{
    通常将TTracer的实例存放于application级的Session中,在使用时,
    创建一个ITraceInfo,调用TTracer.Write(ITraceInfo)即可,
}

unit com.sunset.app.tracer;

interface

uses StrUtils,classes,SysUtils;

type

//==========================
// 接口声明
//==========================

    //跟踪信息的接口
    ITraceInfo = interface
        function ToString: string;
    end;
    //输出目标的接口
    IOutput = interface
        procedure Write(const aInfo: ITraceInfo); //写入跟踪信息
    end;

//==========================
// 跟踪信息类 ,实现 ITraceInfo
//==========================

    //string形式的跟踪记录
    TStringTI = class(TInterfacedObject, ITraceInfo)
    private
        FData: string;
    public
        constructor Create(data: string);
        function ToString: string;
    end;

//==========================
// 跟踪信息输出类,实现 IOutput
//==========================

    TFileLog = class(TInterfacedObject, IOutput)
    private
        FLogFile: string;
    public
        constructor Create(const FileName: string);
        procedure Write(const aInfo: ITraceInfo); //写入跟踪信息
    end;

    TProcStr = procedure(const value:string) of Object;
    TDatabaseLog = class(TInterfacedObject, IOutput)
    private
        FWriteProc :TProcStr;
    public
        constructor Create(WriteProc: TProcStr);
        procedure Write(const aInfo: ITraceInfo); //写入跟踪信息
    end;

//==========================
// 跟踪工具
//==========================

{ TTracer }
    //用来进行记录跟踪日志的类
    TTracer = class(TObject)
    private
        FOutput: IOutput; //输出目标
        procedure SetOutput(const Value: IOutput);
    public
        constructor Create; overload;
        constructor Create(aOutput: IOutput); overload;
        destructor Destroy; override;
        property Output: IOutput read FOutput write SetOutput;
        procedure Write(const aInfo: ITraceInfo); //写入跟踪信息
    end;

implementation

{ TTracer }

constructor TTracer.Create;
begin

end;

constructor TTracer.Create(aOutput: IOutput);
begin
    FOutput := aOutput;
end;

destructor TTracer.Destroy;
begin
    if FOutput <> nil then FOutput := nil;
    inherited;
end;

procedure TTracer.SetOutput(const Value: IOutput);
begin
    FOutput := Value;
end;

procedure TTracer.Write(const aInfo: ITraceInfo);
begin
    if FOutput = nil then raise Exception.CreateFmt('没有创建输出目标%s!!!', []);
    FOutput.Write(aInfo);
end;

{ TStringTI }

constructor TStringTI.Create(data: string);
begin
    FData := Data;
end;

function TStringTI.ToString: string;
begin
    Result := FData;
end;

{ TStringLog }

constructor TFileLog.Create(const FileName: string);
begin
    FLogFile := FileName;
end;

procedure TFileLog.Write(const aInfo: ITraceInfo);
begin
    if not FileExists(FLogFile) then FileClose(FileCreate(FLogFile));
    with TStringList.Create do
    begin
        try
            LoadFromFile(FLogFile);
            Add(aInfo.ToString);
            SaveToFile(FLogFile);
        finally
            Free;
        end;
    end;
end;

{ TDatabaseLog }

constructor TDatabaseLog.Create(WriteProc: TProcStr);
begin
    FWriteProc := WriteProc;
    if not Assigned(FWriteProc) then raise Exception.CreateFmt('没有传入正确的写入跟踪方法%s!!!', []);
end;

procedure TDatabaseLog.Write(const aInfo: ITraceInfo);
begin
    FWriteProc(aInfo.ToString);
end;

end.

===========测试代码===========
{************************}
{                                                }
{          测试名称：                  }
{          作    者：                      }
{          版    本：                     }
{          说    明：                     }
{          备    注：                    }
{                                              }
{***********************}

unit test.com.sunset.app.tracer;

interface

uses
  Windows, SysUtils, Classes, TestFramework, TestExtensions,
  com.sunset.app.tracer;

type
  TTest = class(TTestCase)
  protected
    procedure SetUp; override;
    procedure TearDown; override;

  published
    procedure TestTracer;
  end;

implementation

procedure TTest.Setup;
begin

end;

procedure TTest.TearDown;
begin

end;

procedure TTest.TestTracer;
var
    tracer:TTracer;
    aInfo:ITraceInfo;
const
    testData ='adfadfdasf';
    testFile ='d:\2.txt';
begin
    aInfo := TStringTI.Create(testData);
    Tracer := TTracer.Create(TFileLog.Create(testfile));
    Tracer.Write(aInfo);
    Tracer.Free;
    aInfo := nil;
    with TStringList.Create do
    begin
        LoadFromFile(testfile);
        Check(Strings[Count -1] = testData);
        Free;
    end;
end;

initialization
  TestFramework.RegisterTest(TTest.Suite);

end.