"""xpath utilities"""

#import copy
#import os
import sys

from lxml import etree

#xsimport docing
from nitpo import Nitpo

class Xpaths(Nitpo):

    def __init__(self, do_verbose=False):
        super().__init__()
        ns = self.const['ns']
        self.N = {'n': self.const['ns']}
        self.nsmap = {None: ns}
        self.do_verbose = do_verbose

    def run(self, doc, xp):
        try:
            outs = doc.xpath(xp, namespaces=self.const['nsmap'])
        except etree.XPathEvalError:
            note = f"xpaths can't evalute '{xp}'"
            if self.is_dev():
                raise Exception(note)
            print(note, file=sys.stderr)
            return None
        return outs

    def has_it(self, doc, xp):
        count = len(doc.xpath(xp, namespaces=self.const['nsmap']))
        if count == 0:
            return False
        return True

    def txt(self, doc):
        string = etree.tostring(doc, pretty_print=True).decode()
        return string

    def zero_or_one(self, doc, xp):
        outs = self.run(doc, xp)
        if outs is None:
            return []
        if outs is False:
            return []
        if outs is True:
            return []
        if len(outs) == 0:
            return []
        if len(outs) == 1:
            return outs[0]
        err = self.txt(doc) + ' must not have several ' + xp
        if self.is_dev():
            raise Exception(err)
        print(err, file=sys.stderr)
        return outs[0]

    def all(self, doc, xp):
        outs = self.run(doc, xp)
        return outs

    def none_or_one(self, doc, xp):
        outs = self.run(doc, xp)
        if len(outs) == 0:
            return None
        if len(outs) == 1:
            return outs[0]
        err = self.txt(doc) + ' must not have several ' + xp
        if self.is_dev():
            raise Exception(err)
        print(err, file=sys.stderr)
        return outs[0]

    def one_or_last(self, doc, xp):
        outs = self.run(doc, xp)
        if len(outs) == 0:
            err = self.txt(doc) + ' must have at least one ' + xp
            if self.is_dev():
                raise Exception(err)
            return None
        return outs[-1]

    def one_or_first(self, doc, xp):
        outs = self.run(doc, xp)
        if len(outs) == 0:
            err = self.txt(doc) + ' must have at least one ' + xp
            if self.is_dev():
                raise Exception(err)
            return None
        return outs[0]

    def one(self, doc, xp):
        outs = self.run(doc, xp)
        if len(outs) == 0:
            err = self.txt(doc) + ' must have ' + xp
            if self.is_dev():
                raise Exception(err)
            print(err, file=sys.stderr)
        if len(outs) == 1:
            return outs[0]
        err = self.txt(doc) + ' must not have several ' + xp
        if self.is_dev():
            raise Exception(err)
        print(err, file=sys.stderr)
        return outs[0]