/***************************************************************************
  qgsvaluerelationfieldformatter.cpp - QgsValueRelationFieldFormatter

 ---------------------
 begin                : 3.12.2016
 copyright            : (C) 2016 by Matthias Kuhn
 email                : matthias@opengis.ch
 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
#include "qgsvaluerelationfieldformatter.h"

#include "qgis.h"
#include "qgsproject.h"
#include "qgsvectorlayer.h"
#include "qgsexpressionnodeimpl.h"
#include "qgsapplication.h"
#include "qgsexpressioncontextutils.h"
#include "qgsvectorlayerref.h"
#include "qgspostgresstringutils.h"
#include "qgsmessagelog.h"

#include <nlohmann/json.hpp>
using namespace nlohmann;

#include <QSettings>

bool orderByKeyLessThan( const QgsValueRelationFieldFormatter::ValueRelationItem &p1, const QgsValueRelationFieldFormatter::ValueRelationItem &p2 )
{
  return qgsVariantLessThan( p1.key, p2.key );
}

bool orderByValueLessThan( const QgsValueRelationFieldFormatter::ValueRelationItem &p1, const QgsValueRelationFieldFormatter::ValueRelationItem &p2 )
{
  return qgsVariantLessThan( p1.value, p2.value );
}

QgsValueRelationFieldFormatter::QgsValueRelationFieldFormatter()
{
  setFlags( flags() | QgsFieldFormatter::CanProvideAvailableValues );
}

QString QgsValueRelationFieldFormatter::id() const
{
  return QStringLiteral( "ValueRelation" );
}

QString QgsValueRelationFieldFormatter::representValue( QgsVectorLayer *layer, int fieldIndex, const QVariantMap &config, const QVariant &cache, const QVariant &value ) const
{
  ValueRelationCache vrCache;

  if ( cache.isValid() )
  {
    vrCache = cache.value<QgsValueRelationFieldFormatter::ValueRelationCache>();
  }
  else
  {
    vrCache = QgsValueRelationFieldFormatter::createCache( config );
  }

  if ( config.value( QStringLiteral( "AllowMulti" ) ).toBool() )
  {
    QStringList keyList;

    if ( layer->fields().at( fieldIndex ).type() == QVariant::Map )
    {
      //because of json it's stored as QVariantList
      keyList = value.toStringList();
    }
    else
    {
      keyList = valueToStringList( value );
    }

    QStringList valueList;

    for ( const QgsValueRelationFieldFormatter::ValueRelationItem &item : qgis::as_const( vrCache ) )
    {
      if ( keyList.contains( item.key.toString() ) )
      {
        valueList << item.value;
      }
    }

    return valueList.join( QLatin1String( ", " ) ).prepend( '{' ).append( '}' );
  }
  else
  {
    if ( value.isNull() )
    {
      return QgsApplication::nullRepresentation();
    }

    for ( const QgsValueRelationFieldFormatter::ValueRelationItem &item : qgis::as_const( vrCache ) )
    {
      if ( item.key == value )
      {
        return item.value;
      }
    }
  }

  return QStringLiteral( "(%1)" ).arg( value.toString() );
}

QVariant QgsValueRelationFieldFormatter::sortValue( QgsVectorLayer *layer, int fieldIndex, const QVariantMap &config, const QVariant &cache, const QVariant &value ) const
{
  return value.isNull() ? QString() : representValue( layer, fieldIndex, config, cache, value );
}

QVariant QgsValueRelationFieldFormatter::createCache( QgsVectorLayer *layer, int fieldIndex, const QVariantMap &config ) const
{
  Q_UNUSED( layer )
  Q_UNUSED( fieldIndex )
  return QVariant::fromValue<ValueRelationCache>( createCache( config ) );

}

QgsValueRelationFieldFormatter::ValueRelationCache QgsValueRelationFieldFormatter::createCache(
  const QVariantMap &config,
  const QgsFeature &formFeature,
  const QgsFeature &parentFormFeature )
{
  ValueRelationCache cache;

  const QgsVectorLayer *layer = resolveLayer( config, QgsProject::instance() );

  if ( !layer )
    return cache;

  QgsFields fields = layer->fields();
  int ki = fields.indexOf( config.value( QStringLiteral( "Key" ) ).toString() );
  int vi = fields.indexOf( config.value( QStringLiteral( "Value" ) ).toString() );

  QgsFeatureRequest request;

  request.setFlags( QgsFeatureRequest::NoGeometry );
  QgsAttributeIds subsetOfAttributes { ki, vi };

  const QString descriptionExpressionString = config.value( "Description" ).toString();
  QgsExpression descriptionExpression( descriptionExpressionString );
  QgsExpressionContext context( QgsExpressionContextUtils::globalProjectLayerScopes( layer ) );
  descriptionExpression.prepare( &context );
  subsetOfAttributes += descriptionExpression.referencedAttributeIndexes( layer->fields() );
  request.setSubsetOfAttributes( qgis::setToList( subsetOfAttributes ) );

  const QString filterExpression = config.value( QStringLiteral( "FilterExpression" ) ).toString();

  // Skip the filter and build a full cache if the form scope is required and the feature
  // is not valid or the attributes required for the filter have no valid value
  // Note: parent form scope is not checked for usability because it's supposed to
  //       be used into a coalesce that retrieve the current value of the parent
  //       from the parent layer when used outside of an embedded form
  if ( ! filterExpression.isEmpty() && ( !( expressionRequiresFormScope( filterExpression ) )
                                         || expressionIsUsable( filterExpression, formFeature ) ) )
  {
    QgsExpressionContext filterContext = context;
    if ( formFeature.isValid( ) && QgsValueRelationFieldFormatter::expressionRequiresFormScope( filterExpression ) )
      filterContext.appendScope( QgsExpressionContextUtils::formScope( formFeature ) );
    if ( parentFormFeature.isValid() && QgsValueRelationFieldFormatter::expressionRequiresParentFormScope( filterExpression ) )
      filterContext.appendScope( QgsExpressionContextUtils::parentFormScope( parentFormFeature ) );
    request.setExpressionContext( filterContext );
    request.setFilterExpression( filterExpression );
  }

  QgsFeatureIterator fit = layer->getFeatures( request );

  QgsFeature f;
  while ( fit.nextFeature( f ) )
  {
    QString description;
    if ( descriptionExpression.isValid() )
    {
      context.setFeature( f );
      description = descriptionExpression.evaluate( &context ).toString();
    }
    cache.append( ValueRelationItem( f.attribute( ki ), f.attribute( vi ).toString(), description ) );
  }

  if ( config.value( QStringLiteral( "OrderByValue" ) ).toBool() )
  {
    std::sort( cache.begin(), cache.end(), orderByValueLessThan );
  }
  else
  {
    std::sort( cache.begin(), cache.end(), orderByKeyLessThan );
  }

  return cache;
}


QList<QgsVectorLayerRef> QgsValueRelationFieldFormatter::layerDependencies( const QVariantMap &config ) const
{
  QList<QgsVectorLayerRef> result;
  const QString layerId { config.value( QStringLiteral( "Layer" ) ).toString() };
  const QString layerName { config.value( QStringLiteral( "LayerName" ) ).toString() };
  const QString providerName { config.value( QStringLiteral( "LayerProviderName" ) ).toString() };
  const QString layerSource { config.value( QStringLiteral( "LayerSource" ) ).toString() };
  if ( ! layerId.isEmpty() && ! layerName.isEmpty() && ! providerName.isEmpty() && ! layerSource.isEmpty() )
  {
    result.append( QgsVectorLayerRef( layerId, layerName, layerSource, providerName ) );
  }
  return result;
}

QVariantList QgsValueRelationFieldFormatter::availableValues( const QVariantMap &config, int countLimit, const QgsFieldFormatterContext &context ) const
{
  QVariantList values;

  if ( auto *lProject = context.project() )
  {
    const QgsVectorLayer *referencedLayer = qobject_cast<QgsVectorLayer *>( lProject->mapLayer( config[QStringLiteral( "Layer" )].toString() ) );
    if ( referencedLayer )
    {
      int fieldIndex = referencedLayer->fields().indexOf( config.value( QStringLiteral( "Key" ) ).toString() );
      values = qgis::setToList( referencedLayer->uniqueValues( fieldIndex, countLimit ) );
    }
  }
  return values;
}

QStringList QgsValueRelationFieldFormatter::valueToStringList( const QVariant &value )
{
  QStringList checkList;
  if ( value.type() == QVariant::StringList )
  {
    checkList = value.toStringList();
  }
  else
  {
    QVariantList valuesList;
    if ( value.type() == QVariant::String )
    {
      // This must be an array representation
      auto newVal { value };
      if ( newVal.toString().trimmed().startsWith( '{' ) )
      {
        //normal case
        valuesList = QgsPostgresStringUtils::parseArray( newVal.toString() );
      }
      else if ( newVal.toString().trimmed().startsWith( '[' ) )
      {
        //fallback, in case it's a json array
        try
        {
          for ( auto &element : json::parse( newVal.toString().toStdString() ) )
          {
            if ( element.is_number_integer() )
            {
              valuesList.push_back( element.get<int>() );
            }
            else if ( element.is_number_unsigned() )
            {
              valuesList.push_back( element.get<unsigned>() );
            }
            else if ( element.is_string() )
            {
              valuesList.push_back( QString::fromStdString( element.get<std::string>() ) );
            }
          }
        }
        catch ( json::parse_error &ex )
        {
          QgsMessageLog::logMessage( QObject::tr( "Cannot parse JSON like string '%1' Error: %2" ).arg( newVal.toString(), ex.what() ) );
        }
      }
    }
    else if ( value.type() == QVariant::List )
    {
      valuesList = value.toList( );
    }

    checkList.reserve( valuesList.size() );
    for ( const QVariant &listItem : qgis::as_const( valuesList ) )
    {
      QString v( listItem.toString( ) );
      if ( ! v.isEmpty() )
        checkList.append( v );
    }
  }
  return checkList;
}


QSet<QString> QgsValueRelationFieldFormatter::expressionFormVariables( const QString &expression )
{
  std::unique_ptr< QgsExpressionContextScope > scope( QgsExpressionContextUtils::formScope() );
  QSet< QString > formVariables = qgis::listToSet( scope->variableNames() );
  const QSet< QString > usedVariables = QgsExpression( expression ).referencedVariables();
  formVariables.intersect( usedVariables );
  return formVariables;
}

QSet<QString> QgsValueRelationFieldFormatter::expressionParentFormVariables( const QString &expression )
{
  std::unique_ptr< QgsExpressionContextScope > scope( QgsExpressionContextUtils::parentFormScope() );
  QSet< QString > formVariables = qgis::listToSet( scope->variableNames() );
  const QSet< QString > usedVariables = QgsExpression( expression ).referencedVariables();
  formVariables.intersect( usedVariables );
  return formVariables;
}

bool QgsValueRelationFieldFormatter::expressionRequiresFormScope( const QString &expression )
{
  return !( expressionFormAttributes( expression ).isEmpty() && expressionFormVariables( expression ).isEmpty() );
}

bool QgsValueRelationFieldFormatter::expressionRequiresParentFormScope( const QString &expression )
{
  return !( expressionParentFormAttributes( expression ).isEmpty() && expressionParentFormVariables( expression ).isEmpty() );
}

QSet<QString> QgsValueRelationFieldFormatter::expressionParentFormAttributes( const QString &expression )
{
  QSet<QString> attributes;
  QgsExpression exp( expression );
  std::unique_ptr< QgsExpressionContextScope > scope( QgsExpressionContextUtils::parentFormScope() );
  // List of form function names used in the expression
  const QSet<QString> formFunctions( qgis::listToSet( scope->functionNames() )
                                     .intersect( exp.referencedFunctions( ) ) );
  const QList<const QgsExpressionNodeFunction *> expFunctions( exp.findNodes<QgsExpressionNodeFunction>() );
  QgsExpressionContext context;
  for ( const auto &f : expFunctions )
  {
    QgsExpressionFunction *fd = QgsExpression::QgsExpression::Functions()[f->fnIndex()];
    if ( formFunctions.contains( fd->name( ) ) )
    {
      for ( const auto &param : f->args( )->list() )
      {
        attributes.insert( param->eval( &exp, &context ).toString() );
      }
    }
  }
  return attributes;
}

QSet<QString> QgsValueRelationFieldFormatter::expressionFormAttributes( const QString &expression )
{
  QSet<QString> attributes;
  QgsExpression exp( expression );
  std::unique_ptr< QgsExpressionContextScope > scope( QgsExpressionContextUtils::formScope() );
  // List of form function names used in the expression
  const QSet<QString> formFunctions( qgis::listToSet( scope->functionNames() )
                                     .intersect( exp.referencedFunctions( ) ) );
  const QList<const QgsExpressionNodeFunction *> expFunctions( exp.findNodes<QgsExpressionNodeFunction>() );
  QgsExpressionContext context;
  for ( const auto &f : expFunctions )
  {
    QgsExpressionFunction *fd = QgsExpression::QgsExpression::Functions()[f->fnIndex()];
    if ( formFunctions.contains( fd->name( ) ) )
    {
      for ( const auto &param : f->args( )->list() )
      {
        attributes.insert( param->eval( &exp, &context ).toString() );
      }
    }
  }
  return attributes;
}

bool QgsValueRelationFieldFormatter::expressionIsUsable( const QString &expression,
    const QgsFeature &feature,
    const QgsFeature &parentFeature )
{
  const QSet<QString> attrs = expressionFormAttributes( expression );
  for ( auto it = attrs.constBegin() ; it != attrs.constEnd(); it++ )
  {
    if ( ! feature.attribute( *it ).isValid() )
      return false;
  }

  if ( ! expressionFormVariables( expression ).isEmpty() && feature.geometry().isEmpty( ) )
    return false;

  if ( parentFeature.isValid() )
  {
    const QSet<QString> parentAttrs = expressionParentFormAttributes( expression );
    for ( auto it = parentAttrs.constBegin() ; it != parentAttrs.constEnd(); it++ )
    {
      if ( ! parentFeature.attribute( *it ).isValid() )
        return false;
    }
    if ( ! expressionParentFormVariables( expression ).isEmpty() && parentFeature.geometry().isEmpty( ) )
      return false;
  }
  return true;
}

QgsVectorLayer *QgsValueRelationFieldFormatter::resolveLayer( const QVariantMap &config, const QgsProject *project )
{
  QgsVectorLayerRef ref { config.value( QStringLiteral( "Layer" ) ).toString(),
                          config.value( QStringLiteral( "LayerName" ) ).toString(),
                          config.value( QStringLiteral( "LayerSource" ) ).toString(),
                          config.value( QStringLiteral( "LayerProviderName" ) ).toString() };
  return ref.resolveByIdOrNameOnly( project );
}
