const { performance } = require('perf_hooks')

var init

module.exports = blockgenerator

function blockgenerator ({ blockinterval = 6000, intrinsics }, log, emit) {

if (init) throw Error('block generator already initialized')

var currentBlock = 0

var scheduled = []

var total = 0 // TODO: make this BigInt

init = setInterval(async () => {

// if (currentBlock === 0) {

// for (var i = 0; i < scheduled.length; i++) {

// const action = scheduled[i]

// action.executeBlock += currentBlock

// }

// }

const startTime = performance.now()

currentBlock++

const temp = [...scheduled]

scheduled = []

while (temp.length) {

if ((performance.now() - startTime) > (blockinterval - 200)) {

scheduled = [...temp, ...scheduled]

log({ type: 'Error', data: 'not able to check or execute the remaining ${temp.length} intrinsics in scheduler during blockinterval' })

emit({ from: 'blockgenerator', type: 'block', data: { number: currentBlock, startTime } })

// TODO: maybe allow listeners to `emit` (= '*') events?

return

}

const { id, from, type, data, executeBlock } = temp.shift()

if (!id) continue // old item - id removed by `cancelAction(id)`

else if (executeBlock <= currentBlock) {

log({ type: 'scheduler', data: `Executing: ${type}` })

const intrinsic = intrinsics[type]

await intrinsic(from, data)

}

else scheduled.push({ id, from, type, data, executeBlock })

}

emit({ type: 'block', data: { number: currentBlock, startTime } })

}, blockinterval)

function scheduleAction ({ from, data, delay, type }) {

if (delay <= 0) return void setTimeout(() => {

const intrinsic = intrinsics[type]

intrinsic(from, data)

}, 0)

const item = { from, type, data, executeBlock: currentBlock + delay/*currentBlock? currentBlock + delay : delay*/ }

const id = item.id = total = total + 1

scheduled.push(item)

log({ type: 'scheduler', data: { from: from.path, type, data, id, executeBlock: item.executeBlock } })

return id

}

function cancelAction (id) {

log({ type: 'scheduler', data: { text: `Cancel: ${id}`, scheduled: scheduled.filter(entry => entry.id) } })

// log({ type: 'scheduler', data: { text: `Cancel: ${id}` } })

for (var i = 0, len = scheduled.length; i < len; i++) {

if (scheduled[i].id === id) scheduled[i].id = undefined

}

}

return { scheduleAction, cancelAction }

}