Fix linked account balance currency mismatch (#566)

* Fix linked account balance currency mismatch

When linking accounts from providers (Lunchflow, SimpleFIN, Enable Banking),
the initial sync was creating balances before the correct currency was known.
This caused:
1. Opening anchor entry created with default currency (USD/EUR)
2. First sync created balances with wrong currency
3. Later syncs created balances with correct currency
4. Both currency balances existed, charts showed wrong (zero) values

Changes:
- Add `skip_initial_sync` parameter to `Account.create_and_sync`
- Skip initial sync for linked accounts (provider sync handles it)
- Add currency filter to ChartSeriesBuilder query to only fetch
  balances matching the account's current currency

* Add migration script and add tests

* Update schema.rb

---------

Signed-off-by: soky srm <sokysrm@gmail.com>
Co-authored-by: sokie <sokysrm@gmail.com>

test/models/account_test.rb

@@ -14,6 +14,64 @@ class AccountTest < ActiveSupport::TestCase
     end
   end
 
+  test "create_and_sync calls sync_later by default" do
+    Account.any_instance.expects(:sync_later).once
+
+    account = Account.create_and_sync({
+      family: @family,
+      name: "Test Account",
+      balance: 100,
+      currency: "USD",
+      accountable_type: "Depository",
+      accountable_attributes: {}
+    })
+
+    assert account.persisted?
+    assert_equal "USD", account.currency
+    assert_equal 100, account.balance
+  end
+
+  test "create_and_sync skips sync_later when skip_initial_sync is true" do
+    Account.any_instance.expects(:sync_later).never
+
+    account = Account.create_and_sync(
+      {
+        family: @family,
+        name: "Linked Account",
+        balance: 500,
+        currency: "EUR",
+        accountable_type: "Depository",
+        accountable_attributes: {}
+      },
+      skip_initial_sync: true
+    )
+
+    assert account.persisted?
+    assert_equal "EUR", account.currency
+    assert_equal 500, account.balance
+  end
+
+  test "create_and_sync creates opening anchor with correct currency" do
+    Account.any_instance.stubs(:sync_later)
+
+    account = Account.create_and_sync(
+      {
+        family: @family,
+        name: "Test Account",
+        balance: 1000,
+        currency: "GBP",
+        accountable_type: "Depository",
+        accountable_attributes: {}
+      },
+      skip_initial_sync: true
+    )
+
+    opening_anchor = account.valuations.opening_anchor.first
+    assert_not_nil opening_anchor
+    assert_equal "GBP", opening_anchor.entry.currency
+    assert_equal 1000, opening_anchor.entry.amount
+  end
+
   test "gets short/long subtype label" do
     investment = Investment.new(subtype: "hsa")
     account = @family.accounts.create!(

test/models/balance/chart_series_builder_test.rb

@@ -127,4 +127,197 @@ class Balance::ChartSeriesBuilderTest < ActiveSupport::TestCase
 
     assert_equal expected, builder.balance_series.map { |v| v.value.amount }
   end
+
+  test "uses balances matching account currency for correct chart data" do
+    # This test verifies that chart data is built from balances with proper currency.
+    # Data integrity is maintained by:
+    # 1. Account.create_and_sync with skip_initial_sync: true for linked accounts
+    # 2. Migration cleanup_orphaned_currency_balances for existing data
+    account = accounts(:depository)
+    account.balances.destroy_all
+
+    # Account is in USD, create balances in USD
+    create_balance(account: account, date: 2.days.ago.to_date, balance: 1000)
+    create_balance(account: account, date: 1.day.ago.to_date, balance: 1500)
+    create_balance(account: account, date: Date.current, balance: 2000)
+
+    builder = Balance::ChartSeriesBuilder.new(
+      account_ids: [ account.id ],
+      currency: "USD",
+      period: Period.custom(start_date: 2.days.ago.to_date, end_date: Date.current),
+      interval: "1 day"
+    )
+
+    series = builder.balance_series
+    assert_equal 3, series.size
+    assert_equal [ 1000, 1500, 2000 ], series.map { |v| v.value.amount }
+  end
+
+  test "balances are converted to target currency using exchange rates" do
+    # Create account with EUR currency
+    family = families(:dylan_family)
+    account = family.accounts.create!(
+      name: "EUR Account",
+      balance: 1000,
+      currency: "EUR",
+      accountable: Depository.new
+    )
+
+    account.balances.destroy_all
+
+    # Create balances in EUR (matching account currency)
+    create_balance(account: account, date: 1.day.ago.to_date, balance: 1000)
+    create_balance(account: account, date: Date.current, balance: 1200)
+
+    # Add exchange rate EUR -> USD
+    ExchangeRate.create!(date: 1.day.ago.to_date, from_currency: "EUR", to_currency: "USD", rate: 1.1)
+
+    # Request chart in USD (different from account's EUR)
+    builder = Balance::ChartSeriesBuilder.new(
+      account_ids: [ account.id ],
+      currency: "USD",
+      period: Period.custom(start_date: 1.day.ago.to_date, end_date: Date.current),
+      interval: "1 day"
+    )
+
+    series = builder.balance_series
+    # EUR balances converted to USD at 1.1 rate (LOCF for today)
+    assert_equal [ 1100, 1320 ], series.map { |v| v.value.amount }
+  end
+
+  test "linked account with orphaned currency balances shows correct values after cleanup" do
+    # This test reproduces the original bug scenario:
+    # 1. Linked account created with initial sync before correct currency was known
+    # 2. Opening anchor and first sync created balances with wrong currency (USD)
+    # 3. Provider sync updated account to correct currency (EUR) and created new balances
+    # 4. Both USD and EUR balances existed - charts showed wrong values
+    #
+    # The fix:
+    # 1. skip_initial_sync prevents this going forward
+    # 2. Migration cleans up orphaned balances for existing linked accounts
+
+    # Use the connected (linked) account fixture
+    linked_account = accounts(:connected)
+    linked_account.balances.destroy_all
+
+    # Simulate the bug: account is now EUR but has old USD balances from initial sync
+    linked_account.update!(currency: "EUR")
+
+    # Create orphaned balances in wrong currency (USD) - from initial sync before currency was known
+    Balance.create!(
+      account: linked_account,
+      date: 3.days.ago.to_date,
+      balance: 1000,
+      cash_balance: 1000,
+      currency: "USD", # Wrong currency!
+      start_cash_balance: 1000,
+      start_non_cash_balance: 0,
+      cash_inflows: 0,
+      cash_outflows: 0,
+      non_cash_inflows: 0,
+      non_cash_outflows: 0,
+      net_market_flows: 0,
+      cash_adjustments: 0,
+      non_cash_adjustments: 0,
+      flows_factor: 1
+    )
+
+    Balance.create!(
+      account: linked_account,
+      date: 2.days.ago.to_date,
+      balance: 1100,
+      cash_balance: 1100,
+      currency: "USD", # Wrong currency!
+      start_cash_balance: 1100,
+      start_non_cash_balance: 0,
+      cash_inflows: 0,
+      cash_outflows: 0,
+      non_cash_inflows: 0,
+      non_cash_outflows: 0,
+      net_market_flows: 0,
+      cash_adjustments: 0,
+      non_cash_adjustments: 0,
+      flows_factor: 1
+    )
+
+    # Create correct balances in EUR - from provider sync after currency was known
+    create_balance(account: linked_account, date: 1.day.ago.to_date, balance: 5000)
+    create_balance(account: linked_account, date: Date.current, balance: 5500)
+
+    # Verify we have both currency balances (the bug state)
+    assert_equal 2, linked_account.balances.where(currency: "USD").count
+    assert_equal 2, linked_account.balances.where(currency: "EUR").count
+
+    # Simulate migration cleanup: delete orphaned balances with wrong currency
+    linked_account.balances.where.not(currency: linked_account.currency).delete_all
+
+    # Verify cleanup removed orphaned balances
+    assert_equal 0, linked_account.balances.where(currency: "USD").count
+    assert_equal 2, linked_account.balances.where(currency: "EUR").count
+
+    # Now chart should show correct EUR values
+    builder = Balance::ChartSeriesBuilder.new(
+      account_ids: [ linked_account.id ],
+      currency: "EUR",
+      period: Period.custom(start_date: 2.days.ago.to_date, end_date: Date.current),
+      interval: "1 day"
+    )
+
+    series = builder.balance_series
+    # After cleanup: only EUR balances exist, chart shows correct values
+    # Day 2 ago: 0 (no EUR balance), Day 1 ago: 5000, Today: 5500
+    assert_equal [ 0, 5000, 5500 ], series.map { |v| v.value.amount }
+  end
+
+  test "chart ignores orphaned currency balances via currency filter" do
+    # This test verifies the currency filter correctly ignores orphaned balances.
+    # The filter `b.currency = accounts.currency` ensures only valid balances are used.
+    #
+    # Bug scenario: Account currency changed from USD to EUR after initial sync,
+    # leaving orphaned USD balances. Without the filter, charts would show wrong values.
+
+    linked_account = accounts(:connected)
+    linked_account.balances.destroy_all
+
+    # Account is EUR but has orphaned USD balances (bug state)
+    linked_account.update!(currency: "EUR")
+
+    # Create orphaned USD balance (wrong currency)
+    Balance.create!(
+      account: linked_account,
+      date: 1.day.ago.to_date,
+      balance: 9999,
+      cash_balance: 9999,
+      currency: "USD", # Wrong currency - doesn't match account.currency (EUR)
+      start_cash_balance: 9999,
+      start_non_cash_balance: 0,
+      cash_inflows: 0,
+      cash_outflows: 0,
+      non_cash_inflows: 0,
+      non_cash_outflows: 0,
+      net_market_flows: 0,
+      cash_adjustments: 0,
+      non_cash_adjustments: 0,
+      flows_factor: 1
+    )
+
+    # Chart correctly ignores USD balance because account.currency is EUR
+    builder = Balance::ChartSeriesBuilder.new(
+      account_ids: [ linked_account.id ],
+      currency: "EUR",
+      period: Period.custom(start_date: 1.day.ago.to_date, end_date: Date.current),
+      interval: "1 day"
+    )
+
+    series = builder.balance_series
+
+    # Currency filter ensures orphaned USD balance (9999) is ignored
+    # Chart shows zeros because no EUR balances exist
+    assert_equal 2, series.size
+    assert_equal [ 0, 0 ], series.map { |v| v.value.amount }
+
+    # Verify the orphaned balance still exists in DB (migration will clean it up)
+    assert_equal 1, linked_account.balances.where(currency: "USD").count
+    assert_equal 0, linked_account.balances.where(currency: "EUR").count
+  end
 end