/*
 * Copyright 2015 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.jssrc.internal;

import com.google.template.soy.jssrc.restricted.JsExpr;
import com.google.template.soy.jssrc.restricted.JsExprUtils;
import com.google.template.soy.shared.internal.CodeBuilder;

import java.util.List;

/**
 * A JavaScript implementation of the CodeBuilder class.
 *
 * <p>Usage example that demonstrates most of the methods:
 * <pre>
 *   JsCodeBuilder jcb = new JsCodeBuilder(CodeStyle.STRINGBUILDER);
 *   jcb.appendLine("story.title = function(opt_data) {");
 *   jcb.increaseIndent();
 *   jcb.pushOutputVar("output");
 *   jcb.initOutputVarIfNecessary();
 *   jcb.pushOutputVar("temp");
 *   jcb.addToOutputVar(Lists.newArrayList(
 *       new JsExpr("'Snow White and the '", Integer.MAX_VALUE),
 *       new JsExpr("opt_data.numDwarfs", Integer.MAX_VALUE));
 *   jcb.popOutputVar();
 *   jcb.addToOutputVar(Lists.newArrayList(
 *       new JsExpr("temp", Integer.MAX_VALUE),
 *       new JsExpr("' Dwarfs'", Integer.MAX_VALUE));
 *   jcb.appendLineStart("return ").appendOutputVarName().appendLineEnd(".toString();");
 *   jcb.popOutputVar();
 *   jcb.decreaseIndent();
 *   String THE_END = "the end";
 *   jcb.appendLine("}  // ", THE_END);
 * </pre>
 *
 * <p>The above example builds the following JS code:
 * <pre>
 * story.title = function(opt_data) {
 *   var output = new soy.StringBuilder();
 *   var temp = new soy.StringBuilder('Snow White and the ', opt_data.numDwarfs);
 *   output.append(temp, ' Dwarfs');
 *   return output.toString();
 * }  // the end
 * </pre>
 *
 */
final class JsCodeBuilder extends CodeBuilder<JsExpr> {

  @Override public void initOutputVarIfNecessary() {

    if (getOutputVarIsInited()) {
      // Nothing to do since it's already initialized.
      return;
    }

    // var output = '';
    appendLine("var ", getOutputVarName(), " = '';");
    setOutputVarInited();
  }

  @Override public void addToOutputVar(List<? extends JsExpr> jsExprs) {
    if (getOutputVarIsInited()) {
      // output += AAA + BBB + CCC;
      appendLine(getOutputVarName(), " += ", JsExprUtils.concatJsExprs(jsExprs).getText(), ";");
    } else {
      // var output = '' + AAA + BBB + CCC;
      // NOTE: We initialize with '' to enforce string concatenation. This ensures something like
      // {2}{2} becomes '22' instead of 4.
      // TODO: Optimize this away if we know the first or second expression is a string.
      String contents = JsExprUtils.concatJsExprsForceString(jsExprs).getText();
      appendLine("var ", getOutputVarName(), " = ", contents, ";");
      setOutputVarInited();
    }
  }
}