/**
 * Network Topology Map — pure logic helpers.
 *
 * No React, no DOM — fully unit-testable.
 * All data is derived from the existing Agent type; no backend changes needed.
 */

import type { Agent } from '../types';

// ── Subnet parsing ─────────────────────────────────────────────────────────

/**
 * Extract the /24 subnet string from an IPv4 address.
 * "192.168.1.42" → "192.168.1.0/24"
 * Returns "unknown" when the IP is missing or non-IPv4.
 */
export function parseSubnet(ip: string | undefined): string {
  if (!ip) return 'unknown';
  const parts = ip.split('.');
  if (parts.length !== 4 || parts.some((p) => isNaN(Number(p)))) return 'unknown';
  return `${parts[0]}.${parts[1]}.${parts[2]}.0/24`;
}

/** Human-friendly label: "192.168.1.x" */
export function subnetLabel(subnet: string): string {
  if (subnet === 'unknown') return 'Unknown';
  return subnet.replace('.0/24', '.x');
}

/** Group agents by their /24 subnet. */
export function groupBySubnet(agents: Agent[]): Map<string, Agent[]> {
  const map = new Map<string, Agent[]>();
  for (const a of agents) {
    const s = parseSubnet(a.ip);
    if (!map.has(s)) map.set(s, []);
    map.get(s)!.push(a);
  }
  return map;
}

// ── Layout ─────────────────────────────────────────────────────────────────

/** Stable hash from a string → 0..1 float. */
function stableHash(seed: string): number {
  let h = 2166136261 >>> 0;
  for (let i = 0; i < seed.length; i++) {
    h ^= seed.charCodeAt(i);
    h = Math.imul(h, 16777619) >>> 0;
  }
  return (h % 10000) / 10000;
}

/** Two independent stable floats for x/y from one seed. */
function stableXY(seed: string): { x: number; y: number } {
  return {
    x: stableHash(seed + ':x'),
    y: stableHash(seed + ':y'),
  };
}

export interface SubnetLayout {
  subnet: string;
  label: string;
  cx: number;   // center x, 0-100 viewBox
  cy: number;   // center y, 0-100 viewBox
  r: number;    // radius of the bubble ring
  color: string;
}

const SUBNET_PALETTE = [
  '#00e8f5', // cyan
  '#b24bf3', // violet
  '#39ff14', // neon green
  '#ff2da6', // magenta
  '#ffb020', // amber
  '#ff6b35', // orange
  '#3a86ff', // blue
  '#06d6a0', // teal
  '#ffd60a', // yellow
  '#f72585', // hot pink
];

export function subnetColor(index: number): string {
  return SUBNET_PALETTE[index % SUBNET_PALETTE.length];
}

/**
 * Place subnet bubbles in a circle around the center.
 * Single subnet gets center position.
 */
export function layoutSubnets(subnets: string[]): SubnetLayout[] {
  const total = subnets.length;
  const BASE_R = 18;
  const ORBIT_R = total === 1 ? 0 : 28;

  return subnets.map((subnet, i) => {
    const angle = total === 1 ? 0 : (i / total) * Math.PI * 2 - Math.PI / 2;
    const cx = 50 + Math.cos(angle) * ORBIT_R;
    const cy = 50 + Math.sin(angle) * ORBIT_R;
    return {
      subnet,
      label: subnetLabel(subnet),
      cx,
      cy,
      r: BASE_R,
      color: subnetColor(i),
    };
  });
}

export interface TopoNode {
  id: string;
  agentId: string;
  label: string;
  x: number;
  y: number;
  subnet: string;
  subnetColor: string;
  online: boolean;
  platform: string;
  ip: string;
  hashrate: number;
  latencyMs?: number;
  joinLane?: string;
  canSpread: boolean;
  capabilities: Agent['capabilities'];
}

/**
 * Compute pixel positions for all nodes.
 * Nodes within a subnet scatter around the subnet center.
 */
export function layoutNodes(
  agents: Agent[],
  subnetLayouts: SubnetLayout[],
): TopoNode[] {
  const subnetMap = new Map(subnetLayouts.map((s) => [s.subnet, s]));
  const subnetAgentCounts = new Map<string, number>();

  for (const a of agents) {
    const s = parseSubnet(a.ip);
    subnetAgentCounts.set(s, (subnetAgentCounts.get(s) ?? 0) + 1);
  }

  const subnetCounters = new Map<string, number>();

  return agents.map((agent): TopoNode => {
    const subnet = parseSubnet(agent.ip);
    const layout = subnetMap.get(subnet) ?? { cx: 50, cy: 50, r: 18, color: '#00e8f5', subnet, label: 'Unknown' };
    const total = subnetAgentCounts.get(subnet) ?? 1;
    const idx = subnetCounters.get(subnet) ?? 0;
    subnetCounters.set(subnet, idx + 1);

    // Stable jitter within the bubble radius
    const jitter = stableXY(`${subnet}:${agent.id}`);
    const angle = (idx / Math.max(total, 1)) * Math.PI * 2 + (jitter.x - 0.5) * 0.8;
    const dist = (total === 1 ? 0 : 4 + Math.sqrt(total) * 2.5) * (0.6 + jitter.y * 0.4);
    const maxDist = layout.r * 0.75;

    return {
      id: agent.id,
      agentId: agent.id,
      label: agent.name,
      x: layout.cx + Math.cos(angle) * Math.min(dist, maxDist),
      y: layout.cy + Math.sin(angle) * Math.min(dist, maxDist),
      subnet,
      subnetColor: layout.color,
      online: agent.status === 'online',
      platform: agent.platform ?? 'unknown',
      ip: agent.ip ?? '—',
      hashrate: agent.hashrate_15m ?? 0,
      latencyMs: agent.latency_ms,
      joinLane: agent.join_lane,
      canSpread: !!(agent.capabilities?.auto_spread),
      capabilities: agent.capabilities,
    };
  });
}

// ── Edge graph ──────────────────────────────────────────────────────────────

export type EdgeKind =
  | 'subnet'        // same /24 — implies reachability
  | 'spread'        // lateral spread candidate
  | 'smb'           // SMB admin$ path (Windows + port 445)
  | 'winrm'         // WinRM (Windows + 5985/5986)
  | 'ssh'           // SSH lateral (Linux/Darwin)
  | 'cross_subnet'; // different subnets, but both spread-capable

export interface TopoEdge {
  id: string;
  sourceId: string;
  targetId: string;
  kind: EdgeKind;
  /** Highlight when either endpoint is selected. */
  active: boolean;
}

/** Determine what spread lanes exist between two agents. */
export function spreadLanesBetween(a: Agent, b: Agent): EdgeKind[] {
  if (!a.capabilities?.auto_spread || !b.capabilities?.auto_spread) return [];
  const lanes: EdgeKind[] = ['spread'];

  const aWin = (a.platform ?? '').toLowerCase().includes('win');
  const bWin = (b.platform ?? '').toLowerCase().includes('win');
  const aLin = (a.platform ?? '').toLowerCase().includes('linux') || (a.platform ?? '').toLowerCase().includes('darwin');
  const bLin = (b.platform ?? '').toLowerCase().includes('linux') || (b.platform ?? '').toLowerCase().includes('darwin');

  if (aWin && bWin) { lanes.push('smb'); lanes.push('winrm'); }
  if ((aLin && bWin) || (aWin && bLin) || (aLin && bLin)) lanes.push('ssh');

  return lanes;
}

/**
 * Build all edges for the topology graph.
 *
 * Rules:
 *  - Same subnet + both online → `subnet` edge
 *  - Both have auto_spread + online → additional `spread` / protocol edges
 *  - Cross-subnet + both spread-capable → `cross_subnet`
 */
export function buildEdges(agents: Agent[], selectedIds: Set<string>): TopoEdge[] {
  const online = agents.filter((a) => a.status === 'online');
  const edges: TopoEdge[] = [];
  const seen = new Set<string>();

  for (let i = 0; i < online.length; i++) {
    for (let j = i + 1; j < online.length; j++) {
      const a = online[i];
      const b = online[j];
      const subA = parseSubnet(a.ip);
      const subB = parseSubnet(b.ip);
      const sameSubnet = subA === subB && subA !== 'unknown';
      const edgeKey = [a.id, b.id].sort().join('::');

      if (seen.has(edgeKey)) continue;
      seen.add(edgeKey);

      const active = selectedIds.has(a.id) || selectedIds.has(b.id);

      if (sameSubnet) {
        edges.push({ id: edgeKey + ':subnet', sourceId: a.id, targetId: b.id, kind: 'subnet', active });
      }

      // Spread lanes (may add on top of subnet edge)
      const lanes = spreadLanesBetween(a, b);
      for (const lane of lanes) {
        if (lane === 'spread' && sameSubnet) continue; // subnet edge covers it
        const spreadKey = edgeKey + ':' + lane;
        if (seen.has(spreadKey)) continue;
        seen.add(spreadKey);
        edges.push({
          id: spreadKey,
          sourceId: a.id,
          targetId: b.id,
          kind: sameSubnet ? lane : 'cross_subnet',
          active,
        });
      }
    }
  }

  return edges;
}

/**
 * Which agents can be reached laterally from a source agent?
 * Returns agent IDs with the best available lane.
 */
export function spreadCandidates(
  source: Agent,
  allAgents: Agent[],
): { agentId: string; lane: EdgeKind }[] {
  if (!source.capabilities?.auto_spread || source.status !== 'online') return [];
  const results: { agentId: string; lane: EdgeKind }[] = [];

  for (const target of allAgents) {
    if (target.id === source.id || target.status !== 'online') continue;
    const lanes = spreadLanesBetween(source, target);
    if (lanes.length === 0) continue;
    // Prefer most specific lane
    const preferred = lanes.find((l) => l !== 'spread') ?? lanes[0];
    results.push({ agentId: target.id, lane: preferred });
  }
  return results;
}