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docs/zagros/withdraw/withdraw-coin.md

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+# Blockchain Withdraw: Coin
+###### Sprint: 7
+
+### Outcome:
+Users can do coin withdrawal from any wallet to favorite address
+
+#### File destination:
+- {$Dena_Path}/app/model/withdraw.rb
+- {$Dena_Path}/app/workers/amqp/withdraw_coin.rb
+
+### Implementation description:
+after withdraw was created by the user through the API,
+the hooked method will be called and send the hash message (withdraw data) to RabbitMq relevant queue.<br />
+the class is responsible to handle the hash message is: `WithdrawCoin`
+
+    1- finding the Withdraw by the id in the hash message if not, an error will be logged that not found a record in DB and exit
+    2- locking the Withdraw
+    3- check state of the Withdraw is processing, if not, an error will be logged and exit
+    4- check destination address was present, if not, an error will be logged, the Withdraw will be failed and exit
+    5- logging warning message that withdraw is ready for sending to blockchain
+    6- find an active hot wallet, if not, an error will be logged, the Withdraw will be skipped, and exit
+    7- check the balance of the active hot wallet, if not appropriate log error, skip the Withdraw and exit
+    8- create an object from WalletService by the active hot wallet
+    9- **WalletService** call `build_withdrawal!` for the withdraw and return transaction
+    10- the `txid` of the Withdraw being update by the Hash of the transaction
+    11- changing withdraw the state from `processing` to `confirming` with `dispatch` function
+    12- save the Withdraw in DB
+```mermaid
+graph TD
+    A[API] --> |post request| B[withdraw model]
+    B --> |hooked method| C(RabbitMq)
+    D(withdraw coin) --> |hash message in queue| C
+    D --> E((WalletService))
+
+```
+#### WalletService
+this class using as a middleman for connecting to every coin wallet.<br />
+In the time of creation object, the adapter (the hand of this class to talk the crypto coin wallet) receives its config.<br />
+The aim of WalletService class is to union and structurize all crypto coin wallets implemented in the Peatio.<br />
+
+##### build_withdrawal! function
+this method create transaction on blockchain by the help of adapter and specific its config
+
+```mermaid
+graph LR
+    A(Peatio) -->|Blockchain stuffs| B[BlockchainService using adapter]
+    
+    A --> |Wallet Deposit/Withdraw| C[WalletService using adapter]
+    B --> |Blockchain stuffs| D((Btc Blockchain))
+    B --> |Blockchain stuffs| E((Eth Blockchain))
+    B --> |Blockchain stuffs| F((...))
+    B --> A
+
+    C --> |Wallet Deposit/Withdraw| G((Btc Wallet))
+    C --> |Wallet Deposit/Withdraw| H((Eth Wallet))
+    C --> |Wallet Deposit/Withdraw| I((...))
+    C --> A
+```