#!/usr/bin/env python3
from __future__ import annotations

import argparse
import os
import re
import shutil
import subprocess
from datetime import datetime, timezone
from pathlib import Path

RUNTIME_ROOT = Path("{{RUNTIME_ROOT}}")


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description="Generate a backtrace for a Metin runtime core file")
    parser.add_argument("--core", help="Core file path. Defaults to the newest core under the runtime tree.")
    parser.add_argument("--exe", help="Executable path override. If omitted, infer it from the core path.")
    return parser.parse_args()


def ensure_root() -> None:
    if os.geteuid() != 0:
        raise SystemExit("Run as root.")


def run(command: list[str], check: bool = False) -> subprocess.CompletedProcess[str]:
    return subprocess.run(command, check=check, capture_output=True, text=True)


def iter_core_files() -> list[Path]:
    return sorted(
        (path for path in RUNTIME_ROOT.glob("channels/**/core*") if path.is_file()),
        key=lambda path: path.stat().st_mtime,
        reverse=True,
    )


def resolve_core_path(core_arg: str | None) -> Path:
    if core_arg:
        candidate = Path(core_arg)
        if not candidate.is_absolute():
            runtime_relative = RUNTIME_ROOT / core_arg
            if runtime_relative.exists():
                candidate = runtime_relative
        candidate = candidate.resolve()
        if not candidate.is_file():
            raise SystemExit(f"Core file not found: {candidate}")
        return candidate

    cores = iter_core_files()
    if not cores:
        raise SystemExit(f"No core files found under {RUNTIME_ROOT}")
    return cores[0]


def infer_execfn_from_file_output(core_path: Path) -> Path | None:
    completed = run(["file", str(core_path)])
    if completed.returncode != 0:
        return None

    match = re.search(r"execfn: '([^']+)'", completed.stdout)
    if not match:
        return None

    candidate = Path(match.group(1))
    if candidate.is_file():
        return candidate
    return None


def infer_executable(core_path: Path, exe_arg: str | None) -> Path:
    if exe_arg:
        exe_path = Path(exe_arg).resolve()
        if not exe_path.is_file():
            raise SystemExit(f"Executable not found: {exe_path}")
        return exe_path

    execfn_candidate = infer_execfn_from_file_output(core_path)

    parent_name = core_path.parent.name
    grandparent_name = core_path.parent.parent.name if core_path.parent.parent else ""

    candidates: list[Path] = []
    if execfn_candidate:
        candidates.append(execfn_candidate)

    if parent_name == "db":
        candidates.append(core_path.parent / "db")
    elif parent_name == "auth":
        candidates.append(core_path.parent / "game_auth")
    elif parent_name.startswith("core") and grandparent_name.startswith("channel"):
        candidates.append(core_path.parent / f"{grandparent_name}_{parent_name}")

    for candidate in candidates:
        if candidate.is_file():
            return candidate.resolve()

    raise SystemExit(f"Could not infer executable for core file: {core_path}")


def preferred_debugger() -> str | None:
    for tool in ("gdb", "lldb"):
        if shutil.which(tool):
            return tool
    return None


def format_section(title: str, body: str) -> str:
    return f"== {title} ==\n{body.rstrip()}\n"


def render_file_info(path: Path) -> str:
    completed = run(["file", str(path)])
    body = completed.stdout or completed.stderr or "<no output>"
    return format_section(f"file {path}", body)


def render_executable_freshness(core_path: Path, exe_path: Path) -> str:
    core_stat = core_path.stat()
    exe_stat = exe_path.stat()
    core_mtime = datetime.fromtimestamp(core_stat.st_mtime, tz=timezone.utc).isoformat()
    exe_mtime = datetime.fromtimestamp(exe_stat.st_mtime, tz=timezone.utc).isoformat()

    lines = [
        f"core_mtime: {core_mtime}",
        f"exe_mtime: {exe_mtime}",
    ]

    if exe_stat.st_mtime > core_stat.st_mtime + 1:
        lines.append(
            "warning: executable is newer than the core file; symbols may not match. "
            "Prefer an executable snapshot from an incident bundle or pass --exe explicitly."
        )
    else:
        lines.append("status: executable is not newer than the core file")

    return format_section("core/executable freshness", "\n".join(lines))


def render_readelf_notes(core_path: Path) -> str:
    if not shutil.which("readelf"):
        return ""
    completed = run(["readelf", "-n", str(core_path)])
    body = completed.stdout or completed.stderr or "<no output>"
    return format_section(f"readelf -n {core_path}", body)


def render_debugger_backtrace(debugger: str, exe_path: Path, core_path: Path) -> str:
    if debugger == "gdb":
        command = [
            "gdb",
            "-batch",
            "-ex",
            "set pagination off",
            "-ex",
            "thread apply all bt full",
            str(exe_path),
            str(core_path),
        ]
    elif debugger == "lldb":
        command = [
            "lldb",
            "--batch",
            "-o",
            "thread backtrace all",
            "-c",
            str(core_path),
            str(exe_path),
        ]
    else:
        raise SystemExit(f"Unsupported debugger: {debugger}")

    completed = run(command)
    output = completed.stdout or completed.stderr or "<no output>"
    return format_section("backtrace", f"$ {' '.join(command)}\n\n{output}")


def main() -> int:
    args = parse_args()
    ensure_root()

    core_path = resolve_core_path(args.core)
    exe_path = infer_executable(core_path, args.exe)
    debugger = preferred_debugger()

    sections = [
        format_section(
            "summary",
            "\n".join(
                [
                    f"core: {core_path}",
                    f"executable: {exe_path}",
                    f"debugger: {debugger or '<none>'}",
                ]
            ),
        ),
        render_file_info(core_path),
        render_file_info(exe_path),
        render_executable_freshness(core_path, exe_path),
    ]

    readelf_section = render_readelf_notes(core_path)
    if readelf_section:
        sections.append(readelf_section)

    if debugger:
        sections.append(render_debugger_backtrace(debugger, exe_path, core_path))
    else:
        sections.append(
            format_section(
                "backtrace",
                "No supported debugger found. Install gdb or lldb on the host to generate a stack trace.",
            )
        )

    print("\n".join(section.rstrip() for section in sections if section).rstrip())
    return 0


if __name__ == "__main__":
    raise SystemExit(main())