"""Bounded metadata cache for display previews, never for inference inputs."""
from collections import OrderedDict
from functools import lru_cache
from pathlib import Path
from threading import RLock
from urllib.parse import quote
import html
import json

from PIL import Image

from documents import load_inputs
from presentation import input_summary
from region_selection import cached_image, region_image, source_key

_CACHE = OrderedDict()
_LOCK = RLock()
_LIMIT = 64
PREVIEW_EDGE = 1280


def display_image(image):
    preview = image.copy()
    preview.thumbnail((PREVIEW_EDGE, PREVIEW_EDGE), Image.Resampling.LANCZOS)
    return preview


@lru_cache(maxsize=64)
def example_thumbnail(path):
    image = load_inputs([path], 'document_markdown', 1)[0]
    image.thumbnail((384, 256))
    return cached_image(image, image_format='webp', quality=75)


def source_preview(paths, task, page, drawing=False, temp_files=None):
    identity = source_key(paths, page)
    key = (identity, tuple(Path(path).suffix.lower() for path in paths), task == 'crosspage_table', drawing)
    with _LOCK:
        entry = _CACHE.get(key)
        if entry is not None and all(Path(path).is_file() for path in (*entry['files'], *entry['originals'])):
            _CACHE.move_to_end(key)
        else:
            entry = None
    if entry is None:
        images = load_inputs(paths, task, page)
        pdf = Path(paths[0]).suffix.lower() == '.pdf'
        originals = [cached_image(image) for image in images] if pdf else list(paths)
        pages = [{'url': './gradio_api/file=' + quote(str(path), safe='/'),
                  'name': f'Page {int(page)+index}' if pdf else Path(path).name,
                  'width': image.width, 'height': image.height}
                 for index, (path, image) in enumerate(zip(originals, images))]
        if drawing:
            files = set()
            region = region_image(images[0], paths, page, temp_files=files,
                                  preview=display_image(images[0]), highres_url=pages[0]['url'])
            values = []
        else:
            files = [cached_image(display_image(image), image_format='webp', quality=75) for image in images]
            region = None
            values = [(path, f'Page {int(page)+index}' if Path(paths[0]).suffix.lower()=='.pdf' else f'Image {index+1}')
                      for index, path in enumerate(files)]
        if pdf:
            files = [*files, *originals]
        metadata = html.escape(json.dumps(pages), quote=True)
        entry = {'files': tuple(files), 'originals': tuple(originals), 'region': region, 'values': values,
                 'summary': input_summary(images, pdf=pdf, page=page)
                            + f'<span hidden data-source-pages="{metadata}"></span>'}
        with _LOCK:
            _CACHE[key] = entry
            _CACHE.move_to_end(key)
            while len(_CACHE) > _LIMIT:
                _CACHE.popitem(last=False)
    if temp_files is not None:
        temp_files.update(entry['files'])
    return entry