"""
Internal Python-level IMAP handling used by the testplugin
and for cleaning up inbox/mvbox for each test function run.
"""

import io
import email
import ssl
import pathlib
from imapclient import IMAPClient
from imapclient.exceptions import IMAPClientError
import deltachat


SEEN = b'\\Seen'
DELETED = b'\\Deleted'
FLAGS = b'FLAGS'
FETCH = b'FETCH'
ALL = "1:*"


@deltachat.global_hookimpl
def dc_account_extra_configure(account):
    """ Reset the account (we reuse accounts across tests)
    and make 'account.direct_imap' available for direct IMAP ops.
    """
    imap = DirectImap(account, account.logid)
    if imap.select_config_folder("mvbox"):
        imap.delete(ALL, expunge=True)
    assert imap.select_config_folder("inbox")
    imap.delete(ALL, expunge=True)
    setattr(account, "direct_imap", imap)


@deltachat.global_hookimpl
def dc_account_after_shutdown(account):
    """ shutdown the imap connection if there is one. """
    imap = getattr(account, "direct_imap", None)
    if imap is not None:
        imap.shutdown()
        del account.direct_imap


class DirectImap:
    def __init__(self, account, logid):
        self.account = account
        self.logid = logid
        self._idling = False
        self.connect()

    def connect(self):
        ssl_context = ssl.create_default_context()

        # don't check if certificate hostname doesn't match target hostname
        ssl_context.check_hostname = False

        # don't check if the certificate is trusted by a certificate authority
        ssl_context.verify_mode = ssl.CERT_NONE

        host = self.account.get_config("configured_mail_server")
        user = self.account.get_config("addr")
        pw = self.account.get_config("mail_pw")
        self.conn = IMAPClient(host, ssl_context=ssl_context)
        self.conn.login(user, pw)

        self.select_folder("INBOX")

    def shutdown(self):
        try:
            self.conn.idle_done()
        except (OSError, IMAPClientError):
            pass
        try:
            self.conn.logout()
        except (OSError, IMAPClientError):
            print("Could not logout direct_imap conn")

    def select_folder(self, foldername):
        assert not self._idling
        return self.conn.select_folder(foldername)

    def select_config_folder(self, config_name):
        """ Return info about selected folder if it is
        configured, otherwise None. """
        if "_" not in config_name:
            config_name = "configured_{}_folder".format(config_name)
        foldername = self.account.get_config(config_name)
        if foldername:
            return self.select_folder(foldername)

    def list_folders(self):
        """ return list of all existing folder names"""
        assert not self._idling
        folders = []
        for meta, sep, foldername in self.conn.list_folders():
            folders.append(foldername)
        return folders

    def delete(self, range, expunge=True):
        """ delete a range of messages (imap-syntax).
        If expunge is true, perform the expunge-operation
        to make sure the messages are really gone and not
        just flagged as deleted.
        """
        self.conn.set_flags(range, [DELETED])
        if expunge:
            self.conn.expunge()

    def get_all_messages(self):
        assert not self._idling
        return self.conn.fetch(ALL, [FLAGS])

    def get_unread_messages(self):
        assert not self._idling
        res = self.conn.fetch(ALL, [FLAGS])
        return [uid for uid in res
                if SEEN not in res[uid][FLAGS]]

    def mark_all_read(self):
        messages = self.get_unread_messages()
        if messages:
            res = self.conn.set_flags(messages, [SEEN])
            print("marked seen:", messages, res)

    def get_unread_cnt(self):
        return len(self.get_unread_messages())

    def dump_account_info(self, logfile):
        def log(*args, **kwargs):
            kwargs["file"] = logfile
            print(*args, **kwargs)

        cursor = 0
        for name, val in self.account.get_info().items():
            entry = "{}={}".format(name.upper(), val)
            if cursor + len(entry) > 80:
                log("")
                cursor = 0
            log(entry, end=" ")
            cursor += len(entry) + 1
        log("")

    def dump_imap_structures(self, dir, logfile):
        assert not self._idling
        stream = io.StringIO()

        def log(*args, **kwargs):
            kwargs["file"] = stream
            print(*args, **kwargs)

        empty_folders = []
        for imapfolder in self.list_folders():
            self.select_folder(imapfolder)
            messages = list(self.get_all_messages())
            if not messages:
                empty_folders.append(imapfolder)
                continue

            log("---------", imapfolder, len(messages), "messages ---------")
            # get message content without auto-marking it as seen
            # fetching 'RFC822' would mark it as seen.
            requested = [b'BODY.PEEK[HEADER]', FLAGS]
            for uid, data in self.conn.fetch(messages, requested).items():
                body_bytes = data[b'BODY[HEADER]']
                flags = data[FLAGS]
                path = pathlib.Path(str(dir)).joinpath("IMAP", self.logid, imapfolder)
                path.mkdir(parents=True, exist_ok=True)
                fn = path.joinpath(str(uid))
                fn.write_bytes(body_bytes)
                log("Message", uid, fn)
                email_message = email.message_from_bytes(body_bytes)
                log("Message", uid, flags, "Message-Id:", email_message.get("Message-Id"))

        if empty_folders:
            log("--------- EMPTY FOLDERS:", empty_folders)

        print(stream.getvalue(), file=logfile)

    def idle_start(self):
        """ switch this connection to idle mode. non-blocking. """
        assert not self._idling
        res = self.conn.idle()
        self._idling = True
        return res

    def idle_check(self, terminate=False):
        """ (blocking) wait for next idle message from server. """
        assert self._idling
        self.account.log("imap-direct: calling idle_check")
        res = self.conn.idle_check()
        if terminate:
            self.idle_done()
        return res

    def idle_wait_for_seen(self):
        """ Return first message with SEEN flag
        from a running idle-stream REtiurn.
        """
        while 1:
            for item in self.idle_check():
                if item[1] == FETCH:
                    if item[2][0] == FLAGS:
                        if SEEN in item[2][1]:
                            return item[0]

    def idle_done(self):
        """ send idle-done to server if we are currently in idle mode. """
        if self._idling:
            res = self.conn.idle_done()
            self._idling = False
            return res