"""Repo read intern — pack repo with repomix, answer question with LLM."""

from __future__ import annotations

import os
import shutil
import subprocess
import tempfile
from pathlib import Path
from typing import Any

from .base import BudgetExceededError, Intern, InternResponse
from ..safety import always_ask_globs


# Conservative token estimate: chars/4 overestimates for repomix XML (tag overhead),
# so BudgetExceededError fires early rather than late. Real enforcement is on the
# endpoint side — this is a client-side safety net, not a precision counter.
CHARS_PER_TOKEN = 4


def _estimate_tokens(text: str) -> int:
    return len(text) // CHARS_PER_TOKEN


def _top_files_by_size(packed: str, n: int = 5) -> list[str]:
    """Return the n largest files in repomix XML output, by block content size.

    Parses each ``<file path="X">...</file>`` block and measures the byte length
    of its content, so BudgetExceededError.top_files points the user at the real
    overflow culprits — not the first files in document order.
    """
    sizes: list[tuple[int, str]] = []
    pos = 0
    while True:
        open_idx = packed.find('<file ', pos)
        if open_idx == -1:
            break
        close_idx = packed.find('</file>', open_idx)
        if close_idx == -1:
            break
        path_start = packed.find('path="', open_idx) + 6
        path_end = packed.find('"', path_start)
        path = packed[path_start:path_end]
        # Content sits between the opening tag's '>' and the closing '</file>'.
        content_start = packed.find('>', open_idx) + 1
        content_size = close_idx - content_start
        sizes.append((content_size, path))
        pos = close_idx + len('</file>')

    sizes.sort(key=lambda x: x[0], reverse=True)
    return [path for _, path in sizes[:n]]


class RepoRead(Intern):
    id = "repo_read"
    description = "Pack directory/repo with repomix and answer a question. Cheap repo comprehension."

    def run(
        self,
        paths: list[str],
        question: str,
        compress: bool = False,
        **kwargs: Any,
    ) -> InternResponse | BudgetExceededError:
        if not paths:
            return InternResponse(text="No paths provided", usage={})

        # Build repomix args: pass all paths, not just first.
        ignore_globs = always_ask_globs()

        # Resolve npx via PATH. On Windows, subprocess.run(shell=False) does not
        # expand PATHEXT, so passing bare "npx" fails to find npx.cmd; shutil.which
        # finds the .cmd (or .exe / shell wrapper on POSIX) and returns a full path
        # that CreateProcess / execve can dispatch directly.
        npx = shutil.which("npx") or shutil.which("npx.cmd")
        if npx is None:
            return InternResponse(text="npx not found - install Node.js", usage={})

        # Use mkstemp to avoid Windows file-sharing issues with NamedTemporaryFile.
        # os.close(fd) releases the handle before repomix writes to the path.
        fd, tmp_path = tempfile.mkstemp(suffix=".xml")
        os.close(fd)
        err_fd, err_path = tempfile.mkstemp(suffix=".stderr")
        os.close(err_fd)
        try:
            args = [
                npx, "-y", "repomix@latest",
                *paths,
                "--output", tmp_path,
                "--style", "xml",
            ]
            if compress:
                args.append("--compress")
            for glob in ignore_globs:
                args += ["--ignore", glob]

            try:
                # Redirect repomix's stdio to FILES/DEVNULL, never PIPES. capture_output
                # spawns reader threads that communicate() joins; if any process in the
                # child tree (an orphaned `node` grandchild, or — under concurrent launches
                # on Windows — a sibling subprocess that inherited the pipe handle) keeps a
                # pipe write-end open, that join blocks FOREVER, past the timeout, wedging
                # the worker thread. repomix's real output already goes to --output, so its
                # stdout is unused; stderr is captured to a file for error reporting only.
                with open(err_path, "w", encoding="utf-8", errors="replace") as err_f:
                    subprocess.run(
                        args,
                        stdin=subprocess.DEVNULL,
                        stdout=subprocess.DEVNULL,
                        stderr=err_f,
                        timeout=120,
                        check=True,
                    )
                packed_text = Path(tmp_path).read_text()
            except subprocess.TimeoutExpired:
                return InternResponse(text="Repomix timed out (120s)", usage={})
            except subprocess.CalledProcessError:
                err = Path(err_path).read_text(encoding="utf-8", errors="replace")
                return InternResponse(text=f"Repomix failed: {err[:500]}", usage={})
            except FileNotFoundError:
                return InternResponse(text="npx not found - install Node.js", usage={})
        finally:
            # Always clean up the temp files, even on error.
            for _p in (tmp_path, err_path):
                try:
                    os.unlink(_p)
                except OSError:
                    pass

        # Budget check before sending to LLM.
        tokens = _estimate_tokens(packed_text)
        if tokens > self.context_budget:
            return BudgetExceededError(
                tokens=tokens,
                limit=self.context_budget,
                top_files=_top_files_by_size(packed_text),
            )

        prompt = f"# Packed repo\n\n{packed_text}\n\n# Question\n\n{question}"

        if self.client is None:
            return InternResponse(text="No client configured", usage={})

        extra_body = kwargs.get("extra_body", {})
        resp = self.client.chat.completions.create(
            model=self.model or "deepseek-v4-flash",
            messages=[
                {"role": "system", "content": self.system_prompt},
                {"role": "user", "content": prompt},
            ],
            max_tokens=kwargs.get("max_tokens", self.max_tokens),
            temperature=self.temperature,
            extra_body=extra_body if extra_body else None,
        )

        choice = resp.choices[0]
        return InternResponse(
            text=choice.message.content or "",
            usage={
                "tokens_in": resp.usage.prompt_tokens if resp.usage else 0,
                "tokens_out": resp.usage.completion_tokens if resp.usage else 0,
            },
        )