from __future__ import annotations

import hashlib
from dataclasses import dataclass
from typing import Protocol
from uuid import uuid4

from app.bootstrap.settings import KnowledgeServiceSettings


@dataclass(frozen=True, slots=True)
class StoredObject:
    backend: str
    bucket: str
    object_key: str
    content_type: str
    size_bytes: int
    etag: str | None = None

    def to_metadata(self) -> dict[str, str | int | None]:
        return {
            "backend": self.backend,
            "bucket": self.bucket,
            "objectKey": self.object_key,
            "contentType": self.content_type,
            "sizeBytes": self.size_bytes,
            "etag": self.etag,
        }


@dataclass(frozen=True, slots=True)
class ObjectStorageStatus:
    backend: str
    bucket: str
    object_key: str
    exists: bool
    content_type: str | None = None
    size_bytes: int | None = None
    etag: str | None = None
    error_message: str | None = None


class ObjectStorageError(RuntimeError):
    pass


class ObjectStorageConfigurationError(ObjectStorageError):
    pass


class ObjectStorageNotFoundError(ObjectStorageError, FileNotFoundError):
    pass


class KnowledgeObjectStorage(Protocol):
    def put_bytes(
        self,
        *,
        object_key: str,
        content: bytes,
        content_type: str) -> StoredObject:
        ...

    def get_bytes(self, *, object_key: str) -> bytes:
        ...

    def head_object(self, *, object_key: str) -> ObjectStorageStatus:
        ...

    def delete_object(self, *, object_key: str) -> bool:
        ...

    def health_check(self) -> dict[str, str | bool | None]:
        ...


class InMemoryObjectStorage:
    _buckets: dict[str, dict[str, tuple[bytes, str, str]]] = {}

    def __init__(self, *, bucket: str = "memory-knowledge") -> None:
        self.bucket = bucket
        self._objects = self._buckets.setdefault(bucket, {})

    def put_bytes(
        self,
        *,
        object_key: str,
        content: bytes,
        content_type: str) -> StoredObject:
        etag = hashlib.sha256(content).hexdigest()
        self._objects[object_key] = (content, content_type, etag)
        return StoredObject(
            backend="memory",
            bucket=self.bucket,
            object_key=object_key,
            content_type=content_type,
            size_bytes=len(content),
            etag=etag)

    def get_bytes(self, *, object_key: str) -> bytes:
        try:
            return self._objects[object_key][0]
        except KeyError as exc:
            raise ObjectStorageNotFoundError(f"knowledge object not found: {object_key}") from exc

    def head_object(self, *, object_key: str) -> ObjectStorageStatus:
        stored = self._objects.get(object_key)
        if stored is None:
            return ObjectStorageStatus(
                backend="memory",
                bucket=self.bucket,
                object_key=object_key,
                exists=False,
                error_message=f"knowledge object not found: {object_key}")
        content, content_type, etag = stored
        return ObjectStorageStatus(
            backend="memory",
            bucket=self.bucket,
            object_key=object_key,
            exists=True,
            content_type=content_type,
            size_bytes=len(content),
            etag=etag)

    def delete_object(self, *, object_key: str) -> bool:
        return self._objects.pop(object_key, None) is not None

    def health_check(self) -> dict[str, str | bool | None]:
        return {
            "backend": "memory",
            "bucket": self.bucket,
            "available": True,
            "message": None,
        }


class MinioObjectStorage:
    def __init__(self, *, settings: KnowledgeServiceSettings) -> None:
        try:
            import boto3
            from botocore.config import Config
            from botocore.exceptions import ClientError
        except Exception as exc:
            raise ObjectStorageConfigurationError(
                "boto3 is required for MinIO object storage. "
                "Install knowledge-service dependencies before starting the service."
            ) from exc

        self._client_error_type = ClientError
        self.bucket = settings.object_storage_bucket.strip()
        if not self.bucket:
            raise ObjectStorageConfigurationError("MinIO bucket is required")
        config = Config(
            signature_version="s3v4",
            s3={"addressing_style": "path" if settings.object_storage_path_style else "auto"},
        )
        try:
            self._client = boto3.client(
                "s3",
                endpoint_url=settings.object_storage_endpoint_url,
                aws_access_key_id=settings.object_storage_access_key,
                aws_secret_access_key=settings.object_storage_secret_key,
                region_name=settings.object_storage_region,
                config=config,
            )
        except Exception as exc:
            raise ObjectStorageConfigurationError("failed to configure MinIO client") from exc
        self._bucket_checked = False

    def put_bytes(
        self,
        *,
        object_key: str,
        content: bytes,
        content_type: str) -> StoredObject:
        try:
            self._ensure_bucket()
            response = self._client.put_object(
                Bucket=self.bucket,
                Key=object_key,
                Body=content,
                ContentType=content_type,
            )
        except self._client_error_type as exc:
            raise ObjectStorageError(f"failed to write knowledge object: {object_key}") from exc
        etag = response.get("ETag")
        return StoredObject(
            backend="minio",
            bucket=self.bucket,
            object_key=object_key,
            content_type=content_type,
            size_bytes=len(content),
            etag=str(etag).strip('"') if etag else None)

    def get_bytes(self, *, object_key: str) -> bytes:
        try:
            response = self._client.get_object(Bucket=self.bucket, Key=object_key)
        except self._client_error_type as exc:
            if self._is_not_found(exc):
                raise ObjectStorageNotFoundError(f"knowledge object not found: {object_key}") from exc
            raise ObjectStorageError(f"failed to read knowledge object: {object_key}") from exc
        try:
            return response["Body"].read()
        finally:
            response["Body"].close()

    def head_object(self, *, object_key: str) -> ObjectStorageStatus:
        try:
            response = self._client.head_object(Bucket=self.bucket, Key=object_key)
        except self._client_error_type as exc:
            if self._is_not_found(exc):
                return ObjectStorageStatus(
                    backend="minio",
                    bucket=self.bucket,
                    object_key=object_key,
                    exists=False,
                    error_message=f"knowledge object not found: {object_key}")
            raise ObjectStorageError(f"failed to stat knowledge object: {object_key}") from exc
        return ObjectStorageStatus(
            backend="minio",
            bucket=self.bucket,
            object_key=object_key,
            exists=True,
            content_type=response.get("ContentType"),
            size_bytes=response.get("ContentLength"),
            etag=str(response.get("ETag")).strip('"') if response.get("ETag") else None)

    def delete_object(self, *, object_key: str) -> bool:
        try:
            existed = self.head_object(object_key=object_key).exists
            self._client.delete_object(Bucket=self.bucket, Key=object_key)
            return existed
        except ObjectStorageError:
            raise
        except self._client_error_type as exc:
            raise ObjectStorageError(f"failed to delete knowledge object: {object_key}") from exc

    def health_check(self) -> dict[str, str | bool | None]:
        try:
            self._ensure_bucket()
        except ObjectStorageError as exc:
            return {
                "backend": "minio",
                "bucket": self.bucket,
                "available": False,
                "message": str(exc),
            }
        return {
            "backend": "minio",
            "bucket": self.bucket,
            "available": True,
            "message": None,
        }

    def _ensure_bucket(self) -> None:
        if self._bucket_checked:
            return
        try:
            self._client.head_bucket(Bucket=self.bucket)
        except self._client_error_type as exc:
            if not self._is_not_found(exc):
                raise ObjectStorageError(f"failed to access MinIO bucket: {self.bucket}") from exc
            try:
                self._client.create_bucket(Bucket=self.bucket)
            except self._client_error_type as create_exc:
                raise ObjectStorageError(f"failed to create MinIO bucket: {self.bucket}") from create_exc
        self._bucket_checked = True

    def _is_not_found(self, exc: Exception) -> bool:
        response = getattr(exc, "response", None)
        if not isinstance(response, dict):
            return False
        error = response.get("Error")
        status = response.get("ResponseMetadata", {}).get("HTTPStatusCode")
        code = error.get("Code") if isinstance(error, dict) else None
        return status == 404 or code in {"404", "NoSuchBucket", "NoSuchKey", "NotFound"}


def build_object_storage(settings: KnowledgeServiceSettings) -> KnowledgeObjectStorage:
    backend = settings.object_storage_backend.strip().lower()
    if backend == "memory":
        return InMemoryObjectStorage(bucket=settings.object_storage_bucket)
    if backend == "minio":
        return MinioObjectStorage(settings=settings)
    raise ValueError(f"unsupported knowledge object storage backend: {settings.object_storage_backend}")


def build_document_object_key(
    *,
    knowledge_base_id: str,
    source_type: str,
    title: str) -> str:
    safe_title = "".join(
        char.lower() if char.isalnum() else "-"
        for char in title
    ).strip("-") or "document"
    suffix = source_type.strip().lower().removeprefix(".") or "txt"
    return f"knowledge/{knowledge_base_id}/documents/{uuid4().hex}/{safe_title[:80]}.{suffix}"