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// Copyright 2009-2022 Josh Close
// This file is a part of CsvHelper and is dual licensed under MS-PL and Apache 2.0.
// See LICENSE.txt for details or visit http://www.opensource.org/licenses/ms-pl.html for MS-PL and http://opensource.org/licenses/Apache-2.0 for Apache 2.0.
// https://github.com/JoshClose/CsvHelper
using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
namespace CsvHelper.Expressions
{
/// <summary>
/// Hydrates members of an existing record.
/// </summary>
public class RecordHydrator
{
private readonly CsvReader reader;
private readonly ExpressionManager expressionManager;
private readonly Dictionary<Type, Delegate> hydrateRecordActions = new Dictionary<Type, Delegate>();
/// <summary>
/// Creates a new instance using the given reader.
/// </summary>
/// <param name="reader">The reader.</param>
public RecordHydrator(CsvReader reader)
{
this.reader = reader;
expressionManager = ObjectResolver.Current.Resolve<ExpressionManager>(reader);
}
/// <summary>
/// Hydrates members of the given record using the current reader row.
/// </summary>
/// <typeparam name="T">The record type.</typeparam>
/// <param name="record">The record.</param>
public void Hydrate<T>(T record)
{
try
{
GetHydrateRecordAction<T>()(record);
}
catch (TargetInvocationException ex)
{
if (ex.InnerException != null)
{
throw ex.InnerException;
}
else
{
throw;
}
}
}
/// <summary>
/// Gets the action delegate used to hydrate a custom class object's members with data from the reader.
/// </summary>
/// <typeparam name="T">The record type.</typeparam>
protected virtual Action<T> GetHydrateRecordAction<T>()
{
var recordType = typeof(T);
if (!hydrateRecordActions.TryGetValue(recordType, out Delegate action))
{
hydrateRecordActions[recordType] = action = CreateHydrateRecordAction<T>();
}
return (Action<T>)action;
}
/// <summary>
/// Creates the action delegate used to hydrate a record's members with data from the reader.
/// </summary>
/// <typeparam name="T">The record type.</typeparam>
protected virtual Action<T> CreateHydrateRecordAction<T>()
{
var recordType = typeof(T);
if (reader.Context.Maps[recordType] == null)
{
reader.Context.Maps.Add(reader.Context.AutoMap(recordType));
}
var mapping = reader.Context.Maps[recordType];
var recordTypeParameter = Expression.Parameter(recordType, "record");
var memberAssignments = new List<Expression>();
foreach (var memberMap in mapping.MemberMaps)
{
var fieldExpression = expressionManager.CreateGetFieldExpression(memberMap);
if (fieldExpression == null)
{
continue;
}
var memberTypeParameter = Expression.Parameter(memberMap.Data.Member.MemberType(), "member");
var memberAccess = Expression.MakeMemberAccess(recordTypeParameter, memberMap.Data.Member);
var memberAssignment = Expression.Assign(memberAccess, fieldExpression);
memberAssignments.Add(memberAssignment);
}
foreach (var referenceMap in mapping.ReferenceMaps)
{
if (!reader.CanRead(referenceMap))
{
continue;
}
var referenceAssignments = new List<MemberAssignment>();
expressionManager.CreateMemberAssignmentsForMapping(referenceMap.Data.Mapping, referenceAssignments);
var referenceBody = expressionManager.CreateInstanceAndAssignMembers(referenceMap.Data.Member.MemberType(), referenceAssignments);
var memberTypeParameter = Expression.Parameter(referenceMap.Data.Member.MemberType(), "referenceMember");
var memberAccess = Expression.MakeMemberAccess(recordTypeParameter, referenceMap.Data.Member);
var memberAssignment = Expression.Assign(memberAccess, referenceBody);
memberAssignments.Add(memberAssignment);
}
var body = Expression.Block(memberAssignments);
return Expression.Lambda<Action<T>>(body, recordTypeParameter).Compile();
}
}
}
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