"""
ScriptNameFix WSGI middleware.

When nginx strips the path prefix before forwarding to a Flask app it also
sets the X-Script-Name header (e.g. /digiserver).  This middleware reads
that header and sets SCRIPT_NAME in the WSGI environ so that Flask's
url_for() generates absolute URLs with the correct prefix.

Usage in the app factory:
    from app.utils.script_name_fix import ScriptNameFix
    app.wsgi_app = ScriptNameFix(app.wsgi_app)
"""


class ScriptNameFix:
    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        script_name = environ.get('HTTP_X_SCRIPT_NAME', '').rstrip('/')
        if script_name:
            environ['SCRIPT_NAME'] = script_name
            path_info = environ.get('PATH_INFO', '/')
            if path_info.startswith(script_name):
                environ['PATH_INFO'] = path_info[len(script_name):] or '/'
        return self.app(environ, start_response)