtract(Value value) {
        throw new UnsupportedValueOperationException(getType(), Operation.SUBTRACT);
    }

    /**
     * Returns a new value created by multiplying this value by an argument (operator *).
     *
     * @param value the right side of the operator
     * @return a product of two values
     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
     * incompatible or non-numeric types)
     */
    public Value multiply(Value value) {
        throw new UnsupportedValueOperationException(getType(), Operation.MULTIPLY);
    }

    /**
     * Returns a new value created by dividing this value by an argument (operator /).
     *
     * @param value the right side of the operator
     * @return a quotient of two values
     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
     * incompatible or non-numeric types)
     */
    public Value divide(Value value) {
        throw new UnsupportedValueOperationException(getType(), Operation.DIVIDE);
    }

    /**
     * Returns the remainder of division of this value by an argument (operator %).
     *
     * @param value the right side of the operator
     * @return a remainder
     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
     * incompatible or non-numeric types)
     */
    public Value modulo(Value value) {
        throw new UnsupportedValueOperationException(getType(), Operation.MODULO);
    }

    /**
     * Returns the result of a logical AND (operator &&).
     *
     * @param value the right side of the operator
     * @return a conjunction of the two values
     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
     * non-boolean types)
     */
    public Value and(Value value) {
        throw new UnsupportedValueOperationException(getType(), Operation.AND);
    }

    /**
     * Returns the result of a logical OR (operator ||).
     *
     * @param value the right side of the operator
     * @return an alternative of two values
     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
     * non-boolean types)
     */
    public Value or(Value value) {
        throw new UnsupportedValueOperationException(getType(), Operation.OR);
    }

    /**
     * Returns a result of trying to match to this value with a regular expression specified as an argument.
     *
     * @param value the regular expression to match against
     * @return a <code>ValueBoolean</code> representing true if and only if this value matches provided regular
     * expression
     * @throws UnsupportedValueOperationException if this operator is unsupported for these values
     */
    public Value regExpr(Value value) {
        throw new UnsupportedValueOperationException(getType(), Operation.REG_EXPR);
    }

    /**
     * Returns the negation (numeric or logical) of this value. This may refer to operator - or !, depending on type.
     *
     * @return a value that is the negation of this value
     * @throws UnsupportedValueOperationException if this operator is unsupported for this value
     */
    public Value negate() { // !, -
        throw new UnsupportedValueOperationException(getType(), Operation.NEGATE);
    }

    /**
     * Returns the size of this value. Semantics depend on type.
     *
     * @return a size of this value
     * @throws UnsupportedValueOperationException if this operation is unsupported for this value
     */
    public Value valueSize() {
        // name clash with size from List interface
        throw new UnsupportedValueOperationException(getType(), Operation.VALUE_SIZE);
    }

    /**
     * Returns this value converted to another type.
     *
     * @param to a desired type
     * @return this value converted to the <code>type</code>
     * @throws UnsupportedConversionException if a requested conversion is unsupported
     */
    public abstract Value convertTo(Type to);

    /**
     * Returns a textual representation of this value. This method uses conversion to <code>ValueString</code>.
     *
     * @return a textual representation of this value
     * @see #convertTo(Type)
     */
    @Override
    public String toString() {
        return ((ValueString)convertTo(TypePrimitive.STRING)).getValue();
    }

    /**
     * Returns a default value (such as an uninitialized variable). This may be <code>0</code> for integer types,
     * <code>false</code> for boolean, <code>null</code> for complex types, etc.
     *
     * @return a default value of this type
     */
    public abstract Value getDefaultValue();
}