# coding=utf-8
# Copyright 2020 Google and The HuggingFace Inc. team.
#
# 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.

import argparse
import os
from pathlib import Path
from typing import Dict

import tensorflow as tf
import torch
from tqdm import tqdm

from . import PegasusConfig, PegasusForConditionalGeneration, PegasusTokenizer
from .configuration_pegasus import DEFAULTS, task_specific_params


PATTERNS = [
    # replace left string with right string to get the relevant state_dict key (identical state dict to bart)
    ["memory_attention", "encoder_attn"],
    ["attention", "attn"],
    ["/", "."],
    [".LayerNorm.gamma", "_layer_norm.weight"],
    [".LayerNorm.beta", "_layer_norm.bias"],
    ["r.layer_", "r.layers."],
    ["output_proj", "out_proj"],
    ["ffn.dense_1.", "fc2."],
    ["ffn.dense.", "fc1."],
    ["ffn_layer_norm", "final_layer_norm"],
    ["kernel", "weight"],
    ["encoder_layer_norm.", "encoder.layer_norm."],
    ["decoder_layer_norm.", "decoder.layer_norm."],
    ["embeddings.weights", "shared.weight"],
]


def rename_state_dict_key(k):

    for pegasus_name, hf_name in PATTERNS:
        k = k.replace(pegasus_name, hf_name)
    return k


# See appendix C of paper for all hyperparams


def convert_pegasus(tf_weights: dict, cfg_updates: dict) -> PegasusForConditionalGeneration:
    cfg_kwargs = DEFAULTS.copy()
    cfg_kwargs.update(cfg_updates)
    cfg = PegasusConfig(**cfg_kwargs)
    torch_model = PegasusForConditionalGeneration(cfg)
    sd = torch_model.model.state_dict()
    mapping = {}
    for k, v in tf_weights.items():
        new_k = rename_state_dict_key(k)
        if new_k not in sd:
            raise ValueError(f"could not find new key {new_k} in state dict. (converted from {k})")

        if "dense" in k or "proj" in new_k:
            v = v.T
        mapping[new_k] = torch.tensor(v, dtype=sd[new_k].dtype)
        assert v.shape == sd[new_k].shape, f"{new_k}, {k}, {v.shape}, {sd[new_k].shape}"
    # make sure embedding.padding_idx is respected
    mapping["shared.weight"][cfg.pad_token_id] = torch.zeros_like(mapping["shared.weight"][cfg.pad_token_id + 1])
    mapping["encoder.embed_tokens.weight"] = mapping["shared.weight"]
    mapping["decoder.embed_tokens.weight"] = mapping["shared.weight"]
    empty_biases = {k: torch.zeros_like(v) for k, v in sd.items() if k.endswith("bias") and k not in mapping}
    mapping.update(**empty_biases)
    missing, extra = torch_model.model.load_state_dict(mapping, strict=False)
    unexpected_missing = [
        k for k in missing if k not in ["encoder.embed_positions.weight", "decoder.embed_positions.weight"]
    ]
    assert unexpected_missing == [], f"no matches found for the following torch keys {unexpected_missing}"
    assert extra == [], f"no matches found for the following tf keys {extra}"
    return torch_model


def get_tf_weights_as_numpy(path="./ckpt/aeslc/model.ckpt-32000") -> Dict:
    init_vars = tf.train.list_variables(path)
    tf_weights = {}
    ignore_name = ["Adafactor", "global_step"]
    for name, shape in tqdm(init_vars, desc="converting tf checkpoint to dict"):
        skip_key = any([pat in name for pat in ignore_name])
        if skip_key:
            continue
        array = tf.train.load_variable(path, name)
        tf_weights[name] = array
    return tf_weights


def convert_pegasus_ckpt_to_pytorch(ckpt_path: str, save_dir: str):
    # save tokenizer first
    dataset = Path(ckpt_path).parent.name
    desired_max_model_length = task_specific_params[f"summarization_{dataset}"]["max_position_embeddings"]
    tok = PegasusTokenizer.from_pretrained("sshleifer/pegasus", model_max_length=desired_max_model_length)
    assert tok.model_max_length == desired_max_model_length
    tok.save_pretrained(save_dir)

    # convert model
    tf_weights = get_tf_weights_as_numpy(ckpt_path)
    cfg_updates = task_specific_params[f"summarization_{dataset}"]
    if dataset == "large":
        cfg_updates["task_specific_params"] = task_specific_params
    torch_model = convert_pegasus(tf_weights, cfg_updates)
    torch_model.save_pretrained(save_dir)
    sd = torch_model.state_dict()
    sd.pop("model.decoder.embed_positions.weight")
    sd.pop("model.encoder.embed_positions.weight")
    torch.save(sd, Path(save_dir) / "pytorch_model.bin")


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    # Required parameters
    parser.add_argument("tf_ckpt_path", type=str, help="passed to tf.train.list_variables")
    parser.add_argument("save_dir", default=None, type=str, help="Path to the output PyTorch model.")
    args = parser.parse_args()
    if args.save_dir is None:
        dataset = Path(args.tf_ckpt_path).parent.name
        args.save_dir = os.path.join("pegasus", dataset)
    convert_pegasus_ckpt_to_pytorch(args.tf_ckpt_path, args.save_dir)
