/*
 * Copyright 2011 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.base.Joiner;
import com.google.common.collect.Iterables;
import com.google.template.soy.basetree.SyntaxVersion;
import com.google.template.soy.error.ErrorReporter;
import com.google.template.soy.error.ErrorReporter.Checkpoint;
import com.google.template.soy.error.SoyErrorKind;
import com.google.template.soy.exprtree.AbstractExprNodeVisitor;
import com.google.template.soy.exprtree.ExprNode;
import com.google.template.soy.exprtree.ExprNode.ParentExprNode;
import com.google.template.soy.exprtree.FunctionNode;
import com.google.template.soy.exprtree.MapLiteralNode;
import com.google.template.soy.exprtree.VarRefNode;
import com.google.template.soy.shared.internal.BuiltinFunction;
import com.google.template.soy.shared.restricted.SoyFunction;
import com.google.template.soy.soytree.AbstractSoyNodeVisitor;
import com.google.template.soy.soytree.ExprUnion;
import com.google.template.soy.soytree.SoyNode;
import com.google.template.soy.soytree.SoyNode.ExprHolderNode;
import com.google.template.soy.soytree.SoyNode.ParentSoyNode;
import com.google.template.soy.soytree.defn.LoopVar;

import java.util.Set;

/**
 * Checks the signatures of functions.
 *
 * <p>Important: Do not use outside of Soy code (treat as superpackage-private).
 *
 */
final class CheckFunctionCallsVisitor extends AbstractSoyNodeVisitor<Void> {

  private static final SoyErrorKind INCORRECT_NUM_ARGS =
      SoyErrorKind.of("Function ''{0}'' called with {1} arguments (expected {2}).");
  private static final SoyErrorKind LOOP_VARIABLE_NOT_IN_SCOPE =
      SoyErrorKind.of("Function ''{0}'' must have a foreach loop variable as its argument.");
  private static final SoyErrorKind QUOTE_KEYS_IF_JS_REQUIRES_MAP_LITERAL_ARG =
      SoyErrorKind.of(
          "Function ''quoteKeysIfJs'' called with argument of type {0} (expected map literal).");
  private static final SoyErrorKind UNKNOWN_FUNCTION = SoyErrorKind.of("Unknown function ''{0}''.");

  private final ErrorReporter errorReporter;

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

  CheckFunctionCallsVisitor(SyntaxVersion declaredSyntaxVersion, ErrorReporter errorReporter) {
    this.errorReporter = errorReporter;
    this.declaredSyntaxVersion = declaredSyntaxVersion;
  }


  /**
   * Recursively identifies all Soy nodes that contain expressions, and recurse to
   * each expression.
   */
  @Override protected void visitSoyNode(SoyNode node) {

    if (node instanceof ExprHolderNode) {

      for (ExprUnion exprUnion : ((ExprHolderNode) node).getAllExprUnions()) {
        if (exprUnion.getExpr() == null) {
          continue;
        }
        new CheckFunctionCallsExprVisitor().exec(exprUnion.getExpr());
      }
    }

    if (node instanceof ParentSoyNode<?>) {
      visitChildren((ParentSoyNode<?>) node);
    }
  }


  /**
   * Used to visit expr nodes to find nonplugin functions and check their signatures.
   */
  private final class CheckFunctionCallsExprVisitor extends AbstractExprNodeVisitor<Void> {

    /**
     * Recurse to children.
     */
    @Override protected void visitExprNode(ExprNode node) {
      if (node instanceof ParentExprNode) {
        visitChildren((ParentExprNode) node);
      }
    }

    /** Check the function signature. */
    @Override protected void visitFunctionNode(FunctionNode node) {
      String fnName = node.getFunctionName();
      SoyFunction function = node.getSoyFunction();
      if (function == null) {
        if (declaredSyntaxVersion != SyntaxVersion.V1_0) {
          // In Soy V2, all functions must be available as SoyFunctions at compile time.
          errorReporter.report(node.getSourceLocation(), UNKNOWN_FUNCTION, fnName);
        }
        return;
      }

      Checkpoint checkpoint = errorReporter.checkpoint();
      checkNumArgs(function, node);

      // If there were arity errors, don't run visitNonpluginFunction (it would NPE).
      if (function instanceof BuiltinFunction && !errorReporter.errorsSince(checkpoint)) {
        visitNonpluginFunction((BuiltinFunction) function, node);
      }

      // Recurse to operands.
      visitChildren(node);
    }

    private void visitNonpluginFunction(BuiltinFunction nonpluginFn, FunctionNode node) {
      String fnName = nonpluginFn.getName();
      // Check argument types.
      ExprNode firstChild = Iterables.getFirst(node.getChildren(), null);
      switch (nonpluginFn) {
        case INDEX:
        case IS_FIRST:
        case IS_LAST:
          requireLoopVariableInScope(node, firstChild);
          break;
        case QUOTE_KEYS_IF_JS:
          if (!(firstChild instanceof MapLiteralNode)) {
            errorReporter.report(
                node.getSourceLocation(),
                QUOTE_KEYS_IF_JS_REQUIRES_MAP_LITERAL_ARG,
                node.getChild(0).getType().toString());
          }
          break;
        case CHECK_NOT_NULL:
          // Do nothing.  All types are valid.
          break;
        default:
          throw new AssertionError("Unrecognized nonplugin fn " + fnName);
      }
    }

    private void checkNumArgs(SoyFunction function, FunctionNode node) {
      int numArgs = node.numChildren();
      Set<Integer> arities = function.getValidArgsSizes();
      if (!arities.contains(numArgs)) {
        errorReporter.report(
            node.getSourceLocation(),
            INCORRECT_NUM_ARGS,
            function.getName(),
            numArgs,
            Joiner.on(" or ").join(arities));
      }
    }

    /**
     * @param fn The function that must take a loop variable.
     */
    private void requireLoopVariableInScope(FunctionNode fn, ExprNode loopVariable) {
      if (!(loopVariable instanceof VarRefNode
          && ((VarRefNode) loopVariable).getDefnDecl() instanceof LoopVar)) {
        errorReporter.report(
            fn.getSourceLocation(), LOOP_VARIABLE_NOT_IN_SCOPE, fn.getFunctionName());
      }
    }
  }
}