/*
 *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
 *  License: AGPLv3 s.t. "Commons Clause" – see LICENSE.md for details
 */

/*
Jupyter's blob store (based on sqlite), which hooks into the raw http server.
*/

import { BlobStoreInterface } from "@cocalc/frontend/jupyter/project-interface";
import * as fs from "fs";
import { readFile } from "./async-utils-node";
import Logger from "@cocalc/backend/logger";
import { months_ago, to_json } from "@cocalc/util/misc";
const misc_node = require("@cocalc/backend/misc_node");
import Database from "better-sqlite3";
import { Router } from "express";
const winston = Logger("jupyter-blobs-sqlite");
import { get_ProjectStatusServer } from "@cocalc/project/project-status/server";

const JUPYTER_BLOBS_DB_FILE: string =
  process.env.JUPYTER_BLOBS_DB_FILE ??
  `${process.env.SMC_LOCAL_HUB_HOME ?? process.env.HOME}/.jupyter-blobs-v0.db`;

// TODO: are these the only base64 encoded types that jupyter kernels return?
const BASE64_TYPES = ["image/png", "image/jpeg", "application/pdf", "base64"];

export class BlobStore implements BlobStoreInterface {
  private db: Database.Database;
  private stmt_insert;
  private stmt_update;
  private stmt_get;
  private stmt_data;
  private stmt_ipynb;
  private stmt_keys;

  constructor() {
    winston.debug("jupyter BlobStore: constructor");
    try {
      this.init();
      winston.debug(`jupyter BlobStore: ${JUPYTER_BLOBS_DB_FILE} opened fine`);
    } catch (err) {
      winston.debug(
        `jupyter BlobStore: ${JUPYTER_BLOBS_DB_FILE} open error - ${err}`
      );
      // File may be corrupt/broken/etc. -- in this case, remove and try again.
      // This database is only an image *cache*, so this is fine.
      // See https://github.com/sagemathinc/cocalc/issues/2766
      // Using sync is also fine, since this only happens once
      // during initialization.
      winston.debug("jupyter BlobStore: resetting database cache");
      try {
        fs.unlinkSync(JUPYTER_BLOBS_DB_FILE);
      } catch (error) {
        err = error;
        winston.debug(
          `Error trying to delete ${JUPYTER_BLOBS_DB_FILE}... ignoring: `,
          err
        );
      }
      this.init();
    }
  }

  init(): void {
    if (JUPYTER_BLOBS_DB_FILE == "memory") {
      // as any, because @types/better-sqlite3 is not yet updated to support this
      // doc about the constructor: https://wchargin.com/better-sqlite3/api.html#new-databasepath-options
      this.db = new Database(".db", { memory: true } as any);
    } else {
      this.db = new Database(JUPYTER_BLOBS_DB_FILE);
    }

    this.init_table();
    this.init_statements(); // table must exist!

    if (JUPYTER_BLOBS_DB_FILE !== "memory") {
      this.clean(); // do this once on start
      this.db.exec("VACUUM");
    }
  }

  private init_table() {
    this.db
      .prepare(
        "CREATE TABLE IF NOT EXISTS blobs (sha1 TEXT, data BLOB, type TEXT, ipynb TEXT, time INTEGER)"
      )
      .run();
  }

  private init_statements() {
    this.stmt_insert = this.db.prepare(
      "INSERT INTO blobs VALUES(?, ?, ?, ?, ?)"
    );
    this.stmt_update = this.db.prepare("UPDATE blobs SET time=? WHERE sha1=?");
    this.stmt_get = this.db.prepare("SELECT * FROM blobs WHERE sha1=?");
    this.stmt_data = this.db.prepare("SELECT data FROM blobs where sha1=?");
    this.stmt_keys = this.db.prepare("SELECT sha1 FROM blobs");
    this.stmt_ipynb = this.db.prepare(
      "SELECT ipynb, type, data FROM blobs where sha1=?"
    );
  }

  private clean(): void {
    this.clean_old();
    this.clean_filesize();
  }

  private clean_old() {
    // Delete anything old...
    // The main point of this blob store being in the db is to ensure that when the
    // project restarts, then user saves an ipynb,
    // that they do not loose any work.  So a few weeks should be way more than enough.
    // Note that TimeTravel may rely on these old blobs, so images in TimeTravel may
    // stop working after this long.  That's a tradeoff.
    this.db
      .prepare("DELETE FROM blobs WHERE time <= ?")
      .run(months_ago(1).getTime());
  }

  private clean_filesize() {
    // we also check for the actual filesize and in case, get rid of half of the old blobs
    try {
      const stats = fs.statSync(JUPYTER_BLOBS_DB_FILE);
      const size_mb = stats.size / (1024 * 1024);
      if (size_mb > 128) {
        const cnt = this.db.prepare("SELECT COUNT(*) as cnt FROM blobs").get();
        if (cnt?.cnt == null) return;
        const n = Math.floor(cnt.cnt / 2);
        winston.debug(
          `jupyter BlobStore: large file of ${size_mb}MiB detected – deleting ${n} old rows.`
        );
        if (n == 0) return;
        const when = this.db
          .prepare("SELECT time FROM blobs ORDER BY time ASC LIMIT 1 OFFSET ?")
          .get(n);
        if (when?.time == null) return;
        winston.debug(`jupyter BlobStore: delete starting from ${when.time}`);
        this.db.prepare("DELETE FROM blobs WHERE time <= ?").run(when.time);
      }
    } catch (err) {
      winston.debug(`jupyter BlobStore: clean_filesize error: ${err}`);
    }
  }

  // used in testing
  delete_all_blobs(): void {
    this.db.prepare("DELETE FROM blobs").run();
  }

  // data could, e.g., be a uuencoded image
  // We return the sha1 hash of it, and store it, along with a reference count.
  // ipynb = (optional) text that is also stored and will be
  //         returned when get_ipynb is called
  //         This is used for some iframe support code.
  save(data, type, ipynb?): string {
    if (BASE64_TYPES.includes(type)) {
      data = Buffer.from(data, "base64");
    } else {
      data = Buffer.from(data);
    }
    const sha1: string = misc_node.sha1(data);
    const row = this.stmt_get.get(sha1);
    if (row == null) {
      this.stmt_insert.run([sha1, data, type, ipynb, Date.now()]);
    } else {
      this.stmt_update.run([Date.now(), sha1]);
    }
    return sha1;
  }

  // Read a file from disk and save it in the database.
  // Returns the sha1 hash of the file.
  async readFile(path: string, type: string): Promise<string> {
    return await this.save(await readFile(path), type);
  }

  /*
  free(sha1: string): void {
    // instead, stuff gets freed 1 month after last save.
  }
  */

  // Return data with given sha1, or undefined if no such data.
  get(sha1: string): undefined | Buffer {
    const x = this.stmt_data.get(sha1);
    if (x != null) {
      return x.data;
    }
  }

  get_ipynb(sha1: string): any {
    const row = this.stmt_ipynb.get(sha1);
    if (row == null) {
      return;
    }
    if (row.ipynb != null) {
      return row.ipynb;
    }
    if (BASE64_TYPES.includes(row.type)) {
      return row.data.toString("base64");
    } else {
      return row.data.toString();
    }
  }

  keys(): string[] {
    return this.stmt_keys.all().map((x) => x.sha1);
  }

  express_router(base): Router {
    const router = Router();
    base += "blobs/";

    router.get(base, (_, res) => {
      res.send(to_json(this.keys()));
    });

    router.get(base + "*", (req, res) => {
      const filename: string = req.path.slice(base.length);
      const sha1: string = `${req.query.sha1}`;
      res.type(filename);
      res.send(this.get(sha1));
    });
    return router;
  }
}

let blob_store: BlobStore | undefined = undefined;

export function get_blob_store() {
  if (blob_store != null) return blob_store;
  try {
    blob_store = new BlobStore();
    get_ProjectStatusServer().clearComponentAlert("BlobStore");
    return blob_store;
  } catch (err) {
    get_ProjectStatusServer().setComponentAlert("BlobStore");
    winston.warn(`unable to instantiate BlobStore -- ${err}`);
  }
}