const r2 = require('r2')
const path = require('path')
const fs = require('fs')
const { once, EventEmitter } = require('events')
const { inherits } = require('util')
const getPost = require('mediumexporter').getPost
const { createClient } = require('webdav')
const readline = require('readline')
const { markdown } = require('markdown')
const GhostAdminAPI = require('@tryghost/admin-api')
const { Canvas, Image } = require('canvas')
const slugify = require('underscore.string/slugify')
const Rembrandt = require('rembrandt')
const nodepub = require('nodepub')
const cheerio = require('cheerio')

const config = require('./config')

class Seance {
  constructor(...args) {
    this.MEDIUM_IMG_CDN = 'https://miro.medium.com/fit/c/'

    try {
      this.ghostAdmin = new GhostAdminAPI({
        url: config.ghost.url,
        version: config.ghost.version,
        key: config.ghost.admin_key,
      })
    } catch(err) {
      console.error('Your Ghost isn\'t configured. Please run `seance setup` to fix this!')
    }

    /**
     * function [fetchFromMedium]
     * @returns [string] status
    */
  }

    async fetchFromMedium (mediumUrl, options = {
        json: null,
      }) {

      this.emit('update', {
        status: 'starting',
        message: `Fetching: ${mediumUrl}`,
        loglevel: 'info'
      })

      var output = path.join(process.env.PWD, 'content')

      var json

      if (!options.json) {
        json = await this.fetchMediumJSON(mediumUrl)
      } else {
        json = options.json
      }

      // use mediumexporter's getPost function to fetch a Medium post
      const post = await getPost(mediumUrl, {
          returnObject: true,
          output: output,
          postJSON: json
        }).catch((err) => {
          return {
            error: err,
          }
        })

      // set output folder path
      // this is based on what mediumexporter chooses as the output folder
      var outputFolder = path.join(output, post.slug)

      this.emit('update', {
        status: 'normal',
        message: `Saving to: ${outputFolder}`,
        loglevel: 'info'
      })

      if (!fs.existsSync(path.join(outputFolder, post.slug))) {
        fs.mkdirSync(outputFolder, { recursive: true })
      }

      // mediumexporter writes a plain .md file if the post has no media
      // if that is the case, we should create the subfolder manually
      // and copy the data there.
      if (fs.existsSync(path.join(output, post.slug + '.md'))) {
        fs.renameSync(
          path.join(output, post.slug + '.md'),
          path.join(outputFolder, 'index.md')
        )
      }

      // generate metadata
      const metadata = JSON.stringify({
        title: post.title,
        subtitle: post.subtitle,
        author: post.author || "",
        authors: post.authors || [],
        date: new Date(post.date),
        tags: post.tags,
        url: post.url,
        slug: post.slug,
        images: post.images,
        featuredImage: post.featuredImage,
      })

      // write metadata to output folder
      await fs.promises.writeFile(path.join(outputFolder, 'metadata.json'), metadata)
      return post
    };


  /**
   * function [pushToGhost]
   * @description
   * Pre-processes and uploads the given article to Ghost
   *
   * @param {Boolean} options.noUpload Skip uploading of images
   * @param {Boolean} options.noPush Skip pushing to Ghost; just generate the file
   * @param {Boolean} options.dryRun Combination of noUpload and noPush
   * @returns [object] object containing details of the uploaded Ghost post
  */
  async pushToGhost (postSlug, options={}) {
    this.emit('update', {
      status: 'starting',
      message: 'Starting upload: ' + postSlug,
      loglevel: 'info'
    })

    if (!!options.dryRun) {
      options.noUpload = true
      options.noPush = true
    }

    console.log('noUpload', options.noUpload)

    // Decide working path
    var postFolder = path.resolve('content/' + postSlug)

    // Verify file exists
    if (!fs.existsSync(postFolder)) {

      this.emit('error', {
        message: 'Could not find post folder! Is it fetched?',
      })

      return false
    }

    // Decide file
    const postContent = path.join(postFolder, 'index.md')
    const postOutput = path.join(postFolder, 'ghost.md')

    // Verify post exists
    if (!fs.existsSync(postContent)) {

      this.emit('error', {
        message: "Could not find 'index.md' in " + postSlug + "! Is it fetched?",
      })

      return false
    }

    // Decide WebDAV upload path
    var current_date = new Date()

    const uploadPath = path.join(
      current_date.getUTCFullYear().toString(),
      (current_date.getUTCMonth() + 1).toString(),
      postSlug
    )

    // Path where WebDAV files will be placed (eg. https://example.com:2078)
    const davPath = path.join(config.webdav.path_prefix, uploadPath)

    // Public path to upload those files (eg. https://media.example.com/uploads)
    // We'll do it directly since path.join mangles the protocol
    const uploadedPath = config.webdav.uploaded_path_prefix + '/' + uploadPath

    // load metadata file
    this.emit('update', {
      status: 'starting',
      message: 'Loading metadata',
      loglevel: 'debug'
    })

    var postMetaFile = path.join(postFolder, 'metadata.json')
    let postMeta = await JSON.parse(await fs.promises.readFile(postMetaFile))

    // Process lines
    const readInterface = readline.createInterface({
      input: fs.createReadStream(postContent),
      output: process.stdout,
      terminal: false
    })

    const outStream = fs.createWriteStream(postOutput, { encoding: 'utf-8' })

    // We'll calculate these later since Medium messes it up sometimes
    let title = null
    let subtitle = null

    let reImage = new RegExp('^!\\[(.*)\\]\\((\\S+?)\\)(.*)')
    let reTitle = new RegExp('^#\ (.*)')
    let reSubtitle = new RegExp('^#+\ (.*)$')

    // Note down uploaded images
    var uploadedImages = []

    this.emit('update', {
      status: 'progress',
      progress: null, // we don't know the percentage
      message: 'Parsing post',
      loglevel: 'info'
    })

    for await (const line of readInterface) {
      // Line to output
      // Default is to make it same as input
      var newLine = line

      // Skip the header (and preceding blank lines)
      if (!title) {

        // blanks
        if (!line) continue

        // starting with a # (must be the title)
        let match = await reTitle.exec(line)
        if (match) {
          title = match[1]
          continue // no need to add line; it'll come automatically
        }
      } else if (!subtitle) {

        // check if it's a repeat of the title (Medium does that)
        if (line.endsWith(title)) continue

        // otherwise set the subtitle if it doesn't exist
        // or if it's a repeat of the title (Medium does that too)

        if (!subtitle && postMeta.subtitle == postMeta.title) {
          let match = await reSubtitle.exec(line)

          if (match) {
            subtitle = match[1]
            postMeta.subtitle = match[1]
          }
        }

      }

      // check for images
      var m = await reImage.exec(line)
      if (m) {
        // Get image name
        var imageAlt = m[1]
        var imageName = m[2].replace('*', '')
        var imagePath = path.join(postFolder, 'images', imageName)

        if (!fs.existsSync(imagePath)) {
          console.warn('Skipping missing image: ' + imageName)
        } else {
          // check for separator image
          var isScissors = await this.checkScissors(imagePath)
          if (isScissors) {
            newLine = '\n---\n'
          } else {
            // upload pic to server
            console.debug(`Adding to upload queue: ${imageName}`)
            uploadedImages.push(imageName)

            // Let's wait for the upload, just to avoid conflicts
            if (!options.noUpload) {
              await this.uploadDav(davPath, imagePath)
            }

            newLine = '![' + imageAlt + '](' + uploadedPath + '/' + imageName + ')'
          }
        }
      }

      outStream.write(newLine + '\n')
    }

    // Upload feature_image, if required
    var featuredImagePath
    if (!!postMeta.featuredImage) {
      var imageName = postMeta.featuredImage.replace('*', '')

      // if the image is listed in postMeta.images, it would have
      // already been uploaded
      if (uploadedImages.indexOf(imageName) != -1) {

        this.emit('update', {
            status: 'progress',
            progress: 95, // we don't know the percentage
            message: `Skipping feature image ${imageName}: already listed for upload`,
            loglevel: 'info'
          })

      } else {
        var imagePath = path.join(postFolder, 'images', imageName)

        // We can only upload if the file exists!
        if (!fs.existsSync(imagePath)) {

          this.emit('update', {
            status: 'progress',
            progress: 95, // we don't know the percentage
            message: `Skipping feature image "${imageName}": file not found`,
            loglevel: 'warning'
          })

        } else {

          this.emit('update', {
            status: 'progress',
            progress: 95, // we don't know the percentage
            message: `Uploading feature image: ${imageName}`,
            loglevel: 'info'
          })

          if (!options.noUpload) {
            this.uploadDav(davPath, imagePath)
          }

          featuredImagePath = uploadedPath + '/' + imageName
        }
      }
    }

    // calculate users
    let users = []
    postMeta.authors.forEach((user) => {
      users.push({slug: user.username})
    })

    // This will happen once all the line reading is finished
    // Uploads will continue in paralell though
    this.emit('update', {
      status: 'progress',
      progress: 100, // we don't know the percentage
      message: 'Uploading to Ghost',
      loglevel: 'info'
    })

    if (!options.noPush) {
      let res = await this.ghostAdmin.posts.add({
        title: postMeta.title,
        custom_excerpt: postMeta.subtitle || null,
        tags: postMeta.tags,
        authors: users,
        html: markdown.toHTML(await fs.promises.readFile(postOutput, 'utf-8')),
        feature_image: featuredImagePath
      }, {source: 'html'})

      // Check if user was added
      if (res.primary_author.id == 1) {
        this.emit('notification', {
          message: `WARNING: The admin editor, "${res.primary_author.name}", is set as author for this post. If this is incorrect, there was some problem matching usernames. Please check and set it manually.`,
        })
      }

      this.emit('update', {
        status: 'progress',
        progress: 100, // we don't know the percentage
        message: 'Post conveyed successfully',
        loglevel: 'info'
      })

      return {
        slug: res.slug,
        id: res.id,
        uuid: res.uuid,
        preview_url: res.url,
        primary_author: res.primary_author,
        title: res.title,
        subtitle: res.custom_excerpt,
        status: res.status,
      }
    } else {
      // just return without pushing to Ghost
      return {
        slug: postSlug,
        id: 0,
        uuid: 0,
        preview_url: null,
        primary_author: {},
        title: postMeta.title,
        subtitle: postMeta.subtitle,
        status: 'none',
      }
    }
  }


  /**
   * function [mediumToGhost]
   * @returns [string] status
  */
  mediumToGhost (mediumUrl) {
    console.info('Copying: ' + mediumUrl);
  }


  async fetchMediumJSON(mediumUrl) {
    var json
    var text

    if (mediumUrl.match(/^http/i)) {
      // remove the anchors at the end
      mediumUrl = mediumUrl.replace(/#.*$/, '')

      // intelligently add ?json attribute
      if (mediumUrl.indexOf('format=json') == -1) {
        if (mediumUrl.indexOf('?') == -1) {
          mediumUrl = `${mediumUrl}?format=json`
        } else {
          mediumUrl = `${mediumUrl}&format=json`
        }
      }

      // let's get it!
      const response = await fetch(mediumUrl)
      text = await response.text()
    } else if (fs.existsSync(mediumUrl)) {
      text = (await fs.promises.readFile(mediumUrl)).toString()
    } else {
      throw { error: 'URL must be a Medium URL or existing JSON file' }
    }

    try {
      json = await JSON.parse(text.substr(text.indexOf('{')))
    } catch(err) {
      throw { error: 'You JSON seems to be malformed' }
    }

    return json;
  }

  /**
   * function [checkScissors]
   * @returns [boolean] matchStatus
  */

  async checkScissors (imagePath) {
    // Decide "separator" image
    // If set, images matching this will be ignored and replaced
    // with a horizontal-rule ("---" in markdown) instead.
    let scissors = config.scissors

      // if scissors not set, return false
    // (it's never a scissors since it never matches)
    if (!scissors) {

      this.emit('update', {
        status: 'normal',
        message: '[scissors] No scissors set, so rejecting all images',
        loglevel: 'warning'
      })

      return false
    } else {

      /* First, check that the image has finished loading
       * (we don't use this, because Rembrandt loads it again
       * on its own, which is messy but what to do ¯\_(ツ)_/¯
       */

      try {
        let ctx = new Canvas().getContext('2d')
        let img = new Image()
        img.src = imagePath
        ctx.drawImage(img, 0, 0, img.width, img.height)
      } catch (err) {
        this.emit('update', {
            status: 'normal',
            message: `[scissors] Skipping scissors check:${err.message}`,
            loglevel: 'warning'
          })
          return false
      }

      // Check if given image matches the scissors
      try {
        let isScissors = new Rembrandt({
          imageA: scissors,
          imageB: imagePath,
          thresholdType: Rembrandt.THRESHOLD_PERCENT,
          maxThreshold: 0.1
        })
        let result = await isScissors.compare()
        return result.passed
      } catch (err) {

        this.emit('update', {
          status: 'normal',
          message: `[scissors] Skipping scissors check:${err.message}`,
          loglevel: 'warning'
        })

        return false
      }
    }
  }

  /**
   * function [createUser]
   * @returns [object] ghost data json
  */
  async generateUserData (mediumUsername, email) {

    this.emit('update', {
      status: 'starting',
      message: `Creating: @${mediumUsername} (email: ${email})`,
      loglevel: 'debug'
    })


    const mediumUrl = `https://medium.com/@${mediumUsername}/?format=json`;
    const json = await this.fetchMediumJSON(mediumUrl);

    if (!json.success) {
      this.emit('error', {
        message: `Error: ${json.error}`,
      })
      return false
    }

    this.emit('update', {
      status: 'normal',
      message: `Name: ${json.payload.user.name}`,
      loglevel: 'debug'
    })

    this.emit('update', {
      status: 'normal',
      message: `Bio: ${json.payload.user.bio}`,
      loglevel: 'debug'
    })

    // Download and upload image

    let imageId = json.payload.user.imageId
    this.emit('update', {
      status: 'normal',
      message: `Profile pic: ${imageId}`,
      loglevel: 'debug'
    })

    let imagePath = this.MEDIUM_IMG_CDN + '256/256/' + imageId
    let filetype = imageId.split('.')[imageId.split('.').length - 1]
    let fileName = `${mediumUsername}.${filetype}`
    let filePath = path.join(process.env.PWD, fileName)

    this.emit('update', {
      status: 'normal',
      message: `Fetching profile pic: ${imagePath}`,
      loglevel: 'info'
    })

    const response = await (await r2.get(imagePath).response).buffer()
    await await fs.promises.writeFile(filePath, response, 'base64')

    this.emit('update', {
      status: 'normal',
      message: `Uploading profile pic: ${imagePath}`,
      loglevel: 'info'
    })

    await this.uploadDav(path.join(config.webdav.path_prefix,'avatars'),
      filePath)

    // Generate Ghost JSON

    const ghostData = {
      data: {
        users: [
          {
            id: 1,
            slug: json.payload.user.username,
            bio: json.payload.user.bio,
            email: email,
            name: json.payload.user.name,
            profile_image: config.webdav.uploaded_path_prefix + '/avatars/' + fileName
          }
        ]
      },
      meta: {
        exported_on: new Date,
        version: '2.14.0'
      }
    }

    return(JSON.stringify(ghostData))
  };

  async createDirIfNotExist (client, folder) {
    // recursively create subfolders if they don't exist.

    //safety: don't touch directories outside WEBDAV_PATH_PREFIX
    if (!folder.startsWith(config.webdav.path_prefix)) {
      throw new Error(`Cannot create directories outside ${config.webdav.path_prefix}`)
    }

    // check the folder
    await client.stat(folder)
    .catch(async (err) => {
      if (!err.response) {
        // no response! Maybe a network error or something :P
        console.error(`[dav-upload:folder] Error creating folder "${folder}"`)
        console.error(`[dav-upload:folder] ${err.toJSON().message}`)
        console.error('[dav-upload:folder] Please check your Internet connection and try again')
        return false
      } else if (err.response.status == 404) {

        // it's a 404, so we'll create the directory
        this.emit('update', {
          status: 'normal',
          message: `Noting missing subdirectory: ${folder}`,
          loglevel: 'debug'
        })

        // first, create the parent directory (if required)
        if (!await this.createDirIfNotExist(client, path.dirname(folder))) {
          // if not created, we fail too :-/
          return false
        }

        this.emit('update', {
          status: 'normal',
          message: `Creating missing subdirectory: ${folder}`,
          loglevel: 'debug'
        })

        // then, create the current directory
        await client.createDirectory(folder)
        .catch(async (err) => {
          if (err.response.status == 405) { // Method Not Allowed
            // Maybe the directory's already been created in the meantime?
            await client.stat(folder)
            .catch((err2) => {
              // Bad guess. Panic (and raise the original error)

              this.emit('update', {
                status: 'error',
                message: `Error: ${err.toJSON().message}\nWe're not sure what went wrong. Help!`,
                loglevel: 'error'
              })

              throw err
            })
          } else {
            // what's this? Panic!
            this.emit('update', {
                status: 'error',
                message: `Error: ${err.toJSON().message}\nWe're not sure what went wrong. Help!`,
                loglevel: 'error'
              })

            throw err
          }
        })
      } else {

        // it's not a 404; we don't know how to handle this. Panic!
        this.emit('update', {
          status: 'error',
          message: 'An unknown error occured. Help!',
          loglevel: 'error'
        })
        console.error(err.toJSON())
        throw err
      }
    })
    return true
  }

  /**
   * function [uploadDav]
   * @returns [string] status
  */
  async uploadDav (dirPath, filePath) {

    // connect to webdav
    const client = createClient(
      config.webdav.server_url,
      {
        username: config.webdav.username,
        password: config.webdav.password,
        digest: config.webdav.use_digest
      })

    // create directory if not exists
    console.debug(`[dav-upload] Loading ${dirPath}`)
    if (!await this.createDirIfNotExist(client, dirPath)) {
      console.error(`[dav-upload] Could not upload ${path.basename(filePath)} :(`)
      return false
    }

    // upload a file
    console.debug('Uploading file')
    const outStream = client.createWriteStream(
      path.join(dirPath, path.basename(filePath))
    )
    outStream.on('finish', () => console.debug('Uploaded successfully.'))

    const inStream = fs.createReadStream(filePath)
    .pipe(outStream)

    return true
  }


  /**
   * function [fetchToEpub]
   * @description fetches posts from Ghost and packs them into an epub
   * @options.id unique ID for the generated epub
   * @options.title title of the generated epub
   * @options.author author of the generated epub
   * @options.language language of the book
   * @genre genre of the book
   * @cover cover image to use
   * @returns [string] status
  */
  async fetchToEpub (postSlugs, options = {}) {
    if (!options.title) options.title = 'Seance Collection'
    if (!options.author) options.author = 'Seance'
    if (!options.language) options.language = 'en'
    if (!options.genre) options.genre = 'Unknown'
    if (!options.coverImage) options.coverImage = 'random-cover.jpg'
    if (!options.outputFolder) options.outputFolder = '.'


    console.log(`Fetching: ${postSlugs}`)
    let allPosts = []

    // first, fetch all the posts
    for (let slug of postSlugs) {
      console.log(`Fetching: ${slug}`)
      let post = await this.ghostAdmin.posts.read({slug: slug}, {formats: ['html']})
      allPosts.push(post)
    }

    // prepare for image downloads
    let pics = []
    let picFolder = path.join(options.outputFolder, 'seance-images')
    if (!fs.existsSync(picFolder)) {
      fs.mkdirSync(picFolder, { recursive: true })
    }

    // prepare array to collect processed posts
    let processedPosts = []

    for (let post of allPosts) {
      // decide a post slug, for future files
      let postSlug = slugify(post.title)

      // get the cover pic
      let featurePicTag
      if (!!post.feature_image) {
        let imgUrl = post.feature_image
        if (/^\/\//i.test(imgUrl)) {
          imgUrl = 'https:' + imgUrl
        } else if (!/^https?:\/\//i.test(imgUrl)) {
          imgUrl = 'https://' + imgUrl
        }
        let response = await (await r2.get(imgUrl).response).buffer()
        let ext = post.feature_image.split('.').pop()
        await await fs.promises.writeFile(path.join(picFolder, `${postSlug}.${ext}`), response, 'base64')
        featurePicTag = `<img src="../images/${postSlug}.${ext}"/>`
        pics.push(`${picFolder}/${postSlug}.${ext}`)
      }

      let c = cheerio.load(`${featurePicTag}<h1>${post.title}</h1>${post.html}`)

      // hunt for other pics
      // TODO: make asynchronous
      let picCounter = 0
      c('img').each(async function() {
        // skip if it's a local image
        if (c(this).attr('src').indexOf('../images') == 0) {
          return
        }

        // first, process the url
        let imgUrl = c(this).attr('src')
        console.log('Downloading:', imgUrl)
        if (/^\/\//i.test(imgUrl)) {
          imgUrl = 'https:' + imgUrl
        } else if (!/^https?:\/\//i.test(imgUrl)) {
          imgUrl = 'https://' + imgUrl
        }

        // now decide an output name
        let ext = c(this).attr('src').split('.').pop()
        let imageFile = path.join(picFolder, `${postSlug}-insert-${picCounter}.${ext}`)

        // note down our calculations
        c(this).attr('src', `../images/${postSlug}-insert-${picCounter}.${ext}`)
        pics.push(imageFile)
        picCounter = picCounter + 1

        // finally, download the images
        let response = await (await r2.get(imgUrl).response).buffer()
        await fs.promises.writeFile(imageFile, response, 'base64')
        console.log('Downloaded to:', imageFile)
      })

      processedPosts.push({
        title: post.title,
        body: c.html(),
      })
    }

    // decide metadata
    let metadata = {
      id: 'seance-test', // FIXME
      title: options.title,
      author: options.author,
      language: options.language,
      contents: 'Table of Contents',
      genre: options.genre,
      cover: options.coverImage,
      images: pics,
    }

    // create the ePub
    let epub = nodepub.document(metadata)

    // add the documents
    for (let post of processedPosts) {
      epub.addSection(post.title, post.body)
    }

    // generate it!
    await epub.writeEPUB(options.outputFolder, options.title)
  }

}

// Make Seance an EventEmitter
inherits(Seance, EventEmitter)

module.exports = {
  Seance
}