import type { Topic } from "./paths.ts";

function summaryOf(topic: Topic): string {
  const s = (topic.summary ?? "").trim();
  return s.length > 0 ? s : "(no summary)";
}

function titleOf(topic: Topic): string {
  const t = (topic.title ?? "").trim();
  return t.length > 0 ? t : topic.filename;
}

/** The on-disk INDEX.md content. Orchestrator-owned; the consolidator never writes it. */
export function renderIndexFile(topics: Topic[]): string {
  const parts: string[] = ["# Memory index", ""];
  if (topics.length === 0) {
    parts.push("_No topics yet._");
    return `${parts.join("\n")}\n`;
  }
  parts.push("Durable memory topics for this project. Read a file for its full current state.", "");
  for (const topic of topics) {
    const updated = topic.updated ? ` · updated ${topic.updated}` : "";
    parts.push(`## ${titleOf(topic)}`);
    parts.push(`- \`${topic.path}\`${updated}`);
    parts.push(`- ${summaryOf(topic)}`);
    parts.push("");
  }
  return `${parts.join("\n").trimEnd()}\n`;
}

/**
 * The compaction injection block's memory-map section. Returns undefined when there are no topics.
 */
export function renderMemoryMap(topics: Topic[]): string | undefined {
  if (topics.length === 0) return undefined;
  const lines: string[] = [
    "## Memory map",
    "Durable long-term notes live in `.memory/`. Read a file when a topic below looks relevant; these summaries are intentionally terse.",
  ];
  for (const topic of topics) {
    const updated = topic.updated ? ` (updated ${topic.updated})` : "";
    lines.push(`- \`${topic.path}\` — ${summaryOf(topic)}${updated}`);
  }
  return lines.join("\n");
}