"""Interface 72: calibrated landmarks and a transparent annotation overlay."""

import math

import cv2
import numpy as np

from face_analysis.calibration import estimate_scale_factor, normalized_to_pixel
from face_analysis.special_points import detect_special_points
from hairline.face_landmarks import to_landmark_list
from hairline.framing import prepare_portrait


class AnnotationUnavailable(ValueError):
    """The image does not contain the landmarks needed for all annotations."""


def build_b_end_annotation(image):
    image, normalized, _ = prepare_portrait(image)
    height, width = image.shape[:2]
    landmarks = to_landmark_list(normalized)
    special = detect_special_points(image, landmarks_override=landmarks)["points"]

    hairline_keys = ("hair_line_center", "hair_line_left", "hair_line_left_left")
    if any(special[key] is None for key in hairline_keys):
        raise AnnotationUnavailable("未找到完整发际线，请露出额头和两侧发际线后重拍")

    px_per_cm = estimate_scale_factor(landmarks, width, height)
    if not math.isfinite(px_per_cm) or px_per_cm <= 0:
        raise AnnotationUnavailable("无法估算厘米比例，请使用清晰正面照")

    center, left, left_left = (
        (special[key]["x"], special[key]["y"]) for key in hairline_keys
    )
    points = {
        1: normalized_to_pixel(landmarks.landmark[4], width, height),
        2: center,
        3: (center[0] + 2 * px_per_cm, center[1]),
        4: left,
        5: left_left,
        6: normalized_to_pixel(landmarks.landmark[446], width, height),
    }
    if any(not (0 <= x < width and 0 <= y < height) for x, y in points.values()):
        raise AnnotationUnavailable("扶正裁切后无法保留全部标注点，请使用留有边距的照片")

    pairs = ((2, 1), (2, 3), (4, 6), (5, 6))
    measurements = {
        f"{start}-{end}": (2.0 if (start, end) == (2, 3)
                          else round(math.dist(points[start], points[end]) / px_per_cm, 1))
        for start, end in pairs
    }
    overlay = _render(points, measurements, width, height)
    data = {
        "coordinate_space": "processed_image",
        "image_size": {"width": width, "height": height},
        "points": {str(index): {"x": x, "y": y} for index, (x, y) in points.items()},
        "measurements_cm": measurements,
        "px_per_cm": px_per_cm,
    }
    return image, overlay, data


def _dashed_line(alpha, start, target, scale, *, ray, length_multiplier=1.0):
    x, y = start
    distance = math.dist(start, target)
    if distance == 0:
        return
    dx, dy = (target[0] - x) / distance, (target[1] - y) / distance
    length = distance
    if ray:
        height, width = alpha.shape
        # Fade within a bounded distance, ending sooner when the ray hits an edge.
        limits = []
        if dx:
            limits.append(((width - 1 if dx > 0 else 0) - x) / dx)
        if dy:
            limits.append(((height - 1 if dy > 0 else 0) - y) / dy)
        edge_limit = min(limits)
        length = min(min(2.5 * distance, edge_limit) * length_multiplier, edge_limit)

    dash = max(4, round(7 * scale))
    gap = max(3, round(5 * scale))
    thickness = max(1, round(1.6 * scale))
    if length <= 0:
        return

    # Separate layer so a faint crossing cannot overwrite a brighter ray.
    layer = np.zeros_like(alpha)
    for offset in range(0, math.ceil(length), dash + gap):
        end = min(offset + dash, length)
        opacity = round(255 * (1 - offset / length)) if ray else 255
        cv2.line(
            layer,
            (round(x + dx * offset), round(y + dy * offset)),
            (round(x + dx * end), round(y + dy * end)),
            opacity, thickness, cv2.LINE_AA,
        )
    np.maximum(alpha, layer, out=alpha)


def _render(points, measurements, width, height):
    scale = max(0.65, min(width, height) / 650)
    alpha = np.zeros((height, width), dtype=np.uint8)
    _dashed_line(alpha, points[2], points[1], scale, ray=True, length_multiplier=0.85)
    for start, end, ray in ((2, 3, False), (4, 6, True)):
        _dashed_line(alpha, points[start], points[end], scale, ray=ray)
    _dashed_line(alpha, points[5], points[6], scale, ray=True, length_multiplier=1.3)

    shift = 4
    subpixel = 1 << shift
    radius = round(1.4 * max(2, round(4 * scale)) * subpixel)
    for point in points.values():
        center = tuple(round(value * subpixel) for value in point)
        cv2.circle(alpha, center, radius, 255, -1, cv2.LINE_AA, shift=shift)

    font = cv2.FONT_HERSHEY_SIMPLEX
    font_scale = 0.53 * scale
    thickness = max(1, round(scale))
    gap = max(4, round(8 * scale))
    for start, end, placement in ((2, 1, "left"), (2, 3, "above"),
                                  (4, 6, "left"), (5, 6, "right")):
        a, b = points[start], points[end]
        x, y = (a[0] + b[0]) / 2, (a[1] + b[1]) / 2
        unit = " CM" if (start, end) == (2, 3) else "cm"
        label = f"{measurements[f'{start}-{end}']:.1f}{unit}"
        (text_width, text_height), baseline = cv2.getTextSize(label, font, font_scale, thickness)
        text_x = {
            "left": x - text_width - gap,
            "above": x - text_width / 2,
            "right": x + gap,
        }[placement]
        text_y = y - gap if placement == "above" else y + text_height / 2
        origin = (
            max(0, min(width - text_width, round(text_x))),
            max(text_height, min(height - baseline - 1, round(text_y))),
        )
        cv2.putText(alpha, label, origin, font, font_scale, 255, thickness, cv2.LINE_AA)

    overlay = np.full((height, width, 4), 255, dtype=np.uint8)
    overlay[:, :, 3] = alpha
    return overlay