com.github.fge.uritemplate.expression.TemplateExpression Maven / Gradle / Ivy

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/*
 * Copyright (c) 2014, Francis Galiegue ([email protected])
 *
 * This software is dual-licensed under:
 *
 * - the Lesser General Public License (LGPL) version 3.0 or, at your option, any
 *   later version;
 * - the Apache Software License (ASL) version 2.0.
 *
 * The text of this file and of both licenses is available at the root of this
 * project or, if you have the jar distribution, in directory META-INF/, under
 * the names LGPL-3.0.txt and ASL-2.0.txt respectively.
 *
 * Direct link to the sources:
 *
 * - LGPL 3.0: https://www.gnu.org/licenses/lgpl-3.0.txt
 * - ASL 2.0: http://www.apache.org/licenses/LICENSE-2.0.txt
 */

package com.github.fge.uritemplate.expression;

import com.github.fge.uritemplate.URITemplateException;
import com.github.fge.uritemplate.render.ValueRenderer;
import com.github.fge.uritemplate.vars.VariableMap;
import com.github.fge.uritemplate.vars.specs.VariableSpec;
import com.github.fge.uritemplate.vars.values.VariableValue;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;

import java.util.List;

/**
 * Template expression (ie, not literal) rendering class
 *
 * This class ultimately handles all {@code {...}} sequences found in a
 * URI template.
 *
 * @see ValueRenderer
 */
public final class TemplateExpression
    implements URITemplateExpression
{
    private final ExpressionType expressionType;
    private final List variableSpecs;

    public TemplateExpression(final ExpressionType expressionType,
        final List variableSpecs)
    {
        this.expressionType = expressionType;
        this.variableSpecs = ImmutableList.copyOf(variableSpecs);
    }

    @Override
    public String expand(final VariableMap vars)
        throws URITemplateException
    {
        /*
         * Near exact reproduction of the suggested algorithm, with two
         * differences:
         *
         * - parsing errors are treated elsewhere;
         * - the possibility of varspecs both exploded and prefixed is left
         *   open; not here: it is one or the other, not both.
         */

        // Expanded values
        final List expansions = Lists.newArrayList();

        VariableValue value;
        ValueRenderer renderer;

        /*
         * Walk over the defined varspecs for this template
         */
        for (final VariableSpec varspec: variableSpecs) {
            value = vars.get(varspec.getName());
            // No such variable: continue
            if (value == null)
                continue;
            renderer = value.getType().selectRenderer(expressionType);
            expansions.addAll(renderer.render(varspec, value));
        }

        if (expansions.isEmpty())
            return "";
        final Joiner joiner = Joiner.on(expressionType.getSeparator());
        // Where the final result is stored
        final StringBuilder sb = new StringBuilder(expressionType.getPrefix());
        joiner.appendTo(sb, expansions);
        return sb.toString();
    }

    @Override
    public int hashCode()
    {
        return 31 * expressionType.hashCode() + variableSpecs.hashCode();
    }

    @Override
    public boolean equals(final Object obj)
    {
        if (obj == null)
            return false;
        if (this == obj)
            return true;
        if (getClass() != obj.getClass())
            return false;
        final TemplateExpression other = (TemplateExpression) obj;
        return expressionType == other.expressionType
            && variableSpecs.equals(other.variableSpecs);
    }
}