/**
 * @file Session snapshots: `POST /api/snapshots` freezes a session — its row,
 * agents, events (oldest first), the SessionOverview stats and the token cost —
 * into one immutable `session_snapshots` row read back by an unguessable token
 * (`GET /api/snapshots/:token`). File paths can be redacted at capture, so
 * nothing redacted is ever stored. Writes are same-origin only.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const crypto = require("node:crypto");
const os = require("node:os");
const { Router } = require("express");
const { db, stmts } = require("../db");
const { sameOriginGuard } = require("../lib/same-origin");
const { calculateCost, attachAgentCosts } = require("./pricing");
const { sessionStats } = require("./sessions");
const { bySessionWhere } = require("../lib/scope");

const router = Router();

/** Keys whose string value is a path on this machine — replaced whole. */
const PATH_KEYS = new Set([
  "cwd",
  "transcript_path",
  "agent_transcript_path",
  "file_path",
  "filePath",
  "notebook_path",
  "path",
]);
const REDACTED = "[redacted]";
/** 24 random bytes, base64url. */
const TOKEN_RE = /^[A-Za-z0-9_-]{32}$/;

function escapeRe(s) {
  return s.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
}

/**
 * A redactor for one session: path-valued keys become `[redacted]`, and the
 * session's cwd / the home dir inside any other string (a Bash command, a
 * summary) become `<cwd>` / `~`.
 */
function pathRedactor(cwd) {
  const swaps = [
    [cwd, "<cwd>"],
    [os.homedir(), "~"],
  ]
    .filter(([p]) => typeof p === "string" && p.length > 1)
    .map(([p, to]) => [new RegExp(`${escapeRe(p)}(?![\\w.-])`, "g"), to]);
  const str = (s) => swaps.reduce((acc, [re, to]) => acc.replace(re, to), s);
  const walk = (v, key) => {
    if (typeof v === "string") return PATH_KEYS.has(key) ? REDACTED : str(v);
    if (Array.isArray(v)) return v.map((x) => walk(x));
    if (v && typeof v === "object") {
      const out = {};
      for (const [k, x] of Object.entries(v)) out[k] = walk(x, k);
      return out;
    }
    return v;
  };
  // A column holding JSON text (events.data, *.metadata) is redacted as JSON.
  const json = (text) => {
    if (typeof text !== "string") return text;
    try {
      return JSON.stringify(walk(JSON.parse(text)));
    } catch {
      return str(text);
    }
  };
  return { walk, json };
}

function capture(sessionId, redactPaths) {
  const session = stmts.getSession.get(sessionId);
  if (!session) return null;
  const agents = attachAgentCosts(stmts.listAgentsBySession.all(sessionId));
  const events = stmts.listEventsBySession.all(sessionId).reverse();
  const cost = calculateCost(
    stmts.getTokensBySession.all(sessionId),
    stmts.listPricing.all(),
    session.started_at ? String(session.started_at).slice(0, 10) : undefined
  );
  const payload = {
    version: 1,
    captured_at: new Date().toISOString(),
    redacted: { file_paths: redactPaths },
    session,
    agents,
    events,
    stats: sessionStats(sessionId),
    cost,
  };
  if (!redactPaths) return payload;
  const r = pathRedactor(session.cwd);
  const row = (x) => {
    const out = r.walk(x);
    if ("data" in x) out.data = r.json(x.data);
    if ("metadata" in x) out.metadata = r.json(x.metadata);
    return out;
  };
  return {
    ...payload,
    session: row(session),
    agents: agents.map(row),
    events: events.map(row),
  };
}

// GET /api/snapshots — every snapshot, newest first, without its payload; a
// server-mode member gets only the snapshots of their own sessions.
router.get("/", (req, res) => {
  const own = bySessionWhere(req);
  const snapshots = db
    .prepare(
      `SELECT id, token, session_id, created_at,
              json_extract(payload, '$.session.name') AS session_name,
              json_extract(payload, '$.redacted.file_paths') AS redacted,
              json_array_length(payload, '$.events') AS event_count,
              length(payload) AS bytes
         FROM session_snapshots WHERE ${own.where} ORDER BY id DESC`
    )
    .all(...own.params)
    .map((s) => ({ ...s, redacted: s.redacted === 1 }));
  res.json({ snapshots });
});

// POST /api/snapshots {session_id, redact?: {file_paths?: boolean}}
router.post("/", sameOriginGuard, (req, res) => {
  const sessionId = req.body?.session_id;
  if (typeof sessionId !== "string" || !sessionId) {
    return res
      .status(400)
      .json({ error: { code: "INVALID_INPUT", message: "session_id is required" } });
  }
  const payload = capture(sessionId, req.body?.redact?.file_paths === true);
  if (!payload) {
    return res.status(404).json({ error: { code: "NOT_FOUND", message: "Session not found" } });
  }
  const token = crypto.randomBytes(24).toString("base64url");
  const { lastInsertRowid } = db
    .prepare("INSERT INTO session_snapshots (token, session_id, payload) VALUES (?, ?, ?)")
    .run(token, sessionId, JSON.stringify(payload));
  const row = db
    .prepare("SELECT id, token, session_id, created_at FROM session_snapshots WHERE id = ?")
    .get(lastInsertRowid);
  res.status(201).json({ snapshot: row });
});

// GET /api/snapshots/:token — the frozen payload, sent as stored.
router.get("/:token", (req, res) => {
  const token = req.params.token;
  const row = TOKEN_RE.test(token)
    ? db
        .prepare(
          "SELECT id, token, session_id, created_at, payload FROM session_snapshots WHERE token = ?"
        )
        .get(token)
    : null;
  if (!row) {
    return res.status(404).json({ error: { code: "NOT_FOUND", message: "Snapshot not found" } });
  }
  const { payload, ...meta } = row;
  res.type("application/json").send(`{"snapshot":${JSON.stringify(meta)},"payload":${payload}}`);
});

// DELETE /api/snapshots/:id
router.delete("/:id", sameOriginGuard, (req, res) => {
  const id = Number(req.params.id);
  const { changes } = Number.isInteger(id)
    ? db.prepare("DELETE FROM session_snapshots WHERE id = ?").run(id)
    : { changes: 0 };
  if (!changes) {
    return res.status(404).json({ error: { code: "NOT_FOUND", message: "Snapshot not found" } });
  }
  res.json({ ok: true });
});

module.exports = router;
module.exports.pathRedactor = pathRedactor;