import { readFileSync, writeFileSync, existsSync, mkdirSync, readdirSync, statSync } from "node:fs";
import { join } from "node:path";
import { resolveWebChatDir } from "@/lib/workspace";

export type WebSessionMeta = {
  id: string;
  title: string;
  createdAt: number;
  updatedAt: number;
  messageCount: number;
  /** When set, this session is scoped to a specific workspace file. */
  filePath?: string;
};

export function ensureDir() {
  const dir = resolveWebChatDir();
  if (!existsSync(dir)) {
    mkdirSync(dir, { recursive: true });
  }
  return dir;
}

/**
 * Read the session index, auto-discovering any orphaned .jsonl files
 * that aren't in the index (e.g. from profile switches or missing index).
 */
export function readIndex(): WebSessionMeta[] {
  const dir = ensureDir();
  const indexFile = join(dir, "index.json");
  let index: WebSessionMeta[] = [];
  if (existsSync(indexFile)) {
    try {
      index = JSON.parse(readFileSync(indexFile, "utf-8"));
    } catch {
      index = [];
    }
  }

  // Scan for orphaned .jsonl files not in the index
  try {
    const indexed = new Set(index.map((s) => s.id));
    const files = readdirSync(dir).filter((f) => f.endsWith(".jsonl"));
    let dirty = false;
    for (const file of files) {
      const id = file.replace(/\.jsonl$/, "");
      if (indexed.has(id)) {continue;}

      const fp = join(dir, file);
      const stat = statSync(fp);
      let title = "New Chat";
      let messageCount = 0;
      try {
        const content = readFileSync(fp, "utf-8");
        const lines = content.split("\n").filter((l) => l.trim());
        messageCount = lines.length;
        for (const line of lines) {
          const parsed = JSON.parse(line);
          if (parsed.role === "user" && parsed.content) {
            const text = String(parsed.content);
            title = text.length > 60 ? text.slice(0, 60) + "..." : text;
            break;
          }
        }
      } catch { /* best-effort */ }

      index.push({
        id,
        title,
        createdAt: stat.birthtimeMs || stat.mtimeMs,
        updatedAt: stat.mtimeMs,
        messageCount,
      });
      dirty = true;
    }

    if (dirty) {
      index.sort((a, b) => b.updatedAt - a.updatedAt);
      writeFileSync(indexFile, JSON.stringify(index, null, 2));
    }
  } catch { /* best-effort */ }

  return index;
}

export function writeIndex(sessions: WebSessionMeta[]) {
  const dir = ensureDir();
  writeFileSync(join(dir, "index.json"), JSON.stringify(sessions, null, 2));
}