#!/usr/bin/env python3

import argparse
import json
from copy import deepcopy


def main():
    ap = argparse.ArgumentParser(description="Duplicate an instance N times to create multi-channel configs.")
    ap.add_argument("--in", dest="inp", required=True, help="Input config.json")
    ap.add_argument("--out", dest="out", required=True, help="Output config.json")
    ap.add_argument("--instance", required=True, help="Base instance name to duplicate")
    ap.add_argument("--count", type=int, required=True, help="Number of instances to generate")
    ap.add_argument("--name-prefix", default=None, help="New instance name prefix (default: base name)")
    ap.add_argument(
        "--url-pattern",
        default=None,
        help="Optional url pattern with {i} (0-based) and {n} (1-based), e.g. rtsp://ip/stream{n}",
    )
    args = ap.parse_args()

    with open(args.inp, "r", encoding="utf-8") as f:
        cfg = json.load(f)

    insts = cfg.get("instances")
    if not isinstance(insts, list):
        raise SystemExit("root.instances must be an array")

    base = None
    for it in insts:
        if isinstance(it, dict) and it.get("name") == args.instance:
            base = it
            break
    if base is None:
        raise SystemExit(f"instance not found: {args.instance}")

    prefix = args.name_prefix or args.instance
    out_insts = []
    for i in range(max(0, args.count)):
        one = deepcopy(base)
        one["name"] = f"{prefix}_{i+1:02d}"
        params = one.get("params")
        if not isinstance(params, dict):
            params = {}
            one["params"] = params
        if args.url_pattern is not None:
            params["url"] = args.url_pattern.format(i=i, n=i + 1)
        out_insts.append(one)

    cfg["instances"] = out_insts

    with open(args.out, "w", encoding="utf-8") as f:
        json.dump(cfg, f, ensure_ascii=False, indent=2)
        f.write("\n")


if __name__ == "__main__":
    main()