#!/usr/bin/python3

import email.parser
import hashlib
import html
import html.parser
import mailbox
import os
import re
import subprocess
import sys
import tempfile
import urllib.parse

import jinja2

basedir = "."

jenv = jinja2.Environment(
                loader=jinja2.FileSystemLoader(["templates"]),
                autoescape=True,
              )

def get_message_id(msg):
    """
    Extract the message id from a message

    Note that this assumes that there is (at least) one message id. If
    this is not the case, it will raise an exception (currently an
    IndexError, but we may use something more suitable in the future).
    """
    match = re.search(r'<(.*?)>', msg["Message-ID"])
    return match.group(1)

def encode_message_id(msgid):
    encmsgid = re.sub('[^!"$(-.0-9:=@-z|~]', lambda x: "{%02x}" % (ord(x.group(0))), msgid)
    return encmsgid

def render_message(msg):
    msgtmpl = jenv.get_template("message2.html")
    bodyhtml = render_body(msg)
    context = {
        "message_id": msg["Message-Id"],
        "subject": msg["Subject"],
        "from": msg["From"],
        "date": msg["Date"],
        "bodyhtml": bodyhtml,
    }
    msghtml = msgtmpl.render(context)
    return jinja2.Markup(msghtml)

partial_message_cache = {}

def render_body(msg):
    content_type = msg.get_content_type()

    if content_type == "text/plain":
        bodytmpl = jenv.get_template("body_text_plain.html")
        context = {
            "body": msg.get_payload(decode=True).decode(msg.get_charset() or "iso-8859-1")
        }
        bodyhtml = bodytmpl.render(context)
    elif content_type == "multipart/mixed":
        partshtml = []
        for part in msg.get_payload():
            partshtml.append(render_body(part))
        bodytmpl = jenv.get_template("body_multipart_mixed.html")
        context = {
            "parts": partshtml
        }
        bodyhtml = bodytmpl.render(context)
    elif content_type == "multipart/digest":
        partshtml = []
        for part in msg.get_payload():
            partshtml.append(render_message(part))
        bodytmpl = jenv.get_template("body_multipart_digest.html")
        context = {
            "parts": partshtml
        }
        bodyhtml = bodytmpl.render(context)
    elif content_type == "message/rfc822":
        partshtml = []
        for part in msg.get_payload():
            partshtml.append(render_message(part))
        bodytmpl = jenv.get_template("body_message_rfc822.html")
        context = {
            "parts": partshtml
        }
        bodyhtml = bodytmpl.render(context)
    elif content_type == "text/html":
        htmlpart = HTMLPart()
        htmlpart.feed(msg.get_payload(decode=True).decode(msg.get_charset() or "iso-8859-1"))
        bodytmpl = jenv.get_template("body_text_html.html")
        context = {
            "body": jinja2.Markup(htmlpart.as_string())
        }
        bodyhtml = bodytmpl.render(context)
    elif content_type == "text/enriched":
        tepart = TextEnrichedPart(msg.get_payload())
        bodytmpl = jenv.get_template("body_text_enriched.html")
        context = {
            "body": jinja2.Markup(tepart.as_string())
        }
        bodyhtml = bodytmpl.render(context)
    elif content_type == "message/partial":
        # Default header for get_param is Content-Type
        whole_msg_id = msg.get_param("id")
        if not whole_msg_id in partial_message_cache:
            # For now we assume that total is present on all parts. This
            # isn't guarantueed, however, and we may need to handle the 
            # case where total is only present on the last part.
            partial_message_cache[whole_msg_id] = [None] * int(msg.get_param("total"))
        payload = msg.get_payload()
        s = payload[0].as_string() # Only one part
        partial_message_cache[whole_msg_id][int(msg.get_param("number"))-1] = s
        if not None in partial_message_cache[whole_msg_id]:
            p = email.parser.Parser()
            whole_msg = p.parsestr("".join(partial_message_cache[whole_msg_id]))
            whole_msg_embedded_id = whole_msg["Message-Id"]
            if not whole_msg_embedded_id:
                whole_msg.add_header("Message-Id", "<" + whole_msg_id + ">")
                whole_msg_embedded_id = whole_msg_id
            archive(whole_msg)
            del partial_message_cache[whole_msg_id]
        bodyhtml = "<p>This is part %d of %d of <a href='../%s/'>%s</a></p>" % (
                        int(msg.get_param("number")),
                        int(msg.get_param("total")),
                        encode_message_id(whole_msg_id),
                        html.escape(whole_msg_id))

    elif content_type == "application/octet-stream":
        name = msg.get_param("name") or "(data)"
        m = hashlib.sha256()
        payload = msg.get_payload(decode=True)
        m.update(payload)
        filename = m.hexdigest() + ".bin"
        os.makedirs("parts", exist_ok=True)
        with open("parts/" + filename, "wb") as fh:
            fh.write(payload)
        bodytmpl = jenv.get_template("body_application_octet_stream.html")
        context = {
            "name": name,
            "url": "../../parts/" + filename,
        }
        bodyhtml = bodytmpl.render(context)

    elif content_type == "multipart/signed":
        content, signature = msg.get_payload()
        with tempfile.NamedTemporaryFile(buffering=0) as content_fh:
            content_fh.write(content.as_bytes())
            with tempfile.NamedTemporaryFile(buffering=0, suffix=".asc") as signature_fh:
                signature_fh.write(signature.get_payload(decode=True))

                r = subprocess.run(["gpg", "--verify", signature_fh.name, content_fh.name],
                                   stdout=subprocess.PIPE,
                                   stderr=subprocess.PIPE,
                                   universal_newlines=True)
                gpgresult = r.stderr
                # Analyze gpgresult or just use r,returncode?
                gpgstatus = "dubious"

        contenthtml = render_message(content)
        bodytmpl = jenv.get_template("body_multipart_signed.html")
        context = {
            "content": contenthtml,
            "gpgresult": gpgresult,
            "gpgstatus": gpgstatus,
        }
        bodyhtml = bodytmpl.render(context)

    else:
        raise RuntimeError("Content-type " + content_type + " not implemented yet")

    return jinja2.Markup(bodyhtml)


def archive(msg):
    mid = get_message_id(msg)
    encmid = encode_message_id(mid)
    msgdir = basedir + "/msg/" + encmid
    os.makedirs(msgdir, exist_ok=True)
    with open(msgdir + "/index.html", "w") as hfd:
        msgtmpl = jenv.get_template("message.html")
        bodyhtml = render_body(msg)
        context = {
            "list": "LUGA",
            "message_id": mid,
            "subject": msg["Subject"],
            "from": msg["From"],
            "date": msg["Date"],
            "bodyhtml": bodyhtml,
        }
        msghtml = msgtmpl.render(context)
        hfd.write(msghtml)


class HTMLPart(html.parser.HTMLParser):
    allowed_tags = [
        "h2", "a", "wbr", "hr", "pre", "img", "font", "i", "br", "table", "tr",
        "th", "td", "b", "select", "option", "input", "sup", "address",
        "center", "p", "h1", "dl", "h3", "ul", "li", "ol", "u"
    ]
    hide_tags = [ "title" ]
    ignore_tags = [ "html", "head", "body", "marquee", "meta", "form", ]

    def __init__(self):
        super().__init__()
        self.hide = False
        self.content = []

    def handle_starttag(self, tag, attrs):
        if tag == "base":
            href = [x[1] for x in attrs if x[0] == "href"]
            if href:
                self.base = href[0]
        elif tag in self.allowed_tags:
            attrstr = "".join(
                            [' %s="%s"' % (a[0],  html.escape(a[1])) if a[1] else ' %s' % (a[0])
                                for a in self.clean_attrs(tag, attrs)
                            ]
                         )
            self.content.append("<%s%s>" % ( tag, attrstr ))
        elif tag in self.hide_tags:
            self.hide = True
        elif tag in self.ignore_tags:
            pass
        else:
            print("Encountered unknown start tag", tag, attrs, file=sys.stderr)

    def handle_endtag(self, tag):
        if tag in self.allowed_tags:
            self.content.append("</%s>" % tag)
        elif tag in self.hide_tags:
            self.hide = False # XXX - Need stack?
        elif tag in self.ignore_tags:
            pass
        else:
            print("Encountered unknown end tag", tag, file=sys.stderr)

    def handle_data(self, data):
        if not self.hide:
            self.content.append(data)

    def as_string(self):
        return "".join(self.content)

    def clean_attrs(self, tag, attrs):
        safe_attrs = [
            "border", "alt", "size", "face", "width", "height", "hspace",
            "cellpadding", "cellspacing", "bgcolor", "valign", "nowrap",
            "color", "colspan", "name", "value", "type", "align", "clear",
            "noshade"
        ]
        clean_attrs = []
        for a in attrs:
            if a[0] in safe_attrs:
                clean_attrs.append(a)
            elif a[0] == "href":
                url = a[1]
                url = urllib.parse.urljoin(self.base, url)
                u = urllib.parse.urlparse(url)
                if u[0] in ['https', 'http', 'ftp']:
                    clean_attrs.append((a[0], url))
            elif a[0] == "src":
                url = a[1]
                url = urllib.parse.urljoin(self.base, url)
                u = urllib.parse.urlparse(url)
                if u[0] == "cid":
                    print("Encountered src cid attribute", a, file=sys.stderr)
                    # XXX - implement cid
                    clean_attrs.append((a[0], url))
                else:
                    print("Ignored src attribute", a, file=sys.stderr)
            elif a[0] == "target":
                pass
            else:
                print("Encountered unknown attribute", a, file=sys.stderr)
        return clean_attrs


class TextEnrichedPart:
    class TEElement:
        def __init__(self, t):
            self.type = t.lower()
            self.content = []
            self.filled = True
        
        def append_text(self, s):
            s = s.replace("<<", "<")
            if self.filled:
                s = re.sub(r'\n+',
                           lambda m: m.group(0)[1:] if len(m.group(0)) > 1 else " ",
                           s)
            self.content.append(s)

        def as_string(self):
            if self.type == "":
                pre = "<div class='text-enriched'>"
                post = "</div>"
            elif self.type == "bold":
                pre = "<b>"
                post = "</b>"
            else:
                raise NotImplementedError("Unknown type " + self.type)

            s = pre
            for c in self.content:
                if isinstance(c, type(self)):
                    s += c.as_string()
                else:
                    s += html.escape(c)
            s += post
            return s

    def __init__(self, s):
        self.stack = [ self.TEElement("") ]
        while s:
            stack_top = self.stack[-1]
            m = re.match(r'(.*?)<(/?[A-Za-z0-9-]{,60})>(.*)', s, re.DOTALL)
            if m:
                if m.group(2).lower == "param" and re.match(r'\s*', m.group(1)):
                    stack_top.content.append(TEElement("param"))
                else:
                    stack_top.append_text(m.group(1))
                    if m.group(2)[0] != "/":
                        new = self.TEElement(m.group(2))
                        stack_top.content.append(new)
                        self.stack.append(new)
                    else:
                        if stack_top.type == m.group(2)[1:]:
                            self.stack.pop()
                        else:
                            raise RuntimeError("Nesting error: Expected %s, got %s near %s", self.stack[-1].type, m.group(2)[1:], s)
                s = m.group(3)
            else:
                stack_top.append_text(s)
                s = ""

    def as_string(self):
        return self.stack[0].as_string()


for f in sys.argv[1:]:
    print("F", f, file=sys.stderr)
    mb = mailbox.mbox(f)

    for m in mb:
        archive(m)

# vim: tw=79