const JSZM = require('./jszm-async')

const defer = () => {
    const deferred = {
        resolve: value => (deferred._resolved = value),
        reject: err => (deferred._rejected = err)
    }
    const promise = new Promise((resolve, reject) => {
        if (deferred.hasOwnProperty('_resolved')) return resolve(deferred._resolved)
        if (deferred.hasOwnProperty('_rejected')) return reject(deferred._rejected)
        deferred.resolve = resolve
        deferred.reject = reject
    })
    deferred.promise = promise
    return deferred
}

class VM {
    constructor(data, save) {
        this.zm = new JSZM(data)
        const vm = this
        let printBuffer = []
        const transcript = []
        this.inputBuffer = []
        this.outputBuffer = []
        this.saveData = save
        this.zm.save = function*(buf) {
            vm.saveData = buf
            return true
        }

        this.zm.restore = function*() {
            return vm.saveData
        }

        this.zm.highlight = function*(a) {
            //printBuffer.push(`[${a}]`)
        }

        this.zm.print = function*(text, scripting) {
            printBuffer.push(text)
            if (scripting) {
                transcript.push(text)
            }
        }

        const flush = () => {
            const output = printBuffer.join('')
            printBuffer = []
            if (this.outputBuffer.length) {
                const deferred = this.outputBuffer.shift()
                deferred.resolve(output)
            } else {
                this.initialOutput = output
            }
        }

        vm.reader = null
        this.zm.read = async function*(maxlen) {
            flush() // Should only read after done writing, so flush what it's written.
            if (vm.reader) throw new Error('Simultaneous reads')
            if (vm.inputBuffer.length) {
                const text = this.inputBuffer.shift()
                return text
            } else {
                const deferred = defer()
                vm.reader = deferred
                const text = await deferred.promise
                vm.reader = null
                return text
            }
        }
    }

    start() {
        if (this._started) throw new Error('Already started')
        const deferred = defer()
        this.outputBuffer.push(deferred)
        this.zm.run().next()
        return deferred.promise
    }

    play(text) {
        const deferred = defer()
        this.outputBuffer.push(deferred)
        if (this.reader) {
            this.reader.resolve(text)
        } else {
            this.inputBuffer.push(text)
        }
        return deferred.promise
    }

    save() {
        const ret = [Buffer.from(this.zm.serialize([], [])).toString('base64')]
        if (this.saveData) {
            ret.push(Buffer.from(this.saveData).toString('base64'))
        }
        return ret.join('.')
    }

    restore(save) {
        if (typeof save === 'string') {
            const datas = save.split('.')
            this.zm.deserialize(Buffer.from(datas[0], 'base64'))
            if (datas.length > 1) {
                this.saveData = Buffer.from(datas[1], 'base64')
            }
        }
    }
}

VM.play = async (data, save, input) => {
    const vm = new VM(data)
    const ret = {}
    ret.output = await vm.start()
    if (save) {
        vm.restore(save)
    }
    if (input) {
        ret.output = await vm.play(input)
    }    
    ret.save = vm.save()
    return ret
}

module.exports = VM