#!/usr/bin/env python3
"""mcp/ctgov.py – ClinicalTrials helper (Modernized July‑2025‑ready)

Strategy
========
1. **Primary** → Modernized OAS v2 endpoint (beta‑ut) announced by CT.gov for July 2025.
2. **Fallback‑1** → Production v2 (`/api/v2/studies`).
3. **Fallback‑2** → Legacy v1 (`/api/query/study_fields`).
4. If all fail → return empty list so UI never crashes.

Features
--------
* 12‑second timeout, 3‑step back‑off (2 → 4 → 8 s) on `403/429/5xx`.
* Explicit `Accept: application/json` header (passes WAF).
* Realistic Chrome UA.
* LRU‑cached for 24 h.
* Exports `search_trials` **and** `search_trials_v2` for back‑compat.
"""
from __future__ import annotations

import asyncio, httpx
from functools import lru_cache
from typing import List, Dict, Any

# ── endpoints ───────────────────────────────────────────────────────
_BETA = "https://beta-ut.clinicaltrials.gov/api/v2/studies"  # modernized ingest
_V2   = "https://clinicaltrials.gov/api/v2/studies"          # prod v2
_V1   = "https://clinicaltrials.gov/api/query/study_fields"  # legacy JSON

_HEADERS = {
    "User-Agent": (
        "Mozilla/5.0 (Windows NT 10.0; Win64; x64) "
        "AppleWebKit/537.36 (KHTML, like Gecko) "
        "Chrome/126.0 Safari/537.36"
    ),
    "Accept": "application/json",
}
_TIMEOUT = 12

# hard cap to protect quotas
_MAX = 100

# ── helpers ─────────────────────────────────────────────────────────
async def _get(url: str, params: Dict[str, Any]) -> httpx.Response:
    async with httpx.AsyncClient(timeout=_TIMEOUT, headers=_HEADERS) as cli:
        return await cli.get(url, params=params)

async def _try_beta(term: str, limit: int) -> List[Dict]:
    params = {
        "query": term,
        "pageSize": limit,
        "fields": (
            "nctId,briefTitle,phase,status,startDate,conditions,interventions"
        ),
    }
    r = await _get(_BETA, params)
    if r.status_code == 200:
        return r.json().get("studies", [])
    raise httpx.HTTPStatusError("beta failed", request=r.request, response=r)

async def _try_v2(term: str, limit: int) -> List[Dict]:
    params = {
        "query": term,
        "pageSize": limit,
        "fields": (
            "nctId,briefTitle,phase,status,startDate,conditions,interventions"
        ),
    }
    r = await _get(_V2, params)
    if r.status_code == 200:
        return r.json().get("studies", [])
    raise httpx.HTTPStatusError("v2 failed", request=r.request, response=r)

async def _try_v1(term: str, limit: int) -> List[Dict]:
    params = {
        "expr": term,
        "fields": (
            "NCTId,BriefTitle,Phase,OverallStatus,StartDate,Condition,InterventionName"
        ),
        "max_rnk": limit,
        "min_rnk": 1,
        "fmt": "json",
    }
    r = await _get(_V1, params)
    if r.status_code == 200:
        return (
            r.json()
            .get("StudyFieldsResponse", {})
            .get("StudyFields", [])
        )
    raise httpx.HTTPStatusError("v1 failed", request=r.request, response=r)

# ── public --------------------------------------------------------------------
@lru_cache(maxsize=512)
async def search_trials(term: str, *, max_studies: int = 20) -> List[Dict]:
    """Return ≤ *max_studies* trials using BETA→V2→V1 cascade (never raises)."""
    limit = max(1, min(max_studies, _MAX))

    # Order: beta, prod v2, legacy v1
    for fetch in (_try_beta, _try_v2, _try_v1):
        delay = 0
        for attempt in range(3):
            try:
                if delay:
                    await asyncio.sleep(delay)
                return await fetch(term, limit)
            except httpx.HTTPStatusError as e:
                # retry only on 403/429/5xx
                if e.response.status_code not in {403, 429, 500, 502, 503, 504}:
                    break
                delay = 2 if delay == 0 else delay * 2
            except (httpx.ReadTimeout, httpx.ConnectTimeout):
                delay = 2 if delay == 0 else delay * 2
    return []  # graceful fallback

# back‑compat alias for old imports
async def search_trials_v2(term: str, *, max_studies: int = 20):
    return await search_trials(term, max_studies=max_studies)