Add solution for Challenge 7 by onomica #1884
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,154 @@ | ||
| package challenge7 | ||
|
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| import ( | ||
| "fmt" | ||
| "sync" | ||
| ) | ||
|
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| type BankAccount struct { | ||
| ID string | ||
| Owner string | ||
| Balance float64 | ||
| MinBalance float64 | ||
| mu sync.Mutex | ||
| } | ||
|
|
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| const ( | ||
| MaxTransactionAmount = 10000.0 | ||
| ) | ||
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| type AccountError struct { | ||
| ID string | ||
| Owner string | ||
| } | ||
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| func (e *AccountError) Error() string { | ||
| return fmt.Sprintf("account error: %s: %s", e.ID, e.Owner) | ||
| } | ||
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| type InsufficientFundsError struct { | ||
| Balance float64 | ||
| Amount float64 | ||
| } | ||
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| func (e *InsufficientFundsError) Error() string { | ||
| return fmt.Sprintf("insufficient funds: balance $%.2f, attempted to withdraw $%.2f", e.Balance, e.Amount) | ||
| } | ||
|
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| type NegativeAmountError struct { | ||
| Amount float64 | ||
| } | ||
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| func (e *NegativeAmountError) Error() string { | ||
| return fmt.Sprintf("negative amount: $%.2f", e.Amount) | ||
| } | ||
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| type ExceedsLimitError struct { | ||
| Amount float64 | ||
| Limit float64 | ||
| } | ||
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| func (e *ExceedsLimitError) Error() string { | ||
| return fmt.Sprintf("amount $%.2f exceeds limit $%.2f", e.Amount, e.Limit) | ||
| } | ||
|
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| func NewBankAccount(id, owner string, initialBalance, minBalance float64) (*BankAccount, error) { | ||
| if id == "" || owner == "" { | ||
| return nil, &AccountError{ | ||
| ID: id, | ||
| Owner: owner, | ||
| } | ||
| } | ||
|
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| if initialBalance < 0 { | ||
| return nil, &NegativeAmountError{Amount: initialBalance} | ||
| } | ||
| if minBalance < 0 { | ||
| return nil, &NegativeAmountError{Amount: minBalance} | ||
| } | ||
| if initialBalance < minBalance { | ||
| return nil, &InsufficientFundsError{ | ||
| Balance: initialBalance, | ||
| Amount: minBalance, | ||
| } | ||
| } | ||
|
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| return &BankAccount{ | ||
| ID: id, | ||
| Owner: owner, | ||
| Balance: initialBalance, | ||
| MinBalance: minBalance, | ||
| }, nil | ||
| } | ||
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| func (a *BankAccount) Deposit(amount float64) error { | ||
| if err := validateAmount(amount); err != nil { | ||
| return err | ||
| } | ||
|
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| a.mu.Lock() | ||
| defer a.mu.Unlock() | ||
| a.Balance += amount | ||
| return nil | ||
| } | ||
|
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| func (a *BankAccount) Withdraw(amount float64) error { | ||
| if err := validateAmount(amount); err != nil { | ||
| return err | ||
| } | ||
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| a.mu.Lock() | ||
| defer a.mu.Unlock() | ||
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| if a.Balance-amount < a.MinBalance { | ||
| return &InsufficientFundsError{ | ||
| Balance: a.Balance, | ||
| Amount: amount, | ||
| } | ||
| } | ||
|
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| a.Balance -= amount | ||
| return nil | ||
| } | ||
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| func (a *BankAccount) Transfer(amount float64, target *BankAccount) error { | ||
| if a == target { | ||
| return nil | ||
| } | ||
|
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| if err := validateAmount(amount); err != nil { | ||
| return err | ||
| } | ||
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| first, second := a, target | ||
| if first.ID > second.ID { | ||
| first, second = second, first | ||
| } | ||
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| first.mu.Lock() | ||
| defer first.mu.Unlock() | ||
| second.mu.Lock() | ||
| defer second.mu.Unlock() | ||
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| if a.Balance-amount < a.MinBalance { | ||
| return &InsufficientFundsError{ | ||
| Balance: a.Balance, | ||
| Amount: amount, | ||
| } | ||
| } | ||
|
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| a.Balance -= amount | ||
| target.Balance += amount | ||
|
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| return nil | ||
| } | ||
|
Comment on lines
+114
to
+144
Contributor
There was a problem hiding this comment. 📐 Maintainability & Code Quality | 🟡 Minor | ⚡ Quick win 🧩 Analysis chain🏁 Script executed: #!/bin/bash
# Search for Transfer-related tests in the challenge-7 test file
rg -n -C3 'TestTransfer' challenge-7/solution-template_test.goRepository: RezaSi/go-interview-practice Length of output: 302 🏁 Script executed: #!/bin/bash
set -euo pipefail
# Show the Transfer test and nearby helpers with line numbers
sed -n '240,360p' challenge-7/solution-template_test.go | cat -nRepository: RezaSi/go-interview-practice Length of output: 4295 🏁 Script executed: #!/bin/bash
set -euo pipefail
# Look for any other transfer-focused tests or self-transfer coverage
rg -n -C2 'self-transfer|Transfer\(|Concurrent.*Transfer|TestTransfer' challenge-7Repository: RezaSi/go-interview-practice Length of output: 17520 🏁 Script executed: #!/bin/bash
set -euo pipefail
# Inspect the Transfer implementation and the test file around any concurrency helpers
sed -n '1,220p' challenge-7/submissions/onomica/solution-template.go | cat -nRepository: RezaSi/go-interview-practice Length of output: 4110 🏁 Script executed: #!/bin/bash
set -euo pipefail
# Search for any dedicated self-transfer or concurrent transfer test cases
rg -n -C3 'self.?transfer|concurrent transfer|Transfer test|TestTransfer|go func\(\).*Transfer|\.Transfer\(' challenge-7/solution-template_test.go challenge-7Repository: RezaSi/go-interview-practice Length of output: 2771 Add self-transfer and concurrency cases to |
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| func validateAmount(amount float64) error { | ||
| if amount < 0 { | ||
| return &NegativeAmountError{Amount: amount} | ||
| } | ||
| if amount > MaxTransactionAmount { | ||
| return &ExceedsLimitError{Amount: amount, Limit: MaxTransactionAmount} | ||
| } | ||
| return nil | ||
| } | ||
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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
Self-transfer skips amount validation.
The
a == targetearly return at Line 115 happens beforevalidateAmountat Line 119, soTransfer(-100, account)orTransfer(MaxTransactionAmount+1, account)returnsnilinstead of the expectedNegativeAmountError/ExceedsLimitError. Move validation before the self-transfer check to keep the error contract consistent withDepositandWithdraw.🔧 Proposed fix
func (a *BankAccount) Transfer(amount float64, target *BankAccount) error { + if err := validateAmount(amount); err != nil { + return err + } + if a == target { return nil } - if err := validateAmount(amount); err != nil { - return err - } - first, second := a, target📝 Committable suggestion