"""Export to PDF via latex"""

# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.

import subprocess
import os
import sys

from ipython_genutils.py3compat import which, cast_bytes_py2, getcwd
from traitlets import Integer, List, Bool, Instance, Unicode
from testpath.tempdir import TemporaryWorkingDirectory
from .latex import LatexExporter

class LatexFailed(IOError):
    """Exception for failed latex run
    
    Captured latex output is in error.output.
    """
    def __init__(self, output):
        self.output = output
    
    def __unicode__(self):
        return u"PDF creating failed, captured latex output:\n%s" % self.output
    
    def __str__(self):
        u = self.__unicode__()
        return cast_bytes_py2(u)

def prepend_to_env_search_path(varname, value, envdict):
    """Add value to the environment variable varname in envdict

    e.g. prepend_to_env_search_path('BIBINPUTS', '/home/sally/foo', os.environ)
    """
    if not value:
        return  # Nothing to add

    envdict[varname] = cast_bytes_py2(value) + os.pathsep + envdict.get(varname, '')

class PDFExporter(LatexExporter):
    """Writer designed to write to PDF files.

    This inherits from :class:`LatexExporter`. It creates a LaTeX file in
    a temporary directory using the template machinery, and then runs LaTeX
    to create a pdf.
    """
    export_from_notebook="pdf"

    latex_count = Integer(3,
        help="How many times latex will be called."
    ).tag(config=True)

    latex_command = List([u"xelatex", u"{filename}"],
        help="Shell command used to compile latex."
    ).tag(config=True)

    bib_command = List([u"bibtex", u"{filename}"],
        help="Shell command used to run bibtex."
    ).tag(config=True)

    verbose = Bool(False,
        help="Whether to display the output of latex commands."
    ).tag(config=True)

    texinputs = Unicode(help="texinputs dir. A notebook's directory is added")
    writer = Instance("nbconvert.writers.FilesWriter", args=(), kw={'build_directory': '.'})
    
    _captured_output = List()

    def run_command(self, command_list, filename, count, log_function):
        """Run command_list count times.
        
        Parameters
        ----------
        command_list : list
            A list of args to provide to Popen. Each element of this
            list will be interpolated with the filename to convert.
        filename : unicode
            The name of the file to convert.
        count : int
            How many times to run the command.
        
        Returns
        -------
        success : bool
            A boolean indicating if the command was successful (True)
            or failed (False).
        """
        command = [c.format(filename=filename) for c in command_list]

        # On windows with python 2.x there is a bug in subprocess.Popen and
        # unicode commands are not supported
        if sys.platform == 'win32' and sys.version_info < (3,0):
            #We must use cp1252 encoding for calling subprocess.Popen
            #Note that sys.stdin.encoding and encoding.DEFAULT_ENCODING
            # could be different (cp437 in case of dos console)
            command = [c.encode('cp1252') for c in command]

        # This will throw a clearer error if the command is not found
        cmd = which(command_list[0])
        if cmd is None:
            link = "https://nbconvert.readthedocs.io/en/latest/install.html#installing-tex"
            raise OSError("{formatter} not found on PATH, if you have not installed "
                          "{formatter} you may need to do so. Find further instructions "
                          "at {link}.".format(formatter=command_list[0], link=link))
        
        times = 'time' if count == 1 else 'times'
        self.log.info("Running %s %i %s: %s", command_list[0], count, times, command)
        
        shell = (sys.platform == 'win32')
        if shell:
            command = subprocess.list2cmdline(command)
        env = os.environ.copy()
        prepend_to_env_search_path('TEXINPUTS', self.texinputs, env)
        prepend_to_env_search_path('BIBINPUTS', self.texinputs, env)
        prepend_to_env_search_path('BSTINPUTS', self.texinputs, env)

        with open(os.devnull, 'rb') as null:
            stdout = subprocess.PIPE if not self.verbose else None
            for index in range(count):
                p = subprocess.Popen(command, stdout=stdout, stderr=subprocess.STDOUT,
                        stdin=null, shell=shell, env=env)
                out, _ = p.communicate()
                if p.returncode:
                    if self.verbose:
                        # verbose means I didn't capture stdout with PIPE,
                        # so it's already been displayed and `out` is None.
                        out = u''
                    else:
                        out = out.decode('utf-8', 'replace')
                    log_function(command, out)
                    self._captured_output.append(out)
                    return False # failure
        return True # success

    def run_latex(self, filename):
        """Run xelatex self.latex_count times."""

        def log_error(command, out):
            self.log.critical(u"%s failed: %s\n%s", command[0], command, out)

        return self.run_command(self.latex_command, filename,
            self.latex_count, log_error)

    def run_bib(self, filename):
        """Run bibtex self.latex_count times."""
        filename = os.path.splitext(filename)[0]

        def log_error(command, out):
            self.log.warning('%s had problems, most likely because there were no citations',
                command[0])
            self.log.debug(u"%s output: %s\n%s", command[0], command, out)

        return self.run_command(self.bib_command, filename, 1, log_error)
    
    def from_notebook_node(self, nb, resources=None, **kw):
        latex, resources = super(PDFExporter, self).from_notebook_node(
            nb, resources=resources, **kw
        )
        # set texinputs directory, so that local files will be found
        if resources and resources.get('metadata', {}).get('path'):
            self.texinputs = resources['metadata']['path']
        else:
            self.texinputs = getcwd()
        
        self._captured_outputs = []
        with TemporaryWorkingDirectory():
            notebook_name = 'notebook'
            tex_file = self.writer.write(latex, resources, notebook_name=notebook_name)
            self.log.info("Building PDF")
            rc = self.run_latex(tex_file)
            if rc:
                rc = self.run_bib(tex_file)
            if rc:
                rc = self.run_latex(tex_file)
            
            pdf_file = notebook_name + '.pdf'
            if not os.path.isfile(pdf_file):
                raise LatexFailed('\n'.join(self._captured_output))
            self.log.info('PDF successfully created')
            with open(pdf_file, 'rb') as f:
                pdf_data = f.read()
        
        # convert output extension to pdf
        # the writer above required it to be tex
        resources['output_extension'] = '.pdf'
        # clear figure outputs, extracted by latex export,
        # so we don't claim to be a multi-file export.
        resources.pop('outputs', None)
        
        return pdf_data, resources
    
