#!/usr/bin/python

import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
import inspect

GAP = 5

def clipVal(v, mn, mx):
   if v < mn: return mn
   if v > mx: return mx
   return v

class InnerCode(QWidget):
   def __init__(self, scrollArea):
      super().__init__(scrollArea)
      self.scrollArea = scrollArea
      self.setFont(QFont('Courier', 16))
      self.setFocusPolicy(Qt.StrongFocus)
      self.blinkcursor = False
      # Initial values:
      self.setSource('')
      self.CursorPosition = 0
      t = QTimer(self)
      t.timeout.connect(self.updateCursor)
      t.setInterval(500)
      t.start()
   def updateCursor(self):
      self.blinkcursor = not self.blinkcursor
      self.update(self.cursorX, self.cursorY, self.charWidth, self.charHeight)
   def setSource(self, src):
      self.src = src
      self.adjust()
   def setCursorPosition(self, c):
      self.cursorPosition = clipVal(c, 0, len(self.src))
      self.cursorX = self.CursorCol * self.charWidth + self.xposTXT - self.charWidth
      self.cursorY = self.CursorRow * self.charHeight - self.charHeight
      self.update()
   CursorPosition = property(lambda self: self.cursorPosition, setCursorPosition)
   @property
   def Rows(self):
      # Make this nicer:
      return self.src.split('\n')
   @property
   def CursorRow(self):
      # TODO: make this nice.
      txt = self.src[0:self.cursorPosition]
      return len(txt.split('\n'))
   @property
   def CursorCol(self):
      txt = self.src[0:self.cursorPosition]
      curLine = txt.split('\n')[-1]
      return len(curLine) + 1
   @property
   def CurrentLine(self):
      return self.getRow(self.CursorRow)
   def setRowCol(self, r, c):
      prevRows = self.Rows[:r]
      txt = '\n'.join(prevRows)
      self.CursorPosition = len(txt) + c
   def getRow(self, r):
      rows = self.Rows
      r = r - 1
      if r < 0 or r > len(rows) - 1:
         return ''
      else:
         return rows[r]
   def getChar(self, pos):
      pass
   def insertText(self, txt):
      self.setSource(self.src[0:self.CursorPosition] + txt + self.src[self.CursorPosition:])
      self.CursorPosition += len(txt)
   def deleteChar(self):
      self.setSource(self.src[0:self.CursorPosition] + self.src[self.CursorPosition+1:])
   def GotoNextChar(self):
      if self.src[self.CursorPosition] != '\n':
         self.CursorPosition += 1
   def GotoPrevChar(self):
      if self.src[self.CursorPosition - 1] != '\n':
         self.CursorPosition -= 1
   def GotoNextLine(self):
      curLine = self.CurrentLine
      c = self.CursorCol
      self.CursorPosition += len(curLine) - c + 1 # line break char!
      curLine = self.CurrentLine
      if len(curLine) < c:
         self.CursorPosition += len(curLine)
      else:
         self.CursorPosition += c
   def GotoPrevLine(self):
      c = self.CursorCol
      self.CursorPosition -= c + 1 # line break char!
      curLine = self.CurrentLine
      if len(curLine) > c:
         self.CursorPosition -= len(curLine) - c
   def paintEvent(self, event):
      # Helper variables:
      er = event.rect()
      chw, chh = self.charWidth, self.charHeight
      painter = QPainter(self)
      # Background:
      painter.fillRect(er, self.palette().color(QPalette.Base))
      painter.fillRect(QRect(self.xposLNA, er.top(), 8 * chw, er.bottom() + 1), Qt.gray)
      painter.fillRect(er.left(), (self.CursorRow - 1) * chh, er.width(), chh, Qt.yellow)
      painter.setPen(Qt.gray)
      # first and last row:
      row1 = max(int(er.top() / chh) - 1, 1)
      row2 = max(int(er.bottom() / chh) + 1, 1)
      # Draw contents:
      for row in range(row1, row2 + 1):
         ypos = row * chh - self.charDescent
         painter.setPen(Qt.black)
         painter.drawText(self.xposLNA, ypos, 'R ={0}'.format(row))
         xpos = self.xposTXT
         painter.drawText(xpos, ypos, self.getRow(row))
      # cursor
      if self.blinkcursor:
         painter.fillRect(self.cursorX, self.cursorY, 2, chh, Qt.black)
   def keyPressEvent(self, event):
      if event.matches(QKeySequence.MoveToNextChar):
         self.GotoNextChar()
      elif event.matches(QKeySequence.MoveToPreviousChar):
         self.GotoPrevChar()
      elif event.matches(QKeySequence.MoveToNextLine):
         self.GotoNextLine()
      elif event.matches(QKeySequence.MoveToPreviousLine):
         self.GotoPrevLine()
      elif event.matches(QKeySequence.MoveToNextPage):
         for i in range(5):
            self.GotoNextLine()
      elif event.matches(QKeySequence.MoveToPreviousPage):
         for i in range(5):
            self.GotoPrevLine()
      elif event.matches(QKeySequence.MoveToEndOfLine):
         self.CursorPosition += len(self.CurrentLine) - self.CursorCol + 1
      elif event.matches(QKeySequence.MoveToStartOfLine):
         self.CursorPosition -= self.CursorCol - 1
      elif event.matches(QKeySequence.Delete):
         self.deleteChar()
      elif event.matches(QKeySequence.InsertParagraphSeparator):
         self.insertText('\n')
      elif event.key() == Qt.Key_Backspace:
         self.CursorPosition -= 1
         self.deleteChar()
      else:
         char = event.text()
         if char:
            self.insertText(char)
      self.update()
   def mousePressEvent(self, event):
      pos = event.pos()
      if pos.x() > self.xposTXT and pos.x():
         c = round((pos.x() - self.xposTXT) / self.charWidth)
         r = int(pos.y() / self.charHeight)
         self.setRowCol(r, c)
   def adjust(self):
      metrics = self.fontMetrics()
      self.charHeight = metrics.height()
      self.charWidth = metrics.width('x')
      self.charDescent = metrics.descent()
      self.xposLNA = GAP
      self.xposTXT = self.xposLNA + 8 * self.charWidth + GAP
      self.xposEnd = self.xposTXT + self.charWidth * 80
      self.setMinimumWidth(self.xposEnd)
      txt = self.src.split('\n')
      self.setMinimumHeight(self.charHeight * len(txt))
      self.update()

class CodeEdit(QScrollArea):
   def __init__(self):
      super().__init__()
      self.ic = InnerCode(self)
      self.setWidget(self.ic)
      self.setWidgetResizable(True)
      self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
      self.setFocusPolicy(Qt.NoFocus)
   Source = property(lambda s: s.ic.getSource(), lambda s, v: s.ic.setSource(v))

if __name__ == '__main__':
   app = QApplication(sys.argv)
   ce = CodeEdit()
   ce.show()
   src = ''.join(inspect.getsourcelines(InnerCode)[0])
   ce.Source = src
   ce.resize(600, 800)
   app.exec()