# python3.7
"""Utility functions for visualizing results."""

import base64
import os.path
import cv2
import numpy as np
from bs4 import BeautifulSoup

__all__ = [
    'get_grid_shape', 'get_blank_image', 'load_image', 'save_image',
    'resize_image', 'postprocess_image', 'add_text_to_image',
    'parse_image_size', 'fuse_images', 'HtmlPageVisualizer', 'HtmlPageReader',
    'VideoReader', 'VideoWriter'
]


def get_grid_shape(size, row=0, col=0, is_portrait=False):
    """Gets the shape of a grid based on the size.

    This function makes greatest effort on making the output grid square if
    neither `row` nor `col` is set. If `is_portrait` is set as `False`, the
    height will always be equal to or smaller than the width. For example, if
    input `size = 16`, output shape will be `(4, 4)`; if input `size = 15`,
    output shape will be (3, 5). Otherwise, the height will always be equal to
    or larger than the width.

    Args:
        size: Size (height * width) of the target grid.
        is_portrait: Whether to return a portrait size of a landscape size.
            (default: False)

    Returns:
        A two-element tuple, representing height and width respectively.
    """
    assert isinstance(size, int)
    assert isinstance(row, int)
    assert isinstance(col, int)
    if size == 0:
        return (0, 0)

    if row > 0 and col > 0 and row * col != size:
        row = 0
        col = 0

    if row > 0 and size % row == 0:
        return (row, size // row)
    if col > 0 and size % col == 0:
        return (size // col, col)

    row = int(np.sqrt(size))
    while row > 0:
        if size % row == 0:
            col = size // row
            break
        row = row - 1

    return (col, row) if is_portrait else (row, col)


def get_blank_image(height, width, channels=3, is_black=True):
    """Gets a blank image, either white of black.

    NOTE: This function will always return an image with `RGB` channel order for
    color image and pixel range [0, 255].

    Args:
        height: Height of the returned image.
        width: Width of the returned image.
        channels: Number of channels. (default: 3)
        is_black: Whether to return a black image. (default: True)
    """
    shape = (height, width, channels)
    if is_black:
        return np.zeros(shape, dtype=np.uint8)
    return np.ones(shape, dtype=np.uint8) * 255


def load_image(path, image_channels=3):
    """Loads an image from disk.

    NOTE: This function will always return an image with `RGB` channel order for
    color image and pixel range [0, 255].

    Args:
        path: Path to load the image from.
        image_channels: Number of image channels of returned image. This field
            is employed since `cv2.imread()` will always return a 3-channel
            image, even for grayscale image.

    Returns:
        An image with dtype `np.ndarray`, or `None` if `path` does not exist.
    """
    if not os.path.isfile(path):
        return None

    assert image_channels in [1, 3]

    image = cv2.imread(path)
    assert image.ndim == 3 and image.shape[2] == 3
    if image_channels == 1:
        return image[:, :, 0:1]
    return image[:, :, ::-1]


def save_image(path, image):
    """Saves an image to disk.

    NOTE: The input image (if colorful) is assumed to be with `RGB` channel
    order and pixel range [0, 255].

    Args:
        path: Path to save the image to.
        image: Image to save.
    """
    if image is None:
        return

    assert image.ndim == 3 and image.shape[2] in [1, 3]
    cv2.imwrite(path, image[:, :, ::-1])


def resize_image(image, *args, **kwargs):
    """Resizes image.

    This is a wrap of `cv2.resize()`.

    NOTE: THe channel order of the input image will not be changed.

    Args:
        image: Image to resize.
    """
    if image is None:
        return None

    assert image.ndim == 3 and image.shape[2] in [1, 3]
    image = cv2.resize(image, *args, **kwargs)
    if image.ndim == 2:
        return image[:, :, np.newaxis]
    return image


def postprocess_image(image, min_val=-1.0, max_val=1.0, data_format='NCHW'):
    """Post-processes image to pixel range [0, 255] with dtype `uint8`.

    NOTE: The returned image will always be with `HWC` format.

    Args:
        min_val: Minimum value of the input image.
        max_val: Maximum value of the input image.
        data_format: Data format of the input image. Supporting `NCHW`, `NHWC`,
            `CHW`, `HWC`.

    Returns:
        The post-processed image.

    Raises:
        NotImplementedError: If the input `data_format` is not support.
    """
    assert isinstance(image, np.ndarray)
    image = image.astype(np.float64)
    image = (image - min_val) * 255 / (max_val - min_val)
    image = np.clip(image + 0.5, 0, 255).astype(np.uint8)
    data_format = data_format.upper()
    if data_format == 'NCHW':
        assert image.ndim == 4 and image.shape[1] in [1, 3]
        return image.transpose(0, 2, 3, 1)
    if data_format == 'NHWC':
        assert image.ndim == 4 and image.shape[3] in [1, 3]
        return image
    if data_format == 'CHW':
        assert image.ndim == 3 and image.shape[0] in [1, 3]
        return image.transpose(1, 2, 0)
    if data_format == 'HWC':
        assert image.ndim == 3 and image.shape[2] in [1, 3]
        return image
    raise NotImplementedError(f'Data format `{data_format}` is not supported!')


def add_text_to_image(image,
                      text='',
                      position=None,
                      font=cv2.FONT_HERSHEY_TRIPLEX,
                      font_size=1.0,
                      line_type=cv2.LINE_8,
                      line_width=1,
                      color=(255, 255, 255)):
    """Overlays text on given image.

    NOTE: The input image is assumed to be with `RGB` channel order.

    Args:
        image: The image to overlay text on.
        text: Text content to overlay on the image. (default: '')
        position: Target position (bottom-left corner) to add text. If not set,
            center of the image will be used by default. (default: None)
        font: Font of the text added. (default: cv2.FONT_HERSHEY_TRIPLEX)
        font_size: Font size of the text added. (default: 1.0)
        line_type: Line type used to depict the text. (default: cv2.LINE_8)
        line_width: Line width used to depict the text. (default: 1)
        color: Color of the text added in `RGB` channel order. (default:
            (255, 255, 255))

    Returns:
        An image with target text overlayed on.
    """
    if image is None or not text:
        return image

    cv2.putText(img=image,
                text=text,
                org=position,
                fontFace=font,
                fontScale=font_size,
                color=color,
                thickness=line_width,
                lineType=line_type,
                bottomLeftOrigin=False)

    return image


def parse_image_size(obj):
    """Parses object to a pair of image size, i.e., (width, height).

    Args:
        obj: The input object to parse image size from.

    Returns:
        A two-element tuple, indicating image width and height respectively.

    Raises:
        If the input is invalid, i.e., neither a list or tuple, nor a string.
    """
    if obj is None or obj == '':
        width = height = 0
    elif isinstance(obj, int):
        width = height = obj
    elif isinstance(obj, (list, tuple, np.ndarray)):
        numbers = tuple(obj)
        if len(numbers) == 0:
            width = height = 0
        elif len(numbers) == 1:
            width = height = numbers[0]
        elif len(numbers) == 2:
            width = numbers[0]
            height = numbers[1]
        else:
            raise ValueError(f'At most two elements for image size.')
    elif isinstance(obj, str):
        splits = obj.replace(' ', '').split(',')
        numbers = tuple(map(int, splits))
        if len(numbers) == 0:
            width = height = 0
        elif len(numbers) == 1:
            width = height = numbers[0]
        elif len(numbers) == 2:
            width = numbers[0]
            height = numbers[1]
        else:
            raise ValueError(f'At most two elements for image size.')
    else:
        raise ValueError(f'Invalid type of input: {type(obj)}!')

    return (max(0, width), max(0, height))


def fuse_images(images,
                image_size=None,
                row=0,
                col=0,
                is_row_major=True,
                is_portrait=False,
                row_spacing=0,
                col_spacing=0,
                border_left=0,
                border_right=0,
                border_top=0,
                border_bottom=0,
                black_background=True):
    """Fuses a collection of images into an entire image.

    Args:
        images: A collection of images to fuse. Should be with shape [num,
            height, width, channels].
        image_size: This field is used to resize the image before fusion. `0`
            disables resizing. (default: None)
        row: Number of rows used for image fusion. If not set, this field will
            be automatically assigned based on `col` and total number of images.
            (default: None)
        col: Number of columns used for image fusion. If not set, this field
            will be automatically assigned based on `row` and total number of
            images. (default: None)
        is_row_major: Whether the input images should be arranged row-major or
            column-major. (default: True)
        is_portrait: Only active when both `row` and `col` should be assigned
            automatically. (default: False)
        row_spacing: Space between rows. (default: 0)
        col_spacing: Space between columns. (default: 0)
        border_left: Width of left border. (default: 0)
        border_right: Width of right border. (default: 0)
        border_top: Width of top border. (default: 0)
        border_bottom: Width of bottom border. (default: 0)

    Returns:
        The fused image.

    Raises:
        ValueError: If the input `images` is not with shape [num, height, width,
            width].
    """
    if images is None:
        return images

    if images.ndim != 4:
        raise ValueError(f'Input `images` should be with shape [num, height, '
                         f'width, channels], but {images.shape} is received!')

    num, image_height, image_width, channels = images.shape
    width, height = parse_image_size(image_size)
    height = height or image_height
    width = width or image_width
    row, col = get_grid_shape(num, row=row, col=col, is_portrait=is_portrait)
    fused_height = (
        height * row + row_spacing * (row - 1) + border_top + border_bottom)
    fused_width = (
        width * col + col_spacing * (col - 1) + border_left + border_right)
    fused_image = get_blank_image(
        fused_height, fused_width, channels=channels, is_black=black_background)
    images = images.reshape(row, col, image_height, image_width, channels)
    if not is_row_major:
        images = images.transpose(1, 0, 2, 3, 4)

    for i in range(row):
        y = border_top + i * (height + row_spacing)
        for j in range(col):
            x = border_left + j * (width + col_spacing)
            if height != image_height or width != image_width:
                image = cv2.resize(images[i, j], (width, height))
            else:
                image = images[i, j]
            fused_image[y:y + height, x:x + width] = image

    return fused_image


def get_sortable_html_header(column_name_list, sort_by_ascending=False):
    """Gets header for sortable html page.

    Basically, the html page contains a sortable table, where user can sort the
    rows by a particular column by clicking the column head.

    Example:

    column_name_list = [name_1, name_2, name_3]
    header = get_sortable_html_header(column_name_list)
    footer = get_sortable_html_footer()
    sortable_table = ...
    html_page = header + sortable_table + footer

    Args:
        column_name_list: List of column header names.
        sort_by_ascending: Default sorting order. If set as `True`, the html
            page will be sorted by ascending order when the header is clicked
            for the first time.

    Returns:
        A string, which represents for the header for a sortable html page.
    """
    header = '\n'.join([
        '<script type="text/javascript">',
        'var column_idx;',
        'var sort_by_ascending = ' + str(sort_by_ascending).lower() + ';',
        '',
        'function sorting(tbody, column_idx){',
        '    this.column_idx = column_idx;',
        '    Array.from(tbody.rows)',
        '             .sort(compareCells)',
        '             .forEach(function(row) { tbody.appendChild(row); })',
        '    sort_by_ascending = !sort_by_ascending;',
        '}',
        '',
        'function compareCells(row_a, row_b) {',
        '    var val_a = row_a.cells[column_idx].innerText;',
        '    var val_b = row_b.cells[column_idx].innerText;',
        '    var flag = sort_by_ascending ? 1 : -1;',
        '    return flag * (val_a > val_b ? 1 : -1);',
        '}',
        '</script>',
        '',
        '<html>',
        '',
        '<head>',
        '<style>',
        '    table {',
        '        border-spacing: 0;',
        '        border: 1px solid black;',
        '    }',
        '    th {',
        '        cursor: pointer;',
        '    }',
        '    th, td {',
        '        text-align: left;',
        '        vertical-align: middle;',
        '        border-collapse: collapse;',
        '        border: 0.5px solid black;',
        '        padding: 8px;',
        '    }',
        '    tr:nth-child(even) {',
        '        background-color: #d2d2d2;',
        '    }',
        '</style>',
        '</head>',
        '',
        '<body>',
        '',
        '<table>',
        '<thead>',
        '<tr>',
        ''])
    for idx, name in enumerate(column_name_list):
        header += f'    <th onclick="sorting(tbody, {idx})">{name}</th>\n'
    header += '</tr>\n'
    header += '</thead>\n'
    header += '<tbody id="tbody">\n'

    return header


def get_sortable_html_footer():
    """Gets footer for sortable html page.

    Check function `get_sortable_html_header()` for more details.
    """
    return '</tbody>\n</table>\n\n</body>\n</html>\n'


def encode_image_to_html_str(image, image_size=None):
    """Encodes an image to html language.

    NOTE: Input image is always assumed to be with `RGB` channel order.

    Args:
        image: The input image to encode. Should be with `RGB` channel order.
        image_size: This field is used to resize the image before encoding. `0`
            disables resizing. (default: None)

    Returns:
        A string which represents the encoded image.
    """
    if image is None:
        return ''

    assert image.ndim == 3 and image.shape[2] in [1, 3]

    # Change channel order to `BGR`, which is opencv-friendly.
    image = image[:, :, ::-1]

    # Resize the image if needed.
    width, height = parse_image_size(image_size)
    if height or width:
        height = height or image.shape[0]
        width = width or image.shape[1]
        image = cv2.resize(image, (width, height))

    # Encode the image to html-format string.
    encoded_image = cv2.imencode('.jpg', image)[1].tostring()
    encoded_image_base64 = base64.b64encode(encoded_image).decode('utf-8')
    html_str = f'<img src="data:image/jpeg;base64, {encoded_image_base64}"/>'

    return html_str


def decode_html_str_to_image(html_str, image_size=None):
    """Decodes image from html.

    Args:
        html_str: Image string parsed from html.
        image_size: This field is used to resize the image after decoding. `0`
            disables resizing. (default: None)

    Returns:
        An image with `RGB` channel order.
    """
    if not html_str:
        return None

    assert isinstance(html_str, str)
    image_str = html_str.split(',')[-1]
    encoded_image = base64.b64decode(image_str)
    encoded_image_numpy = np.frombuffer(encoded_image, dtype=np.uint8)
    image = cv2.imdecode(encoded_image_numpy, flags=cv2.IMREAD_COLOR)

    # Resize the image if needed.
    width, height = parse_image_size(image_size)
    if height or width:
        height = height or image.shape[0]
        width = width or image.shape[1]
        image = cv2.resize(image, (width, height))

    return image[:, :, ::-1]


class HtmlPageVisualizer(object):
    """Defines the html page visualizer.

    This class can be used to visualize image results as html page. Basically,
    it is based on an html-format sorted table with helper functions
    `get_sortable_html_header()`, `get_sortable_html_footer()`, and
    `encode_image_to_html_str()`. To simplify the usage, specifying the
    following fields are enough to create a visualization page:

    (1) num_rows: Number of rows of the table (header-row exclusive).
    (2) num_cols: Number of columns of the table.
    (3) header contents (optional): Title of each column.

    NOTE: `grid_size` can be used to assign `num_rows` and `num_cols`
    automatically.

    Example:

    html = HtmlPageVisualizer(num_rows, num_cols)
    html.set_headers([...])
    for i in range(num_rows):
        for j in range(num_cols):
            html.set_cell(i, j, text=..., image=..., highlight=False)
    html.save('visualize.html')
    """

    def __init__(self,
                 num_rows=0,
                 num_cols=0,
                 grid_size=0,
                 is_portrait=True,
                 viz_size=None):
        if grid_size > 0:
            num_rows, num_cols = get_grid_shape(
                grid_size, row=num_rows, col=num_cols, is_portrait=is_portrait)
        assert num_rows > 0 and num_cols > 0

        self.num_rows = num_rows
        self.num_cols = num_cols
        self.viz_size = parse_image_size(viz_size)
        self.headers = ['' for _ in range(self.num_cols)]
        self.cells = [[{
            'text': '',
            'image': '',
            'highlight': False,
        } for _ in range(self.num_cols)] for _ in range(self.num_rows)]

    def set_header(self, col_idx, content):
        """Sets the content of a particular header by column index."""
        self.headers[col_idx] = content

    def set_headers(self, contents):
        """Sets the contents of all headers."""
        if isinstance(contents, str):
            contents = [contents]
        assert isinstance(contents, (list, tuple))
        assert len(contents) == self.num_cols
        for col_idx, content in enumerate(contents):
            self.set_header(col_idx, content)

    def set_cell(self, row_idx, col_idx, text='', image=None, highlight=False):
        """Sets the content of a particular cell.

        Basically, a cell contains some text as well as an image. Both text and
        image can be empty.

        Args:
            row_idx: Row index of the cell to edit.
            col_idx: Column index of the cell to edit.
            text: Text to add into the target cell. (default: None)
            image: Image to show in the target cell. Should be with `RGB`
                channel order. (default: None)
            highlight: Whether to highlight this cell. (default: False)
        """
        self.cells[row_idx][col_idx]['text'] = text
        self.cells[row_idx][col_idx]['image'] = encode_image_to_html_str(
            image, self.viz_size)
        self.cells[row_idx][col_idx]['highlight'] = bool(highlight)

    def save(self, save_path):
        """Saves the html page."""
        html = ''
        for i in range(self.num_rows):
            html += f'<tr>\n'
            for j in range(self.num_cols):
                text = self.cells[i][j]['text']
                image = self.cells[i][j]['image']
                if self.cells[i][j]['highlight']:
                    color = ' bgcolor="#FF8888"'
                else:
                    color = ''
                if text:
                    html += f'    <td{color}>{text}<br><br>{image}</td>\n'
                else:
                    html += f'    <td{color}>{image}</td>\n'
            html += f'</tr>\n'

        header = get_sortable_html_header(self.headers)
        footer = get_sortable_html_footer()

        with open(save_path, 'w') as f:
            f.write(header + html + footer)


class HtmlPageReader(object):
    """Defines the html page reader.

    This class can be used to parse results from the visualization page
    generated by `HtmlPageVisualizer`.

    Example:

    html = HtmlPageReader(html_path)
    for j in range(html.num_cols):
        header = html.get_header(j)
    for i in range(html.num_rows):
        for j in range(html.num_cols):
            text = html.get_text(i, j)
            image = html.get_image(i, j, image_size=None)
    """
    def __init__(self, html_path):
        """Initializes by loading the content from file."""
        self.html_path = html_path
        if not os.path.isfile(html_path):
            raise ValueError(f'File `{html_path}` does not exist!')

        # Load content.
        with open(html_path, 'r') as f:
            self.html = BeautifulSoup(f, 'html.parser')

        # Parse headers.
        thead = self.html.find('thead')
        headers = thead.findAll('th')
        self.headers = []
        for header in headers:
            self.headers.append(header.text)
        self.num_cols = len(self.headers)

        # Parse cells.
        tbody = self.html.find('tbody')
        rows = tbody.findAll('tr')
        self.cells = []
        for row in rows:
            cells = row.findAll('td')
            self.cells.append([])
            for cell in cells:
                self.cells[-1].append({
                    'text': cell.text,
                    'image': cell.find('img')['src'],
                })
            assert len(self.cells[-1]) == self.num_cols
        self.num_rows = len(self.cells)

    def get_header(self, j):
        """Gets header for a particular column."""
        return self.headers[j]

    def get_text(self, i, j):
        """Gets text from a particular cell."""
        return self.cells[i][j]['text']

    def get_image(self, i, j, image_size=None):
        """Gets image from a particular cell."""
        return decode_html_str_to_image(self.cells[i][j]['image'], image_size)


class VideoReader(object):
    """Defines the video reader.

    This class can be used to read frames from a given video.
    """

    def __init__(self, path):
        """Initializes the video reader by loading the video from disk."""
        if not os.path.isfile(path):
            raise ValueError(f'Video `{path}` does not exist!')

        self.path = path
        self.video = cv2.VideoCapture(path)
        assert self.video.isOpened()
        self.position = 0

        self.length = int(self.video.get(cv2.CAP_PROP_FRAME_COUNT))
        self.frame_height = int(self.video.get(cv2.CAP_PROP_FRAME_HEIGHT))
        self.frame_width = int(self.video.get(cv2.CAP_PROP_FRAME_WIDTH))
        self.fps = self.video.get(cv2.CAP_PROP_FPS)

    def __del__(self):
        """Releases the opened video."""
        self.video.release()

    def read(self, position=None):
        """Reads a certain frame.

        NOTE: The returned frame is assumed to be with `RGB` channel order.

        Args:
            position: Optional. If set, the reader will read frames from the
                exact position. Otherwise, the reader will read next frames.
                (default: None)
        """
        if position is not None and position < self.length:
            self.video.set(cv2.CAP_PROP_POS_FRAMES, position)
            self.position = position

        success, frame = self.video.read()
        self.position = self.position + 1

        return frame[:, :, ::-1] if success else None


class VideoWriter(object):
    """Defines the video writer.

    This class can be used to create a video.

    NOTE: `.avi` and `DIVX` is the most recommended codec format since it does
    not rely on other dependencies.
    """

    def __init__(self, path, frame_height, frame_width, fps=24, codec='DIVX'):
        """Creates the video writer."""
        self.path = path
        self.frame_height = frame_height
        self.frame_width = frame_width
        self.fps = fps
        self.codec = codec

        self.video = cv2.VideoWriter(filename=path,
                                     fourcc=cv2.VideoWriter_fourcc(*codec),
                                     fps=fps,
                                     frameSize=(frame_width, frame_height))

    def __del__(self):
        """Releases the opened video."""
        self.video.release()

    def write(self, frame):
        """Writes a target frame.

        NOTE: The input frame is assumed to be with `RGB` channel order.
        """
        self.video.write(frame[:, :, ::-1])