# Copyright (c) Kyutai, all rights reserved.
# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.

from typing import Optional

import mlx.core as mx

from ..modules.conditioner import ConditionTensor
from ..models import Lm
from ..utils import sampling


class LmGen:
    def __init__(
        self,
        model: Lm,
        max_steps: int,
        text_sampler: sampling.Sampler,
        audio_sampler: sampling.Sampler,
        cfg_coef: float = 1.0,
        check: bool = False,
        on_text_hook=None,
        on_audio_hook=None,
    ):
        self.model: Lm = model
        self.text_sampler = text_sampler
        self.audio_sampler = audio_sampler
        self.max_steps = max_steps
        self.check = check
        self.num_codebooks = 1 + model.cfg.audio_codebooks
        self.gen_sequence = mx.full(
            shape=(1, self.num_codebooks, max_steps),
            vals=self.ungenerated_token,
            dtype=mx.int32,
        )
        self.step_idx = 0
        self.audio_padding_token = self.model.cfg.audio_padding_token
        self.audio_delays = self.model.cfg.audio_delays
        self.max_delay = max(self.audio_delays)
        self.main_codebooks = self.model.cfg.depformer.num_slices
        self.cfg_coef = cfg_coef
        self.on_text_hook = on_text_hook
        self.on_audio_hook = on_audio_hook

    @property
    def zero_token(self) -> int:
        """Special value in the input tokens, indicating that no sampling should
        happen for that value, and no input should be given to the model."""
        return -1

    @property
    def ungenerated_token(self) -> int:
        """Special value that can be provided in the prompt to indicate that this specific
        value should be predicted and sampled. This allows for partial teacher forcing, by generating
        one modality, with the other one fixed.
        """
        return -2

    def _step(
        self,
        other_audio_tokens: mx.array,
        ct: ConditionTensor | None = None,
        cross_attention_src: mx.array | None = None,
    ) -> tuple[mx.array, mx.array]:
        if self.step_idx >= self.max_steps:
            raise ValueError(f"reached max-steps {self.max_steps}")

        if self.step_idx == 0:
            text_tokens = mx.array([[self.model.cfg.text_out_vocab_size]])
        else:
            text_tokens = self.gen_sequence[:, 0, self.step_idx - 1][None]
        self.gen_sequence[:, 1 + self.main_codebooks :, self.step_idx] = (
            other_audio_tokens
        )
        audio_tokens = []
        for cb_idx, delay in enumerate(self.audio_delays):
            gen_idx = self.step_idx - 1 - delay
            if gen_idx >= 0:
                audio_token = self.gen_sequence[:, cb_idx + 1, gen_idx][None]
            else:
                audio_token = mx.array([[self.audio_padding_token]])
            if (audio_token == self.ungenerated_token).any():  # type: ignore
                raise ValueError(
                    f"ungenerated value in audio tokens cb: {cb_idx} step: {self.step_idx}"
                )
            assert audio_token.shape == (1, 1), "invalid audio-tokens shape"
            audio_tokens.append(audio_token)
        if (text_tokens == self.ungenerated_token).any():  # type: ignore
            raise ValueError(f"ungenerated value in text tokens {self.step_idx}")
        assert text_tokens.shape == (1, 1), "invalid text-tokens shape"
        text_tokens, audio_tokens, transformer_out = self.model._sample(
            text_tokens,
            audio_tokens,
            self.text_sampler,
            self.audio_sampler,
            ct=ct,
            cross_attention_src=cross_attention_src,
            cfg_coef=self.cfg_coef,
            on_text_hook=self.on_text_hook,
            on_audio_hook=self.on_audio_hook,
        )
        assert text_tokens.shape == (1,), "invalid output text-token shape"
        assert audio_tokens is None or audio_tokens.shape == (
            self.model.cfg.generated_codebooks,
        ), "invalid output audio-token shape"

        self.gen_sequence[:, 0, self.step_idx] = text_tokens
        for cb_idx, delay in enumerate(self.audio_delays[: self.main_codebooks]):
            gen_idx = self.step_idx - delay
            if gen_idx >= 0:
                self.gen_sequence[:, cb_idx + 1, gen_idx] = audio_tokens[cb_idx]
        self.step_idx += 1
        return text_tokens, transformer_out

    def step(
        self,
        other_audio_tokens: mx.array,
        ct: ConditionTensor | None = None,
        cross_attention_src: mx.array | None = None,
    ) -> mx.array:
        return self._step(other_audio_tokens, ct, cross_attention_src)[0]

    def step_with_extra_heads(
        self,
        other_audio_tokens: mx.array,
        ct: ConditionTensor | None = None,
        cross_attention_src: mx.array | None = None,
    ) -> tuple[mx.array, list[mx.array]]:
        text, transformer_out = self._step(other_audio_tokens, ct, cross_attention_src)
        extra_heads = [eh(transformer_out) for eh in self.model.extra_heads]
        return text, extra_heads

    def last_audio_tokens(self) -> Optional[mx.array]:
        gen_idx = self.step_idx - 1 - self.max_delay
        if gen_idx < 0:
            return None
        tokens = self.gen_sequence[:, 1 : 1 + self.main_codebooks, gen_idx]
        if (tokens == self.audio_padding_token).any():  # type: ignore
            return None
        if (tokens == self.ungenerated_token).any():  # type: ignore
            raise ValueError(f"ungenerated value in last-audio tokens {self.step_idx}")
        return tokens
