/*
 * 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.solr.common.params;

import java.io.IOException;
import java.io.Serializable;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import org.apache.solr.client.solrj.util.ClientUtils;
import org.apache.solr.common.MapWriter;
import org.apache.solr.common.SolrException;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.common.util.SimpleOrderedMap;
import org.apache.solr.common.util.StrUtils;

/**
 * SolrParams is designed to hold parameters to Solr, often from the request coming into Solr.
 * It's basically a MultiMap of String keys to one or more String values.  Neither keys nor values may be null.
 * Unlike a general Map/MultiMap, the size is unknown without iterating over each parameter name.
 */
public abstract class SolrParams implements Serializable, MapWriter, Iterable<Map.Entry<String, String[]>> {

  /**
   * Returns the first String value of a param, or null if not set.
   * To get all, call {@link #getParams(String)} instead.
   */
  public abstract String get(String param);

  /** returns an array of the String values of a param, or null if no mapping for the param exists. */
  public abstract String[] getParams(String param);

  /**
   * Returns an Iterator over the parameter names.
   * If you were to call a getter for this parameter, you should get a non-null value.
   * Since you probably want the value, consider using Java 5 for-each style instead for convenience since a SolrParams
   * implements {@link Iterable}.
   */
  public abstract Iterator<String> getParameterNamesIterator();

  /** returns the value of the param, or def if not set */
  public String get(String param, String def) {
    String val = get(param);
    return val==null ? def : val;
  }

  @Override
  public void writeMap(EntryWriter ew) throws IOException {
    //TODO don't call toNamedList; more efficiently implement here
    //note: multiple values, if present, are a String[] under 1 key
    toNamedList().forEach((k, v) -> {
      if (v == null || "".equals(v)) return;
      try {
        ew.put(k, v);
      } catch (IOException e) {
        throw new RuntimeException("Error serializing", e);
      }
    });
  }

  /** Returns an Iterator of {@code Map.Entry} providing a multi-map view.  Treat it as read-only. */
  @Override
  public Iterator<Map.Entry<String, String[]>> iterator() {
    Iterator<String> it = getParameterNamesIterator();
    return new Iterator<Map.Entry<String, String[]>>() {
      @Override
      public boolean hasNext() {
        return it.hasNext();
      }
      @Override
      public Map.Entry<String, String[]> next() {
        String key = it.next();
        return new Map.Entry<String, String[]>() {
          @Override
          public String getKey() {
            return key;
          }

          @Override
          public String[] getValue() {
            return getParams(key);
          }

          @Override
          public String[] setValue(String[] newValue) {
            throw new UnsupportedOperationException("read-only");
          }

          @Override
          public String toString() {
            return getKey() + "=" + Arrays.toString(getValue());
          }
        };
      }
    };
  }

  /** A {@link Stream} view over {@link #iterator()} -- for convenience.  Treat it as read-only. */
  public Stream<Map.Entry<String, String[]>> stream() {
    return StreamSupport.stream(spliterator(), false);
  }
  // Do we add Map.forEach equivalent too?  But it eager-fetches the value, and Iterable<Map.Entry> allows the user
  //  to only get the value when needed.

  /** returns a RequiredSolrParams wrapping this */
  public RequiredSolrParams required()
  {
    // TODO? should we want to stash a reference?
    return new RequiredSolrParams(this);
  }

  protected String fpname(String field, String param) {
    return "f."+field+'.'+param;
  }

  /** returns the String value of the field parameter, "f.field.param", or
   *  the value for "param" if that is not set.
   */
  public String getFieldParam(String field, String param) {
    String val = get(fpname(field,param));
    return val!=null ? val : get(param);
  }

  /** returns the String value of the field parameter, "f.field.param", or
   *  the value for "param" if that is not set.  If that is not set, def
   */
  public String getFieldParam(String field, String param, String def) {
    String val = get(fpname(field,param));
    return val!=null ? val : get(param, def);
  }

  /** returns the String values of the field parameter, "f.field.param", or
   *  the values for "param" if that is not set.
   */
  public String[] getFieldParams(String field, String param) {
    String[] val = getParams(fpname(field,param));
    return val!=null ? val : getParams(param);
  }

  /** 
   * Returns the Boolean value of the param, or null if not set. 
   * Use this method only when you want to be explicit 
   * about absence of a value (<code>null</code>) vs the default value <code>false</code>.  
   * @see #getBool(String, boolean) 
   * @see #getPrimitiveBool(String) 
   *  
   **/
  
  public Boolean getBool(String param) {
    String val = get(param);
    return val==null ? null : StrUtils.parseBool(val);
  }
  
  /** Returns the boolean value of the param, or <code>false</code> if not set */
  public boolean getPrimitiveBool(String param) {
    return getBool(param, false);
  }

  /** Returns the boolean value of the param, or def if not set */
  public boolean getBool(String param, boolean def) {
    String val = get(param);
    return val==null ? def : StrUtils.parseBool(val);
  }

  /** 
   * Returns the Boolean value of the field param,
   * or the value for param, or null if neither is set. 
   * Use this method only when you want to be explicit 
   * about absence of a value (<code>null</code>) vs the default value <code>false</code>.  
   * @see #getFieldBool(String, String, boolean) 
   * @see #getPrimitiveFieldBool(String, String)    
   **/
  public Boolean getFieldBool(String field, String param) {
    String val = getFieldParam(field, param);
    return val==null ? null : StrUtils.parseBool(val);
  }
  
  /**
   * Returns the boolean value of the field param, or
   * the value for param or 
   * the default value of boolean - <code>false</code> 
   */
  public boolean getPrimitiveFieldBool(String field, String param) {
    return getFieldBool(field, param, false);
  }

  /** 
   * Returns the boolean value of the field param,
   * or the value for param, or def if neither is set. 
   * 
   * */
  public boolean getFieldBool(String field, String param, boolean def) {
    String val = getFieldParam(field, param);
    return val==null ? def : StrUtils.parseBool(val);
  }

  /** 
   * Returns the Integer value of the param, or null if not set 
   * Use this method only when you want to be explicit 
   * about absence of a value (<code>null</code>) vs the default value for int -
   * zero (<code>0</code>).  
   * @see #getInt(String, int) 
   * @see #getPrimitiveInt(String) 
   * */
  public Integer getInt(String param) {
    String val = get(param);
    try {
      return val==null ? null : Integer.valueOf(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }
  
  /**
   * Returns int value of the the param or 
   * default value for int - zero (<code>0</code>) if not set. 
   */
  public int getPrimitiveInt(String param) {
    return getInt(param, 0);
  }

  /** Returns the int value of the param, or def if not set */
  public int getInt(String param, int def) {
    String val = get(param);
    try {
      return val == null ? def : Integer.parseInt(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }

  /** 
   * Returns the Long value of the param, or null if not set 
   * Use this method only when you want to be explicit 
   * about absence of a value (<code>null</code>) vs the default value zero (<code>0</code>).  
   * @see #getLong(String, long) 
   *
   **/
  public Long getLong(String param) {
    String val = get(param);
    try {
      return val == null ? null : Long.valueOf(val);
    } catch (Exception ex) {
      throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex);
    }
  }

  /** Returns the long value of the param, or def if not set */
  public long getLong(String param, long def) {
    String val = get(param);
    try {
      return val == null ? def : Long.parseLong(val);
    } catch (Exception ex) {
      throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex);
    }
  }


  /**
   * Use this method only when you want to be explicit 
   * about absence of a value (<code>null</code>) vs the default value zero (<code>0</code>).
   * 
   * @return The int value of the field param, or the value for param
   * or <code>null</code> if neither is set.
   *   
   * @see #getFieldInt(String, String, int) 
   **/
  public Integer getFieldInt(String field, String param) {
    String val = getFieldParam(field, param);
    try {
      return val==null ? null : Integer.valueOf(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }

  /** Returns the int value of the field param,
  or the value for param, or def if neither is set. */
  public int getFieldInt(String field, String param, int def) {
    String val = getFieldParam(field, param);
    try {
      return val==null ? def : Integer.parseInt(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }


  /** 
   * Returns the Float value of the param, or null if not set 
   * Use this method only when you want to be explicit 
   * about absence of a value (<code>null</code>) vs the default value zero (<code>0.0f</code>).
   * @see #getFloat(String, float)
   **/
  public Float getFloat(String param) {
    String val = get(param);
    try {
      return val==null ? null : Float.valueOf(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }

  /** Returns the float value of the param, or def if not set */
  public float getFloat(String param, float def) {
    String val = get(param);
    try {
      return val==null ? def : Float.parseFloat(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }

  /** 
   * Returns the Float value of the param, or null if not set 
   * Use this method only when you want to be explicit 
   * about absence of a value (<code>null</code>) vs the default value zero (<code>0.0d</code>).
   * @see #getDouble(String, double)
   *
   **/
  public Double getDouble(String param) {
    String val = get(param);
    try {
      return val==null ? null : Double.valueOf(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }

  /** Returns the float value of the param, or def if not set */
  public double getDouble(String param, double def) {
    String val = get(param);
    try {
      return val==null ? def : Double.parseDouble(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }


  /** 
   * Returns the float value of the field param. 
   * Use this method only when you want to be explicit 
   * about absence of a value (<code>null</code>) vs the default value zero (<code>0.0f</code>).
   * 
   * @see #getFieldFloat(String, String, float)
   * @see #getPrimitiveFieldFloat(String, String)
   * 
   **/
  public Float getFieldFloat(String field, String param) {
    String val = getFieldParam(field, param);
    try {
      return val==null ? null : Float.valueOf(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }
  
  /**
   * Returns the float value of the field param or
   * the value for param or 
   * the default value for float - zero (<code>0.0f</code>)   
   */
  public float getPrimitiveFieldFloat(String field, String param) {
    return getFieldFloat(field, param, 0.0f);
  }

  /** Returns the float value of the field param,
  or the value for param, or def if neither is set. */
  public float getFieldFloat(String field, String param, float def) {
    String val = getFieldParam(field, param);
    try {
      return val==null ? def : Float.parseFloat(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }

  /** 
   * Returns the float value of the field param. 
   * Use this method only when you want to be explicit 
   * about absence of a value (<code>null</code>) vs the default value zero (<code>0.0d</code>).
   * @see #getDouble(String, double)
   *
   **/
  public Double getFieldDouble(String field, String param) {
    String val = getFieldParam(field, param);
    try {
      return val==null ? null : Double.valueOf(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }

  /** Returns the float value of the field param,
  or the value for param, or def if neither is set. */
  public double getFieldDouble(String field, String param, double def) {
    String val = getFieldParam(field, param);
    try {
      return val==null ? def : Double.parseDouble(val);
    }
    catch( Exception ex ) {
      throw new SolrException( SolrException.ErrorCode.BAD_REQUEST, ex.getMessage(), ex );
    }
  }

  public static SolrParams wrapDefaults(SolrParams params, SolrParams defaults) {
    if (params == null)
      return defaults;
    if (defaults == null)
      return params;
    return new DefaultSolrParams(params,defaults);
  }

  public static SolrParams wrapAppended(SolrParams params, SolrParams defaults) {
    if (params == null)
      return defaults;
    if (defaults == null)
      return params;
    return AppendedSolrParams.wrapAppended(params,defaults);
  }

  /** Create a Map&lt;String,String&gt; from a NamedList given no keys are repeated */
  @Deprecated // Doesn't belong here (no SolrParams).  Just remove.
  public static Map<String,String> toMap(NamedList params) {
    HashMap<String,String> map = new HashMap<>();
    for (int i=0; i<params.size(); i++) {
      map.put(params.getName(i), params.getVal(i).toString());
    }
    return map;
  }

  /** Create a Map&lt;String,String[]&gt; from a NamedList */
  @Deprecated // Doesn't belong here (no SolrParams).  Just remove.
  public static Map<String,String[]> toMultiMap(NamedList params) {
    HashMap<String,String[]> map = new HashMap<>();
    for (int i=0; i<params.size(); i++) {
      String name = params.getName(i);
      Object val = params.getVal(i);
      if (val instanceof String[]) {
        MultiMapSolrParams.addParam(name, (String[]) val, map);
      } else if (val instanceof List) {
        List l = (List) val;
        String[] s = new String[l.size()];
        for (int j = 0; j < l.size(); j++) {
          s[j] = l.get(j) == null ? null : String.valueOf(l.get(j));
        }
        MultiMapSolrParams.addParam(name, s, map);
      } else {
        MultiMapSolrParams.addParam(name, val.toString(), map);
      }
    }
    return map;
  }

  /**
   * Create SolrParams from NamedList.
   * @deprecated Use {@link NamedList#toSolrParams()}.
   */
  @Deprecated //move to NamedList to allow easier flow
  public static SolrParams toSolrParams(NamedList params) {
    return params.toSolrParams();
  }

  @Deprecated
  public SolrParams toFilteredSolrParams(List<String> names) {
    // TODO do this better somehow via a view that filters?  See SolrCore.preDecorateResponse.
    //   ... and/or add some optional predicates to iterator()?
    NamedList<String> nl = new NamedList<>();
    for (Iterator<String> it = getParameterNamesIterator(); it.hasNext();) {
      final String name = it.next();
      if (names.contains(name)) {
        final String[] values = getParams(name);
        for (String value : values) {
          nl.add(name, value);
        }
      }
    }
    return nl.toSolrParams();
  }

  /**
   * Convert this to a NamedList of unique keys with either String or String[] values depending on
   * how many values there are for the parameter.
   */
  public NamedList<Object> toNamedList() {
    final SimpleOrderedMap<Object> result = new SimpleOrderedMap<>();

    for(Iterator<String> it=getParameterNamesIterator(); it.hasNext(); ) {
      final String name = it.next();
      final String [] values = getParams(name);
      if(values.length==1) {
        result.add(name,values[0]);
      } else {
        // currently no reason not to use the same array
        result.add(name,values);
      }
    }
    return result;
  }

  // Deprecated because there isn't a universal way to deal with multi-values (always
  //  String[] or only for > 1 or always 1st value).  And what to do with nulls or empty string.
  //  And SolrParams now implements MapWriter.toMap(Map) (a default method).  So what do we do?
  @Deprecated
  public Map<String, Object> getAll(Map<String, Object> sink, Collection<String> params) {
    if (sink == null) sink = new LinkedHashMap<>();
    for (String param : params) {
      String[] v = getParams(param);
      if (v != null && v.length > 0) {
        if (v.length == 1) {
          sink.put(param, v[0]);
        } else {
          sink.put(param, v);
        }
      }
    }
    return sink;
  }


  /**Copy all params to the given map or if the given map is null
   * create a new one
   */
  @Deprecated
  public Map<String, Object> getAll(Map<String, Object> sink, String... params){
    return getAll(sink, params == null ? Collections.emptyList() : Arrays.asList(params));
  }
  
  /** Returns this SolrParams as a properly URL encoded string, starting with {@code "?"}, if not empty. */
  public String toQueryString() {
    try {
      final String charset = StandardCharsets.UTF_8.name();
      final StringBuilder sb = new StringBuilder(128);
      boolean first = true;
      for (final Iterator<String> it = getParameterNamesIterator(); it.hasNext();) {
        final String name = it.next(), nameEnc = URLEncoder.encode(name, charset);
        for (String val : getParams(name)) {
          sb.append(first ? '?' : '&').append(nameEnc).append('=').append(URLEncoder.encode(val, charset));
          first = false;
        }
      }
      return sb.toString();
    } catch (UnsupportedEncodingException e) {
      // impossible!
      throw new AssertionError(e);
    }
  }

  /**
   * Generates a local-params string of the form <pre>{! name=value name2=value2}</pre>.
   */
  public String toLocalParamsString() {
    final StringBuilder sb = new StringBuilder(128);
    sb.append("{!");
    //TODO perhaps look for 'type' and add here?  but it doesn't matter.
    for (final Iterator<String> it = getParameterNamesIterator(); it.hasNext();) {
      final String name = it.next();
      for (String val : getParams(name)) {
        sb.append(' '); // do so even the first time; why not.
        sb.append(name); // no escaping for name; it must follow "Java Identifier" rules.
        sb.append('=');
        sb.append(ClientUtils.encodeLocalParamVal(val));
      }
    }
    sb.append('}');
    return sb.toString();
  }

  /** Like {@link #toQueryString()}, but only replacing enough chars so that
   * the URL may be unambiguously pasted back into a browser.
   * This method can be used to properly log query parameters without
   * making them unreadable.
   * <p>
   * Characters with a numeric value less than 32 are encoded.
   * &amp;,=,%,+,space are encoded.
   */
  @Override
  public String toString() {
    final StringBuilder sb = new StringBuilder(128);
    try {
      boolean first=true;
      for (final Iterator<String> it = getParameterNamesIterator(); it.hasNext();) {
        final String name = it.next();
        for (String val : getParams(name)) {
          if (!first) sb.append('&');
          first=false;
          StrUtils.partialURLEncodeVal(sb, name);
          sb.append('=');
          StrUtils.partialURLEncodeVal(sb, val);
        }
      }
      return sb.toString();
    } catch (IOException e) {
      // impossible!
      throw new AssertionError(e);
    }
  }

}
