import { END } from "@uncaged/nerve-core";
import type { Moderator, ThreadContext } from "@uncaged/nerve-core";

import type { AnswererMeta } from "./roles/answerer.js";
import type { ExplorerMeta } from "./roles/explorer.js";
import type { QuestionerMeta } from "./roles/questioner.js";

export type WorkflowMeta = {
  questioner: QuestionerMeta;
  answerer: AnswererMeta;
  explorer: ExplorerMeta;
};

type Steps = ThreadContext<WorkflowMeta>["steps"];

function lastQuestionerRemaining(steps: Steps): QuestionerMeta | undefined {
  for (let i = steps.length - 1; i >= 0; i--) {
    const s = steps[i];
    if (s.role === "questioner") return s.meta;
  }
  return undefined;
}

/** End when the last two explorer invocations both added no new cards (issue #266 stagnation rule). */
function lastTwoExplorerRunsBothEmpty(steps: Steps): boolean {
  const explorerSteps = steps.filter((s) => s.role === "explorer");
  if (explorerSteps.length < 2) return false;
  const e1 = explorerSteps[explorerSteps.length - 1].meta as ExplorerMeta;
  const e2 = explorerSteps[explorerSteps.length - 2].meta as ExplorerMeta;
  return e1.new_cards.length === 0 && e2.new_cards.length === 0;
}

function queueAfterSkippedExplorer(steps: Steps): string[] {
  const q = lastQuestionerRemaining(steps);
  return q?.remaining_queue ?? [];
}

function queueAfterExplorerStep(steps: Steps): string[] {
  const last = steps[steps.length - 1];
  if (!last || last.role !== "explorer") return [];
  const q = lastQuestionerRemaining(steps);
  if (!q) return [];
  const e = last.meta as ExplorerMeta;
  return [...q.remaining_queue, ...e.new_cards];
}

export const moderator: Moderator<WorkflowMeta> = (context) => {
  const { steps } = context;

  if (steps.length === 0) {
    return "questioner";
  }

  const last = steps[steps.length - 1];

  if (last.role === "questioner") {
    return "answerer";
  }

  if (last.role === "answerer") {
    const am = last.meta as AnswererMeta;
    if (am.has_unanswered) {
      return "explorer";
    }
    const q = queueAfterSkippedExplorer(steps);
    if (q.length === 0) {
      return END;
    }
    return "questioner";
  }

  if (last.role === "explorer") {
    if (lastTwoExplorerRunsBothEmpty(steps)) {
      return END;
    }
    const q = queueAfterExplorerStep(steps);
    if (q.length === 0) {
      return END;
    }
    return "questioner";
  }

  return END;
};