unit uengShaderGeneratorArgs;

{$mode objfpc}{$H+}
{$I uengShaderFile.inc}

interface

uses
  Classes, SysUtils,
  uengShaderFileTypes, uengShaderPart

{$IFDEF USE_BITSPACE_UTILS}
  , uutlGenerics
{$ENDIF}
  ;

type
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  TengGenerateFlag = (
    gfGenerateProcedureCode,    // generate procedure code
    gfGenerateProcedureCall,    // generate procedure call
    gfGenerateInlineCode,       // generate procedure as inline code
    gfGenerateParameterCode,    // generate code for parameter items
    gfAddProcedureItem,         // add procedure item to generator args
    gfAddParameterItem          // add parameter items to generator args
  );
  TengGenerateFlags = set of TengGenerateFlag;
  TengGenerateFlagsStack = specialize TutlSimpleList<TengGenerateFlags>;

  TengPopCodeFlag = (
    pcfAppend,
    pcfPrepend,
    pcfAddEmptyLine
  );
  TengPopCodeFlags = set of TengPopCodeFlag;

  TengShaderGeneratorArgs = class(TObject)
  private type
    TengGeneratorToken = (
      gtNormal          = 0,  // normal text
      gtLineBreak       = 1,  // line break
      gtCommandEnd      = 2,  // command end (like ';')
      gtBlockBegin      = 3,  // code block begin (to calculate indent)
      gtBlockEnd        = 4,  // code block end (to calculate indent)
      gtAppendToPrev    = 5,  // append current line to prev line
      gtToken           = 6   // code token (like '$INCLUDE' or '$IF')
    );

    TCodePart = class(TObject)
    private
      fText: String;
      fIndent: Integer;
      fToken: TengGeneratorToken;
      function GetDebugText: String;
      function GetCode: String;
    public
      property Text:      String             read fText write fText;
      property Code:      String             read GetCode;
      property DebugText: String             read GetDebugText;
      property Indent:    Integer            read fIndent;
      property Token:     TengGeneratorToken read fToken;
      constructor Create(const aToken: TengGeneratorToken; const aText: String; const aIndent: Integer = 0);
    end;
    TCodePartList = specialize TutlSimpleList<TCodePart>;

  public type
    TCodeStackItem = class(TObject)
    private
      fItems: TCodePartList;
      function GetIsEmpty: Boolean;
    public
      property Items:   TCodePartList read fItems;
      property IsEmpty: Boolean       read GetIsEmpty;

      procedure GenerateCode(const aCode: TengShaderCode);
      procedure Merge(const aItem: TCodeStackItem; aIndex: Integer);

      constructor Create;
      destructor Destroy; override;
    end;

  private type
    TCodeStack = specialize TutlSimpleList<TCodeStackItem>;
    TParameterMap = specialize TutlMap<string, TengShaderPart>;
    TProcedureList = specialize TutlSimpleList<TengShaderPart>;
    TProcParamStack = specialize TutlSimpleList<TStrings>;

  private
    fInlineReturnCounter: Integer;
    fCode: TCodeStack;
    fRoot: TengShaderPart;
    fFlagStack: TengGenerateFlagsStack;
    fMetaDataList: TengMetaDataList;
    fParameters: TParameterMap;
    fProcedures: TProcedureList;
    fProcParams: TProcParamStack;

    fMaxParameterLength: Integer;

    function GetFlags: TengGenerateFlags;
    function GetProcParams: TStrings;

    procedure GenerateParameterCode(const aTypes: CengShaderPartArr);
    procedure GenerateProcedureCode;
    procedure GenerateMetaCode;
  public
    property Root:               TengShaderPart    read fRoot;
    property Flags:              TengGenerateFlags read GetFlags;
    property ProcParams:         TStrings          read GetProcParams;
    property MaxParameterLength: Integer           read fMaxParameterLength;

    procedure PushCode;
    procedure PushFlags(const aFlags: TengGenerateFlags);
    procedure PushProcParams(const aParams: TStrings);

    procedure PopCode(const aFlags: TengPopCodeFlags);
    procedure PopFlags;
    procedure PopProcParams;

    function AddText(const aText: String): TengShaderGeneratorArgs;
    function AddToken(const aToken: String): TengShaderGeneratorArgs;
    function AddCommandEnd(const aToken: String): TengShaderGeneratorArgs;
    function AddLineBreak: TengShaderGeneratorArgs;
    function BeginBlock(const aIndent: Integer = 0): TengShaderGeneratorArgs;
    function EndBlock(const aCanAppend: Boolean = false): TengShaderGeneratorArgs;
    function AppendToPrevLine: TengShaderGeneratorArgs;

    procedure AddMeta(const aMeta: TengMetaData);
    procedure AddParameter(const aParam: TengShaderPart);
    procedure AddProcedure(const aProc: TengShaderPart);

    function ExtractCurrentCommand(const aCommand: TCodeStackItem): Integer;
    procedure ReplaceIdents(const aOld, aNew: TStrings);
    procedure ReplaceReturns(const aCommand: TCodeStackItem; const aRetType, aName: String);

    procedure GenerateCode(const aCode: TengShaderCode);

    constructor Create(const aRoot: TengShaderPart);
    destructor Destroy; override;
  end;

implementation

uses
  Math, RegExpr,
  uengShaderFileHelper, uengShaderFileConstants, uengShaderPartParameter, uengShaderPartProc;

const
  WHITESPACES = [' ', #9];

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//TengShaderGeneratorArgs.TCodePart///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.TCodePart.GetCode: String;
begin
  case fToken of
    gtNormal,
    gtCommandEnd:
      result := fText;
    gtLineBreak:
      result := sLineBreak;
  else
    result := '';
  end;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.TCodePart.GetDebugText: String;
begin
  case fToken of
    gtNormal:         result := '[N]' + fText;
    gtLineBreak:      result := sLineBreak;
    gtCommandEnd:     result := '[C]' + fText;
    gtBlockBegin:     result := format('[B%d]', [fIndent]);
    gtBlockEnd:       result := '[E]';
    gtToken:          result := '[T' + fText + ']';
    gtAppendToPrev:   result := '[A]';
  else
    result := '[' + IntToStr(Integer(fToken)) + ']' + fText
  end;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
constructor TengShaderGeneratorArgs.TCodePart.Create(const aToken: TengGeneratorToken; const aText: String; const aIndent: Integer);
begin
  inherited Create;
  fToken  := aToken;
  fText   := aText;
  fIndent := aIndent;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//TengShaderGeneratorArgs.TCodeStackItem//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.TCodeStackItem.GetIsEmpty: Boolean;
begin
  result := (fItems.Count = 0);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.TCodeStackItem.GenerateCode(const aCode: TengShaderCode);
type
  TGenFlag = (
    gfToken,          // current line has a token in it
    gfTokenOnly,      // current line has only a token (or whitespaces) in it
    gfPrevIsEmpty,    // previouse line was empty (or whitespaces only)
    gfCodeIsEmpty,    // nothing has added to code
    gfAddToPrev       // add current line to previouse line
  );
  TGenFlags = set of TGenFlag;

var
  i: Integer;
  f: TGenFlags;
  line: String;

  function GetStrOffset(const aStr: String): Integer;
  var
    len: Integer;
  begin
    result := 0;
    len := Length(aStr);
    while (result < len) and (aStr[result+1] in WHITESPACES) do
      inc(result);
  end;

  function GetOffset(const aCodePart: TCodePart): Integer;
  begin
    result := GetStrOffset(line);
  end;

  function GetMinOffset(aStartIndex: Integer): Integer;
  begin
    if (Trim(line) <> '')
      then result := GetStrOffset(line)
      else result := High(Integer);
    while (aStartIndex < aCode.Count) do begin
      if (Trim(aCode[aStartIndex]) <> '') then
        result := Min(result, GetStrOffset(aCode[aStartIndex]));
      inc(aStartIndex);
    end;
    if (result >= High(Integer)) then
      result := 0;
  end;

  function TrimLeftLen(const aStr: String; aLen: Integer): String;
  var
    i, len: Integer;
  begin
    i   := 1;
    len := Length(aStr);
    while (i <= len) and (aStr[i] in WHITESPACES) and (aLen > 0) do begin
      inc(i);
      dec(aLen);
    end;
    result := Copy(aStr, i, len - i + 1);
  end;

  function PrepareStr(const aStr: String; const aOffset: Integer): String;
  begin
    if (aOffset > 0)
      then result := StringOfChar(' ', aOffset) + aStr
      else result := TrimLeftLen(aStr, -aOffset);
  end;

  procedure IndentBlock(aStartIndex: Integer; const aIndent: Integer);
  var
    o: Integer;
  begin
    o := aIndent - GetMinOffset(aStartIndex);
    while (aStartIndex < aCode.Count) do begin
      aCode[aStartIndex] := PrepareStr(aCode[aStartIndex], o);
      inc(aStartIndex);
    end;
    if (Trim(line) <> '') then
      line := PrepareStr(line, o);
  end;

  procedure ProgressBlock(const aIndent: Integer);
  var
    s: String;
    cp: TCodePart;
    FirstLineIndex: Integer;
  begin
    FirstLineIndex := aCode.Count;
    while (i < fItems.Count) do begin
      cp := fItems[i];
      inc(i);

      case cp.Token of
        gtLineBreak: begin
          if (Trim(line) = '') then begin
            if (f * [gfTokenOnly, gfPrevIsEmpty] = []) then begin
              aCode.Add(line);
              Include(f, gfPrevIsEmpty);
            end;
          end else begin
            if (gfAddToPrev in f) and not (gfCodeIsEmpty in f)
              then aCode[aCode.Count-1] := aCode[aCode.Count-1] + TrimLeft(line)
              else aCode.Add(line);
            Exclude(f, gfPrevIsEmpty);
            Exclude(f, gfCodeIsEmpty);
          end;
          Exclude(f, gfToken);
          Exclude(f, gfTokenOnly);
          Exclude(f, gfAddToPrev);
          line := '';
        end;

        gtToken: begin
          Include(f, gfToken);
          if (Trim(line) = '') then
            Include(f, gfTokenOnly);
        end;

        gtBlockBegin: begin
          Include(f, gfPrevIsEmpty);
          ProgressBlock(GetStrOffset(line) + cp.Indent);
        end;

        gtBlockEnd: begin
          IndentBlock(FirstLineIndex, aIndent);
          exit;
        end;

        gtAppendToPrev: begin
          if (Trim(line) = '') and not (gfPrevIsEmpty in f) then
            include(f, gfAddToPrev);
        end;
      else
        s := cp.Code;
        line := line + s;
      end;
    end;
  end;

{$IFDEF DEBUG}
  procedure GenerateDebugCode;
  var
    cp: TCodePart;
    s: String;
    sl: TStringList;
  begin
    s := '';
    for cp in fItems do
      s := s + cp.DebugText;
    sl := TStringList.Create;
    try
      sl.Text := s;
      sl.SaveToFile('C:\Users\Erik\Desktop\tmp\debug.txt');
    finally
      FreeAndNil(sl);
    end;
  end;
{$ENDIF}

begin
  i    := 0;
  f    := [gfPrevIsEmpty, gfCodeIsEmpty];
  line := '';
{$IFDEF DEBUG}
  GenerateDebugCode;
{$ENDIF}
  ProgressBlock(0);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.TCodeStackItem.Merge(const aItem: TCodeStackItem; aIndex: Integer);
begin
  if (aIndex < 0) then
    aIndex := 0;
  if (aIndex > fItems.Count) then
    aIndex := fItems.Count;
  while (aItem.Items.Count > 0) do
    fItems.Insert(aIndex, aItem.Items.PopLast(false));
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
constructor TengShaderGeneratorArgs.TCodeStackItem.Create;
begin
  inherited Create;
  fItems := TCodePartList.Create(true);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
destructor TengShaderGeneratorArgs.TCodeStackItem.Destroy;
begin
  FreeAndNil(fItems);
  inherited Destroy;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//TengShaderGeneratorArgs///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.GetFlags: TengGenerateFlags;
begin
  result := fFlagStack.Last;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.GetProcParams: TStrings;
begin
  result := fProcParams.Last;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.GenerateParameterCode(const aTypes: CengShaderPartArr);
var
  m: TParameterMap;
  p: TengShaderPart;
begin
  PushCode;
  PushFlags(Flags + [gfGenerateParameterCode] - [gfAddParameterItem]);
  m := TParameterMap.Create(false);
  try
    fMaxParameterLength := 0;
    for p in fParameters do begin
      if CheckType(p, aTypes) then with (p as TengShaderPartParameter) do begin
        fMaxParameterLength := Max(fMaxParameterLength, Length(Typ));
        m.Add(Typ+Name, p);
      end;
    end;
    for p in m do begin
      (p as TengShaderPartParameter).GenerateCodeIntern(self);
      AddLineBreak;
    end;
  finally
    FreeAndNil(m);
    PopFlags;
    PopCode([pcfPrepend, pcfAddEmptyLine]);
  end;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.GenerateProcedureCode;
var
  i: Integer;
begin
  i := 0;
  while (i < fProcedures.Count) do begin
    PushCode;
    PushFlags([gfGenerateProcedureCode, gfAddParameterItem]);
    try
      (fProcedures[i] as TengShaderPartProc).GenerateCodeIntern(self);
    finally
      PopFlags;
      PopCode([pcfPrepend, pcfAddEmptyLine]);
    end;
    inc(i);
  end;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.GenerateMetaCode;
var
  layouts: TStringList;
  m: TengMetaData;
  vCompat: Boolean;
  vMax, i: Integer;
  s: String;
begin
  PushCode;
  vMax    := 0;
  vCompat := false;
  layouts := TStringList.Create;
  try
    for m in fMetaDataList do begin
      case m.MetaType of
        metaVersion: begin
          if (m.Values[0] = VERSION_EXTRA_COMPAT) then
            vCompat := true
          else if TryStrToInt(m.Values[0], i) then
            vMax := max(vMax, i);
          if (m.Count > 1) and (m.Values[1] = VERSION_EXTRA_COMPAT) then
            vCompat := true;
        end;

        metaExtension: begin
          AddText(format('#extension %s : %s', [m.Values[0], m.Values[1]]));
          AddLineBreak;
        end;

        metaLayout: begin
          layouts.Add('layout' + m.Values[0] + ';');
        end;
      end;
    end;

    if (vMax >= LAYOUT_MIN_VERSION) then begin
      for s in layouts do begin
        AddText(s);
        AddLineBreak;
      end;
    end;

    if (vMax > 0) then begin
      PushCode;
      try
        AddText('#version ' + IntToStr(vMax));
        if vCompat then
          AddText(' ' + VERSION_EXTRA_COMPAT);
        AddLineBreak;
      finally
        PopCode([pcfPrepend]);
      end;
    end;
  finally
    PopCode([pcfPrepend, pcfAddEmptyLine]);
    FreeAndNil(layouts);
  end;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.PushCode;
begin
  fCode.PushLast(TCodeStackItem.Create);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.PushFlags(const aFlags: TengGenerateFlags);
begin
  fFlagStack.PushLast(aFlags);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.PushProcParams(const aParams: TStrings);
begin
  fProcParams.PushLast(aParams);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.PopCode(const aFlags: TengPopCodeFlags);
var
  csi: TCodeStackItem;
begin
  csi := fCode.PopLast(false);
  try
    if csi.IsEmpty then
      exit;
    if (pcfPrepend in aFlags) then begin
      if (pcfAddEmptyLine in aFlags) then
        csi.Items.Add(TCodePart.Create(gtLineBreak, ''));
      fCode.Last.Merge(csi, 1);
    end else if (pcfAppend in aFlags) then begin
      if (pcfAddEmptyLine in aFlags) then
        fCode.Last.Items.Add(TCodePart.Create(gtLineBreak, ''));
      fCode.Last.Merge(csi, fCode.Last.Items.Count);
    end;
  finally
    FreeAndNil(csi);
  end;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.PopFlags;
begin
  fFlagStack.PopLast(true);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.PopProcParams;
begin
  fProcParams.PopLast;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.AddText(const aText: String): TengShaderGeneratorArgs;
begin
  fCode.Last.Items.Add(TCodePart.Create(gtNormal, aText));
  result := self;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.AddToken(const aToken: String): TengShaderGeneratorArgs;
begin
  fCode.Last.Items.Add(TCodePart.Create(gtToken, aToken));
  result := self;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.AddCommandEnd(const aToken: String): TengShaderGeneratorArgs;
begin
  fCode.Last.Items.Add(TCodePart.Create(gtCommandEnd, aToken));
  result := self;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.AddLineBreak: TengShaderGeneratorArgs;
begin
  fCode.Last.Items.Add(TCodePart.Create(gtLineBreak, ''));
  result := self;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.BeginBlock(const aIndent: Integer): TengShaderGeneratorArgs;
begin
  fCode.Last.Items.Add(TCodePart.Create(gtBlockBegin, '', aIndent));
  result := self;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.EndBlock(const aCanAppend: Boolean): TengShaderGeneratorArgs;
begin
  fCode.Last.Items.Add(TCodePart.Create(gtBlockEnd, ''));
  result := self;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.AppendToPrevLine: TengShaderGeneratorArgs;
begin
  fCode.Last.Items.Add(TCodePart.Create(gtAppendToPrev, ''));
  result := self;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.AddMeta(const aMeta: TengMetaData);
begin
  fMetaDataList.Add(aMeta);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.AddParameter(const aParam: TengShaderPart);
var
  p: TengShaderPart;
  s: String;
begin
  if not (aParam is TengShaderPartParameter) then
    raise EengShaderPartInternal.Create('parameter (' + aParam.ClassName + ') is not a ' + TengShaderPartParameter.ClassName, aParam);
  with (aParam as TengShaderPartParameter) do begin
    p := fParameters[Name];
    if Assigned(p) then begin
      s := Format('use of duplicate identifier: %s (%s %d:%d)', [Name, Filename, Line + 1, Col]) + sLineBreak +
                  'previously declared here:' + sLineBreak +
                  Format('  %s %d:%d', [p.Filename, p.Line + 1, p.Col]) + sLineBreak;
      fRoot.LogMsg(llWarning, s);
      fParameters[Name] := aParam;
    end else
      fParameters.Add(Name, aParam);
  end;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.AddProcedure(const aProc: TengShaderPart);
begin
  if not (aProc is TengShaderPartProc) then
    raise EengShaderPartInternal.Create('parameter (' + aProc.ClassName + ') is not a ' + TengShaderPartProc.ClassName, aProc);
  fProcedures.Add(aProc);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
function TengShaderGeneratorArgs.ExtractCurrentCommand(const aCommand: TCodeStackItem): Integer;
var
  csi: TCodeStackItem;
  i, len: Integer;
  s: String;
begin
  csi := fCode.Last;
  if not Assigned(aCommand) then
    exit;

  // find last command end token
  while (csi.Items.Last.Token <> gtCommandEnd) do
    aCommand.Items.PushFirst(csi.Items.PopLast(false));

  // move forward to first code part with text
  while (aCommand.Items.First.Token <> gtNormal) or (Trim(aCommand.Items.First.Text) = '') do
    csi.Items.PushLast(aCommand.Items.PopFirst(false));

  // extract leading whitespaces
  i := 1;
  s := aCommand.Items.First.Text;
  len := Length(s);
  while (s[i] in WHITESPACES) and (i <= len) do
    inc(i);
  csi.Items.PushLast(TCodePart.Create(gtNormal, Copy(s, 1, i-1)));
  aCommand.Items.First.Text := copy(s, i, len-i+1);
  result := i - 1;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.ReplaceIdents(const aOld, aNew: TStrings);
var
  rx: TRegExpr;
  i: Integer;
  cp: TCodePart;
begin
  if (aOld.Count <> aNew.Count) then
    raise EengShaderPartInternal.Create('old and new ident must have the same size');
  rx := TRegExpr.Create;
  try
    for i := 0 to aOld.Count-1 do begin
      rx.Expression := '([^A-z0-9_]+|^)' + aOld[i] + '([^A-z0-9_]+|$)';
      for cp in fCode.Last.Items do
        cp.Text := rx.Replace(cp.Text, '$1' + aNew[i] + '$2', true);
    end;
  finally
    FreeAndNil(rx);
  end;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.ReplaceReturns(const aCommand: TCodeStackItem; const aRetType, aName: String);
var
  rx: TRegExpr;
  RetCount, i, j: Integer;
  csi: TCodeStackItem;
  cp: TCodePart;
  s: String;
begin
  rx := TRegExpr.Create;
  try
    rx.Expression := '([^A-z0-9_]+|^)return([^A-z0-9_]+|$)';
    csi := fCode.Last;

    // find number of "return" in code
    RetCount := 0;
    for cp in csi.Items do begin
      s := cp.Code;
      if rx.Exec(s) then
        inc(RetCount);
    end;

    // no "return" found
    if (RetCount = 0) then begin
      raise EengShaderPartInternal.Create('expected "return" token in function');

    // more than one "return"
    end else if (RetCount > 1) then begin
      // find block begin
      i := 0;
      while (csi.Items[i].Token <> gtBlockBegin) and (i < csi.Items.Count) do
        inc(i);
      if (i < csi.Items.Count)
        then inc(i)
        else i := 0;

      // insert temp variable
      s := Format('%s_ret%.4d', [aName, fInlineReturnCounter]);
      inc(fInlineReturnCounter);
      csi.Items.Insert(i,   TCodePart.Create(gtLineBreak, ''));
      csi.Items.Insert(i+1, TCodePart.Create(gtNormal, aRetType + ' ' + s));
      csi.Items.Insert(i+2, TCodePart.Create(gtCommandEnd, ';'));
      csi.Items.Insert(i+3, TCodePart.Create(gtLineBreak, ''));

      // replace "return" with temp variable
      for cp in csi.Items do
        cp.Text := rx.Replace(cp.Text, '$1' + s + ' =$2', true);

      // merge code
      csi.Merge(aCommand, csi.Items.Count);
      AddText(s);

    // exact one "return"
    end else begin
      i := csi.Items.Count-1;
      while (i > 0) do begin
        cp := csi.Items[i];
        if rx.Exec(cp.Text) then begin
          csi.Items.Insert(i, TCodePart.Create(gtNormal, rx.Match[1]));
          cp.Text := rx.Replace(cp.Text, '(', true);

          // replace last gtCommandEnd with ')' and delete everything behind
          j := csi.Items.Count-1;
          while (j > i) and not (csi.Items[j].Token = gtCommandEnd) do
            dec(j);
          if (j > i) then
            csi.Items[j] := TCodePart.Create(gtNormal, ')');
          while (csi.Items.Count-1 > j) do
            csi.Items.PopLast(true);

          // merge
          csi.Merge(aCommand, i+1);
        end;
        dec(i);
      end;
    end;
  finally
    FreeAndNil(rx);
  end;
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
procedure TengShaderGeneratorArgs.GenerateCode(const aCode: TengShaderCode);
begin
  GenerateProcedureCode;
  GenerateParameterCode(CengShaderPartArr.Create(TengShaderPartVar));
  GenerateParameterCode(CengShaderPartArr.Create(TengShaderPartVarying));
  GenerateParameterCode(CengShaderPartArr.Create(TengShaderPartUniform));
  GenerateMetaCode;
  fCode.Last.GenerateCode(aCode);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
constructor TengShaderGeneratorArgs.Create(const aRoot: TengShaderPart);
begin
  inherited Create;
  fCode         := TCodeStack.Create(true);
  fFlagStack    := TengGenerateFlagsStack.Create();
  fMetaDataList := TengMetaDataList.Create(false);
  fParameters   := TParameterMap.Create(false);
  fProcedures   := TProcedureList.Create(false);
  fProcParams   := TProcParamStack.Create(false);
  fRoot         := aRoot;
  fInlineReturnCounter := 0;
  PushCode;
  PushFlags([ gfAddParameterItem, gfAddProcedureItem ]);
end;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
destructor TengShaderGeneratorArgs.Destroy;
begin
  FreeAndNil(fProcParams);
  FreeAndNil(fProcedures);
  FreeAndNil(fParameters);
  FreeAndNil(fMetaDataList);
  FreeAndNil(fFlagStack);
  FreeAndNil(fCode);
  inherited Destroy;
end;

end.