/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you 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 org.apache.calcite.sql.fun;

import org.apache.calcite.linq4j.Ord;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.sql.SqlCall;
import org.apache.calcite.sql.SqlCallBinding;
import org.apache.calcite.sql.SqlCharStringLiteral;
import org.apache.calcite.sql.SqlCollation;
import org.apache.calcite.sql.SqlKind;
import org.apache.calcite.sql.SqlLiteral;
import org.apache.calcite.sql.SqlNode;
import org.apache.calcite.sql.SqlOperatorBinding;
import org.apache.calcite.sql.SqlSpecialOperator;
import org.apache.calcite.sql.SqlUtil;
import org.apache.calcite.sql.SqlWriter;
import org.apache.calcite.sql.parser.SqlParserPos;
import org.apache.calcite.sql.type.InferTypes;
import org.apache.calcite.sql.type.OperandTypes;
import org.apache.calcite.sql.type.ReturnTypes;
import org.apache.calcite.sql.type.SqlTypeName;
import org.apache.calcite.sql.type.SqlTypeUtil;
import org.apache.calcite.sql.validate.SqlValidator;
import org.apache.calcite.sql.validate.SqlValidatorScope;
import org.apache.calcite.util.BitString;
import org.apache.calcite.util.NlsString;
import org.apache.calcite.util.Util;

import java.util.List;

import static org.apache.calcite.linq4j.Nullness.castNonNull;
import static org.apache.calcite.util.Static.RESOURCE;

/**
 * Internal operator, by which the parser represents a continued string literal.
 *
 * <p>The string fragments are {@link SqlLiteral} objects, all of the same type,
 * collected as the operands of an {@link SqlCall} using this operator. After
 * validation, the fragments will be concatenated into a single literal.
 *
 * <p>For a chain of {@link org.apache.calcite.sql.SqlCharStringLiteral}
 * objects, a {@link SqlCollation} object is attached only to the head of the
 * chain.
 */
public class SqlLiteralChainOperator extends SqlSpecialOperator {
  //~ Constructors -----------------------------------------------------------

  SqlLiteralChainOperator() {
    super(
        "$LiteralChain",
        SqlKind.LITERAL_CHAIN,
        80,
        true,

        // precedence tighter than the * and || operators
        ReturnTypes.ARG0,
        InferTypes.FIRST_KNOWN,
        OperandTypes.VARIADIC);
  }

  //~ Methods ----------------------------------------------------------------

  // all operands must be the same type
  private static boolean argTypesValid(SqlCallBinding callBinding) {
    if (callBinding.getOperandCount() < 2) {
      return true; // nothing to compare
    }
    RelDataType firstType = null;
    for (Ord<SqlNode> operand : Ord.zip(callBinding.operands())) {
      RelDataType type = SqlTypeUtil.deriveType(callBinding, operand.e);
      if (operand.i == 0) {
        firstType = type;
      } else if (!SqlTypeUtil.sameNamedType(castNonNull(firstType), type)) {
        return false;
      }
    }
    return true;
  }

  @Override public boolean checkOperandTypes(
      SqlCallBinding callBinding,
      boolean throwOnFailure) {
    if (!argTypesValid(callBinding)) {
      if (throwOnFailure) {
        throw callBinding.newValidationSignatureError();
      }
      return false;
    }
    return true;
  }

  // Result type is the same as all the args, but its size is the
  // total size.
  // REVIEW mb 8/8/04: Possibly this can be achieved by combining
  // the strategy useFirstArgType with a new transformer.
  @Override public RelDataType inferReturnType(
      SqlOperatorBinding opBinding) {
    // Here we know all the operands have the same type,
    // which has a size (precision), but not a scale.
    RelDataType ret = opBinding.getOperandType(0);
    SqlTypeName typeName = ret.getSqlTypeName();
    assert typeName.allowsPrecNoScale()
        : "LiteralChain has impossible operand type "
        + typeName;
    int size = 0;
    for (RelDataType type : opBinding.collectOperandTypes()) {
      size += type.getPrecision();
      assert type.getSqlTypeName() == typeName;
    }
    return opBinding.getTypeFactory().createSqlType(typeName, size);
  }

  @Override public String getAllowedSignatures(String opName) {
    return opName + "(...)";
  }

  @Override public void validateCall(
      SqlCall call,
      SqlValidator validator,
      SqlValidatorScope scope,
      SqlValidatorScope operandScope) {
    // per the SQL std, each string fragment must be on a different line
    final List<SqlNode> operandList = call.getOperandList();
    for (int i = 1; i < operandList.size(); i++) {
      SqlParserPos prevPos = operandList.get(i - 1).getParserPosition();
      final SqlNode operand = operandList.get(i);
      SqlParserPos pos = operand.getParserPosition();
      if (pos.getLineNum() <= prevPos.getLineNum()) {
        throw validator.newValidationError(operand,
            RESOURCE.stringFragsOnSameLine());
      }
    }
  }

  @Override public void unparse(
      SqlWriter writer,
      SqlCall call,
      int leftPrec,
      int rightPrec) {
    final SqlWriter.Frame frame = writer.startList("", "");
    SqlCollation collation = null;
    for (Ord<SqlNode> operand : Ord.zip(call.getOperandList())) {
      SqlLiteral rand = (SqlLiteral) operand.e;
      if (operand.i > 0) {
        // SQL:2003 says there must be a newline between string
        // fragments.
        writer.newlineAndIndent();
      }
      if (rand instanceof SqlCharStringLiteral) {
        final NlsString nls = rand.getValueAs(NlsString.class);
        if (operand.i == 0) {
          collation = nls.getCollation();

          // print with prefix
          writer.literal(nls.asSql(true, false, writer.getDialect()));
        } else {
          // print without prefix
          writer.literal(nls.asSql(false, false, writer.getDialect()));
        }
      } else if (operand.i == 0) {
        // print with prefix
        rand.unparse(writer, leftPrec, rightPrec);
      } else {
        // print without prefix
        if (rand.getTypeName() == SqlTypeName.BINARY) {
          BitString bs = rand.getValueAs(BitString.class);
          writer.literal("'" + bs.toHexString() + "'");
        } else {
          writer.literal("'" + rand.toValue() + "'");
        }
      }
    }
    if (collation != null) {
      collation.unparse(writer);
    }
    writer.endList(frame);
  }

  /**
   * Concatenates the operands of a call to this operator.
   */
  public static SqlLiteral concatenateOperands(SqlCall call) {
    final List<SqlNode> operandList = call.getOperandList();
    assert operandList.size() > 0;
    assert operandList.get(0) instanceof SqlLiteral
        : operandList.get(0).getClass();
    return SqlUtil.concatenateLiterals(
        Util.cast(operandList, SqlLiteral.class));
  }
}
