from __future__ import annotations

import tempfile
from pathlib import Path

from fastapi import UploadFile

from app.core.exceptions import AppError
from app.schemas.imports import CaseSqlImportApplyResponse, CaseSqlImportPreviewResponse, CaseSqlPreviewCase
from scripts.import_source_case_sql import ImportValidationError, import_source_sql, parse_source_dump


MAX_SQL_UPLOAD_BYTES = 5 * 1024 * 1024
ALLOWED_TABLES = {"case_base", "traditional_case", "teaching_case", "scoring_rule"}


class CaseSqlImportService:
    """病例 SQL 导入服务：解析接口 SQL 文件并安全映射到当前病例表。"""

    async def preview(self, file: UploadFile) -> CaseSqlImportPreviewResponse:
        """导入预检：上传 SQL 后只解析结构和数据，不写入数据库。"""
        temp_path = await self._save_upload_to_temp(file)
        try:
            parsed, warnings, encoding = parse_source_dump(temp_path)
            table_rows = self._allowed_table_counts(parsed)
            preview_cases = [
                CaseSqlPreviewCase(
                    id=int(row["id"]),
                    title=str(row.get("title") or ""),
                    case_type=str(row.get("case_type") or ""),
                    difficulty=str(row.get("difficulty") or ""),
                )
                for row in parsed.get("case_base", [])
            ]
            return CaseSqlImportPreviewResponse(
                file_name=file.filename or "case.sql",
                encoding=encoding,
                tables=table_rows,
                can_import=True,
                warnings=warnings,
                errors=[],
                preview_cases=preview_cases,
            )
        except ImportValidationError as exc:
            return CaseSqlImportPreviewResponse(
                file_name=file.filename or "case.sql",
                can_import=False,
                errors=[str(exc)],
            )
        finally:
            self._remove_temp_file(temp_path)

    async def apply(self, file: UploadFile) -> CaseSqlImportApplyResponse:
        """确认导入：解析通过后以事务方式写入 case_base/traditional_case/teaching_case/scoring_rule。"""
        temp_path = await self._save_upload_to_temp(file)
        try:
            report = import_source_sql(temp_path, apply=True)
            return CaseSqlImportApplyResponse(
                imported=True,
                file_name=file.filename or "case.sql",
                encoding=report.encoding,
                inserted_or_updated_cases=report.upserted_cases,
                imported_traditional_cases=report.upserted_traditional_cases,
                imported_teaching_cases=report.upserted_teaching_cases,
                imported_scoring_rules=report.replaced_scoring_rules,
                generated_exam_items=report.generated_exam_items,
                warnings=report.warnings,
            )
        except ImportValidationError as exc:
            raise AppError("CASE_SQL_IMPORT_INVALID", str(exc), 400) from exc
        finally:
            self._remove_temp_file(temp_path)

    async def _save_upload_to_temp(self, file: UploadFile) -> Path:
        """上传落盘：校验 SQL 后缀和大小后保存到临时文件，供解析器读取。"""
        filename = file.filename or ""
        if not filename.lower().endswith(".sql"):
            raise AppError("CASE_SQL_FILE_INVALID", "only .sql files are supported", 400)
        content = await file.read()
        if not content:
            raise AppError("CASE_SQL_FILE_EMPTY", "uploaded SQL file is empty", 400)
        if len(content) > MAX_SQL_UPLOAD_BYTES:
            raise AppError("CASE_SQL_FILE_TOO_LARGE", "SQL file is larger than 5MB", 400)

        handle = tempfile.NamedTemporaryFile(delete=False, suffix=".sql")
        try:
            handle.write(content)
            return Path(handle.name)
        finally:
            handle.close()

    def _allowed_table_counts(self, parsed: dict[str, list[dict]]) -> dict[str, int]:
        """表计数：只暴露当前业务允许导入的病例表。"""
        return {table: len(rows) for table, rows in parsed.items() if table in ALLOWED_TABLES}

    def _remove_temp_file(self, path: Path) -> None:
        """临时文件清理：解析或导入完成后删除上传副本。"""
        try:
            path.unlink(missing_ok=True)
        except OSError:
            pass