<template>
  <div class="h-full w-full">
    <div class="h-full flex items-center justify-center">
      <div style="width: 100px; max-width: 100px" class="h-full hidden sm:flex items-center overflow-x-hidden justify-center">
        <span v-if="hasPrev" class="material-icons text-white text-opacity-50 hover:text-opacity-80 cursor-pointer text-6xl" @mousedown.prevent @click="prev">chevron_left</span>
      </div>
      <div id="frame" class="w-full" style="height: 80%">
        <div id="viewer"></div>
      </div>
      <div style="width: 100px; max-width: 100px" class="h-full hidden sm:flex items-center justify-center overflow-x-hidden">
        <span v-if="hasNext" class="material-icons text-white text-opacity-50 hover:text-opacity-80 cursor-pointer text-6xl" @mousedown.prevent @click="next">chevron_right</span>
      </div>
    </div>
  </div>
</template>

<script>
import ePub from 'epubjs'

/**
 * @typedef {object} EpubReader
 * @property {ePub.Book} book
 * @property {ePub.Rendition} rendition
 */
export default {
  props: {
    url: String,
    libraryItem: {
      type: Object,
      default: () => {}
    }
  },
  data() {
    return {
      windowWidth: 0,
      /** @type {ePub.Book} */
      book: null,
      /** @type {ePub.Rendition} */
      rendition: null
    }
  },
  computed: {
    /** @returns {string} */
    libraryItemId() {
      return this.libraryItem?.id
    },
    hasPrev() {
      return !this.rendition?.location?.atStart
    },
    hasNext() {
      return !this.rendition?.location?.atEnd
    },
    /** @returns {Array<ePub.NavItem>} */
    chapters() {
      return this.book ? this.book.navigation.toc : []
    },
    userMediaProgress() {
      if (!this.libraryItemId) return
      return this.$store.getters['user/getUserMediaProgress'](this.libraryItemId)
    },
    localStorageLocationsKey() {
      return `ebookLocations-${this.libraryItemId}`
    },
    readerWidth() {
      if (this.windowWidth < 640) return this.windowWidth
      return this.windowWidth - 200
    }
  },
  methods: {
    prev() {
      return this.rendition?.prev()
    },
    next() {
      return this.rendition?.next()
    },
    goToChapter(href) {
      return this.rendition?.display(href)
    },
    keyUp(e) {
      const rtl = this.book.package.metadata.direction === 'rtl'
      if ((e.keyCode || e.which) == 37) {
        return rtl ? this.next() : this.prev()
      } else if ((e.keyCode || e.which) == 39) {
        return rtl ? this.prev() : this.next()
      }
    },
    /**
     * @param {object} payload
     * @param {string} payload.ebookLocation - CFI of the current location
     * @param {string} payload.ebookProgress - eBook Progress Percentage
     */
    updateProgress(payload) {
      this.$axios.$patch(`/api/me/progress/${this.libraryItemId}`, payload).catch((error) => {
        console.error('EpubReader.updateProgress failed:', error)
      })
    },
    getAllEbookLocationData() {
      const locations = []
      let totalSize = 0 // Total in bytes

      for (const key in localStorage) {
        if (!localStorage.hasOwnProperty(key) || !key.startsWith('ebookLocations-')) {
          continue
        }

        try {
          const ebookLocations = JSON.parse(localStorage[key])
          if (!ebookLocations.locations) throw new Error('Invalid locations object')

          ebookLocations.key = key
          ebookLocations.size = (localStorage[key].length + key.length) * 2
          locations.push(ebookLocations)
          totalSize += ebookLocations.size
        } catch (error) {
          console.error('Failed to parse ebook locations', key, error)
          localStorage.removeItem(key)
        }
      }

      // Sort by oldest lastAccessed first
      locations.sort((a, b) => a.lastAccessed - b.lastAccessed)

      return {
        locations,
        totalSize
      }
    },
    /** @param {string} locationString */
    checkSaveLocations(locationString) {
      const maxSizeInBytes = 3000000 // Allow epub locations to take up to 3MB of space
      const newLocationsSize = JSON.stringify({ lastAccessed: Date.now(), locations: locationString }).length * 2

      // Too large overall
      if (newLocationsSize > maxSizeInBytes) {
        console.error('Epub locations are too large to store. Size =', newLocationsSize)
        return
      }

      const ebookLocationsData = this.getAllEbookLocationData()

      let availableSpace = maxSizeInBytes - ebookLocationsData.totalSize

      // Remove epub locations until there is room for locations
      while (availableSpace < newLocationsSize && ebookLocationsData.locations.length) {
        const oldestLocation = ebookLocationsData.locations.shift()
        console.log(`Removing cached locations for epub "${oldestLocation.key}" taking up ${oldestLocation.size} bytes`)
        availableSpace += oldestLocation.size
        localStorage.removeItem(oldestLocation.key)
      }

      console.log(`Cacheing epub locations with key "${this.localStorageLocationsKey}" taking up ${newLocationsSize} bytes`)
      this.saveLocations(locationString)
    },
    /** @param {string} locationString */
    saveLocations(locationString) {
      localStorage.setItem(
        this.localStorageLocationsKey,
        JSON.stringify({
          lastAccessed: Date.now(),
          locations: locationString
        })
      )
    },
    loadLocations() {
      const locationsObjString = localStorage.getItem(this.localStorageLocationsKey)
      if (!locationsObjString) return null

      const locationsObject = JSON.parse(locationsObjString)

      // Remove invalid location objects
      if (!locationsObject.locations) {
        console.error('Invalid epub locations stored', this.localStorageLocationsKey)
        localStorage.removeItem(this.localStorageLocationsKey)
        return null
      }

      // Update lastAccessed
      this.saveLocations(locationsObject.locations)

      return locationsObject.locations
    },
    /** @param {string} location - CFI of the new location */
    relocated(location) {
      if (this.userMediaProgress?.ebookLocation === location.start.cfi) {
        return
      }

      if (location.end.percentage) {
        this.updateProgress({
          ebookLocation: location.start.cfi,
          ebookProgress: location.end.percentage
        })
      } else {
        this.updateProgress({
          ebookLocation: location.start.cfi
        })
      }
    },
    initEpub() {
      /** @type {EpubReader} */
      const reader = this

      /** @type {ePub.Book} */
      reader.book = new ePub(reader.url, {
        width: this.readerWidth,
        height: window.innerHeight - 50
      })

      /** @type {ePub.Rendition} */
      reader.rendition = reader.book.renderTo('viewer', {
        width: this.readerWidth,
        height: window.innerHeight * 0.8
      })

      // load saved progress
      reader.rendition.display(this.userMediaProgress?.ebookLocation || reader.book.locations.start)

      // load style
      reader.rendition.themes.default({ '*': { color: '#fff!important' } })

      reader.book.ready.then(() => {
        // set up event listeners
        reader.rendition.on('relocated', reader.relocated)
        reader.rendition.on('keydown', reader.keyUp)

        let touchStart = 0
        let touchEnd = 0
        reader.rendition.on('touchstart', (event) => {
          touchStart = event.changedTouches[0].screenX
        })

        reader.rendition.on('touchend', (event) => {
          touchEnd = event.changedTouches[0].screenX
          const touchDistanceX = Math.abs(touchEnd - touchStart)
          if (touchStart < touchEnd && touchDistanceX > 120) {
            this.next()
          }
          if (touchStart > touchEnd && touchDistanceX > 120) {
            this.prev()
          }
        })

        // load ebook cfi locations
        const savedLocations = this.loadLocations()
        if (savedLocations) {
          reader.book.locations.load(savedLocations)
        } else {
          reader.book.locations.generate().then(() => {
            this.checkSaveLocations(reader.book.locations.save())
          })
        }
      })
    },
    resize() {
      this.windowWidth = window.innerWidth
      this.rendition?.resize(this.readerWidth, window.innerHeight * 0.8)
    }
  },
  beforeDestroy() {
    window.removeEventListener('resize', this.resize)
    this.book?.destroy()
  },
  mounted() {
    this.windowWidth = window.innerWidth
    window.addEventListener('resize', this.resize)
    this.initEpub()
  }
}
</script>
