1 files changed, 86 insertions, 0 deletions
diff --git a/util/CommandLineInterfacer.js b/util/CommandLineInterfacer.js
new file mode 100644
index 0000000..3f9d208
--- /dev/null
+++ b/util/CommandLineInterfacer.js
@@ -0,0 +1,86 @@
+const EventEmitter = require('events')
+const waitForData = require('./waitForData')
+const ansi = require('./ansi')
+
+module.exports = class CommandLineInterfacer extends EventEmitter {
+  constructor(inStream = process.stdin, outStream = process.stdout) {
+    super()
+
+    this.inStream = inStream
+    this.outStream = outStream
+
+    inStream.on('data', buffer => {
+      this.emit('inputData', buffer)
+    })
+
+    inStream.setRawMode(true)
+  }
+
+  async getScreenSize() {
+    const waitUntil = cond => waitForData(this.inStream, cond)
+
+    // Get old cursor position..
+    this.outStream.write(ansi.requestCursorPosition())
+    const { options: oldCoords } = this.parseANSICommand(
+      await waitUntil(buf => ansi.isANSICommand(buf, 82))
+    )
+
+    // Move far to the bottom right of the screen, then get cursor position..
+    // (We could use moveCursor here, but the 0-index offset isn't really
+    // relevant.)
+    this.outStream.write(ansi.moveCursorRaw(9999, 9999))
+    this.outStream.write(ansi.requestCursorPosition())
+    const { options: sizeCoords } = this.parseANSICommand(
+      await waitUntil(buf => ansi.isANSICommand(buf, 82))
+    )
+
+    // Restore to old cursor position.. (Using moveCursorRaw is actaully
+    // necessary here, since we'll be passing the coordinates returned from
+    // another ANSI command.)
+    this.outStream.write(ansi.moveCursorRaw(oldCoords[0], oldCoords[1]))
+
+    // And return dimensions.
+    const [ sizeLine, sizeCol ] = sizeCoords
+    return {
+      lines: sizeLine, cols: sizeCol,
+      width: sizeCol, height: sizeLine
+    }
+  }
+
+  parseANSICommand(buffer) {
+    // Typically ANSI commands are written ESC[1;2;3;4C
+    // ..where ESC is the ANSI escape code, equal to hexadecimal 1B and
+    //   decimal 33
+    // ..where [ and ; are the literal strings "[" and ";"
+    // ..where 1, 2, 3, and 4 are decimal integer arguments written in ASCII
+    //   that may last more than one byte (e.g. "15")
+    // ..where C is some number representing the code of the command
+
+    if (buffer[0] !== 0x1b || buffer[1] !== 0x5b) {
+      throw new Error('Not an ANSI command')
+    }
+
+    const options = []
+    let curOption = ''
+    let commandCode = null
+    for (let val of buffer.slice(2)) {
+      if (48 <= val && val <= 57) { // 0124356789
+        curOption = curOption.concat(val - 48)
+      } else {
+        options.push(parseInt(curOption))
+        curOption = ''
+
+        if (val !== 59) { // ;
+          commandCode = val
+          break
+        }
+      }
+    }
+
+    return {code: commandCode, options: options}
+  }
+
+  write(data) {
+    this.outStream.write(data)
+  }
+}