"""Bucket sync: per agent, `<BUCKET>/<swarm>/<type>/<agent>/` holds

    workdir/<path relative to the workdir>        (if persist_workdir)
    sessions/<agent>.jsonl, <agent>.state.json    (pi session log + worker state)
    harness/<path relative to the harness home>   (CLAUDE_CONFIG_DIR or CODEX_HOME)

The workdir goes through `sync_bucket` (the Python form of `hf buckets sync`, as in the
resume-gate experiment), upward with delete so the bucket mirrors the workdir. The handful of
session and harness files go through `batch_bucket_files`, only those whose (mtime, size)
changed since the last push by this worker. `restore` brings all three areas back to the
same absolute paths (workdir and work root are fixed, harness homes are fixed by the image)
before the first resume.
"""

from __future__ import annotations

import asyncio
import logging
import re
import threading
from collections import Counter
from dataclasses import dataclass, field
from pathlib import Path
from typing import TYPE_CHECKING, Protocol

if TYPE_CHECKING:
    from flock.worker.agents import AgentRuntime

log = logging.getLogger(__name__)

UPLOAD_CHUNK = 200


@dataclass
class BucketStats:
    """Bucket traffic counters for the worker log: store operations (`ops`), the Hub HTTP
    requests behind them (`http`, by method and route; xet CAS transfers run in hf_xet and are
    not seen here) and HTTP error statuses (`errors`, e.g. 429). Thread-safe."""

    ops: Counter = field(default_factory=Counter)
    http: Counter = field(default_factory=Counter)
    errors: Counter = field(default_factory=Counter)
    _lock: threading.Lock = field(default_factory=threading.Lock, repr=False)

    def add(self, kind: str, key: str, n: int = 1) -> None:
        with self._lock:
            getattr(self, kind)[key] += n

    def snapshot(self) -> dict[str, Counter]:
        with self._lock:
            return {"ops": Counter(self.ops), "http": Counter(self.http),
                    "errors": Counter(self.errors)}

    def since(self, before: dict[str, Counter]) -> dict[str, dict[str, int]]:
        now = self.snapshot()
        return {k: dict(now[k] - before[k]) for k in now}


_BUCKET_ROUTE = re.compile(r"^/api/buckets/[^/]+/[^/]+(?:/([^/]+))?")


def http_route(method: str, host: str, path: str) -> str:
    """'GET /api/buckets/ns/b/tree/x/y' -> 'GET buckets/tree'; other hosts by first segment."""
    m = _BUCKET_ROUTE.match(path)
    if m:
        return f"{method} buckets/{m.group(1) or ''}".rstrip("/")
    first = path.strip("/").split("/", 1)[0]
    if host.endswith("huggingface.co"):
        return f"{method} {first or '/'}"
    return f"{method} {host}/{first}"


def count_hub_http(stats: BucketStats) -> None:
    """Count every request huggingface_hub's shared client makes (one install per process)."""
    import huggingface_hub
    from huggingface_hub.utils._http import default_client_factory

    def on_request(request) -> None:
        stats.add("http", http_route(request.method, request.url.host, request.url.path))

    def on_response(response) -> None:
        if response.status_code >= 400:
            req = response.request
            route = http_route(req.method, req.url.host, req.url.path)
            stats.add("errors", f"{response.status_code} {route}")

    def factory():
        client = default_client_factory()
        client.event_hooks["request"].append(on_request)
        client.event_hooks.setdefault("response", []).append(on_response)
        return client

    huggingface_hub.set_client_factory(factory)


class BucketStore(Protocol):
    """Blocking bucket operations on paths relative to the flock root."""

    def upload(self, files: list[tuple[Path, str]]) -> None: ...
    def list(self, prefix: str) -> list[str]: ...
    def download(self, files: list[tuple[str, Path]]) -> None: ...
    def sync_up(self, local: Path, prefix: str) -> None:
        """Mirror a local directory to `prefix` (delete remote files missing locally)."""
        ...

    def sync_down(self, prefix: str, local: Path) -> None: ...


def parse_bucket(url: str) -> tuple[str, str]:
    """'hf://buckets/ns/name/some/prefix' -> ('ns/name', 'some/prefix/')."""
    rest = url.removeprefix("hf://").removeprefix("buckets/").strip("/")
    parts = rest.split("/")
    if len(parts) < 2:
        raise ValueError(f"bad bucket url {url!r}; expected hf://buckets/<namespace>/<name>[/prefix]")
    prefix = "/".join(parts[2:])
    return f"{parts[0]}/{parts[1]}", (prefix + "/" if prefix else "")


class HubBucketStore:
    """huggingface_hub bucket API (batch_bucket_files / list_bucket_tree / download_bucket_files)."""

    def __init__(self, url: str, token: str | None = None, stats: BucketStats | None = None) -> None:
        from huggingface_hub import HfApi

        self.bucket_id, self.base = parse_bucket(url)
        self.api = HfApi(token=token)
        self.stats = stats or BucketStats()

    def upload(self, files: list[tuple[Path, str]]) -> None:
        for i in range(0, len(files), UPLOAD_CHUNK):
            self.stats.add("ops", "batch_bucket_files")
            chunk = files[i : i + UPLOAD_CHUNK]
            self.api.batch_bucket_files(self.bucket_id, add=[(str(p), self.base + r) for p, r in chunk])

    def list(self, prefix: str) -> list[str]:
        from huggingface_hub import BucketFile

        self.stats.add("ops", "list_bucket_tree")
        full = self.base + prefix
        out = []
        for f in self.api.list_bucket_tree(self.bucket_id, prefix=full, recursive=True):
            if isinstance(f, BucketFile) and f.path.startswith(full):
                out.append(f.path[len(self.base):])
        return out

    def download(self, files: list[tuple[str, Path]]) -> None:
        self.stats.add("ops", "download_bucket_files")
        for _, local in files:
            local.parent.mkdir(parents=True, exist_ok=True)
        self.api.download_bucket_files(self.bucket_id, [(self.base + r, str(p)) for r, p in files])

    def _url(self, prefix: str) -> str:
        return f"hf://buckets/{self.bucket_id}/{self.base}{prefix}".rstrip("/")

    def sync_up(self, local: Path, prefix: str) -> None:
        self.stats.add("ops", "sync_bucket_up")
        self.api.sync_bucket(str(local), self._url(prefix), delete=True, quiet=True)

    def sync_down(self, prefix: str, local: Path) -> None:
        self.stats.add("ops", "sync_bucket_down")
        local.mkdir(parents=True, exist_ok=True)
        self.api.sync_bucket(self._url(prefix), str(local), quiet=True)


@dataclass
class RestoreResult:
    workdir: int = 0
    sessions: int = 0
    harness: int = 0


class BucketSync:
    def __init__(self, store: BucketStore, swarm: str) -> None:
        self.store = store
        self.swarm = swarm
        self.stats: BucketStats = getattr(store, "stats", None) or BucketStats()
        self._seen: dict[Path, tuple[int, int]] = {}

    def prefix(self, rt: AgentRuntime) -> str:
        return f"{self.swarm}/{rt.type_name}/{rt.name}/"

    def collect(self, rt: AgentRuntime) -> list[tuple[Path, str]]:
        """The agent's session-log, state and harness files, with their bucket paths."""
        pre = self.prefix(rt)
        out: list[tuple[Path, str]] = []
        for p in (rt.log.path, rt.state_path):
            if p.is_file():
                out.append((p, f"{pre}sessions/{p.name}"))
        home = Path(rt.adapter.home)
        for p in rt.harness_files():
            try:
                rel = p.relative_to(home)
            except ValueError:
                log.warning("%s: harness file %s is outside %s; not synced", rt.name, p, home)
                continue
            out.append((p, f"{pre}harness/{rel.as_posix()}"))
        return out

    def _changed(self, files: list[tuple[Path, str]]) -> list[tuple[Path, str]]:
        changed = []
        for p, r in files:
            try:
                st = p.stat()
            except OSError:
                continue
            sig = (st.st_mtime_ns, st.st_size)
            if self._seen.get(p) != sig:
                changed.append((p, r))
        return changed

    def _mark(self, files: list[tuple[Path, str]]) -> None:
        for p, _ in files:
            try:
                st = p.stat()
                self._seen[p] = (st.st_mtime_ns, st.st_size)
            except OSError:
                pass

    async def push(self, rt: AgentRuntime) -> int:
        try:
            return await self._push(rt)
        except Exception:
            self.stats.add("errors", "push_failed")
            raise

    async def _push(self, rt: AgentRuntime) -> int:
        if rt.spec.persist_workdir and rt.workdir.is_dir():
            await asyncio.to_thread(self.store.sync_up, rt.workdir, self.prefix(rt) + "workdir")
        files = self._changed(self.collect(rt))
        if files:
            await asyncio.to_thread(self.store.upload, files)
            self._mark(files)
        return len(files)

    async def restore(self, rt: AgentRuntime) -> RestoreResult:
        try:
            return await self._restore(rt)
        except Exception:
            self.stats.add("errors", "restore_failed")
            raise

    async def _restore(self, rt: AgentRuntime) -> RestoreResult:
        pre = self.prefix(rt)
        remote = await asyncio.to_thread(self.store.list, pre)
        res = RestoreResult()
        plan: list[tuple[str, Path]] = []
        home = Path(rt.adapter.home)
        for r in remote:
            rel = r[len(pre):]
            area, _, sub = rel.partition("/")
            if not sub or ".." in Path(sub).parts:
                continue
            if area == "workdir":
                res.workdir += 1
            elif area == "sessions":
                plan.append((r, rt.sessions_dir / sub))
                res.sessions += 1
            elif area == "harness":
                plan.append((r, home / sub))
                res.harness += 1
        if res.workdir and rt.spec.persist_workdir:
            await asyncio.to_thread(self.store.sync_down, pre + "workdir", rt.workdir)
        if plan:
            await asyncio.to_thread(self.store.download, plan)
            self._mark([(p, r) for r, p in plan])
        log.info("%s: restored %s", rt.name, res)
        return res