"""CRUD API for roundtable-planning business chains (业务链条).

A business chain is a named, reusable, *ordered* list of agents the user
assembles in the chain editor. In Step 2 the coordinator dispatches to the seats
following this order. Bound to the requesting user (not the browser), so it
follows the account across devices/sessions — same model as roundtable drafts.

Routes (prefix ``/api/roundtable-chains``):
    GET    ""               list current user's chains (full records, incl. seats)
    POST   ""               create a chain
    GET    "/{chain_id}"    one chain
    PUT    "/{chain_id}"    partial update (title / description / seats)
    DELETE "/{chain_id}"    delete
"""

from __future__ import annotations

import logging
from datetime import datetime
from uuid import uuid4

from fastapi import APIRouter, HTTPException, Request
from pydantic import BaseModel, Field

from deerflow.runtime.user_context import get_effective_user_id

logger = logging.getLogger(__name__)
router = APIRouter(prefix="/api/roundtable-chains", tags=["roundtable-chains"])

# Seat-count bounds mirror the roundtable selection bounds (2 ≤ N ≤ 8).
MIN_SEATS = 2
MAX_SEATS = 8


# ── schemas ────────────────────────────────────────────────────────────────


class ChainSeatSchema(BaseModel):
    agent_id: str = Field(min_length=1, max_length=128)
    name: str = ""
    description: str = ""


class ChainResponse(BaseModel):
    id: str
    title: str = ""
    description: str | None = None
    seats: list[ChainSeatSchema] = []
    created_at: datetime | str | None = None
    updated_at: datetime | str | None = None


class ChainListResponse(BaseModel):
    chains: list[ChainResponse]


class ChainCreateRequest(BaseModel):
    # Optional client-provided id so the browser can keep one stable id across
    # the create + subsequent updates without an extra round-trip.
    id: str | None = Field(default=None, max_length=64)
    title: str = Field(default="", max_length=512)
    description: str | None = Field(default=None, max_length=2048)
    seats: list[ChainSeatSchema] = []


class ChainUpdateRequest(BaseModel):
    # All optional → callers send only what changed.
    title: str | None = Field(default=None, max_length=512)
    description: str | None = Field(default=None, max_length=2048)
    seats: list[ChainSeatSchema] | None = None


# ── helpers ──────────────────────────────────────────────────────────────


def _current_user_id(request: Request) -> str:
    user = getattr(request.state, "user", None)
    if user is not None:
        return str(user.id)
    return get_effective_user_id()


def _get_store(request: Request):
    store = getattr(request.app.state, "roundtable_chain_store", None)
    if store is None:
        raise HTTPException(status_code=503, detail="Roundtable chain store not available")
    return store


def _validate_seats(seats: list[ChainSeatSchema]) -> None:
    """Enforce 2 ≤ N ≤ 8 and reject duplicate agent ids within a chain."""
    if len(seats) < MIN_SEATS or len(seats) > MAX_SEATS:
        raise HTTPException(
            status_code=400,
            detail=f"业务链条席位数须在 {MIN_SEATS}–{MAX_SEATS} 之间（当前 {len(seats)}）",
        )
    seen: set[str] = set()
    for s in seats:
        if s.agent_id in seen:
            raise HTTPException(status_code=400, detail=f"业务链条存在重复智能体: {s.agent_id}")
        seen.add(s.agent_id)


# ── routes ───────────────────────────────────────────────────────────────


@router.get("", response_model=ChainListResponse)
async def list_chains(request: Request) -> ChainListResponse:
    store = _get_store(request)
    user_id = _current_user_id(request)
    rows = await store.list_chains(user_id)
    return ChainListResponse(chains=[ChainResponse(**r) for r in rows])


@router.post("", response_model=ChainResponse, status_code=201)
async def create_chain(request: Request, body: ChainCreateRequest) -> ChainResponse:
    _validate_seats(body.seats)
    store = _get_store(request)
    user_id = _current_user_id(request)
    row = await store.create_chain(
        user_id,
        {
            "id": (body.id or uuid4().hex),
            "title": body.title.strip(),
            "description": body.description,
            "seats": [s.model_dump() for s in body.seats],
        },
    )
    return ChainResponse(**row)


@router.get("/{chain_id}", response_model=ChainResponse)
async def get_chain(request: Request, chain_id: str) -> ChainResponse:
    store = _get_store(request)
    user_id = _current_user_id(request)
    row = await store.get_chain(chain_id, user_id)
    if row is None:
        raise HTTPException(status_code=404, detail="Chain not found")
    return ChainResponse(**row)


@router.put("/{chain_id}", response_model=ChainResponse)
async def update_chain(request: Request, chain_id: str, body: ChainUpdateRequest) -> ChainResponse:
    if body.seats is not None:
        _validate_seats(body.seats)
    store = _get_store(request)
    user_id = _current_user_id(request)
    # Distinguish "omitted" from "explicitly sent"; only forward provided fields.
    fields = body.model_dump(exclude_unset=True)
    row = await store.update_chain(chain_id, user_id, **fields)
    if row is None:
        raise HTTPException(status_code=404, detail="Chain not found")
    return ChainResponse(**row)


@router.delete("/{chain_id}", status_code=204)
async def delete_chain(request: Request, chain_id: str) -> None:
    store = _get_store(request)
    user_id = _current_user_id(request)
    deleted = await store.delete_chain(chain_id, user_id)
    if not deleted:
        raise HTTPException(status_code=404, detail="Chain not found")