geek-calc/specs/001-build-a-single/data-model.md

Data Model: Geek Calculator

Entities

Calculation Expression

• Representation: String containing numbers, operators (+, -, ×, ÷), parentheses, percentage, +/- signs
• Validation: Must follow valid mathematical expression syntax rules
• State transitions: In-progress expression → evaluated expression → stored in history

Calculation Result

• Representation: Number (JavaScript number type, may be Infinity or finite value)
• Validation: Must be a numeric result from evaluation
• State transitions: Calculated from expression → displayed → stored in history

RPN Stack

• Representation: Array of numbers representing operands in Reverse Polish Notation
• Operations: Push, pop, peek, clear, size
• Validation: Elements must be valid numbers
• State transitions: Empty → populated with operands → modified through RPN operations

Calculation History Entry

• Fields:
  • expression (string): The original input expression
  • result (number): The calculated result
  • timestamp (Date): When the calculation was completed
  • id (string): Unique identifier for recall
• Validation: Expression and result must be valid
• State transitions: New entry → stored → accessed → potentially deleted when limit reached

Application Settings

• Fields:
  • theme (string): 'dark' or other theme options
  • mode (string): 'standard' or 'rpn' for calculation mode
  • historyLimit (number): Maximum number of history entries to store
• Validation: Values must be from predefined sets
• State transitions: Default settings → user modified → saved to localStorage

User Input State

• Fields:
  • currentValue (string): The current value being entered
  • operator (string): The current operator in use
  • previousValue (number): The previous operand
  • calculationPending (boolean): Whether a calculation is ready to execute
• Validation: Values must be consistent with calculator state
• State transitions: Initial state → value entry → operator selection → result calculation