import re
import enum
import datetime

from dateparser.search import search_dates
from email.header      import decode_header

def decode(text: str):
    decoded = decode_header(text)[0]

    if decoded[1] is None:
        return str(decoded[0])

    try:
        return str(decoded[0], decoded[1])
    except:
        return str(decoded[0])

class MessageState(enum.Enum):
    EMPTY  = 0
    HEADER = 1
    BODY   = 2

class Message():
    __slots__ = 'state', 'headers', 'line', 'content', 'body', 'key',

    RE_HEADER     = re.compile(r'^([A-Za-z0-9\-]+): (.*)$')
    RE_MESSAGE_ID = re.compile(r'^<([^<>]+)>$')

    def __init__(self):
        self.state   = MessageState.EMPTY
        self.headers = dict()
        self.line    = None
        self.content = ''
        self.body    = None
        self.key     = None

    def add(self, line: str):
        if self.line is not None:
            self.content += self.line

        if self.state is MessageState.EMPTY:
            self.state = MessageState.HEADER

        if self.state is MessageState.HEADER:
            if line == '\n' or line == '\r\n':
                self.state = MessageState.BODY
            elif line[0] == ' ' or line[0] == '\t':
                self.headers[self.key] += ' ' + decode(line.strip())
            else:
                match = self.RE_HEADER.match(line)

                if match:
                    self.key = match[1].lower()

                    self.headers[self.key] = decode(match[2].rstrip())
        elif self.state is MessageState.BODY:
            if self.body is None:
                self.body = ''
            else:
                self.body += self.line

        self.line = line

    def header(self, key: str):
        return self.headers.get(key.lower())

    def date(self):
        try:
            return search_dates(self.headers['date'])[0][1]
        except:
            return datetime.datetime.fromtimestamp(0)

    def sender(self):
        return self.headers.get('from', 'Unknown')

    def subject(self):
        return self.headers.get('subject', '(no subject)')

    def is_first_line(self):
        return len(self.headers) == 1 and (self.body == '' or self.body is None)

    @staticmethod
    def each_line(text: str):
        start = 0
        end   = len(text)

        while True:
            try:
                index = text.index('\n', start, end)

                yield text[start:index+1]

                start = index + 1

                if start == end:
                    break
            except ValueError:
                yield text[start:end]
                break

    @staticmethod
    def parse(text: str):
        message = MBoxMessage()

        for line in MBoxMessage.each_line(text):
            message.add(line)

        return message