/*
 * Copyright 2008 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.passes;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ListMultimap;
import com.google.template.soy.base.SourceLocation;
import com.google.template.soy.basetree.Node;
import com.google.template.soy.basetree.NodeVisitor;
import com.google.template.soy.basetree.SyntaxVersion;
import com.google.template.soy.error.ErrorReporter;
import com.google.template.soy.error.SoyErrorKind;
import com.google.template.soy.exprtree.VarRefNode;
import com.google.template.soy.passes.FindIndirectParamsVisitor.IndirectParamsInfo;
import com.google.template.soy.soytree.AbstractSoyNodeVisitor;
import com.google.template.soy.soytree.ExprUnion;
import com.google.template.soy.soytree.SoyFileNode;
import com.google.template.soy.soytree.SoyFileSetNode;
import com.google.template.soy.soytree.SoyNode;
import com.google.template.soy.soytree.SoyNode.ParentSoyNode;
import com.google.template.soy.soytree.SoytreeUtils;
import com.google.template.soy.soytree.TemplateBasicNode;
import com.google.template.soy.soytree.TemplateNode;
import com.google.template.soy.soytree.TemplateRegistry;
import com.google.template.soy.soytree.defn.TemplateParam;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Visitor for checking that in each template, the parameters declared in the SoyDoc match the data
 * keys referenced in the template.
 *
 * <p> Important: Do not use outside of Soy code (treat as superpackage-private).
 *
 * <p> Precondition: All template and callee names should be full names (i.e. you must execute
 * {@code SetFullCalleeNamesVisitor} before executing this visitor).
 *
 * <p> Note this visitor only works for code in Soy V2 syntax.
 *
 * <p> {@link #exec} should be called on a full parse tree. There is no return value.
 * However, errors are reported to the {@code ErrorReporter} if the parameters
 * declared in some template's SoyDoc do not match the data keys referenced in that template.
 *
 */
final class CheckTemplateParamsVisitor extends AbstractSoyNodeVisitor<Void> {

  private static final SoyErrorKind UNDECLARED_DATA_KEY =
      SoyErrorKind.of("Unknown data key ''{0}''.{1}");
  private static final SoyErrorKind UNUSED_PARAM =
      SoyErrorKind.of("Param ''{0}'' unused in template body.");

  /** User-declared syntax version. */
  private final SyntaxVersion declaredSyntaxVersion;
  private final ErrorReporter errorReporter;

  /** Registry of all templates in the Soy tree. */
  private final TemplateRegistry templateRegistry;

  /**
   * @param declaredSyntaxVersion User-declared syntax version,
   */
  CheckTemplateParamsVisitor(
      TemplateRegistry templateRegistry,
      SyntaxVersion declaredSyntaxVersion,
      ErrorReporter errorReporter) {
    this.templateRegistry = templateRegistry;
    this.errorReporter = errorReporter;
    this.declaredSyntaxVersion = declaredSyntaxVersion;
  }

  // -----------------------------------------------------------------------------------------------
  // Implementations for specific nodes.

  @Override protected void visitSoyFileSetNode(SoyFileSetNode node) {
    // Run pass only on the Soy files that are all in V2 syntax.
    for (SoyFileNode soyFile : node.getChildren()) {
      // Run pass on Soy file if it is all in V2 syntax.
      if (declaredSyntaxVersion.num >= SyntaxVersion.V2_0.num || allNodesInferredAboveV2(soyFile)) {
        visit(soyFile);
      }
    }
  }

  private boolean allNodesInferredAboveV2(SoyNode node) {
    final AtomicBoolean allV2 = new AtomicBoolean(true);
    SoytreeUtils.visitAllNodes(
        node,
        new NodeVisitor<Node, Boolean>() {
          @Override
          public Boolean exec(Node node) {
            if (!node.couldHaveSyntaxVersionAtLeast(SyntaxVersion.V2_0)) {
              allV2.set(false);
              return false;
            }
            // TODO(lukes): it would be nice if the fact that an ExprHolderNode contains v1
            // expressions was reflected in its inferred syntax version.
            if (node instanceof SoyNode.ExprHolderNode) {
              for (ExprUnion union : ((SoyNode.ExprHolderNode) node).getAllExprUnions()) {
                if (union.getExpr() == null) {
                  allV2.set(false);
                  return false;
                }
              }
            }
            return true;
          }
        });
    return allV2.get();
  }

  @Override protected void visitTemplateNode(TemplateNode node) {
    ListMultimap<String, SourceLocation> dataKeys = ArrayListMultimap.create();

    for (VarRefNode varRefNode : SoytreeUtils.getAllNodesOfType(node, VarRefNode.class)) {
      if (varRefNode.isPossibleParam()) {
        dataKeys.put(varRefNode.getName(), varRefNode.getSourceLocation());
      }
    }

    IndirectParamsInfo ipi = new FindIndirectParamsVisitor(templateRegistry).exec(node);

    Set<String> allParamNames = new HashSet<>();
    List<String> unusedParams = new ArrayList<>();
    for (TemplateParam param : node.getAllParams()) {
      allParamNames.add(param.name());
      if (dataKeys.containsKey(param.name())) {
        // Good: Declared and referenced in template. We remove these from dataKeys so
        // that at the end of the for-loop, dataKeys will only contain the keys that are referenced
        // but not declared in SoyDoc.
        dataKeys.removeAll(param.name());
      } else if (ipi.paramKeyToCalleesMultimap.containsKey(param.name()) ||
                 ipi.mayHaveIndirectParamsInExternalCalls ||
                 ipi.mayHaveIndirectParamsInExternalDelCalls) {
        // Good: Declared in SoyDoc and either (a) used in a call that passes all data or (b) used
        // in an external call or delcall that passes all data, which may need the param (we can't
        // verify).
      } else {
        // Bad: Declared in SoyDoc but not referenced in template.
        unusedParams.add(param.name());
      }
    }

    // At this point, the only keys left in dataKeys are undeclared.
    for (Entry<String, SourceLocation> undeclared : dataKeys.entries()) {
      String extraErrorMessage = "";
      errorReporter.report(
          undeclared.getValue(), UNDECLARED_DATA_KEY, undeclared.getKey(), extraErrorMessage);
    }

    // Delegate templates can declare unused params because other implementations
    // of the same delegate may need to use those params.
    if (node instanceof TemplateBasicNode) {
      for (String unusedParam : unusedParams) {
        errorReporter.report(node.getSourceLocation(), UNUSED_PARAM, unusedParam);
      }
    }
  }

  // -----------------------------------------------------------------------------------------------
  // Fallback implementation.

  @Override protected void visitSoyNode(SoyNode node) {
    if (node instanceof ParentSoyNode<?>) {
      visitChildren((ParentSoyNode<?>) node);
    }
  }
}