"""Locate the bundled DeepSeek Harness SDK runtime shipped with this package.

Two runtime carriers coexist under ``runtime/``, both injected by the repo's
``scripts/build-exe-for-python-sdk.ts`` build (neither is checked into git):

- **exe (production)**: single-file executables named
  ``dsh-jsonrpc-agent-pkg-<platform>-<arch>`` (platform in {linux, macos}, arch in
  {x64, arm64}); the target machine needs no Node installation.
- **node (dev-only)**: the full deploy closure under ``runtime/node/``
  (``package.json`` + ``node_modules/``), executed as ``node
  runtime/node/node_modules/@deepseek-ai/dsh-jsonrpc-demo/lib/bin.js`` on a
  system Node >= 22.19. It is the current checkout's source build, never
  selected automatically, and excluded from wheel/sdist distributions.

``runtime/cordis.yml`` IS checked in: it is the default agent configuration
the client SDK injects via ``$DSH_CORDIS_CONFIG`` for zero-config runs — the
runtime itself always requires an explicit config and has no built-in
fallback.
"""

from __future__ import annotations

import os
import platform
import shutil
import sys
from pathlib import Path

PACKAGE_METADATA_FILENAME = "deepseek-harness-runtime.json"

RUNTIME_MODE_ENV_VAR = "DSH_RUNTIME_MODE"

_PLATFORM_TAGS = {"linux": "linux", "darwin": "macos"}
_ARCH_TAGS = {"x86_64": "x64", "amd64": "x64", "arm64": "arm64", "aarch64": "arm64"}

_EXE_ACQUISITION_HINT = (
    "Two ways to get the executable: run `scripts/build-exe-for-python-sdk.ts` (via tsx) in a "
    "deepseek-harness checkout, or install the matching `deepseek-harness-runtime-bin` platform "
    "wheel retained by the `build-exe-for-python-sdk` CI workflow. For local development "
    "against a repo source build, explicitly select the dev-only node carrier with "
    f"{RUNTIME_MODE_ENV_VAR}=node (or resolve_bundled_launch_args('node'))."
)


def bundled_package_dir() -> Path:
    """Root directory of the installed runtime package data (the directory of this module)."""
    root = Path(__file__).resolve().parent
    metadata = root / PACKAGE_METADATA_FILENAME
    if not metadata.is_file():
        raise FileNotFoundError(f"deepseek-harness-runtime-bin is missing {metadata}")
    return root


def bundled_default_config_path() -> Path:
    """Path of the checked-in default runtime configuration (``runtime/cordis.yml``).

    The client SDK injects this path via ``$DSH_CORDIS_CONFIG`` when the caller
    supplies no config and the launch resolves to the bundled runtime — the
    runtime binary itself always demands an explicit config.
    """
    path = bundled_package_dir() / "runtime" / "cordis.yml"
    if not path.is_file():
        raise FileNotFoundError(
            f"deepseek-harness-runtime-bin is missing the default runtime config at {path}"
        )
    return path


def bundled_runtime_path() -> Path:
    """Absolute path of the bundled single-file runtime executable for the current platform.

    Raises FileNotFoundError when the platform is unsupported or the executable
    has not been placed into this package; the message names the acquisition
    routes (acquisition strategy is deliberately separate from this lookup
    interface, so an on-demand download can replace it without touching
    callers).
    """
    tag = _current_platform_tag()
    path = bundled_package_dir() / "runtime" / f"dsh-jsonrpc-agent-pkg-{tag}"
    if not path.is_file():
        raise FileNotFoundError(
            f"deepseek-harness-runtime-bin is missing the runtime executable at {path}. "
            + _EXE_ACQUISITION_HINT
        )
    return path


def resolve_bundled_launch_args(mode: str | None = None) -> tuple[str, ...]:
    """The argv tuple that launches the bundled runtime.

    Mode selection: the explicit ``mode`` argument wins, then the
    ``DSH_RUNTIME_MODE`` environment variable (``exe`` | ``node``), then
    automatic resolution. Automatic resolution finds the production exe ONLY —
    the dev-only node carrier must be selected explicitly so a production
    deployment can never silently ride on a source build. Returns
    ``(exe_path,)`` in exe mode and ``(node_path, bin_js_path)`` in node mode;
    raises FileNotFoundError when the selected carrier is unavailable and
    ValueError for an unknown mode value.
    """
    selected = mode if mode is not None else os.environ.get(RUNTIME_MODE_ENV_VAR)
    if selected is None or selected == "exe":
        return (str(bundled_runtime_path()),)
    if selected == "node":
        return _node_launch_args()
    raise ValueError(
        f"unsupported DeepSeek Harness runtime mode {selected!r}: expected 'exe' or 'node' "
        f"(explicit argument or ${RUNTIME_MODE_ENV_VAR})"
    )


def _current_platform_tag() -> str:
    plat = _PLATFORM_TAGS.get(sys.platform)
    arch = _ARCH_TAGS.get(platform.machine().lower())
    if plat is None or arch is None:
        raise FileNotFoundError(
            "no bundled dsh-jsonrpc-agent executable exists for this platform "
            f"(sys.platform={sys.platform!r}, machine={platform.machine()!r}); supported: "
            "linux/macos on x64/arm64. " + _EXE_ACQUISITION_HINT
        )
    return f"{plat}-{arch}"


def _node_launch_args() -> tuple[str, str]:
    node_root = bundled_package_dir() / "runtime" / "node"
    bin_js = (
        node_root / "node_modules" / "@deepseek-ai" / "dsh-jsonrpc-demo" / "lib" / "bin.js"
    )
    if not bin_js.is_file():
        raise FileNotFoundError(
            f"the dev-only node runtime closure is missing at {node_root} "
            f"(no {bin_js}); run `scripts/build-exe-for-python-sdk.ts` in a deepseek-harness "
            "checkout, which builds and copies the deploy closure here. The node carrier "
            "is for repo-local development only — production uses the single-file exe."
        )
    node = shutil.which("node")
    if node is None:
        raise FileNotFoundError(
            "the node runtime mode needs a system `node` (>=22.19) on PATH; "
            "install Node.js or use the exe mode"
        )
    return (node, str(bin_js))


__all__ = [
    "PACKAGE_METADATA_FILENAME",
    "RUNTIME_MODE_ENV_VAR",
    "bundled_default_config_path",
    "bundled_package_dir",
    "bundled_runtime_path",
    "resolve_bundled_launch_args",
]
