# coding=utf-8
# Copyright (c) 2020, NVIDIA CORPORATION.  All rights reserved.
#
# 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
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"""Batching utilities."""


import torch


from megatron import get_tokenizer


def tokenize_prompts_and_batch(prompts, tokens_to_generate):
    """Given a set of prompts and number of tokens to generate:
        - tokenize prompts
        - set the sequence length to be the max of length of prompts
          plus the number of tokens we would like to generate
        - pad all the sequences to this length so we can convert them
          into a 2D tensor.
    """

    # Tokenize all the prompts.
    tokenizer = get_tokenizer()
    prompts_tokens = [tokenizer.tokenize(prompt) for prompt in prompts]

    # Now we have a list of list of tokens which each list has a different
    # size. We want to extend this list to:
    #   - incorporate the tokens that need to be generated
    #   - make all the sequences equal length.
    # Get the prompts length.
    prompts_length = [len(prompt_tokens) for prompt_tokens in prompts_tokens]
    # Get the max prompts length.
    max_prompt_len = max(prompts_length)
    # Number of tokens in the each sample of the batch.
    samples_length = max_prompt_len + tokens_to_generate
    # Now update the list of list to be of the same size: samples_length.
    for prompt_tokens, prompt_length in zip(prompts_tokens, prompts_length):
        padding_size = samples_length - prompt_length
        prompt_tokens.extend([tokenizer.eod] * padding_size)

    # Now we are in a structured format, we can convert to tensors.
    prompts_tokens_tensor = torch.cuda.LongTensor(prompts_tokens)
    prompts_length_tensor = torch.cuda.LongTensor(prompts_length)

    return prompts_tokens_tensor, prompts_length_tensor