#!/usr/bin/env python3
"""Encode a nicer DEMO clip with the deterministic integer inter-frame codec
(`wai.video.int_motion`) for the in-browser player: two bouncing discs over a
gradient, 128x128. Same codec as the committed conformance vector (integer block
MC + quantized residual + rANS); this is just a bigger, livelier clip to serve.

  python tools/wai_int_video_demo_encode.py <out-dir>
"""
import sys, os, json, base64
import numpy as np
from compressai.ans import RansEncoder

H = W = 128
NF, BLOCK, SEARCH, Q = 16, 16, 6, 6
RMAX = (255 + Q - 1) // Q


def fnv1a(buf):
    h = 14695981039346656037
    for b in buf:
        h = ((h ^ b) * 1099511628211) & 0xFFFFFFFFFFFFFFFF
    return h


def laplacian_cdf():
    n = 2 * RMAX + 1
    pmf = np.exp(-np.abs(np.arange(n) - RMAX) / 6.0)
    total = 1 << 16
    f = np.maximum((pmf / pmf.sum() * (total - 1)).round().astype(np.int64), 1)
    f[f.argmax()] += (total - 1) - int(f.sum())
    cdf = [0]
    for v in f:
        cdf.append(cdf[-1] + int(v))
    cdf.append(total)
    return cdf


def make_clip():
    yy, xx = np.mgrid[0:H, 0:W]
    grad = ((xx * 80 // W) + (yy * 60 // H)).astype(np.int64)
    # two discs with integer position/velocity, reflecting off the walls
    p1, v1, r1, col1 = [28, 30], [6, 4], 16, [250, 205, 70]
    p2, v2, r2, col2 = [96, 80], [-5, 6], 10, [70, 215, 230]
    frames = []
    for _ in range(NF):
        img = np.empty((H, W, 3), np.int64)
        img[..., 0] = np.clip(35 + grad, 0, 255)
        img[..., 1] = np.clip(55 + grad // 2, 0, 255)
        img[..., 2] = np.clip(85 + grad // 3, 0, 255)
        for (p, r, col) in ((p1, r1, col1), (p2, r2, col2)):
            img[((xx - p[0]) ** 2 + (yy - p[1]) ** 2) <= r * r] = col
        frames.append(img.astype(np.int64))
        for (p, v, r) in ((p1, v1, r1), (p2, v2, r2)):
            for i in (0, 1):
                p[i] += v[i]
                if p[i] < r or p[i] >= (W if i == 0 else H) - r:
                    v[i] = -v[i]
                    p[i] += 2 * v[i]
    return frames


def mc_predict(ref, mvs):
    pred = np.empty_like(ref)
    nbx = (W + BLOCK - 1) // BLOCK
    for by in range(0, H, BLOCK):
        for bx in range(0, W, BLOCK):
            dy, dx = mvs[(by // BLOCK) * nbx + (bx // BLOCK)]
            ys = np.clip(np.arange(by, min(by + BLOCK, H)) + dy, 0, H - 1)
            xs = np.clip(np.arange(bx, min(bx + BLOCK, W)) + dx, 0, W - 1)
            pred[by:by + len(ys), bx:bx + len(xs)] = ref[np.ix_(ys, xs)]
    return pred


def search_mvs(cur, ref):
    mvs = []
    for by in range(0, H, BLOCK):
        for bx in range(0, W, BLOCK):
            cb = cur[by:by + BLOCK, bx:bx + BLOCK]
            best, bmv = None, (0, 0)
            for dy in range(-SEARCH, SEARCH + 1):
                for dx in range(-SEARCH, SEARCH + 1):
                    ys = np.clip(np.arange(by, by + cb.shape[0]) + dy, 0, H - 1)
                    xs = np.clip(np.arange(bx, bx + cb.shape[1]) + dx, 0, W - 1)
                    sad = int(np.abs(cb - ref[np.ix_(ys, xs)]).sum())
                    if best is None or sad < best:
                        best, bmv = sad, (dy, dx)
            mvs.append([int(bmv[0]), int(bmv[1])])
    return mvs


def main(outdir):
    os.makedirs(outdir, exist_ok=True)
    frames = make_clip()
    cdf, offset = laplacian_cdf(), -RMAX
    enc = RansEncoder()
    syms, mvs_all, recon, hashes = [], [], [], []
    for f in range(NF):
        if f == 0:
            pred, mvs = np.full((H, W, 3), 128, np.int64), []
        else:
            mvs = search_mvs(frames[f], recon[-1])
            pred = np.stack([mc_predict(recon[-1][..., c], mvs) for c in range(3)], -1)
        rq = np.round((frames[f] - pred) / Q).astype(np.int64).clip(-RMAX, RMAX)
        syms.extend(rq.reshape(-1).tolist())
        rec = np.clip(pred + rq * Q, 0, 255).astype(np.int64)
        recon.append(rec)
        mvs_all.append(mvs)
        hashes.append(format(fnv1a(np.ascontiguousarray(rec.astype(np.uint8)).tobytes()), '016x'))

    bits = enc.encode_with_indexes(syms, [0] * len(syms), [cdf], [len(cdf)], [offset])
    clip_hash = format(fnv1a(b''.join(bytes.fromhex(h) for h in hashes)), '016x')
    json.dump({'block': BLOCK, 'q': Q, 'rmax': RMAX, 'offset': offset, 'cdf': cdf,
               'n_frames': NF, 'h': H, 'w': W, 'mvs': mvs_all,
               'rans_b64': base64.b64encode(bytes(bits)).decode()},
              open(f'{outdir}/video_demo_bitstream.json', 'w'))
    json.dump({'n_frames': NF, 'h': H, 'w': W, 'frame_hashes': hashes, 'clip_hash': clip_hash},
              open(f'{outdir}/video_demo.json', 'w'))
    sz = os.path.getsize(f'{outdir}/video_demo_bitstream.json')
    print(f'demo clip: {NF}x {H}x{W}, {len(bits)} rANS bytes (bitstream {sz} B) -> clip_hash {clip_hash}')


if __name__ == '__main__':
    main(sys.argv[1])