"""单篇试验: 尝试从 ScienceDirect 网页(pdfft)下载某 DOI 的真排版 PDF。

用途: 验证"网页直下"在当前服务器 IP / 机构会话下是否可行, 再决定要不要进流水线。
不批量、不轮询, 只对一个 DOI 跑一次, 默认只探测不写库(加 --save 才落盘)。

流程:
  1. 调 Elsevier API(text/xml) 取该 DOI 的 PII
  2. 拼 https://www.sciencedirect.com/science/article/pii/{PII}/pdfft?download=true
  3. 用 curl-cffi 伪装 Chrome 指纹请求(可选注入机构 Cookie)
  4. 用 _inspect_pdf 判定拿到的是真全文(多页)还是预览页/坏内容/被挡(403/HTML)

注意:
  - ScienceDirect 走 Cloudflare + 付费墙, 且页面声明 TDM 预留(应走 API)。
    非机构 IP 通常 403; 机构 IP(订阅按 IP)+ 过 Cloudflare 才可能拿到。
  - 批量爬网页违反 Elsevier 条款且可能导致机构 IP 被封, 此命令仅供单篇可行性验证。

用法:
  python manage.py try_sciencedirect_pdf 10.1016/j.conbuildmat.2026.146897
  python manage.py try_sciencedirect_pdf <doi> --cookie-file cookie.txt
  python manage.py try_sciencedirect_pdf <doi> --cookie "EUID=...; SD_REMOTEACCESS=..." --save
"""
import re

from django.conf import settings
from django.core.management.base import BaseCommand, CommandError

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

_UA = ("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 "
       "(KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36")


class Command(BaseCommand):
    help = "单篇试验: 从 ScienceDirect 网页(pdfft)尝试下载真 PDF"

    def add_arguments(self, parser):
        parser.add_argument("doi", help="目标 DOI, 如 10.1016/j.conbuildmat.2026.146897")
        parser.add_argument("--cookie", default="", help="机构会话 Cookie 头(整串)")
        parser.add_argument("--cookie-file", default="",
                            help="从文件读取 Cookie(优先于 --cookie)")
        parser.add_argument("--save", action="store_true",
                            help="确认拿到真全文 PDF 时落盘到该 Paper")

    def handle(self, *args, **opts):
        doi = opts["doi"].strip()
        cookie = opts["cookie"]
        if opts["cookie_file"]:
            with open(opts["cookie_file"], "r", encoding="utf-8") as f:
                cookie = f.read().strip()

        # 1. 取 PII
        pii = self._fetch_pii(doi)
        if not pii:
            raise CommandError(f"未能从 Elsevier API 取到 PII: {doi}")
        self.stdout.write(f"PII: {pii}")

        url = (f"https://www.sciencedirect.com/science/article/pii/{pii}"
               f"/pdfft?download=true")
        self.stdout.write(f"URL: {url}")

        # 2. curl-cffi 请求
        try:
            import curl_cffi.requests as cf
        except ImportError:
            raise CommandError("curl_cffi 未安装: pip install curl-cffi")

        headers = {
            "User-Agent": _UA,
            "Accept": "application/pdf,application/octet-stream,*/*",
            "Accept-Language": "en-US,en;q=0.9",
            "Referer": f"https://www.sciencedirect.com/science/article/pii/{pii}",
        }
        if cookie:
            headers["Cookie"] = cookie

        try:
            r = cf.get(url, impersonate="chrome131", headers=headers,
                       timeout=60, allow_redirects=True)
        except Exception as e:
            raise CommandError(f"请求失败: {e!r}")

        ctype = r.headers.get("content-type", "")
        content = r.content
        self.stdout.write(
            f"HTTP {r.status_code}  content-type={ctype}  len={len(content)}  "
            f"server={r.headers.get('server')}  cf-ray={r.headers.get('cf-ray')}")
        self.stdout.write(f"最终 URL: {r.url}")

        # 3. 判定内容
        if r.status_code != 200:
            self._diagnose(r.status_code, content)
            return
        kind, pages = _inspect_pdf(content)
        self.stdout.write(f"内容判定: kind={kind} pages={pages}")

        if kind == "ok":
            self.stdout.write(self.style.SUCCESS(
                f"✓ 拿到真全文 PDF ({pages} 页, {len(content)} bytes)"))
            if opts["save"]:
                paper = Paper.objects.filter(doi=doi).first()
                if not paper:
                    self.stdout.write("⚠ 库中无此 DOI, 未落盘")
                else:
                    paper.save_file_pdf(content, save_obj=True)
                    self.stdout.write(self.style.SUCCESS(f"已落盘: {paper.init_paper_path('pdf')}"))
        elif kind == "preview":
            self.stdout.write(self.style.WARNING("✗ 仍是预览页(1 页), 网页这条路对该篇无效"))
        elif kind == "broken":
            head = content[:300].decode("utf-8", "replace").replace("\n", " ")
            self.stdout.write(self.style.WARNING(
                f"✗ 不是有效 PDF(可能被挡/付费墙页). 内容开头: {head}"))
        else:
            self.stdout.write(self.style.WARNING(f"✗ 无法判定: {kind}"))

    def _fetch_pii(self, doi):
        import requests
        from lxml import etree
        H = {"X-ELS-Insttoken": settings.ELSEVIER_INST_TOKEN,
             "X-ELS-APIKey": settings.ELSEVIER_API_KEY}
        try:
            rx = requests.get(
                f"https://api.elsevier.com/content/article/doi/{doi}",
                params={"httpAccept": "text/xml"}, headers=H, timeout=(3, 30))
        except requests.RequestException as e:
            raise CommandError(f"取 XML 失败: {e!r}")
        if rx.status_code != 200:
            raise CommandError(f"取 XML 非 200: {rx.status_code}")
        root = etree.fromstring(rx.content)
        nodes = root.xpath("//*[local-name()='pii']/text()")
        if not nodes:
            return None
        return re.sub(r"[^A-Za-z0-9]", "", nodes[0])

    def _diagnose(self, status, content):
        if status == 403:
            is_cf = b"cloudflare" in content[:5000].lower() or b"cf-" in content[:2000].lower()
            tdm = b"tdm-reservation" in content[:5000]
            self.stdout.write(self.style.WARNING(
                "✗ 403 被拒。" + ("Cloudflare 挑战页。" if is_cf else "")
                + ("页面声明 TDM 预留(应走 API)。" if tdm else "")
                + " 多半是: 该服务器 IP 不在机构订阅网段, 或未带有效机构 Cookie。"))
        elif status in (401, 302, 301):
            self.stdout.write(self.style.WARNING(
                f"✗ {status}: 多半跳登录/未认证, 需要机构会话 Cookie。"))
        else:
            head = content[:300].decode("utf-8", "replace").replace("\n", " ")
            self.stdout.write(self.style.WARNING(f"✗ {status}. 开头: {head}"))