TruncateDirective.java

/*
 * Copyright 2011 Google 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.google.template.soy.basicdirectives;

import com.google.common.collect.ImmutableSet;
import com.google.template.soy.data.SoyDataException;
import com.google.template.soy.data.SoyValue;
import com.google.template.soy.data.restricted.StringData;
import com.google.template.soy.jssrc.restricted.JsExpr;
import com.google.template.soy.jssrc.restricted.SoyLibraryAssistedJsSrcPrintDirective;
import com.google.template.soy.pysrc.restricted.PyExpr;
import com.google.template.soy.pysrc.restricted.PyFunctionExprBuilder;
import com.google.template.soy.pysrc.restricted.SoyPySrcPrintDirective;
import com.google.template.soy.shared.restricted.SoyJavaPrintDirective;
import com.google.template.soy.shared.restricted.SoyPurePrintDirective;
import java.util.List;
import java.util.Set;
import javax.inject.Inject;
import javax.inject.Singleton;

/**
 * A directive that truncates a string to a maximum length if it is too long, optionally adding
 * ellipsis.
 *
 */
@Singleton
@SoyPurePrintDirective
final class TruncateDirective
    implements SoyJavaPrintDirective,
        SoyLibraryAssistedJsSrcPrintDirective,
        SoyPySrcPrintDirective {

  @Inject
  public TruncateDirective() {}

  @Override
  public String getName() {
    return "|truncate";
  }

  @Override
  public Set<Integer> getValidArgsSizes() {
    return ImmutableSet.of(1, 2);
  }

  @Override
  public boolean shouldCancelAutoescape() {
    return false;
  }

  @Override
  public SoyValue applyForJava(SoyValue value, List<SoyValue> args) {
    int maxLen;
    try {
      maxLen = args.get(0).integerValue();
    } catch (SoyDataException sde) {
      throw new IllegalArgumentException(
          "Could not parse first parameter of '|truncate' as integer (value was \""
              + args.get(0).stringValue()
              + "\").");
    }

    String str = value.coerceToString();
    if (str.length() <= maxLen) {
      return StringData.forValue(str); // no need to truncate
    }

    boolean doAddEllipsis;
    if (args.size() == 2) {
      try {
        doAddEllipsis = args.get(1).booleanValue();
      } catch (SoyDataException sde) {
        throw new IllegalArgumentException(
            "Could not parse second parameter of '|truncate' as boolean.");
      }
    } else {
      doAddEllipsis = true; // default to true
    }

    // If doAddEllipsis, either reduce maxLen to compensate, or else if maxLen is too small, just
    // turn off doAddEllipsis.
    if (doAddEllipsis) {
      if (maxLen > 3) {
        maxLen -= 3;
      } else {
        doAddEllipsis = false;
      }
    }

    // Make sure truncating at maxLen doesn't cut up a unicode surrogate pair.
    if (Character.isHighSurrogate(str.charAt(maxLen - 1))
        && Character.isLowSurrogate(str.charAt(maxLen))) {
      maxLen -= 1;
    }

    // Truncate.
    str = str.substring(0, maxLen);

    // Add ellipsis.
    if (doAddEllipsis) {
      str += "...";
    }

    return StringData.forValue(str);
  }

  @Override
  public JsExpr applyForJsSrc(JsExpr value, List<JsExpr> args) {
    String maxLenExprText = args.get(0).getText();
    String doAddEllipsisExprText = (args.size() == 2) ? args.get(1).getText() : "true" /*default*/;

    return new JsExpr(
        "soy.$$truncate("
            + value.getText()
            + ", "
            + maxLenExprText
            + ", "
            + doAddEllipsisExprText
            + ")",
        Integer.MAX_VALUE);
  }

  @Override
  public ImmutableSet<String> getRequiredJsLibNames() {
    return ImmutableSet.of("soy");
  }

  @Override
  public PyExpr applyForPySrc(PyExpr value, List<PyExpr> args) {
    // Truncation always wants a string, so to potentially save an unnecessary conversion, we do
    // optional coercing at compile time.
    PyExpr input = value.toPyString();
    PyExpr maxLen = args.get(0);
    PyExpr doAddEllipsis = (args.size() == 2) ? args.get(1) : new PyExpr("True", Integer.MAX_VALUE);

    PyFunctionExprBuilder fnBuilder = new PyFunctionExprBuilder("directives.truncate");
    fnBuilder.addArg(input).addArg(maxLen).addArg(doAddEllipsis);
    return fnBuilder.asPyStringExpr();
  }
}