import re
from Tkinter import *
import tkMessageBox

def get(root):
    if not hasattr(root, "_searchengine"):
        root._searchengine = SearchEngine(root)
        # XXX This will never garbage-collect 
    return root._searchengine

class SearchEngine:

    def __init__(self, root):
        self.root = root
       

    # Access methods

    def getpat(self):
        return self.patvar.get()

    def setpat(self, pat):
        self.patvar.set(pat)

    def isre(self):
        return self.revar.get()

    def iscase(self):
        return self.casevar.get()

    def isword(self):
        return self.wordvar.get()

    def iswrap(self):
        return self.wrapvar.get()

    def isback(self):
        return self.backvar.get()

    # Higher level access methods

    def getcookedpat(self):
        pat = self.getpat()
        if not self.isre():
            pat = re.escape(pat)
        if self.isword():
            pat = r"\b%s\b" % pat
        return pat

    def getprog(self):
        pat = self.getpat()
        if not pat:
            self.report_error
            return None
        pat = self.getcookedpat()
        flags = 0
        if not self.iscase():
            flags = flags | re.IGNORECASE
        try:
            prog = re.compile(pat, flags)
        except re.error, what:
            try:
                msg, col = what
            except:
                msg = str(what)
                col = -1
            self.report_error(pat, msg, col)
            return None
        return prog

    def report_error(self, pat, msg, col=-1):
        # Derived class could overrid this with 
        msg = "Error: " + str(msg)
        if pat:
            msg = msg + "\np\Pattern: " + str(pat)
        if col >= 0:
            msg = msg + "\nOffset: " + str(col)
        tkMessageBox.showerror("Regular expression error",
                               msg, master=self.root)

    def setcookedpat(self, pat):
        if self.isre():
            pat = re.escape(pat)
        self.setpat(pat)

    def search_text(self, text, prog=None, ok=0):
        """Search a text widget for the pattern.

        If prog is given, it should be the precompiled pattern.
        Return a tuple (lineno, matchobj); None if not found.

        This obeys the wrap and direction (back) settings.