# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
#
# 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.

import paddle
import paddle.nn.functional as F
from base_model import SemanticIndexBase


class SemanticIndexHardestNeg(SemanticIndexBase):
    def __init__(self, pretrained_model, dropout=None, margin=0.3, output_emb_size=None):
        super().__init__(pretrained_model, dropout, output_emb_size)
        self.margin = margin

    def forward(
        self,
        query_input_ids,
        title_input_ids,
        query_token_type_ids=None,
        query_position_ids=None,
        query_attention_mask=None,
        title_token_type_ids=None,
        title_position_ids=None,
        title_attention_mask=None,
    ):

        query_cls_embedding = self.get_pooled_embedding(
            query_input_ids, query_token_type_ids, query_position_ids, query_attention_mask
        )

        title_cls_embedding = self.get_pooled_embedding(
            title_input_ids, title_token_type_ids, title_position_ids, title_attention_mask
        )

        cosine_sim = paddle.matmul(query_cls_embedding, title_cls_embedding, transpose_y=True)

        pos_sim = paddle.max(cosine_sim, axis=-1)

        # subtract 10000 from all diagonal elements of cosine_sim
        mask_score = paddle.full(
            shape=[query_cls_embedding.shape[0]], fill_value=10000, dtype=paddle.get_default_dtype()
        )
        tmp_cosine_sim = cosine_sim - paddle.diag(mask_score)
        hardest_negative_sim = paddle.max(tmp_cosine_sim, axis=-1)

        labels = paddle.full(shape=[query_cls_embedding.shape[0]], fill_value=1.0, dtype="float32")

        loss = F.margin_ranking_loss(pos_sim, hardest_negative_sim, labels, margin=self.margin)
        return loss
