sequenceDiagram
  participant AW as Alice's<br>web view
  participant AN as Alice's<br>app native
  participant AC as Alice's<br>chat core
  participant BC as Bob's<br>chat core
  participant BN as Bob's<br>app native
  participant BW as Bob's<br>web view

  note over AW, AC: Alice's app
  note over BC, BW: Bob's app

  note over AW, BW: 1. Establishing call

  note over AN: user: start call
  AN ->> AW: WCCapabilities
  AW ->> AN: WRCapabilities (e2e?)

  AN ->> AC: APISendCallInvitation
  AC -->> BC: XCallInv
  AC ->> AN: CRCmdOk

  BC ->> BN: CRCallInvitation
  note over BN: show: accept call?
  
  alt user accepted?
    BN ->> BC: no: APIRejectCall<br>(sender not notified)
    BC ->> BN: CRCmdOk
  else
    BN ->> BW: yes: WCStartCall
    BW ->> BN: WCallOffer
  end

  BN ->> BC: APISendCallOffer
  BC -->> AC: XCallOffer
  BC ->> BN: CRCmdOk
  AC ->> AN: CRCallOffer
  note over AN: show if no e2e: continue call?

  AN ->> AW: WCallOffer
  AW ->> AN: WCallAnswer
  AN ->> AC: APISendCallAnswer
  AC -->> BC: XCallAnswer
  AC ->> AN: CRCmdOk
  BC ->> BN: CRCallAnswer
  BN ->> BW: WCallAnswer

  note over AW, BW: call can be established at this point

  note over AW, BW: 2. Sending additional ice candidates<br>(optional, same for another side):

  BW ->> BN: WCallICE
  BN ->> BC: APISendCallExtraInfo
  BC -->> AC: XCallExtra
  BC ->> BN: CRCmdOk
  AC ->> AN: CRCallExtraInfo
  AN ->> AW: WCallICE

  note over AW, BW: 3. Call termination (same for another party):

  note over AN: user: end call
  AN ->> AW: WEndCall
  AN ->> AC: APIEndCall
  AC -->> BC: XCallEnd
  AC ->> AN: CRCmdOk
  BC ->> BN: CRCallEnded
  note over BN: show: call ended
  BN ->> BW: WEndCall