import os
import sys
from io import StringIO

from docutils import nodes
from docutils.parsers.rst import Directive, directives

__all__ = ['Generate']


class Generate(Directive):
    """
    Custom directive to include raw output generated using supplied Python code

    This directive is similar to the ``raw`` directive, except that the raw content is generated
    instead of statically provided.  As with the ``raw`` directive, the required argument specifies
    the format of the output (e.g., ``html`` or ``latex``).

    The optional flag ``html_border`` surrounds HTML output with a black border for visual
    separation.
    """
    required_arguments = 1
    optional_arguments = 0
    option_spec = {'html_border': directives.flag}
    has_content = True

    def run(self):
        # Respect the same disabling options as the ``raw`` directive
        if (not self.state.document.settings.raw_enabled
                or not self.state.document.settings.file_insertion_enabled):
            raise self.warning(f'"{self.name}" directive disabled.')

        attributes = {'format': ' '.join(self.arguments[0].lower().split())}

        source, lineno = self.state_machine.get_source_and_line(self.lineno)

        old_stdout, sys.stdout = sys.stdout, StringIO()
        try:
            # Execute the Python code and capture its output
            exec('\n'.join(self.content))
            text = sys.stdout.getvalue()

            # Wrap HTML output in a black border if requested
            if attributes['format'] == 'html' and 'html_border' in self.options:
                text = f"<div style='border:1px solid black; padding:3px'>{text}</div>"

            # Append the output in the same fashion as the ``raw`` directive
            raw_node = nodes.raw('', text, **attributes)
            raw_node.source, raw_node.line = source, lineno
            return [raw_node]
        except Exception as e:
            message = f"Unable to execute Python code at {os.path.basename(source)}:{lineno}"
            return [nodes.error(None, nodes.paragraph(text=message)),
                    nodes.paragraph(text=str(e))]
        finally:
            sys.stdout = old_stdout


def setup(app):
    app.add_directive('generate', Generate)

    return {'parallel_read_safe': True, 'parallel_write_safe': True}
