"""
Genesis version compatibility layer.

Provides consistent API across Genesis 0.3.x and 0.4.x:
- detect_collision_parallel: batch collision detection across all envs
- Mesh morph: handles parse_glb_with_zup vs file_meshes_are_zup
"""

import numpy as np
import genesis as gs

_GENESIS_VERSION = tuple(int(x) for x in gs.__version__.split(".")[:3])


def _detect_collision_parallel_impl(
    entity,
    with_entity=None,
    exclude_self_contact=False,
    envs_idx=None,
    unsafe=False,
):
    """
    Batch collision detection across all parallel envs.

    Ported from Genesis 0.3.x RigidEntity.detect_collision_parallel().
    Works with Genesis 0.4.x by accessing the same solver internals.

    Returns:
        numpy.ndarray: bool array of shape (n_envs,) indicating collision.
    """
    if not unsafe:
        entity.solver.collider.clear()
        entity.solver.collider.detection()

    # Pull current contact buffers
    n_collision = entity.solver.collider._collider_state.n_contacts.to_numpy()
    geom_A = entity.solver.collider._collider_state.contact_data.geom_a.to_numpy()
    geom_B = entity.solver.collider._collider_state.contact_data.geom_b.to_numpy()

    n_collision = np.asarray(n_collision).reshape(-1)  # [B]
    geom_A = np.asarray(geom_A)  # [max_contacts, B]
    geom_B = np.asarray(geom_B)  # [max_contacts, B]

    max_contacts, B = geom_A.shape

    if envs_idx is None:
        envs_idx = np.arange(B, dtype=int)
    else:
        envs_idx = np.asarray(envs_idx, dtype=int)

    valid_rows = np.arange(max_contacts)[:, None] < n_collision[None, :]

    selfA = (geom_A >= entity.geom_start) & (geom_A < entity.geom_end)
    selfB = (geom_B >= entity.geom_start) & (geom_B < entity.geom_end)

    if with_entity is not None:
        otherA = (geom_A >= with_entity.geom_start) & (geom_A < with_entity.geom_end)
        otherB = (geom_B >= with_entity.geom_start) & (geom_B < with_entity.geom_end)
        hits = ((selfA & otherB) | (selfB & otherA)) & valid_rows
    else:
        hits = (selfA | selfB) & valid_rows
        if exclude_self_contact:
            hits &= ~(selfA & selfB)

    collided = np.any(hits, axis=0)  # [B]
    return collided[envs_idx]


def patch_entity_compat(entity, n_envs):
    """Add detect_collision_parallel() to entity if missing (Genesis 0.4+)."""
    if hasattr(entity, "detect_collision_parallel"):
        return  # Already has it (Genesis 0.3.x)

    import types

    def detect_collision_parallel(
        with_entity=None, exclude_self_contact=False, envs_idx=None, *, unsafe=False
    ):
        return _detect_collision_parallel_impl(
            entity, with_entity, exclude_self_contact, envs_idx, unsafe=unsafe
        )

    entity.detect_collision_parallel = detect_collision_parallel


def mesh_kwargs_compat(**kwargs):
    """Convert Mesh kwargs for Genesis version compatibility.

    Genesis 0.3.x: GLBs are auto-handled (no flag needed).
    Genesis 0.4.x: Need file_meshes_are_zup=True to match old behavior.
    """
    if _GENESIS_VERSION >= (0, 4, 0):
        # Convert parse_glb_with_zup -> file_meshes_are_zup
        if "parse_glb_with_zup" in kwargs:
            kwargs["file_meshes_are_zup"] = kwargs.pop("parse_glb_with_zup")
    else:
        # 0.3.x: remove both flags (not needed, can break things)
        kwargs.pop("parse_glb_with_zup", None)
        kwargs.pop("file_meshes_are_zup", None)
    return kwargs


def create_mesh_morph(**kwargs):
    """Create gs.morphs.Mesh with version-compatible kwargs."""
    return gs.morphs.Mesh(**mesh_kwargs_compat(**kwargs))