import {
  accountName,
  downloadStatusName,
  healthName,
  humanNow,
  humanRelative,
  kindName,
  subscriptionStatusName,
} from "../format.ts";
import type { EnvironmentFacts, PromptSection } from "../types.ts";

// 第 2 层:环境事实。会话开始时服务端从业务表读出的摘要,让模型知道"有什么"再去查"怎么样":
// 反例(docs/design/agent-report-sample-bad.md)里模型只看了站点列表,就汇报"系统里没有下载器"。
// 只写名称、类型、状态和计数,不写地址、ID 与凭证;数字以会话开始时为准,细节仍以工具结果为准。

const MAX_NAMED = 6;

function names<T>(items: readonly T[], render: (x: T) => string): string {
  const shown = items.slice(0, MAX_NAMED).map(render);
  const more = items.length - shown.length;
  return more > 0 ? `${shown.join("；")}；另有 ${more} 个` : shown.join("；");
}

/** 计数表 → "追更中 3、已取消 2";全 0 返回空串 */
function counts(m: Record<string, number>, label: (k: string) => string): string {
  return Object.entries(m)
    .filter(([, n]) => n > 0)
    .sort((a, b) => b[1] - a[1])
    .map(([k, n]) => `${label(k)} ${n}`)
    .join("、");
}

const total = (m: Record<string, number>) => Object.values(m).reduce((a, b) => a + b, 0);

export function renderEnvironment(f: EnvironmentFacts): string[] {
  const now = new Date(f.now);
  const tz = f.timeZone;
  const rel = (iso: string | null) => humanRelative(iso, now, tz);
  const lines: string[] = [`现在：${humanNow(now, tz)}。`];

  const dl = f.downloaders.filter((d) => d.enabled);
  if (dl.length === 0)
    lines.push(
      f.downloaders.length > 0
        ? `下载器：${f.downloaders.length} 个都已停用。`
        : "下载器：还没有接入（设置 → 下载器）。",
    );
  else
    lines.push(
      `下载器 ${dl.length} 个：${names(dl, (d) => {
        const seen = rel(d.lastSeenAt);
        const t = d.tasks;
        const tasks =
          t.total > 0
            ? `，本工具管理 ${t.total} 个任务（进行中 ${t.active}、失败 ${t.failed}）`
            : "，没有本工具管理的任务";
        return `「${d.name}」${kindName(d.kind)}，${healthName(d.health)}${seen ? `（${seen}）` : ""}${tasks}`;
      })}。`,
    );

  const ms = f.mediaServers.filter((m) => m.enabled);
  lines.push(
    ms.length === 0
      ? "媒体服务器：还没有接入。"
      : `媒体服务器 ${ms.length} 个：${names(ms, (m) => {
          const seen = rel(m.lastSeenAt);
          return `「${m.name}」${kindName(m.kind)}，${healthName(m.health)}${seen ? `（${seen}）` : ""}`;
        })}。`,
  );

  const sites = f.sites.filter((s) => s.enabled);
  lines.push(
    sites.length === 0
      ? "站点：还没有启用的站点。"
      : `站点 ${sites.length} 个：${names(sites, (s) => {
          const at = rel(s.lastHealthAt);
          const health =
            s.health === "unknown" ? "还没检查过" : `上次检查${healthName(s.health)}${at ? `（${at}）` : ""}`;
          return `「${s.name}」${kindName(s.kind)}，${health}${s.account ? `，${accountName(s.account)}` : ""}`;
        })}。`,
  );

  const roots = f.libraryRoots.filter((r) => r.enabled);
  lines.push(
    roots.length === 0
      ? "媒体库目录：还没有登记。"
      : `媒体库目录 ${roots.length} 个：${names(roots, (r) => `「${r.name}」${healthName(r.health)}`)}。`,
  );

  const subs = total(f.subscriptions);
  lines.push(subs === 0 ? "订阅：没有。" : `订阅 ${subs} 个：${counts(f.subscriptions, subscriptionStatusName)}。`);
  const dls = total(f.downloads);
  lines.push(
    dls === 0
      ? "下载任务（本工具管理）：没有。"
      : `下载任务（本工具管理）${dls} 个：${counts(f.downloads, downloadStatusName)}。`,
  );
  lines.push(f.openDecisions === 0 ? "待处理事项：没有。" : `待处理事项：${f.openDecisions} 条未关闭。`);
  if (f.webSearch !== undefined) lines.push(f.webSearch ? "网页搜索：已开启。" : "网页搜索：未开启。");
  return lines;
}

export function environmentLayer(f: EnvironmentFacts | null | undefined): PromptSection {
  if (!f) return { layer: "environment", title: "当前环境", lines: [] };
  return {
    layer: "environment",
    title: "当前环境",
    lines: [
      "会话开始时的快照，只有名称、状态和计数；要细节或最新状态用下面的能力查。这里写了「还没有接入」的就是真的没有，不用再向用户确认。",
      ...renderEnvironment(f).map((l) => `- ${l}`),
    ],
  };
}