/*
    *    Copyright 2015-2023 the original author or authors.
    *
    *    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
    *
    *       https://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.mybatis.scripting.freemarker;
  
  import java.io.CharArrayWriter;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.ibatis.builder.SqlSourceBuilder;
  import org.apache.ibatis.mapping.BoundSql;
  import org.apache.ibatis.mapping.SqlSource;
  import org.apache.ibatis.session.Configuration;
  
  import freemarker.template.SimpleScalar;
  import freemarker.template.Template;
  import freemarker.template.TemplateException;
  import freemarker.template.Version;
  
  /**
   * Applies provided parameter(s) to FreeMarker template. Then passes the result into default MyBatis engine (and it
   * finally replaces #{}-params to '?'-params). So, FreeMarker is used as preprocessor for MyBatis engine.
   *
   * @author elwood
   */
  public class FreeMarkerSqlSource implements SqlSource {
    private final Template template;
    private final Configuration configuration;
    private final Version incompatibleImprovementsVersion;
    private final String databaseId;
  
    public static final String GENERATED_PARAMS_KEY = "__GENERATED__";
  
    public FreeMarkerSqlSource(Template template, Configuration configuration, Version incompatibleImprovementsVersion) {
      this.template = template;
      this.configuration = configuration;
      this.incompatibleImprovementsVersion = incompatibleImprovementsVersion;
      this.databaseId = configuration.getDatabaseId();
    }
  
    /**
     * Populates additional parameters to data context. Data context can be {@link java.util.Map} or
     * {@link org.mybatis.scripting.freemarker.ParamObjectAdapter} instance.
     */
    protected Object preProcessDataContext(Object dataContext, boolean isMap) {
      if (isMap) {
        ((Map<String, Object>) dataContext).put(MyBatisParamDirective.DEFAULT_KEY, new MyBatisParamDirective());
        ((Map<String, Object>) dataContext).put(MyBatisParamDirective.DATABASE_ID_KEY, new SimpleScalar(this.databaseId));
      } else {
        ((ParamObjectAdapter) dataContext).putAdditionalParam(MyBatisParamDirective.DEFAULT_KEY,
            new MyBatisParamDirective());
        ((ParamObjectAdapter) dataContext).putAdditionalParam(MyBatisParamDirective.DATABASE_ID_KEY,
            new SimpleScalar(this.databaseId));
      }
      return dataContext;
    }
  
    @Override
    public BoundSql getBoundSql(Object parameterObject) {
      // Add to passed parameterObject our predefined directive - MyBatisParamDirective
      // It will be available as "p" inside templates
      Object dataContext;
      ArrayList generatedParams = new ArrayList<>();
      if (parameterObject != null) {
        if (parameterObject instanceof Map) {
          HashMap<String, Object> map = new HashMap<>((Map<String, Object>) parameterObject);
          map.put(GENERATED_PARAMS_KEY, generatedParams);
          dataContext = preProcessDataContext(map, true);
        } else {
          ParamObjectAdapter adapter = new ParamObjectAdapter(parameterObject, generatedParams,
              incompatibleImprovementsVersion);
          dataContext = preProcessDataContext(adapter, false);
        }
      } else {
        HashMap<Object, Object> map = new HashMap<>();
        map.put(GENERATED_PARAMS_KEY, generatedParams);
        dataContext = preProcessDataContext(map, true);
      }
  
      CharArrayWriter writer = new CharArrayWriter();
      try {
        template.process(dataContext, writer);
      } catch (TemplateException | IOException e) {
        throw new RuntimeException(e);
      }
 
     // We got SQL ready for MyBatis here. This SQL contains
     // params declarations like "#{param}",
     // they will be replaced to '?' by MyBatis engine further
     String sql = writer.toString();
 
     if (!generatedParams.isEmpty()) {
       if (!(parameterObject instanceof Map)) {
         throw new UnsupportedOperationException("Auto-generated prepared statements parameters"
             + " are not available if using parameters object. Use @Param-annotated parameters" + " instead.");
       }
 
       Map<String, Object> parametersMap = (Map<String, Object>) parameterObject;
       for (int i = 0; i < generatedParams.size(); i++) {
         parametersMap.put("_p" + i, generatedParams.get(i));
       }
     }
 
     // Pass retrieved SQL into MyBatis engine, it will substitute prepared-statements parameters
     SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
     Class<?> parameterType1 = parameterObject == null ? Object.class : parameterObject.getClass();
     SqlSource sqlSource = sqlSourceParser.parse(sql, parameterType1, new HashMap<String, Object>());
     return sqlSource.getBoundSql(parameterObject);
   }
 }