"""Answer provenance and reproducible annotation spacing (200 dpi pixels)."""
from hashlib import sha256
from pathlib import Path
import shutil

import pymupdf

from copienator import configuration
from copienator.json_io import atomic_write_json, read_json


def fingerprint(path):
    return sha256(Path(path).read_bytes()).hexdigest()


def metadata_path(pdf):
    return Path(pdf).with_suffix('.layout.json')


def answer_parts(pdf):
    """Ignore stale sidecars after a PDF is replaced or manually edited."""
    if pdf is None or not Path(pdf).is_file():
        return []
    try:
        data = read_json(metadata_path(pdf), default={})
        if data.get('sha256') == fingerprint(pdf):
            parts = data.get('parts', [])
            if isinstance(parts, list) and all(isinstance(part, dict) for part in parts):
                return parts
    except (OSError, ValueError, TypeError, AttributeError):
        pass
    return []


def save_parts(pdf, parts):
    atomic_write_json(metadata_path(pdf), {
        'version': 1, 'sha256': fingerprint(pdf), 'parts': parts,
    })


def page_parts(pdf):
    parts = answer_parts(pdf)
    if not Path(pdf).is_file():
        return []
    with pymupdf.open(pdf) as document:
        if len(parts) == len(document):
            return parts
        return [{'margin_status': 'unknown'} for _ in document]


def copy_answer_pdf(source, destination):
    parts = answer_parts(source)
    shutil.copy(source, destination)
    save_parts(destination, parts)


def move_answer_pdf(source, destination):
    parts = answer_parts(source)
    shutil.move(str(source), str(destination))
    save_parts(destination, parts)
    metadata_path(source).unlink(missing_ok=True)


def layout_for(pdf):
    low = any(part.get('margin_status') == 'low' for part in answer_parts(pdf))
    margin = (configuration.ANNOTATION_LOW_MARGIN_LEFT if low
              else configuration.ANNOTATION_MARGIN_LEFT)
    if type(margin) is not int or margin < 0:
        raise ValueError('Annotation left margins must be non-negative integers')
    return {'version': 1, 'margin_left': margin, 'narrow_left_pad_limit': 300}


def legacy_layout():
    # Old annotation scans were produced with these literal constants.
    return {'version': 1, 'margin_left': 300, 'narrow_left_pad_limit': 300}