import { readFileSync } from "node:fs";
import { getRouters } from "./router-loader.js";
import { getRule } from "./rule-store.js";
import type { RouterContext } from "./router-loader.js";

export interface InjectionResult {
  appendSystemContext?: string;
}

export async function resolveInjection(
  ctx: RouterContext,
  log: { info(msg: string): void; warn(msg: string): void }
): Promise<InjectionResult> {
  const routers = getRouters();
  const segments: string[] = [];

  for (const router of routers) {
    try {
      const key = await router.module.resolve(ctx);
      if (!key) continue;

      const promptFile = getRule(router.name, key);
      if (!promptFile) continue;

      try {
        const content = readFileSync(promptFile, "utf8").trim();
        if (content) {
          segments.push(content);
          log.info(`[prism-facet] injecting ${router.name}:${key} → ${promptFile}`);
        }
      } catch (err) {
        log.warn(`[prism-facet] cannot read ${promptFile}: ${String(err)}`);
      }
    } catch (err) {
      log.warn(`[prism-facet] router ${router.name} failed: ${String(err)}`);
    }
  }

  if (segments.length === 0) return {};
  return { appendSystemContext: segments.join("\n\n---\n\n") };
}