#!/usr/bin/env python3
import configparser
import getpass
import itertools
import email.message
import enum
import os
import smtplib
import sys
import textwrap

from datetime import datetime

import xml.etree.ElementTree as etree


DESCRIPTION = """\
Send email updates for XEP changes based on the difference between two \
xeplist files."""

EPILOG = """\
Configuration file contents:

[smtp]
host=<smtp server to send through>
port=587
user=<optional: user name to authenticate with>
password=<optional: password to authn. with>
from=<address to send from>

If user is omitted, anonymous mail sending is attempted.

If options are missing from the configuration file and the standard input and \
standard output are a terminal, the script interactively asks for the option \
values. If no terminal is connected, the script exits with an error instead."""


class Status(enum.Enum):
    PROTO = 'ProtoXEP'
    EXPERIMENTAL = 'Experimental'
    PROPOSED = 'Proposed'
    DRAFT = 'Draft'
    ACTIVE = 'Active'
    FINAL = 'Final'
    RETRACTED = 'Retracted'
    OBSOLETE = 'Obsolete'
    DEFERRED = 'Deferred'
    REJECTED = 'Rejected'
    DEPRECATED = 'Deprecated'

    @classmethod
    def fromstr(cls, s):
        if s == "Proto" or s.lower() == "protoxep":
            s = "ProtoXEP"
        return cls(s)


class Action(enum.Enum):
    PROTO = "Proposed XMPP Extension"
    NEW = "NEW"
    DRAFT = "DRAFT"
    ACTIVE = "ACTIVE"
    FINAL = "FINAL"
    RETRACT = "RETRACTED"
    OBSOLETE = "OBSOLETED"
    DEFER = "DEFERRED"
    UPDATE = "UPDATED"

    @classmethod
    def fromstatus(cls, status):
        return {
            Status.EXPERIMENTAL: cls.NEW,
            Status.DRAFT: cls.DRAFT,
            Status.ACTIVE: cls.ACTIVE,
            Status.FINAL: cls.FINAL,
            Status.RETRACTED: cls.RETRACT,
            Status.OBSOLETED: cls.OBSOLETE,
            Status.DEPRECATED: cls.DEPRECATE,
            Status.DEFERRED: cls.DEFERRED,
        }


XEP_URL_PREFIX = "https://xmpp.org/extensions/"


MAIL_PROTO_TEMPLATE = """\
The XMPP Extensions Editor has received a proposal for a new XEP.

Title: {info[title]}
Abstract:
{info[abstract]}

URL: {url}

The {approver} will decide in the next two weeks whether to accept this \
proposal as an official XEP."""


SUBJECT_PROTO_TEMPLATE = "Proposed XMPP Extension: {info[title]}"


MAIL_NONPROTO_TEMPLATE = """\
Version {info[last_revision][version]} of XEP-{info[number]:04d} \
({info[title]}) has been released.

Abstract:
{info[abstract]}

Changelog:
{changelog}

URL: {url}"""


SUBJECT_NONPROTO_TEMPLATE = \
    "{action.value}: XEP-{info[number]:04d} ({info[title]})"


def load_xepinfo(el):
    accepted = el.get("accepted").lower() == "true"

    info = {
        "title": el.find("title").text,
        "abstract": el.find("abstract").text,
        "type": el.find("type").text,
        "status": Status.fromstr(el.find("status").text),
        "approver": el.find("approver").text,
        "accepted": accepted,
    }

    last_revision_el = el.find("last-revision")
    if last_revision_el is not None:
        last_revision = {
            "version": last_revision_el.find("version").text,
            "date": last_revision_el.find("date").text,
            "initials": None,
            "remark": None,
        }

        initials_el = last_revision_el.find("initials")
        if initials_el is not None:
            last_revision["initials"] = initials_el.text

        remark_el = last_revision_el.find("remark")
        if remark_el is not None:
            last_revision["remark"] = remark_el.text

        info["last_revision"] = last_revision

    sig = el.find("sig")
    if sig is not None:
        info["sig"] = sig.text

    if accepted:
        info["number"] = int(el.find("number").text)
    else:
        info["protoname"] = el.find("proto-name").text

    return info


def load_xepinfos(tree):
    accepted, protos = {}, {}
    for info_el in tree.getroot():
        info = load_xepinfo(info_el)
        if info["accepted"]:
            accepted[info["number"]] = info
        else:
            protos[info["protoname"]] = info

    return accepted, protos


def dummy_info(number):
    return {
        "status": None,
        "accepted": False,
        "number": number,
    }


def diff_infos(old, new):
    if old["status"] != new["status"]:
        if new["status"] == Status.PROTO:
            return Action.PROTO
        elif old["status"] is None:
            return Action.NEW
        else:
            return Action.fromstatus(new["status"])

    old_version = old.get("last_revision", {}).get("version")
    new_version = new.get("last_revision", {}).get("version")

    if old_version != new_version:
        return Action.UPDATE

    return None


def wraptext(text):
    return "\n".join(
        itertools.chain(
            *[textwrap.wrap(line) if line else [line] for line in text.split("\n")]
        )
    )


def make_proto_mail(info):
    kwargs = {
        "info": info,
        "approver": info["approver"],
        "url": "{}inbox/{}.html".format(
            XEP_URL_PREFIX,
            info["protoname"],
        ),
    }

    mail = email.message.EmailMessage()
    mail["Subject"] = SUBJECT_PROTO_TEMPLATE.format(**kwargs)
    mail["XSF-XEP-Action"] = "PROTO"
    mail["XSF-XEP-Title"] = info["title"]
    mail["XSF-XEP-Type"] = info["type"]
    mail["XSF-XEP-Status"] = info["status"].value
    mail["XSF-XEP-Url"] = kwargs["url"]
    mail["XSF-XEP-Approver"] = kwargs["approver"]
    mail.set_content(
        wraptext(MAIL_PROTO_TEMPLATE.format(**kwargs)),
        "plain",
        "utf-8",
    )

    return mail


def make_nonproto_mail(action, info):
    last_revision = info.get("last_revision")
    changelog = "(see in-document revision history)"
    if last_revision is not None:
        remark = last_revision.get("remark")
        initials = last_revision.get("initials")
        if remark and initials:
            changelog = "{} ({})".format(remark, initials)

    kwargs = {
        "info": info,
        "changelog": changelog,
        "action": action,
        "url": "{}xep-{:04d}.html".format(
            XEP_URL_PREFIX,
            info["number"],
        ),
    }

    mail = email.message.EmailMessage()
    mail["Subject"] = SUBJECT_NONPROTO_TEMPLATE.format(**kwargs)
    mail["XSF-XEP-Action"] = action.value
    mail["XSF-XEP-Title"] = info["title"]
    mail["XSF-XEP-Type"] = info["type"]
    mail["XSF-XEP-Status"] = info["status"].value
    mail["XSF-XEP-Number"] = "{:04d}".format(info["number"])
    mail["XSF-XEP-Url"] = kwargs["url"]
    mail.set_content(
        wraptext(MAIL_NONPROTO_TEMPLATE.format(**kwargs)),
        "plain",
        "utf-8",
    )

    return mail


def get_or_ask(config, section, name, prompt):
    try:
        return config.get(section, name)
    except (configparser.NoSectionError,
            configparser.NoOptionError):
        return input(prompt)


def interactively_extend_smtp_config(config):
    try:
        host = config.get("smtp", "host")
    except (configparser.NoSectionError,
            configparser.NoOptionError):
        host = input("SMTP server: ").strip()
        port = int(input("SMTP port (blank for 587): ").strip() or "587")
        user = input(
            "SMTP user (leave blank for anon): "
        ).strip() or None
        if user:
            password = getpass.getpass()
        else:
            password = None
    else:
        port = config.getint("smtp", "port", fallback=587)
        user = config.get("smtp", "user", fallback=None)
        password = config.get("smtp", "password", fallback=None)

    try:
        from_ = config.get("smtp", "from")
    except (configparser.NoSectionError,
            configparser.NoOptionError):
        from_ = input("From address: ").strip()

    if not config.has_section("smtp"):
        config.add_section("smtp")
    config.set("smtp", "host", host)
    config.set("smtp", "port", str(port))
    if user:
        config.set("smtp", "user", user)
        if password is None:
            password = getpass.getpass()
        config.set("smtp", "password", password)
    config.set("smtp", "from", from_)


def choose(prompt, options, *,
           eof=EOFError,
           keyboard_interrupt=KeyboardInterrupt):
    while True:
        try:
            choice = input(prompt).strip()
        except EOFError:
            if eof is EOFError:
                raise
            return eof
        except KeyboardInterrupt:
            if keyboard_interrupt is KeyboardInterrupt:
                raise
            return keyboard_interrupt

        if choice not in options:
            print("invalid choice. please enter one of: {}".format(
                ", ".join(map(str, options))
            ))
            continue

        return choice


def make_smtpconn(config):
    host = config.get("smtp", "host")
    port = config.getint("smtp", "port")
    user = config.get("smtp", "user", fallback=None)
    password = config.get("smtp", "password", fallback=None)

    conn = smtplib.SMTP(host, port)
    conn.starttls()
    if user is not None:
        conn.login(user, password)

    return conn


def make_fake_smtpconn():
    class Fake:
        def send_message(self, mail):
            print("---8<---")
            print(mail.as_string())
            print("--->8---")

        def close(self):
            pass

    return Fake()


def main():
    import argparse

    parser = argparse.ArgumentParser(
        description=wraptext(DESCRIPTION),
        epilog=wraptext(EPILOG),
        formatter_class=argparse.RawDescriptionHelpFormatter
    )

    parser.add_argument(
        "-c", "--config",
        metavar="FILE",
        type=argparse.FileType("r"),
        help="Configuration file",
    )
    parser.add_argument(
        "-y",
        dest="ask_confirmation",
        default=True,
        action="store_false",
        help="'I trust this script to do the right thing and send emails"
        "without asking for confirmation.'"
    )
    parser.add_argument(
        "--no-proto",
        dest="process_proto",
        default=True,
        action="store_false",
        help="Disable processing of ProtoXEPs.",
    )
    parser.add_argument(
        "-n", "--dry-run",
        dest="dry_run",
        action="store_true",
        default=False,
        help="Instead of sending emails, print them to stdout (implies -y)",
    )

    parser.add_argument(
        "old",
        type=argparse.FileType("rb"),
        help="Old xep-infos XML file",
    )
    parser.add_argument(
        "new",
        type=argparse.FileType("rb"),
        help="New xep-infos XML file",
    )

    parser.add_argument(
        "to",
        nargs="+",
        help="The mail addresses to send the update mails to."
    )

    args = parser.parse_args()

    can_be_interactive = (
        os.isatty(sys.stdin.fileno()) and
        os.isatty(sys.stdout.fileno())
    )

    if args.dry_run:
        args.ask_confirmation = False

    if args.ask_confirmation and not can_be_interactive:
        print("Cannot ask for confirmation (stdio is not a TTY), but -y is",
              "not given either. Aborting.", sep="\n", file=sys.stderr)
        sys.exit(2)

    config = configparser.ConfigParser()
    if args.config is not None:
        config.read_file(args.config)

    with args.old as f:
        tree = etree.parse(f)
    old_accepted, old_proto = load_xepinfos(tree)

    with args.new as f:
        tree = etree.parse(f)
    new_accepted, new_proto = load_xepinfos(tree)

    old_xeps = set(old_accepted.keys())
    new_xeps = set(new_accepted.keys())

    common_xeps = old_xeps & new_xeps
    added_xeps = new_xeps - old_xeps

    added_protos = set(new_proto.keys()) - set(old_proto.keys())

    updates = []

    for common_xep in common_xeps:
        old_info = old_accepted[common_xep]
        new_info = new_accepted[common_xep]

        action = diff_infos(old_info, new_info)
        if action is not None:
            updates.append((common_xep, action, new_info))

    for added_xep in added_xeps:
        old_info = dummy_info(added_xep)
        new_info = new_accepted[common_xep]

        action = diff_infos(old_info, new_info)
        if action is not None:
            updates.append((added_xep, action, new_info))

    if args.process_proto:
        for added_proto in added_protos:
            old_info = dummy_info('xxxx')
            new_info = new_proto[added_proto]

            action = diff_infos(old_info, new_info)
            if action is not None:
                updates.append((added_proto, action, new_info))

    if args.dry_run:
        smtpconn = make_fake_smtpconn()
    else:
        if can_be_interactive:
            interactively_extend_smtp_config(config)

        try:
            smtpconn = make_smtpconn(config)
        except (configparser.NoSectionError,
                configparser.NoOptionError) as exc:
            print("Missing configuration: {}".format(exc),
                  file=sys.stderr)
            print("(cannot ask for configuration on stdio because it is "
                  "not a TTY)", file=sys.stderr)
            sys.exit(3)

    try:
        for id_, action, info in updates:
            if action == Action.PROTO:
                mail = make_proto_mail(info)
            else:
                mail = make_nonproto_mail(action, info)
            mail["Date"] = datetime.utcnow()
            mail["From"] = config.get("smtp", "from")
            mail["To"] = args.to

            if args.ask_confirmation:
                print()
                print("---8<---")
                print(mail.as_string())
                print("--->8---")
                print()
                choice = choose(
                    "Send this email? [y]es, [n]o, [a]bort: ",
                    "yna",
                    eof="a",
                )

                if choice == "n":
                    continue
                elif choice == "a":
                    print("Exiting on user request.", file=sys.stderr)
                    sys.exit(4)

            smtpconn.send_message(mail)
    finally:
        smtpconn.close()


if __name__ == "__main__":
    main()