/**
 * The picture of what is actually raised, read from the hypervisor's own metadata.
 *
 * Deliberately reads the same tags `destroy` uses rather than re-deriving anything from the
 * declaration: a diagram built from the declaration would draw what was asked for and call
 * it what exists, which is the whole failure this pairing is meant to expose. Everything
 * shown here was either recorded on the resource when it was raised, or is being reported
 * by the running machine now — nothing is inferred from a file on disk.
 */

import { incusOk, taggedNetworks } from "../incus/client.ts";
import { depthOf, type Diagram, type DiagramMachine, type DiagramSegment } from "./model.ts";

interface RawInstance {
  name?: string;
  type?: string;
  status?: string;
  config?: Record<string, string>;
  devices?: Record<string, Record<string, string>>;
  state?: {
    network?: Record<
      string,
      { hwaddr?: string; addresses?: { family?: string; address?: string; netmask?: string; scope?: string }[] }
    >;
  };
}

export async function diagramFromLive(instanceId: string): Promise<Diagram> {
  const networks = (await taggedNetworks()).filter((n) => n.instanceId === instanceId);

  const json = (await incusOk(["list", "--format", "json"], 30_000)) ?? "[]";
  const parsed = JSON.parse(json) as RawInstance[];
  const mine = parsed.filter((i) => i.config?.["user.mesh-lab.instance"] === instanceId);
  if (mine.length === 0 && networks.length === 0) throw new Error(`no scenario instance '${instanceId}'`);

  const segmentOfLink = new Map(networks.map((n) => [n.name, n.segment]));

  // A gateway records the segments behind it, so the tree is recoverable from the routers
  // alone. Without this every segment would draw at the same depth and a picture of a
  // layered scenario would look flat — which is exactly the property under test.
  const parent = new Map<string, string>();
  for (const item of mine) {
    const inside = item.config?.["user.mesh-lab.router"];
    const outside = item.config?.["user.mesh-lab.outside"];
    if (!inside || !outside) continue;
    for (const segment of inside.split(",").filter(Boolean)) parent.set(segment, outside);
  }
  const parentOf = (name: string) => parent.get(name);

  const segments: DiagramSegment[] = networks.map((n) => ({
    name: n.segment,
    // Untagged links come from an instance raised before segment shape was recorded. Drawn
    // as private rather than guessed at, and the missing tag is said out loud on the lane.
    kind: n.kind ?? "private",
    cidr: n.cidr,
    mtu: n.mtu,
    behind: parentOf(n.segment),
    depth: depthOf(n.segment, parentOf),
  }));

  const machines: DiagramMachine[] = mine.map((item) => {
    const config = item.config ?? {};
    const isTransit = config["user.mesh-lab.transit"] !== undefined;
    const isRouter = config["user.mesh-lab.router"] !== undefined;

    // Addresses are joined to devices by MAC, not by name. A container's interface is
    // called what the device is called; a virtual machine names its own — `enp5s0` for the
    // device configured as `eth0` — so matching on the name attached every address to a
    // container and none to a VM, which read as machines that had failed to come up.
    const heldByMac = new Map<string, string[]>();
    const heldByName = new Map<string, string[]>();
    for (const [name, iface] of Object.entries(item.state?.network ?? {})) {
      const held = (iface.addresses ?? [])
        .filter((a) => a.scope === "global" && a.address)
        .map((a) => (a.netmask ? `${a.address}/${a.netmask}` : (a.address as string)));
      if (held.length === 0) continue;
      heldByName.set(name, held);
      if (iface.hwaddr) heldByMac.set(iface.hwaddr.toLowerCase(), held);
    }

    const attachments: DiagramMachine["attachments"] = [];
    for (const [device, spec] of Object.entries(item.devices ?? {})) {
      if (spec["type"] !== "nic") continue;
      const segment = segmentOfLink.get(spec["parent"] ?? "");
      if (!segment) continue;
      const mac = spec["hwaddr"]?.toLowerCase();
      const addresses = (mac ? heldByMac.get(mac) : undefined) ?? heldByName.get(device) ?? [];
      attachments.push({ segment, addresses });
    }
    // Outside first, then the segments behind it — the same order the declared picture uses,
    // and what lets the layout place a gateway above the lanes it SERVES rather than below
    // the one it faces. Sorting alphabetically threw that away.
    const outside = config["user.mesh-lab.outside"];
    attachments.sort((a, b) =>
      a.segment === outside ? -1 : b.segment === outside ? 1 : a.segment.localeCompare(b.segment),
    );

    const notes: string[] = [];
    notes.push(item.type === "container" ? "container" : "virtual machine");
    if (config["user.mesh-lab.inbound"] === "deny") notes.push("refuses inbound");
    if (isRouter) {
      const nat = (config["user.mesh-lab.nat"] ?? "").split(",").filter(Boolean);
      notes.push(nat.length > 0 ? `NAT ${nat.join("+")}` : "routed, no NAT");
      if (config["user.mesh-lab.forwardable"] !== undefined) {
        notes.push(config["user.mesh-lab.forwardable"] === "true" ? "forwardable" : "NOT forwardable");
      }
      const ttl = config["user.mesh-lab.mapping-ttl"];
      if (ttl) notes.push(`mappings expire ${ttl}s`);
    }

    return {
      name: config["user.mesh-lab.machine"] ?? item.name ?? "?",
      kind: isTransit ? "transit" : isRouter ? "router" : "machine",
      notes,
      attachments,
      ...(item.status ? { status: item.status } : {}),
    };
  });

  return { title: instanceId, source: "live", segments, machines };
}