"""Private local/S3 storage. All object keys are application-generated."""
import os
import re
import secrets
from functools import lru_cache
from pathlib import Path
from .config import settings

KEY = re.compile(r'^[a-f0-9]{48}/(?:input\.(?:SchDoc|PcbDoc)|(?:old|new)\.(?:SchDoc|PcbDoc)|comparison\.json|pcb-comparison\.json|attempt-[12]/(?:data\.json|drawing\.svg|old\.svg|new\.svg))$')

class Storage:
    def __init__(self):
        self.config = settings()
        if self.config.s3_bucket:
            import boto3
            self.s3 = boto3.client('s3', endpoint_url=self.config.s3_endpoint, region_name=self.config.s3_region)
        else: self.s3 = None

    def path(self, key):
        if not KEY.fullmatch(key): raise ValueError('Invalid storage key')
        p = self.config.storage_dir / 'objects' / key
        if not p.resolve().is_relative_to(self.config.storage_dir / 'objects'):
            raise ValueError('Invalid storage path')
        return p

    def put(self, key, data, content_type='application/octet-stream'):
        p = self.path(key)  # validate on both backends
        if self.s3:
            self.s3.put_object(Bucket=self.config.s3_bucket, Key=key, Body=data, ContentType=content_type)
        else:
            p.parent.mkdir(parents=True, exist_ok=True, mode=0o700)
            tmp = p.with_name(p.name + '.' + secrets.token_hex(8) + '.tmp')
            try:
                with open(tmp, 'xb') as f:
                    os.chmod(tmp, 0o600)
                    f.write(data)
                os.replace(tmp, p)
            finally: tmp.unlink(missing_ok=True)

    def get(self, key):
        p = self.path(key)
        if self.s3:
            with self.s3.get_object(Bucket=self.config.s3_bucket, Key=key)['Body'] as body:
                return body.read()
        return p.read_bytes()

    def delete(self, key):
        p = self.path(key)
        if self.s3: self.s3.delete_object(Bucket=self.config.s3_bucket, Key=key)
        else: p.unlink(missing_ok=True)

@lru_cache
def storage(): return Storage()