/**
 * Suggested prompt producer for the Home feed.
 *
 * Returns an array of `SuggestedPrompt` items shown at the top of the
 * Home page as conversation starters. All prompts are generated by the
 * assistant based on the user's connected services and context — read
 * from a checkpoint-backed cache in the GET path. Generation runs on
 * demand via `refreshAssistantSuggestedPrompts`, invoked fire-and-forget
 * by the home-content revalidation coordinator when a client fetches the
 * home feed and the cache is stale (see `home-content-refresh.ts`).
 * Nothing generates at daemon startup or on a timer.
 *
 * The cache persists in the `memory_checkpoints` table so a daemon
 * restart does not force a regeneration. OAuth connect/disconnect paths
 * invalidate it explicitly so suggestions track integration state.
 */

import { resolveCallSiteConfig } from "../config/llm-resolver.js";
import { getConfig } from "../config/loader.js";
import { buildSystemPrompt } from "../prompts/system-prompt.js";
import { getConfiguredProvider } from "../providers/provider-send-message.js";
import { runBtwSidechain } from "../runtime/btw-sidechain.js";
import { formatIntegrationSummary } from "../schedule/integration-status.js";
import { getLogger } from "../util/logger.js";
import type { SuggestedPrompt } from "./feed-types.js";
import {
  readCachedPrompts,
  writeCachedPrompts,
} from "./suggested-prompts-cache.js";

const log = getLogger("suggested-prompts");

const LLM_SUGGESTIONS_TIMEOUT_MS = 5_000;

/**
 * Return cached assistant-generated prompts. No LLM calls happen in
 * this path — safe for GET. Returns an empty array until the first
 * background refresh populates the cache.
 */
export async function getSuggestedPrompts(): Promise<SuggestedPrompt[]> {
  return readCachedPrompts() ?? [];
}

/**
 * Generate LLM-based suggestion prompts and write them to the cache.
 * No-ops when the cache is still fresh. Intended for fire-and-forget
 * background invocation, not the GET path. Returns `true` when a new
 * batch was generated and cached.
 */
export async function refreshAssistantSuggestedPrompts(): Promise<boolean> {
  if (readCachedPrompts() !== null) {
    return false;
  }

  try {
    const llmPrompts = await generateAssistantPrompts();
    // Cache empty results too — an empty or unparseable LLM response
    // would otherwise leave the cache unpopulated and every Home feed
    // GET would re-trigger generation until the TTL window closed.
    // Only report success when the cache write landed AND there is new
    // content — otherwise the coordinator would publish
    // home_feed_updated for content the next GET cannot serve.
    const wrote = writeCachedPrompts(llmPrompts);
    return wrote && llmPrompts.length > 0;
  } catch (err) {
    log.warn({ err }, "Failed to refresh assistant suggested prompts");
    return false;
  }
}

// ---------------------------------------------------------------------------
// LLM-generated suggestions
// ---------------------------------------------------------------------------

interface LLMSuggestion {
  label: string;
  prompt: string;
}

/**
 * Ask the LLM to generate contextual conversation-starter suggestions
 * based on the assistant's persona and the user's connected services.
 * Returns an empty array on failure.
 */
async function generateAssistantPrompts(): Promise<SuggestedPrompt[]> {
  const config = getConfig();
  const resolved = resolveCallSiteConfig("homeSuggestedPrompts", config.llm);

  const provider = await getConfiguredProvider("homeSuggestedPrompts");
  if (!provider) {
    return [];
  }

  const systemPrompt = buildSystemPrompt({
    excludeBootstrap: true,
    excludeCustomPrefix: true,
  });

  let integrationContext = "";
  try {
    integrationContext = `\nConnected integrations: ${await formatIntegrationSummary()}`;
  } catch {
    // Best-effort — continue without integration info
  }

  const result = await runBtwSidechain({
    content:
      "Suggest 2-3 short, actionable conversation starters for the home page. " +
      "Each should be something specific and helpful you can do for the user right now. " +
      "Focus on things the user's connected services enable — don't suggest connecting services they already have. " +
      "You may suggest connecting a service only if it's not yet connected and would be genuinely useful." +
      integrationContext +
      ' Return ONLY a JSON array of objects with "label" (max 5 words) and "prompt" (the full message to send). ' +
      "No markdown fences, no explanation.",
    provider,
    systemPrompt,
    messages: [],
    tools: [],
    callSite: "homeSuggestedPrompts",
    maxTokens: resolved.maxTokens,
    timeoutMs: LLM_SUGGESTIONS_TIMEOUT_MS,
  });

  const text = result.text.trim();
  if (!text) {
    return [];
  }

  const parsed = parseLLMSuggestions(text);
  return parsed.map((s, i) => ({
    id: `assistant-${i}-${s.label.toLowerCase().replace(/\s+/g, "-")}`,
    label: s.label,
    prompt: s.prompt,
    source: "assistant" as const,
  }));
}

function parseLLMSuggestions(text: string): LLMSuggestion[] {
  try {
    const cleaned = text
      .replace(/^```(?:json)?\n?/m, "")
      .replace(/\n?```$/m, "");
    const parsed = JSON.parse(cleaned);
    if (!Array.isArray(parsed)) {
      return [];
    }
    return parsed.filter(
      (item): item is LLMSuggestion =>
        typeof item === "object" &&
        item !== null &&
        typeof item.label === "string" &&
        typeof item.prompt === "string",
    );
  } catch {
    log.warn("Failed to parse LLM suggestions response");
    return [];
  }
}