# Copyright (c) 2024 Alibaba Inc (authors: Xiang Lyu, Zhihao Du)
#
# 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.
from typing import Dict, Optional, Union
import torch
from torch import nn
import torch.nn.functional as F
from torch.nn.utils.rnn import pad_sequence, unpad_sequence
from cosyvoice.utils.common import IGNORE_ID
from cosyvoice.transformer.label_smoothing_loss import LabelSmoothingLoss
from cosyvoice.utils.common import th_accuracy


class TransformerLM(torch.nn.Module):
    def __init__(
            self,
            text_encoder_input_size: int,
            llm_input_size: int,
            llm_output_size: int,
            text_token_size: int,
            speech_token_size: int,
            text_encoder: torch.nn.Module,
            llm: torch.nn.Module,
            length_normalized_loss: bool = True,
            lsm_weight: float = 0.0,
            spk_embed_dim: int = 192,
    ):
        super().__init__()
        self.llm_input_size = llm_input_size
        self.speech_token_size = speech_token_size
        # 1. build text token inputs related modules
        self.text_embedding = torch.nn.Embedding(text_token_size, text_encoder_input_size)
        self.text_encoder = text_encoder
        self.text_encoder_affine_layer = nn.Linear(
            self.text_encoder.output_size(),
            llm_input_size
        )

        # 2. build speech token language model related modules
        self.sos_eos = 0
        self.task_id = 1
        self.llm_embedding = torch.nn.Embedding(2, llm_input_size)
        self.llm = llm
        self.llm_decoder = nn.Linear(llm_output_size, speech_token_size + 1)
        self.criterion_ce = LabelSmoothingLoss(
            size=speech_token_size + 1,
            padding_idx=IGNORE_ID,
            smoothing=lsm_weight,
            normalize_length=length_normalized_loss,
        )

        # 3. [Optional] build speech token related modules
        self.speech_embedding = torch.nn.Embedding(speech_token_size, llm_input_size)
        self.spk_embed_affine_layer = torch.nn.Linear(spk_embed_dim, llm_input_size)

    def encode(
            self,
            text: torch.Tensor,
            text_lengths: torch.Tensor,
    ):
        encoder_out, encoder_mask = self.text_encoder(text, text_lengths, decoding_chunk_size=1, num_decoding_left_chunks=-1)
        encoder_out_lens = encoder_mask.squeeze(1).sum(1)
        encoder_out = self.text_encoder_affine_layer(encoder_out)
        return encoder_out, encoder_out_lens

    def pad_unpad_sequence(self, sos_eos_emb, embedding, text_token, text_token_len, task_id_emb, speech_token, speech_token_len):
        text_token = unpad_sequence(text_token, text_token_len.cpu(), batch_first=True)
        speech_token = unpad_sequence(speech_token, speech_token_len.cpu(), batch_first=True)
        lm_input = [torch.concat([sos_eos_emb.squeeze(dim=0), embedding[i], text_token[i], task_id_emb.squeeze(dim=0), speech_token[i]], dim=0) for i in range(len(text_token))]
        lm_input_len = torch.tensor([i.size(0) for i in lm_input], dtype=torch.int32)
        lm_input = pad_sequence(lm_input, batch_first=True, padding_value=IGNORE_ID)
        return lm_input, lm_input_len

    def forward(
            self,
            batch: dict,
            device: torch.device,
    ) -> Dict[str, Optional[torch.Tensor]]:
        """
        Args:
            text: (B, L, D)
            text_lengths: (B,)
            audio: (B, T, N) or (B, T)
            audio_lengths: (B,)
        """
        text_token = batch['text_token'].to(device)
        text_token_len = batch['text_token_len'].to(device)
        speech_token = batch['speech_token'].to(device)
        speech_token_len = batch['speech_token_len'].to(device)
        embedding = batch['embedding'].to(device)

        # 1. prepare llm_target
        lm_target = [torch.tensor([IGNORE_ID] * (2 + text_token_len[i]) + speech_token[i, :speech_token_len[i]].tolist() + [self.speech_token_size]) for i in range(text_token.size(0))]
        lm_target = pad_sequence(lm_target, batch_first=True, padding_value=IGNORE_ID).to(device)

        # 1. encode text_token
        text_token = self.text_embedding(text_token)
        text_token, text_token_len = self.encode(text_token, text_token_len)

        # 2. embedding projection
        embedding = F.normalize(embedding, dim=1)
        embedding = self.spk_embed_affine_layer(embedding)
        embedding = embedding.unsqueeze(1)

        # 3. eos and task_id
        sos_eos_emb = self.llm_embedding.weight[self.sos_eos].reshape(1, 1, -1)
        task_id_emb = self.llm_embedding.weight[self.task_id].reshape(1, 1, -1)

        # 4. encode speech_token
        speech_token = self.speech_embedding(speech_token)

        # 5. unpad and pad
        lm_input, lm_input_len = self.pad_unpad_sequence(sos_eos_emb, embedding, text_token, text_token_len, task_id_emb, speech_token, speech_token_len)

        # 6. run lm forward
        lm_output, lm_output_mask = self.llm(lm_input, lm_input_len.to(device))
        logits = self.llm_decoder(lm_output)
        loss = self.criterion_ce(logits, lm_target)
        acc = th_accuracy(logits.view(-1, self.speech_token_size + 1), lm_target, ignore_label=IGNORE_ID)
        return {'loss': loss, 'acc': acc}

    def sampling_ids(
            self,
            weighted_scores: torch.Tensor,
            sampling: Union[bool, int, float] = True,
            beam_size: int = 1,
            ignore_eos: bool = True,
    ):
        while True:
            prob, indices = weighted_scores.softmax(dim=-1).topk(sampling)
            top_ids = prob.multinomial(beam_size, replacement=True)
            top_ids = indices[top_ids]
            if (not ignore_eos) or (self.speech_token_size not in top_ids):
                break
        return top_ids

    @torch.inference_mode()
    def inference(
            self,
            text: torch.Tensor,
            text_len: torch.Tensor,
            prompt_text: torch.Tensor,
            prompt_text_len: torch.Tensor,
            prompt_speech_token: torch.Tensor,
            prompt_speech_token_len: torch.Tensor,
            embedding: torch.Tensor,
            beam_size: int = 1,
            sampling: int = 25,
            max_token_text_ratio: float = 20,
            min_token_text_ratio: float = 2,
    ) -> torch.Tensor:
        device = text.device
        text = torch.concat([prompt_text, text], dim=1)
        text_len += prompt_text_len
        text = self.text_embedding(text)

        # 1. encode text
        text, text_len = self.encode(text, text_len)

        # 2. encode embedding
        if embedding.shape[0] != 0:
            embedding = F.normalize(embedding, dim=1)
            embedding = self.spk_embed_affine_layer(embedding)
            embedding = embedding.unsqueeze(dim=1)
        else:
            embedding = torch.zeros(1, 0, self.llm_input_size).to(device)

        # 3. concat llm_input
        sos_eos_emb = self.llm_embedding.weight[self.sos_eos].reshape(1, 1, -1)
        task_id_emb = self.llm_embedding.weight[self.task_id].reshape(1, 1, -1)
        if prompt_speech_token_len != 0:
            prompt_speech_token_emb = self.speech_embedding(prompt_speech_token)
        else:
            prompt_speech_token_emb = torch.zeros(1, 0, self.llm_input_size).to(device)
        lm_input = torch.concat([sos_eos_emb, embedding, text, task_id_emb, prompt_speech_token_emb], dim=1)

        # 4. cal min/max_length
        min_len = int((text_len - prompt_text_len) * min_token_text_ratio)
        max_len = int((text_len - prompt_text_len) * max_token_text_ratio)

        # 5. step by step decode
        out_tokens = []
        offset = 0
        att_cache, cnn_cache = torch.zeros((0, 0, 0, 0), device=lm_input.device), torch.zeros((0, 0, 0, 0), device=lm_input.device)
        for i in range(max_len):
            y_pred, att_cache, cnn_cache = self.llm.forward_chunk(lm_input, offset=0, required_cache_size=-1, att_cache=att_cache, cnn_cache=cnn_cache,
                                                                  att_mask=torch.tril(torch.ones((1, lm_input.shape[1], lm_input.shape[1]), device=lm_input.device)).to(torch.bool))
            logp = self.llm_decoder(y_pred[:, -1]).log_softmax(dim=-1)
            top_ids = self.sampling_ids(logp.squeeze(dim=0), sampling, beam_size, ignore_eos=True if i < min_len else False).item()
            if top_ids == self.speech_token_size:
                break
            out_tokens.append(top_ids)
            offset += lm_input.size(1)
            lm_input = self.speech_embedding.weight[top_ids].reshape(1, 1, -1)

        return torch.tensor([out_tokens], dtype=torch.int64, device=device)