from argparse import ArgumentParser
from pathlib import Path

import cv2 as cv
import numpy as np


parser = ArgumentParser()
parser.add_argument("--input", default="input/scene.png", help="Image to scan")
parser.add_argument("--output", default="output/hough-lines.png", help="Annotated output image")
parser.add_argument("--canny-low", type=int, default=50, help="Lower Canny threshold")
parser.add_argument("--canny-high", type=int, default=150, help="Upper Canny threshold")
parser.add_argument("--votes", type=int, default=60, help="Minimum Hough accumulator votes")
parser.add_argument("--min-length", type=int, default=80, help="Minimum line segment length")
parser.add_argument("--max-gap", type=int, default=12, help="Maximum gap joined into one segment")
args = parser.parse_args()

input_path = Path(args.input)
output_path = Path(args.output)

gray = cv.imread(str(input_path), cv.IMREAD_GRAYSCALE)
color = cv.imread(str(input_path), cv.IMREAD_COLOR)
if gray is None or color is None:
    raise SystemExit(f"could not read input image: {input_path}")

blurred = cv.GaussianBlur(gray, (5, 5), 0)
edges = cv.Canny(blurred, args.canny_low, args.canny_high, apertureSize=3)

lines = cv.HoughLinesP(
    edges,
    rho=1,
    theta=np.pi / 180,
    threshold=args.votes,
    minLineLength=args.min_length,
    maxLineGap=args.max_gap,
)

segments = [] if lines is None else [line[0] for line in lines]
annotated = color.copy()

for x1, y1, x2, y2 in segments:
    cv.line(annotated, (x1, y1), (x2, y2), (0, 180, 0), 3, cv.LINE_AA)

output_path.parent.mkdir(parents=True, exist_ok=True)
if not cv.imwrite(str(output_path), annotated):
    raise SystemExit(f"could not write output image: {output_path}")

edge_pixels = int(cv.countNonZero(edges))
print(f"image size: {gray.shape[1]}x{gray.shape[0]}")
print(f"edge pixels: {edge_pixels}")
print(f"line segments: {len(segments)}")
print(f"minimum segment length: {args.min_length}")
print(f"maximum join gap: {args.max_gap}")

if segments:
    longest = max(
        segments,
        key=lambda segment: np.hypot(segment[2] - segment[0], segment[3] - segment[1]),
    )
    x1, y1, x2, y2 = longest
    length = np.hypot(x2 - x1, y2 - y1)
    print(f"longest segment: ({x1},{y1}) to ({x2},{y2}) length={length:.1f}")

print(f"wrote: {output_path}")