from os import fdopen, remove
from subprocess import Popen, PIPE, CalledProcessError
from tempfile import mkstemp

from django.conf import settings
from django.http import HttpResponse
from django.template import loader
from django.utils.encoding import smart_str

WKHTMLTOPDF_CMD = getattr(settings, 'WKHTMLTOPDF_CMD', 'wkhtmltopdf')

def wkhtmltopdf(pages, output=None, **kwargs):
    """
    Converts html to PDF using http://code.google.com/p/wkhtmltopdf/.

    pages: List of file paths or URLs of the html to be converted.
    output: Optionsal output file path.
    **kwargs: Passed to wkhtmltopdf via _extra_args() (See
              https://github.com/antialize/wkhtmltopdf/blob/master/README_WKHTMLTOPDF
              for acceptable args.)
              Kwargs is passed through as arguments. e.g.:
                  {'footer_html': 'http://example.com/foot.html'}
              becomes
                  '--footer-html http://example.com/foot.html'
              Where there is no value passed, use a blank string. e.g.:
                  {'disable_javascript': ''}
              becomes:
                  '--disable-javascript '

    example usage:
        wkhtmltopdf(html_path="~/example.html",
                    dpi=300,
                    orientation="Landscape",
                    disable_javascript="")
    """

    def _extra_args(**kwargs):
        """Converts kwargs into a string of flags to be passed to wkhtmltopdf."""
        flags = ''
        for k, v in kwargs.items():
            flags += ' --%s %s' % (k.replace('_', '-'), v)
        return flags

    if not isinstance(pages, list):
        pages = [pages]

    kwargs['quiet'] = ''
    args = '%s %s %s %s' % (WKHTMLTOPDF_CMD, _extra_args(**kwargs), ' '.join(pages), output or '-')

    process = Popen(args, stdout=PIPE, shell=True)
    stdoutdata, stderrdata = process.communicate()

    if process.returncode != 0:
        raise CalledProcessError(process.returncode, args)
    
    if output is None:
        output = stdoutdata

    return output

def render_to_pdf(template_name, dictionary=None, context_instance=None, header_template=None, footer_template=None, **kwargs):
    """Renders a html template as a PDF response."""

    filename = kwargs.pop('filename', None)

    page_path = template_to_temp_file(template_name, dictionary, context_instance)

    tmp_files = []
    if header_template is not None:
        kwargs['header_html'] = template_to_temp_file(header_template, dictionary, context_instance)
        tmp_files.append(kwargs['header_html'])
    if footer_template is not None:
        kwargs['footer_html'] = template_to_temp_file(footer_template, dictionary, context_instance)
        tmp_files.append(kwargs['footer_html'])

    content = wkhtmltopdf([page_path], **kwargs)

    for path in tmp_files:
        remove(path)

    response = HttpResponse(content, mimetype='application/pdf')
    if filename is not None:
        response['Content-Disposition'] = 'attachment;' + ' filename=%s' %filename
    return response


def template_to_temp_file(*args, **kwargs):
    """
    Renders a template to a temp file, and returns the path of the file.
    """
    file_descriptor, tempfile_path = mkstemp(suffix='.html')
    with fdopen(file_descriptor, 'wt') as f:
        f.write(smart_str(loader.render_to_string(*args, **kwargs)))
    return tempfile_path