import fs from "node:fs";
import os from "node:os";
import path from "node:path";

import JSON5 from "json5";
import type { MsgContext } from "../auto-reply/templating.js";
import { CONFIG_DIR, normalizeE164 } from "../utils.js";

export type SessionScope = "per-sender" | "global";

export type SessionEntry = {
  sessionId: string;
  updatedAt: number;
  systemSent?: boolean;
};

export const SESSION_STORE_DEFAULT = path.join(CONFIG_DIR, "sessions.json");
export const DEFAULT_RESET_TRIGGER = "/new";
export const DEFAULT_IDLE_MINUTES = 60;

export function resolveStorePath(store?: string) {
  if (!store) return SESSION_STORE_DEFAULT;
  if (store.startsWith("~"))
    return path.resolve(store.replace("~", os.homedir()));
  return path.resolve(store);
}

export function loadSessionStore(
  storePath: string,
): Record<string, SessionEntry> {
  try {
    const raw = fs.readFileSync(storePath, "utf-8");
    const parsed = JSON5.parse(raw);
    if (parsed && typeof parsed === "object") {
      return parsed as Record<string, SessionEntry>;
    }
  } catch {
    // ignore missing/invalid store; we'll recreate it
  }
  return {};
}

export async function saveSessionStore(
  storePath: string,
  store: Record<string, SessionEntry>,
) {
  await fs.promises.mkdir(path.dirname(storePath), { recursive: true });
  await fs.promises.writeFile(
    storePath,
    JSON.stringify(store, null, 2),
    "utf-8",
  );
}

// Decide which session bucket to use (per-sender vs global).
export function deriveSessionKey(scope: SessionScope, ctx: MsgContext) {
  if (scope === "global") return "global";
  const from = ctx.From ? normalizeE164(ctx.From) : "";
  return from || "unknown";
}