import cv2
import math
import numpy as np
import os
import torch
from basicsr.archs.rrdbnet_arch import RRDBNet
from torch.hub import download_url_to_file, get_dir
from torch.nn import functional as F
from urllib.parse import urlparse

ROOT_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


class RealESRGANer():

    def __init__(self, scale, model_path, tile=0, tile_pad=10, pre_pad=10, half=False):
        self.scale = scale
        self.tile_size = tile
        self.tile_pad = tile_pad
        self.pre_pad = pre_pad
        self.mod_scale = None
        self.half = half

        # initialize model
        self.device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
        model = RRDBNet(num_in_ch=3, num_out_ch=3, num_feat=64, num_block=23, num_grow_ch=32, scale=scale)

        if model_path.startswith('https://'):
            model_path = load_file_from_url(
                url=model_path, model_dir='realesrgan/weights', progress=True, file_name=None)
        loadnet = torch.load(model_path)
        if 'params_ema' in loadnet:
            keyname = 'params_ema'
        else:
            keyname = 'params'
        model.load_state_dict(loadnet[keyname], strict=True)
        model.eval()
        self.model = model.to(self.device)
        if self.half:
            self.model = self.model.half()

    def pre_process(self, img):
        img = torch.from_numpy(np.transpose(img, (2, 0, 1))).float()
        self.img = img.unsqueeze(0).to(self.device)
        if self.half:
            self.img = self.img.half()

        # pre_pad
        if self.pre_pad != 0:
            self.img = F.pad(self.img, (0, self.pre_pad, 0, self.pre_pad), 'reflect')
        # mod pad
        if self.scale == 2:
            self.mod_scale = 2
        elif self.scale == 1:
            self.mod_scale = 4
        if self.mod_scale is not None:
            self.mod_pad_h, self.mod_pad_w = 0, 0
            _, _, h, w = self.img.size()
            if (h % self.mod_scale != 0):
                self.mod_pad_h = (self.mod_scale - h % self.mod_scale)
            if (w % self.mod_scale != 0):
                self.mod_pad_w = (self.mod_scale - w % self.mod_scale)
            self.img = F.pad(self.img, (0, self.mod_pad_w, 0, self.mod_pad_h), 'reflect')

    def process(self):
        self.output = self.model(self.img)

    def tile_process(self):
        """Modified from: https://github.com/ata4/esrgan-launcher
        """
        batch, channel, height, width = self.img.shape
        output_height = height * self.scale
        output_width = width * self.scale
        output_shape = (batch, channel, output_height, output_width)

        # start with black image
        self.output = self.img.new_zeros(output_shape)
        tiles_x = math.ceil(width / self.tile_size)
        tiles_y = math.ceil(height / self.tile_size)

        # loop over all tiles
        for y in range(tiles_y):
            for x in range(tiles_x):
                # extract tile from input image
                ofs_x = x * self.tile_size
                ofs_y = y * self.tile_size
                # input tile area on total image
                input_start_x = ofs_x
                input_end_x = min(ofs_x + self.tile_size, width)
                input_start_y = ofs_y
                input_end_y = min(ofs_y + self.tile_size, height)

                # input tile area on total image with padding
                input_start_x_pad = max(input_start_x - self.tile_pad, 0)
                input_end_x_pad = min(input_end_x + self.tile_pad, width)
                input_start_y_pad = max(input_start_y - self.tile_pad, 0)
                input_end_y_pad = min(input_end_y + self.tile_pad, height)

                # input tile dimensions
                input_tile_width = input_end_x - input_start_x
                input_tile_height = input_end_y - input_start_y
                tile_idx = y * tiles_x + x + 1
                input_tile = self.img[:, :, input_start_y_pad:input_end_y_pad, input_start_x_pad:input_end_x_pad]

                # upscale tile
                try:
                    with torch.no_grad():
                        output_tile = self.model(input_tile)
                except Exception as error:
                    print('Error', error)
                print(f'\tTile {tile_idx}/{tiles_x * tiles_y}')

                # output tile area on total image
                output_start_x = input_start_x * self.scale
                output_end_x = input_end_x * self.scale
                output_start_y = input_start_y * self.scale
                output_end_y = input_end_y * self.scale

                # output tile area without padding
                output_start_x_tile = (input_start_x - input_start_x_pad) * self.scale
                output_end_x_tile = output_start_x_tile + input_tile_width * self.scale
                output_start_y_tile = (input_start_y - input_start_y_pad) * self.scale
                output_end_y_tile = output_start_y_tile + input_tile_height * self.scale

                # put tile into output image
                self.output[:, :, output_start_y:output_end_y,
                            output_start_x:output_end_x] = output_tile[:, :, output_start_y_tile:output_end_y_tile,
                                                                       output_start_x_tile:output_end_x_tile]

    def post_process(self):
        # remove extra pad
        if self.mod_scale is not None:
            _, _, h, w = self.output.size()
            self.output = self.output[:, :, 0:h - self.mod_pad_h * self.scale, 0:w - self.mod_pad_w * self.scale]
        # remove prepad
        if self.pre_pad != 0:
            _, _, h, w = self.output.size()
            self.output = self.output[:, :, 0:h - self.pre_pad * self.scale, 0:w - self.pre_pad * self.scale]
        return self.output

    @torch.no_grad()
    def enhance(self, img, outscale=None, alpha_upsampler='realesrgan'):
        h_input, w_input = img.shape[0:2]
        # img: numpy
        img = img.astype(np.float32)
        if np.max(img) > 255:  # 16-bit image
            max_range = 65535
            print('\tInput is a 16-bit image')
        else:
            max_range = 255
        img = img / max_range
        if len(img.shape) == 2:  # gray image
            img_mode = 'L'
            img = cv2.cvtColor(img, cv2.COLOR_GRAY2RGB)
        elif img.shape[2] == 4:  # RGBA image with alpha channel
            img_mode = 'RGBA'
            alpha = img[:, :, 3]
            img = img[:, :, 0:3]
            img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
            if alpha_upsampler == 'realesrgan':
                alpha = cv2.cvtColor(alpha, cv2.COLOR_GRAY2RGB)
        else:
            img_mode = 'RGB'
            img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

        # ------------------- process image (without the alpha channel) ------------------- #
        self.pre_process(img)
        if self.tile_size > 0:
            self.tile_process()
        else:
            self.process()
        output_img = self.post_process()
        output_img = output_img.data.squeeze().float().cpu().clamp_(0, 1).numpy()
        output_img = np.transpose(output_img[[2, 1, 0], :, :], (1, 2, 0))
        if img_mode == 'L':
            output_img = cv2.cvtColor(output_img, cv2.COLOR_BGR2GRAY)

        # ------------------- process the alpha channel if necessary ------------------- #
        if img_mode == 'RGBA':
            if alpha_upsampler == 'realesrgan':
                self.pre_process(alpha)
                if self.tile_size > 0:
                    self.tile_process()
                else:
                    self.process()
                output_alpha = self.post_process()
                output_alpha = output_alpha.data.squeeze().float().cpu().clamp_(0, 1).numpy()
                output_alpha = np.transpose(output_alpha[[2, 1, 0], :, :], (1, 2, 0))
                output_alpha = cv2.cvtColor(output_alpha, cv2.COLOR_BGR2GRAY)
            else:
                h, w = alpha.shape[0:2]
                output_alpha = cv2.resize(alpha, (w * self.scale, h * self.scale), interpolation=cv2.INTER_LINEAR)

            # merge the alpha channel
            output_img = cv2.cvtColor(output_img, cv2.COLOR_BGR2BGRA)
            output_img[:, :, 3] = output_alpha

        # ------------------------------ return ------------------------------ #
        if max_range == 65535:  # 16-bit image
            output = (output_img * 65535.0).round().astype(np.uint16)
        else:
            output = (output_img * 255.0).round().astype(np.uint8)

        if outscale is not None and outscale != float(self.scale):
            output = cv2.resize(
                output, (
                    int(w_input * outscale),
                    int(h_input * outscale),
                ), interpolation=cv2.INTER_LANCZOS4)

        return output, img_mode


def load_file_from_url(url, model_dir=None, progress=True, file_name=None):
    """Ref:https://github.com/1adrianb/face-alignment/blob/master/face_alignment/utils.py
    """
    if model_dir is None:
        hub_dir = get_dir()
        model_dir = os.path.join(hub_dir, 'checkpoints')

    os.makedirs(os.path.join(ROOT_DIR, model_dir), exist_ok=True)

    parts = urlparse(url)
    filename = os.path.basename(parts.path)
    if file_name is not None:
        filename = file_name
    cached_file = os.path.abspath(os.path.join(ROOT_DIR, model_dir, filename))
    if not os.path.exists(cached_file):
        print(f'Downloading: "{url}" to {cached_file}\n')
        download_url_to_file(url, cached_file, hash_prefix=None, progress=progress)
    return cached_file