#!/usr/bin/env python
# -*- coding: utf-8 -*-
# File: model.py

import tensorflow as tf
from tensorpack.tfutils import get_current_tower_context
from tensorpack.tfutils.summary import add_moving_summary
from tensorpack.tfutils.argscope import argscope
from tensorpack.tfutils.scope_utils import under_name_scope
from tensorpack.models import (
    Conv2D, FullyConnected, GlobalAvgPooling, layer_register, Conv2DTranspose)

from utils.box_ops import pairwise_iou
import config


@under_name_scope()
def clip_boxes(boxes, window, name=None):
    """
    Args:
        boxes: nx4, xyxy
        window: [h, w]
    """
    boxes = tf.maximum(boxes, 0.0)
    m = tf.tile(tf.reverse(window, [0]), [2])    # (4,)
    boxes = tf.minimum(boxes, tf.to_float(m), name=name)
    return boxes


@layer_register(log_shape=True)
def rpn_head(featuremap, channel, num_anchors):
    """
    Returns:
        label_logits: fHxfWxNA
        box_logits: fHxfWxNAx4
    """
    with argscope(Conv2D, data_format='channels_first',
                  kernel_initializer=tf.random_normal_initializer(stddev=0.01)):
        hidden = Conv2D('conv0', featuremap, channel, 3, activation=tf.nn.relu)

        label_logits = Conv2D('class', hidden, num_anchors, 1)
        box_logits = Conv2D('box', hidden, 4 * num_anchors, 1)
        # 1, NA(*4), im/16, im/16 (NCHW)

        label_logits = tf.transpose(label_logits, [0, 2, 3, 1])  # 1xfHxfWxNA
        label_logits = tf.squeeze(label_logits, 0)  # fHxfWxNA

        shp = tf.shape(box_logits)  # 1x(NAx4)xfHxfW
        box_logits = tf.transpose(box_logits, [0, 2, 3, 1])  # 1xfHxfWx(NAx4)
        box_logits = tf.reshape(box_logits, tf.stack([shp[2], shp[3], num_anchors, 4]))  # fHxfWxNAx4
    return label_logits, box_logits


@under_name_scope()
def rpn_losses(anchor_labels, anchor_boxes, label_logits, box_logits):
    """
    Args:
        anchor_labels: fHxfWxNA
        anchor_boxes: fHxfWxNAx4, encoded
        label_logits:  fHxfWxNA
        box_logits: fHxfWxNAx4

    Returns:
        label_loss, box_loss
    """
    with tf.device('/cpu:0'):
        valid_mask = tf.stop_gradient(tf.not_equal(anchor_labels, -1))
        pos_mask = tf.stop_gradient(tf.equal(anchor_labels, 1))
        nr_valid = tf.stop_gradient(tf.count_nonzero(valid_mask, dtype=tf.int32), name='num_valid_anchor')
        nr_pos = tf.count_nonzero(pos_mask, dtype=tf.int32, name='num_pos_anchor')

        valid_anchor_labels = tf.boolean_mask(anchor_labels, valid_mask)
    valid_label_logits = tf.boolean_mask(label_logits, valid_mask)

    with tf.name_scope('label_metrics'):
        valid_label_prob = tf.nn.sigmoid(valid_label_logits)
        summaries = []
        with tf.device('/cpu:0'):
            for th in [0.5, 0.2, 0.1]:
                valid_prediction = tf.cast(valid_label_prob > th, tf.int32)
                nr_pos_prediction = tf.reduce_sum(valid_prediction, name='num_pos_prediction')
                pos_prediction_corr = tf.count_nonzero(
                    tf.logical_and(
                        valid_label_prob > th,
                        tf.equal(valid_prediction, valid_anchor_labels)),
                    dtype=tf.int32)
                summaries.append(tf.truediv(
                    pos_prediction_corr,
                    nr_pos, name='recall_th{}'.format(th)))
                precision = tf.to_float(tf.truediv(pos_prediction_corr, nr_pos_prediction))
                precision = tf.where(tf.equal(nr_pos_prediction, 0), 0.0, precision, name='precision_th{}'.format(th))
                summaries.append(precision)
        add_moving_summary(*summaries)

    label_loss = tf.nn.sigmoid_cross_entropy_with_logits(
        labels=tf.to_float(valid_anchor_labels), logits=valid_label_logits)
    label_loss = tf.reduce_mean(label_loss, name='label_loss')

    pos_anchor_boxes = tf.boolean_mask(anchor_boxes, pos_mask)
    pos_box_logits = tf.boolean_mask(box_logits, pos_mask)
    delta = 1.0 / 9
    box_loss = tf.losses.huber_loss(
        pos_anchor_boxes, pos_box_logits, delta=delta,
        reduction=tf.losses.Reduction.SUM) / delta
    box_loss = tf.div(
        box_loss,
        tf.cast(nr_valid, tf.float32), name='box_loss')

    add_moving_summary(label_loss, box_loss, nr_valid, nr_pos)
    return label_loss, box_loss


@under_name_scope()
def decode_bbox_target(box_predictions, anchors):
    """
    Args:
        box_predictions: (..., 4), logits
        anchors: (..., 4), floatbox. Must have the same shape

    Returns:
        box_decoded: (..., 4), float32. With the same shape.
    """
    orig_shape = tf.shape(anchors)
    box_pred_txtytwth = tf.reshape(box_predictions, (-1, 2, 2))
    box_pred_txty, box_pred_twth = tf.split(box_pred_txtytwth, 2, axis=1)
    # each is (...)x1x2
    anchors_x1y1x2y2 = tf.reshape(anchors, (-1, 2, 2))
    anchors_x1y1, anchors_x2y2 = tf.split(anchors_x1y1x2y2, 2, axis=1)

    waha = anchors_x2y2 - anchors_x1y1
    xaya = (anchors_x2y2 + anchors_x1y1) * 0.5

    wbhb = tf.exp(tf.minimum(
        box_pred_twth, config.BBOX_DECODE_CLIP)) * waha
    xbyb = box_pred_txty * waha + xaya
    x1y1 = xbyb - wbhb * 0.5
    x2y2 = xbyb + wbhb * 0.5    # (...)x1x2
    out = tf.concat([x1y1, x2y2], axis=-2)
    return tf.reshape(out, orig_shape)


@under_name_scope()
def encode_bbox_target(boxes, anchors):
    """
    Args:
        boxes: (..., 4), float32
        anchors: (..., 4), float32

    Returns:
        box_encoded: (..., 4), float32 with the same shape.
    """
    anchors_x1y1x2y2 = tf.reshape(anchors, (-1, 2, 2))
    anchors_x1y1, anchors_x2y2 = tf.split(anchors_x1y1x2y2, 2, axis=1)
    waha = anchors_x2y2 - anchors_x1y1
    xaya = (anchors_x2y2 + anchors_x1y1) * 0.5

    boxes_x1y1x2y2 = tf.reshape(boxes, (-1, 2, 2))
    boxes_x1y1, boxes_x2y2 = tf.split(boxes_x1y1x2y2, 2, axis=1)
    wbhb = boxes_x2y2 - boxes_x1y1
    xbyb = (boxes_x2y2 + boxes_x1y1) * 0.5

    # Note that here not all boxes are valid. Some may be zero
    txty = (xbyb - xaya) / waha
    twth = tf.log(wbhb / waha)  # may contain -inf for invalid boxes
    encoded = tf.concat([txty, twth], axis=1)  # (-1x2x2)
    return tf.reshape(encoded, tf.shape(boxes))


@under_name_scope()
def generate_rpn_proposals(boxes, scores, img_shape):
    """
    Args:
        boxes: nx4 float dtype, decoded to floatbox already
        scores: n float, the logits
        img_shape: [h, w]

    Returns:
        boxes: kx4 float
        scores: k logits
    """
    assert boxes.shape.ndims == 2, boxes.shape
    if get_current_tower_context().is_training:
        PRE_NMS_TOPK = config.TRAIN_PRE_NMS_TOPK
        POST_NMS_TOPK = config.TRAIN_POST_NMS_TOPK
    else:
        PRE_NMS_TOPK = config.TEST_PRE_NMS_TOPK
        POST_NMS_TOPK = config.TEST_POST_NMS_TOPK

    topk = tf.minimum(PRE_NMS_TOPK, tf.size(scores))
    topk_scores, topk_indices = tf.nn.top_k(scores, k=topk, sorted=False)
    topk_boxes = tf.gather(boxes, topk_indices)
    topk_boxes = clip_boxes(topk_boxes, img_shape)

    topk_boxes_x1y1x2y2 = tf.reshape(topk_boxes, (-1, 2, 2))
    topk_boxes_x1y1, topk_boxes_x2y2 = tf.split(topk_boxes_x1y1x2y2, 2, axis=1)
    # nx1x2 each
    wbhb = tf.squeeze(topk_boxes_x2y2 - topk_boxes_x1y1, axis=1)
    valid = tf.reduce_all(wbhb > config.RPN_MIN_SIZE, axis=1)  # n,
    topk_valid_boxes_x1y1x2y2 = tf.boolean_mask(topk_boxes_x1y1x2y2, valid)
    topk_valid_scores = tf.boolean_mask(topk_scores, valid)

    topk_valid_boxes_y1x1y2x2 = tf.reshape(
        tf.reverse(topk_valid_boxes_x1y1x2y2, axis=[2]),
        (-1, 4), name='nms_input_boxes')
    nms_indices = tf.image.non_max_suppression(
        topk_valid_boxes_y1x1y2x2,
        topk_valid_scores,
        max_output_size=POST_NMS_TOPK,
        iou_threshold=config.RPN_PROPOSAL_NMS_THRESH)

    topk_valid_boxes = tf.reshape(topk_valid_boxes_x1y1x2y2, (-1, 4))
    final_boxes = tf.gather(
        topk_valid_boxes,
        nms_indices, name='boxes')
    final_scores = tf.gather(topk_valid_scores, nms_indices, name='scores')
    tf.sigmoid(final_scores, name='probs')  # for visualization
    return final_boxes, final_scores


@under_name_scope()
def proposal_metrics(iou):
    """
    Add summaries for RPN proposals.

    Args:
        iou: nxm, #proposal x #gt
    """
    # find best roi for each gt, for summary only
    best_iou = tf.reduce_max(iou, axis=0)
    mean_best_iou = tf.reduce_mean(best_iou, name='best_iou_per_gt')
    summaries = [mean_best_iou]
    with tf.device('/cpu:0'):
        for th in [0.3, 0.5]:
            recall = tf.truediv(
                tf.count_nonzero(best_iou >= th),
                tf.size(best_iou, out_type=tf.int64),
                name='recall_iou{}'.format(th))
            summaries.append(recall)
    add_moving_summary(*summaries)


@under_name_scope()
def sample_fast_rcnn_targets(boxes, gt_boxes, gt_labels):
    """
    Sample some ROIs from all proposals for training.

    Args:
        boxes: nx4 region proposals, floatbox
        gt_boxes: mx4, floatbox
        gt_labels: m, int32

    Returns:
        sampled_boxes: tx4 floatbox, the rois
        sampled_labels: t labels, in [0, #class-1]. Positive means foreground.
        fg_inds_wrt_gt: #fg indices, each in range [0, m-1].
            It contains the matching GT of each foreground roi.
    """
    iou = pairwise_iou(boxes, gt_boxes)     # nxm
    proposal_metrics(iou)

    # add ground truth as proposals as well
    boxes = tf.concat([boxes, gt_boxes], axis=0)    # (n+m) x 4
    iou = tf.concat([iou, tf.eye(tf.shape(gt_boxes)[0])], axis=0)   # (n+m) x m
    # #proposal=n+m from now on

    def sample_fg_bg(iou):
        fg_mask = tf.reduce_max(iou, axis=1) >= config.FASTRCNN_FG_THRESH

        fg_inds = tf.reshape(tf.where(fg_mask), [-1])
        num_fg = tf.minimum(int(
            config.FASTRCNN_BATCH_PER_IM * config.FASTRCNN_FG_RATIO),
            tf.size(fg_inds), name='num_fg')
        fg_inds = tf.random_shuffle(fg_inds)[:num_fg]

        bg_inds = tf.reshape(tf.where(tf.logical_not(fg_mask)), [-1])
        num_bg = tf.minimum(
            config.FASTRCNN_BATCH_PER_IM - num_fg,
            tf.size(bg_inds), name='num_bg')
        bg_inds = tf.random_shuffle(bg_inds)[:num_bg]

        add_moving_summary(num_fg, num_bg)
        return fg_inds, bg_inds

    fg_inds, bg_inds = sample_fg_bg(iou)
    # fg,bg indices w.r.t proposals

    best_iou_ind = tf.argmax(iou, axis=1)   # #proposal, each in 0~m-1
    fg_inds_wrt_gt = tf.gather(best_iou_ind, fg_inds)   # num_fg

    all_indices = tf.concat([fg_inds, bg_inds], axis=0)   # indices w.r.t all n+m proposal boxes
    ret_boxes = tf.gather(boxes, all_indices, name='sampled_proposal_boxes')

    ret_labels = tf.concat(
        [tf.gather(gt_labels, fg_inds_wrt_gt),
         tf.zeros_like(bg_inds, dtype=tf.int64)], axis=0, name='sampled_labels')
    # stop the gradient -- they are meant to be ground-truth
    return tf.stop_gradient(ret_boxes), tf.stop_gradient(ret_labels), fg_inds_wrt_gt


@under_name_scope()
def crop_and_resize(image, boxes, box_ind, crop_size):
    """
    Better-aligned version of tf.image.crop_and_resize, following our definition of floating point boxes.

    Args:
        image: NCHW
        boxes: nx4, x1y1x2y2
        box_ind: (n,)
        crop_size (int):
    Returns:
        n,C,size,size
    """
    assert isinstance(crop_size, int), crop_size

    @under_name_scope()
    def transform_fpcoor_for_tf(boxes, image_shape, crop_shape):
        """
        The way tf.image.crop_and_resize works (with normalized box):
        Initial point (the value of output[0]): x0_box * (W_img - 1)
        Spacing: w_box * (W_img - 1) / (W_crop - 1)
        Use the above grid to bilinear sample.

        However, what we want is (with fpcoor box):
        Spacing: w_box / W_crop
        Initial point: x0_box + spacing/2 - 0.5
        (-0.5 because bilinear sample assumes floating point coordinate (0.0, 0.0) is the same as pixel value (0, 0))

        This function transform fpcoor boxes to a format to be used by tf.image.crop_and_resize

        Returns:
            y1x1y2x2
        """
        x0, y0, x1, y1 = tf.split(boxes, 4, axis=1)

        spacing_w = (x1 - x0) / tf.to_float(crop_shape[1])
        spacing_h = (y1 - y0) / tf.to_float(crop_shape[0])

        nx0 = (x0 + spacing_w / 2 - 0.5) / tf.to_float(image_shape[1] - 1)
        ny0 = (y0 + spacing_h / 2 - 0.5) / tf.to_float(image_shape[0] - 1)

        nw = spacing_w * tf.to_float(crop_shape[1] - 1) / tf.to_float(image_shape[1] - 1)
        nh = spacing_h * tf.to_float(crop_shape[0] - 1) / tf.to_float(image_shape[0] - 1)

        return tf.concat([ny0, nx0, ny0 + nh, nx0 + nw], axis=1)

    image_shape = tf.shape(image)[2:]
    boxes = transform_fpcoor_for_tf(boxes, image_shape, [crop_size, crop_size])
    image = tf.transpose(image, [0, 2, 3, 1])   # 1hwc
    ret = tf.image.crop_and_resize(
        image, boxes, box_ind,
        crop_size=[crop_size, crop_size])
    ret = tf.transpose(ret, [0, 3, 1, 2])   # ncss
    return ret


@under_name_scope()
def roi_align(featuremap, boxes, output_shape):
    """
    Args:
        featuremap: 1xCxHxW
        boxes: Nx4 floatbox
        output_shape: int

    Returns:
        NxCxoHxoW
    """
    boxes = tf.stop_gradient(boxes)  # TODO
    # sample 4 locations per roi bin
    ret = crop_and_resize(
        featuremap, boxes,
        tf.zeros([tf.shape(boxes)[0]], dtype=tf.int32),
        output_shape * 2)
    ret = tf.nn.avg_pool(ret, [1, 1, 2, 2], [1, 1, 2, 2], padding='SAME', data_format='NCHW')
    return ret


@layer_register(log_shape=True)
def fastrcnn_head(feature, num_classes):
    """
    Args:
        feature (NxCx7x7):
        num_classes(int): num_category + 1

    Returns:
        cls_logits (Nxnum_class), reg_logits (Nx num_class-1 x 4)
    """
    feature = GlobalAvgPooling('gap', feature, data_format='channels_first')
    classification = FullyConnected(
        'class', feature, num_classes,
        kernel_initializer=tf.random_normal_initializer(stddev=0.01))
    box_regression = FullyConnected(
        'box', feature, (num_classes - 1) * 4,
        kernel_initializer=tf.random_normal_initializer(stddev=0.001))
    box_regression = tf.reshape(box_regression, (-1, num_classes - 1, 4))
    return classification, box_regression


@under_name_scope()
def fastrcnn_losses(labels, label_logits, fg_boxes, fg_box_logits):
    """
    Args:
        labels: n,
        label_logits: nxC
        fg_boxes: nfgx4, encoded
        fg_box_logits: nfgx(C-1)x4
    """
    label_loss = tf.nn.sparse_softmax_cross_entropy_with_logits(
        labels=labels, logits=label_logits)
    label_loss = tf.reduce_mean(label_loss, name='label_loss')

    fg_inds = tf.where(labels > 0)[:, 0]
    fg_labels = tf.gather(labels, fg_inds)
    num_fg = tf.size(fg_inds)
    indices = tf.stack(
        [tf.range(num_fg),
         tf.to_int32(fg_labels) - 1], axis=1)  # #fgx2
    fg_box_logits = tf.gather_nd(fg_box_logits, indices)

    with tf.name_scope('label_metrics'), tf.device('/cpu:0'):
        prediction = tf.argmax(label_logits, axis=1, name='label_prediction')
        correct = tf.to_float(tf.equal(prediction, labels))  # boolean/integer gather is unavailable on GPU
        accuracy = tf.reduce_mean(correct, name='accuracy')
        fg_label_pred = tf.argmax(tf.gather(label_logits, fg_inds), axis=1)
        num_zero = tf.reduce_sum(tf.to_int32(tf.equal(fg_label_pred, 0)), name='num_zero')
        false_negative = tf.truediv(num_zero, num_fg, name='false_negative')
        fg_accuracy = tf.reduce_mean(
            tf.gather(correct, fg_inds), name='fg_accuracy')

    box_loss = tf.losses.huber_loss(
        fg_boxes, fg_box_logits, reduction=tf.losses.Reduction.SUM)
    box_loss = tf.truediv(
        box_loss, tf.to_float(tf.shape(labels)[0]), name='box_loss')

    add_moving_summary(label_loss, box_loss, accuracy, fg_accuracy, false_negative)
    return label_loss, box_loss


@under_name_scope()
def fastrcnn_predictions(boxes, probs):
    """
    Generate final results from predictions of all proposals.

    Args:
        boxes: n#catx4 floatbox in float32
        probs: nx#class
    """
    assert boxes.shape[1] == config.NUM_CLASS - 1
    assert probs.shape[1] == config.NUM_CLASS
    boxes = tf.transpose(boxes, [1, 0, 2])  # #catxnx4
    probs = tf.transpose(probs[:, 1:], [1, 0])  # #catxn

    def f(X):
        """
        prob: n probabilities
        box: nx4 boxes

        Returns: n boolean, the selection
        """
        prob, box = X
        output_shape = tf.shape(prob)
        # filter by score threshold
        ids = tf.reshape(tf.where(prob > config.RESULT_SCORE_THRESH), [-1])
        prob = tf.gather(prob, ids)
        box = tf.gather(box, ids)
        # NMS within each class
        selection = tf.image.non_max_suppression(
            box, prob, config.RESULTS_PER_IM, config.FASTRCNN_NMS_THRESH)
        selection = tf.to_int32(tf.gather(ids, selection))
        # sort available in TF>1.4.0
        # sorted_selection = tf.contrib.framework.sort(selection, direction='ASCENDING')
        sorted_selection = -tf.nn.top_k(-selection, k=tf.size(selection))[0]
        mask = tf.sparse_to_dense(
            sparse_indices=sorted_selection,
            output_shape=output_shape,
            sparse_values=True,
            default_value=False)
        return mask

    masks = tf.map_fn(f, (probs, boxes), dtype=tf.bool,
                      parallel_iterations=10)     # #cat x N
    selected_indices = tf.where(masks)  # #selection x 2, each is (cat_id, box_id)
    probs = tf.boolean_mask(probs, masks)

    # filter again by sorting scores
    topk_probs, topk_indices = tf.nn.top_k(
        probs,
        tf.minimum(config.RESULTS_PER_IM, tf.size(probs)),
        sorted=False)
    filtered_selection = tf.gather(selected_indices, topk_indices)
    filtered_selection = tf.reverse(filtered_selection, axis=[1], name='filtered_indices')
    return filtered_selection, topk_probs


@layer_register(log_shape=True)
def maskrcnn_head(feature, num_class):
    """
    Args:
        feature (NxCx7x7):
        num_classes(int): num_category + 1

    Returns:
        mask_logits (N x num_category x 14 x 14):
    """
    with argscope([Conv2D, Conv2DTranspose], data_format='channels_first',
                  kernel_initializer=tf.variance_scaling_initializer(
                      scale=2.0, mode='fan_out', distribution='normal')):
        # c2's MSRAFill is fan_out
        l = Conv2DTranspose('deconv', feature, 256, 2, strides=2, activation=tf.nn.relu)
        l = Conv2D('conv', l, num_class - 1, 1)
    return l


@under_name_scope()
def maskrcnn_loss(mask_logits, fg_labels, fg_target_masks):
    """
    Args:
        mask_logits: #fg x #category x14x14
        fg_labels: #fg, in 1~#class
        fg_target_masks: #fgx14x14, int
    """
    num_fg = tf.size(fg_labels)
    indices = tf.stack([tf.range(num_fg), tf.to_int32(fg_labels) - 1], axis=1)  # #fgx2
    mask_logits = tf.gather_nd(mask_logits, indices)  # #fgx14x14
    mask_probs = tf.sigmoid(mask_logits)

    # add some training visualizations to tensorboard
    with tf.name_scope('mask_viz'):
        viz = tf.concat([fg_target_masks, mask_probs], axis=1)
        viz = tf.expand_dims(viz, 3)
        viz = tf.cast(viz * 255, tf.uint8, name='viz')
        tf.summary.image('mask_truth|pred', viz, max_outputs=10)

    loss = tf.nn.sigmoid_cross_entropy_with_logits(
        labels=fg_target_masks, logits=mask_logits)
    loss = tf.reduce_mean(loss, name='maskrcnn_loss')

    pred_label = mask_probs > 0.5
    truth_label = fg_target_masks > 0.5
    accuracy = tf.reduce_mean(
        tf.to_float(tf.equal(pred_label, truth_label)),
        name='accuracy')
    pos_accuracy = tf.logical_and(
        tf.equal(pred_label, truth_label),
        tf.equal(truth_label, True))
    pos_accuracy = tf.reduce_mean(tf.to_float(pos_accuracy), name='pos_accuracy')
    fg_pixel_ratio = tf.reduce_mean(tf.to_float(truth_label), name='fg_pixel_ratio')

    add_moving_summary(loss, accuracy, fg_pixel_ratio, pos_accuracy)
    return loss


if __name__ == '__main__':
    """
    Demonstrate what's wrong with tf.image.crop_and_resize:
    """
    import numpy as np
    import tensorflow.contrib.eager as tfe
    tfe.enable_eager_execution()

    # want to crop 2x2 out of a 5x5 image, and resize to 4x4
    image = np.arange(25).astype('float32').reshape(5, 5)
    boxes = np.asarray([[1, 1, 3, 3]], dtype='float32')
    target = 4

    print(crop_and_resize(
        image[None, None, :, :], boxes, [0], target)[0][0])
    """
    Expected values:
    4.5 5 5.5 6
    7 7.5 8 8.5
    9.5 10 10.5 11
    12 12.5 13 13.5
    Our implementation is not perfect either. When boxes are on the border of
    images, TF pads zeros instead of border values. But this rarely happens so it's fine.

    You cannot easily get the above results with tf.image.crop_and_resize.
    Try out yourself here:
    """
    print(tf.image.crop_and_resize(
        image[None, :, :, None],
        np.asarray([[1, 1, 2, 2]]) / 4.0, [0], [target, target])[0][:, :, 0])
