from model import Mamba, ModelArgs
from transformers import AutoTokenizer
import torch
import torch.nn.functional as F


# One of:
#     'state-spaces/mamba-2.8b-slimpj'
#     'state-spaces/mamba-2.8b'
#     'state-spaces/mamba-1.4b'
#     'state-spaces/mamba-790m'
#     'state-spaces/mamba-370m'
#     'state-spaces/mamba-130m'
pretrained_model_name = "state-spaces/mamba-370m"

model = Mamba.from_pretrained(pretrained_model_name)
tokenizer = AutoTokenizer.from_pretrained("EleutherAI/gpt-neox-20b")


def generate(model, tokenizer, prompt: str, n_tokens_to_gen: int = 50, sample: bool = True, top_k: int = 40):
    model.eval()

    input_ids = tokenizer(prompt, return_tensors="pt").input_ids

    for token_n in range(n_tokens_to_gen):
        with torch.no_grad():
            indices_to_input = input_ids
            next_token_logits = model(indices_to_input)[:, -1]

        probs = F.softmax(next_token_logits, dim=-1)
        (batch, vocab_size) = probs.shape

        if top_k is not None:
            (values, indices) = torch.topk(probs, k=top_k)
            probs[probs < values[:, -1, None]] = 0
            probs = probs / probs.sum(axis=1, keepdims=True)

        if sample:
            next_indices = torch.multinomial(probs, num_samples=1)
        else:
            next_indices = torch.argmax(probs, dim=-1)[:, None]

        input_ids = torch.cat([input_ids, next_indices], dim=1)

    output_completions = [tokenizer.decode(output.tolist()) for output in input_ids][0]

    return output_completions


print(generate(model, tokenizer, "Mamba is the"))