"""一次性修复: 纠正被误标为全文 PDF 的历史记录(Elsevier 摘要预览页 / 损坏文件)。

背景:
  Elsevier Article API 对未授权 / in-press 文章, application/pdf 端点会返回仅含
  摘要的 1 页预览 PDF(魔数仍是 %PDF、体积也不小); 另有部分历史记录把 HTML 错误页 /
  被截断的垃圾当 PDF 存了。旧抓取逻辑只校验魔数 + 体积, 都会误标 has_fulltext_pdf=True。

本命令核对本地 PDF, 分两类处理:
  - 预览页(1 页):   has_fulltext_pdf 置回 False; 文件**仅在 --delete-file 时**删除。
  - 损坏文件(非 PDF / pypdf 解析失败): has_fulltext_pdf 置回 False; 文件**总是删除**
    (dry-run 除外), 因为它根本不是有效全文, 留着无用且会污染下游解析。
  两类在缺少 XML 全文(has_fulltext_xml=False)时, 一并把 has_fulltext 回退 False,
  让其重新进入下载链路去找真正的全文; 并追加 fail_reason 标记供抓取任务排除。

安全前提:
  "损坏"只在铁证下判定 —— 文件不以 %PDF 开头, 或已装 pypdf 且解析直接失败。
  若未装 pypdf 且魔数正常但页数判不出, 归为 unknown, **不处理、绝不删除**。
  强烈建议先 `pip install pypdf` 再跑, 否则只能处理魔数明显不符的坏文件。

用法:
  python manage.py fix_preview_pdf --dry-run
  python manage.py fix_preview_pdf                 # 纠正标记 + 删除坏文件, 保留预览页文件
  python manage.py fix_preview_pdf --delete-file   # 并删除预览页文件
"""
import os

from django.core.management.base import BaseCommand

from apps.resm.models import Paper
from apps.resm.tasks import _inspect_pdf


class Command(BaseCommand):
    help = "纠正被误标为全文的 Elsevier 预览页 / 损坏 PDF"

    def add_arguments(self, parser):
        parser.add_argument("--dry-run", action="store_true",
                            help="只统计, 不写库 / 不删文件")
        parser.add_argument("--limit", type=int, default=0,
                            help="最多处理多少条 (0=不限)")
        parser.add_argument("--delete-file", action="store_true",
                            help="同时删除预览页文件(坏文件无论该开关都会删)")

    def handle(self, *args, **opts):
        dry = opts["dry_run"]
        limit = opts["limit"]
        del_preview = opts["delete_file"]

        qs = Paper.objects.filter(
            has_fulltext_pdf=True, doi__startswith="10.1016"
        ).order_by("id")
        total = qs.count()
        self.stdout.write(
            f"候选(has_fulltext_pdf=True 且 DOI 以 10.1016 开头): {total}")

        checked = preview = broken = only_pdf = deleted = 0
        missing = unknown = 0
        for paper in qs.iterator():
            if limit and checked >= limit:
                break
            checked += 1

            path = paper.init_paper_path("pdf")
            if not os.path.exists(path):
                missing += 1
                continue
            try:
                with open(path, "rb") as f:
                    content = f.read()
            except OSError:
                unknown += 1
                continue

            kind, pages = _inspect_pdf(content)
            if kind == "ok":
                continue
            if kind == "unknown":
                unknown += 1
                continue

            # kind in ('preview', 'broken'): 都要纠正标记
            do_delete = (kind == "broken") or del_preview
            only_pdf_case = not paper.has_fulltext_xml
            if kind == "preview":
                preview += 1
                tag = f"preview {pages}p"
            else:
                broken += 1
                tag = "broken"
            if only_pdf_case:
                only_pdf += 1
            self.stdout.write(
                f"[{tag}]{' (only-pdf)' if only_pdf_case else ''}"
                f"{' +rm' if do_delete else ''} {paper.doi}  {path}")
            if dry:
                continue

            paper.has_fulltext_pdf = False
            update_fields = ["has_fulltext_pdf", "update_time"]
            # 没有 XML 全文时, has_fulltext 之前只是被这张假/坏 PDF 置上的, 一并回退
            if only_pdf_case:
                paper.has_fulltext = False
                update_fields.insert(0, "has_fulltext")
            paper.save(update_fields=update_fields)
            reason = "elsevier_pdf_preview_only" if kind == "preview" else "pdf_broken"
            if reason not in (paper.fail_reason or ""):
                paper.save_fail_reason(reason)
            if do_delete:
                try:
                    os.remove(path)
                    deleted += 1
                except OSError:
                    pass

        self.stdout.write(self.style.SUCCESS(
            f"检查={checked} 预览页={preview} 坏文件={broken} "
            f"(无XML全文一并回退has_fulltext={only_pdf}) 删除文件={deleted} "
            f"文件缺失={missing} 未知/跳过={unknown}"
            + ("  (dry-run, 未写库)" if dry else "")
        ))