#!/usr/bin/env python
"""Compose truth | sim... side-by-side comparison video with labels.

Usage:
  python compose_video.py --world work/B_03/world \
      --sims work/B_03/out_p1 work/B_03/out_p2 \
      --labels "mu=0.5 e=0.05" "mu=0.02 e=0.9" \
      --out work/B_03/compare_B_03.mp4
"""
import argparse
import json
from pathlib import Path

import cv2
import numpy as np


def read_frames(path):
    cap = cv2.VideoCapture(str(path))
    frames = []
    while True:
        ok, f = cap.read()
        if not ok:
            break
        frames.append(f)
    cap.release()
    return frames


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--world", required=True)
    ap.add_argument("--sims", nargs="+", required=True)
    ap.add_argument("--labels", nargs="+", required=True)
    ap.add_argument("--truth-label", default="truth (reference)")
    ap.add_argument("--out", required=True)
    args = ap.parse_args()
    assert len(args.labels) == len(args.sims)

    spec = json.loads((Path(args.world) / "spec.json").read_text())
    W, H = spec["video"]["width"], spec["video"]["height"]
    fps = spec["video"]["fps"] or 24.0

    panels = [(args.truth_label, read_frames(Path(args.world) / "render.mp4"))]
    for sim, lab in zip(args.sims, args.labels):
        panels.append((lab, read_frames(Path(sim) / "sim.mp4")))

    n = min(len(f) for _, f in panels)
    canvas_w, canvas_h = W * len(panels), H
    writer = cv2.VideoWriter(str(args.out), cv2.VideoWriter_fourcc(*"mp4v"),
                             fps, (canvas_w, canvas_h))
    font = cv2.FONT_HERSHEY_SIMPLEX
    for i in range(n):
        row = []
        for k, (lab, frames) in enumerate(panels):
            f = frames[i]
            if f.shape[:2] != (H, W):
                f = cv2.resize(f, (W, H))
            tag = f"{lab}  [{i+1}/{n}]"
            cv2.rectangle(f, (0, 0), (W, 34), (0, 0, 0), -1)
            cv2.putText(f, tag, (10, 24), font, 0.62, (255, 255, 255), 2, cv2.LINE_AA)
            if k:
                cv2.line(f, (0, 0), (0, H), (255, 255, 255), 2)
            row.append(f)
        writer.write(np.hstack(row))
    writer.release()
    print(f"wrote {args.out} ({n} frames, {canvas_w}x{canvas_h})")


if __name__ == "__main__":
    main()