{

  Abstract:
    Methods and classes for loading translations/localizations from po files.

  Example 1: Load a specific .po file:

    procedure TForm1.FormCreate(Sender: TObject);
    var
      PODirectory: String;
    begin
      PODirectory:='/path/to/languages/';
      TranslateUnitResourceStrings('StrConsts',PODirectory+'gui.%s.po',
                                   'nl','');
      MessageDlg('Title','Text',mtInformation,[mbOk,mbCancel,mbYes],0);
    end;


  Example 2: Load the current language file using the GetLanguageIDs function
    of the gettext unit:

    procedure TForm1.FormCreate(Sender: TObject);
    var
      PODirectory, Lang, FallbackLang: String;
    begin
      PODirectory:='/path/to/languages/';
      GetLanguageIDs(Lang,FallbackLang); // in unit gettext
      TranslateUnitResourceStrings('StrConsts',PODirectory+'gui.%s.po',
                                   Lang,FallbackLang);
      MessageDlg('Title','Text',mtInformation,[mbOk,mbCancel,mbYes],0);
    end;
}
unit gfx_pofiles;

{$mode objfpc}{$H+}{$INLINE ON}

{.$Define DEBUG}

interface

uses
  Classes,
  SysUtils,
  Contnrs,
  gfx_stringhashlist;

type
  TPOFileItem = class(TObject)
  public
    Identifier: string;
    Original: string;
    Translation: string;
    constructor Create(const TheIdentifier, TheOriginal, TheTranslated: string);
  end;


  TPOFile = class(TObject)
  protected
    FItems: TFPList;  // list of TPOFileItem
    FIdentifierToItem: TStringHashList;
    FOriginalToItem: TStringHashList;
  public
    constructor Create(const AFilename: string);
    constructor Create(AStream: TStream);
    destructor  Destroy; override;
    procedure   ReadPOText(const s: string);
    procedure   Add(const Identifier, OriginalValue, TranslatedValue: string);
    function    Translate(const Identifier, OriginalValue: string): string;
    procedure   AppendFile(const AFilename: string);
  end;


  EPOFileError = class(Exception);


var
  SystemCharSetIsUTF8: Boolean = True;// the fpGUI interfaces expect UTF-8 as default
 // if you don't use UTF-8, install a proper widestring manager and set this
 // to false. You're on your own then!


// translate resource strings for one unit
procedure TranslateUnitResourceStrings(const ResUnitName, BaseFilename, Lang, FallbackLang: string);
function  TranslateUnitResourceStrings(const ResUnitName, AFilename: string): boolean;
function  UTF8ToSystemCharSet(const s: string): string; {$ifndef MultiLocale} inline;{$endif}


procedure DebugLn(const s1: string);
procedure DebugLn(const s1, s2: string);
procedure DebugLn(const s1, s2, s3: string);
procedure DebugLn(const s1, s2, s3, s4: string);

implementation

uses
  gfx_UTF8utils;

procedure DebugLn(const s1: string);
begin
  { TODO : Improve this to work under Windows GUI apps as well.}
  writeln(s1);
end;

procedure DebugLn(const s1, s2: string);
begin
  writeln(s1 + s2);
end;

procedure DebugLn(const s1, s2, s3: string);
begin
  writeln(s1 + s2 + s3);
end;

procedure DebugLn(const s1, s2, s3, s4: string);
begin
  writeln(s1 + s2 + s3 + s4);
end;


procedure DumpExceptionBackTrace;
var
  FrameCount: integer;
  Frames: PPointer;
  FrameNumber: integer;
begin
  DebugLn('  Stack trace:');
  DebugLn(BackTraceStrFunc(ExceptAddr));
  FrameCount := ExceptFrameCount;
  Frames     := ExceptFrames;
  for FrameNumber := 0 to FrameCount - 1 do
    DebugLn(BackTraceStrFunc(Frames[FrameNumber]));
end;


function UTF8ToSystemCharSet(const s: string): string; {$ifndef MultiLocale} inline;
{$endif}
begin
  if SystemCharSetIsUTF8 then
    Exit(s);
  {$IFDEF NoUTF8Translations}
  Result := s;
  {$ELSE}
    {$IFNDEF MultiLocale}
  Result := Utf8ToAnsi(s);
    {$ELSE}
  try
    if (LowerCase(GetDefaultCodepage) <> 'utf8') and (LowerCase(GetDefaultCodepage) <> 'utf-8') then
      Result := CPConvert(s, 'utf8', LowerCase(GetDefaultCodepage))
    else
      Result := s;
  except
    Result := s;
  end;
    {$ENDIF}
  {$ENDIF}
end;

{$ifndef ver2_0}
function Translate(Name, Value: ansistring; Hash: longint; arg: Pointer): ansistring;
var
  po: TPOFile;
begin
  po     := TPOFile(arg);
  // get UTF8 string
  Result := po.Translate(Name, Value);
  // convert UTF8 to current local
  if Result <> '' then
    Result := UTF8ToSystemCharSet(Result);
end;

{$endif ver2_0}

function TranslateUnitResourceStrings(const ResUnitName, AFilename: string): boolean;
var
{$ifdef ver2_0}
  TableID, StringID, TableCount: integer;
  s: string;
  DefValue: string;
{$endif ver2_0}
  po: TPOFile;
  lPath, lFile: string;
  lPos: integer;
  ToolkitOnly: Boolean;
begin
  {$IFDEF DEBUG}
  writeln('TranslateUnitResourceStrings:');
  {$ENDIF}
  Result := False;
  ToolkitOnly := False;

  // build correct filename for fpGUI Toolkit translations.
  lPath := ExtractFilePath(AFilename);
  lFile := ExtractFileName(AFilename);
  lPos := Pos('.', lFile);
  lFile := lPath + 'fpgui' + Copy(lFile, lPos, Length(lFile)-lPos+1);
  {$IFDEF DEBUG}
  writeln('  lFile = ', lFile);
  writeln('  ResUnitName="', ResUnitName, '"');
  writeln('  AFilename="', AFilename, '"');
  {$ENDIF}

  if {(ResUnitName = '') or} (AFilename = '') or (not FileExists(AFilename)) then
    ToolkitOnly := True;  // we don't have a application translation file
  try
    po := nil;
    // read .po file
    if ToolkitOnly then
    begin
      if not FileExists(lFile) then
        Exit;
      {$IFDEF DEBUG}
      writeln('  ************  Only translating the toolkit   ***********');
      {$ENDIF}
      po := TPOFile.Create(nil);
      po.AppendFile(lFile);
    end
    else
    begin
      po := TPOFile.Create(AFilename);
      // Now append fpGUI translations
      po.AppendFile(lFile);
    end;
    try
{$ifdef ver2_0}
      for TableID := 0 to ResourceStringTableCount - 1 do
      begin
        TableCount := ResourceStringCount(TableID);

        // check if this table belongs to the ResUnitName
        if TableCount = 0 then
          continue;
        s := GetResourceStringName(TableID, 0);
        if CompareText(ResUnitName + '.', LeftStr(s, length(ResUnitName) + 1)) <> 0 then
          continue;

        // translate all resource strings of the unit
        for StringID := 0 to TableCount - 1 do
        begin
          DefValue := GetResourceStringDefaultValue(TableID, StringID);
          // get UTF8 string
          s        := po.Translate(GetResourceStringName(TableID, StringID), DefValue);

          if Length(s) > 0 then
          begin
            // convert UTF8 to current local
            s := UTF8ToSystemCharSet(s);
            SetResourceStringValue(TableID, StringID, s);
          end;
        end;
      end;
{$else ver2_0}
//      SetUnitResourceStrings(ResUnitName, @Translate, po);
      SetResourceStrings(@Translate, po);
{$endif ver2_0}
    finally
      po.Free;
    end;
    Result := True;
  except
    on e: Exception do
    begin
      DebugLn('Exception while translating ', ResUnitName);
      DebugLn(e.Message);
      DumpExceptionBackTrace;
    end;
  end;
end;

procedure TranslateUnitResourceStrings(const ResUnitName, BaseFilename, Lang, FallbackLang: string);
begin
  if {(ResUnitName = '') or} (BaseFilename = '') then
    Exit;

  if (FallbackLang <> '') then
  begin
    {$IFDEF DEBUG}
    writeln('1) Trying fallback language... ', Fallbacklang);
    {$ENDIF}
    TranslateUnitResourceStrings(ResUnitName, Format(BaseFilename, [FallbackLang]));
  end;
  if (Lang <> '') then
  begin
    {$IFDEF DEBUG}
    writeln('2) Trying language... ', Lang);
    {$ENDIF}
    TranslateUnitResourceStrings(ResUnitName, Format(BaseFilename, [Lang]));
  end;
end;

{ TPOFile }

constructor TPOFile.Create(const AFilename: string);
var
  f: TStream;
begin
  if AFilename <> '' then
    f := TFileStream.Create(AFilename, fmOpenRead);
  try
    Self.Create(f);
  finally
    if Assigned(f) then
      f.Free;
  end;
end;

constructor TPOFile.Create(AStream: TStream);
var
  Size: integer;
  s: string;
begin
  inherited Create;
  FItems          := TFPList.Create;
  FIdentifierToItem := TStringHashList.Create(False);
  FOriginalToItem := TStringHashList.Create(True);
  
  if AStream = nil then
    Exit;

  Size := AStream.Size - AStream.Position;
  if Size <= 0 then
    Exit; //==>
  SetLength(s, Size);
  AStream.Read(s[1], Size);
  ReadPOText(s);
end;

destructor TPOFile.Destroy;
var
  i: integer;
begin
  for i := 0 to FItems.Count - 1 do
    TObject(FItems[i]).Free;
  FItems.Free;
  FIdentifierToItem.Free;
  FOriginalToItem.Free;
  inherited Destroy;
end;

procedure TPOFile.ReadPOText(const s: string);
{ Read a .po file. Structure:

Example
#: lazarusidestrconsts:lisdonotshowsplashscreen
msgid "                      Do not show splash screen"
msgstr ""

}
const
  sCommentIdentifier: PChar = '#: ';
  sMsgID: PChar  = 'msgid "';
  sMsgStr: PChar = 'msgstr "';
var
  l: integer;
  LineLen: integer;
  p: PChar;
  LineStart: PChar;
  LineEnd: PChar;
  Identifier: string;
  MsgID: string;
  MsgStr: string;
  TextEnd: PChar;
begin
  if s = '' then
    Exit; //==>
  l         := Length(s);
  p         := PChar(s);
  LineStart := p;
  TextEnd   := p + l;
  while LineStart < TextEnd do
  begin
    LineEnd := LineStart;
    while (not (LineEnd^ in [#0, #10, #13])) do
      Inc(LineEnd);
    LineLen := LineEnd - LineStart;
    if LineLen > 0 then
      if CompareMem(LineStart, sCommentIdentifier, 3) then
        Identifier := copy(s, LineStart - p + 4, LineLen - 3)
      else if CompareMem(LineStart, sMsgID, 7) then
        MsgID      := UTF8CStringToUTF8String(LineStart + 7, LineLen - 8)
      else if CompareMem(LineStart, sMsgStr, 8) then
      begin
        //MsgStr:=copy(s,LineStart-p+9,LineLen-9);
        MsgStr := UTF8CStringToUTF8String(LineStart + 8, LineLen - 9);
        Add(Identifier, MsgID, MsgStr);
      end;
    LineStart := LineEnd + 1;
    while (LineStart < TextEnd) and (LineStart^ in [#10, #13]) do
      Inc(LineStart);
  end;
end;

procedure TPOFile.Add(const Identifier, OriginalValue, TranslatedValue: string);
var
  Item: TPOFileItem;
begin
  {$IFDEF DEBUG}
  writeln('TPOFile.Add: ' + Identifier + ' | ' + OriginalValue + ' | ' + TranslatedValue);
  {$ENDIF}
  if (TranslatedValue = '') then
    Exit; //==>
  Item := TPOFileItem.Create(Identifier, OriginalValue, TranslatedValue);
  FItems.Add(Item);
  FIdentifierToItem.Add(Identifier, Item);
  FOriginalToItem.Add(OriginalValue, Item);
end;

function TPOFile.Translate(const Identifier, OriginalValue: string): string;
var
  Item: TPOFileItem;
  s: string;
begin
  s := StringReplace(Identifier, '.', ':', []);
  {$IFDEF DEBUG}
  writeln('TPOFile.Translate: ' + s + '(' + Identifier + ') | ' + OriginalValue);
  {$ENDIF}
  Item := TPOFileItem(FIdentifierToItem.Data[s]);
  if Item = nil then
  begin
    {$IFDEF DEBUG}
    writeln('  identifier lookup failed, trying original value');
    {$ENDIF}
    Item := TPOFileItem(FOriginalToItem.Data[OriginalValue]);
  end;
  if Item <> nil then
  begin
    Result := Item.Translation;
    if Result = '' then
      raise Exception.Create('TPOFile.Translate Inconsistency');
  end
  else
  begin
    {$IFDEF DEBUG}
    writeln('  OriginalValue lookup failed, defaulting to original value');
    {$ENDIF}
    Result := OriginalValue;
  end;
end;

procedure TPOFile.AppendFile(const AFilename: string);
var
  Size: integer;
  s: string;
  f: TStream;
begin
  // Now fpGUI translation
  if (AFilename = '') or (not FileExists(AFilename)) then
    Exit;
  f := TFileStream.Create(AFilename, fmOpenRead);
  try
    s := '';
    Size := f.Size - f.Position;
    if Size <= 0 then
      Exit; //==>
    SetLength(s, Size);
    f.Read(s[1], Size);
    ReadPOText(s);
  finally
    f.Free;
  end;
end;

{ TPOFileItem }

constructor TPOFileItem.Create(const TheIdentifier, TheOriginal, TheTranslated: string);
begin
  Identifier  := TheIdentifier;
  Original    := TheOriginal;
  Translation := TheTranslated;
end;

end.