# Copyright 2017 - Tilman 't.animal' Adler

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""" Decreases the time needed to build large galleries (e.g.: 25k images in
2.5s instead of 30s)

This plugin allows extended caching, which is useful for large galleries. Once
a gallery has been built it caches the exif-data of the contained images in the
gallery target folder.  Before the next run it restores them so that the image
does not have to be parsed again. For large galleries this can speed up the
creation of index files dramatically.

"""

import logging
import os
import pickle

from sigal import signals

logger = logging.getLogger(__name__)


def load_exif(album):
    """Loads the exif data of all images in an album from cache"""
    if not hasattr(album.gallery, "exifCache"):
        _restore_cache(album.gallery)
    cache = album.gallery.exifCache

    for media in album.medias:
        if media.type == "image":
            key = os.path.join(media.path, media.dst_filename)
            if key in cache:
                media.exif = cache[key]


def _restore_cache(gallery):
    """Restores the exif data cache from the cache file"""
    cachePath = os.path.join(gallery.settings["destination"], ".exif_cache")
    try:
        if os.path.exists(cachePath):
            with open(cachePath, "rb") as cacheFile:
                gallery.exifCache = pickle.load(cacheFile)
                logger.debug("Loaded cache with %d entries", len(gallery.exifCache))
        else:
            gallery.exifCache = {}
    except Exception as e:
        logger.warn("Could not load cache: %s", e)
        gallery.exifCache = {}


def save_cache(gallery):
    """Stores the exif data of all images in the gallery"""

    if hasattr(gallery, "exifCache"):
        cache = gallery.exifCache
    else:
        cache = gallery.exifCache = {}

    for album in gallery.albums.values():
        for image in album.images:
            cache[os.path.join(image.path, image.dst_filename)] = image.exif

    cachePath = os.path.join(gallery.settings["destination"], ".exif_cache")

    if len(cache) == 0:
        if os.path.exists(cachePath):
            os.remove(cachePath)
        return

    try:
        with open(cachePath, "wb") as cacheFile:
            pickle.dump(cache, cacheFile)
            logger.debug("Stored cache with %d entries", len(gallery.exifCache))
    except Exception as e:
        logger.warn("Could not store cache: %s", e)
        os.remove(cachePath)


def register(settings):
    signals.gallery_build.connect(save_cache)
    signals.album_initialized.connect(load_exif)
