'''
 * Copyright (c) 2022, salesforce.com, inc.
 * All rights reserved.
 * SPDX-License-Identifier: BSD-3-Clause
 * For full license text, see LICENSE.txt file in the repo root or https://opensource.org/licenses/BSD-3-Clause
 * By Junnan Li
'''
import warnings

import pkg_resources

warnings.filterwarnings("ignore")

from blip.models.vit import VisionTransformer, interpolate_pos_embed
from blip.models.med import BertConfig, BertModel, BertLMHeadModel
from transformers import BertTokenizer

import torch
from torch import nn

import os
from urllib.parse import urlparse
from timm.models.hub import download_cached_file


class BLIP_Base(nn.Module):
    def __init__(self,
                 med_config=None,
                 image_size=224,
                 vit='base',
                 vit_grad_ckpt=False,
                 vit_ckpt_layer=0,
                 ):
        """
        Args:
            med_config (str): path for the mixture of encoder-decoder model's configuration file
            image_size (int): input image size
            vit (str): model size of vision transformer
        """
        super().__init__()

        if med_config is None: 
            med_config = os.path.join(
                os.path.dirname(os.path.dirname(__file__)), "configs", "med_config.json"
            )
        if isinstance(med_config, str):
            med_config = BertConfig.from_json_file(med_config)
        
        self.visual_encoder, vision_width = create_vit(vit, image_size, vit_grad_ckpt, vit_ckpt_layer)
        self.tokenizer = init_tokenizer()
        med_config.encoder_width = vision_width
        self.text_encoder = BertModel(config=med_config, add_pooling_layer=False)
    
    def forward(self, image, caption, mode):
        
        assert mode in ['image', 'text', 'multimodal'], "mode parameter must be image, text, or multimodal"
        text = self.tokenizer(caption, return_tensors="pt").to(image.device)
        
        if mode == 'image':
            # return image features
            image_embeds = self.visual_encoder(image)
            return image_embeds
        
        elif mode == 'text':
            # return text features
            text_output = self.text_encoder(text.input_ids, attention_mask=text.attention_mask,
                                            return_dict=True, mode='text')
            return text_output.last_hidden_state
        
        elif mode == 'multimodal':
            # return multimodel features
            image_embeds = self.visual_encoder(image)
            image_atts = torch.ones(image_embeds.size()[:-1], dtype=torch.long).to(image.device)
            
            text.input_ids[:, 0] = self.tokenizer.enc_token_id
            output = self.text_encoder(text.input_ids,
                                       attention_mask=text.attention_mask,
                                       encoder_hidden_states=image_embeds,
                                       encoder_attention_mask=image_atts,
                                       return_dict=True,
                                       )
            return output.last_hidden_state


class BLIP_Decoder(nn.Module):
    def __init__(self,
                 med_config='configs/med_config.json',
                 image_size=384,
                 vit='base',
                 vit_grad_ckpt=False,
                 vit_ckpt_layer=0,
                 prompt='a picture of ',
                 ):
        """
        Args:
            med_config (str): path for the mixture of encoder-decoder model's configuration file
            image_size (int): input image size
            vit (str): model size of vision transformer
        """
        super().__init__()
        
        self.visual_encoder, vision_width = create_vit(vit, image_size, vit_grad_ckpt, vit_ckpt_layer)
        self.tokenizer = init_tokenizer()
        med_config = BertConfig.from_json_file(med_config)
        med_config.encoder_width = vision_width
        self.text_decoder = BertLMHeadModel(config=med_config)
        
        self.prompt = prompt
        self.prompt_length = len(self.tokenizer(self.prompt).input_ids) - 1
    
    def forward(self, image, caption):
        
        image_embeds = self.visual_encoder(image)
        image_atts = torch.ones(image_embeds.size()[:-1], dtype=torch.long).to(image.device)
        
        text = self.tokenizer(caption, padding='longest', truncation=True, max_length=40, return_tensors="pt").to(image.device)
        
        text.input_ids[:, 0] = self.tokenizer.bos_token_id
        
        decoder_targets = text.input_ids.masked_fill(text.input_ids == self.tokenizer.pad_token_id, -100)
        decoder_targets[:, :self.prompt_length] = -100
        
        decoder_output = self.text_decoder(text.input_ids,
                                           attention_mask=text.attention_mask,
                                           encoder_hidden_states=image_embeds,
                                           encoder_attention_mask=image_atts,
                                           labels=decoder_targets,
                                           return_dict=True,
                                           )
        loss_lm = decoder_output.loss
        
        return loss_lm
    
    def generate(self, image, sample=False, num_beams=3, max_length=30, min_length=10, top_p=0.9, repetition_penalty=1.0):
        image_embeds = self.visual_encoder(image)
        
        if not sample:
            image_embeds = image_embeds.repeat_interleave(num_beams, dim=0)
        
        image_atts = torch.ones(image_embeds.size()[:-1], dtype=torch.long).to(image.device)
        model_kwargs = {"encoder_hidden_states": image_embeds, "encoder_attention_mask": image_atts}
        
        prompt = [self.prompt] * image.size(0)
        input_ids = self.tokenizer(prompt, return_tensors="pt").input_ids.to(image.device)
        input_ids[:, 0] = self.tokenizer.bos_token_id
        input_ids = input_ids[:, :-1]
        
        if sample:
            #nucleus sampling
            outputs = self.text_decoder.generate(input_ids=input_ids,
                                                 max_length=max_length,
                                                 min_length=min_length,
                                                 do_sample=True,
                                                 top_p=top_p,
                                                 num_return_sequences=1,
                                                 eos_token_id=self.tokenizer.sep_token_id,
                                                 pad_token_id=self.tokenizer.pad_token_id,
                                                 repetition_penalty=1.1,
                                                 **model_kwargs)
        else:
            #beam search
            outputs = self.text_decoder.generate(input_ids=input_ids,
                                                 max_length=max_length,
                                                 min_length=min_length,
                                                 num_beams=num_beams,
                                                 eos_token_id=self.tokenizer.sep_token_id,
                                                 pad_token_id=self.tokenizer.pad_token_id,
                                                 repetition_penalty=repetition_penalty,
                                                 **model_kwargs)
        
        captions = []
        for output in outputs:
            caption = self.tokenizer.decode(output, skip_special_tokens=True)
            captions.append(caption[len(self.prompt):])
        return captions


def blip_decoder(pretrained='', **kwargs):
    model = BLIP_Decoder(**kwargs)
    if pretrained:
        model, msg = load_checkpoint(model, pretrained)
        assert (len(msg.missing_keys) == 0)
    return model


def blip_feature_extractor(pretrained='', **kwargs):
    model = BLIP_Base(**kwargs)
    if pretrained:
        model, msg = load_checkpoint(model, pretrained)
        assert (len(msg.missing_keys) == 0)
    return model


def init_tokenizer():
    tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')
    tokenizer.add_special_tokens({'bos_token': '[DEC]'})
    tokenizer.add_special_tokens({'additional_special_tokens': ['[ENC]']})
    tokenizer.enc_token_id = tokenizer.additional_special_tokens_ids[0]
    return tokenizer


def create_vit(vit, image_size, use_grad_checkpointing=False, ckpt_layer=0, drop_path_rate=0):
    assert vit in ['base', 'large'], "vit parameter must be base or large"
    if vit == 'base':
        vision_width = 768
        visual_encoder = VisionTransformer(img_size=image_size, patch_size=16, embed_dim=vision_width, depth=12,
                                           num_heads=12, use_grad_checkpointing=use_grad_checkpointing, ckpt_layer=ckpt_layer,
                                           drop_path_rate=0 or drop_path_rate
                                           )
    elif vit == 'large':
        vision_width = 1024
        visual_encoder = VisionTransformer(img_size=image_size, patch_size=16, embed_dim=vision_width, depth=24,
                                           num_heads=16, use_grad_checkpointing=use_grad_checkpointing, ckpt_layer=ckpt_layer,
                                           drop_path_rate=0.1 or drop_path_rate
                                           )
    return visual_encoder, vision_width


def is_url(url_or_filename):
    parsed = urlparse(url_or_filename)
    return parsed.scheme in ("http", "https")


def load_checkpoint(model, url_or_filename):
    if is_url(url_or_filename):
        cached_file = download_cached_file(url_or_filename, check_hash=False, progress=True)
        checkpoint = torch.load(cached_file, map_location='cpu')
    elif os.path.isfile(url_or_filename):
        checkpoint = torch.load(url_or_filename, map_location='cpu')
    else:
        raise RuntimeError('checkpoint url or path is invalid')
    
    state_dict = checkpoint['model']
    
    state_dict['visual_encoder.pos_embed'] = interpolate_pos_embed(state_dict['visual_encoder.pos_embed'], model.visual_encoder)
    if 'visual_encoder_m.pos_embed' in model.state_dict().keys():
        state_dict['visual_encoder_m.pos_embed'] = interpolate_pos_embed(state_dict['visual_encoder_m.pos_embed'],
                                                                         model.visual_encoder_m)
    for key in model.state_dict().keys():
        if key in state_dict.keys():
            if state_dict[key].shape != model.state_dict()[key].shape:
                del state_dict[key]
    
    msg = model.load_state_dict(state_dict, strict=False)
    print('load checkpoint from %s' % url_or_filename)
    return model, msg
