import os
from base64 import b64decode
from socket import socketpair

import varlink


class QMAuthError(Exception):
    def __init__(self, rc):
        super().__init__(rc)
        self.rc = rc


class QMailAuthuser:
    def __init__(
        self, username, password, prog, mailbox_path, virtual_user, authenticator
    ):
        self._username = username
        self._password = password
        self._prog = prog
        self._mailbox_path = mailbox_path
        self._virtual_user = virtual_user
        self._authenticator = authenticator

        self._pid = None
        self._socket = None
        self._client = None
        self._connection = None

    def read_headers_for(self, folder, start, end, sort):
        sort_val = dict()
        if sort[0] == "!":
            sort = sort[1:]
            sort_val["direction"] = "desc"
        else:
            sort_val["direction"] = "asc"

        match sort:
            case "date" | "subject" | "size":
                sort_val["parameter"] = sort
            case _:
                raise ValueError(f"invalid sort parameter {sort!r}")

        req = self._connection.List(folder=folder, start=start, end=end, sort=sort_val)
        return [
            {
                "message_handle": lmh["mid"],
                "byte_size": lmh["byte_size"],
                "unread": lmh["unread"],
                "date_received": lmh["rec_date"],
                "head": self._mail_header(lmh["header"]),
            }
            for lmh in req["mail_heads"]
        ]

    def count(self, folder):
        resp = self._connection.Stats(folder=folder)
        return {
            "byte_size": resp["byte_size"],
            "total_mails": resp["mail_count"],
            "unread_mails": resp["unread_count"],
        }

    def show(self, folder, msgid):
        resp = self._connection.Show(folder=folder, mid=msgid)
        return {
            "head": self._mail_header(resp["mail"]["head"]),
            "body": self._mail_body(resp["mail"]["body"]),
        }

    def raw(self, folder, mid, path):
        resp = self._connection.Raw(folder=folder, mid=mid, path=path)
        return {
            "head": self._mime_header(resp["header"]),
            "body": b64decode(resp["body"]),
        }

    def search(self, pattern, folder):
        resp = self._connection.Search(folder=folder, pattern=pattern)
        return resp

    def folders(self):
        resp = self._connection.Folders()
        return list(resp["folders"]) + [""]

    def move(self, mid, from_f, to_f):
        self._connection.Move(mid=mid, from_folder=from_f, to_folder=to_f)
        return True

    def remove(self, folder, msgid):
        self._connection.Remove(folder=folder, mid=msgid)
        return True

    def add_folder(self, name):
        resp = self._connection.AddFolder(name=name)
        return resp["status"]

    @staticmethod
    def _address(addr):
        if not addr:
            return None
        a = {"address": addr["address"]}
        if addr.get("name"):
            a["display_name"] = addr["name"]
        return a

    def _mail_header(self, mail_head):
        h = mail_head
        return {
            "date": h["send_date"],
            "sender": self._address(h.get("sender")),
            "cc": [self._address(x) for x in h["cc"] if x],
            "bcc": [self._address(x) for x in h["bcc"] if x],
            "from": [self._address(x) for x in h["written_from"] if x],
            "reply_to": [self._address(x) for x in h["reply_to"] if x],
            "to": [self._address(x) for x in h["send_to"] if x],
            "subject": h["subject"],
            "comments": list(h["comments"]),
            "keywords": list(h["keywords"]),
            "mime": self._mime_header(h["mime"]),
        }

    @staticmethod
    def _mime_header(mime_head):
        mh = {
            "content_maintype": mime_head["mime_type"]["main_type"],
            "content_subtype": mime_head["mime_type"]["sub_type"],
        }
        match mime_head["content_dispo"]:
            case "inline":
                mh["content_disposition"] = "inline"
            case "attachment":
                mh["content_disposition"] = "attachment"
            case "none":
                mh["content_disposition"] = None
            case invalid:
                raise ValueError(f"invalid content disposition {invalid!r}")

        if "file_name" in mime_head:
            mh["filename"] = mime_head["file_name"]

        return mh

    def _mail_body(self, body):
        assert len(body) == 1

        if "discrete" in body:
            return body["discrete"]
        elif "multipart" in body:
            res = {"parts": []}
            for mp in body["multipart"]["parts"]:
                r = {"head": self._mime_header(mp["mime_header"])}

                if mp["mime_header"]["content_dispo"] != "attachment":
                    r["body"] = self._mail_body(mp["body"])

                res["parts"].append(r)
            if pr := body["multipart"].get("preamble"):
                res["preamble"] = pr
            if ep := body["multipart"].get("epilogue"):
                res["epilogue"] = ep
            return res
        elif "mail" in body:
            return {
                "head": self._mail_header(body["mail"]["head"]),
                "body": self._mail_body(body["mail"]["body"]),
            }
        else:
            assert False

    def open(self):
        (rp, wp) = os.pipe()
        (sp, sc) = socketpair()
        cmdline = [self._authenticator, self._prog]
        if (pid := os.fork()) == 0:
            # child
            os.close(wp)
            sp.close()
            os.dup2(rp, 3)
            os.dup2(sc.fileno(), 4)
            os.environ["LISTEN_FDS"] = "2"
            os.environ["LISTEN_FDNAMES"] = "auth:varlink"
            os.environ["LISTEN_PID"] = str(os.getpid())
            os.execvp(self._authenticator, cmdline)
            assert False
        sc.close()
        os.close(rp)
        os.write(wp, f"{self._username}\0{self._password}\0\0".encode())
        os.close(wp)

        self._pid = pid
        self._socket = sp
        self._client = varlink.Client()

        try:
            self._connection = self._client.open(
                "de.jmhoffmann.jwebmail.mail-storage", connection=sp
            )
        except ConnectionResetError:
            (pid, status) = os.waitpid(pid, os.WNOHANG)
            if pid != 0:
                raise QMAuthError(os.waitstatus_to_exitcode(status))
            else:
                raise

        user = self._username[: self._username.index("@")]
        self._connection.Init(
            unix_user=self._virtual_user,
            mailbox_path=os.path.join(self._mailbox_path, user),
        )
        return self

    def close(self):
        self._connection.close()
        self._socket.close()
        (pid, status) = os.waitpid(self._pid, 0)
        assert pid == self._pid
        rc = os.waitstatus_to_exitcode(status)
        if rc != 0:
            raise QMAuthError(rc)