Escrow Smart Contract (in Ink!)

Escrow is a financial arrangement where a neutral third party temporarily holds funds/assets while two parties complete a transaction. It ensures:

1. Security: Funds are protected until conditions are met.
2. Trust: Neither party can act unilaterally.
3. Automation: Rules are enforced programmatically (via smart contracts).

Key Features

Feature	Description
Mutual Approval	Both buyer and seller must approve to release funds.
Automatic Execution	Transfers funds instantly when both parties approve.
Cancellation	Allows refunds (when funded) if the transaction fails.
Transparency	All actions logged as on-chain events
Security Checks	Prevents invalid states.

Data Structure

Component	Type	Description
buyer	AccountId	Initiator/asset depositor
seller	AccountId	Recipient of assets
amount	Balance	Agreed transaction value
buyer_approved	bool	Buyer's confirmation flag
seller_approved	bool	Seller's confirmation flag
state	EscrowState	Current lifecycle stage (see state diagram)

Functions overview

initiate_escrow - Start Transaction

Key Points:

• Buyer initiates by specifying seller/amount
• Prevents self-dealing with buyer == seller check
• Auto-increments escrow IDs

deposit_assets - Fund Escrow

Key Points:

• Only buyer can deposit
• Exact amount required
• Must be in Created state

complete_escrow - Mutual Approval

Key Points:

• Buyer and seller must call separately
• Prevents duplicate approvals
• Funds transfer only after mutual consent

cancel_escrow - Abort Transaction

Key Points:

• Either party can cancel
• Refund only if funds were deposited
• Completed escrows cannot be canceled

States

stateDiagram-v2
    [*] --> Created
    Created --> Funded : deposit_assets()\n
    Created --> Canceled : cancel_escrow()\n
    
    Funded --> Completed : complete_escrow()\n
    Funded --> Canceled : cancel_escrow()\n
    
    Completed --> [*]
    Canceled --> [*]

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Sequence Diagram

sequenceDiagram
    participant B as Buyer
    participant C as Contract
    participant S as Seller

    B->>C: initiate_escrow(seller, amount)
    activate C
    C-->>B: escrow_id
    deactivate C
    Note right of C: State: Created

    B->>C: deposit_assets(escrow_id) + amount
    activate C
    C-->>B: Ok
    deactivate C
    Note right of C: State: Funded

    B->>C: complete_escrow(escrow_id)
    activate C
    C->>C: Mark buyer_approved = true
    C-->>B: Ok
    deactivate C

    S->>C: complete_escrow(escrow_id)
    activate C
    C->>C: Mark seller_approved = true
    alt Both approved?
        C->>S: Transfer funds
        Note right of C: State: Completed
    end
    C-->>S: Ok
    deactivate C

    alt Cancellation
        B->>C: cancel_escrow(escrow_id)
        activate C
        alt State == Funded
            C->>B: Refund
        end
        Note right of C: State: Canceled
        C-->>B: Ok
        deactivate C
    end

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