"""
单文件：参考深度反投影到 ECEF → 投影到 query 相机 → 并排可视化对应点。
运行: python demo.py
"""

from pathlib import Path

import cv2
import numpy as np
import pyproj
from scipy.spatial.transform import Rotation as R

# 与 poses 里帧名一致（如 888.jpg）
REF_STEM = "888"
QUERY_STEM = "1047"
NUM_SAMPLES = 100
# 内参 fx, fy, cx, cy — 需与渲染一致
FX, FY, CX, CY = 1931.7, 1931.7, 800.0, 600.0
W, H = 1600, 1200

ROOT = Path(__file__).resolve().parent
ASSETS = ROOT / "assets"
OUT = ROOT / "outputs"


def wgs84_to_ecef(lon, lat, h):
    t = pyproj.Transformer.from_crs(
        "EPSG:4326",
        {"proj": "geocent", "ellps": "WGS84", "datum": "WGS84"},
        always_xy=True,
    )
    x, y, z = t.transform(lon, lat, h, radians=False)
    return np.array([x, y, z], np.float64)


def enu_to_ecef_rot(lon, lat):
    lat_r, lon_r = np.radians(lat), np.radians(lon)
    up = np.array(
        [
            np.cos(lon_r) * np.cos(lat_r),
            np.sin(lon_r) * np.cos(lat_r),
            np.sin(lat_r),
        ]
    )
    east = np.array([-np.sin(lon_r), np.cos(lon_r), 0.0])
    north = np.cross(up, east)
    m = np.zeros((3, 3))
    m[:, 0], m[:, 1], m[:, 2] = east, north, up
    return m


def pose_to_c2w_ecef(lon, lat, alt, roll, pitch, yaw):
    r_pose = R.from_euler("xyz", [pitch, roll, yaw], degrees=True).as_matrix()
    r_enu = enu_to_ecef_rot(lon, lat)
    r_c2w = r_enu @ r_pose
    t = wgs84_to_ecef(lon, lat, alt)
    T = np.eye(4, dtype=np.float64)
    T[:3, :3] = r_c2w
    T[:3, 3] = t
    T[:3, 1] *= -1
    T[:3, 2] *= -1
    return T


def load_poses(path):
    d = {}
    for line in open(path, encoding="utf-8"):
        p = line.split()
        if p:
            d[p[0]] = list(map(float, p[1:]))
    return d


def unproject_xy_depth(xy, z, T_c2w, fx, fy, cx, cy):
    """像素 (x,y) + 深度 z → ECEF。"""
    x, y = xy[:, 0], xy[:, 1]
    z = z.astype(np.float64)
    xc = z * (x - cx) / fx
    yc = z * (y - cy) / fy
    pc = np.stack([xc, yc, z], axis=1)
    Rm, t = T_c2w[:3, :3], T_c2w[:3, 3]
    return (Rm @ pc.T).T + t


def project_ecef(pts, T_c2w, fx, fy, cx, cy):
    """ECEF → 像素 (x,y)。"""
    Rm, t = T_c2w[:3, :3], T_c2w[:3, 3]
    Rinv = Rm.T
    pc = (Rinv @ (pts - t).T).T
    z = pc[:, 2]
    u = fx * pc[:, 0] / z + cx
    v = fy * pc[:, 1] / z + cy
    return np.stack([u, v], axis=1)


def vis_side_by_side(img_l, img_r, pl, pr, out_path):
    h1, w1 = img_l.shape[:2]
    h2, w2 = img_r.shape[:2]
    pl = np.asarray(pl, dtype=np.float64)
    pr = np.asarray(pr, dtype=np.float64)
    in_l = (pl[:, 0] >= 0) & (pl[:, 0] < w1) & (pl[:, 1] >= 0) & (pl[:, 1] < h1)
    in_r = (pr[:, 0] >= 0) & (pr[:, 0] < w2) & (pr[:, 1] >= 0) & (pr[:, 1] < h2)
    m = in_l & in_r
    pl, pr = pl[m], pr[m]

    h = max(h1, h2)
    w = w1 + w2
    vis = np.zeros((h, w, 3), np.uint8)
    vis[:h1, :w1] = img_l
    vis[:h2, w1 : w1 + w2] = img_r
    for i in range(len(pl)):
        c = (int(37 * i % 255), int(91 * i % 255), int(17 * i % 255))
        x1, y1 = int(pl[i, 0]), int(pl[i, 1])
        x2, y2 = int(pr[i, 0]), int(pr[i, 1])
        cv2.circle(vis, (x1, y1), 4, c, -1)
        cv2.circle(vis, (x2 + w1, y2), 4, c, -1)
        cv2.line(vis, (x1, y1), (x2 + w1, y2), c, 2)
    OUT.mkdir(parents=True, exist_ok=True)
    cv2.imwrite(str(out_path), vis)
    print("Wrote", out_path)


def load_bgr(rgb_path, depth_path):
    im = cv2.imread(str(rgb_path))
    if im is not None:
        return im
    d = cv2.imread(str(depth_path), cv2.IMREAD_UNCHANGED)
    d = np.flipud(d[:, :, 0] if d.ndim == 3 else d).astype(np.float32)
    v = d[d > 0]
    lo, hi = (np.percentile(v, [2, 98]) if v.size else (0.0, 1.0))
    g = (np.clip((d - lo) / (hi - lo + 1e-6), 0, 1) * 255).astype(np.uint8)
    return cv2.applyColorMap(g, cv2.COLORMAP_VIRIDIS)


def main():
    pose_txt = ASSETS / "HongKong_seq2@500@30_60@cloudy.txt"
    ref_d = ASSETS / f"{REF_STEM}_1.png"
    q_rgb = ASSETS / f"{QUERY_STEM}_0.png"
    q_d = ASSETS / f"{QUERY_STEM}_1.png"

    poses = load_poses(pose_txt)
    T_ref = pose_to_c2w_ecef(*poses[f"{REF_STEM}.jpg"])
    T_q = pose_to_c2w_ecef(*poses[f"{QUERY_STEM}.jpg"])

    depth = cv2.imread(str(ref_d), cv2.IMREAD_UNCHANGED)
    depth = np.ascontiguousarray(np.flipud(depth))

    rng = np.random.default_rng(0)
    ex = rng.integers(0, W, size=NUM_SAMPLES)
    ey = rng.integers(0, H, size=NUM_SAMPLES)
    xy = np.column_stack([ex.astype(np.float64), ey.astype(np.float64)])
    z = depth[ey, ex].astype(np.float64)

    m = z > 0
    xy, z = xy[m], z[m]

    pts_ecef = unproject_xy_depth(xy, z, T_ref, FX, FY, CX, CY)
    uv_q = project_ecef(pts_ecef, T_q, FX, FY, CX, CY)

    ref_img = load_bgr(ASSETS / f"{REF_STEM}_0.png", ref_d)
    q_img = load_bgr(q_rgb, q_d)

    vis_side_by_side(q_img, ref_img, uv_q, xy, OUT / "reprojection_matches.png")


if __name__ == "__main__":
    main()