"""Sync discovered mDNS hosts into the system hosts file.

Writes a managed block so native tools (ping, curl, kubectl) resolve `.local`
names without the `resolve` wrapper. Only IPv4, only the managed block is
touched — the rest of the file is preserved.
"""
import os
from pathlib import Path

from . import browse as _browse
from ._pick import pick_best

MARK_BEGIN = "# >>> mdns-termux managed >>>"
MARK_END = "# <<< mdns-termux managed <<<"


def hosts_path() -> Path:
    prefix = os.environ.get("PREFIX", "")
    if prefix and "com.termux" in prefix:
        return Path(prefix) / "etc" / "hosts"
    return Path("/etc/hosts")


def collect(duration: float = 3.0) -> dict[str, str]:
    """Return {hostname.local: best_ipv4} from all advertised services."""
    out: dict[str, str] = {}
    for it in _browse.browse(None, duration):
        server = (it.get("server") or "").rstrip(".")
        v4 = [a for a in (it.get("addresses") or []) if ":" not in a]
        if not server or not v4:
            continue
        best = pick_best(v4, family="v4")
        if best and server not in out:
            out[server] = best
    return out


def _render_block(mapping: dict[str, str]) -> str:
    lines = [MARK_BEGIN]
    for host in sorted(mapping):
        short = host[:-6] if host.endswith(".local") else host
        lines.append(f"{mapping[host]}\t{host} {short}")
    lines.append(MARK_END)
    return "\n".join(lines)


def _strip_block(text: str) -> str:
    out, skip = [], False
    for line in text.splitlines():
        if line.strip() == MARK_BEGIN:
            skip = True
            continue
        if line.strip() == MARK_END:
            skip = False
            continue
        if not skip:
            out.append(line)
    return "\n".join(out).rstrip("\n")


def sync(duration: float = 3.0, dry_run: bool = False) -> int:
    mapping = collect(duration)
    if not mapping:
        print("no hosts discovered on the LAN")
        return 1
    block = _render_block(mapping)
    if dry_run:
        print(block)
        return 0
    path = hosts_path()
    original = path.read_text() if path.exists() else "127.0.0.1\tlocalhost\n"
    body = _strip_block(original)
    path.write_text(f"{body}\n{block}\n")
    print(f"wrote {len(mapping)} host(s) to {path}")
    for host, ip in sorted(mapping.items()):
        print(f"  {ip}\t{host}")
    return 0