"""GitHub元数据预检传输：凭据仅留在HTTPS API源，不跟随外部跳转。"""
import re
import time
import urllib.error
import urllib.parse
import urllib.request
from github_source import repository_parts

MAX_PROBE_TIMEOUT = 10
MAX_PROBE_REDIRECTS = 3


def _metadata_target(url):
    if (not isinstance(url, str) or len(url) > 2048
            or any(ord(char) <= 32 or ord(char) >= 127 for char in url)
            or "\\" in url or "?" in url or "#" in url):
        raise ValueError("invalid GitHub metadata target")
    parsed = urllib.parse.urlsplit(url)
    if (parsed.scheme != "https" or parsed.hostname != "api.github.com"
            or parsed.username is not None or parsed.password is not None
            or parsed.port not in (None, 443) or parsed.netloc.endswith(":")):
        raise ValueError("invalid GitHub metadata origin")
    if parsed.path.startswith("/repos/"):
        repository_parts("https://github.com/" + parsed.path[len("/repos/"):])
    elif not re.fullmatch(r"/repositories/[0-9]{1,20}", parsed.path):
        raise ValueError("invalid GitHub metadata path")
    return url


class GithubMetadataRedirect(urllib.request.HTTPRedirectHandler):
    max_redirections = MAX_PROBE_REDIRECTS
    max_repeats = 1

    def __init__(self, deadline):
        self.deadline = deadline

    def redirect_request(self, req, fp, code, msg, headers, newurl):
        try:
            _metadata_target(req.full_url)
            _metadata_target(newurl)
        except ValueError:
            raise urllib.error.HTTPError(req.full_url, code, "GitHub预检跳转不允许", {}, fp) from None
        remaining = self.deadline - time.monotonic()
        if remaining <= 0:
            fp.close()
            raise TimeoutError("GitHub metadata probe timed out")
        # urllib的父处理器使用旧req.timeout传给下一跳；收紧到剩余预算。
        req.timeout = min(getattr(req, "timeout", MAX_PROBE_TIMEOUT), remaining)
        return super().redirect_request(req, fp, code, msg, headers, newurl)


    def http_error_302(self, req, fp, code, msg, headers):
        location = headers.get("location") or headers.get("uri")
        if not isinstance(location, str) or not location or len(location) > 2048:
            raise urllib.error.HTTPError(req.full_url, code, "GitHub预检跳转无效", {}, fp)
        try:
            target = urllib.parse.urljoin(req.full_url, location)
        except ValueError:
            raise urllib.error.HTTPError(req.full_url, code, "GitHub预检跳转无效", {}, fp) from None
        new_request = self.redirect_request(req, fp, code, msg, headers, target)
        count = getattr(req, "_ranking_probe_redirects", 0)
        seen = getattr(req, "_ranking_probe_seen", {req.full_url})
        if new_request is None or count >= MAX_PROBE_REDIRECTS or target in seen:
            raise urllib.error.HTTPError(req.full_url, code, "GitHub预检跳转次数过多", {}, fp)
        new_request._ranking_probe_redirects = count + 1
        new_request._ranking_probe_seen = seen | {target}
        # 只看元数据状态：关闭跳转正文，不使用urllib默认的无界fp.read()。
        fp.close()
        return self.parent.open(new_request, timeout=req.timeout)

    http_error_301 = http_error_303 = http_error_307 = http_error_308 = http_error_302


def open_github_probe(request, *, timeout=MAX_PROBE_TIMEOUT):
    """创建本次请求专用opener，不修改全局；HTTP错误也关闭其响应。"""
    _metadata_target(request.full_url)
    if (request.get_method() != "GET" or isinstance(timeout, bool)
            or not isinstance(timeout, (int, float)) or not 0 < timeout <= MAX_PROBE_TIMEOUT):
        raise ValueError("invalid GitHub metadata request")
    redirect = GithubMetadataRedirect(time.monotonic() + timeout)
    opener = urllib.request.build_opener(redirect)
    try:
        return opener.open(request, timeout=timeout)
    except urllib.error.HTTPError as error:
        try:
            error.close()
        except Exception:
            pass  # 清理失败不覆盖原HTTP错误，不输出响应或地址。
        raise