"""Basic regular expression demostration facility (Perl style syntax).

This displays a window with two type-in boxes.  In the top box, you
enter a Perl style regular expression.  In the bottom box, you enter a
string.  The first match in the string of the regular expression is
highlighted with a yellow background (or red if the match is empty --
then the character at the match is highlighted).  The highlighting is
continuously updated.  At the bottom are a number of checkboxes which
control the regular expression options used (see the re module for
descriptions).  When there's no match, or when the regular expression
is syntactically incorrect, an error message is displayed.

"""

from Tkinter import *
import re

class ReDemo:
	
	def __init__(self, master):
		self.master = master

		self.promptdisplay = Label(self.master, anchor=W,
			text="Enter a Perl-style regular expression:")
		self.promptdisplay.pack(side=TOP, fill=X)

		self.regexdisplay = Entry(self.master)
		self.regexdisplay.pack(fill=X)
		self.regexdisplay.focus_set()

		self.addoptions()

		self.statusdisplay = Label(self.master, text="", anchor=W)
		self.statusdisplay.pack(side=TOP, fill=X)

		self.labeldisplay = Label(self.master, anchor=W,
			text="Enter a string to search:")
		self.labeldisplay.pack(fill=X)
		self.labeldisplay.pack(fill=X)

		self.showframe = Frame(master)
		self.showframe.pack(fill=X, anchor=W)

		self.showvar = StringVar(master)
		self.showvar.set("first")

		self.showfirstradio = Radiobutton(self.showframe,
						 text="Highlight first match",
						  variable=self.showvar,
						  value="first",
						  command=self.recompile)
		self.showfirstradio.pack(side=LEFT)

		self.showallradio = Radiobutton(self.showframe,
						text="Highlight all matches",
						variable=self.showvar,
						value="all",
						command=self.recompile)
		self.showallradio.pack(side=LEFT)

		self.stringdisplay = Text(self.master, width=60, height=4)
		self.stringdisplay.pack(fill=BOTH, expand=1)
		self.stringdisplay.tag_configure("hit", background="yellow")

		self.grouplabel = Label(self.master, text="Groups:", anchor=W)
		self.grouplabel.pack(fill=X)

		self.grouplist = Listbox(self.master)
		self.grouplist.pack(expand=1, fill=BOTH)

		self.regexdisplay.bind('<Key>', self.recompile)
		self.stringdisplay.bind('<Key>', self.reevaluate)

		self.compiled = None
		self.recompile()

		btags = self.regexdisplay.bindtags()
		self.regexdisplay.bindtags(btags[1:] + btags[:1])

		btags = self.stringdisplay.bindtags()
		self.stringdisplay.bindtags(btags[1:] + btags[:1])
	
	def addoptions(self):
		self.frames = []
		self.boxes = []
		self.vars = []
		for name in ('IGNORECASE',
			     'LOCALE',
			     'MULTILINE',
			     'DOTALL',
			     'VERBOSE'):
			if len(self.boxes) % 3 == 0:
				frame = Frame(self.master)
				frame.pack(fill=X)
				self.frames.append(frame)
			val = getattr(re, name)
			var = IntVar()
			box = Checkbutton(frame,
				variable=var, text=name,
				offvalue=0, onvalue=val,
				command=self.recompile)
			box.pack(side=LEFT)
			self.boxes.append(box)
			self.vars.append(var)
	
	def getflags(self):
		flags = 0
		for var in self.vars:
			flags = flags | var.get()
		flags = flags
		return flags
	
	def recompile(self, event=None):
		try:
			self.compiled = re.compile(self.regexdisplay.get(),
						   self.getflags())
			bg = self.promptdisplay['background']
			self.statusdisplay.config(text="", background=bg)
		except re.error, msg:
			self.compiled = None
			self.statusdisplay.config(
				text="re.error: %s" % str(msg),
				background="red")
		self.reevaluate()
	
	def reevaluate(self, event=None):
		try:
			self.stringdisplay.tag_remove("hit", "1.0", END)
		except TclError:
			pass
		try:
			self.stringdisplay.tag_remove("hit0", "1.0", END)
		except TclError:
			pass
		self.grouplist.delete(0, END)
		if not self.compiled:
			return
		self.stringdisplay.tag_configure("hit", background="yellow")
		self.stringdisplay.tag_configure("hit0", background="orange")
		text = self.stringdisplay.get("1.0", END)
		last = 0
		nmatches = 0
		while last <= len(text):
			m = self.compiled.search(text, last)
			if m is None:
				break
			first, last = m.span()
			if last == first:
				last = first+1
				tag = "hit0"
			else:
				tag = "hit"
			pfirst = "1.0 + %d chars" % first
			plast = "1.0 + %d chars" % last
			self.stringdisplay.tag_add(tag, pfirst, plast)
			if nmatches == 0:
				self.stringdisplay.yview_pickplace(pfirst)
				groups = list(m.groups())
				groups.insert(0, m.group())
				for i in range(len(groups)):
					g = "%2d: %s" % (i, `groups[i]`)
					self.grouplist.insert(END, g)
			nmatches = nmatches + 1
			if self.showvar.get() == "first":
				break

		if nmatches == 0:
			self.statusdisplay.config(text="(no match)",
						  background="yellow")
		else:
			self.statusdisplay.config(text="")


# Main function, run when invoked as a stand-alone Python program.

def main():
    root = Tk()
    demo = ReDemo(root)
    root.protocol('WM_DELETE_WINDOW', root.quit)
    root.mainloop()

if __name__ == '__main__':
    main()