"""QQ Bot chunked upload flow.

The QQ v2 API caps inline base64 uploads (``file_data`` / ``url``) at ~10 MB.
Files between 10 MB and ~100 MB use the three-step chunked flow::

    1. POST /v2/{users|groups}/{id}/upload_prepare
       → upload_id, block_size, and pre-signed COS part URLs.
    2. Per part: PUT bytes to the COS URL, then POST .../upload_part_finish.
    3. POST /v2/{users|groups}/{id}/files with {"upload_id": ...}
       → ``file_info`` token used in a RichMedia message.

Error codes (QQ Bot v2 spec): ``40093001`` — ``upload_part_finish`` retryable
until the server's ``retry_timeout`` (or a local cap) elapses; ``40093002`` —
daily upload quota exceeded, surfaced as :class:`UploadDailyLimitExceededError`.
Other API/I/O failures raise ``RuntimeError``.

Ported from WideLee's qqbot-agent-sdk v1.2.2 (``media_loader.py::ChunkedUploader``).
Authorship preserved via Co-authored-by.
"""

from __future__ import annotations

import asyncio
import hashlib
import logging
from dataclasses import dataclass
from pathlib import Path
from typing import Any, Awaitable, Callable, Dict, List

from gateway.platforms.qqbot.constants import FILE_UPLOAD_TIMEOUT

logger = logging.getLogger(__name__)


_BIZ_CODE_DAILY_LIMIT = 40093002     # upload_prepare: daily cumulative limit
_BIZ_CODE_PART_RETRYABLE = 40093001  # upload_part_finish: transient

_DEFAULT_CONCURRENT_PARTS = 1
_MAX_CONCURRENT_PARTS = 10

_PART_UPLOAD_TIMEOUT = 300.0        # 5 minutes per COS PUT
_PART_UPLOAD_MAX_RETRIES = 2
_PART_FINISH_RETRY_INTERVAL = 1.0
_PART_FINISH_DEFAULT_TIMEOUT = 120.0
_PART_FINISH_MAX_TIMEOUT = 600.0

_COMPLETE_UPLOAD_MAX_RETRIES = 2
_COMPLETE_UPLOAD_BASE_DELAY = 2.0

# First 10,002,432 bytes used for the ``md5_10m`` hash (per QQ API spec).
_MD5_10M_SIZE = 10_002_432


# ── Exceptions ───────────────────────────────────────────────────────

class UploadDailyLimitExceededError(Exception):
    """Raised when ``upload_prepare`` returns biz_code 40093002 (daily quota hit)."""

    def __init__(self, file_name: str, file_size: int, message: str = "") -> None:
        self.file_name = file_name
        self.file_size = file_size
        super().__init__(message or f"Daily upload limit exceeded for {file_name!r}")

    @property
    def file_size_human(self) -> str:
        return format_size(self.file_size)


class UploadFileTooLargeError(Exception):
    """Raised when a file exceeds the platform per-file size limit."""

    def __init__(self, file_name: str, file_size: int, limit_bytes: int = 0, message: str = "") -> None:
        self.file_name = file_name
        self.file_size = file_size
        self.limit_bytes = limit_bytes
        limit_str = f" ({format_size(limit_bytes)})" if limit_bytes else ""
        super().__init__(
            message or f"File {file_name!r} ({format_size(file_size)}) exceeds platform limit{limit_str}"
        )

    @property
    def file_size_human(self) -> str:
        return format_size(self.file_size)

    @property
    def limit_human(self) -> str:
        return format_size(self.limit_bytes) if self.limit_bytes else "unknown"


# ── Prepare-response shape ───────────────────────────────────────────

@dataclass
class _PreparePart:
    index: int
    presigned_url: str
    block_size: int = 0


@dataclass
class _PrepareResult:
    upload_id: str
    block_size: int
    parts: List[_PreparePart]
    concurrency: int = _DEFAULT_CONCURRENT_PARTS
    retry_timeout: float = 0.0


def _parse_prepare_response(raw: Dict[str, Any]) -> _PrepareResult:
    """Parse upload_prepare response (either bare or wrapped in ``data``)."""
    src = raw.get("data") if isinstance(raw.get("data"), dict) else raw
    upload_id = str(src.get("upload_id", ""))
    if not upload_id:
        raise ValueError(f"upload_prepare response missing upload_id: {str(raw)[:200]}")
    block_size = int(src.get("block_size", 0))
    raw_parts = src.get("parts") or src.get("part_list") or []
    if not isinstance(raw_parts, list) or not raw_parts:
        raise ValueError(f"upload_prepare response missing parts: {str(raw)[:200]}")
    parts = [
        _PreparePart(
            index=int(p.get("part_index") or p.get("index") or 0),
            presigned_url=str(p.get("presigned_url") or p.get("url") or ""),
            block_size=int(p.get("block_size", 0)),
        )
        for p in raw_parts
        if isinstance(p, dict)
    ]
    return _PrepareResult(
        upload_id=upload_id,
        block_size=block_size,
        parts=parts,
        concurrency=int(src.get("concurrency", _DEFAULT_CONCURRENT_PARTS)) or _DEFAULT_CONCURRENT_PARTS,
        retry_timeout=float(src.get("retry_timeout", 0.0) or 0.0),
    )


def _api_path(chat_type: str, target_id: str, endpoint: str) -> str:
    base = "/v2/users" if chat_type == "c2c" else "/v2/groups"
    return f"{base}/{target_id}/{endpoint}"


# ── Chunked upload driver ────────────────────────────────────────────

class ChunkedUploader:
    """Run the prepare → PUT parts → complete sequence.

    :param api_request: Bound ``_api_request(method, path, body=..., timeout=...)``
        coroutine from the adapter (passed in rather than imported to avoid
        circular imports). Must raise ``RuntimeError`` with the biz_code in
        the message on API errors.
    :param http_put: Coroutine ``(url, data, headers) -> httpx-like response``
        for COS part uploads.
    :param log_tag: Log prefix.
    """

    def __init__(
        self,
        api_request: Callable[..., Awaitable[Dict[str, Any]]],
        http_put: Callable[..., Awaitable[Any]],
        log_tag: str = "QQBot",
    ) -> None:
        self._api_request = api_request
        self._http_put = http_put
        self._log_tag = log_tag

    async def upload(
        self,
        chat_type: str,
        target_id: str,
        file_path: str,
        file_type: int,
        file_name: str,
    ) -> Dict[str, Any]:
        """Run the full chunked upload and return the ``complete_upload`` response.

        :param chat_type: ``'c2c'`` or ``'group'``.
        :param file_type: ``MEDIA_TYPE_*`` constant.
        :returns: Raw ``complete_upload`` response dict (contains ``file_info``).
        :raises UploadDailyLimitExceededError: On biz_code 40093002.
        :raises UploadFileTooLargeError: When the file exceeds the platform limit.
        :raises RuntimeError: On other API or I/O failures.
        """
        if chat_type not in {"c2c", "group"}:
            raise ValueError(f"ChunkedUploader: unsupported chat_type {chat_type!r}")

        file_size = Path(file_path).stat().st_size
        logger.info(
            "[%s] Chunked upload start: file=%s size=%s type=%d",
            self._log_tag, file_name, format_size(file_size), file_type,
        )

        # Hashing is blocking I/O → executor.
        hashes = await asyncio.get_running_loop().run_in_executor(
            None, _compute_file_hashes, file_path, file_size
        )
        prepare = await self._prepare(chat_type, target_id, file_type, file_name, file_size, hashes)
        max_concurrent = min(prepare.concurrency, _MAX_CONCURRENT_PARTS)
        retry_timeout = min(
            prepare.retry_timeout if prepare.retry_timeout > 0 else _PART_FINISH_DEFAULT_TIMEOUT,
            _PART_FINISH_MAX_TIMEOUT,
        )
        logger.info(
            "[%s] Prepared: upload_id=%s block_size=%s parts=%d concurrency=%d",
            self._log_tag, prepare.upload_id, format_size(prepare.block_size),
            len(prepare.parts), max_concurrent,
        )

        total_parts = len(prepare.parts)
        completed = [0]  # shared counter for progress logging
        sem = asyncio.Semaphore(max(max_concurrent, 1))

        async def _run(part: _PreparePart) -> None:
            async with sem:
                await self._upload_one_part(
                    chat_type, target_id, file_path, file_size, prepare.upload_id,
                    prepare.block_size, part, retry_timeout, total_parts, completed,
                )

        await asyncio.gather(*(_run(p) for p in prepare.parts))
        logger.info("[%s] All %d parts uploaded, completing…", self._log_tag, total_parts)
        return await self._complete(chat_type, target_id, prepare.upload_id)

    async def _prepare(
        self,
        chat_type: str,
        target_id: str,
        file_type: int,
        file_name: str,
        file_size: int,
        hashes: Dict[str, str],
    ) -> _PrepareResult:
        body = {
            "file_type": file_type,
            "file_name": file_name,
            "file_size": file_size,
            "md5": hashes["md5"],
            "sha1": hashes["sha1"],
            "md5_10m": hashes["md5_10m"],
        }
        try:
            raw = await self._api_request(
                "POST", _api_path(chat_type, target_id, "upload_prepare"),
                body=body, timeout=FILE_UPLOAD_TIMEOUT,
            )
        except RuntimeError as exc:
            err_msg = str(exc)
            if f"{_BIZ_CODE_DAILY_LIMIT}" in err_msg:
                raise UploadDailyLimitExceededError(file_name, file_size, err_msg) from exc
            raise
        return _parse_prepare_response(raw)

    async def _upload_one_part(
        self,
        chat_type: str,
        target_id: str,
        file_path: str,
        file_size: int,
        upload_id: str,
        rsp_block_size: int,
        part: _PreparePart,
        retry_timeout: float,
        total_parts: int,
        completed: List[int],
    ) -> None:
        """PUT one part to COS, then call ``upload_part_finish``."""
        part_index = part.index
        # Per-part block_size wins; fall back to the response-level value.
        actual_block_size = part.block_size if part.block_size > 0 else rsp_block_size
        offset = (part_index - 1) * rsp_block_size
        length = min(actual_block_size, file_size - offset)

        data = await asyncio.get_running_loop().run_in_executor(
            None, _read_file_chunk, file_path, offset, length
        )
        md5_hex = hashlib.md5(data).hexdigest()
        logger.debug(
            "[%s] Part %d/%d: uploading %s (offset=%d md5=%s)",
            self._log_tag, part_index, total_parts, format_size(length), offset, md5_hex,
        )

        await self._put_to_presigned_url(part.presigned_url, data, part_index, total_parts)
        await self._part_finish_with_retry(
            chat_type, target_id, upload_id, part_index, length, md5_hex, retry_timeout,
        )

        completed[0] += 1
        logger.debug(
            "[%s] Part %d/%d done (%d/%d total)",
            self._log_tag, part_index, total_parts, completed[0], total_parts,
        )

    async def _with_retries(
        self,
        attempt_fn: Callable[[], Awaitable[Any]],
        *,
        max_retries: int,
        base_delay: float,
        label: str,
        failure_label: str,
    ) -> Any:
        """Run *attempt_fn* up to ``max_retries + 1`` times with exponential backoff."""
        last_exc: Exception | None = None
        for attempt in range(max_retries + 1):
            try:
                return await attempt_fn()
            except Exception as exc:
                last_exc = exc
                if attempt < max_retries:
                    delay = base_delay * (2 ** attempt)
                    logger.warning(
                        "[%s] %s attempt %d failed, retry in %.1fs: %s",
                        self._log_tag, label, attempt + 1, delay, exc,
                    )
                    await asyncio.sleep(delay)
        raise RuntimeError(f"{failure_label} failed after {max_retries + 1} attempts: {last_exc}")

    async def _put_to_presigned_url(self, url: str, data: bytes, part_index: int, total_parts: int) -> None:
        """PUT part data to a pre-signed COS URL with retry."""

        async def _attempt() -> None:
            resp = await asyncio.wait_for(
                self._http_put(url, data=data, headers={"Content-Length": str(len(data))}),
                timeout=_PART_UPLOAD_TIMEOUT,
            )
            status = getattr(resp, "status_code", 0)
            if 200 <= status < 300:
                logger.debug("[%s] PUT part %d/%d: %d OK", self._log_tag, part_index, total_parts, status)
                return
            body_preview = ""
            try:
                body_preview = getattr(resp, "text", "")[:200]
            except Exception:  # pragma: no cover — defensive
                pass
            raise RuntimeError(f"COS PUT returned {status}: {body_preview}")

        await self._with_retries(
            _attempt, max_retries=_PART_UPLOAD_MAX_RETRIES, base_delay=1.0,
            label=f"PUT part {part_index}/{total_parts}",
            failure_label=f"Part {part_index}/{total_parts} upload",
        )

    async def _part_finish_with_retry(
        self,
        chat_type: str,
        target_id: str,
        upload_id: str,
        part_index: int,
        block_size: int,
        md5: str,
        retry_timeout: float,
    ) -> None:
        """Call ``upload_part_finish``, retrying on biz_code 40093001 until *retry_timeout*."""
        path = _api_path(chat_type, target_id, "upload_part_finish")
        body = {"upload_id": upload_id, "part_index": part_index, "block_size": block_size, "md5": md5}
        loop = asyncio.get_running_loop()
        start = loop.time()
        attempt = 0
        while True:
            try:
                await self._api_request("POST", path, body=body, timeout=FILE_UPLOAD_TIMEOUT)
                return
            except RuntimeError as exc:
                if f"{_BIZ_CODE_PART_RETRYABLE}" not in str(exc):
                    raise
                elapsed = loop.time() - start
                if elapsed >= retry_timeout:
                    raise RuntimeError(
                        f"upload_part_finish persistent retry timed out "
                        f"after {retry_timeout:.0f}s ({attempt} retries): {exc}"
                    ) from exc
                attempt += 1
                logger.debug(
                    "[%s] part_finish retryable error, attempt %d, elapsed=%.1fs: %s",
                    self._log_tag, attempt, elapsed, exc,
                )
                await asyncio.sleep(_PART_FINISH_RETRY_INTERVAL)

    async def _complete(self, chat_type: str, target_id: str, upload_id: str) -> Dict[str, Any]:
        """Call ``complete_upload`` with retry.

        Reuses the ``/files`` endpoint (same as the simple URL-based upload) but
        signals the chunked-completion path by sending only ``upload_id``.
        """
        path = _api_path(chat_type, target_id, "files")
        body = {"upload_id": upload_id}
        return await self._with_retries(
            lambda: self._api_request("POST", path, body=body, timeout=FILE_UPLOAD_TIMEOUT),
            max_retries=_COMPLETE_UPLOAD_MAX_RETRIES, base_delay=_COMPLETE_UPLOAD_BASE_DELAY,
            label="complete_upload", failure_label="complete_upload",
        )


# ── Helpers (module-level for testability) ───────────────────────────

def format_size(size_bytes: int) -> str:
    """Return a human-readable file size string (e.g. ``'12.3 MB'``)."""
    size = float(size_bytes)
    for unit in ("B", "KB", "MB", "GB"):
        if size < 1024.0:
            return f"{size:.1f} {unit}"
        size /= 1024.0
    return f"{size:.1f} TB"


def _read_file_chunk(file_path: str, offset: int, length: int) -> bytes:
    """Read *length* bytes at *offset*; raises IOError on a short read (truncated file)."""
    with open(file_path, "rb") as fh:
        fh.seek(offset)
        data = fh.read(length)
        if len(data) != length:
            raise IOError(
                f"Short read from {file_path}: expected {length} bytes at "
                f"offset {offset}, got {len(data)} (file may be truncated)"
            )
        return data


def _compute_file_hashes(file_path: str, file_size: int) -> Dict[str, str]:
    """Compute md5, sha1, and md5_10m in a single pass."""
    md5 = hashlib.md5()
    sha1 = hashlib.sha1()
    md5_10m = hashlib.md5()
    need_10m = file_size > _MD5_10M_SIZE
    bytes_read = 0
    with open(file_path, "rb") as fh:
        while chunk := fh.read(65536):
            md5.update(chunk)
            sha1.update(chunk)
            if need_10m:
                remaining = _MD5_10M_SIZE - bytes_read
                if remaining > 0:
                    md5_10m.update(chunk[:remaining])
            bytes_read += len(chunk)
    full_md5 = md5.hexdigest()
    return {
        "md5": full_md5,
        "sha1": sha1.hexdigest(),
        # For small files the "10m" hash is just the full md5.
        "md5_10m": md5_10m.hexdigest() if need_10m else full_md5,
    }