{
* This Source Code Form is subject to the terms of the Mozilla Public License,
* v. 2.0. If a copy of the MPL was not distributed with this file, You can
* obtain one at http://mozilla.org/MPL/2.0/
*
* Copyright (C) 2005-2013, Peter Johnson (www.delphidabbler.com).
*
* $Rev$
* $Date$
*
* Defines a singleton object and subsidiary classes that encapsulate the
* snippets and tags in the snippets database.
}
unit DB.UMain;
interface
uses
// Project
CS.Database.SnippetsTable,
CS.Database.Types,
CS.Utils.Dates,
UMultiCastEvents,
USingleton;
type
{
TDatabaseChangeEventKind:
Enumeration that specifies the different kind of change events triggered by
the database.
}
TDatabaseChangeEventKind = (
evChangeBegin, // a change to the database is about to take place
evChangeEnd, // a change to the database has completed
evSnippetAdded, // a snippet has been added
evBeforeSnippetDelete, // a snippet is about to be deleted
evSnippetDeleted, // a snippet has been deleted
evBeforeSnippetChange, // a snippet is about to be changed
evSnippetChanged // a snippet's properties / references have changed
// TODO: add suitable event kinds for changes to tags as required
);
{
IDatabaseChangeEventInfo:
Interface supported by objects passed to Database object's change event
handler that provides information about a change event. Some properites
are not defined for certain event types. Kind property always defined.
}
IDatabaseChangeEventInfo = interface(IInterface)
['{80DEE62F-DC23-4EE7-A0B1-5DE46F483CE1}']
function GetKind: TDatabaseChangeEventKind;
{Gets kind (type) of event.
@return Event kind.
}
function GetInfo: TObject;
{Gets additional information about event.
@return Object that provides required information.
}
property Kind: TDatabaseChangeEventKind read GetKind;
{Identifies kind (type) of an event. Always defined}
property Info: TObject read GetInfo;
{Provides additional information about the event. Actual type of object
depends on Kind. May be nil}
end;
TDBFilterFn = reference to function (ASnippet: ISnippet): Boolean;
TDatabase = class(TSingleton)
strict private
type
{
TEventInfo:
Class that provides information about a change event.
}
TEventInfo = class(TInterfacedObject, IDatabaseChangeEventInfo)
strict private
fKind: TDatabaseChangeEventKind; // Kind of event
fInfo: TObject; // Extra info about event
public
constructor Create(const Kind: TDatabaseChangeEventKind;
const Info: TObject = nil);
{Constructor. Creates an event information object.
@param Kind [in] Kind of event.
@param Info [in] Reference to further information about the event.
May be nil if event doesn't have additional information.
}
{ IDatabaseChangeEventInfo methods }
function GetKind: TDatabaseChangeEventKind;
{Gets kind (type) of event.
@return Event kind.
}
function GetInfo: TObject;
{Gets additional information about event.
@return Object that provides required information.
}
end;
strict private
class var
fInstance: TDatabase;
class function GetInstance: TDatabase; static;
strict private
var
fSnippetsTable: TDBSnippetsTable;
fAllTags: ITagSet;
fAllSnippetKinds: ISnippetKindList;
fLastModified: TUTCDateTime;
fDirty: Boolean;
fChangeEvents: TMulticastEvents; // List of change event handlers
procedure FlagUpdate;
procedure TriggerSnippetChangeEvent(const Kind: TDatabaseChangeEventKind;
const SnippetID: TSnippetID);
procedure TriggerNullDataEvent(const Kind: TDatabaseChangeEventKind);
procedure TriggerChangeEvent(const Kind: TDatabaseChangeEventKind;
const Info: TObject = nil);
{Triggers a change event. Notifies all registered listeners.
@param Kind [in] Kind of event.
@param Info [in] Reference to any further information for event. May be
nil.
}
strict protected
procedure Initialize; override;
procedure Finalize; override;
public
class property Instance: TDatabase read GetInstance;
public
procedure Load;
procedure Save;
function IsDirty: Boolean;
function LookupEditableSnippet(const ASnippetID: TSnippetID):
IEditableSnippet;
function TryLookupEditableSnippet(const ASnippetID: TSnippetID;
out ASnippet: IEditableSnippet): Boolean;
function LookupSnippet(const ASnippetID: TSnippetID): ISnippet;
function TryLookupSnippet(const ASnippetID: TSnippetID;
out ASnippet: ISnippet): Boolean;
function SelectSnippets(FilterFn: TDBFilterFn): ISnippetIDList;
function GetAllSnippets: ISnippetIDList;
function GetAllTags: ITagSet;
function GetAllSnippetKinds: ISnippetKindList;
function SnippetExists(const ASnippetID: TSnippetID): Boolean;
function SnippetCount: Integer;
function IsEmpty: Boolean;
// Returns a list of IDs of all snippets that depend on the snippet with
// the given ID.
function GetDependentsOf(const ASnippetID: TSnippetID): ISnippetIDList;
// Returns a list of IDs of all snippet that refer to (i.e. cross-reference)
// the snippet with the given ID.
function GetReferrersTo(const ASnippetID: TSnippetID): ISnippetIDList;
function NewSnippet: IEditableSnippet;
procedure AddSnippet(ASnippet: IEditableSnippet);
procedure UpdateSnippet(ASnippet: IEditableSnippet);
procedure DeleteSnippet(ASnippetID: TSnippetID);
procedure AddChangeEventHandler(const Handler: TNotifyEventInfo);
{Adds a change event handler to list of listeners.
@param Handler [in] Event handler to be added.
}
procedure RemoveChangeEventHandler(const Handler: TNotifyEventInfo);
{Removes a change event handler from list of listeners.
@param Handler [in] Handler to remove from list.
}
end;
function Database: TDatabase;
implementation
uses
// Project
CS.Database.IO.Factory,
CS.Database.IO.Types,
CS.Database.SnippetKinds,
CS.Database.Snippets,
CS.Database.Tags,
UBox,
UExceptions,
UQuery,
UStrUtils,
UUniqueID;
function Database: TDatabase;
begin
Result := TDatabase.Instance;
end;
{ TDatabase }
procedure TDatabase.AddChangeEventHandler(const Handler: TNotifyEventInfo);
begin
fChangeEvents.AddHandler(Handler);
end;
procedure TDatabase.AddSnippet(ASnippet: IEditableSnippet);
var
DBSnippet: TDBSnippet;
resourcestring
// Error message
sNameExists = 'Snippet "%s" already exists in database';
begin
if fSnippetsTable.Contains(ASnippet.ID) then
raise ECodeSnip.CreateFmt(sNameExists, [ASnippet.ID.ToString]);
if not fAllTags.ContainsSubSet(ASnippet.Tags) then
begin
{ TODO: Add TriggerNullDataEvent(evChangeBegin); }
fAllTags.Include(ASnippet.Tags);
{ TODO: Add change event for all tags added. Something like:
for Tag in ASnippet.Tags do
TriggerTagChangeEvent(evTagAdded, Tag); }
{ TODO: Add TriggerNullDataEvent(evChangeEnd); }
end;
TriggerNullDataEvent(evChangeBegin);
try
// TODO: Do we need to check snippet references and xrefs here?
DBSnippet := TDBSnippet.CreateFrom(ASnippet);
FlagUpdate; // sets fLastModifed
DBSnippet.SetCreated(fLastModified);
DBSnippet.SetModified(fLastModified);
fSnippetsTable.Add(DBSnippet);
Query.Update;
TriggerSnippetChangeEvent(evSnippetAdded, ASnippet.ID);
finally
TriggerNullDataEvent(evChangeEnd);
end;
end;
procedure TDatabase.DeleteSnippet(ASnippetID: TSnippetID);
var
Dependent: TSnippetID; // each snippet that depends on Snippet
Dependents: ISnippetIDList; // list of dependent snippets
Referrer: TSnippetID; // each snippet that cross references Snippet
Referrers: ISnippetIDList; // list of referencing snippets
begin
Assert(Database.SnippetExists(ASnippetID),
ClassName + '.DeleteSnippet: Snippet is not in the database');
TriggerNullDataEvent(evChangeBegin);
TriggerSnippetChangeEvent(evBeforeSnippetDelete, ASnippetID);
// Get list of referencing and dependent snippets
Dependents := nil;
Referrers := nil;
try
Dependents := Database.GetDependentsOf(ASnippetID);
Referrers := Database.GetReferrersTo(ASnippetID);
// TODO: scan all snippets and remove references that match snippet ID
// Delete snippet for XRef or Depends list of referencing snippets
for Referrer in Referrers do
fSnippetsTable.Get(Referrer).GetXRefs.Remove(ASnippetID);
for Dependent in Dependents do
fSnippetsTable.Get(Dependent).GetRequiredSnippets.Remove(
ASnippetID
);
// Delete snippet itself
fSnippetsTable.Delete(ASnippetID);
Query.Update;
finally
FlagUpdate;
TriggerSnippetChangeEvent(evSnippetDeleted, ASnippetID);
TriggerNullDataEvent(evChangeEnd);
end;
end;
procedure TDatabase.Finalize;
begin
fChangeEvents.Free;
fSnippetsTable.Free;
inherited;
end;
procedure TDatabase.FlagUpdate;
begin
fDirty := True;
fLastModified := TUTCDateTime.Now;
end;
function TDatabase.GetAllSnippetKinds: ISnippetKindList;
begin
Result := fAllSnippetKinds;
end;
function TDatabase.GetAllSnippets: ISnippetIDList;
var
Snippet: TDBSnippet;
begin
Result := TSnippetIDList.Create(fSnippetsTable.Size);
for Snippet in fSnippetsTable do
Result.Add(Snippet.GetID);
end;
function TDatabase.GetAllTags: ITagSet;
begin
Result := TTagSet.Create(fAllTags);
end;
function TDatabase.GetDependentsOf(const ASnippetID: TSnippetID):
ISnippetIDList;
var
Snippet: TDBSnippet;
begin
Result := TSnippetIDList.Create;
for Snippet in fSnippetsTable do
if (Snippet.GetID <> ASnippetID)
and Snippet.GetRequiredSnippets.Contains(ASnippetID) then
Result.Add(Snippet.GetID);
end;
class function TDatabase.GetInstance: TDatabase;
begin
if not Assigned(fInstance) then
fInstance := TDatabase.Create;
Result := fInstance;
end;
function TDatabase.GetReferrersTo(const ASnippetID: TSnippetID): ISnippetIDList;
var
Snippet: TDBSnippet; // references each snippet in database
begin
Result := TSnippetIDList.Create;
for Snippet in fSnippetsTable do
if (Snippet.GetID <> ASnippetID)
and Snippet.GetXRefs.Contains(ASnippetID) then
Result.Add(Snippet.GetID);
end;
procedure TDatabase.Initialize;
begin
inherited;
fSnippetsTable := TDBSnippetsTable.Create;
fAllTags := TTagSet.Create;
fAllSnippetKinds := TSnippetKindList.Create;
fChangeEvents := TMultiCastEvents.Create(Self);
end;
function TDatabase.IsDirty: Boolean;
begin
Result := fDirty;
end;
function TDatabase.IsEmpty: Boolean;
begin
Result := fSnippetsTable.Size = 0;
end;
procedure TDatabase.Load;
var
Loader: IDatabaseLoader;
begin
fSnippetsTable.Clear; // TODO: decide if loaders should clear this table
Loader := TDatabaseIOFactory.CreateLoader;
Loader.Load(fSnippetsTable, fAllTags, fLastModified);
fDirty := False;
end;
function TDatabase.LookupEditableSnippet(const ASnippetID: TSnippetID):
IEditableSnippet;
var
Row: TDBSnippet;
begin
Row := fSnippetsTable.Get(ASnippetID);
Result := Row.CloneAsEditable;
end;
function TDatabase.LookupSnippet(const ASnippetID: TSnippetID): ISnippet;
var
Row: TDBSnippet;
begin
Row := fSnippetsTable.Get(ASnippetID);
Result := Row.CloneAsReadOnly;
end;
function TDatabase.NewSnippet: IEditableSnippet;
begin
// Snippet IDs created in TEditableSnippet.CreateNew *should* be unique, but
// we make sure the ID is unique, just in case!
repeat
Result := TEditableSnippet.CreateNew;
until not fSnippetsTable.Contains(Result.ID);
end;
procedure TDatabase.RemoveChangeEventHandler(const Handler: TNotifyEventInfo);
begin
fChangeEvents.RemoveHandler(Handler);
end;
procedure TDatabase.Save;
var
Writer: IDatabaseWriter;
begin
Writer := TDatabaseIOFactory.CreateWriter;
Writer.Save(fSnippetsTable, fAllTags, fLastModified);
fDirty := False;
end;
function TDatabase.SelectSnippets(FilterFn: TDBFilterFn): ISnippetIDList;
var
Snippet: TDBSnippet;
begin
Result := TSnippetIDList.Create;
for Snippet in fSnippetsTable do
if FilterFn(Snippet.CloneAsReadOnly) then
Result.Add(Snippet.GetID)
end;
function TDatabase.SnippetCount: Integer;
begin
Result := fSnippetsTable.Size;
end;
function TDatabase.SnippetExists(const ASnippetID: TSnippetID): Boolean;
begin
Result := fSnippetsTable.Contains(ASnippetID);
end;
procedure TDatabase.TriggerChangeEvent(const Kind: TDatabaseChangeEventKind;
const Info: TObject);
var
EvtInfo: IDatabaseChangeEventInfo; // event information object
begin
EvtInfo := TEventInfo.Create(Kind, Info);
fChangeEvents.TriggerEvents(EvtInfo);
end;
procedure TDatabase.TriggerNullDataEvent(const Kind: TDatabaseChangeEventKind);
begin
TriggerChangeEvent(Kind, nil);
end;
procedure TDatabase.TriggerSnippetChangeEvent(
const Kind: TDatabaseChangeEventKind; const SnippetID: TSnippetID);
var
Obj: TBox<TSnippetID>;
begin
Obj := TBox<TSnippetID>.Create(SnippetID);
try
TriggerChangeEvent(Kind, Obj);
finally
Obj.Free;
end;
end;
function TDatabase.TryLookupEditableSnippet(const ASnippetID: TSnippetID;
out ASnippet: IEditableSnippet): Boolean;
begin
Result := fSnippetsTable.Contains(ASnippetID);
if Result then
ASnippet := fSnippetsTable.Get(ASnippetID).CloneAsEditable
else
ASnippet := nil;
end;
function TDatabase.TryLookupSnippet(const ASnippetID: TSnippetID;
out ASnippet: ISnippet): Boolean;
begin
Result := fSnippetsTable.Contains(ASnippetID);
if Result then
ASnippet := fSnippetsTable.Get(ASnippetID).CloneAsReadOnly
else
ASnippet := nil;
end;
procedure TDatabase.UpdateSnippet(ASnippet: IEditableSnippet);
var
DBSnippet: TDBSnippet;
begin
// TODO: refactor out this common in common with AddSnippet
if not fAllTags.ContainsSubSet(ASnippet.Tags) then
begin
{ TODO: Add TriggerNullDataEvent(evChangeBegin); }
fAllTags.Include(ASnippet.Tags);
{ TODO: Add change event for all tags added. Something like:
for Tag in ASnippet.Tags do
TriggerTagChangeEvent(evTagAdded, Tag); }
{ TODO: Add TriggerNullDataEvent(evChangeEnd); }
end;
TriggerNullDataEvent(evChangeBegin);
TriggerSnippetChangeEvent(evBeforeSnippetChange, ASnippet.ID);
DBSnippet := TDBSnippet.CreateFrom(ASnippet);
try
// TODO: Do we need to check snippet references and xrefs here?
FlagUpdate;
DBSnippet.SetModified(fLastModified);
fSnippetsTable.Update(DBSnippet);
Query.Update;
finally
TriggerSnippetChangeEvent(evSnippetChanged, ASnippet.ID);
TriggerNullDataEvent(evChangeEnd);
DBSnippet.Free;
end;
end;
{ TDatabase.TEventInfo }
constructor TDatabase.TEventInfo.Create(const Kind: TDatabaseChangeEventKind;
const Info: TObject);
begin
inherited Create;
fKind := Kind;
fInfo := Info;
end;
function TDatabase.TEventInfo.GetInfo: TObject;
begin
Result := fInfo;
end;
function TDatabase.TEventInfo.GetKind: TDatabaseChangeEventKind;
begin
Result := fKind;
end;
end.
