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DIAGRAMS.md

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Note

Below sections assume you've gone through the abbreviations table and core components

Statuses

There are two types of streams: STREAMING, when debt is actively accruing, and PAUSED, when debt is not accruing:

Type Status Description
STREAMING STREAMING_SOLVENT Streaming stream when there is no uncovered debt.
STREAMING STREAMING_INSOLVENT Streaming stream when there is uncovered debt.
PAUSED PAUSED_SOLVENT Paused stream when there is no uncovered debt.
PAUSED PAUSED_INSOLVENT Paused stream when there is uncovered debt.
PAUSED VOIDED Paused stream that cannot be restarted. Sets uncovered debt to 0 for insolvent streams.

Statuses diagram

The transition between statuses is done by specific functions, which can be seen in the text on the edges or by the time.

stateDiagram-v2
    direction LR

    state Streaming {
        direction LR
        STREAMING_SOLVENT
        STREAMING_INSOLVENT --> STREAMING_SOLVENT : deposit
        STREAMING_SOLVENT --> STREAMING_INSOLVENT : time
    }

    state Paused {
        direction RL
        PAUSED_SOLVENT
        PAUSED_INSOLVENT --> PAUSED_SOLVENT : deposit
        PAUSED_INSOLVENT
    }

    Streaming --> Paused : pause
    Paused --> Streaming : restart
    Paused --> VOIDED : void
    Streaming --> VOIDED : void

    NULL --> Streaming : create (rps > 0)
    NULL --> Paused : create (rps = 0)

    NULL:::grey
    Paused:::lightYellow
    PAUSED_INSOLVENT:::intenseYellow
    PAUSED_SOLVENT:::intenseYellow
    Streaming:::lightGreen
    STREAMING_INSOLVENT:::intenseGreen
    STREAMING_SOLVENT:::intenseGreen
    VOIDED:::red

    classDef grey fill:#b0b0b0,stroke:#333,stroke-width:2px,color:#000,font-weight:bold;
    classDef intenseGreen fill:#32cd32,stroke:#333,stroke-width:2px,color:#000,font-weight:bold;
    classDef intenseYellow fill:#ffd700,color:#000,font-weight:bold;
    classDef lightGreen fill:#98FB98,color:#000,font-weight:bold;
    classDef lightYellow fill:#ffff99,color:#000,font-weight:bold;
    classDef red fill:#ff4e4e,stroke:#333,stroke-width:2px;
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Function calls

Notes:

  1. The arrows point to the status on which the function can be called.
  2. The "update" comments refer only to the stream internal state.
  3. st is always updated to block.timestamp.
  4. Red lines refers to the function that are doing an ERC-20 transfer
flowchart LR
    subgraph Statuses
        NULL((NULL)):::grey
        STR((STREAMING)):::green
        PSED((PAUSED)):::yellow
        VOID((VOIDED)):::red
    end

    subgraph Functions
        CR([CREATE])
        ADJRPS([ADJUST_RPS])
        DP([DEPOSIT])
        PS([PAUSE])
        RST([RESTART])
        VD([VOID])
        RFD([REFUND])
        WTD([WITHDRAW])
    end

    BOTH((  )):::black


    classDef black fill:#000000,stroke:#333,stroke-width:2px;
    classDef green fill:#32cd32,stroke:#333,stroke-width:2px;
    classDef grey fill:#b0b0b0,stroke:#333,stroke-width:2px;
    classDef yellow fill:#ffff99,stroke:#333,stroke-width:2px;
    classDef red fill:#ff4e4e,stroke:#333,stroke-width:2px;

    CR -- "update rps<br/>update st" --> NULL

    ADJRPS -- "update sd (+od)<br/>update rps<br/>update st" -->  STR

    DP -- "update bal (+)" --> BOTH

    RFD -- "update bal (-)" --> BOTH
    RFD -- "update bal (-)" --> VOID

    PS -- "update sd (+od)<br/>update rps (0)<br/>update st" --> STR

    BOTH --> STR & PSED

    RST -- "update rps<br/>update st" --> PSED

    VD -- "update sd (bal || +od)<br/>update rps (0)<br/>update st" --> BOTH

    WTD -- "update sd (-)<br/>update st<br/>update bal (-)" --> BOTH
    WTD -- "update sd (-)" --> VOID

    linkStyle 2,3,4,10,11 stroke:#ff0000,stroke-width:2px
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Internal State

The stream struct has more fields than the ones shown here, but these are the most relevant ones.

flowchart LR
    stream[(Stream Internal State)]:::green
    bal([Balance - bal]):::green
    rps([RatePerSecond - rps]):::green
    sd([SnapshotDebt - sd]):::green
    st([Snapshot Time - st]):::green

    stream --> bal
    stream --> rps
    stream --> sd
    stream --> st

    classDef green fill:#32cd32,stroke:#333,stroke-width:2px;
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ERC-20 Transfer Actions

flowchart LR
    erc_transfers[(ERC20 Transfer Actions)]:::red
    dep([Deposit - add]):::red
    ref([Refund - remove]):::red
    wtd([Withdraw - remove]):::red

    erc_transfers --> dep
    erc_transfers --> ref
    erc_transfers --> wtd

    classDef red fill:#ff4e4e,stroke:#333,stroke-width:2px;
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$~$

Amount Calculations

Ongoing Debt

flowchart TD
rca([Ongoing Debt - od]):::green1
di0{ }:::green0
di1{ }:::green0
res_00([0 ]):::green1
res_01([0 ]):::green1
res_rca(["rps * elt"]):::green1

rca --> di0
di0 -- "rps > 0" --> di1
di0 -- "rps == 0" --> res_00
di1 -- "now <= st" --> res_01
di1 -- "now > st" --> res_rca

classDef green0 fill:#98FB98,stroke:#333,stroke-width:2px;
classDef green1 fill:#32cd32,stroke:#333,stroke-width:2px;
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Uncovered Debt

Notes: A non-zero uncovered debt implies:

  1. bal < sd when the status is PAUSED
  2. bal < sd + od when the status is STREAMING
flowchart TD
    di0{ }:::red1
    sd([Uncovered Debt - ud]):::red0
    res_sd(["td - bal"]):::red1
    res_zero([0]):::red1

    sd --> di0
    di0 -- "bal < td" --> res_sd
    di0 -- "bal >= td" --> res_zero

    classDef red0 fill:#EA6B66,stroke:#333,stroke-width:2px;
    classDef red1 fill:#FFCCCC,stroke:#333,stroke-width:2px;
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Covered debt

flowchart TD
    di0{ }:::blue0
    di1{ }:::blue0
    di2{ }:::blue0
    cd([Covered Debt - cd]):::blue0
    res_0([0 ]):::blue1
    res_bal([bal]):::blue1
    res_sd([sd]):::blue1
    res_sum([td]):::blue1


    cd --> di0
    di0 -- "bal = 0" --> res_0
    di0 -- "bal > 0" --> di1
    di1 -- "ud > 0" --> res_bal
    di1 -- "ud = 0" --> di2
    di2 -- "paused" --> res_sd
    di2 -- "streaming" --> res_sum

    classDef blue0 fill:#DAE8FC,stroke:#333,stroke-width:2px;
    classDef blue1 fill:#1BA1E2,stroke:#333,stroke-width:2px;
    linkStyle 1,2,3,4,5,6 stroke:#1BA1E2,stroke-width:2px
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Refundable Amount

    flowchart TD
    ra([Refundable Amount - ra]):::orange0
    res_ra([bal - cd]):::orange1
    ra --> res_ra

    classDef orange0 fill:#FFA500,stroke:#333,stroke-width:2px;
    classDef orange1 fill:#FFCD28,stroke:#333,stroke-width:2px;
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