import asyncio
import hashlib
import json
import re
from typing import List, Optional, Dict, Any
from urllib.parse import urlparse, unquote

import httpx
from fastapi import FastAPI, HTTPException, Query, Body
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel, Field, field_validator
from pydantic_settings import BaseSettings

# =========================
# Settings
# =========================
class Settings(BaseSettings):
    ZOTERO_API_KEY: str
    ZOTERO_DEFAULT_GROUP_ID: Optional[str] = None
    ZOTERO_API_VERSION: str = "3"
    HTTP_TIMEOUT_SECONDS: float = 20.0
    MAX_RETRIES: int = 4
    CORS_ALLOW_ORIGINS: str = "*"   # comma-separated or "*"

    class Config:
        case_sensitive = True

settings = Settings()

# =========================
# Models
# =========================
class Creator(BaseModel):
    creatorType: str = Field("author", examples=["author", "editor"])
    firstName: str = ""
    lastName: str

class Tag(BaseModel):
    tag: str

class ItemModel(BaseModel):
    """
    Canonical Zotero item payload.
      - conferencePaper uses 'proceedingsTitle'
      - journalArticle uses 'publicationTitle'
    """
    itemType: str = Field(..., examples=["journalArticle", "conferencePaper"])
    title: str
    creators: List[Creator] = []

    # Titles
    publicationTitle: Optional[str] = None      # journalArticle
    proceedingsTitle: Optional[str] = None      # conferencePaper
    conferenceName: Optional[str] = None

    abstractNote: Optional[str] = None
    date: Optional[str] = None
    pages: Optional[str] = None
    url: Optional[str] = None

    # common extras we’ll map from BibTeX
    volume: Optional[str] = None
    issue: Optional[str] = None                 # BibTeX 'number'
    publisher: Optional[str] = None
    place: Optional[str] = None                 # BibTeX 'address'
    series: Optional[str] = None
    DOI: Optional[str] = None
    ISBN: Optional[str] = None

    tags: List[Tag] = []
    collections: List[str] = []
    extra: Optional[str] = None
    relations: Dict[str, Any] = {}

class CreateRequest(BaseModel):
    """
    Public/ingress model. Accepts friendly aliases + raw BibTeX.
    """
    groupId: Optional[str] = None
    writeToken: Optional[str] = None
    item: Optional[ItemModel] = None

    # Friendly fields
    title: Optional[str] = None
    authors: Optional[str] = None
    editors: Optional[str] = None
    itemType: Optional[str] = None

    # Titles (aliases)
    publicationTitle: Optional[str] = None
    proceedingsTitle: Optional[str] = None
    bookTitle: Optional[str] = None             # alias → proceedingsTitle
    conferenceName: Optional[str] = None

    date: Optional[str] = None
    pages: Optional[str] = None
    url: Optional[str] = None
    abstractNote: Optional[str] = None
    tags: Optional[List[str]] = None
    collections: Optional[List[str]] = None

    # extra scholarly fields
    volume: Optional[str] = None
    issue: Optional[str] = None
    publisher: Optional[str] = None
    place: Optional[str] = None
    series: Optional[str] = None
    DOI: Optional[str] = None
    ISBN: Optional[str] = None

    # Optional raw BibTeX
    bibtex: Optional[str] = None

    @field_validator("groupId", mode="before")
    @classmethod
    def default_group(cls, v: Optional[str]) -> Optional[str]:
        return v or settings.ZOTERO_DEFAULT_GROUP_ID

# =========================
# Helpers
# =========================
AUTHOR_SPLIT_RE = re.compile(r"\s*(?:;| and )\s*", re.IGNORECASE)

def parse_people(s: Optional[str], creator_type: str = "author") -> List[Creator]:
    if not s:
        return []
    people = []
    for part in AUTHOR_SPLIT_RE.split(s.strip()):
        if not part:
            continue
        if "," in part:
            last, first = [p.strip() for p in part.split(",", 1)]
        else:
            bits = part.strip().split()
            if len(bits) == 1:
                last, first = bits[0], ""
            else:
                last, first = bits[-1], " ".join(bits[:-1])
        people.append(Creator(creatorType=creator_type, firstName=first, lastName=last))
    return people

def _bt_get(bib: str, name: str) -> Optional[str]:
    mm = re.search(rf"{name}\s*=\s*\{{([^}}]+)\}}", bib, re.IGNORECASE)
    if mm:
        return mm.group(1).strip()
    # also support quotes "..."
    mm = re.search(rf"{name}\s*=\s*\"([^\"]+)\"", bib, re.IGNORECASE)
    return mm.group(1).strip() if mm else None

def parse_bibtex(bib: str) -> Dict[str, Any]:
    """
    Very light BibTeX parsing.
    """
    out: Dict[str, str] = {}
    m = re.search(r"@\s*(\w+)\s*\{", bib)
    if m:
        out["itemType"] = {
            "article": "journalArticle",
            "inproceedings": "conferencePaper",
            "proceedings": "conferencePaper",
            "book": "book",
        }.get(m.group(1).lower(), m.group(1))

    out["title"] = _bt_get(bib, "title")
    out["authors"] = _bt_get(bib, "author")
    out["editors"] = _bt_get(bib, "editor")
    out["publicationTitle"] = _bt_get(bib, "journal")
    out["proceedingsTitle"] = _bt_get(bib, "booktitle")
    out["pages"] = _bt_get(bib, "pages")
    out["date"] = _bt_get(bib, "year")
    out["url"] = _bt_get(bib, "url")
    out["abstractNote"] = _bt_get(bib, "abstract")

    # extras
    out["series"] = _bt_get(bib, "series")
    out["volume"] = _bt_get(bib, "volume")
    out["issue"] = _bt_get(bib, "number")
    out["publisher"] = _bt_get(bib, "publisher")
    out["place"] = _bt_get(bib, "address")
    out["DOI"] = _bt_get(bib, "doi")
    out["ISBN"] = _bt_get(bib, "isbn")

    return {k: v for k, v in out.items() if v}

def normalize_titles_for_type(item: Dict[str, Any]) -> None:
    """
    Normalize title fields based on itemType.
    """
    itype = (item.get("itemType") or "").lower()

    if itype == "conferencepaper":
        if not item.get("proceedingsTitle"):
            if item.get("bookTitle"):
                item["proceedingsTitle"] = item.pop("bookTitle")
            elif item.get("publicationTitle"):
                item["proceedingsTitle"] = item["publicationTitle"]
        item.pop("bookTitle", None)
        item.pop("publicationTitle", None)

    elif itype == "journalarticle":
        # prefer publicationTitle; drop conference fields
        item.pop("proceedingsTitle", None)
        item.pop("bookTitle", None)

    else:
        # Coalesce: if publicationTitle missing, reuse proceedingsTitle
        if not item.get("publicationTitle") and item.get("proceedingsTitle"):
            item["publicationTitle"] = item.pop("proceedingsTitle")
        item.pop("bookTitle", None)

def guess_title_from_url(u: Optional[str]) -> Optional[str]:
    if not u:
        return None
    try:
        p = urlparse(u)
        if not p.path:
            return None
        parts = [seg for seg in p.path.split("/") if seg]
        if not parts:
            return None
        last = parts[-1]
        # strip extension
        if "." in last:
            last = last.rsplit(".", 1)[0]
        text = unquote(last)
        text = re.sub(r"[-_]+", " ", text).strip()
        if not text:
            return None
        return text[:1].upper() + text[1:]
    except Exception:
        return None

def merge_request_to_item(req: CreateRequest) -> ItemModel:
    """
    Merge precedence:
      1) req.item (canonical)
      2) parsed bibtex (fills missing)
      3) friendly fields on req (override/add)
      4) normalize titles
      5) ensure title (fallback from URL slug if still missing)
    """
    item: Dict[str, Any] = json.loads(req.item.json()) if req.item else {}

    # (2) From BibTeX
    if req.bibtex:
        bt = parse_bibtex(req.bibtex)
        item.setdefault("itemType", bt.get("itemType"))
        for k in [
            "title", "publicationTitle", "proceedingsTitle", "conferenceName",
            "pages", "date", "url", "abstractNote", "series", "volume", "issue",
            "publisher", "place", "DOI", "ISBN"
        ]:
            if bt.get(k) and not item.get(k):
                item[k] = bt[k]
        # creators
        if bt.get("authors") and "creators" not in item:
            item["creators"] = parse_people(bt["authors"], "author")
        if bt.get("editors"):
            item.setdefault("creators", [])
            item["creators"].extend(parse_people(bt["editors"], "editor"))

    # (3) Friendly fields (override/add)
    if req.itemType: item["itemType"] = req.itemType
    if req.title: item["title"] = req.title
    if req.publicationTitle: item["publicationTitle"] = req.publicationTitle
    if req.proceedingsTitle: item["proceedingsTitle"] = req.proceedingsTitle
    if req.bookTitle: item["bookTitle"] = req.bookTitle
    if req.conferenceName: item["conferenceName"] = req.conferenceName
    if req.pages: item["pages"] = req.pages
    if req.date: item["date"] = req.date
    if req.url: item["url"] = req.url
    if req.abstractNote: item["abstractNote"] = req.abstractNote

    # extras
    if req.volume: item["volume"] = req.volume
    if req.issue: item["issue"] = req.issue
    if req.publisher: item["publisher"] = req.publisher
    if req.place: item["place"] = req.place
    if req.series: item["series"] = req.series
    if req.DOI: item["DOI"] = req.DOI
    if req.ISBN: item["ISBN"] = req.ISBN

    # creators (authors/editors text)
    creators: List[Creator] = []
    if req.authors: creators.extend(parse_people(req.authors, "author"))
    if req.editors: creators.extend(parse_people(req.editors, "editor"))
    if creators: item["creators"] = creators

    # tags/collections
    if req.tags is not None:
        item["tags"] = [Tag(tag=t) for t in req.tags]
    if req.collections is not None:
        item["collections"] = req.collections

    # (4) Normalize titles by type
    normalize_titles_for_type(item)

    # (5) Ensure title: fallback from URL slug if still missing
    if not item.get("title"):
        t = guess_title_from_url(item.get("url"))
        if t:
            item["title"] = t

    # Final validation
    try:
        return ItemModel(**item)
    except Exception as e:
        raise HTTPException(status_code=422, detail=f"Invalid item payload: {e}")

def default_write_token(item: ItemModel) -> str:
    base = f"{item.itemType}|{item.title}|{item.date or ''}"
    return hashlib.sha256(base.encode("utf-8")).hexdigest()[:32]

async def zotero_post_items(group_id: str, items: List[ItemModel], write_token: str) -> Dict[str, Any]:
    url = f"https://api.zotero.org/groups/{group_id}/items"
    headers = {
        "Zotero-API-Key": settings.ZOTERO_API_KEY,
        "Zotero-API-Version": settings.ZOTERO_API_VERSION,
        "Content-Type": "application/json",
        "Accept": "application/json",
        "Zotero-Write-Token": write_token,
    }
    data = [json.loads(i.json(exclude_none=True)) for i in items]

    timeout = httpx.Timeout(settings.HTTP_TIMEOUT_SECONDS)
    attempt = 0
    last_exc: Optional[Exception] = None

    async with httpx.AsyncClient(timeout=timeout) as client:
        while attempt <= settings.MAX_RETRIES:
            try:
                resp = await client.post(url, headers=headers, json=data)
                if resp.status_code in (200, 201, 204):
                    return {"status": resp.status_code, "zotero": resp.json() if resp.text else {}}
                if resp.status_code in (429, 500, 502, 503, 504):
                    retry_after = 0
                    ra = resp.headers.get("Retry-After")
                    if ra:
                        try:
                            retry_after = int(ra)
                        except ValueError:
                            retry_after = 0
                    delay = max(retry_after, 2 ** attempt)
                    attempt += 1
                    await asyncio.sleep(delay)
                    continue
                raise HTTPException(status_code=resp.status_code, detail=resp.text)
            except httpx.HTTPError as e:
                last_exc = e
                attempt += 1
                await asyncio.sleep(2 ** (attempt - 1))
                continue
    raise HTTPException(status_code=502, detail=f"Upstream Zotero error or timeout: {last_exc}")

# =========================
# FastAPI app
# =========================
app = FastAPI(title="Zotero Proxy", version="1.2.0")

allow_origins = ["*"] if settings.CORS_ALLOW_ORIGINS.strip() == "*" else [
    o.strip() for o in settings.CORS_ALLOW_ORIGINS.split(",") if o.strip()
]
app.add_middleware(
    CORSMiddleware,
    allow_origins=allow_origins,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

@app.get("/ping")
async def ping():
    return {"ok": True}

@app.post("/items")
async def create_item(req: CreateRequest = Body(...)):
    group_id = req.groupId or settings.ZOTERO_DEFAULT_GROUP_ID
    if not group_id:
        raise HTTPException(status_code=400, detail="groupId is required (or set ZOTERO_DEFAULT_GROUP_ID).")
    item = merge_request_to_item(req)
    # If still no title after all fallbacks, fail clearly:
    if not item.title:
        raise HTTPException(status_code=422, detail="Missing 'title'. Provide it directly, via BibTeX, or a URL I can slug.")
    write_token = req.writeToken or default_write_token(item)
    result = await zotero_post_items(group_id, [item], write_token)
    return {"groupId": group_id, "writeToken": write_token, **result}

@app.get("/items")
async def create_item_from_query(
    groupId: Optional[str] = Query(None),
    title: Optional[str] = Query(None),
    authors: Optional[str] = Query(None),
    editors: Optional[str] = Query(None),
    itemType: Optional[str] = Query(None),

    # Titles
    publicationTitle: Optional[str] = Query(None),
    proceedingsTitle: Optional[str] = Query(None),
    bookTitle: Optional[str] = Query(None),
    conferenceName: Optional[str] = Query(None),

    date: Optional[str] = Query(None),
    pages: Optional[str] = Query(None),
    url: Optional[str] = Query(None),
    abstractNote: Optional[str] = Query(None),
    tags: Optional[str] = Query(None),          # comma-separated
    collections: Optional[str] = Query(None),   # comma-separated

    # extras
    volume: Optional[str] = Query(None),
    issue: Optional[str] = Query(None),
    publisher: Optional[str] = Query(None),
    place: Optional[str] = Query(None),
    series: Optional[str] = Query(None),
    DOI: Optional[str] = Query(None),
    ISBN: Optional[str] = Query(None),

    writeToken: Optional[str] = Query(None),
    bibtex: Optional[str] = Query(None),
):
    req = CreateRequest(
        groupId=groupId or settings.ZOTERO_DEFAULT_GROUP_ID,
        writeToken=writeToken,
        title=title,
        authors=authors,
        editors=editors,
        itemType=itemType,
        publicationTitle=publicationTitle,
        proceedingsTitle=proceedingsTitle,
        bookTitle=bookTitle,
        conferenceName=conferenceName,
        date=date,
        pages=pages,
        url=url,
        abstractNote=abstractNote,
        tags=[t.strip() for t in tags.split(",")] if tags else None,
        collections=[c.strip() for c in collections.split(",")] if collections else None,
        volume=volume,
        issue=issue,
        publisher=publisher,
        place=place,
        series=series,
        DOI=DOI,
        ISBN=ISBN,
        bibtex=bibtex,
    )
    return await create_item(req)