// Copyright 2017 The Bazel Authors. All rights reserved.
//
// 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.devtools.bazel.e4b.projectviews;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.nio.file.Files;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

/** A class to create a {@link ProjectView} */
public class Builder {
  private ImmutableList.Builder<String> buildFlags = ImmutableList.builder();
  private ImmutableList.Builder<String> directories = ImmutableList.builder();
  private ImmutableList.Builder<String> targets = ImmutableList.builder();
  private int javaLanguageLevel = 0; // <= 0 means take it from java_toolchain.

  Builder() {}

  public Builder addBuildFlag(String... flag) {
    buildFlags.add(flag);
    return this;
  }

  public Builder addDirectory(String... dir) {
    directories.add(dir);
    return this;
  }

  public Builder addTarget(String... target) {
    targets.add(target);
    return this;
  }

  public Builder setJavaLanguageLevel(int level) {
    Preconditions.checkArgument(level > 0, "Can only set java language level to a value > 0");
    Preconditions.checkArgument(javaLanguageLevel == 0, "Java language level was already set");
    javaLanguageLevel = level;
    return this;
  }

  // State object using while parsing a stream
  private String currentSection = null;

  /**
   * Parse the project view given in view, following also imports.
   * 
   * @throws IOException
   * @throws ProjectViewParseException
   */
  public Builder parseView(File view) throws IOException, ProjectViewParseException {
    int linenb = 0;
    for (String line : Files.readAllLines(view.toPath())) {
      linenb++;
      parseLine(view.getPath(), view.getParentFile(), line, linenb);
    }
    currentSection = null;
    return this;
  }

  /**
   * Parse the project view at the given {@code url}.
   * 
   * @throws IOException
   * @throws ProjectViewParseException
   */
  public Builder parseView(URL url) throws IOException, ProjectViewParseException {
    int linenb = 0;
    try (BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()))) {
      for (String line : reader.lines().toArray(String[]::new)) {
        linenb++;
        parseLine(url.toString(), null, line, linenb);
      }
    }
    currentSection = null;
    return this;
  }

  private void parseLine(String fileName, File parentFile, String line, int linenb)
      throws ProjectViewParseException, IOException {
    if (line.isEmpty()) {
      currentSection = null;
    } else if (line.startsWith("  ")) {
      if (currentSection == null) {
        throw new ProjectViewParseException(
            "Line " + linenb + " of project view " + fileName + " is not in a section");
      }
      if (currentSection.equals("directories")) {
        directories.add(line.substring(2));
      } else if (currentSection.equals("targets")) {
        targets.add(line.substring(2));
      } else if (currentSection.equals("build_flags")) {
        buildFlags.add(line.substring(2));
      } // else ignoring other sections
    } else if (line.startsWith("import ")) {
      // imports
      String path = line.substring(7);
      if (path.startsWith("/")) {
        parseView(new File(path));
      } else {
        parseView(new File(parentFile, path));
      }
    } else if (line.contains(":")) {
      // section declaration
      line = line.trim();
      if (line.endsWith(":")) {
        currentSection = line.substring(0, line.length() - 1);
        if (currentSection.equals("java_language_level")) {
          throw new ProjectViewParseException("Line " + linenb + " of project view "
              + fileName + ": java_language_level cannot be a section name");
        }
      } else {
        int colonIndex = line.indexOf(':');
        String label = line.substring(0, colonIndex).trim();
        String value = line.substring(colonIndex + 1).trim();
        if (label.equals("directories") || label.equals("import") || label.equals("targets")
            || label.equals("build_flags")) {
          throw new ProjectViewParseException("Line " + linenb + " of project view "
              + fileName + ": " + label + " cannot be a label name");
        }
        if (label.equals("java_language_level")) {
          if (!value.matches("^[0-9]+$")) {
            throw new ProjectViewParseException("Line " + linenb + " of project view "
                + fileName + ": java_language_level should be an integer.");
          }
          javaLanguageLevel = Integer.parseInt(value);
        }
      }
    } else if (!line.trim().startsWith("#")) {
      throw new ProjectViewParseException(
          "Project view " + fileName + " contains a syntax error at line " + linenb);
    }
  }

  public ProjectView build() {
    return new ProjectViewImpl(directories.build(), targets.build(), javaLanguageLevel,
        buildFlags.build());
  }
}