const fs = require('node:fs')
const path = require('node:path')
const async = require('async')
const debug = require('debug')('thumbsup:debug')
const fsextra = require('fs-extra')
const handlebars = require('handlebars')
const less = require('less')

class Theme {
  constructor (themeDir, destDir, opts) {
    // directory that contains the theme
    this.dir = path.resolve(themeDir)
    // target directory
    this.dest = path.resolve(destDir)
    // custom options
    this.opts = opts
  }

  // load all theme helpers
  // and copy assets into the output folder (static files, CSS...)
  prepare (done) {
    this.options = this.loadPackageOptions()
    this.dir = path.join(this.dir, this.options.themeRoot || '')
    // validate that the theme looks well structured
    this.validateStructure()
    // compiled template
    this.template = compileTemplate(path.join(this.dir, 'album.hbs'))
    this.loadPartials()
    this.loadHelpers()
    async.series([
      next => this.copyPublic(next),
      next => this.renderStyles(next)
    ], done)
  }

  // look for an explicit root in the theme's <package.json>
  loadPackageOptions () {
    try {
      const packagePath = path.join(this.dir, 'package.json')
      const contents = fs.readFileSync(packagePath).toString()
      const pkg = JSON.parse(contents)
      return pkg.thumbsup || {}
    } catch (ex) {
      debug('Theme does not have a package.json, using default options')
      return {}
    }
  }

  // make sure the given folder is a valid theme
  validateStructure () {
    if (!fs.existsSync(this.dir)) {
      throw new Error(`Theme does not exist: ${this.dir}`)
    }
    const template = fs.existsSync(path.join(this.dir, 'album.hbs'))
    const style = fs.existsSync(path.join(this.dir, 'theme.less'))
    if (!template || !style) {
      throw new Error(`Invalid theme structure in ${this.dir}`)
    }
  }

  // renders the given album HTML page
  render (targetPath, data, next) {
    const fullPath = path.join(this.dest, targetPath)
    debug(`Theme rendering ${targetPath}`)
    const contents = this.template(data)
    fs.mkdirSync(path.dirname(fullPath), { recursive: true })
    fs.writeFile(fullPath, contents, next)
  }

  // ------------------------
  // private methods
  // ------------------------

  loadPartials () {
    if (!isDirectory(path.join(this.dir, 'partials'))) {
      return
    }
    // load all files in the <partials> folder
    const partials = fs.readdirSync(path.join(this.dir, 'partials'))
    const isTemplate = filepath => path.extname(filepath) === '.hbs'
    partials.filter(isTemplate).forEach(filename => {
      debug(`Loading partial ${filename}`)
      const templateName = path.basename(filename, path.extname(filename))
      handlebars.registerPartial(templateName, compileTemplate(path.join(this.dir, 'partials', filename)))
    })
  }

  loadHelpers () {
    if (!isDirectory(path.join(this.dir, 'helpers'))) {
      return
    }
    // load all files in the <helpers> folder
    const helpers = fs.readdirSync(path.join(this.dir, 'helpers'))
    const isHelper = filepath => path.extname(filepath) === '.js'
    helpers.filter(isHelper).forEach(filename => {
      debug(`Loading helper ${filename}`)
      const name = path.basename(filename, path.extname(filename))
      const fullPath = path.join(this.dir, 'helpers', filename)
      handlebars.registerHelper(name, require(fullPath))
    })
  }

  renderStyles (done) {
    debug('Rendering theme styles')
    // full LESS content
    const themeFile = path.join(this.dir, 'theme.less')
    const themeLess = fs.readFileSync(themeFile, 'utf-8')
    // optional custom LESS file
    const customInclude = this.customStylesInclude()
    // now render both together
    const lessOptions = {
      paths: [this.dir]
    }
    less.render(themeLess + customInclude, lessOptions, (err, output) => {
      if (err) return done(err)
      const filename = this.opts.stylesheetName || 'theme.css'
      const dest = path.join(this.dest, 'public', filename)
      fs.mkdirSync(path.join(this.dest, 'public'), { recursive: true })
      fs.writeFile(dest, output.css, done)
    })
  }

  customStylesInclude () {
    const customPath = this.opts.customStylesPath
    if (customPath) {
      // see http://lesscss.org/features/#import-atrules-feature
      // we use (inline) to avoid processing raw CSS files
      const includeType = path.extname(customPath) === '.css' ? '(inline) ' : ''
      return `\n@import ${includeType}'${customPath}';`
    }
    return ''
  }

  copyPublic (done) {
    if (!isDirectory(path.join(this.dir, 'public'))) {
      return done()
    }
    // copy all files in the <public> folder
    const src = path.join(this.dir, 'public')
    const dest = path.join(this.dest, 'public')
    fsextra.copy(src, dest, done)
  }
}

function compileTemplate (hbsFile) {
  const src = fs.readFileSync(hbsFile)
  return handlebars.compile(src.toString())
}

function isDirectory (fullPath) {
  try {
    return fs.statSync(fullPath).isDirectory()
  } catch (ex) {
    return false
  }
}

module.exports = Theme