#!/usr/bin/env swift
// REPL for JavaScriptCore (for arrow keys, use rlwrap command)
import JavaScriptCore

guard let ctx = JSContext() else {exit(1)}
guard let syntaxError = ctx.globalObject?.forProperty("SyntaxError") else {exit(1)}
let ueEoS = "Unexpected end of script"

// override console.log()
guard let console = ctx.evaluateScript("console") else {exit(1)}
let log: @convention(block) (JSValue) -> Void = {arg in
    if arg.isUndefined {print()} else {print(arg)}
}
console.setValue(log, forProperty: "log")

var repl = (lines: "", prompt: "> ")
print(repl.prompt, terminator: "")
while let line = readLine(strippingNewline: false) {
    let code = repl.lines + line
    repl = (lines: "", prompt: "> ")
    let value = ctx.evaluateScript(code)
    if let exp = ctx.exception {
        ctx.exception = nil
        let se = exp.isObject && exp.forProperty("constructor").isEqual(to: syntaxError)
        if se && exp.forProperty("message").isEqual(to: ueEoS) {
            repl = (lines: code, prompt: "+ ")
        } else {
            print(exp)
        }
    } else if let val = value {
        print(val)
    }
    print(repl.prompt, terminator: "")
}
print()