qcast-front/src/util/calc-utils.js

export const createCalculator = (options = {}) => {
  const state = {
    currentOperand: '',
    previousOperand: '',
    operation: undefined,
    shouldResetDisplay: false,
    allowNegative: options.allowNegative ?? true,
    allowDecimal: options.allowDecimal ?? true,
    allowZero: options.allowZero ?? true,
    decimalPlaces: options.decimalPlaces ?? null,
  }
  
  // Expose state for debugging and direct access
  const getState = () => ({ ...state })

  const clear = () => {
    state.currentOperand = ''
    state.previousOperand = ''
    state.operation = undefined
    state.shouldResetDisplay = false
    return state.currentOperand
  }

  const deleteNumber = () => {
    if (state.currentOperand.length <= 1) {
      state.currentOperand = '0'
    } else {
      state.currentOperand = state.currentOperand.toString().slice(0, -1)
    }
    return state.currentOperand
  }

  const appendNumber = (number) => {
    if (number === '.' && !state.allowDecimal) return state.currentOperand
    if (number === '.' && state.currentOperand.includes('.')) return state.currentOperand

    if (state.shouldResetDisplay) {
      state.currentOperand = number.toString()
      state.shouldResetDisplay = false
    } else {
      if (state.currentOperand === '0' && number !== '.') {
        state.currentOperand = number.toString()
      } else {
        state.currentOperand = state.currentOperand.toString() + number.toString()
      }
    }
    return state.currentOperand
  }

  const chooseOperation = (operation) => {
    if (operation === '-' && state.currentOperand === '0' && state.previousOperand === '' && state.allowNegative) {
      state.currentOperand = '-'
      return state.currentOperand
    }

    if (state.currentOperand === '' || state.currentOperand === '-') return state.currentOperand
    
    // If there's a previous operation, compute it first
    if (state.previousOperand !== '') {
      compute()
    }

    state.operation = operation
    state.previousOperand = state.currentOperand
    state.currentOperand = ''
    return state.previousOperand + state.operation
  }

  const compute = () => {
    // If there's no operation, return the current value
    if (!state.operation) return parseFloat(state.currentOperand || '0')
    
    // If there's no current operand but we have a previous one, use previous as current
    if (state.currentOperand === '' && state.previousOperand !== '') {
      state.currentOperand = state.previousOperand
    }
    
    const prev = parseFloat(state.previousOperand)
    const current = parseFloat(state.currentOperand)
    
    if (isNaN(prev) || isNaN(current)) return 0
    
    let result
    switch (state.operation) {
      case '+':
        result = prev + current
        break
      case '-':
        result = prev - current
        break
      case '×':
        result = prev * current
        break
      case '÷':
        if (current === 0) {
          state.currentOperand = 'Error'
          return 0
        }
        result = prev / current
        break
      default:
        return parseFloat(state.currentOperand || '0')
    }
    
    // Apply formatting and constraints
    if (state.decimalPlaces !== null) {
      result = Number(result.toFixed(state.decimalPlaces))
    }
    
    if (!state.allowDecimal) {
      result = Math.round(result)
    }
    
    if (!state.allowNegative && result < 0) {
      result = 0
    }
    
    if (!state.allowZero && result === 0) {
      result = 1
    }
    
    // Update state
    state.currentOperand = result.toString()
    state.previousOperand = ''
    state.operation = undefined
    state.shouldResetDisplay = true
    
    return result
  }
  
  // Getter methods for the calculator state
  const getCurrentOperand = () => state.currentOperand
  const getPreviousOperand = () => state.previousOperand
  const getOperation = () => state.operation
  const getDisplayValue = () => {
    if (state.operation && state.previousOperand) {
      return `${state.previousOperand} ${state.operation} ${state.currentOperand || ''}`.trim()
    }
    return state.currentOperand
  }

  return {
    // Core calculator methods
    clear,
    delete: deleteNumber, // Alias for deleteNumber for compatibility
    deleteNumber,
    appendNumber,
    chooseOperation,
    compute,
    
    // State getters
    getDisplayValue,
    getCurrentOperand,
    getPreviousOperand,
    getOperation,
    
    // Direct state access (for debugging)
    getState,
    
    // Direct property access (for compatibility with CalcInput.jsx)
    get currentOperand() { return state.currentOperand },
    get previousOperand() { return state.previousOperand },
    get operation() { return state.operation },
    get shouldResetDisplay() { return state.shouldResetDisplay },
    
    // Setter for direct property access (if needed)
    set currentOperand(value) { state.currentOperand = value },
    set previousOperand(value) { state.previousOperand = value },
    set operation(value) { state.operation = value },
    set shouldResetDisplay(value) { state.shouldResetDisplay = value }
  }
}