"""文档服务：上传、删除、配额管理。"""

import hashlib
from pathlib import Path

import filetype

from app.core.config import get_settings
from app.core.errors import (
    FileTooLargeError,
    FileTypeUnsupportedError,
    NotFoundError,
    StorageQuotaExceededError,
)
from app.core.security import decrypt_token, encrypt_token, generate_token, hash_token
from app.models.document import Document
from app.models.user import User
from app.repositories.doc_repo import DocumentRepository
from app.repositories.kb_repo import KnowledgeBaseRepository
from app.storage.local_storage import get_storage
from app.storage.object_keys import original_object_key
from sqlalchemy.orm import Session

# 允许的文件扩展名
ALLOWED_EXTENSIONS = {".docx", ".pdf"}
ALLOWED_MIMES = {
    "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
    "application/pdf",
}


class DocumentService:
    def __init__(self, session: Session) -> None:
        self._session = session
        self._doc_repo = DocumentRepository(session)
        self._kb_repo = KnowledgeBaseRepository(session)

    def upload(
        self,
        user: User,
        kb_id: str,
        filename: str,
        content: bytes,
        category_id: str | None = None,
    ) -> Document:
        """上传文档。

        流程：校验 KB 归属 → 文件大小 → 扩展名/MIME → 配额 → SHA256 → 存储 → 入库
        """
        # 校验 KB 归属
        kb = self._kb_repo.get_by_id(kb_id)
        if kb is None or kb.user_id != user.id or kb.status == "DELETED":
            raise NotFoundError("知识库不存在。")

        settings = get_settings()

        # 文件大小
        if len(content) > settings.default_max_file_size:
            raise FileTooLargeError(
                f"单文件大小超出限制（最大 {settings.default_max_file_size // (1024*1024)}MB）。"
            )

        # 扩展名
        ext = Path(filename).suffix.lower()
        if ext not in ALLOWED_EXTENSIONS:
            raise FileTypeUnsupportedError(
                f"不支持的文件类型 '{ext}'。当前支持：{', '.join(sorted(ALLOWED_EXTENSIONS))}"
            )

        # MIME 嗅探（前 8KB）——仅用于辅助校验，扩展名为主
        kind = filetype.guess(content[:8192])
        detected_mime = kind.mime if kind else ""
        # .docx 底层是 ZIP，filetype 会识别为 application/zip，这是正常的
        # 只在检测到明确不属于文档类型的 MIME 时才拒绝（如图片、视频等）
        BLOCKED_MIMES = {"image/jpeg", "image/png", "video/mp4", "audio/mpeg", "application/x-executable"}
        if detected_mime in BLOCKED_MIMES:
            raise FileTypeUnsupportedError(f"文件内容类型不受支持：{detected_mime}")

        # 配额检查（原子 SQL）
        file_size = len(content)
        self._check_quota(user, file_size)

        # SHA256
        sha256 = hashlib.sha256(content).hexdigest()

        # 生成文档 token
        doc_token = generate_token()
        doc_token_hash = hash_token(doc_token)
        doc_token_encrypted = encrypt_token(doc_token)
        doc_token_hint = doc_token[-8:] if len(doc_token) >= 8 else doc_token

        # 存储原始文件
        storage_key = original_object_key(
            user_id=user.id,
            knowledge_base_id=kb_id,
            document_id="pending",  # 先存文件，入库后更新路径
            original_filename=filename,
        )
        storage = get_storage()
        storage.save(storage_key, content)

        # 入库
        doc = self._doc_repo.create(
            knowledge_base_id=kb_id,
            user_id=user.id,
            original_filename=filename,
            storage_path=storage_key,
            file_size=file_size,
            mime_type=detected_mime or "application/octet-stream",
            file_ext=ext,
            sha256=sha256,
            doc_token_hash=doc_token_hash,
            doc_token_encrypted=doc_token_encrypted,
            doc_token_hint=doc_token_hint,
            category_id=category_id,
        )

        # 更新存储路径中的 document_id
        actual_key = original_object_key(
            user_id=user.id,
            knowledge_base_id=kb_id,
            document_id=doc.id,
            original_filename=filename,
        )
        # 移动文件到正确路径
        if actual_key != storage_key:
            storage.save(actual_key, storage.delete(storage_key) or content)
            doc.storage_path = actual_key

        # 扣减配额（原子 SQL）
        self._deduct_quota(user, file_size)

        self._session.commit()

        # 同步解析文档（MVP：阻塞式）
        self._process_document(doc)

        return doc

    def get_or_404(self, doc_id: str, user: User) -> Document:
        doc = self._doc_repo.get_by_id(doc_id)
        if doc is None or doc.user_id != user.id or doc.status == "DELETED":
            raise NotFoundError("文档不存在。")
        return doc

    def list_by_knowledge_base(
        self, kb_id: str, user: User, *, category_id: str | None = None, page: int = 1, page_size: int = 50
    ):
        # 校验 KB 归属
        kb = self._kb_repo.get_by_id(kb_id)
        if kb is None or kb.user_id != user.id or kb.status == "DELETED":
            raise NotFoundError("知识库不存在。")
        return self._doc_repo.list_by_knowledge_base(kb_id, category_id=category_id, page=page, page_size=page_size)

    def delete(self, doc_id: str, user: User) -> None:
        doc = self.get_or_404(doc_id, user)
        file_size = doc.file_size
        self._doc_repo.delete(doc)
        # 回补配额
        self._restore_quota(user, file_size)
        self._session.commit()

    def _check_quota(self, user: User, file_size: int) -> None:
        settings = get_settings()
        if user.storage_used + file_size > settings.default_storage_quota:
            raise StorageQuotaExceededError(
                f"存储空间不足（已用 {user.storage_used // (1024*1024)}MB，"
                f"上传 {file_size // (1024*1024)}MB，"
                f"总配额 {settings.default_storage_quota // (1024*1024)}MB）。"
            )

    def _deduct_quota(self, user: User, file_size: int) -> None:
        """原子扣减配额。"""
        from sqlalchemy import update

        stmt = (
            update(User)
            .where(User.id == user.id, User.storage_used + file_size <= get_settings().default_storage_quota)
            .values(storage_used=User.storage_used + file_size)
        )
        result = self._session.execute(stmt)
        if result.rowcount == 0:
            raise StorageQuotaExceededError("存储空间不足（并发上传导致）。")
        # 更新本地对象
        user.storage_used += file_size

    def _restore_quota(self, user: User, file_size: int) -> None:
        """回补配额。"""
        from sqlalchemy import update

        stmt = (
            update(User)
            .where(User.id == user.id)
            .values(storage_used=User.storage_used - file_size)
        )
        self._session.execute(stmt)
        user.storage_used = max(0, user.storage_used - file_size)

    def _process_document(self, doc: Document) -> None:
        """同步处理文档（MVP 阶段，阻塞式）。"""
        from app.processors.local_processor import LocalDocumentProcessor

        processor = LocalDocumentProcessor(self._session)
        processor.process(doc.id)

    def create_text(
        self,
        user: User,
        kb_id: str,
        title: str,
        content: str,
        content_format: str = "markdown",
        category_id: str | None = None,
    ) -> Document:
        """创建文本内容文档（无需上传文件）。"""
        # 校验 KB 归属
        kb = self._kb_repo.get_by_id(kb_id)
        if kb is None or kb.user_id != user.id or kb.status == "DELETED":
            raise NotFoundError("知识库不存在。")

        # 生成文档 token
        doc_token = generate_token()
        doc_token_hash = hash_token(doc_token)
        doc_token_encrypted = encrypt_token(doc_token)
        doc_token_hint = doc_token[-8:] if len(doc_token) >= 8 else doc_token

        # 计算内容大小
        content_size = len(content.encode("utf-8"))

        # 配额检查
        self._check_quota(user, content_size)

        # 从内容提取摘要和关键词
        summary = self._extract_summary(content)
        keywords = self._extract_keywords(content)

        # 创建文档记录
        doc = Document(
            knowledge_base_id=kb_id,
            user_id=user.id,
            category_id=category_id,
            original_filename=title,
            storage_path=None,  # 文本内容不存储文件
            markdown_path=None,
            content=content,
            content_format=content_format,
            file_size=content_size,
            mime_type="text/markdown" if content_format == "markdown" else "text/plain",
            file_ext=".md" if content_format == "markdown" else ".txt",
            sha256=None,
            doc_token_hash=doc_token_hash,
            doc_token_encrypted=doc_token_encrypted,
            doc_token_hint=doc_token_hint,
            title=title,
            content_summary=summary,
            keywords=keywords,
            status="READY",  # 文本内容直接就绪
        )
        self._session.add(doc)

        # 扣减配额
        self._deduct_quota(user, content_size)

        self._session.commit()
        return doc

    def _extract_summary(self, content: str, max_len: int = 200) -> str:
        """提取摘要。"""
        import re

        text = re.sub(r"[#*_`\[\]()>]", "", content)
        text = re.sub(r"\s+", " ", text).strip()
        if len(text) <= max_len:
            return text
        return text[:max_len] + "..."

    def _extract_keywords(self, content: str, top_k: int = 10) -> str:
        """提取关键词。"""
        try:
            import jieba.analyse
            import re

            text = re.sub(r"[#*_`\[\]()>]", "", content)
            text = re.sub(r"\s+", " ", text).strip()
            keywords = jieba.analyse.extract_tags(text, topK=top_k)
            return ",".join(keywords)
        except Exception:
            return ""