"""OpenAI-compatible shim that forwards Hermes requests to `copilot --acp`.

This adapter lets Hermes treat the GitHub Copilot ACP server as a chat-style
backend. Each request starts a short-lived ACP session, sends the formatted
conversation as a single prompt, collects text chunks, and converts the result
back into the minimal shape Hermes expects from an OpenAI client.
"""

from __future__ import annotations

import json
import os
import queue
import shlex
import subprocess
import threading
import time
from collections import deque
from pathlib import Path
from types import SimpleNamespace
from typing import Any

ACP_MARKER_BASE_URL = "acp://copilot"
_DEFAULT_TIMEOUT_SECONDS = 900.0


def _resolve_command() -> str:
    return (
        os.getenv("HERMES_COPILOT_ACP_COMMAND", "").strip()
        or os.getenv("COPILOT_CLI_PATH", "").strip()
        or "copilot"
    )


def _resolve_args() -> list[str]:
    raw = os.getenv("HERMES_COPILOT_ACP_ARGS", "").strip()
    if not raw:
        return ["--acp", "--stdio"]
    return shlex.split(raw)


def _jsonrpc_error(message_id: Any, code: int, message: str) -> dict[str, Any]:
    return {
        "jsonrpc": "2.0",
        "id": message_id,
        "error": {
            "code": code,
            "message": message,
        },
    }


def _format_messages_as_prompt(messages: list[dict[str, Any]], model: str | None = None) -> str:
    sections: list[str] = [
        "You are being used as the active ACP agent backend for Hermes.",
        "Use your own ACP capabilities and respond directly in natural language.",
        "Do not emit OpenAI tool-call JSON.",
    ]
    if model:
        sections.append(f"Hermes requested model hint: {model}")

    transcript: list[str] = []
    for message in messages:
        if not isinstance(message, dict):
            continue
        role = str(message.get("role") or "unknown").strip().lower()
        if role == "tool":
            role = "tool"
        elif role not in {"system", "user", "assistant"}:
            role = "context"

        content = message.get("content")
        rendered = _render_message_content(content)
        if not rendered:
            continue

        label = {
            "system": "System",
            "user": "User",
            "assistant": "Assistant",
            "tool": "Tool",
            "context": "Context",
        }.get(role, role.title())
        transcript.append(f"{label}:\n{rendered}")

    if transcript:
        sections.append("Conversation transcript:\n\n" + "\n\n".join(transcript))

    sections.append("Continue the conversation from the latest user request.")
    return "\n\n".join(section.strip() for section in sections if section and section.strip())


def _render_message_content(content: Any) -> str:
    if content is None:
        return ""
    if isinstance(content, str):
        return content.strip()
    if isinstance(content, dict):
        if "text" in content:
            return str(content.get("text") or "").strip()
        if "content" in content and isinstance(content.get("content"), str):
            return str(content.get("content") or "").strip()
        return json.dumps(content, ensure_ascii=True)
    if isinstance(content, list):
        parts: list[str] = []
        for item in content:
            if isinstance(item, str):
                parts.append(item)
            elif isinstance(item, dict):
                text = item.get("text")
                if isinstance(text, str) and text.strip():
                    parts.append(text.strip())
        return "\n".join(parts).strip()
    return str(content).strip()


def _ensure_path_within_cwd(path_text: str, cwd: str) -> Path:
    candidate = Path(path_text)
    if not candidate.is_absolute():
        raise PermissionError("ACP file-system paths must be absolute.")
    resolved = candidate.resolve()
    root = Path(cwd).resolve()
    try:
        resolved.relative_to(root)
    except ValueError as exc:
        raise PermissionError(f"Path '{resolved}' is outside the session cwd '{root}'.") from exc
    return resolved


class _ACPChatCompletions:
    def __init__(self, client: "CopilotACPClient"):
        self._client = client

    def create(self, **kwargs: Any) -> Any:
        return self._client._create_chat_completion(**kwargs)


class _ACPChatNamespace:
    def __init__(self, client: "CopilotACPClient"):
        self.completions = _ACPChatCompletions(client)


class CopilotACPClient:
    """Minimal OpenAI-client-compatible facade for Copilot ACP."""

    def __init__(
        self,
        *,
        api_key: str | None = None,
        base_url: str | None = None,
        default_headers: dict[str, str] | None = None,
        acp_command: str | None = None,
        acp_args: list[str] | None = None,
        acp_cwd: str | None = None,
        command: str | None = None,
        args: list[str] | None = None,
        **_: Any,
    ):
        self.api_key = api_key or "copilot-acp"
        self.base_url = base_url or ACP_MARKER_BASE_URL
        self._default_headers = dict(default_headers or {})
        self._acp_command = acp_command or command or _resolve_command()
        self._acp_args = list(acp_args or args or _resolve_args())
        self._acp_cwd = str(Path(acp_cwd or os.getcwd()).resolve())
        self.chat = _ACPChatNamespace(self)
        self.is_closed = False
        self._active_process: subprocess.Popen[str] | None = None
        self._active_process_lock = threading.Lock()

    def close(self) -> None:
        proc: subprocess.Popen[str] | None
        with self._active_process_lock:
            proc = self._active_process
            self._active_process = None
        self.is_closed = True
        if proc is None:
            return
        try:
            proc.terminate()
            proc.wait(timeout=2)
        except Exception:
            try:
                proc.kill()
            except Exception:
                pass

    def _create_chat_completion(
        self,
        *,
        model: str | None = None,
        messages: list[dict[str, Any]] | None = None,
        timeout: float | None = None,
        **_: Any,
    ) -> Any:
        prompt_text = _format_messages_as_prompt(messages or [], model=model)
        response_text, reasoning_text = self._run_prompt(
            prompt_text,
            timeout_seconds=float(timeout or _DEFAULT_TIMEOUT_SECONDS),
        )

        usage = SimpleNamespace(
            prompt_tokens=0,
            completion_tokens=0,
            total_tokens=0,
            prompt_tokens_details=SimpleNamespace(cached_tokens=0),
        )
        assistant_message = SimpleNamespace(
            content=response_text,
            tool_calls=[],
            reasoning=reasoning_text or None,
            reasoning_content=reasoning_text or None,
            reasoning_details=None,
        )
        choice = SimpleNamespace(message=assistant_message, finish_reason="stop")
        return SimpleNamespace(
            choices=[choice],
            usage=usage,
            model=model or "copilot-acp",
        )

    def _run_prompt(self, prompt_text: str, *, timeout_seconds: float) -> tuple[str, str]:
        try:
            proc = subprocess.Popen(
                [self._acp_command] + self._acp_args,
                stdin=subprocess.PIPE,
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE,
                text=True,
                bufsize=1,
                cwd=self._acp_cwd,
            )
        except FileNotFoundError as exc:
            raise RuntimeError(
                f"Could not start Copilot ACP command '{self._acp_command}'. "
                "Install GitHub Copilot CLI or set HERMES_COPILOT_ACP_COMMAND/COPILOT_CLI_PATH."
            ) from exc

        if proc.stdin is None or proc.stdout is None:
            proc.kill()
            raise RuntimeError("Copilot ACP process did not expose stdin/stdout pipes.")

        self.is_closed = False
        with self._active_process_lock:
            self._active_process = proc

        inbox: queue.Queue[dict[str, Any]] = queue.Queue()
        stderr_tail: deque[str] = deque(maxlen=40)

        def _stdout_reader() -> None:
            for line in proc.stdout:
                try:
                    inbox.put(json.loads(line))
                except Exception:
                    inbox.put({"raw": line.rstrip("\n")})

        def _stderr_reader() -> None:
            if proc.stderr is None:
                return
            for line in proc.stderr:
                stderr_tail.append(line.rstrip("\n"))

        out_thread = threading.Thread(target=_stdout_reader, daemon=True)
        err_thread = threading.Thread(target=_stderr_reader, daemon=True)
        out_thread.start()
        err_thread.start()

        next_id = 0

        def _request(method: str, params: dict[str, Any], *, text_parts: list[str] | None = None, reasoning_parts: list[str] | None = None) -> Any:
            nonlocal next_id
            next_id += 1
            request_id = next_id
            payload = {
                "jsonrpc": "2.0",
                "id": request_id,
                "method": method,
                "params": params,
            }
            proc.stdin.write(json.dumps(payload) + "\n")
            proc.stdin.flush()

            deadline = time.time() + timeout_seconds
            while time.time() < deadline:
                if proc.poll() is not None:
                    break
                try:
                    msg = inbox.get(timeout=0.1)
                except queue.Empty:
                    continue

                if self._handle_server_message(
                    msg,
                    process=proc,
                    cwd=self._acp_cwd,
                    text_parts=text_parts,
                    reasoning_parts=reasoning_parts,
                ):
                    continue

                if msg.get("id") != request_id:
                    continue
                if "error" in msg:
                    err = msg.get("error") or {}
                    raise RuntimeError(
                        f"Copilot ACP {method} failed: {err.get('message') or err}"
                    )
                return msg.get("result")

            stderr_text = "\n".join(stderr_tail).strip()
            if proc.poll() is not None and stderr_text:
                raise RuntimeError(f"Copilot ACP process exited early: {stderr_text}")
            raise TimeoutError(f"Timed out waiting for Copilot ACP response to {method}.")

        try:
            _request(
                "initialize",
                {
                    "protocolVersion": 1,
                    "clientCapabilities": {
                        "fs": {
                            "readTextFile": True,
                            "writeTextFile": True,
                        }
                    },
                    "clientInfo": {
                        "name": "hermes-agent",
                        "title": "Hermes Agent",
                        "version": "0.0.0",
                    },
                },
            )
            session = _request(
                "session/new",
                {
                    "cwd": self._acp_cwd,
                    "mcpServers": [],
                },
            ) or {}
            session_id = str(session.get("sessionId") or "").strip()
            if not session_id:
                raise RuntimeError("Copilot ACP did not return a sessionId.")

            text_parts: list[str] = []
            reasoning_parts: list[str] = []
            _request(
                "session/prompt",
                {
                    "sessionId": session_id,
                    "prompt": [
                        {
                            "type": "text",
                            "text": prompt_text,
                        }
                    ],
                },
                text_parts=text_parts,
                reasoning_parts=reasoning_parts,
            )
            return "".join(text_parts), "".join(reasoning_parts)
        finally:
            self.close()

    def _handle_server_message(
        self,
        msg: dict[str, Any],
        *,
        process: subprocess.Popen[str],
        cwd: str,
        text_parts: list[str] | None,
        reasoning_parts: list[str] | None,
    ) -> bool:
        method = msg.get("method")
        if not isinstance(method, str):
            return False

        if method == "session/update":
            params = msg.get("params") or {}
            update = params.get("update") or {}
            kind = str(update.get("sessionUpdate") or "").strip()
            content = update.get("content") or {}
            chunk_text = ""
            if isinstance(content, dict):
                chunk_text = str(content.get("text") or "")
            if kind == "agent_message_chunk" and chunk_text and text_parts is not None:
                text_parts.append(chunk_text)
            elif kind == "agent_thought_chunk" and chunk_text and reasoning_parts is not None:
                reasoning_parts.append(chunk_text)
            return True

        if process.stdin is None:
            return True

        message_id = msg.get("id")
        params = msg.get("params") or {}

        if method == "session/request_permission":
            response = {
                "jsonrpc": "2.0",
                "id": message_id,
                "result": {
                    "outcome": {
                        "outcome": "allow_once",
                    }
                },
            }
        elif method == "fs/read_text_file":
            try:
                path = _ensure_path_within_cwd(str(params.get("path") or ""), cwd)
                content = path.read_text() if path.exists() else ""
                line = params.get("line")
                limit = params.get("limit")
                if isinstance(line, int) and line > 1:
                    lines = content.splitlines(keepends=True)
                    start = line - 1
                    end = start + limit if isinstance(limit, int) and limit > 0 else None
                    content = "".join(lines[start:end])
                response = {
                    "jsonrpc": "2.0",
                    "id": message_id,
                    "result": {
                        "content": content,
                    },
                }
            except Exception as exc:
                response = _jsonrpc_error(message_id, -32602, str(exc))
        elif method == "fs/write_text_file":
            try:
                path = _ensure_path_within_cwd(str(params.get("path") or ""), cwd)
                path.parent.mkdir(parents=True, exist_ok=True)
                path.write_text(str(params.get("content") or ""))
                response = {
                    "jsonrpc": "2.0",
                    "id": message_id,
                    "result": None,
                }
            except Exception as exc:
                response = _jsonrpc_error(message_id, -32602, str(exc))
        else:
            response = _jsonrpc_error(
                message_id,
                -32601,
                f"ACP client method '{method}' is not supported by Hermes yet.",
            )

        process.stdin.write(json.dumps(response) + "\n")
        process.stdin.flush()
        return True