ts/node_readline.ts

   1 import * as path from "path";
   2 import * as ffi from "ffi";
   3 import * as fs from "fs";
   4
   5 // IMPORTANT: choose one
   6 const RL_LIB = "libreadline";  // NOTE: libreadline is GPL
   7 //var RL_LIB = "libedit";
   8
   9 const HISTORY_FILE = path.join(process.env.HOME, ".mal-history");
  10
  11 const rllib = ffi.Library(RL_LIB, {
  12     "readline": ["string", ["string"]],
  13     "add_history": ["int", ["string"]],
  14 });
  15
  16 let rlHistoryLoaded = false;
  17
  18 export function readline(prompt?: string): string | null {
  19     prompt = prompt || "user> ";
  20
  21     if (!rlHistoryLoaded) {
  22         rlHistoryLoaded = true;
  23         let lines: string[] = [];
  24         if (fs.existsSync(HISTORY_FILE)) {
  25             lines = fs.readFileSync(HISTORY_FILE).toString().split("\n");
  26         }
  27         // Max of 2000 lines
  28         lines = lines.slice(Math.max(lines.length - 2000, 0));
  29         for (let i = 0; i < lines.length; i++) {
  30             if (lines[i]) { rllib.add_history(lines[i]); }
  31         }
  32     }
  33
  34     const line = rllib.readline(prompt);
  35     if (line) {
  36         rllib.add_history(line);
  37         try {
  38             fs.appendFileSync(HISTORY_FILE, line + "\n");
  39         } catch (exc) {
  40             // ignored
  41         }
  42     }
  43
  44     return line;
  45 };