git ssb

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const Graph = require('ipld-graph-builder')
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const Kernel = require('./kernel.js')
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const crypto = require('./crypto')
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module.exports = class Hypervisor {
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  constructor (opts) {
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    this._opts = {
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      hypervisor: this,
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      VMs: {}
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    }
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    this.graph = new Graph(opts.dag)
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    this._vmInstances = new Map()
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    Object.assign(this._opts, opts)
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  }
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  async getInstance (port) {
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    const id = await this.generateID(port.id)
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    let kernel = this._vmInstances.get(id)
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    if (!kernel) {
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      // load the container from the state
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      await this.graph.tree(port, 2)
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      // create a new kernel instance
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      const opts = Object.assign({
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        state: port.vm,
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        id: port.id
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      }, this._opts)
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      kernel = new Kernel(opts)
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      await kernel.start()
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      kernel.on('idle', () => {
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        this._vmInstances.delete(id)
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      })
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      this._vmInstances.set(id, kernel)
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    }
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    return kernel
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  }
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  async send (port, message) {
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    const vm = await this.getInstance(port)
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    const id = await this.generateID(port.id)
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    message._fromPort = id
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    vm.queue(message)
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  }
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  // given a port, wait untill its source contract has reached the threshold
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  // tick count
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  async wait (port, ticks) {
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    let kernel = await this.getInstance(port)
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    await kernel.wait(ticks)
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    return kernel
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  }
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  async createStateRoot (port, ticks) {
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    const kernel = await this.wait(port, ticks)
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    return this.graph.flush(kernel.state)
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  }
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  async generateID (port) {
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    let id = Buffer.concat([port.nonce, port.parent])
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    id = await crypto.subtle.digest('SHA-256', id)
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    return new Buffer(id).toString('hex')
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  }
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  addVM (type, vm) {
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    this._opts.VMs[type] = vm
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  }
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}
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