#!python3

"""
FSA DICTIONARY BUILDER

by Olivier R.
License: MPL 2

This tool encodes lexicon into an indexable binary dictionary
Input files MUST be encoded in UTF-8.
"""

import sys
import os
import collections
import json
import time
import re
import traceback

from . import str_transform as st
from .progressbar import ProgressBar



def readFile (spf):
    "generator: read file <spf> and return for each line a list of elements separated by a tabulation."
    print(" < Read lexicon: " + spf)
    if os.path.isfile(spf):
        with open(spf, "r", encoding="utf-8") as hSrc:
            for sLine in hSrc:
                sLine = sLine.strip()
                if sLine and not sLine.startswith("#"):
                    yield sLine.split("\t")
    else:
        raise OSError("# Error. File not found or not loadable: " + spf)



class DAWG:
    """DIRECT ACYCLIC WORD GRAPH"""
    # This code is inspired from Steve Hanov’s DAWG, 2011. (http://stevehanov.ca/blog/index.php?id=115)
    # We store suffix/affix codes and tags within the graph after the “real” word.
    # A word is a list of numbers [ c1, c2, c3 . . . cN, iAffix, iTags]
    # Each arc is an index in self.lArcVal, where are stored characters, suffix/affix codes for stemming and tags.
    # Important: As usual, the last node (after ‘iTags’) is tagged final, AND the node after ‘cN’ is ALSO tagged final.

    def __init__ (self, src, cStemming, sLangCode, sLangName="", sDicName="", sSelectFilterRegex=""):
        print("===== Direct Acyclic Word Graph - Minimal Acyclic Finite State Automaton =====")
        cStemming = cStemming.upper()
        if cStemming == "A":
            funcStemmingGen = st.defineAffixCode
        elif cStemming == "S":
            funcStemmingGen = st.defineSuffixCode
        elif cStemming == "N":
            funcStemmingGen = st.noStemming
        else:
            raise ValueError("# Error. Unknown stemming code: {}".format(cStemming))

        aEntry = set()
        lChar = ['']; dChar = {}; nChar = 1; dCharOccur = {}
        lAff  = [];   dAff  = {}; nAff  = 0; dAffOccur = {}
        lTag  = [];   dTag  = {}; nTag  = 0; dTagOccur = {}
        nErr = 0

        try:
            zFilter = re.compile(sSelectFilterRegex)  if sSelectFilterRegex  else None
        except:
            print(" # Error. Wrong filter regex. Filter ignored.")
            traceback.print_exc()
            zFilter = None

        # read lexicon
        if type(src) is str:
            iterable = readFile(src)
        else:
            iterable = src
        for sFlex, sStem, sTag in iterable:
            if not zFilter or zFilter.search(sTag):
                addWordToCharDict(sFlex)
                # chars
                for c in sFlex:
                    if c not in dChar:
                        dChar[c] = nChar
                        lChar.append(c)
                        nChar += 1
                    dCharOccur[c] = dCharOccur.get(c, 0) + 1
                # affixes to find stem from flexion
                sAff = funcStemmingGen(sFlex, sStem)
                if sAff not in dAff:
                    dAff[sAff] = nAff
                    lAff.append(sAff)
                    nAff += 1
                dAffOccur[sAff] = dAffOccur.get(sAff, 0) + 1
                # tags
                if sTag not in dTag:
                    dTag[sTag] = nTag
                    lTag.append(sTag)
                    nTag += 1
                dTagOccur[sTag] = dTagOccur.get(sTag, 0) + 1
                aEntry.add((sFlex, dAff[sAff], dTag[sTag]))
        if not aEntry:
            raise ValueError("# Error. Empty lexicon")

        # Preparing DAWG
        print(" > Preparing list of words")
        print(" Filter: " + (sSelectFilterRegex or "[None]"))
        lVal = lChar + lAff + lTag
        lWord = [ [dChar[c] for c in sFlex] + [iAff+nChar] + [iTag+nChar+nAff]  for sFlex, iAff, iTag in aEntry ]
        aEntry = None

        # Dictionary of arc values occurrency, to sort arcs of each node
        dValOccur = dict( [ (dChar[c], dCharOccur[c])  for c in dChar ] \
                        + [ (dAff[aff]+nChar, dAffOccur[aff]) for aff in dAff ] \
                        + [ (dTag[tag]+nChar+nAff, dTagOccur[tag]) for tag in dTag ] )

        self.sFileName = src  if type(src) is str  else "[None]"
        self.sLangCode = sLangCode
        self.sLangName = sLangName
        self.sDicName = sDicName
        self.nEntry = len(lWord)
        self.aPreviousEntry = []
        DawgNode.resetNextId()
        self.oRoot = DawgNode()
        self.lUncheckedNodes = []  # list of nodes that have not been checked for duplication.
        self.lMinimizedNodes = {}  # list of unique nodes that have been checked for duplication.
        self.lSortedNodes = []     # version 2 and 3
        self.nNode = 0
        self.nArc = 0
        self.dChar = dChar
        self.nChar = len(dChar)
        self.nAff = nAff
        self.lArcVal = lVal
        self.nArcVal = len(lVal)
        self.nTag = self.nArcVal - self.nChar - nAff
        self.cStemming = cStemming
        if cStemming == "A":
            self.funcStemming = st.changeWordWithAffixCode
        elif cStemming == "S":
            self.funcStemming = st.changeWordWithSuffixCode
        else:
            self.funcStemming = st.noStemming

        # build
        lWord.sort()
        oProgBar = ProgressBar(0, len(lWord))
        for aEntry in lWord:
            self.insert(aEntry)
            oProgBar.increment(1)
        oProgBar.done()
        self.finish()
        self.countNodes()
        self.countArcs()
        self.sortNodes()         # version 2 and 3
        self.sortNodeArcs(dValOccur)
        #self.sortNodeArcs2 (self.oRoot, "")
        self.displayInfo()

    # BUILD DAWG
    def insert (self, aEntry):
        "insert a new entry (insertion must be made in alphabetical order)."
        if aEntry < self.aPreviousEntry:
            sys.exit("# Error: Words must be inserted in alphabetical order.")

        # find common prefix between word and previous word
        nCommonPrefix = 0
        for i in range(min(len(aEntry), len(self.aPreviousEntry))):
            if aEntry[i] != self.aPreviousEntry[i]:
                break
            nCommonPrefix += 1

        # Check the lUncheckedNodes for redundant nodes, proceeding from last
        # one down to the common prefix size. Then truncate the list at that point.
        self._minimize(nCommonPrefix)

        # add the suffix, starting from the correct node mid-way through the graph
        if len(self.lUncheckedNodes) == 0:
            oNode = self.oRoot
        else:
            oNode = self.lUncheckedNodes[-1][2]

        iChar = nCommonPrefix
        for c in aEntry[nCommonPrefix:]:
            oNextNode = DawgNode()
            oNode.arcs[c] = oNextNode
            self.lUncheckedNodes.append((oNode, c, oNextNode))
            if iChar == (len(aEntry) - 2):
                oNode.final = True
            iChar += 1
            oNode = oNextNode
        oNode.final = True
        self.aPreviousEntry = aEntry

    def finish (self):
        "minimize unchecked nodes"
        self._minimize(0)

    def _minimize (self, downTo):
        # proceed from the leaf up to a certain point
        for i in range( len(self.lUncheckedNodes)-1, downTo-1, -1 ):
            oNode, char, oChildNode = self.lUncheckedNodes[i]
            if oChildNode in self.lMinimizedNodes:
                # replace the child with the previously encountered one
                oNode.arcs[char] = self.lMinimizedNodes[oChildNode]
            else:
                # add the state to the minimized nodes.
                self.lMinimizedNodes[oChildNode] = oChildNode
            self.lUncheckedNodes.pop()

    def countNodes (self):
        "count the number of nodes of the whole word graph"
        self.nNode = len(self.lMinimizedNodes)

    def countArcs (self):
        "count the number of arcs in the whole word graph"
        self.nArc = 0
        for oNode in self.lMinimizedNodes:
            self.nArc += len(oNode.arcs)

    def sortNodeArcs (self, dValOccur):
        "sort arcs of each node according to <dValOccur>"
        print(" > Sort node arcs")
        self.oRoot.sortArcs(dValOccur)
        for oNode in self.lMinimizedNodes:
            oNode.sortArcs(dValOccur)

    def sortNodeArcs2 (self, oNode, cPrevious=""):
        "sort arcs of each node depending on the previous char"
        # recursive function
        dCharOccur = getCharOrderAfterChar(cPrevious)
        if dCharOccur:
            oNode.sortArcs2(dCharOccur, self.lArcVal)
        for nArcVal, oNextNode in oNode.arcs.items():
            self.sortNodeArcs2(oNextNode, self.lArcVal[nArcVal])

    def sortNodes (self):
        "sort nodes"
        print(" > Sort nodes")
        for oNode in self.oRoot.arcs.values():
            self._parseNodes(oNode)

    def _parseNodes (self, oNode):
        # Warning: recursive method
        if oNode.pos > 0:
            return
        oNode.setPos()
        self.lSortedNodes.append(oNode)
        for oNextNode in oNode.arcs.values():
            self._parseNodes(oNextNode)

    def lookup (self, sWord):
        "return True if <sWord> is within the word graph (debugging)"
        oNode = self.oRoot
        for c in sWord:
            if self.dChar.get(c, '') not in oNode.arcs:
                return False
            oNode = oNode.arcs[self.dChar[c]]
        return oNode.final

    def morph (self, sWord):
        "return a string of the morphologies of <sWord> (debugging)"
        oNode = self.oRoot
        for c in sWord:
            if self.dChar.get(c, '') not in oNode.arcs:
                return ''
            oNode = oNode.arcs[self.dChar[c]]
        if oNode.final:
            s = "* "
            for arc in oNode.arcs:
                if arc >= self.nChar:
                    s += " [" + self.funcStemming(sWord, self.lArcVal[arc])
                    oNode2 = oNode.arcs[arc]
                    for arc2 in oNode2.arcs:
                        s += " / " + self.lArcVal[arc2]
                    s += "]"
            return s
        return ''

    def displayInfo (self):
        "display informations about the word graph"
        print(" * {:<12} {:>16,}".format("Entries:", self.nEntry))
        print(" * {:<12} {:>16,}".format("Characters:", self.nChar))
        print(" * {:<12} {:>16,}".format("Affixes:", self.nAff))
        print(" * {:<12} {:>16,}".format("Tags:", self.nTag))
        print(" * {:<12} {:>16,}".format("Arc values:", self.nArcVal))
        print(" * {:<12} {:>16,}".format("Nodes:", self.nNode))
        print(" * {:<12} {:>16,}".format("Arcs:", self.nArc))
        print(" * {:<12} {:>16}".format("Stemming:", self.cStemming + "FX"))

    def getArcStats (self):
        "return a string with statistics about nodes and arcs"
        d = {}
        for oNode in self.lMinimizedNodes:
            n = len(oNode.arcs)
            d[n] = d.get(n, 0) + 1
        s = " * Nodes:\n"
        for n in d:
            s = s + " {:>9} nodes have {:>3} arcs\n".format(d[n], n)
        return s

    def writeInfo (self, sPathFile):
        "write informations in file <sPathFile>"
        print(" > Write informations")
        with open(sPathFile, 'w', encoding='utf-8', newline="\n") as hDst:
            hDst.write(self.getArcStats())
            hDst.write("\n * Values:\n")
            for i, s in enumerate(self.lArcVal):
                hDst.write(" {:>6}. {}\n".format(i, s))
            hDst.close()

    def select (self, sPattern=""):
        "generator: returns all entries which morphology fits <sPattern>"
        zPattern = None
        if sPattern:
            try:
                zPattern = re.compile(sPattern)
            except:
                print("# Error in regex pattern")
                traceback.print_exc()
        yield from self._select(zPattern, self.oRoot, "")

    def _select (self, zPattern, oNode, sWord):
        # recursive generator
        for nVal, oNextNode in oNode.arcs.items():
            if nVal <= self.nChar:
                # simple character
                yield from self._select(zPattern, oNextNode, sWord + self.lArcVal[nVal])
            else:
                sEntry = sWord + "\t" + self.funcStemming(sWord, self.lArcVal[nVal])
                for nMorphVal, _ in oNextNode.arcs.items():
                    if not zPattern or zPattern.search(self.lArcVal[nMorphVal]):
                        yield sEntry + "\t" + self.lArcVal[nMorphVal]


    # BINARY CONVERSION
    def _calculateBinary (self, nCompressionMethod):
        print(" > Write DAWG as an indexable binary dictionary [method: %d]" % nCompressionMethod)
        if nCompressionMethod == 1:
            self.nBytesArc = ( (self.nArcVal.bit_length() + 2) // 8 ) + 1   # We add 2 bits. See DawgNode.convToBytes1()
            self.nBytesOffset = 0
            self._calcNumBytesNodeAddress()
            self._calcNodesAddress1()
        elif nCompressionMethod == 2:
            self.nBytesArc = ( (self.nArcVal.bit_length() + 3) // 8 ) + 1   # We add 3 bits. See DawgNode.convToBytes2()
            self.nBytesOffset = 0
            self._calcNumBytesNodeAddress()
            self._calcNodesAddress2()
        elif nCompressionMethod == 3:
            self.nBytesArc = ( (self.nArcVal.bit_length() + 3) // 8 ) + 1   # We add 3 bits. See DawgNode.convToBytes3()
            self.nBytesOffset = 1
            self.nMaxOffset = (2 ** (self.nBytesOffset * 8)) - 1
            self._calcNumBytesNodeAddress()
            self._calcNodesAddress3()
        else:
            print(" # Error: unknown compression method")
        print("   Arc values (chars, affixes and tags): {}  ->  {} bytes".format( self.nArcVal, len("\t".join(self.lArcVal).encode("utf-8")) ))
        print("   Arc size: {} bytes, Address size: {} bytes   ->   {} * {} = {} bytes".format( self.nBytesArc, self.nBytesNodeAddress, \
                                                                                                self.nBytesArc+self.nBytesNodeAddress, self.nArc, \
                                                                                                (self.nBytesArc+self.nBytesNodeAddress)*self.nArc ))

    def _calcNumBytesNodeAddress (self):
        "how many bytes needed to store all nodes/arcs in the binary dictionary"
        self.nBytesNodeAddress = 1
        while ((self.nBytesArc + self.nBytesNodeAddress) * self.nArc) > (2 ** (self.nBytesNodeAddress * 8)):
            self.nBytesNodeAddress += 1

    def _calcNodesAddress1 (self):
        nBytesNode = self.nBytesArc + self.nBytesNodeAddress
        iAddr = len(self.oRoot.arcs) * nBytesNode
        for oNode in self.lMinimizedNodes:
            oNode.addr = iAddr
            iAddr += max(len(oNode.arcs), 1) * nBytesNode

    def _calcNodesAddress2 (self):
        nBytesNode = self.nBytesArc + self.nBytesNodeAddress
        iAddr = len(self.oRoot.arcs) * nBytesNode
        for oNode in self.lSortedNodes:
            oNode.addr = iAddr
            iAddr += max(len(oNode.arcs), 1) * nBytesNode
            for oNextNode in oNode.arcs.values():
                if (oNode.pos + 1) == oNextNode.pos:
                    iAddr -= self.nBytesNodeAddress
                    #break

    def _calcNodesAddress3 (self):
        nBytesNode = self.nBytesArc + self.nBytesNodeAddress
        # theorical nodes size if only addresses and no offset
        self.oRoot.size = len(self.oRoot.arcs) * nBytesNode
        for oNode in self.lSortedNodes:
            oNode.size = max(len(oNode.arcs), 1) * nBytesNode
        # rewind and calculate dropdown from the end, several times
        nDiff = self.nBytesNodeAddress - self.nBytesOffset
        bEnd = False
        while not bEnd:
            bEnd = True
            # recalculate addresses
            iAddr = self.oRoot.size
            for oNode in self.lSortedNodes:
                oNode.addr = iAddr
                iAddr += oNode.size
            # rewind and calculate dropdown from the end, several times
            for i in range(self.nNode-1, -1, -1):
                nSize = max(len(self.lSortedNodes[i].arcs), 1) * nBytesNode
                for oNextNode in self.lSortedNodes[i].arcs.values():
                    if 1 < (oNextNode.addr - self.lSortedNodes[i].addr) < self.nMaxOffset:
                        nSize -= nDiff
                if self.lSortedNodes[i].size != nSize:
                    self.lSortedNodes[i].size = nSize
                    bEnd = False

    def getBinaryAsJSON (self, nCompressionMethod=1, bBinaryDictAsHexString=True):
        "return a JSON string containing all necessary data of the dictionary (compressed as a binary string)"
        self._calculateBinary(nCompressionMethod)
        byDic = b""
        if nCompressionMethod == 1:
            byDic = self.oRoot.convToBytes1(self.nBytesArc, self.nBytesNodeAddress)
            for oNode in self.lMinimizedNodes:
                byDic += oNode.convToBytes1(self.nBytesArc, self.nBytesNodeAddress)
        elif nCompressionMethod == 2:
            byDic = self.oRoot.convToBytes2(self.nBytesArc, self.nBytesNodeAddress)
            for oNode in self.lSortedNodes:
                byDic += oNode.convToBytes2(self.nBytesArc, self.nBytesNodeAddress)
        elif nCompressionMethod == 3:
            byDic = self.oRoot.convToBytes3(self.nBytesArc, self.nBytesNodeAddress, self.nBytesOffset)
            for oNode in self.lSortedNodes:
                byDic += oNode.convToBytes3(self.nBytesArc, self.nBytesNodeAddress, self.nBytesOffset)
        return {
            "sHeader": "/grammalecte-fsa/",
            "sLangCode": self.sLangCode,
            "sLangName": self.sLangName,
            "sDicName": self.sDicName,
            "sFileName": self.sFileName,
            "sDate": self._getDate(),
            "nEntry": self.nEntry,
            "nChar": self.nChar,
            "nAff": self.nAff,
            "nTag": self.nTag,
            "cStemming": self.cStemming,
            "dChar": self.dChar,
            "nNode": self.nNode,
            "nArc": self.nArc,
            "nArcVal": self.nArcVal,
            "lArcVal": self.lArcVal,
            "nCompressionMethod": nCompressionMethod,
            "nBytesArc": self.nBytesArc,
            "nBytesNodeAddress": self.nBytesNodeAddress,
            "nBytesOffset": self.nBytesOffset,
            # Mozilla’s JS parser don’t like file bigger than 4 Mb!
            # So, if necessary, we use an hexadecimal string, that we will convert later in Firefox’s extension.
            # https://github.com/mozilla/addons-linter/issues/1361
            "sByDic": byDic.hex()  if bBinaryDictAsHexString  else [ e  for e in byDic ]
        }

    def writeAsJSObject (self, spfDst, nCompressionMethod, bInJSModule=False, bBinaryDictAsHexString=True):
        "write a file (JSON or JS module) with all the necessary data"
        if not spfDst.endswith(".json"):
            spfDst += "."+str(nCompressionMethod)+".json"
        with open(spfDst, "w", encoding="utf-8", newline="\n") as hDst:
            if bInJSModule:
                hDst.write('// JavaScript\n// Generated data (do not edit)\n\n"use strict";\n\nconst dictionary = ')
            hDst.write( json.dumps(self.getBinaryAsJSON(nCompressionMethod, bBinaryDictAsHexString), ensure_ascii=False) )
            if bInJSModule:
                hDst.write(";\n\nexports.dictionary = dictionary;\n")

    def writeBinary (self, sPathFile, nCompressionMethod, bDebug=False):
        """
        Save as a binary file.

        Format of the binary indexable dictionary:
        Each section is separated with 4 bytes of \0

        - Section Header:
            /grammalecte-fsa/[compression method]
                * compression method is an ASCII string

        - Section Informations:
            /[lang code]
            /[lang name]
            /[dictionary name]
            /[date creation]
            /[number of chars]
            /[number of bytes for each arc]
            /[number of bytes for each address node]
            /[number of entries]
            /[number of nodes]
            /[number of arcs]
            /[number of affixes]
                * each field is a ASCII string
            /[stemming code]
                * "S" means stems are generated by /suffix_code/,
                  "A" means they are generated by /affix_code/
                  See defineSuffixCode() and defineAffixCode() for details.
                  "N" means no stemming

        - Section Values:
                * a list of strings encoded in binary from utf-8, each value separated with a tabulation

        - Section Word Graph (nodes / arcs)
                * A list of nodes which are a list of arcs with an address of the next node.
                  See DawgNode.convToBytes() for details.
        """
        self._calculateBinary(nCompressionMethod)
        if not sPathFile.endswith(".bdic"):
            sPathFile += "."+str(nCompressionMethod)+".bdic"
        with open(sPathFile, 'wb') as hDst:
            # header
            hDst.write("/grammalecte-fsa/{}/".format(nCompressionMethod).encode("utf-8"))
            hDst.write(b"\0\0\0\0")
            # infos
            sInfo = "{}//{}//{}//{}//{}//{}//{}//{}//{}//{}//{}//{}//".format(self.sLangCode, self.sLangName, self.sDicName, self._getDate(), \
                                                                              self.nChar, self.nBytesArc, self.nBytesNodeAddress, \
                                                                              self.nEntry, self.nNode, self.nArc, self.nAff, self.cStemming)
            hDst.write(sInfo.encode("utf-8"))
            hDst.write(b"\0\0\0\0")
            # lArcVal
            hDst.write("\t".join(self.lArcVal).encode("utf-8"))
            hDst.write(b"\0\0\0\0")
            # DAWG: nodes / arcs
            if nCompressionMethod == 1:
                hDst.write(self.oRoot.convToBytes1(self.nBytesArc, self.nBytesNodeAddress))
                for oNode in self.lMinimizedNodes:
                    hDst.write(oNode.convToBytes1(self.nBytesArc, self.nBytesNodeAddress))
            elif nCompressionMethod == 2:
                hDst.write(self.oRoot.convToBytes2(self.nBytesArc, self.nBytesNodeAddress))
                for oNode in self.lSortedNodes:
                    hDst.write(oNode.convToBytes2(self.nBytesArc, self.nBytesNodeAddress))
            elif nCompressionMethod == 3:
                hDst.write(self.oRoot.convToBytes3(self.nBytesArc, self.nBytesNodeAddress, self.nBytesOffset))
                for oNode in self.lSortedNodes:
                    hDst.write(oNode.convToBytes3(self.nBytesArc, self.nBytesNodeAddress, self.nBytesOffset))
        if bDebug:
            self._writeNodes(sPathFile, nCompressionMethod)

    def _getDate (self):
        return time.strftime("%Y.%m.%d, %H:%M")

    def _writeNodes (self, sPathFile, nCompressionMethod):
        "for debugging only"
        print(" > Write nodes")
        with open(sPathFile+".nodes."+str(nCompressionMethod)+".txt", 'w', encoding='utf-8', newline="\n") as hDst:
            if nCompressionMethod == 1:
                hDst.write(self.oRoot.getTxtRepr1(self.nBytesArc, self.lArcVal)+"\n")
                #hDst.write( ''.join( [ "%02X " %  z  for z in self.oRoot.convToBytes1(self.nBytesArc, self.nBytesNodeAddress) ] ).strip() )
                for oNode in self.lMinimizedNodes:
                    hDst.write(oNode.getTxtRepr1(self.nBytesArc, self.lArcVal)+"\n")
            if nCompressionMethod == 2:
                hDst.write(self.oRoot.getTxtRepr2(self.nBytesArc, self.lArcVal)+"\n")
                for oNode in self.lSortedNodes:
                    hDst.write(oNode.getTxtRepr2(self.nBytesArc, self.lArcVal)+"\n")
            if nCompressionMethod == 3:
                hDst.write(self.oRoot.getTxtRepr3(self.nBytesArc, self.nBytesOffset, self.lArcVal)+"\n")
                #hDst.write( ''.join( [ "%02X " %  z  for z in self.oRoot.convToBytes3(self.nBytesArc, self.nBytesNodeAddress, self.nBytesOffset) ] ).strip() )
                for oNode in self.lSortedNodes:
                    hDst.write(oNode.getTxtRepr3(self.nBytesArc, self.nBytesOffset, self.lArcVal)+"\n")



class DawgNode:
    """Node of the word graph"""

    NextId = 0
    NextPos = 1 # (version 2)

    def __init__ (self):
        self.i = DawgNode.NextId
        DawgNode.NextId += 1
        self.final = False
        self.arcs = {}          # key: arc value; value: a node
        self.addr = 0           # address in the binary dictionary
        self.pos = 0            # position in the binary dictionary (version 2)
        self.size = 0           # size of node in bytes (version 3)

    @classmethod
    def resetNextId (cls):
        "set NextId to 0 "
        cls.NextId = 0

    def setPos (self): # version 2
        "define a position for node (version 2)"
        self.pos = DawgNode.NextPos
        DawgNode.NextPos += 1

    def __str__ (self):
        # Caution! this function is used for hashing and comparison!
        sFinalChar = "1"  if self.final  else "0"
        l = [sFinalChar]
        for (key, node) in self.arcs.items():
            l.append(str(key))
            l.append(str(node.i))
        return "_".join(l)

    def __hash__ (self):
        # Used as a key in a python dictionary.
        return self.__str__().__hash__()

    def __eq__ (self, other):
        # Used as a key in a python dictionary.
        # Nodes are equivalent if they have identical arcs, and each identical arc leads to identical states.
        return self.__str__() == other.__str__()

    def sortArcs (self, dValOccur):
        "sort arcs of node according to <dValOccur>"
        self.arcs = collections.OrderedDict(sorted(self.arcs.items(), key=lambda t: dValOccur.get(t[0], 0), reverse=True))

    def sortArcs2 (self, dValOccur, lArcVal):
        "sort arcs of each node depending on the previous char"
        self.arcs = collections.OrderedDict(sorted(self.arcs.items(), key=lambda t: dValOccur.get(lArcVal[t[0]], 0), reverse=True))

    # VERSION 1 =====================================================================================================
    def convToBytes1 (self, nBytesArc, nBytesNodeAddress):
        """
        Convert to bytes (method 1).

        Node scheme:
        - Arc length is defined by nBytesArc
        - Address length is defined by nBytesNodeAddress

        |                Arc                |                         Address of next node                          |
        |                                   |                                                                       |
         ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓
         ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃
         ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛
         [...]
         ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓
         ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃
         ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛
          ^ ^
          ┃ ┃
          ┃ ┃
          ┃ ┗━━━ if 1, last arc of this node
          ┗━━━━━ if 1, this node is final (only on the first arc)
        """
        nArc = len(self.arcs)
        nFinalNodeMask = 1 << ((nBytesArc*8)-1)
        nFinalArcMask = 1 << ((nBytesArc*8)-2)
        if len(self.arcs) == 0:
            val = nFinalNodeMask | nFinalArcMask
            by = val.to_bytes(nBytesArc, byteorder='big')
            by += (0).to_bytes(nBytesNodeAddress, byteorder='big')
            return by
        by = b""
        for i, arc in enumerate(self.arcs, 1):
            val = arc
            if i == 1 and self.final:
                val = val | nFinalNodeMask
            if i == nArc:
                val = val | nFinalArcMask
            by += val.to_bytes(nBytesArc, byteorder='big')
            by += self.arcs[arc].addr.to_bytes(nBytesNodeAddress, byteorder='big')
        return by

    def getTxtRepr1 (self, nBytesArc, lVal):
        "return representation as string of node (method 1)"
        nArc = len(self.arcs)
        nFinalNodeMask = 1 << ((nBytesArc*8)-1)
        nFinalArcMask = 1 << ((nBytesArc*8)-2)
        s = "i{:_>10} -- #{:_>10}\n".format(self.i, self.addr)
        if len(self.arcs) == 0:
            s += "  {:<20}  {:0>16}  i{:_>10}   #{:_>10}\n".format("", bin(nFinalNodeMask | nFinalArcMask)[2:], "0", "0")
            return s
        for i, arc in enumerate(self.arcs, 1):
            val = arc
            if i == 1 and self.final:
                val = val | nFinalNodeMask
            if i == nArc:
                val = val | nFinalArcMask
            s += "  {:<20}  {:0>16}  i{:_>10}   #{:_>10}\n".format(lVal[arc], bin(val)[2:], self.arcs[arc].i, self.arcs[arc].addr)
        return s

    # VERSION 2 =====================================================================================================
    def convToBytes2 (self, nBytesArc, nBytesNodeAddress):
        """
        Convert to bytes (method 2).

        Node scheme:
        - Arc length is defined by nBytesArc
        - Address length is defined by nBytesNodeAddress

        |                Arc                |                         Address of next node                          |
        |                                   |                                                                       |
         ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓
         ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃
         ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛
         [...]
         ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓
         ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃
         ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛
          ^ ^ ^
          ┃ ┃ ┃
          ┃ ┃ ┗━━ if 1, caution, no address: next node is the following node
          ┃ ┗━━━━ if 1, last arc of this node
          ┗━━━━━━ if 1, this node is final (only on the first arc)
        """
        nArc = len(self.arcs)
        nFinalNodeMask = 1 << ((nBytesArc*8)-1)
        nFinalArcMask = 1 << ((nBytesArc*8)-2)
        nNextNodeMask = 1 << ((nBytesArc*8)-3)
        if len(self.arcs) == 0:
            val = nFinalNodeMask | nFinalArcMask
            by = val.to_bytes(nBytesArc, byteorder='big')
            by += (0).to_bytes(nBytesNodeAddress, byteorder='big')
            return by
        by = b""
        for i, arc in enumerate(self.arcs, 1):
            val = arc
            if i == 1 and self.final:
                val = val | nFinalNodeMask
            if i == nArc:
                val = val | nFinalArcMask
            if (self.pos + 1) == self.arcs[arc].pos and self.i != 0:
                val = val | nNextNodeMask
                by += val.to_bytes(nBytesArc, byteorder='big')
            else:
                by += val.to_bytes(nBytesArc, byteorder='big')
                by += self.arcs[arc].addr.to_bytes(nBytesNodeAddress, byteorder='big')
        return by

    def getTxtRepr2 (self, nBytesArc, lVal):
        "return representation as string of node (method 2)"
        nArc = len(self.arcs)
        nFinalNodeMask = 1 << ((nBytesArc*8)-1)
        nFinalArcMask = 1 << ((nBytesArc*8)-2)
        nNextNodeMask = 1 << ((nBytesArc*8)-3)
        s = "i{:_>10} -- #{:_>10}\n".format(self.i, self.addr)
        if nArc == 0:
            s += "  {:<20}  {:0>16}  i{:_>10}   #{:_>10}\n".format("", bin(nFinalNodeMask | nFinalArcMask)[2:], "0", "0")
            return s
        for i, arc in enumerate(self.arcs, 1):
            val = arc
            if i == 1 and self.final:
                val = val | nFinalNodeMask
            if i == nArc:
                val = val | nFinalArcMask
            if (self.pos + 1) == self.arcs[arc].pos  and self.i != 0:
                val = val | nNextNodeMask
                s += "  {:<20}  {:0>16}\n".format(lVal[arc], bin(val)[2:])
            else:
                s += "  {:<20}  {:0>16}  i{:_>10}   #{:_>10}\n".format(lVal[arc], bin(val)[2:], self.arcs[arc].i, self.arcs[arc].addr)
        return s

    # VERSION 3 =====================================================================================================
    def convToBytes3 (self, nBytesArc, nBytesNodeAddress, nBytesOffset):
        """
        Convert to bytes (method 3).

        Node scheme:
        - Arc length is defined by nBytesArc
        - Address length is defined by nBytesNodeAddress
        - Offset length is defined by nBytesOffset

        |                Arc                |            Address of next node  or  offset to next node              |
        |                                   |                                                                       |
         ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓
         ┃1┃0┃0┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃
         ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛
         [...]
         ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓
         ┃0┃0┃1┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃     Offsets are shorter than addresses
         ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛
         ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━━━━┓
         ┃0┃1┃0┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃
         ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛ ┗━━━━━━━━━━━━━━━┛

          ^ ^ ^
          ┃ ┃ ┃
          ┃ ┃ ┗━━ if 1, offset instead of address of next node
          ┃ ┗━━━━ if 1, last arc of this node
          ┗━━━━━━ if 1, this node is final (only on the first arc)
        """
        nArc = len(self.arcs)
        nFinalNodeMask = 1 << ((nBytesArc*8)-1)
        nFinalArcMask = 1 << ((nBytesArc*8)-2)
        nNextNodeMask = 1 << ((nBytesArc*8)-3)
        nMaxOffset = (2 ** (nBytesOffset * 8)) - 1
        if nArc == 0:
            val = nFinalNodeMask | nFinalArcMask
            by = val.to_bytes(nBytesArc, byteorder='big')
            by += (0).to_bytes(nBytesNodeAddress, byteorder='big')
            return by
        by = b""
        for i, arc in enumerate(self.arcs, 1):
            val = arc
            if i == 1 and self.final:
                val = val | nFinalNodeMask
            if i == nArc:
                val = val | nFinalArcMask
            if 1 < (self.arcs[arc].addr - self.addr) < nMaxOffset and self.i != 0:
                val = val | nNextNodeMask
                by += val.to_bytes(nBytesArc, byteorder='big')
                by += (self.arcs[arc].addr-self.addr).to_bytes(nBytesOffset, byteorder='big')
            else:
                by += val.to_bytes(nBytesArc, byteorder='big')
                by += self.arcs[arc].addr.to_bytes(nBytesNodeAddress, byteorder='big')
        return by

    def getTxtRepr3 (self, nBytesArc, nBytesOffset, lVal):
        "return representation as string of node (method 3)"
        nArc = len(self.arcs)
        nFinalNodeMask = 1 << ((nBytesArc*8)-1)
        nFinalArcMask = 1 << ((nBytesArc*8)-2)
        nNextNodeMask = 1 << ((nBytesArc*8)-3)
        nMaxOffset = (2 ** (nBytesOffset * 8)) - 1
        s = "i{:_>10} -- #{:_>10}  ({})\n".format(self.i, self.addr, self.size)
        if nArc == 0:
            s += "  {:<20}  {:0>16}  i{:_>10}   #{:_>10}\n".format("", bin(nFinalNodeMask | nFinalArcMask)[2:], "0", "0")
            return s
        for i, arc in enumerate(self.arcs, 1):
            val = arc
            if i == 1 and self.final:
                val = val | nFinalNodeMask
            if i == nArc:
                val = val | nFinalArcMask
            if 1 < (self.arcs[arc].addr - self.addr) < nMaxOffset and self.i != 0:
                val = val | nNextNodeMask
                s += "  {:<20}  {:0>16}  i{:_>10}   +{:_>10}\n".format(lVal[arc], bin(val)[2:], self.arcs[arc].i, self.arcs[arc].addr - self.addr)
            else:
                s += "  {:<20}  {:0>16}  i{:_>10}   #{:_>10}\n".format(lVal[arc], bin(val)[2:], self.arcs[arc].i, self.arcs[arc].addr)
        return s



# Another attempt to sort node arcs

_dCharOrder = {
    # key: previous char, value: dictionary of chars {c: nValue}
    "": {}
}


def addWordToCharDict (sWord):
    "for each character of <sWord>, count how many times it appears after the previous character, and store result in a <_dCharOrder>"
    cPrevious = ""
    for cChar in sWord:
        if cPrevious not in _dCharOrder:
            _dCharOrder[cPrevious] = {}
        _dCharOrder[cPrevious][cChar] = _dCharOrder[cPrevious].get(cChar, 0) + 1
        cPrevious = cChar


def getCharOrderAfterChar (cChar):
    "return a dictionary of chars with number of times it appears after character <cChar>"
    return _dCharOrder.get(cChar, None)


def displayCharOrder ():
    "display how many times each character appear after another one"
    for key, value in _dCharOrder.items():
        print("[" + key + "]: ", ", ".join([ c+":"+str(n)  for c, n  in  sorted(value.items(), key=lambda t: t[1], reverse=True) ]))
