iOS app for calculating amortized loan payments and viewing current U.S. mortgage rates from the St. Louis Fed (FRED) API.

Bundle ID: com.groundspeedhq.Pay-Calc
Requirements: Xcode, iOS 18.6+ (Simulator or device)
Stack: Swift 5, SwiftUI, MVVM

• Payment — Loan amount, down payment, interest rate, and term; computes monthly payment with optional speech output. Optional schedule inputs: start date, extra payment per period, and lender name. After calculating, open the Loan Amortization Schedule report.
• Loan Amortization Schedule — Report screen with loan details, summary totals (scheduled payment, actual payments, total interest, etc.), and a full payment-by-payment schedule. Apple-style cards, monospaced numeric columns, horizontal scroll for the table. Toolbar actions for Export PDF, Export CSV, and Share (stubbed for future implementation).
• Rates — Live 30-year fixed, 15-year fixed, and 5/1 ARM rates from FRED (today vs. last week).

From the repo root:

# Build
xcodebuild -project Amortized.xcodeproj -scheme Amortized -configuration Debug -sdk iphonesimulator build

Or open Amortized.xcodeproj in Xcode and run on a simulator (recommended).

# List simulator IDs
xcodebuild -showdestinations

# Run all tests (replace <UUID> with a simulator ID)
xcodebuild -project Amortized.xcodeproj -scheme Amortized -destination 'platform=iOS Simulator,id=<UUID>' test

# Run a single test class
xcodebuild -project Amortized.xcodeproj -scheme Amortized -destination 'platform=iOS Simulator,id=<UUID>' -only-testing:AmortizedTests/ClassName test

Tests cover PaymentService (PMT calculations), FRED JSON decoding, and view models.

• Entry: AmortizedApp.swift — SwiftUI App with a TabView (Payment + Rates).
• UI: SwiftUI views: PaymentView (inputs + Calculate + “View Schedule”), AmortizationReportView (report with details card, summary card, and payment schedule table), RatesView. Reusable DetailRow and ScheduleTableRow for the report.
• Logic: PaymentService for monthly PMT and full amortization schedule (buildAmortizationSchedule); ApiService for FRED (30yr, 15yr, 5/1 ARM).
• Models: AmortizationModels.swift — AmortizationScheduleRow, AmortizationSummary. Rates for FRED display.
• Formatting: ReportFormatters — locale-aware currency, percent, and short-date strings for the report and export.

Payment flow: user enters loan parameters (and optionally start date, extra payment, lender) → Calculate → PaymentViewModel computes payment and builds schedule via PaymentService.buildAmortizationSchedule → View Schedule pushes AmortizationReportView with the same view model (single source of truth). Report does not recalculate; it displays stored schedule and summary.

Rates use FRED series: MORTGAGE30US, MORTGAGE15US, MORTGAGE5US. A FRED API key is required (configured in ApiService).