from typing import List, Optional, Union

import torch
from transformers import T5EncoderModel, T5Tokenizer


def _get_t5_prompt_embeds(
    tokenizer: T5Tokenizer,
    text_encoder: T5EncoderModel,
    prompt: Union[str, List[str]],
    num_videos_per_prompt: int = 1,
    max_sequence_length: int = 226,
    device: Optional[torch.device] = None,
    dtype: Optional[torch.dtype] = None,
    text_input_ids=None,
):
    prompt = [prompt] if isinstance(prompt, str) else prompt
    batch_size = len(prompt)

    if tokenizer is not None:
        text_inputs = tokenizer(
            prompt,
            padding="max_length",
            max_length=max_sequence_length,
            truncation=True,
            add_special_tokens=True,
            return_tensors="pt",
        )
        text_input_ids = text_inputs.input_ids
    else:
        if text_input_ids is None:
            raise ValueError("`text_input_ids` must be provided when the tokenizer is not specified.")

    prompt_embeds = text_encoder(text_input_ids.to(device))[0]
    prompt_embeds = prompt_embeds.to(dtype=dtype, device=device)

    # duplicate text embeddings for each generation per prompt, using mps friendly method
    _, seq_len, _ = prompt_embeds.shape
    prompt_embeds = prompt_embeds.repeat(1, num_videos_per_prompt, 1)
    prompt_embeds = prompt_embeds.view(batch_size * num_videos_per_prompt, seq_len, -1)

    return prompt_embeds


def encode_prompt(
    tokenizer: T5Tokenizer,
    text_encoder: T5EncoderModel,
    prompt: Union[str, List[str]],
    num_videos_per_prompt: int = 1,
    max_sequence_length: int = 226,
    device: Optional[torch.device] = None,
    dtype: Optional[torch.dtype] = None,
    text_input_ids=None,
):
    prompt = [prompt] if isinstance(prompt, str) else prompt
    prompt_embeds = _get_t5_prompt_embeds(
        tokenizer,
        text_encoder,
        prompt=prompt,
        num_videos_per_prompt=num_videos_per_prompt,
        max_sequence_length=max_sequence_length,
        device=device,
        dtype=dtype,
        text_input_ids=text_input_ids,
    )
    return prompt_embeds


def compute_prompt_embeddings(
    tokenizer: T5Tokenizer,
    text_encoder: T5EncoderModel,
    prompt: str,
    max_sequence_length: int,
    device: torch.device,
    dtype: torch.dtype,
    requires_grad: bool = False,
):
    if requires_grad:
        prompt_embeds = encode_prompt(
            tokenizer,
            text_encoder,
            prompt,
            num_videos_per_prompt=1,
            max_sequence_length=max_sequence_length,
            device=device,
            dtype=dtype,
        )
    else:
        with torch.no_grad():
            prompt_embeds = encode_prompt(
                tokenizer,
                text_encoder,
                prompt,
                num_videos_per_prompt=1,
                max_sequence_length=max_sequence_length,
                device=device,
                dtype=dtype,
            )
    return prompt_embeds