com.squarespace.template.Arguments.java Source code

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Here is the source code for com.squarespace.template.Arguments.java

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/**
 * Copyright (c) 2014 SQUARESPACE, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.squarespace.template;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import org.apache.commons.lang3.StringUtils;

/**
 * Holds arguments for Formatter/Predicate instances.
 *
 * It associates an argument delimiter with the list of arguments, and defines
 * methods allowing plugins to assert that the correct number of arguments are
 * present.
 */
public class Arguments {

    /**
     * Raw arguments.
     */
    private List<String> args = Collections.emptyList();

    /**
     * Argument delimiter character.
     */
    private char delimiter = ' ';

    /**
     * A place where a Predicate / Formatter can attach data to the parsed arguments.
     */
    private Object opaque;

    /**
     * Constructs an empty argument set.
     */
    public Arguments() {
    }

    /**
     * Constructs arguments by parsing the given raw string.
     */
    public Arguments(StringView raw) {
        parse(raw);
    }

    /**
     * Returns a string with the arguments joined using the delimiter.
     */
    public String join() {
        StringBuilder buf = new StringBuilder();
        ReprEmitter.emit(this, false, buf);
        return buf.toString();
    }

    /**
     * Returns the first argument.
     */
    public String first() {
        return args.get(0);
    }

    /**
     * Returns the Nth argument.
     */
    public String get(int index) {
        return args.get(index);
    }

    /**
     * Returns the number of arguments.
     */
    public int count() {
        return args.size();
    }

    /**
     * Indicates whether the argument list is empty.
     */
    public boolean isEmpty() {
        return args.isEmpty();
    }

    /**
     * Returns the delimiter character.
     */
    public char getDelimiter() {
        return delimiter;
    }

    /**
     * Returns the arguments.
     */
    public List<String> getArgs() {
        return args;
    }

    /**
     * Associates an opaque object with the Arguments instance so it can be retrieved later.
     * Typically, you'll convert your arguments in the parsing phase, in order to report errors
     * early.  Then your plugin can fetch the already-converted arguments during the execute phase.
     */
    public void setOpaque(Object obj) {
        this.opaque = obj;
    }

    /**
     * @see #setOpaque(Object)
     */
    public Object getOpaque() {
        return this.opaque;
    }

    // Helper methods to make assertions about the args.

    /**
     * Asserts there are exactly {@code num} arguments. Throws an exception otherwise.
     */
    public void exactly(int num) throws ArgumentsException {
        if (args.size() != num) {
            throw new ArgumentsException("Wrong number of args, exactly " + num + " expected");
        }
    }

    /**
     * Asserts there are at most {@code num} arguments. Throws an exception otherwise.
     */
    public void atMost(int num) throws ArgumentsException {
        between(0, num);
    }

    /**
     * Asserts there are at least {@code num} arguments. Throws an exception otherwise.
     */
    public void atLeast(int num) throws ArgumentsException {
        between(num, Integer.MAX_VALUE);
    }

    /**
     * Asserts there are between {@code min} and {@code max} arguments, inclusive.
     * Throws an exception otherwise.
     */
    public void between(int min, int max) throws ArgumentsException {
        if (args.size() < min) {
            throw new ArgumentsException("Not enough args. At least " + min + " expected");
        }
        if (args.size() > max) {
            throw new ArgumentsException("Too many args. Takes between " + min + " and " + max);
        }
    }

    @Override
    public String toString() {
        return ReprEmitter.get(this, false);
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof Arguments) {
            Arguments other = (Arguments) obj;
            return delimiter == other.delimiter && args.equals(other.args);
        }
        return false;
    }

    @Override
    public int hashCode() {
        throw new UnsupportedOperationException("Arguments does not implement hashCode()");
    }

    /**
     * Parses the raw string into a list of arguments.
     */
    private void parse(StringView raw) {
        if (raw == null || raw.length() == 0) {
            return;
        }
        delimiter = raw.charAt(0);
        raw = raw.subview(1, raw.length());
        args = Arrays.asList(StringUtils.split(raw.repr(), delimiter));
    }

}