const uniqueSlug = require('unique-slug')
const fs = require('fs')
const path = require('path')
const findStorage = require('browser/lib/findStorage')
const mdurl = require('mdurl')
const fse = require('fs-extra')
const escapeStringRegexp = require('escape-string-regexp')
const sander = require('sander')

const STORAGE_FOLDER_PLACEHOLDER = ':storage'
const DESTINATION_FOLDER = 'attachments'

/**
 * @description
 * Copies a copy of an attachment to the storage folder specified by the given key and return the generated attachment name.
 * Renames the file to match a unique file name.
 *
 * @param {String} sourceFilePath The source path of the attachment to be copied
 * @param {String} storageKey Storage key of the destination storage
 * @param {String} noteKey Key of the current note. Will be used as subfolder in :storage
 * @param {boolean} useRandomName determines whether a random filename for the new file is used. If false the source file name is used
 * @return {Promise<String>} name (inclusive extension) of the generated file
 */
function copyAttachment (sourceFilePath, storageKey, noteKey, useRandomName = true) {
  return new Promise((resolve, reject) => {
    if (!sourceFilePath) {
      reject('sourceFilePath has to be given')
    }

    if (!storageKey) {
      reject('storageKey has to be given')
    }

    if (!noteKey) {
      reject('noteKey has to be given')
    }

    try {
      if (!fs.existsSync(sourceFilePath)) {
        reject('source file does not exist')
      }

      const targetStorage = findStorage.findStorage(storageKey)

      const inputFileStream = fs.createReadStream(sourceFilePath)
      let destinationName
      if (useRandomName) {
        destinationName = `${uniqueSlug()}${path.extname(sourceFilePath)}`
      } else {
        destinationName = path.basename(sourceFilePath)
      }
      const destinationDir = path.join(targetStorage.path, DESTINATION_FOLDER, noteKey)
      createAttachmentDestinationFolder(targetStorage.path, noteKey)
      const outputFile = fs.createWriteStream(path.join(destinationDir, destinationName))
      inputFileStream.pipe(outputFile)
      inputFileStream.on('end', () => {
        resolve(destinationName)
      })
    } catch (e) {
      return reject(e)
    }
  })
}

function createAttachmentDestinationFolder (destinationStoragePath, noteKey) {
  let destinationDir = path.join(destinationStoragePath, DESTINATION_FOLDER)
  if (!fs.existsSync(destinationDir)) {
    fs.mkdirSync(destinationDir)
  }
  destinationDir = path.join(destinationStoragePath, DESTINATION_FOLDER, noteKey)
  if (!fs.existsSync(destinationDir)) {
    fs.mkdirSync(destinationDir)
  }
}

/**
 * @description Moves attachments from the old location ('/images') to the new one ('/attachments/noteKey)
 * @param renderedHTML HTML of the current note
 * @param storagePath Storage path of the current note
 * @param noteKey Key of the current note
 */
function migrateAttachments (renderedHTML, storagePath, noteKey) {
  if (sander.existsSync(path.join(storagePath, 'images'))) {
    const attachments = getAttachmentsInContent(renderedHTML) || []
    if (attachments !== []) {
      createAttachmentDestinationFolder(storagePath, noteKey)
    }
    for (const attachment of attachments) {
      const attachmentBaseName = path.basename(attachment)
      const possibleLegacyPath = path.join(storagePath, 'images', attachmentBaseName)
      if (sander.existsSync(possibleLegacyPath)) {
        const destinationPath = path.join(storagePath, DESTINATION_FOLDER, attachmentBaseName)
        if (!sander.existsSync(destinationPath)) {
          sander.copyFileSync(possibleLegacyPath).to(destinationPath)
        }
      }
    }
  }
}

/**
 * @description Fixes the URLs embedded in the generated HTML so that they again refer actual local files.
 * @param {String} renderedHTML HTML in that the links should be fixed
 * @param {String} storagePath Path of the current storage
 * @returns {String} postprocessed HTML in which all :storage references are mapped to the actual paths.
 */
function fixLocalURLS (renderedHTML, storagePath) {
  return renderedHTML.replace(new RegExp(mdurl.encode(path.sep), 'g'), path.sep).replace(new RegExp(STORAGE_FOLDER_PLACEHOLDER, 'g'), 'file:///' + path.join(storagePath, DESTINATION_FOLDER))
}

/**
 * @description Generates the markdown code for a given attachment
 * @param {String} fileName Name of the attachment
 * @param {String} path Path of the attachment
 * @param {Boolean} showPreview Indicator whether the generated markdown should show a preview of the image. Note that at the moment only previews for images are supported
 * @returns {String} Generated markdown code
 */
function generateAttachmentMarkdown (fileName, path, showPreview) {
  return `${showPreview ? '!' : ''}[${fileName}](${path})`
}

/**
 * @description Handles the drop-event of a file. Includes the necessary markdown code and copies the file to the corresponding storage folder.
 * The method calls {CodeEditor#insertAttachmentMd()} to include the generated markdown at the needed place!
 * @param {CodeEditor} codeEditor Markdown editor. Its insertAttachmentMd() method will be called to include the markdown code
 * @param {String} storageKey Key of the current storage
 * @param {String} noteKey Key of the current note
 * @param {Event} dropEvent DropEvent
 */
function handleAttachmentDrop (codeEditor, storageKey, noteKey, dropEvent) {
  const file = dropEvent.dataTransfer.files[0]
  const filePath = file.path
  const originalFileName = path.basename(filePath)
  const fileType = file['type']

  copyAttachment(filePath, storageKey, noteKey).then((fileName) => {
    const showPreview = fileType.startsWith('image')
    const imageMd = generateAttachmentMarkdown(originalFileName, path.join(STORAGE_FOLDER_PLACEHOLDER, noteKey, fileName), showPreview)
    codeEditor.insertAttachmentMd(imageMd)
  })
}

/**
 * @description Creates a new file in the storage folder belonging to the current note and inserts the correct markdown code
 * @param {CodeEditor} codeEditor Markdown editor. Its insertAttachmentMd() method will be called to include the markdown code
 * @param {String} storageKey Key of the current storage
 * @param {String} noteKey Key of the current note
 * @param {DataTransferItem} dataTransferItem Part of the past-event
 */
function handlePastImageEvent (codeEditor, storageKey, noteKey, dataTransferItem) {
  if (!codeEditor) {
    throw new Error('codeEditor has to be given')
  }
  if (!storageKey) {
    throw new Error('storageKey has to be given')
  }

  if (!noteKey) {
    throw new Error('noteKey has to be given')
  }
  if (!dataTransferItem) {
    throw new Error('dataTransferItem has to be given')
  }

  const blob = dataTransferItem.getAsFile()
  const reader = new FileReader()
  let base64data
  const targetStorage = findStorage.findStorage(storageKey)
  const destinationDir = path.join(targetStorage.path, DESTINATION_FOLDER, noteKey)
  createAttachmentDestinationFolder(targetStorage.path, noteKey)

  const imageName = `${uniqueSlug()}.png`
  const imagePath = path.join(destinationDir, imageName)

  reader.onloadend = function () {
    base64data = reader.result.replace(/^data:image\/png;base64,/, '')
    base64data += base64data.replace('+', ' ')
    const binaryData = new Buffer(base64data, 'base64').toString('binary')
    fs.writeFileSync(imagePath, binaryData, 'binary')
    const imageReferencePath = path.join(STORAGE_FOLDER_PLACEHOLDER, noteKey, imageName)
    const imageMd = generateAttachmentMarkdown(imageName, imageReferencePath, true)
    codeEditor.insertAttachmentMd(imageMd)
  }
  reader.readAsDataURL(blob)
}

/**
 * @description Returns all attachment paths of the given markdown
 * @param {String} markdownContent content in which the attachment paths should be found
 * @returns {String[]} Array of the relative paths (starting with :storage) of the attachments of the given markdown
 */
function getAttachmentsInContent (markdownContent) {
  const preparedInput = markdownContent.replace(new RegExp(mdurl.encode(path.sep), 'g'), path.sep)
  const regexp = new RegExp(STORAGE_FOLDER_PLACEHOLDER + escapeStringRegexp(path.sep) + '?([a-zA-Z0-9]|-)*' + escapeStringRegexp(path.sep) + '[a-zA-Z0-9]+(\\.[a-zA-Z0-9]+)?', 'g')
  return preparedInput.match(regexp)
}

/**
 * @description Returns an array of the absolute paths of the attachments referenced in the given markdown code
 * @param {String} markdownContent content in which the attachment paths should be found
 * @param {String} storagePath path of the current storage
 * @returns {String[]} Absolute paths of the referenced attachments
 */
function getAbsolutePathsOfAttachmentsInContent (markdownContent, storagePath) {
  const temp = getAttachmentsInContent(markdownContent) || []
  const result = []
  for (const relativePath of temp) {
    result.push(relativePath.replace(new RegExp(STORAGE_FOLDER_PLACEHOLDER, 'g'), path.join(storagePath, DESTINATION_FOLDER)))
  }
  return result
}

/**
 * @description Moves the attachments of the current note to the new location.
 * Returns a modified version of the given content so that the links to the attachments point to the new note key.
 * @param {String} oldPath Source of the note to be moved
 * @param {String} newPath Destination of the note to be moved
 * @param {String} noteKey Old note key
 * @param {String} newNoteKey New note key
 * @param {String} noteContent Content of the note to be moved
 * @returns {String} Modified version of noteContent in which the paths of the attachments are fixed
 */
function moveAttachments (oldPath, newPath, noteKey, newNoteKey, noteContent) {
  const src = path.join(oldPath, DESTINATION_FOLDER, noteKey)
  const dest = path.join(newPath, DESTINATION_FOLDER, newNoteKey)
  if (fse.existsSync(src)) {
    fse.moveSync(src, dest)
  }
  return replaceNoteKeyWithNewNoteKey(noteContent, noteKey, newNoteKey)
}

/**
 * Modifies the given content so that in all attachment references the oldNoteKey is replaced by the new one
 * @param noteContent content that should be modified
 * @param oldNoteKey note key to be replaced
 * @param newNoteKey note key serving as a replacement
 * @returns {String} modified note content
 */
function replaceNoteKeyWithNewNoteKey (noteContent, oldNoteKey, newNoteKey) {
  if (noteContent) {
    return noteContent.replace(new RegExp(STORAGE_FOLDER_PLACEHOLDER + escapeStringRegexp(path.sep) + oldNoteKey, 'g'), path.join(STORAGE_FOLDER_PLACEHOLDER, newNoteKey))
  }
  return noteContent
}

/**
 * @description Deletes all :storage and noteKey references from the given input.
 * @param input Input in which the references should be deleted
 * @param noteKey Key of the current note
 * @returns {String} Input without the references
 */
function removeStorageAndNoteReferences (input, noteKey) {
  return input.replace(new RegExp(mdurl.encode(path.sep), 'g'), path.sep).replace(new RegExp(STORAGE_FOLDER_PLACEHOLDER + '(' + escapeStringRegexp(path.sep) + noteKey + ')?', 'g'), DESTINATION_FOLDER)
}

/**
 * @description Deletes the attachment folder specified by the given storageKey and noteKey
 * @param storageKey Key of the storage of the note to be deleted
 * @param noteKey Key of the note to be deleted
 */
function deleteAttachmentFolder (storageKey, noteKey) {
  const storagePath = findStorage.findStorage(storageKey)
  const noteAttachmentPath = path.join(storagePath.path, DESTINATION_FOLDER, noteKey)
  sander.rimrafSync(noteAttachmentPath)
}

/**
 * @description Deletes all attachments stored in the attachment folder of the give not that are not referenced in the markdownContent
 * @param markdownContent Content of the note. All unreferenced notes will be deleted
 * @param storageKey StorageKey of the current note. Is used to determine the belonging attachment folder.
 * @param noteKey NoteKey of the current note. Is used to determine the belonging attachment folder.
 */
function deleteAttachmentsNotPresentInNote (markdownContent, storageKey, noteKey) {
  const targetStorage = findStorage.findStorage(storageKey)
  const attachmentFolder = path.join(targetStorage.path, DESTINATION_FOLDER, noteKey)
  const attachmentsInNote = getAttachmentsInContent(markdownContent)
  const attachmentsInNoteOnlyFileNames = []
  if (attachmentsInNote) {
    for (let i = 0; i < attachmentsInNote.length; i++) {
      attachmentsInNoteOnlyFileNames.push(attachmentsInNote[i].replace(new RegExp(STORAGE_FOLDER_PLACEHOLDER + escapeStringRegexp(path.sep) + noteKey + escapeStringRegexp(path.sep), 'g'), ''))
    }
  }

  if (fs.existsSync(attachmentFolder)) {
    fs.readdir(attachmentFolder, (err, files) => {
      if (err) {
        console.error("Error reading directory '" + attachmentFolder + "'. Error:")
        console.error(err)
        return
      }
      files.forEach(file => {
        if (!attachmentsInNoteOnlyFileNames.includes(file)) {
          const absolutePathOfFile = path.join(targetStorage.path, DESTINATION_FOLDER, noteKey, file)
          fs.unlink(absolutePathOfFile, (err) => {
            if (err) {
              console.error("Could not delete '%s'", absolutePathOfFile)
              console.error(err)
              return
            }
            console.info("File '" + absolutePathOfFile + "' deleted because it was not included in the content of the note")
          })
        }
      })
    })
  } else {
    console.info("Attachment folder ('" + attachmentFolder + "') did not exist..")
  }
}

/**
 * Clones the attachments of a given note.
 * Copies the attachments to their new destination and updates the content of the new note so that the attachment-links again point to the correct destination.
 * @param oldNote Note that is being cloned
 * @param newNote Clone of the note
 */
function cloneAttachments (oldNote, newNote) {
  if (newNote.type === 'MARKDOWN_NOTE') {
    const oldStorage = findStorage.findStorage(oldNote.storage)
    const newStorage = findStorage.findStorage(newNote.storage)
    const attachmentsPaths = getAbsolutePathsOfAttachmentsInContent(oldNote.content, oldStorage.path) || []

    const destinationFolder = path.join(newStorage.path, DESTINATION_FOLDER, newNote.key)
    if (!sander.existsSync(destinationFolder)) {
      sander.mkdirSync(destinationFolder)
    }

    for (const attachment of attachmentsPaths) {
      const destination = path.join(newStorage.path, DESTINATION_FOLDER, newNote.key, path.basename(attachment))
      sander.copyFileSync(attachment).to(destination)
    }
    newNote.content = replaceNoteKeyWithNewNoteKey(newNote.content, oldNote.key, newNote.key)
  } else {
    console.debug('Cloning of the attachment was skipped since it only works for MARKDOWN_NOTEs')
  }
}

module.exports = {
  copyAttachment,
  fixLocalURLS,
  generateAttachmentMarkdown,
  handleAttachmentDrop,
  handlePastImageEvent,
  getAttachmentsInContent,
  getAbsolutePathsOfAttachmentsInContent,
  removeStorageAndNoteReferences,
  deleteAttachmentFolder,
  deleteAttachmentsNotPresentInNote,
  moveAttachments,
  cloneAttachments,
  migrateAttachments,
  STORAGE_FOLDER_PLACEHOLDER,
  DESTINATION_FOLDER
}