__author__ = "Peter Molnar"
__copyright__ = "Copyright 2017-2019, Peter Molnar"
__license__ = "apache-2.0"
__maintainer__ = "Peter Molnar"
__email__ = "mail@petermolnar.net"

import re
import subprocess
import json
import os
import logging
from tempfile import gettempdir

TMPSUBDIR = "nasg"
SHM = "/dev/shm"

if os.path.isdir(SHM) and os.access(SHM, os.W_OK):
    TMPDIR = f"{SHM}/{TMPSUBDIR}"
else:
    TMPDIR = os.path.join(gettempdir(), TMPSUBDIR)

if not os.path.isdir(TMPDIR):
    os.makedirs(TMPDIR)

EXIFDATE = re.compile(
    r"^(?P<year>[0-9]{4}):(?P<month>[0-9]{2}):(?P<day>[0-9]{2})\s+"
    r"(?P<time>[0-9]{2}:[0-9]{2}:[0-9]{2})$"
)


class CachedMeta(dict):
    def __init__(self, fpath):
        self.fpath = fpath
        self.suffix = "cache"

    @property
    def cfile(self):
        fname = os.path.basename(self.fpath)
        if fname == "index.md":
            fname = os.path.basename(os.path.dirname(self.fpath))

        return os.path.join(
            TMPDIR,
            "%s.%s.%s" % (fname, self.__class__.__name__, self.suffix),
        )

    @property
    def _is_cached(self):
        if os.path.exists(self.cfile):
            mtime = os.path.getmtime(self.fpath)
            ctime = os.path.getmtime(self.cfile)
            if ctime >= mtime:
                return True
        return False

    def _read(self):
        if not self._is_cached:
            self._call_tool()
            self._cache_update()
        else:
            self._cache_read()

    def _cache_update(self):
        with open(self.cfile, "wt") as f:
            logging.debug(
                "writing cached meta file of %s to %s", self.fpath, self.cfile
            )
            f.write(json.dumps(self, indent=4, sort_keys=True))

    def _cache_read(self):
        with open(self.cfile, "rt") as f:
            data = json.loads(f.read())
            for k, v in data.items():
                self[k] = v


class Exif(CachedMeta):
    def __init__(self, fpath):
        self.fpath = fpath
        self.suffix = "json.cache"
        self._read()

    def _call_tool(self):
        """
        Why like this: the # on some of the params forces exiftool to
        display values like decimals, so the latitude / longitude params
        can be used and parsed in a sane way

        If only -json is passed, it gets everything nicely, but in the default
        format, which would require another round to parse

        """
        cmd = (
            "exiftool",
            "-sort",
            "-json",
            "-MIMEType",
            "-FileType",
            "-FileName",
            "-FileSize#",
            "-ModifyDate",
            "-CreateDate",
            "-DateTimeOriginal",
            "-ImageHeight",
            "-ImageWidth",
            "-Aperture",
            "-FOV",
            "-ISO",
            "-FocalLength",
            "-FNumber",
            "-FocalLengthIn35mmFormat",
            "-ExposureTime",
            "-Model",
            "-GPSLongitude#",
            "-GPSLatitude#",
            "-LensID",
            "-LensSpec",
            "-Lens",
            "-ReleaseDate",
            "-Description",
            "-Headline",
            "-HierarchicalSubject",
            "-Copyright",
            "-Artist",
            self.fpath,
        )

        p = subprocess.Popen(
            cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE
        )

        stdout, stderr = p.communicate()
        if stderr:
            raise OSError("Error reading EXIF:\n\t%s\n\t%s", cmd, stderr)

        exif = json.loads(stdout.decode("utf-8").strip()).pop()
        if "ReleaseDate" in exif and "ReleaseTime" in exif:
            exif["DateTimeRelease"] = "%s %s" % (
                exif.get("ReleaseDate"),
                exif.get("ReleaseTime")[:8],
            )
            del exif["ReleaseDate"]
            del exif["ReleaseTime"]

        for k, v in exif.items():
            self[k] = self.exifdate2rfc(v)

    def exifdate2rfc(self, value):
        """ converts and EXIF date string to RFC 3339 format

        :param value: EXIF date (2016:05:01 00:08:24)
        :type arg1: str
        :return: RFC 3339 string with UTC timezone 2016-05-01T00:08:24+00:00
        :rtype: str
        """
        if not isinstance(value, str):
            return value
        match = EXIFDATE.match(value)
        if not match:
            return value
        return "%s-%s-%sT%s+00:00" % (
            match.group("year"),
            match.group("month"),
            match.group("day"),
            match.group("time"),
        )