import { listTasks } from './taskService.js';
import { listMessages } from './messageService.js';
import { getRoster } from './rosterService.js';
import { VERSION } from '../../version.js';

/**
 * Per-agent presence (lastSeen) + the /health report (TSK-0226).
 *
 * lastSeen is stamped by the server routes on every announce / claim / review /
 * log / message action. It is deliberately IN-MEMORY: presence is a live-view
 * concern of the running hub process, not project data — a restarted hub simply
 * re-learns presence from the agents' next actions.
 *
 * Traffic light per agent:
 *   active  (green) — acted within ACTIVE_WINDOW_MS (2 min)
 *   busy    (blue)  — has an in_progress task (shown as "busy-on-TSK-X")
 *   idle    (gray)  — seen within STALE_WINDOW_MS (10 min), nothing in flight
 *   stale   (red)   — not seen for > STALE_WINDOW_MS with an open assignment
 */

/** An agent that acted less than this long ago counts as active. */
export const ACTIVE_WINDOW_MS = 2 * 60_000;
/** Longer than this without any action ⇒ the agent is stale/offline. */
export const STALE_WINDOW_MS = 10 * 60_000;

export type AgentLight = 'active' | 'busy' | 'idle' | 'stale';

export interface AgentHealth {
  name: string;
  role: string;
  dispatch: 'loop' | 'architect';
  state: AgentLight;
  /** Busy-on task (in_progress) or — for stale agents — the waiting open task. */
  taskId?: string;
  waitingTaskId?: string;
  lastSeen?: string;
  lastSeenAgoSec?: number;
  inLoop: boolean;
  loopSince?: string;
  loopSinceAgoSec?: number;
  loopExitAt?: string;
  loopExitAgoSec?: number;
  loopExitReason?: string;
}

export interface HealthReport {
  status: 'ok';
  version: string;
  startedAt: string;
  uptimeSec: number;
  counts: { tasks: number; open: number; inProgress: number; review: number; unreadMessages: number };
  agents: AgentHealth[];
  indexErrors?: Array<{ filePath: string; error: string; at: string }>;
}

const lastSeen = new Map<string, number>();
const loops = new Map<string, { since?: number; exitAt?: number; exitReason?: string }>();

/** Stamp an agent's lastSeen (called by the routes on agent actions). */
export function stampSeen(agent: string, at: number = Date.now()): void {
  const name = agent?.trim();
  if (!name) return;
  lastSeen.set(name, at);
}

export function enterLoop(agent: string, at: number = Date.now()): void {
  const name = agent?.trim();
  if (!name) return;
  lastSeen.set(name, at);
  loops.set(name, { since: at });
}

export function leaveLoop(agent: string, reason: string, at: number = Date.now()): void {
  const name = agent?.trim();
  if (!name) return;
  lastSeen.set(name, at);
  loops.set(name, { exitAt: at, exitReason: reason || 'ended' });
}

export function isAgentInLoop(agent: string): boolean {
  return loops.get(agent)?.since !== undefined;
}

export function agentLoopStatus(agent: string): 'active' | 'inactive' | 'unknown' {
  const loop = loops.get(agent);
  if (!loop) return 'unknown';
  return loop.since !== undefined ? 'active' : 'inactive';
}

/** Test hook: drop all presence state. */
export function resetPresence(): void {
  lastSeen.clear();
  loops.clear();
}

/** One agent's traffic light, derived from presence + its task load. */
export function agentLight(
  name: string,
  tasks: Array<{ id: string; status?: string; assignedTo?: string; claimedBy?: string }>,
  now: number = Date.now(),
): Omit<AgentHealth, 'name' | 'role' | 'dispatch'> {
  const seen = lastSeen.get(name);
  const busy = tasks.find((t) => t.status === 'in_progress' && (t.assignedTo === name || t.claimedBy === name));
  const waiting = tasks.find((t) => t.status === 'open' && t.assignedTo === name);
  const seenAgo = seen === undefined ? undefined : now - seen;
  const loop = loops.get(name);

  let state: AgentLight;
  if (seenAgo !== undefined && seenAgo < ACTIVE_WINDOW_MS) {
    state = busy ? 'busy' : 'active';
  } else if (busy) {
    state = 'busy';
  } else if (seenAgo !== undefined && seenAgo < STALE_WINDOW_MS) {
    state = 'idle';
  } else if (waiting) {
    state = 'stale';
  } else {
    state = 'idle';
  }

  return {
    state,
    taskId: busy?.id ?? (state === 'stale' ? waiting?.id : undefined),
    waitingTaskId: waiting?.id,
    lastSeen: seen === undefined ? undefined : new Date(seen).toISOString(),
    lastSeenAgoSec: seenAgo === undefined ? undefined : Math.max(0, Math.round(seenAgo / 1000)),
    inLoop: loop?.since !== undefined,
    loopSince: loop?.since === undefined ? undefined : new Date(loop.since).toISOString(),
    loopSinceAgoSec: loop?.since === undefined ? undefined : Math.max(0, Math.round((now - loop.since) / 1000)),
    loopExitAt: loop?.exitAt === undefined ? undefined : new Date(loop.exitAt).toISOString(),
    loopExitAgoSec: loop?.exitAt === undefined ? undefined : Math.max(0, Math.round((now - loop.exitAt) / 1000)),
    loopExitReason: loop?.exitReason,
  };
}

/** Compact hub health: status + version + uptime + counts + per-agent lights. */
export function computeHealth(cwd: string, startedAtMs: number, now: number = Date.now()): HealthReport {
  const tasks = listTasks(cwd);
  const roster = getRoster(cwd);
  const roleByName = new Map(roster.map((r) => [r.name, r.role]));
  const dispatchByName = new Map(roster.map((r) => [r.name, r.dispatch]));
  // Roster agents PLUS anyone who only ever announced themselves (presence-only).
  const names = new Set<string>([...roster.map((r) => r.name), ...lastSeen.keys()]);

  const agents: AgentHealth[] = Array.from(names)
    .sort((a, b) => a.localeCompare(b))
    .map((name) => ({
      name,
      role: roleByName.get(name) ?? 'implementer',
      dispatch: dispatchByName.get(name) ?? 'loop',
      ...agentLight(name, tasks, now),
    }));

  return {
    status: 'ok',
    version: VERSION,
    startedAt: new Date(startedAtMs).toISOString(),
    uptimeSec: Math.max(0, Math.round((now - startedAtMs) / 1000)),
    counts: {
      tasks: tasks.length,
      open: tasks.filter((t) => t.status === 'open').length,
      inProgress: tasks.filter((t) => t.status === 'in_progress').length,
      review: tasks.filter((t) => t.status === 'review').length,
      unreadMessages: listMessages(cwd).filter((m) => m.status === 'unread').length,
    },
    agents,
  };
}