"""Environment configuration; production fails closed without upload authentication."""
import os
from dataclasses import dataclass
from functools import lru_cache
from pathlib import Path
from urllib.parse import urlsplit

@dataclass(frozen=True)
class Settings:
    environment: str
    database_url: str
    storage_dir: Path
    api_key: str
    public_url: str
    max_upload_bytes: int
    parse_timeout: int
    link_ttl: int
    max_pending: int
    s3_bucket: str
    s3_endpoint: str | None
    s3_region: str
    storage_backend: str
    s3_prefix: str
    s3_addressing_style: str
    s3_connect_timeout: int
    s3_read_timeout: int
    s3_max_attempts: int
    s3_encryption: str
    s3_kms_key_id: str

@lru_cache
def settings():
    root = Path(os.getenv('STORAGE_DIR', './data')).resolve()
    bucket = os.getenv('S3_BUCKET', '').strip()
    backend = os.getenv('STORAGE_BACKEND', 'auto').strip().lower()
    if backend == 'auto': backend = 's3' if bucket else 'local'
    if backend not in ('local', 's3'):
        raise RuntimeError('STORAGE_BACKEND must be auto, local or s3')
    if backend == 's3' and not bucket:
        raise RuntimeError('S3_BUCKET is required when STORAGE_BACKEND=s3')
    prefix = os.getenv('S3_PREFIX', '').strip('/')
    if (len(prefix.encode('utf-8')) > 512 or '\\' in prefix or
        any(ord(c) < 32 or ord(c) == 127 for c in prefix) or
        (prefix and any(part in ('', '.', '..') for part in prefix.split('/')))):
        raise RuntimeError('S3_PREFIX must be a relative object prefix without empty, dot or traversal segments (max 512 UTF-8 bytes)')
    config = Settings(
        environment=os.getenv('APP_ENV', 'development'),
        database_url=os.getenv('DATABASE_URL', f'sqlite:///{root}/jobs.db'),
        storage_dir=root,
        api_key=os.getenv('API_KEY', ''),
        public_url=os.getenv('PUBLIC_BASE_URL', 'http://127.0.0.1:8000').rstrip('/'),
        max_upload_bytes=int(os.getenv('MAX_UPLOAD_BYTES', str(32 * 1024 * 1024))),
        parse_timeout=int(os.getenv('PARSE_TIMEOUT_SECONDS', '60')),
        link_ttl=int(os.getenv('LINK_TTL_SECONDS', '604800')),
        max_pending=int(os.getenv('MAX_PENDING_JOBS', '100')),
        s3_bucket=bucket,
        s3_endpoint=os.getenv('S3_ENDPOINT_URL') or None,
        s3_region=os.getenv('S3_REGION') or os.getenv('AWS_DEFAULT_REGION') or 'us-east-1',
        storage_backend=backend,
        s3_prefix=prefix,
        s3_addressing_style=os.getenv('S3_ADDRESSING_STYLE', 'auto').strip().lower(),
        s3_connect_timeout=int(os.getenv('S3_CONNECT_TIMEOUT', '5')),
        s3_read_timeout=int(os.getenv('S3_READ_TIMEOUT', '60')),
        s3_max_attempts=int(os.getenv('S3_MAX_ATTEMPTS', '3')),
        s3_encryption=os.getenv('S3_SERVER_SIDE_ENCRYPTION', '').strip(),
        s3_kms_key_id=os.getenv('S3_KMS_KEY_ID', '').strip(),
    )
    if config.environment == 'production' and len(config.api_key) < 32:
        raise RuntimeError('Production requires API_KEY with at least 32 characters')
    if config.environment == 'production' and not config.public_url.startswith('https://'):
        raise RuntimeError('Production requires an HTTPS PUBLIC_BASE_URL')
    if min(config.max_upload_bytes, config.parse_timeout, config.link_ttl, config.max_pending) <= 0:
        raise RuntimeError('Upload, parse, expiry and queue limits must be positive')
    if config.s3_addressing_style not in ('auto', 'path', 'virtual'):
        raise RuntimeError('S3_ADDRESSING_STYLE must be auto, path or virtual')
    if min(config.s3_connect_timeout, config.s3_read_timeout, config.s3_max_attempts) <= 0:
        raise RuntimeError('S3 timeouts and max attempts must be positive')
    if config.s3_encryption not in ('', 'AES256', 'aws:kms'):
        raise RuntimeError('S3_SERVER_SIDE_ENCRYPTION must be empty, AES256 or aws:kms')
    if config.s3_kms_key_id and config.s3_encryption != 'aws:kms':
        raise RuntimeError('S3_KMS_KEY_ID requires S3_SERVER_SIDE_ENCRYPTION=aws:kms')
    if config.s3_endpoint:
        url = urlsplit(config.s3_endpoint)
        if url.scheme not in ('http', 'https') or not url.hostname or url.username or url.password or url.query or url.fragment:
            raise RuntimeError('S3_ENDPOINT_URL must be an HTTP(S) service endpoint without credentials, query or fragment')
    if backend == 'local' or config.database_url.startswith('sqlite:'):
        root.mkdir(parents=True, exist_ok=True, mode=0o700)
    return config