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/*
 * Copyright 2007 The Closure Compiler Authors.
 *
 * 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.javascript.jscomp;

import com.google.debugging.sourcemap.proto.Mapping.OriginalMapping;
import javax.annotation.Nullable;

/**
 * A source excerpt provider is responsible for building source code excerpt
 * of specific locations, such as a specific line or a region around a
 * given line number.
 */
public interface SourceExcerptProvider {
  /**
   * Source excerpt variety.
   */
  enum SourceExcerpt {
    /**
     * Line excerpt.
     */
    LINE {
      @Override
      public String get(
          SourceExcerptProvider source,
          String sourceName,
          int lineNumber,
          int unused,
          ExcerptFormatter formatter) {
        return formatter.formatLine(
            source.getSourceLine(sourceName, lineNumber), lineNumber);
      }
    },
    /** Multiple lines excerpt. */
    FULL {
      @Override
      public String get(
          SourceExcerptProvider source,
          String sourceName,
          int startLineNumber,
          int length,
          ExcerptFormatter formatter) {
        return formatter.formatRegion(source.getSourceLines(sourceName, startLineNumber, length));
      }
    },
    /**
     * Region excerpt.
     */
    REGION {
      @Override
      public String get(
          SourceExcerptProvider source,
          String sourceName,
          int lineNumber,
          int length,
          ExcerptFormatter formatter) {
        return formatter.formatRegion(
            source.getSourceRegion(sourceName, lineNumber));
      }
    };

    /** Get a source excerpt string based on the type of the source excerpt. */
    public String get(
        SourceExcerptProvider source,
        String sourceName,
        int lineNumber,
        ExcerptFormatter formatter) {
      return this.get(source, sourceName, lineNumber, -1, formatter);
    }

    /** Get a source excerpt string based on the type of the source excerpt. */
    public abstract String get(
        SourceExcerptProvider source,
        String sourceName,
        int lineNumber,
        int length,
        ExcerptFormatter formatter);
  }

  /**
   * Get the line indicated by the line number. This call will return only the
   * specific line.
   *
   * @param lineNumber the line number, 1 being the first line of the file
   * @return the line indicated, or {@code null} if it does not exist
   */
  String getSourceLine(String sourceName, int lineNumber);

  /**
   * Gets the specific lines returned by the beginning and excerpt length. Must not start or end
   * with a carriage return. Implementations may decide to truncate lines but will always include
   * the first line and never be longer than the specified length.
   *
   * @param lineNumber the line number, 1 being the first line of the file
   * @param length the desired length of the excerpt (in chars). If -1, returns just a single line.
   *     Otherwise, returns as many lines as needed. (including the remainder of the last line)
   * @return the region around the line number indicated, or {@code null} if it does not exist
   */
  @Nullable
  Region getSourceLines(String sourceName, int lineNumber, int length);

  /**
   * Get a region around the indicated line number. The exact definition of a region is
   * implementation specific, but it must contain the line indicated by the line number. A region
   * must not start or end by a carriage return.
   *
   * @param lineNumber the line number, 1 being the first line of the file
   * @return the region around the line number indicated, or {@code null} if it does not exist
   */
  @Nullable
  Region getSourceRegion(String sourceName, int lineNumber);

  /**
   * If the source file is associated with an inputSourceMap, does a lookup
   * for the original file position based on this source map.
   */
  OriginalMapping getSourceMapping(String sourceName, int lineNumber, int columnNumber);

  /**
   * A excerpt formatter is responsible of formatting source excerpts.
   */
  interface ExcerptFormatter {
    /**
     * Format a line excerpt.
     */
    String formatLine(String line, int lineNumber);

    /** Format a region excerpt. */
    String formatRegion(@Nullable Region region);
  }
}