1 files changed, 139 insertions, 0 deletions
diff --git a/util/interfaces/TelnetInterface.js b/util/interfaces/TelnetInterface.js
new file mode 100644
index 0000000..8777680
--- /dev/null
+++ b/util/interfaces/TelnetInterface.js
@@ -0,0 +1,139 @@
+import EventEmitter from 'node:events'
+
+import * as ansi from '../ansi.js'
+import waitForData  from '../waitForData.js'
+
+export default class TelnetInterface extends EventEmitter {
+  constructor(socket) {
+    super()
+
+    this.socket = socket
+
+    socket.on('data', buffer => {
+      if (buffer[0] === 255) {
+        this.handleTelnetData(buffer)
+      } else {
+        this.emit('inputData', buffer)
+      }
+    })
+
+    this.initTelnetOptions()
+  }
+
+  initTelnetOptions() {
+    // Initializes various socket options, using telnet magic.
+
+    // Disables linemode.
+    this.socket.write(Buffer.from([
+      255, 253, 34,  // IAC DO LINEMODE
+      255, 250, 34, 1, 0, 255, 240,  // IAC SB LINEMODE MODE 0 IAC SE
+      255, 251, 1    // IAC WILL ECHO
+    ]))
+
+    // Will SGA. Helps with putty apparently.
+    this.socket.write(Buffer.from([
+      255, 251, 3  // IAC WILL SGA
+    ]))
+
+    this.socket.write(ansi.hideCursor())
+  }
+
+  cleanTelnetOptions() {
+    // Resets the telnet options and magic set in initTelnetOptions.
+
+    this.socket.write(ansi.resetAttributes())
+    this.socket.write(ansi.showCursor())
+  }
+
+  async getScreenSize() {
+    this.socket.write(Buffer.from([255, 253, 31])) // IAC DO NAWS
+
+    let didWillNAWS = false
+    let didSBNAWS = false
+    let sb
+
+    inputLoop: while (true) {
+      const data = await waitForData(this.socket)
+
+      for (const command of this.parseTelnetCommands(data)) {
+        // WILL NAWS
+        if (command[1] === 251 && command[2] === 31) {
+          didWillNAWS = true
+          continue
+        }
+
+        // SB NAWS
+        if (didWillNAWS && command[1] === 250 && command[2] === 31) {
+          didSBNAWS = true
+          sb = command.slice(3)
+          continue
+        }
+
+        // SE
+        if (didSBNAWS && command[1] === 240) { // SE
+          break inputLoop
+        }
+      }
+    }
+
+    return this.parseSBNAWS(sb)
+  }
+
+  parseTelnetCommands(buffer) {
+    if (buffer[0] === 255) {
+      // Telnet IAC (Is A Command) - ignore
+
+      // Split the data into multiple IAC commands if more than one IAC was
+      // sent.
+      const values = Array.from(buffer.values())
+      const commands = []
+      const curCmd = [255]
+      for (const value of values) {
+        if (value === 255) { // IAC
+          commands.push(Array.from(curCmd))
+          curCmd.splice(1, curCmd.length)
+          continue
+        }
+        curCmd.push(value)
+      }
+      commands.push(curCmd)
+
+      return commands
+    } else {
+      return []
+    }
+  }
+
+  write(data) {
+    this.socket.write(data)
+  }
+
+  handleTelnetData(buffer) {
+    let didSBNAWS = false
+    let sbNAWS
+
+    for (let command of this.parseTelnetCommands(buffer)) {
+      // SB NAWS
+      if (command[1] === 250 && command[2] === 31) {
+        didSBNAWS = true
+        sbNAWS = command.slice(3)
+        continue
+      }
+
+      // SE
+      if (didSBNAWS && command[1] === 240) { // SE
+        didSBNAWS = false
+        this.emit('screenSizeUpdated', this.parseSBNAWS(sbNAWS))
+        this.emit('resize', this.parseSBNAWS(sbNAWS))
+        continue
+      }
+    }
+  }
+
+  parseSBNAWS(sb) {
+    const cols = (sb[0] << 8) + sb[1]
+    const lines = (sb[2] << 8) + sb[3]
+
+    return { cols, lines, width: cols, height: lines }
+  }
+}