#!/usr/bin/env python3
"""
Read `terraform output -json` from stdin, emit an Ansible hosts.yml to stdout.

Usage:
    terraform -chdir=terraform/environments/<env> output -json \\
      | python3 scripts/tf_to_inventory.py > inventories/<env>/hosts.yml

Expected Terraform output shape:
    {
      "vms": {
        "value": {
          "hostname": { "ip": "192.168.1.10", "group": "docker_hosts" }
        }
      }
    }

Valid groups: control, docker_hosts, proxmox_hosts, offsite_hosts
(control and offsite_hosts hold manually-provisioned hosts not in Terraform; they
are valid so their sections appear in the generated inventory — see ADR-009.)
"""

import json
import sys

VALID_GROUPS = {"control", "docker_hosts", "proxmox_hosts", "offsite_hosts"}


def main() -> None:
    try:
        data = json.load(sys.stdin)
    except json.JSONDecodeError as exc:
        print(f"error: could not parse Terraform output JSON: {exc}", file=sys.stderr)
        sys.exit(1)

    vms = data.get("vms", {}).get("value", {})
    if not vms:
        print("warning: no VMs in Terraform output — writing empty inventory", file=sys.stderr)

    groups: dict[str, dict[str, str]] = {}
    for hostname, info in vms.items():
        group = info.get("group", "")
        if group not in VALID_GROUPS:
            print(
                f"error: unknown group '{group}' for host '{hostname}' "
                f"(valid: {', '.join(sorted(VALID_GROUPS))})",
                file=sys.stderr,
            )
            sys.exit(1)
        groups.setdefault(group, {})[hostname] = info["ip"]

    lines = [
        "---",
        "# Generated by scripts/tf_to_inventory.py — do not edit manually.",
        "# Regenerate with: make tf-inventory TF_ENV=<env>",
        "# This OVERWRITES the file, including any manually-added control node (ubongo) —",
        "# re-add it afterwards (the one hand-edit exception; docs/runbooks/new-host.md Part E).",
        "",
        "all:",
        "  children:",
    ]

    for group in sorted(VALID_GROUPS):
        lines.append(f"    {group}:")
        hosts = groups.get(group, {})
        if hosts:
            lines.append("      hosts:")
            for hostname in sorted(hosts):
                lines.append(f"        {hostname}:")
                lines.append(f"          ansible_host: {hosts[hostname]}")
        else:
            lines.append("      hosts: {}")

    print("\n".join(lines))


if __name__ == "__main__":
    main()