import { ref } from 'vue'

/**
 * @fileoverview Composable for managing form completion time.
 * Includes persistence in localStorage via pendingSubmission.
 */
export function useFormTimer(pendingSubmission) {
  // Reactive state for timer
  const startTime = ref(null)
  const completionTime = ref(null)
  const isTimerActive = ref(false)
  const isInitialized = ref(false)

  /**
   * Loads timer data from localStorage if available.
   * @returns {Boolean} Whether data was loaded successfully
   */
  const loadFromLocalStorage = () => {
    if (import.meta.server || !pendingSubmission) return false
    
    const savedTimer = pendingSubmission.getTimer()
    if (savedTimer) {
      startTime.value = parseInt(savedTimer)
      return true
    }
    return false
  }

  /**
   * Saves the current start time to localStorage.
   */
  const saveToLocalStorage = () => {
    if (import.meta.server || !pendingSubmission) return
    
    if (startTime.value) {
      pendingSubmission.setTimer(startTime.value.toString())
    } else {
      pendingSubmission.removeTimer()
    }
  }

  /**
   * Starts the timer if not already active.
   * Will load from localStorage on first call if available.
   */
  const start = () => {
    if (isTimerActive.value) {
      return
    }
    
    // If this is the first time starting, try to load from localStorage
    if (!isInitialized.value) {
      isInitialized.value = true
      loadFromLocalStorage()
    }
    
    // Only set a new start time if one doesn't exist already
    if (!startTime.value) {
      startTime.value = Date.now()
    }
    
    isTimerActive.value = true
    saveToLocalStorage()
  }

  /**
   * Stops the timer if active and calculates completion time.
   */
  const stop = () => {
    if (!isTimerActive.value) {
      return
    }
    
    if (startTime.value) {
      completionTime.value = Math.round((Date.now() - startTime.value) / 1000) // Time in seconds
    } else {
      completionTime.value = null
    }
    
    isTimerActive.value = false
    
    // Don't clear local storage on stop - only on reset or explicit removal
  }

  /**
   * Resets the timer state and clears localStorage.
   */
  const reset = () => {
    startTime.value = null
    completionTime.value = null
    isTimerActive.value = false
    
    if (pendingSubmission) {
      pendingSubmission.removeTimer()
    }
  }

  /**
   * Returns the calculated completion time.
   * @returns {Number|null} Completion time in seconds, or null if not available.
   */
  const getCompletionTime = () => {
    return completionTime.value
  }

  // Expose reactive state and methods
  return {
    isTimerActive, // Expose reactive status
    completionTime, // Expose reactive completion time
    start,
    stop,
    reset,
    getCompletionTime,
  }
}