# Copyright 2025 IBM Corp.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# This file includes code adapted from the original work by EPFL and Apple Inc.,
# licensed under the Apache License, Version 2.0.
# Source: https://github.com/apple/ml-4m/

import os
import io
import re
import zarr
import torch
import fsspec
import braceexpand
import numpy as np
import albumentations
import warnings
import webdataset as wds
from collections.abc import Callable, Iterable
from torch.utils.data._utils.collate import default_collate
from webdataset.handlers import warn_and_continue

# Definition of all shard files in TerraMesh
split_files = {
    "ssl4eos12": {
        "train": ["ssl4eos12_shard_{000794..000889}.tar"],
        "val": ["ssl4eos12_shard_000009.tar"],
    },
    "majortom": {
        "train": ["majortom_shard_{000001..000793}.tar"],
        "val": ["majortom_shard_{000001..000008}.tar"],
    },
    "combined": {
        "train": ["majortom_shard_{000001..000793}.tar", "ssl4eos12_shard_{000794..000889}.tar"],
        "val": ["majortom_shard_{000001..000008}.tar", "ssl4eos12_shard_000009.tar"],
    }
}

statistics = {
    "mean": {
        "S2L1C": [2357.090, 2137.398, 2018.799, 2082.998, 2295.663, 2854.548, 3122.860, 3040.571, 3306.491, 1473.849,
                  506.072, 2472.840, 1838.943],
        "S2L2A": [1390.461, 1503.332, 1718.211, 1853.926, 2199.116, 2779.989, 2987.025, 3083.248, 3132.235, 3162.989,
                  2424.902, 1857.665],
        "S2RGB": [110.349, 99.507, 75.843],
        "S1GRD": [-12.577, -20.265],
        "S1RTC": [-10.93, -17.329],
        "NDVI": [0.327],
        "DEM": [651.663],
    },
    "std": {
        "S2L1C": [1673.639, 1722.641, 1602.205, 1873.138, 1866.055, 1779.839, 1776.496, 1724.114, 1771.041, 1079.786,
                  512.404, 1340.879, 1172.435],
        "S2L2A": [2131.157, 2163.666, 2059.311, 2152.477, 2105.179, 1912.773, 1842.326, 1893.568, 1775.656, 1814.907,
                  1436.282, 1336.155],
        "S2RGB": [69.905, 53.708, 53.378],
        "S1GRD": [5.179, 5.872],
        "S1RTC": [4.391, 4.459],
        "NDVI": [0.322],
        "DEM": [928.168]
    }
}


def build_terramesh_dataset(
        path: str = "https://huggingface.co/datasets/ibm-esa-geospatial/TerraMesh/resolve/main/",
        modalities: list | str = None,
        split: str = "val",
        urls: str | None = None,
        batch_size: int = 8,
        return_metadata: bool = False,
        shuffle: bool = True,
        *args, **kwargs,
):
    if len(modalities) == 1:
        # Build standard WebDataset for single modality
        dataset = build_wds_dataset(
            path=path,
            modality=modalities[0],
            split=split,
            urls=urls,
            batch_size=batch_size,
            return_metadata=return_metadata,
            shuffle=shuffle,
            *args, **kwargs
        )
        return dataset

    else:
        # Build custom multi-modal dataset
        dataset = build_multimodal_dataset(
            path=path,
            modalities=modalities,
            split=split,
            urls=urls,
            batch_size=batch_size,
            return_metadata=return_metadata,
            shuffle=shuffle,
            *args, **kwargs,
        )
        return dataset


def zarr_decoder(key, value):
    if key == "zarr.zip" or key.endswith(".zarr.zip"):
        mapper = fsspec.filesystem("zip", fo=io.BytesIO(value), block_size=None).get_mapper("")
        return zarr.open_consolidated(mapper, mode="r")["bands"][...]


def zarr_metadata_decoder(sample):
    for key, value in list(sample.items()):
        if key == "zarr.zip" or key.endswith(".zarr.zip"):
            mapper = fsspec.filesystem("zip", fo=io.BytesIO(value), block_size=None).get_mapper("")
            data = zarr.open_consolidated(mapper, mode="r")
            sample[key] = data["bands"][...]

            # Add metadata
            if "center_lon" not in sample.keys():  # Same center point for all modalities
                sample["center_lon"] = data["center_lon"][...]
                sample["center_lat"] = data["center_lat"][...]
            if "cloud_mask" in data and "cloud_mask" not in sample.keys():  # Same S2 mask in all optical modalities
                sample["cloud_mask"] = data["cloud_mask"][...][np.newaxis, ...]  # Add channel dim to mask
            if data["time"][...] > 1e6:  # DEM has no valid timestamp (value = 0)
                time_key = "time" if key == "zarr.zip" else "time_" + key
                sample[time_key] = data["time"][...]  # Integer values of type "datetime64[ns]"
        # TODO Other types are currently not decoded, fall back to autodecode

    return sample


def identity(sample):
    """Identity function that does nothing."""
    return sample


def drop_time_dim(value, dim: int = 0):
    """
    Remove time dimension from data tensors.
    """
    if isinstance(value, np.ndarray) or isinstance(value, torch.Tensor):
        return value.squeeze(dim)

    elif isinstance(value, dict):
        for k, v in value.items():
            if isinstance(v, np.ndarray) or isinstance(v, torch.Tensor):
                value[k] = v.squeeze(dim)
        return value


def build_wds_dataset(
        path: str = "https://huggingface.co/datasets/ibm-esa-geospatial/TerraMesh/resolve/main/",
        modality: str = "S2L2A",
        split: str = "val",
        urls: str | None = None,
        batch_size: int = 8,
        transform: Callable = None,
        shuffle: bool = True,
        return_metadata: bool = False,
        *args, **kwargs
):
    if urls is None:
        # Select split files
        if modality == "S1GRD":
            files = split_files["ssl4eos12"][split]
        elif modality == "S1GRD":
            files = split_files["majortom"][split]
        else:
            files = split_files["combined"][split]

        # Joins majortom and ssl4eos12 shard files with "::" (except for S-1 modalities)
        urls = "::".join(
            [os.path.join(path, split, modality, f) for f in files]
        )

    kwargs["shardshuffle"] = kwargs.get("shardshuffle", 100) * shuffle  # Shuffle shard

    # Build dataset
    dataset = wds.WebDataset(urls, *args, **kwargs)

    # Decode from bytes to numpy arrays, etc.
    dataset = dataset.map(zarr_metadata_decoder) if return_metadata else dataset.decode(zarr_decoder)

    # Rename modality to "image" and remove temporal dimension
    dataset = (dataset
               .rename(image="zarr.zip")
               .map(drop_time_dim)
               )

    if transform is not None:
        dataset = dataset.map(transform)

    # Create batches
    if batch_size is not None:
        dataset = dataset.batched(batch_size)

    return dataset


def build_multimodal_dataset(
        path: str = "https://huggingface.co/datasets/ibm-esa-geospatial/TerraMesh/resolve/main/",
        modalities: list = None,
        split: str = "val",
        urls: str | None = None,
        batch_size: int = 8,
        transform: Callable = None,
        shuffle: bool = True,
        return_metadata: bool = False,
        *args, **kwargs
):
    if modalities is None:
        modalities = ["S2L2A", "S2L1C", "S2RGB", "S1GRD", "S1RTC", "DEM", "NDVI", "LULC"]  # Default
    if urls is None:
        # Filter modalities based availability (S1GRD and S1RTC not present in all subsets)
        def filter_list(lst, value):
            lst = lst.copy()
            # helper function to filter modalities
            if value in lst:
                lst.remove(value)
            return lst

        majortom_mod = f"[{','.join(filter_list(modalities, 'S1GRD'))}]"
        ssl4eos12_mod = f"[{','.join(filter_list(modalities, 'S1RTC'))}]"

        # Joins majortom and ssl4eos12 shard files with "::"
        urls = (os.path.join(path, split, majortom_mod, split_files["majortom"][split][0])
                + "::" + os.path.join(path, split, ssl4eos12_mod, split_files["ssl4eos12"][split][0]))

    dataset = build_datapipeline(urls, transform, batch_size, shuffle, return_metadata, *args, **kwargs)
    return dataset


def build_datapipeline(urls, transform, batch_size, shuffle, return_metadata, *args, **kwargs):
    shardshuffle = kwargs.get("shardshuffle", 100) * shuffle  # Shuffle shard
    deterministic = kwargs.get("deterministic", False)
    seed = kwargs.get("seed", 0)

    datapipeline = wds.DataPipeline(
        # Infinitely sample shards from the shard list with replacement. Each worker is seeded independently.
        (
            wds.ResampledShards(urls, deterministic=deterministic, seed=seed)
            if shuffle else wds.SimpleShardList(urls)
        ),
        multi_tarfile_samples,  # Extract individual samples from multi-modal tar files
        wds.shuffle(shardshuffle, seed=seed),  # Shuffle with a buffer of given size
        (
            wds.map(zarr_metadata_decoder)
            if return_metadata
            else wds.decode(zarr_decoder)  # Decode from bytes to numpy arrays, etc.
        ),
        wds.map(drop_time_dim),  # Remove time dimension from tensors
        wds.map(remove_extensions),  # Remove "file extensions" from dictionary keys
        (  # Apply transformation
            wds.map(transform)
            if transform is not None
            else wds.map(identity)
        ),
        (  # Batching
            wds.batched(batch_size, collation_fn=default_collate, partial=False)
            if batch_size is not None
            else wds.map(identity)
        ),
    )
    return datapipeline


def extract_modality_names(s):
    """
    Function from https://github.com/apple/ml-4m/blob/main/fourm/data/unified_datasets.py.
    """
    # Regular expression pattern to match anything enclosed in "{" and "}", and comma separated
    pattern = r"\{([^}]*)\}"
    match = re.search(pattern, s)
    return match.group(1).split(",") if match else []


def remove_ext_with_gz(s):
    """
    Function from https://github.com/apple/ml-4m/blob/main/fourm/data/unified_datasets.py.
    """
    if s.endswith(".gz"):
        s = s.replace(".gz", "")
    if s.endswith(".zip"):
        s = s.replace(".zip", "")
    return os.path.splitext(s)[0]


def remove_extensions(sample):
    """
    Function from https://github.com/apple/ml-4m/blob/main/fourm/data/unified_datasets.py.

    In webdatasets, we identify the type of a given modality by adding an extension
    in the form f"{modality_name}.{modality_extension}", e.g. "rgb.jpg" or "caption.json".
    This function removes them and returns a dictionary of {f"{modality_name}": modality}.
    """
    return {remove_ext_with_gz(k): v for k, v in sample.items()}


def multi_tarfile_samples(
        src_iter: Iterable[dict],
        handler: Callable[[Exception], bool] = warn_and_continue,
):
    """
    This function is adapted from https://github.com/apple/ml-4m/blob/main/fourm/data/unified_datasets.py.

    Webdataset does not support splitting up shards by modality, so we need to do this manually.
    Usually, we would need to save all modalities in the same tar file, e.g. shard_root_train/{00000..12345}.tar,
    where each shard contains 1000 samples and each sample contains all modalities.
    This is not flexible when adding new modalities, so we instead save each modality in a separate tar file,
    e.g. shard_root_train_rgb/{00000..12345}.tar, shard_root_train_caption/{00000..12345}.tar, etc., where each shard contains
    again 1000 samples, but each sample contains only one modality. All samples in all shards have to be aligned.

    This function takes an iterator over shard URLs, where we use brace expansion to specify multiple tar files per modality.
    E.g. shard_root_train_[rgb,caption]/00123.tar will be expanded to shard_root_train_rgb/00123.tar and shard_root_train_caption/00123.tar,
    and the samples from these two tar files will be combined into a single sample.

    Args:
        src_iter: Iterator over shards that *already brace expanded the shard numbers*,
            e.g. {"url": "shard_root_train_[rgb,caption]/00000.tar"}, {"url": "shard_root_train_[rgb,caption]/00001.tar"}, ...
            This function will also work when no square braces for multiple modalities are used, e.g. {"url": "shard_root_train/00000.tar"}, ...
            It can be a drop-in replacement for wds.tarfile_samples.
        handler: Function that handles exceptions. If it returns True, the shard is skipped. If it returns False, the function exits.

    Yields:
        Dictionary of aligned samples from all modalities.
    """

    for src in src_iter:

        # Multi tar file URLs use brace expansion with square braces
        multi_tar_urls = src["url"].translate(str.maketrans("[]", "{}"))
        modality_names = extract_modality_names(multi_tar_urls)
        multi_tar_urls = list(braceexpand.braceexpand(multi_tar_urls))

        # Create tar iterators for shards of all modalities
        tar_iters = [
            wds.tarfile_samples([{"url": tar_url}]) for tar_url in multi_tar_urls
        ]

        try:
            # Loop over these iterators in parallel and combine the tar files from different modalities
            for multi_tar_files in zip(*tar_iters):

                merged_dict = {}
                merged_dict["__key__"] = multi_tar_files[0]["__key__"]
                merged_dict["__url__"] = src["url"]

                for modality_name, modality_dict in zip(
                        modality_names, multi_tar_files
                ):
                    _key = modality_dict.pop("__key__")
                    _url = modality_dict.pop("__url__")

                    if _key != merged_dict["__key__"]:
                        raise ValueError(
                            f"Divergence detected! Trying to merge keys {_key} of {modality_name} and {merged_dict['__key__']} of merged_dict with modalities {merged_dict.keys()}."
                        )

                    for k, v in modality_dict.items():
                        if modality_name is None:
                            merged_dict[k] = v
                        else:
                            merged_dict[f"{modality_name}.{k}"] = v

                yield merged_dict

        except Exception as e:
            print(e)
            print(f"Exception occurred while processing {src['url']}.")
            if handler(e):
                print("Skipping shard...")
                continue
            else:
                break


class Transpose(albumentations.ImageOnlyTransform):
    """
    Rearrange is a generic image transformation that reshapes an input tensor using a custom einops pattern.

    This transform allows flexible reordering of tensor dimensions based on the provided pattern and arguments.
    """

    def __init__(self, axis: list):
        """
        Initialize the Transpose transform.

        Args:
            axis (list): Axis for numpy.transpose.
        """
        super().__init__(p=1)
        self.axis = axis

    def apply(self, img, **params):
        return np.transpose(img, self.axis)

    def get_transform_init_args_names(self):
        return "transpose"


def default_non_image_transform(array):
    if hasattr(array, "dtype") and (array.dtype == float or array.dtype == int):
        return torch.from_numpy(array)
    else:
        return array


class MultimodalTransforms:
    """
    MultimodalTransforms applies albumentations transforms to multiple image modalities.

    This class supports both shared transformations across modalities and separate transformations for each modality.
    It also handles non-image modalities by applying a specified non-image transform.

    This code is adapted from https://github.com/IBM/terratorch/blob/main/terratorch/datasets/transforms.py.
    """

    def __init__(
            self,
            transforms: dict | albumentations.Compose,
            non_image_modalities: list[str] | None = None,
            non_image_transforms: object | None = None,
    ):
        """
        Initialize the MultimodalTransforms.

        Args:
            transforms (dict or A.Compose): The transformation(s) to apply to the data.
            non_image_modalities (list[str] | None): List of keys corresponding to non-image modalities.
            non_image_transforms (object | None): A transform to apply to non-image modalities.
                If None, a default transform is used.
        """
        self.transforms = transforms
        self.non_image_modalities = non_image_modalities or []
        self.non_image_transforms = non_image_transforms or default_non_image_transform

    def __call__(self, data: dict):
        # albumentations requires a key "image" and treats all other keys as additional targets
        image_modality = "image" if "image" in data else \
            [k for k in data.keys() if k not in self.non_image_modalities][0]  # Find an image modality name
        data["image"] = data.pop(image_modality)  # albumentations expects an input called "image"
        data = self.transforms(**data)
        data[image_modality] = data.pop("image")

        # Process sequence data which is ignored by albumentations as "global_label"
        for modality in self.non_image_modalities:
            if modality in data:
                data[modality] = self.non_image_transforms(data[modality])

        return data


class MultimodalNormalize(Callable):
    def __init__(self, mean: dict[str, list[float]], std: dict[str, list[float]]):
        super().__init__()
        self.mean = mean
        self.std = std

    def __call__(self, **batch):
        for m in self.mean.keys():
            if m not in batch.keys():
                continue
            batch[m] = (batch[m] - self.mean[m]) / self.std[m]
        return batch

    def add_targets(self, targets):
        """
        Required by albumentations
        """
        pass