Web-based NovaForth repl

vweb/src/app.js

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+import 'xterm/css/xterm.css'
+import './app.css'
+import { Terminal } from 'xterm'
+import { Readline } from 'xterm-readline'
+import init, { WasmCPU, NovaForth } from '../pkg/vweb.js'
+
+const term = new Terminal()
+const rl = new Readline()
+const TIB = 80000 // Just a convenient place to stick a terminal input buffer for the repl. Could be any otherwise-unused address.
+const OUT = 0x10000 // A place that NovaForth will use for its output buffer
+let syms
+
+term.loadAddon(rl)
+term.open(document.getElementsByClassName('terminal')[0])
+term.write('Loading...\r\n')
+
+const handleKey = ({key, domEvent: { key: mnemonic }}) => {
+    if (mnemonic === 'Enter') {
+        console.log(mnemonic)
+    } else {
+        term.write(key)
+    }
+}
+
+init().then(async () => {
+    const cpu = new WasmCPU()
+    syms = JSON.parse(NovaForth.symbols()) // Grab the symbol table for the ROM so we can poke things by name
+
+    NovaForth.rom().forEach((byte, idx) => {
+        cpu.poke(0x400 + idx, byte)
+    })
+
+    term.write(`Loaded ${NovaForth.rom().length} bytes\r\n`)
+    NovaForth.prelude().split(/\n/).forEach((line) => {
+        const result = eval4th(cpu, line) // If there's anything wrong with the prelude, say so
+        if (result !== '') {
+            console.log(`Error with "${line}": ${result}`)
+        }
+    })
+    term.write(`Loaded NovaForth Prelude\r\n`)
+    document.getElementsByClassName('prelude')[0].appendChild(document.createTextNode(NovaForth.prelude()))
+
+    term.focus()
+
+    while (true) {
+        const line = await rl.read('> ') // Read the line of input
+        const str = eval4th(cpu, line) // Run it on the CPU
+        rl.println(str) // Println the result
+    }
+})
+
+function eval4th(cpu, line) {
+    // Copy the line to TIB and null-terminate it
+    for (let i = 0; i < line.length; i++) {
+        cpu.poke(TIB + i, line.charCodeAt(i))
+    }
+    cpu.poke(TIB + line.length, 0)
+
+    cpu.push_call(syms.stop) // Tell the CPU to stop once we're done
+    cpu.push_data(TIB) // Push the TIB and call eval
+    cpu.set_pc(syms.eval)
+    cpu.run() // Run it!
+
+    const len = cpu.peek24(syms.emit_cursor) // Find the length of the output
+    let str = '' // Copy the output from the memory to a JS string
+    for (let i = OUT; i < OUT + len; i++) {
+        str = str + String.fromCharCode(cpu.peek(i))
+    }
+    cpu.poke24(syms.emit_cursor, 0) // Re-clear the output buffer
+
+    return str
+}