#!/usr/bin/env python
# -*- coding: utf-8 -*-

''' Classes used by main program. '''

from datetime import datetime
import os
import shutil
from fractions import Fraction
import pyexiv2

class Radiation:
    '''
    Reiceives Values vom CSV file and creates a list of the relevant data

    Arguments:
    timestamp: Date/time string from CSV as string
    radiation: Radiation from CSV in CP/M as float
    local_timezone: timezone for timezone-unware CSV / Photo, if GPX is timezone aware
    si_factor: CP/M to (µS/h) conversion factor - specific to GMC-tube
    
    Returns:
    timestamp: timestamp of CSV value als datetime object
    radiation: radiation in µS/h as str (for Exif comment, UTF-8)
    '''

    def __init__(self, timestamp, radiation, local_timezone, si_factor):
        self.timestamp = self._time_conversion(timestamp, local_timezone)
        self.radiation = self._radiation_conversion(radiation, si_factor)

    def __repr__(self):
        return '%s %f µS/h' % (str(self.timestamp), self.radiation)

    def _time_conversion(self, timestamp, local_timezone):
        csv_naive_time = datetime.fromisoformat(timestamp)
        # Set timezone
        csv_aware_time = csv_naive_time.astimezone(local_timezone)
        return csv_aware_time

    def _radiation_conversion(self, radiation, si_factor):
        # Convert CP/M to µS/h using si_factor
        radiation = round(float(radiation) * si_factor, 2)
        return radiation

class Photo:
    '''
    Reads Exif metadata.

    Arguments:
    photo: source photo ()
    local_timezone: timezone for timezone-unware CSV / Photo, if GPX is timezone aware
    dest_dir: destination directory where the photo is going to be copied to.
    dry_run: whether to acutally write (True / False)

    Returns:
    self.get_date: timestamp of photo als datetime object
    self.get_target_photo: full path to photo file to work on
    '''

    def __init__(self, photo, local_timezone, dest_dir, dry_run):
        self.get_date = self._get_creation_date(photo, local_timezone)
        self.get_target_photo = self._copy_photo(photo, dest_dir, dry_run)

    def __repr__(self):
        return 'Photo: %s Creation Date: %s' % (str(self.get_target_photo), str(self.get_date))

    def _copy_photo(self, photo, dest_dir, dry_run):
        # Determine where to work on photo and copy it there if needed.
        # Get image file name out of path
        photo_basename = os.path.basename(photo)
        # be os aware and use the correct directory delimiter for destfile
        dest_photo = os.path.join(dest_dir, photo_basename)

        # Copy photo to dest_dir and return its (new) filename
        # if not in dry_run mode or if dest_dir is different from src_dir.
        if dry_run is True:
            return photo
        if dest_dir != '.':
            shutil.copy(photo, dest_photo)
        return dest_photo

    def _get_creation_date(self, photo, local_timezone):
        # Load Exif data from photo
        metadata = pyexiv2.ImageMetadata(photo)
        metadata.read()
        date = metadata['Exif.Photo.DateTimeOriginal']
        # date.value creates datetime object in pic_naive_time
        pic_naive_time = date.value
        # Set timezone
        pic_aware_time = pic_naive_time.astimezone(local_timezone)
        return pic_aware_time

class Exif:
    '''
    Converts, compiles and writes Exif-Tags from given arguemnts. 
    
    Arguments:
    photo: file name of photo to modify
    radiation: radiation levels in µS/h
    latitude: latitude as float
    longitude: longitude as float
    elevation: elevation as float
    dry_run: whether to acutally write (True / False)

    Returns:
    Latitude / Longitude in degrees
    Exif-Comment that has been written (incl. radiation)
    '''

    def __init__(self, photo, radiation, latitude, longitude, elevation, dry_run):
        self.write_exif = self._write_exif(photo, radiation, latitude,
                                           longitude, elevation, dry_run)

    def __repr__(self):
        return 'Position: %s, %s: %s ' % self.write_exif

    def _to_degree(self, value, loc):
        if value < 0:
            loc_value = loc[0]
        elif value > 0:
            loc_value = loc[1]
        else:
            loc_value = ""
        abs_value = abs(value)
        deg = int(abs_value)
        t1 = (abs_value - deg) * 60
        minute = int(t1)
        second = round((t1 - minute) * 60, 5)
        return (deg, minute, second, loc_value) 

    def _write_exif(self, photo, radiation, latitude, longitude, elevation, dry_run):

        metadata = pyexiv2.ImageMetadata(photo)
        metadata.read()

        latitude_degree = self._to_degree(latitude, ["S", "N"])
        longitude_degree = self._to_degree(longitude, ["W", "E"])

        # convert decimal coordinates into fractions required for pyexiv2
        exiv2_latitude = (Fraction(latitude_degree[0] * 60 + latitude_degree[1], 60),
                          Fraction(int(round(latitude_degree[2] * 100, 0)), 6000),
                          Fraction(0, 1))
        exiv2_longitude = (Fraction(longitude_degree[0] * 60 + longitude_degree[1], 60),
                           Fraction(int(round(longitude_degree[2] * 100, 0)), 6000),
                           Fraction(0, 1))

        # Set new UserComment
        new_comment = 'Radiation ☢ ' + str(radiation) + ' µS/h'
        
        # Exif tags to write
        metadata['Exif.GPSInfo.GPSLatitude'] = exiv2_latitude
        metadata['Exif.GPSInfo.GPSLatitudeRef'] = latitude_degree[3]
        metadata['Exif.GPSInfo.GPSLongitude'] = exiv2_longitude
        metadata['Exif.GPSInfo.GPSLongitudeRef'] = longitude_degree[3]
        metadata['Exif.GPSInfo.GPSAltitude'] = Fraction(elevation)
        metadata['Exif.GPSInfo.GPSAltitudeRef'] = '0'
        metadata['Exif.Image.GPSTag'] = 654
        metadata['Exif.GPSInfo.GPSMapDatum'] = "WGS-84"
        metadata['Exif.GPSInfo.GPSVersionID'] = '2 0 0 0'
        metadata['Exif.Photo.UserComment'] = new_comment

        # Write Exif tags to file, if not in dry-run mode
        if dry_run is not True:
            metadata.write()

        return latitude_degree, longitude_degree, new_comment