using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq.Expressions;
using System.Text;
using System.Reflection;
using System.Linq;
using System.Security.Permissions;
using System.Security;

namespace System.Data.Linq {
    using System.Data.Linq.Mapping;
    using System.Data.Linq.Provider;
    using System.Diagnostics.CodeAnalysis;

    /// <summary>
    /// Controls how inserts, updates and deletes are performed.
    /// </summary>
    internal abstract class ChangeDirector {
        internal abstract int Insert(TrackedObject item);
        internal abstract int DynamicInsert(TrackedObject item);
        internal abstract void AppendInsertText(TrackedObject item, StringBuilder appendTo);

        internal abstract int Update(TrackedObject item);
        internal abstract int DynamicUpdate(TrackedObject item);
        internal abstract void AppendUpdateText(TrackedObject item, StringBuilder appendTo);

        internal abstract int Delete(TrackedObject item);
        internal abstract int DynamicDelete(TrackedObject item);
        internal abstract void AppendDeleteText(TrackedObject item, StringBuilder appendTo);

        internal abstract void RollbackAutoSync();
        internal abstract void ClearAutoSyncRollback();

        internal static ChangeDirector CreateChangeDirector(DataContext context) {
            return new StandardChangeDirector(context);
        }

        /// <summary>
        /// Implementation of ChangeDirector which calls user code if possible 
        /// and othewise falls back to creating SQL for 'INSERT', 'UPDATE' and 'DELETE'.
        /// </summary>
        internal class StandardChangeDirector : ChangeDirector {
            private enum UpdateType { Insert, Update, Delete };
            private enum AutoSyncBehavior { ApplyNewAutoSync, RollbackSavedValues }            

            DataContext context;
            [SuppressMessage("Microsoft.MSInternal", "CA908:AvoidTypesThatRequireJitCompilationInPrecompiledAssemblies", Justification="[....]: FxCop bug Dev10:423110 -- List<KeyValuePair<object, object>> is not supposed to be flagged as a violation.")]
            List<KeyValuePair<TrackedObject, object[]>> syncRollbackItems;
            
            internal StandardChangeDirector(DataContext context) {
                this.context = context;
            }

            [SuppressMessage("Microsoft.MSInternal", "CA908:AvoidTypesThatRequireJitCompilationInPrecompiledAssemblies", Justification="[....]: FxCop bug Dev10:423110 -- List<KeyValuePair<object, object>> is not supposed to be flagged as a violation.")]
            private List<KeyValuePair<TrackedObject, object[]>> SyncRollbackItems {
                get {
                    if (syncRollbackItems == null) {
                        syncRollbackItems = new List<KeyValuePair<TrackedObject, object[]>>();
                    }
                    return syncRollbackItems;
                }
            }

            internal override int Insert(TrackedObject item) {
                if (item.Type.Table.InsertMethod != null) {
                    try {
                        item.Type.Table.InsertMethod.Invoke(this.context, new object[] { item.Current });
                    }
                    catch (TargetInvocationException tie) {
                        if (tie.InnerException != null) {
                            throw tie.InnerException;
                        }
                        throw;
                    }
                    return 1;
                }
                else {
                    return DynamicInsert(item);
                }
            }

            internal override int DynamicInsert(TrackedObject item) {
                Expression cmd = this.GetInsertCommand(item);
                if (cmd.Type == typeof(int)) {
                    return (int)this.context.Provider.Execute(cmd).ReturnValue;
                }
                else {
                    IEnumerable<object> facts = (IEnumerable<object>)this.context.Provider.Execute(cmd).ReturnValue;
                    object[] syncResults = (object[])facts.FirstOrDefault();
                    if (syncResults != null) {
                        // [....] any auto gen or computed members
                        AutoSyncMembers(syncResults, item, UpdateType.Insert, AutoSyncBehavior.ApplyNewAutoSync);
                        return 1;
                    }
                    else {
                        throw Error.InsertAutoSyncFailure();
                    }
                }
            }

            internal override void AppendInsertText(TrackedObject item, StringBuilder appendTo) {
                if (item.Type.Table.InsertMethod != null) {
                    appendTo.Append(Strings.InsertCallbackComment);
                }
                else {
                    Expression cmd = this.GetInsertCommand(item);
                    appendTo.Append(this.context.Provider.GetQueryText(cmd));
                    appendTo.AppendLine();
                }
            }

            /// <summary>
            /// Update the item, returning 0 if the update fails, 1 if it succeeds.
            /// </summary>        
            internal override int Update(TrackedObject item) {
                if (item.Type.Table.UpdateMethod != null) {
                    // create a copy - don't allow the override to modify our
                    // internal original values
                    try {
                        item.Type.Table.UpdateMethod.Invoke(this.context, new object[] { item.Current });
                    }
                    catch (TargetInvocationException tie) {
                        if (tie.InnerException != null) {
                            throw tie.InnerException;
                        }
                        throw;
                    }
                    return 1;
                }
                else {
                    return DynamicUpdate(item);
                }
            }

            internal override int DynamicUpdate(TrackedObject item) {
                Expression cmd = this.GetUpdateCommand(item);
                if (cmd.Type == typeof(int)) {
                    return (int)this.context.Provider.Execute(cmd).ReturnValue;
                }
                else {
                    IEnumerable<object> facts = (IEnumerable<object>)this.context.Provider.Execute(cmd).ReturnValue;
                    object[] syncResults = (object[])facts.FirstOrDefault();
                    if (syncResults != null) {
                        // [....] any auto gen or computed members
                        AutoSyncMembers(syncResults, item, UpdateType.Update, AutoSyncBehavior.ApplyNewAutoSync);
                        return 1;
                    }
                    else {
                        return 0;
                    }
                }
            }

            internal override void AppendUpdateText(TrackedObject item, StringBuilder appendTo) {
                if (item.Type.Table.UpdateMethod != null) {
                    appendTo.Append(Strings.UpdateCallbackComment);
                }
                else {
                    Expression cmd = this.GetUpdateCommand(item);
                    appendTo.Append(this.context.Provider.GetQueryText(cmd));
                    appendTo.AppendLine();
                }
            }

            internal override int Delete(TrackedObject item) {
                if (item.Type.Table.DeleteMethod != null) {
                    try {
                        item.Type.Table.DeleteMethod.Invoke(this.context, new object[] { item.Current });
                    }
                    catch (TargetInvocationException tie) {
                        if (tie.InnerException != null) {
                            throw tie.InnerException;
                        }
                        throw;
                    }
                    return 1;
                }
                else {
                    return DynamicDelete(item);
                }
            }

            internal override int DynamicDelete(TrackedObject item) {
                Expression cmd = this.GetDeleteCommand(item);
                int ret = (int)this.context.Provider.Execute(cmd).ReturnValue;
                if (ret == 0) {
                    // we don't yet know if the delete failed because the check constaint did not match
                    // or item was already deleted.  Verify the item exists
                    cmd = this.GetDeleteVerificationCommand(item);
                    ret = ((int?)this.context.Provider.Execute(cmd).ReturnValue) ?? -1;
                }
                return ret;
            }

            internal override void AppendDeleteText(TrackedObject item, StringBuilder appendTo) {
                if (item.Type.Table.DeleteMethod != null) {
                    appendTo.Append(Strings.DeleteCallbackComment);
                }
                else {
                    Expression cmd = this.GetDeleteCommand(item);
                    appendTo.Append(this.context.Provider.GetQueryText(cmd));
                    appendTo.AppendLine();
                }
            }

            [SuppressMessage("Microsoft.MSInternal", "CA908:AvoidTypesThatRequireJitCompilationInPrecompiledAssemblies", Justification="[....]: FxCop bug Dev10:423110 -- List<KeyValuePair<object, object>> is not supposed to be flagged as a violation.")]
            internal override void  RollbackAutoSync() {
                // Rolls back any AutoSync values that may have been set already
                // Those values are no longer valid since the transaction will be rolled back on the server
                if (this.syncRollbackItems != null) {
                    foreach (KeyValuePair<TrackedObject, object[]> rollbackItemPair in this.SyncRollbackItems) {
                        TrackedObject rollbackItem = rollbackItemPair.Key;
                        object[] rollbackValues = rollbackItemPair.Value;

                        AutoSyncMembers(
                            rollbackValues,
                            rollbackItem,
                            rollbackItem.IsNew ? UpdateType.Insert : UpdateType.Update,
                            AutoSyncBehavior.RollbackSavedValues);
                    }
                }
            }

            [SuppressMessage("Microsoft.MSInternal", "CA908:AvoidTypesThatRequireJitCompilationInPrecompiledAssemblies", Justification="[....]: FxCop bug Dev10:423110 -- List<KeyValuePair<object, object>> is not supposed to be flagged as a violation.")]
            internal override void  ClearAutoSyncRollback() {
                this.syncRollbackItems = null;
            }

            private Expression GetInsertCommand(TrackedObject item) {
                MetaType mt = item.Type;

                // bind to InsertFacts if there are any members to syncronize
                List<MetaDataMember> membersToSync = GetAutoSyncMembers(mt, UpdateType.Insert);
                ParameterExpression p = Expression.Parameter(item.Type.Table.RowType.Type, "p");
                if (membersToSync.Count > 0) {
                    Expression autoSync = this.CreateAutoSync(membersToSync, p);
                    LambdaExpression resultSelector = Expression.Lambda(autoSync, p);
                    return Expression.Call(typeof(DataManipulation), "Insert", new Type[] { item.Type.InheritanceRoot.Type, resultSelector.Body.Type }, Expression.Constant(item.Current), resultSelector);
                }
                else {
                    return Expression.Call(typeof(DataManipulation), "Insert", new Type[] { item.Type.InheritanceRoot.Type }, Expression.Constant(item.Current));
                }
            }

            /// <summary>
            /// For the meta members specified, create an array initializer for each and bind to
            /// an output array.
            /// </summary>
            private Expression CreateAutoSync(List<MetaDataMember> membersToSync, Expression source) {
                System.Diagnostics.Debug.Assert(membersToSync.Count > 0);
                int i = 0;
                Expression[] initializers = new Expression[membersToSync.Count];
                foreach (MetaDataMember mm in membersToSync) {
                    initializers[i++] = Expression.Convert(this.GetMemberExpression(source, mm.Member), typeof(object));
                }
                return Expression.NewArrayInit(typeof(object), initializers);
            }

            private static List<MetaDataMember> GetAutoSyncMembers(MetaType metaType, UpdateType updateType) {
                List<MetaDataMember> membersToSync = new List<MetaDataMember>();
                foreach (MetaDataMember metaMember in metaType.PersistentDataMembers.OrderBy(m => m.Ordinal)) {
                    // add all auto generated members for the specified update type to the auto-[....] list
                    if ((updateType == UpdateType.Insert && metaMember.AutoSync == AutoSync.OnInsert) ||
                        (updateType == UpdateType.Update && metaMember.AutoSync == AutoSync.OnUpdate) ||
                         metaMember.AutoSync == AutoSync.Always) {
                        membersToSync.Add(metaMember);
                    }
                }
                return membersToSync;
            }

            /// <summary>
            /// Synchronize the specified item by copying in data from the specified results.
            /// Used to [....] members after successful insert or update, but also used to rollback to previous values if a failure
            /// occurs on other entities in the same SubmitChanges batch.
            /// </summary>
            /// <param name="autoSyncBehavior">
            /// If AutoSyncBehavior.ApplyNewAutoSync, the current value of the property is saved before the [....] occurs. This is used for normal synchronization after a successful update/insert.
            /// Otherwise, the current value is not saved. This is used for rollback operations when something in the SubmitChanges batch failed, rendering the previously-[....]'d values invalid.
            /// </param>
            [SuppressMessage("Microsoft.MSInternal", "CA908:AvoidTypesThatRequireJitCompilationInPrecompiledAssemblies", Justification="[....]: FxCop bug Dev10:423110 -- List<KeyValuePair<object, object>> is not supposed to be flagged as a violation.")]
            private void AutoSyncMembers(object[] syncResults, TrackedObject item, UpdateType updateType, AutoSyncBehavior autoSyncBehavior) {
                System.Diagnostics.Debug.Assert(item != null);
                System.Diagnostics.Debug.Assert(item.IsNew || item.IsPossiblyModified, "AutoSyncMembers should only be called for new and modified objects.");
                object[] syncRollbackValues = null;
                if (syncResults != null) {
                    int idx = 0;
                    List<MetaDataMember> membersToSync = GetAutoSyncMembers(item.Type, updateType);
                    System.Diagnostics.Debug.Assert(syncResults.Length == membersToSync.Count);                    
                    if (autoSyncBehavior == AutoSyncBehavior.ApplyNewAutoSync) {
                        syncRollbackValues = new object[syncResults.Length];
                    }
                    foreach (MetaDataMember mm in membersToSync) {
                        object value = syncResults[idx];
                        object current = item.Current;
                        MetaAccessor accessor =
                            (mm.Member is PropertyInfo && ((PropertyInfo)mm.Member).CanWrite)
                                ? mm.MemberAccessor
                                : mm.StorageAccessor;

                        if (syncRollbackValues != null) {
                            syncRollbackValues[idx] = accessor.GetBoxedValue(current);
                        }
                        accessor.SetBoxedValue(ref current, DBConvert.ChangeType(value, mm.Type));
                        idx++;
                    }                    
                }
                if (syncRollbackValues != null) {
                    this.SyncRollbackItems.Add(new KeyValuePair<TrackedObject, object[]>(item, syncRollbackValues));
                }
            }

            private Expression GetUpdateCommand(TrackedObject tracked) {
                object database = tracked.Original;
                MetaType rowType = tracked.Type.GetInheritanceType(database.GetType());
                MetaType rowTypeRoot = rowType.InheritanceRoot;

                ParameterExpression p = Expression.Parameter(rowTypeRoot.Type, "p");
                Expression pv = p;
                if (rowType != rowTypeRoot) {
                    pv = Expression.Convert(p, rowType.Type);
                }

                Expression check = this.GetUpdateCheck(pv, tracked);
                if (check != null) {
                    check = Expression.Lambda(check, p);
                }

                // bind to out array if there are any members to synchronize
                List<MetaDataMember> membersToSync = GetAutoSyncMembers(rowType, UpdateType.Update);
                if (membersToSync.Count > 0) {
                    Expression autoSync = this.CreateAutoSync(membersToSync, pv);
                    LambdaExpression resultSelector = Expression.Lambda(autoSync, p);
                    if (check != null) {
                        return Expression.Call(typeof(DataManipulation), "Update", new Type[] { rowTypeRoot.Type, resultSelector.Body.Type }, Expression.Constant(tracked.Current), check, resultSelector);
                    }
                    else {
                        return Expression.Call(typeof(DataManipulation), "Update", new Type[] { rowTypeRoot.Type, resultSelector.Body.Type }, Expression.Constant(tracked.Current), resultSelector);
                    }
                }
                else if (check != null) {
                    return Expression.Call(typeof(DataManipulation), "Update", new Type[] { rowTypeRoot.Type }, Expression.Constant(tracked.Current), check);
                }
                else {
                    return Expression.Call(typeof(DataManipulation), "Update", new Type[] { rowTypeRoot.Type }, Expression.Constant(tracked.Current));
                }
            }

            private Expression GetUpdateCheck(Expression serverItem, TrackedObject tracked) {
                MetaType mt = tracked.Type;
                if (mt.VersionMember != null) {
                    return Expression.Equal(
                        this.GetMemberExpression(serverItem, mt.VersionMember.Member),
                        this.GetMemberExpression(Expression.Constant(tracked.Current), mt.VersionMember.Member)
                        );
                }
                else {
                    Expression expr = null;
                    foreach (MetaDataMember mm in mt.PersistentDataMembers) {
                        if (!mm.IsPrimaryKey) {
                            UpdateCheck check = mm.UpdateCheck;
                            if (check == UpdateCheck.Always ||
                                (check == UpdateCheck.WhenChanged && tracked.HasChangedValue(mm))) {
                                object memberValue = mm.MemberAccessor.GetBoxedValue(tracked.Original);
                                Expression eq =
                                    Expression.Equal(
                                        this.GetMemberExpression(serverItem, mm.Member),
                                        Expression.Constant(memberValue, mm.Type)
                                        );
                                expr = (expr != null) ? Expression.And(expr, eq) : eq;
                            }
                        }
                    }
                    return expr;
                }
            }

            private Expression GetDeleteCommand(TrackedObject tracked) {
                MetaType rowType = tracked.Type;
                MetaType rowTypeRoot = rowType.InheritanceRoot;
                ParameterExpression p = Expression.Parameter(rowTypeRoot.Type, "p");
                Expression pv = p;
                if (rowType != rowTypeRoot) {
                    pv = Expression.Convert(p, rowType.Type);
                }
                object original = tracked.CreateDataCopy(tracked.Original);
                Expression check = this.GetUpdateCheck(pv, tracked);
                if (check != null) {
                    check = Expression.Lambda(check, p);
                    return Expression.Call(typeof(DataManipulation), "Delete", new Type[] { rowTypeRoot.Type }, Expression.Constant(original), check);
                }
                else {
                    return Expression.Call(typeof(DataManipulation), "Delete", new Type[] { rowTypeRoot.Type }, Expression.Constant(original));
                }
            }

            private Expression GetDeleteVerificationCommand(TrackedObject tracked) {
                ITable table = this.context.GetTable(tracked.Type.InheritanceRoot.Type);
                System.Diagnostics.Debug.Assert(table != null);
                ParameterExpression p = Expression.Parameter(table.ElementType, "p");
                Expression pred = Expression.Lambda(Expression.Equal(p, Expression.Constant(tracked.Current)), p);
                Expression where = Expression.Call(typeof(Queryable), "Where", new Type[] { table.ElementType }, table.Expression, pred);
                Expression selector = Expression.Lambda(Expression.Constant(0, typeof(int?)), p);
                Expression select = Expression.Call(typeof(Queryable), "Select", new Type[] { table.ElementType, typeof(int?) }, where, selector);
                Expression singleOrDefault = Expression.Call(typeof(Queryable), "SingleOrDefault", new Type[] { typeof(int?) }, select);
                return singleOrDefault;
            }

            [SuppressMessage("Microsoft.Performance", "CA1822:MarkMembersAsStatic", Justification="Unknown reason.")]
            private Expression GetMemberExpression(Expression exp, MemberInfo mi) {
                FieldInfo fi = mi as FieldInfo;
                if (fi != null)
                    return Expression.Field(exp, fi);
                PropertyInfo pi = (PropertyInfo)mi;
                return Expression.Property(exp, pi);
            }
        }
    }
}