# Like many things, this started life as part of Paste

# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php

"""
Error handler middleware

When an exception is thrown from the wrapper application, this logs
the exception and displays an error page.
"""

import logging
import sys
import traceback
from io import StringIO
from typing import cast

import markupsafe
from paste import (
    request,
    wsgilib,
)
from paste.exceptions import (
    collector,
    formatter,
    reporter,
)

log = logging.getLogger(__name__)

__all__ = ("ErrorMiddleware", "handle_exception")


class _NoDefault:
    def __repr__(self):
        return "<NoDefault>"


NoDefault = _NoDefault()


class ErrorMiddleware:
    """
    Error handling middleware

    Usage::

        error_catching_wsgi_app = ErrorMiddleware(wsgi_app)

    Settings:

      ``debug``:
          If true, then tracebacks will be shown in the browser.

      ``error_email``:
          an email address (or list of addresses) to send exception
          reports to

      ``error_log``:
          a filename to append tracebacks to

      ``show_exceptions_in_wsgi_errors``:
          If true, then errors will be printed to ``wsgi.errors``
          (frequently a server error log, or stderr).

      ``from_address``, ``smtp_server``, ``error_subject_prefix``, ``smtp_username``, ``smtp_password``, ``smtp_use_tls``:
          variables to control the emailed exception reports

      ``error_message``:
          When debug mode is off, the error message to show to users.

      ``xmlhttp_key``:
          When this key (default ``_``) is in the request GET variables
          (not POST!), expect that this is an XMLHttpRequest, and the
          response should be more minimal; it should not be a complete
          HTML page.

    Environment Configuration:

      ``paste.throw_errors``:
          If this setting in the request environment is true, then this
          middleware is disabled. This can be useful in a testing situation
          where you don't want errors to be caught and transformed.

      ``paste.expected_exceptions``:
          When this middleware encounters an exception listed in this
          environment variable and when the ``start_response`` has not
          yet occurred, the exception will be re-raised instead of being
          caught.  This should generally be set by middleware that may
          (but probably shouldn't be) installed above this middleware,
          and wants to get certain exceptions.  Exceptions raised after
          ``start_response`` have been called are always caught since
          by definition they are no longer expected.

    """

    def __init__(
        self,
        application,
        global_conf=None,
        debug=NoDefault,
        error_email=None,
        error_log=None,
        show_exceptions_in_wsgi_errors=NoDefault,
        from_address=None,
        smtp_server=None,
        smtp_username=None,
        smtp_password=None,
        smtp_use_tls=False,
        error_subject_prefix=None,
        error_message=None,
        xmlhttp_key=None,
    ):
        from paste.util import converters

        self.application = application
        # @@: global_conf should be handled elsewhere in a separate
        # function for the entry point
        if global_conf is None:
            global_conf = {}
        if debug is NoDefault:
            debug = converters.asbool(global_conf.get("debug"))
        if show_exceptions_in_wsgi_errors is NoDefault:
            show_exceptions_in_wsgi_errors = converters.asbool(global_conf.get("show_exceptions_in_wsgi_errors"))
        self.debug_mode = converters.asbool(debug)
        if error_email is None:
            error_email = (
                global_conf.get("error_email")
                or global_conf.get("admin_email")
                or global_conf.get("webmaster_email")
                or global_conf.get("sysadmin_email")
            )
        self.error_email = converters.aslist(error_email)
        self.error_log = error_log
        self.show_exceptions_in_wsgi_errors = show_exceptions_in_wsgi_errors
        if from_address is None:
            from_address = global_conf.get("error_from_address", "errors@localhost")
        self.from_address = from_address
        if smtp_server is None:
            smtp_server = global_conf.get("smtp_server", "localhost")
        self.smtp_server = smtp_server
        self.smtp_username = smtp_username or global_conf.get("smtp_username")
        self.smtp_password = smtp_password or global_conf.get("smtp_password")
        self.smtp_use_tls = smtp_use_tls or converters.asbool(global_conf.get("smtp_use_tls"))
        self.error_subject_prefix = error_subject_prefix or ""
        if error_message is None:
            error_message = global_conf.get("error_message")
        self.error_message = error_message
        if xmlhttp_key is None:
            xmlhttp_key = global_conf.get("xmlhttp_key", "_")
        self.xmlhttp_key = xmlhttp_key

    def __call__(self, environ, start_response):
        """
        The WSGI application interface.
        """
        # We want to be careful about not sending headers twice,
        # and the content type that the app has committed to (if there
        # is an exception in the iterator body of the response)
        if environ.get("paste.throw_errors"):
            return self.application(environ, start_response)
        environ["paste.throw_errors"] = True

        try:
            __traceback_supplement__ = Supplement, self, environ
            sr_checker = ResponseStartChecker(start_response)
            app_iter = self.application(environ, sr_checker)
            return self.make_catching_iter(app_iter, environ, sr_checker)
        except Exception:
            exc_info = sys.exc_info()
            try:
                for expect in environ.get("paste.expected_exceptions", []):
                    if isinstance(exc_info[1], expect):
                        raise
                log.exception("Uncaught Exception")
                start_response("500 Internal Server Error", [("content-type", "text/html")], exc_info)
                # @@: it would be nice to deal with bad content types here
                response = self.exception_handler(exc_info, environ)
                return [response.encode(errors="ignore")]
            finally:
                # clean up locals...
                exc_info = None

    def make_catching_iter(self, app_iter, environ, sr_checker):
        if isinstance(app_iter, (list, tuple)):
            # These don't raise
            return app_iter
        return CatchingIter(app_iter, environ, sr_checker, self)

    def exception_handler(self, exc_info, environ) -> str:
        simple_html_error = False
        if self.xmlhttp_key:
            get_vars = wsgilib.parse_querystring(environ)
            if dict(get_vars).get(self.xmlhttp_key):
                simple_html_error = True
        return handle_exception(
            exc_info,
            environ["wsgi.errors"],
            debug_mode=self.debug_mode,
            error_email=self.error_email,
            error_log=self.error_log,
            show_exceptions_in_wsgi_errors=self.show_exceptions_in_wsgi_errors,
            error_email_from=self.from_address,
            smtp_server=self.smtp_server,
            smtp_username=self.smtp_username,
            smtp_password=self.smtp_password,
            smtp_use_tls=self.smtp_use_tls,
            error_subject_prefix=self.error_subject_prefix,
            error_message=self.error_message,
            simple_html_error=simple_html_error,
            environ=environ,
        )


class ResponseStartChecker:
    def __init__(self, start_response):
        self.start_response = start_response
        self.response_started = False

    def __call__(self, *args):
        self.response_started = True
        # Return whatever the wrapped start_response would have
        # returned
        return self.start_response(*args)


class CatchingIter:
    """
    A wrapper around the application iterator that will catch
    exceptions raised by the a generator, or by the close method, and
    display or report as necessary.
    """

    def __init__(self, app_iter, environ, start_checker, error_middleware):
        self.app_iterable = app_iter
        self.app_iterator = iter(app_iter)
        self.environ = environ
        self.start_checker = start_checker
        self.error_middleware = error_middleware
        self.closed = False

    def __iter__(self):
        return self

    def __next__(self):
        __traceback_supplement__ = (Supplement, self.error_middleware, self.environ)
        if self.closed:
            raise StopIteration
        try:
            return next(self.app_iterator)
        except StopIteration:
            self.closed = True
            close_response = self._close()
            if close_response is not None:
                return close_response
            else:
                raise StopIteration
        except Exception:
            self.closed = True
            close_response = self._close()
            exc_info = sys.exc_info()
            response = self.error_middleware.exception_handler(exc_info, self.environ)
            if close_response is not None:
                response += f"<hr noshade>Error in .close():<br>{close_response}"

            if not self.start_checker.response_started:
                self.start_checker("500 Internal Server Error", [("content-type", "text/html")], exc_info)

            return response.encode("utf-8", errors="ignore")

    def close(self):
        # This should at least print something to stderr if the
        # close method fails at this point
        if not self.closed:
            self._close()

    def _close(self):
        """Close and return any error message"""
        if not hasattr(self.app_iterable, "close"):
            return None
        try:
            self.app_iterable.close()
            return None
        except Exception:
            close_response = self.error_middleware.exception_handler(sys.exc_info(), self.environ)
            return close_response


class Supplement:
    """
    This is a supplement used to display standard WSGI information in
    the traceback.
    """

    def __init__(self, middleware, environ):
        self.middleware = middleware
        self.environ = environ
        self.source_url = request.construct_url(environ)

    def extraData(self):
        data = {}
        cgi_vars = data[("extra", "CGI Variables")] = {}
        wsgi_vars = data[("extra", "WSGI Variables")] = {}
        hide_vars = [
            "paste.config",
            "wsgi.errors",
            "wsgi.input",
            "wsgi.multithread",
            "wsgi.multiprocess",
            "wsgi.run_once",
            "wsgi.version",
            "wsgi.url_scheme",
        ]
        for name, value in self.environ.items():
            if name.upper() == name:
                if value:
                    cgi_vars[name] = value
            elif name not in hide_vars:
                wsgi_vars[name] = value
        if self.environ["wsgi.version"] != (1, 0):
            wsgi_vars["wsgi.version"] = self.environ["wsgi.version"]
        proc_desc = tuple(
            int(bool(self.environ[key])) for key in ("wsgi.multiprocess", "wsgi.multithread", "wsgi.run_once")
        )
        wsgi_vars["wsgi process"] = self.process_combos[proc_desc]
        wsgi_vars["application"] = self.middleware.application
        if "paste.config" in self.environ:
            data[("extra", "Configuration")] = dict(self.environ["paste.config"])
        return data

    process_combos = {
        # multiprocess, multithread, run_once
        (0, 0, 0): "Non-concurrent server",
        (0, 1, 0): "Multithreaded",
        (1, 0, 0): "Multiprocess",
        (1, 1, 0): "Multi process AND threads (?)",
        (0, 0, 1): "Non-concurrent CGI",
        (0, 1, 1): "Multithread CGI (?)",
        (1, 0, 1): "CGI",
        (1, 1, 1): "Multi thread/process CGI (?)",
    }


def handle_exception(
    exc_info,
    error_stream,
    debug_mode=False,
    error_email=None,
    error_log=None,
    show_exceptions_in_wsgi_errors=False,
    error_email_from="errors@localhost",
    smtp_server="localhost",
    smtp_username=None,
    smtp_password=None,
    smtp_use_tls=False,
    error_subject_prefix="",
    error_message=None,
    simple_html_error=False,
    environ=None,
) -> str:
    """
    For exception handling outside of a web context

    Use like::

        import sys
        from paste.exceptions.errormiddleware import handle_exception
        try:
            do stuff
        except Exception:
            handle_exception(
                sys.exc_info(), sys.stderr, html=False, ...other config...)

    If you want to report, but not fully catch the exception, call
    ``raise`` after ``handle_exception``, which (when given no argument)
    will reraise the exception.
    """
    reported = False
    exc_data = collector.collect_exception(*exc_info)
    extra_data = ""
    if error_email:
        rep = reporter.EmailReporter(
            to_addresses=error_email,
            from_address=error_email_from,
            smtp_server=smtp_server,
            smtp_username=smtp_username,
            smtp_password=smtp_password,
            smtp_use_tls=smtp_use_tls,
            subject_prefix=error_subject_prefix,
        )
        rep_err = send_report(rep, exc_data, html=True)
        if rep_err:
            extra_data += rep_err
        else:
            reported = True
    if error_log:
        rep = reporter.LogReporter(filename=error_log)
        rep_err = send_report(rep, exc_data, html=True)
        if rep_err:
            extra_data += rep_err
        else:
            reported = True
    if show_exceptions_in_wsgi_errors:
        rep = reporter.FileReporter(file=error_stream)
        rep_err = send_report(rep, exc_data, html=True)
        if rep_err:
            extra_data += rep_err
        else:
            reported = True
    else:
        error_stream.write(f"Error - {exc_data.exception_type}: {exc_data.exception_value}\n")
    if debug_mode and simple_html_error:
        return_error = formatter.format_html(
            exc_data, include_hidden_frames=False, include_reusable=False, show_extra_data=False
        )
        reported = True
    elif debug_mode and not simple_html_error:
        error_html = formatter.format_html(exc_data, include_hidden_frames=True, include_reusable=False)
        head_html = formatter.error_css + formatter.hide_display_js
        return_error = error_template(head_html, error_html, extra_data)
        extra_data = ""
        reported = True
    else:
        msg = error_message or """
        An error occurred.
        """
        extra = "<p><b>The error has been logged to our team.</b>"
        if "sentry_event_id" in environ:
            extra += " If you want to contact us about this error, please reference the following<br><br>"
            extra += f"<b><large>GURU MEDITATION: #{environ['sentry_event_id']}</large></b>"
        extra += "</p>"
        return_error = error_template("", msg, extra)
    if not reported and error_stream:
        err_report = formatter.format_text(exc_data, show_hidden_frames=True)
        err_report += f"\n{'-' * 60}\n"
        error_stream.write(err_report)
    if extra_data:
        error_stream.write(extra_data)
    return return_error


def send_report(rep, exc_data, html=True):
    try:
        rep.report(exc_data)
    except Exception:
        output = StringIO()
        traceback.print_exc(file=output)
        if html:
            return f"""
            <p>Additionally an error occurred while sending the {markupsafe.escape(str(rep))} report:

            <pre>{output.getvalue()}</pre>
            </p>"""
        else:
            return f"Additionally an error occurred while sending the {rep} report:\n{output.getvalue()}"
    else:
        return ""


def error_template(head_html, exception, extra):
    return f"""
    <!DOCTYPE HTML>
    <html>
    <head>
    <style type="text/css">
    body {{ color: #303030; background: #dfe5f9; font-family:"Lucida Grande",verdana,arial,helvetica,sans-serif; font-size:12px; line-height:16px; }}
    .content {{ max-width: 720px; margin: auto; margin-top: 50px; }}
    </style>
    <title>Internal Server Error</title>
    {head_html}
    </head>
    <body>
    <div class="content">
    <h1>Internal Server Error</h1>

    <h2>Galaxy was unable to successfully complete your request</h2>

    <p>{exception}</p>

    This may be an intermittent problem due to load or other unpredictable factors, reloading the page may address the problem.

    {extra}
    </div>
    </body>
    </html>"""


def make_error_middleware(app, global_conf, **kw):
    return ErrorMiddleware(app, global_conf=global_conf, **kw)


doc_lines = cast(str, ErrorMiddleware.__doc__).splitlines(True)
for i in range(len(doc_lines)):
    if doc_lines[i].strip().startswith("Settings"):
        make_error_middleware.__doc__ = "".join(doc_lines[i:])
        break
del i, doc_lines
