// Copyright (C) 2013 The Android Open Source Project
//
// 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.googlesource.gerrit.plugins.its.base.workflow;

import com.google.common.collect.Lists;
import com.google.inject.Inject;
import com.googlesource.gerrit.plugins.its.base.GlobalRulesFileName;
import com.googlesource.gerrit.plugins.its.base.ItsPath;
import com.googlesource.gerrit.plugins.its.base.PluginRulesFileName;
import java.io.File;
import java.io.IOException;
import java.nio.file.Path;
import java.util.Collection;
import java.util.Map;
import org.eclipse.jgit.errors.ConfigInvalidException;
import org.eclipse.jgit.storage.file.FileBasedConfig;
import org.eclipse.jgit.util.FS;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/** Collection and matcher against {@link Rule}s. */
public class RuleBase {
  private static final Logger log = LoggerFactory.getLogger(RuleBase.class);

  /** The section for rules within rulebases */
  private static final String RULE_SECTION = "rule";

  /** The key for actions within rulebases */
  private static final String ACTION_KEY = "action";

  private final Path itsPath;
  private final Rule.Factory ruleFactory;
  private final Condition.Factory conditionFactory;
  private final ActionRequest.Factory actionRequestFactory;
  private final String globalRulesFileName;
  private final String pluginRulesFileName;

  private Collection<Rule> rules;

  public interface Factory {
    RuleBase create();
  }

  @Inject
  public RuleBase(
      @ItsPath Path itsPath,
      Rule.Factory ruleFactory,
      Condition.Factory conditionFactory,
      ActionRequest.Factory actionRequestFactory,
      @GlobalRulesFileName String globalRulesFileName,
      @PluginRulesFileName String pluginRulesFileName) {
    this.itsPath = itsPath;
    this.ruleFactory = ruleFactory;
    this.conditionFactory = conditionFactory;
    this.actionRequestFactory = actionRequestFactory;
    this.globalRulesFileName = globalRulesFileName;
    this.pluginRulesFileName = pluginRulesFileName;
    reloadRules();
  }

  /**
   * Adds rules from a file to the RuleBase.
   *
   * <p>If the given file does not exist, it is silently ignored
   *
   * @param ruleFile File from which to read the rules
   */
  private void addRulesFromFile(File ruleFile) {
    if (ruleFile.exists()) {
      FileBasedConfig cfg = new FileBasedConfig(ruleFile, FS.DETECTED);
      try {
        cfg.load();
      } catch (IOException | ConfigInvalidException e) {
        log.error("Invalid ITS action configuration", e);
        return;
      }

      for (String subsection : cfg.getSubsections(RULE_SECTION)) {
        Rule rule = ruleFactory.create(subsection);
        for (String key : cfg.getNames(RULE_SECTION, subsection)) {
          String[] values = cfg.getStringList(RULE_SECTION, subsection, key);
          if (ACTION_KEY.equals(key)) {
            addActions(rule, values);
          } else {
            addConditions(rule, key, values);
          }
        }
        rules.add(rule);
      }
    }
  }

  private void addActions(Rule rule, String[] values) {
    for (String value : values) {
      rule.addActionRequest(actionRequestFactory.create(value));
    }
  }

  private void addConditions(Rule rule, String key, String[] values) {
    for (String value : values) {
      rule.addCondition(conditionFactory.create(key, value));
    }
  }

  /** Loads the rules for the RuleBase. */
  private void reloadRules() {
    rules = Lists.newArrayList();

    // Add global rules
    File globalRuleFile = itsPath.resolve(globalRulesFileName).toFile();
    addRulesFromFile(globalRuleFile);

    // Add its-specific rules
    File itsSpecificRuleFile = itsPath.resolve(pluginRulesFileName).toFile();
    addRulesFromFile(itsSpecificRuleFile);

    if (!globalRuleFile.exists() && !itsSpecificRuleFile.exists()) {
      log.warn(
          "Neither global rule file {} nor Its specific rule file {} exist. Please configure rules.",
          globalRuleFile,
          itsSpecificRuleFile);
    }
  }

  /**
   * Gets the action requests for a set of properties.
   *
   * @param properties The properties to search actions for.
   * @return Requests for the actions that should be fired.
   */
  public Collection<ActionRequest> actionRequestsFor(Map<String, String> properties) {
    Collection<ActionRequest> ret = Lists.newLinkedList();
    for (Rule rule : rules) {
      ret.addAll(rule.actionRequestsFor(properties));
    }
    return ret;
  }
}