import os
import pickle
import orbax.checkpoint
from flax.training import orbax_utils
import jax
import jax.numpy as jnp
import numpy as np
from orbax.checkpoint import ArrayRestoreArgs, RestoreArgs

# suppress logging from orbax 
import logging
logger = logging.getLogger("absl")
logger.setLevel(logging.ERROR)

# compute path to repo root by using this file's path
REPO_PATH = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))

def save_train_run(out, savedir, savename):
    '''Save train run as orbax checkpoint. 
    Orbax requires absolute paths, so we compute the absolute path to the repo root.'''
    # determine whether savedir is relative or absolute
    if not os.path.isabs(savedir):
        savedir = os.path.join(REPO_PATH, savedir)
    if not os.path.exists(savedir):
        os.makedirs(savedir, exist_ok=True)
    savepath = os.path.join(savedir, savename)
    
    checkpointer = orbax.checkpoint.PyTreeCheckpointer()
    save_args = orbax_utils.save_args_from_target(out)
    
    # Save the checkpoint
    checkpointer.save(savepath, out, save_args=save_args)
    return savepath

def load_checkpoints(path, ckpt_key="checkpoints", custom_loader_cfg: dict=None):
    '''Load checkpoints from orbax checkpoint.
    Orbax requires absolute paths, so we compute the absolute path to the repo root.'''
    if custom_loader_cfg is None:
        restored = load_train_run(path)
        return restored[ckpt_key]
    elif custom_loader_cfg["name"] == "open_ended":
        # Open-ended loader needs the full checkpoint
        restored = load_train_run(path)
        partner_out, ego_out = restored
        out = ego_out if custom_loader_cfg["type"] == "ego" else partner_out
        if ckpt_key == "final_buffer":
            return out["final_buffer"]["params"]
        else:
            return out[ckpt_key]
    elif custom_loader_cfg["name"] == "partial_load":
        return _load_partial(path, ckpt_key)
    elif custom_loader_cfg["name"] == "fcp":
        # FCP saves checkpoints with shape
        #   (NUM_SEEDS, PARTNER_POP_SIZE, NUM_CHECKPOINTS, ...)
        # Reshape to the (NUM_SEEDS, FCP_POP_SIZE, ...) layout that
        # AgentPopulation expects, where FCP_POP_SIZE = PARTNER_POP_SIZE *
        # NUM_CHECKPOINTS. Mirrors get_fcp_population in
        # teammate_generation/fcp.py so a saved FCP run can be reused as a
        # partner pool by ego_agent_training/run.py.
        restored = load_train_run(path)
        ckpts = restored[ckpt_key]
        return jax.tree.map(
            lambda x: x.reshape(x.shape[0], x.shape[1] * x.shape[2], *x.shape[3:]),
            ckpts,
        )
    else:
        raise ValueError(f"Invalid custom loader name: {custom_loader_cfg['name']}")

def _load_partial(path, ckpt_key):
    '''Load only a single top-level key from an orbax checkpoint, avoiding OOM
    from loading the entire pytree (e.g. skipping metrics).'''
    if not os.path.isabs(path):
        path = os.path.join(REPO_PATH, path)

    checkpointer = orbax.checkpoint.PyTreeCheckpointer()
    cpu_sharding = jax.sharding.SingleDeviceSharding(jax.devices('cpu')[0])
    meta = checkpointer.metadata(path)

    if ckpt_key not in meta:
        raise KeyError(f"Key '{ckpt_key}' not found in checkpoint. Available keys: {list(meta.keys())}")

    subtree_meta = meta[ckpt_key]
    item = {ckpt_key: jax.tree.map(
        lambda m: np.empty(m.shape, dtype=m.dtype) if hasattr(m, 'shape') else m,
        subtree_meta,
    )}
    transforms = {ckpt_key: orbax.checkpoint.Transform()}
    restore_args = {ckpt_key: jax.tree.map(
        lambda _: orbax.checkpoint.ArrayRestoreArgs(sharding=cpu_sharding),
        subtree_meta,
    )}

    restored = checkpointer.restore(path, item=item, transforms=transforms, restore_args=restore_args)
    return restored[ckpt_key]

def load_train_run(path):
    '''Load checkpoints from orbax checkpoint. 
    Orbax requires absolute paths, so we compute the absolute path to the repo root.'''
    # determine whether path is relative or absolute
    if not os.path.isabs(path):
        path = os.path.join(REPO_PATH, path)
    # load the checkpoint
    checkpointer = orbax.checkpoint.PyTreeCheckpointer()
    def _restore_with_numpy_args():
        metadata = checkpointer.metadata(path)

        def _mk_restore_args(leaf):
            if hasattr(leaf, "shape") and hasattr(leaf, "dtype"):
                return ArrayRestoreArgs(restore_type=np.ndarray)
            return RestoreArgs()

        restore_args = jax.tree_util.tree_map(_mk_restore_args, metadata.tree)
        return checkpointer.restore(path, restore_args=restore_args)

    force_cpu_restore = (
        os.environ.get("JAX_AHT_FORCE_CPU_RESTORE", "0") == "1"
        or os.environ.get("JAX_PLATFORMS", "").lower() == "cpu"
    )

    if force_cpu_restore:
        restored = _restore_with_numpy_args()
    else:
        try:
            restored = checkpointer.restore(path)
        except Exception as exc:
            msg = str(exc)
            recoverable = (
                "sharding passed to deserialization" in msg
                or "Device cuda:0 was not found in jax.local_devices()" in msg
            )
            if not recoverable:
                raise
            restored = _restore_with_numpy_args()
    # convert pytree leaves from np arrays to jax arrays
    restored = jax.tree_util.tree_map(
        lambda x: jnp.array(x) if isinstance(x, np.ndarray) else x,
        restored
    )
    return restored

def save_train_run_as_pickle(out, savedir, savename):
    if not os.path.exists(savedir):
        os.makedirs(savedir, exist_ok=True)
        
    savepath = f"{savedir}/{savename}.pkl"
    with open(savepath, "wb") as f:
        pickle.dump(out, f)
    return savepath

def load_checkpoints_from_pickle(path, ckpt_key="checkpoints"):
    out = load_train_run_from_pickle(path)
    return out[ckpt_key]

def load_train_run_from_pickle(path):
    with open(path, "rb") as f:
        out = pickle.load(f)
    return out