unit uMain;

interface

uses
   Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
   System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs,
   Vcl.StdCtrls, Vcl.Menus, Vcl.ComCtrls, uAlgo;

type
   TMainForm = class(TForm)
    tvTree: TTreeView;
    mmMainMenu: TMainMenu;
    miHelp: TMenuItem;
    miAbout: TMenuItem;
    eKey: TEdit;
    bCreate: TButton;
    bAdd: TButton;
    bRemove: TButton;
    bLength: TButton;
    pmPopupMenu: TPopupMenu;
    laAnswer: TLabel;
    bClear: TButton;
    procedure DisplayTree(TreeNode: TTreeNode; Node: PNode);
    procedure bCreateClick(Sender: TObject);
    procedure eKeyChange(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure bAddClick(Sender: TObject);
    procedure bRemoveClick(Sender: TObject);
    procedure bLengthClick(Sender: TObject);
    procedure miHelpClick(Sender: TObject);
    procedure miAboutClick(Sender: TObject);
    procedure bClearClick(Sender: TObject);
    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
   private
    { Private declarations }
   public
    { Public declarations }
   end;

var
   MainForm: TMainForm;
   Root: PNode;

implementation

{$R *.dfm}

procedure TMainForm.DisplayTree(TreeNode: TTreeNode; Node: PNode);
var
   NewNode: TTreeNode;
begin
   if Node <> nil then
   begin
      NewNode := tvTree.Items.AddChild(TreeNode, IntToStr(Node.Key));
      DisplayTree(NewNode, Node.Right);
      DisplayTree(NewNode, Node.Left);
   end;
end;

procedure TMainForm.bClearClick(Sender: TObject);
begin
   DeleteAll(Root);
   Root := nil;
   tvTree.Items.Clear;
   bClear.Enabled := False;
   bLength.Enabled := False;
   laAnswer.Caption := '';
end;

procedure TMainForm.bCreateClick(Sender: TObject);
begin
   New(Root);
   Root.Left := nil;
   Root.Right := nil;
   Root.Key := StrToInt(eKey.Text);
   tvTree.Items.Clear;
   DisplayTree(nil, Root);
   tvTree.FullExpand;
   bLength.Enabled := True;
   bClear.Enabled := True;
   eKey.Text := '';
   eKey.SetFocus;
end;

procedure TMainForm.bLengthClick(Sender: TObject);
var
   Length: Byte;
begin
   Length := MaxDepth(Root.Left) + MaxDepth(Root.Right);
   if Length <> 0 then
      Dec(Length);
   laAnswer.Caption := 'Max length between nodes with different amount of сhilds: '
     + IntToStr(Length);
   laAnswer.Width := 150;
   bLength.Enabled := False;
end;

procedure TMainForm.bAddClick(Sender: TObject);
begin
   if not Exists(Root, StrToInt(eKey.Text)) then
   begin
      Root := Add(Root, StrToInt(eKey.Text));
      laAnswer.Caption := '';
      bLength.Enabled := True;
      bClear.Enabled := True;
   end
   else
      MessageDlg('This element already exists.',
        mtError, [mbOK], 0);
   tvTree.Items.Clear;
   DisplayTree(nil, Root);
   tvTree.FullExpand;
   eKey.Text := '';
   eKey.SetFocus;
end;

procedure TMainForm.bRemoveClick(Sender: TObject);
begin
   if Exists(Root, StrToInt(eKey.Text)) then
   begin
      Root := Remove(Root, StrToInt(eKey.Text));
      laAnswer.Caption := '';
      if Root = nil then
      begin
         bLength.Enabled := False;
         bClear.Enabled := False;
      end
      else
         bLength.Enabled := True;
   end
   else
      MessageDlg('There are no such elements in the tree.',
        mtError, [mbOK], 0);
   tvTree.Items.Clear;
   DisplayTree(nil, Root);
   tvTree.FullExpand;
   eKey.Text := '';
   eKey.SetFocus;
end;

procedure TMainForm.eKeyChange(Sender: TObject);
begin
   if Length(eKey.Text) > 0 then
      if Root = nil then
         bCreate.Enabled := True
      else
      begin
         bAdd.Enabled := True;
         bRemove.Enabled := True;
      end
   else
   begin
      bCreate.Enabled := False;
      bAdd.Enabled := False;
      bRemove.Enabled := False;
   end;
end;

procedure TMainForm.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
   if MessageDlg('Are you sure to close the program?', mtConfirmation,
     mbYesNo, 0) = mrYes then
      CanClose := True
   else
      CanClose := False;
end;

procedure TMainForm.FormCreate(Sender: TObject);
begin
   Root := nil;
end;

procedure TMainForm.miAboutClick(Sender: TObject);
begin
   ShowMessage('Zhenya Yakubovich, 851001');
end;

procedure TMainForm.miHelpClick(Sender: TObject);
begin
   ShowMessage('This program allows you to:' + #13#10 +
     '   - view tree;' + #13#10 +
     '   - build an empty tree;' + #13#10 +
     '   - add new items;' + #13#10 +
     '   - delete specified items;' + #13#10 +
     '   - find max length of path between items' + #13#10 +
     '     with different amount of childs.');
end;

end.