"""pi CLI 后端 — 调用 pi 子进程生成总结。

通用工具函数（prompt 构建、PDF 提取、JSON 提取、meta.json）已移至 summary_utils.py。
"""

from __future__ import annotations

import asyncio
import logging
import uuid
from pathlib import Path

from app.config import settings
from app.utils import truncate_error
from app.services.summary_utils import (
    JsonNotFoundError,
    build_prompt,
    extract_json,
    extract_pdf_text,
    write_meta_json,
)

logger = logging.getLogger(__name__)

# PDF 全文注入模式的字符上限 — 超过此阈值自动切换到 search 模式
_PDF_MAX_CHARS = 80_000

# 重新导出，保持向后兼容
__all__ = [
    "PiTimeoutError",
    "PiProcessError",
    "JsonNotFoundError",
    "call_pi",
    "write_meta_json",
    "extract_pdf_text",
    "build_prompt",
    "extract_json",
]


# ── 自定义异常 ──────────────────────────────────────────────────────────


class PiTimeoutError(Exception):
    pass


class PiProcessError(Exception):
    def __init__(self, returncode: int, stderr: str):
        self.returncode = returncode
        self.stderr = stderr
        super().__init__(f"pi exited with code {returncode}: {truncate_error(stderr)}")


# ── pi CLI 调用 ────────────────────────────────────────────────────────


async def call_pi(
    meta_path: Path,
    pdf_path: Path,
    fix_errors: list[str] | None = None,
    session_id: str | None = None,
    pdf_mode: str = "inject",
) -> tuple[str, str]:
    """调用 pi CLI 非交互模式，返回 (stdout 文本, session_id)。

    fix_errors: 如果非空，表示上一次验证失败的错误列表，pi 需要修正这些问题。
    session_id: 如果非空，用 --continue 延续该 session；否则创建新 session。
    pdf_mode: "inject" = 全量注入 prompt（@file），"search" = pi 自主 read 文件。
    """
    arxiv_id = meta_path.parent.name

    # 提取 PDF 全文（不截断），根据实际大小自动选择模式
    txt_path = extract_pdf_text(pdf_path, max_chars=None)
    txt_size = len(txt_path.read_text(encoding="utf-8"))

    actual_mode = pdf_mode
    if pdf_mode == "auto":
        if txt_size > _PDF_MAX_CHARS:
            actual_mode = "search"
            logger.info(
                "Auto mode: %s text=%d chars > %dk → search",
                arxiv_id,
                txt_size,
                _PDF_MAX_CHARS // 1000,
            )
        else:
            actual_mode = "inject"
            logger.info(
                "Auto mode: %s text=%d chars ≤ %dk → inject",
                arxiv_id,
                txt_size,
                _PDF_MAX_CHARS // 1000,
            )

    # inject 模式需要截断过长的文本（避免撑爆 context）
    if actual_mode == "inject" and txt_size > _PDF_MAX_CHARS:
        body = txt_path.read_text(encoding="utf-8")
        trimmed = body[:_PDF_MAX_CHARS].rstrip()
        txt_path.write_text(trimmed, encoding="utf-8")
        logger.info(
            "Truncated %s for inject: %d → %d chars", arxiv_id, txt_size, len(trimmed)
        )

    prompt_text = build_prompt(arxiv_id, meta_path, txt_path, actual_mode, fix_errors)

    # 构建 session ID（每篇论文一个独立 session）
    if session_id is None:
        session_id = f"summary-{arxiv_id}-{uuid.uuid4().hex[:8]}"

    # 工具列表：search 模式需要 read 工具
    tools = "bash,write_file" if actual_mode != "search" else "bash,write_file,read"
    cmd = [
        settings.PI_BIN,
        "-p",
        "--tools",
        tools,
    ]
    if fix_errors:
        cmd += ["--session", session_id, "--continue"]
    else:
        cmd += ["--session-id", session_id]
    cmd += [
        "--skill",
        settings.SUMMARY_SKILL,
        prompt_text,
    ]
    if not fix_errors and actual_mode != "search":
        # inject 模式：首次调用传 @file；search 模式 pi 自己 read，不注入
        cmd += [f"@{meta_path}", f"@{txt_path}"]

    logger.info(
        "Calling pi for %s (fix=%s, session=%s, mode=%s)",
        arxiv_id,
        bool(fix_errors),
        session_id,
        actual_mode,
    )

    import time as _time

    _t_sub_start = _time.monotonic()

    proc = await asyncio.create_subprocess_exec(
        *cmd,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE,
    )
    try:
        stdout, stderr = await asyncio.wait_for(
            proc.communicate(),
            timeout=settings.SUMMARY_TIMEOUT_SECONDS,
        )
    except asyncio.TimeoutError:
        proc.kill()
        await proc.wait()
        raise PiTimeoutError(f"pi timed out after {settings.SUMMARY_TIMEOUT_SECONDS}s")

    _t_sub_end = _time.monotonic()

    # 检查 summary.json 是否由 pi 子进程写入
    _summary_file = pdf_path.parent / "summary.json"
    _file_info = ""
    if _summary_file.exists():
        _file_mtime = _summary_file.stat().st_mtime
        _file_size = _summary_file.stat().st_size
        _file_info = f"  summary.json={_file_size}B"

    logger.info(
        "pi subprocess for %s: %.2fs%s",
        arxiv_id,
        _t_sub_end - _t_sub_start,
        _file_info,
    )

    if proc.returncode != 0:
        raise PiProcessError(proc.returncode, stderr.decode("utf-8", errors="replace"))

    return stdout.decode("utf-8", errors="replace"), session_id