import torch
from torch import nn 
from copy import deepcopy

from .base import FM_to_MD_Util
from utils.common.log import logger
from utils.dl.common.model import set_module, get_module, get_super_module
from utils.dl.common.model import get_model_device, get_model_latency, get_model_size
from utils.common.log import logger

from transformers.models.bert.modeling_bert import BertSelfAttention
from transformers import BertConfig

from typing import Optional, Tuple
import math

class BertSelfAttentionPrunable(BertSelfAttention):
    def __init__(self):
        config = BertConfig.from_pretrained('bert-base-multilingual-cased')
        super(BertSelfAttentionPrunable, self).__init__(config)
    
    def transpose_for_scores(self, x):
        new_x_shape = x.size()[:-1] + (self.num_attention_heads, -1)
        x = x.view(new_x_shape)
        return x.permute(0, 2, 1, 3)
    
    def forward(
        self,
        hidden_states: torch.Tensor,
        attention_mask: Optional[torch.FloatTensor] = None,
        head_mask: Optional[torch.FloatTensor] = None,
        encoder_hidden_states: Optional[torch.FloatTensor] = None,
        encoder_attention_mask: Optional[torch.FloatTensor] = None,
        past_key_value: Optional[Tuple[Tuple[torch.FloatTensor]]] = None,
        output_attentions: Optional[bool] = False,
    ) -> Tuple[torch.Tensor]:
        mixed_query_layer = self.query(hidden_states)

        # If this is instantiated as a cross-attention module, the keys
        # and values come from an encoder; the attention mask needs to be
        # such that the encoder's padding tokens are not attended to.
        is_cross_attention = encoder_hidden_states is not None

        if is_cross_attention and past_key_value is not None:
            # reuse k,v, cross_attentions
            key_layer = past_key_value[0]
            value_layer = past_key_value[1]
            attention_mask = encoder_attention_mask
        elif is_cross_attention:
            key_layer = self.transpose_for_scores(self.key(encoder_hidden_states))
            value_layer = self.transpose_for_scores(self.value(encoder_hidden_states))
            attention_mask = encoder_attention_mask
        elif past_key_value is not None:
            key_layer = self.transpose_for_scores(self.key(hidden_states))
            value_layer = self.transpose_for_scores(self.value(hidden_states))
            key_layer = torch.cat([past_key_value[0], key_layer], dim=2)
            value_layer = torch.cat([past_key_value[1], value_layer], dim=2)
        else:
            key_layer = self.transpose_for_scores(self.key(hidden_states))
            value_layer = self.transpose_for_scores(self.value(hidden_states))

        query_layer = self.transpose_for_scores(mixed_query_layer)

        use_cache = past_key_value is not None
        if self.is_decoder:
            # if cross_attention save Tuple(torch.Tensor, torch.Tensor) of all cross attention key/value_states.
            # Further calls to cross_attention layer can then reuse all cross-attention
            # key/value_states (first "if" case)
            # if uni-directional self-attention (decoder) save Tuple(torch.Tensor, torch.Tensor) of
            # all previous decoder key/value_states. Further calls to uni-directional self-attention
            # can concat previous decoder key/value_states to current projected key/value_states (third "elif" case)
            # if encoder bi-directional self-attention `past_key_value` is always `None`
            past_key_value = (key_layer, value_layer)

        # Take the dot product between "query" and "key" to get the raw attention scores.
        attention_scores = torch.matmul(query_layer, key_layer.transpose(-1, -2))

        if self.position_embedding_type == "relative_key" or self.position_embedding_type == "relative_key_query":
            query_length, key_length = query_layer.shape[2], key_layer.shape[2]
            if use_cache:
                position_ids_l = torch.tensor(key_length - 1, dtype=torch.long, device=hidden_states.device).view(
                    -1, 1
                )
            else:
                position_ids_l = torch.arange(query_length, dtype=torch.long, device=hidden_states.device).view(-1, 1)
            position_ids_r = torch.arange(key_length, dtype=torch.long, device=hidden_states.device).view(1, -1)
            distance = position_ids_l - position_ids_r

            positional_embedding = self.distance_embedding(distance + self.max_position_embeddings - 1)
            positional_embedding = positional_embedding.to(dtype=query_layer.dtype)  # fp16 compatibility

            if self.position_embedding_type == "relative_key":
                relative_position_scores = torch.einsum("bhld,lrd->bhlr", query_layer, positional_embedding)
                attention_scores = attention_scores + relative_position_scores
            elif self.position_embedding_type == "relative_key_query":
                relative_position_scores_query = torch.einsum("bhld,lrd->bhlr", query_layer, positional_embedding)
                relative_position_scores_key = torch.einsum("bhrd,lrd->bhlr", key_layer, positional_embedding)
                attention_scores = attention_scores + relative_position_scores_query + relative_position_scores_key

        attention_scores = attention_scores / math.sqrt(self.attention_head_size)
        if attention_mask is not None:
            # Apply the attention mask is (precomputed for all layers in BertModel forward() function)
            attention_scores = attention_scores + attention_mask

        # Normalize the attention scores to probabilities.
        attention_probs = nn.functional.softmax(attention_scores, dim=-1)

        # This is actually dropping out entire tokens to attend to, which might
        # seem a bit unusual, but is taken from the original Transformer paper.
        attention_probs = self.dropout(attention_probs)

        # Mask heads if we want to
        if head_mask is not None:
            attention_probs = attention_probs * head_mask

        context_layer = torch.matmul(attention_probs, value_layer)

        context_layer = context_layer.permute(0, 2, 1, 3).contiguous()
        new_context_layer_shape = context_layer.size()[:-2] + (self.query.out_features,) # NOTE: modified
        context_layer = context_layer.view(new_context_layer_shape)

        outputs = (context_layer, attention_probs) if output_attentions else (context_layer,)

        if self.is_decoder:
            outputs = outputs + (past_key_value,)
        return outputs

    @staticmethod
    def init_from_exist_self_attn(attn: BertSelfAttention):
        # print(attn)
        
        res = BertSelfAttentionPrunable()
        
        for attr in dir(attn):
            # if str(attr) in ['transpose_for_scores'] or str(attr).startswith('_'):
            #     continue
            # if isinstance(getattr(attn, attr), nn.Module):
                # print(attr)
                
            if isinstance(getattr(attn, attr), nn.Module):
                try:
                    # print(attr, 'ok')
                    setattr(res, attr, getattr(attn, attr))
                    
                except Exception as e:
                    print(attr, str(e))
        
        
        
        return res

class FM_to_MD_Bert_Util(FM_to_MD_Util):
    def init_md_from_fm_by_reducing_width(self, fm: nn.Module, reducing_width_ratio: int) -> nn.Module:
        fm_vit = deepcopy(fm)
        
        for block in fm_vit.bert.encoder.layer:
            set_module(block, 'attention.self', BertSelfAttentionPrunable.init_from_exist_self_attn(block.attention.self))
        
        def _f(n):
            return int(n // reducing_width_ratio)
        
        # def _rand_indexes(n):
            # return torch.randperm(n)[0: int(n // reducing_width_ratio)]
            
        def l1_max_indexes(p: torch.Tensor, dim=0):
            assert dim in [0, 1]
            assert p.dim() in [1, 2, 4]
            
            if dim == 1:
                p = p.T
            
            p_norm = p.abs().contiguous().view(p.size(0), -1).sum(dim=1)
            n = p.size(0)
            return p_norm.argsort(descending=True)[0: int(n // reducing_width_ratio)].sort()[0]
        
        for block_i, block in enumerate(fm_vit.bert.encoder.layer):
            for k in ['query', 'key', 'value']:
                qkv = get_module(block, f'attention.self.{k}')

                new_qkv = nn.Linear(qkv.in_features, _f(qkv.out_features), 
                                    qkv.bias is not None, qkv.weight.device)
                indexes = l1_max_indexes(qkv.weight.data, 0)
                
                new_qkv.weight.data.copy_(qkv.weight.data[indexes])
                if qkv.bias is not None:
                    new_qkv.bias.data.copy_(qkv.bias.data[indexes])
                set_module(block, f'attention.self.{k}', new_qkv)
            
            proj = get_module(block, f'attention.output.dense')
            new_proj = nn.Linear(_f(proj.in_features), proj.out_features, 
                                proj.bias is not None, proj.weight.device)
            new_proj.weight.data.copy_(proj.weight.data[:, l1_max_indexes(proj.weight.data, 1)])
            if proj.bias is not None:
                new_proj.bias.data.copy_(proj.bias.data)
            set_module(block, f'attention.output.dense', new_proj)
            
            fc1 = get_module(block, f'intermediate.dense')
            new_fc1 = nn.Linear(fc1.in_features, _f(fc1.out_features), 
                                fc1.bias is not None, fc1.weight.device)
            indexes = l1_max_indexes(fc1.weight.data, 0)
            new_fc1.weight.data.copy_(fc1.weight.data[indexes])
            if fc1.bias is not None:
                new_fc1.bias.data.copy_(fc1.bias.data[indexes])
            set_module(block, f'intermediate.dense', new_fc1)

            fc2 = get_module(block, f'output.dense')
            new_fc2 = nn.Linear(_f(fc2.in_features), fc2.out_features, 
                                fc2.bias is not None, fc2.weight.device)
            new_fc2.weight.data.copy_(fc2.weight.data[:, l1_max_indexes(fc2.weight.data, 1)])
            if fc2.bias is not None:
                new_fc2.bias.data.copy_(fc2.bias.data)
            set_module(block, f'output.dense', new_fc2)
            
        return fm_vit
    
    def init_md_from_fm_by_reducing_width_with_perf_test(self, fm: nn.Module, reducing_width_ratio: int,
                                                         samples: torch.Tensor) -> nn.Module:
        fm_size = get_model_size(fm, True)
        fm_latency = self._get_model_latency(fm, samples, 20, 
                                               get_model_device(fm), 20, False)
        
        master_dnn = self.init_md_from_fm_by_reducing_width(fm, reducing_width_ratio)
        master_dnn_size = get_model_size(master_dnn, True)
        logger.debug(f'inited master DNN: {master_dnn}')
        master_dnn_latency = self._get_model_latency(master_dnn, samples, 20, 
                                               get_model_device(master_dnn), 20, False)

        logger.info(f'init master DNN (w/o FBS yet) by reducing foundation model\'s width (by {reducing_width_ratio:d}x)')
        logger.info(f'foundation model ({fm_size:.3f}MB, {fm_latency:.4f}s/sample) -> '
                    f'master DNN ({master_dnn_size:.3f}MB, {master_dnn_latency:.4f}s/sample)\n'
                    f'(model size: ↓ {(fm_size / master_dnn_size):.2f}x, '
                    f'latency: ↓ {(fm_latency / master_dnn_latency):.2f}x)')
        
        return master_dnn
    
    def _get_model_latency(self, model: torch.nn.Module, model_input_size, sample_num: int, 
                           device: str, warmup_sample_num: int, return_detail=False):
        import time
        
        if isinstance(model_input_size, tuple):
            dummy_input = torch.rand(model_input_size).to(device)
        else:
            dummy_input = model_input_size
            
        model = model.to(device)
        model.eval()
        
        # warm up
        with torch.no_grad():
            for _ in range(warmup_sample_num):
                model(**dummy_input)
                
        infer_time_list = []
                
        if device == 'cuda' or 'cuda' in str(device):
            with torch.no_grad():
                for _ in range(sample_num):
                    s, e = torch.cuda.Event(enable_timing=True), torch.cuda.Event(enable_timing=True)
                    s.record()
                    model(**dummy_input)
                    e.record()
                    torch.cuda.synchronize()
                    cur_model_infer_time = s.elapsed_time(e) / 1000.
                    infer_time_list += [cur_model_infer_time]

        else:
            with torch.no_grad():
                for _ in range(sample_num):
                    start = time.time()
                    model(**dummy_input)
                    cur_model_infer_time = time.time() - start
                    infer_time_list += [cur_model_infer_time]
                    
        avg_infer_time = sum(infer_time_list) / sample_num

        if return_detail:
            return avg_infer_time, infer_time_list
        return avg_infer_time