rdf-parser-csvw/lib/metadata/TableSchema.js

CSV on the Web parser

import url from 'node:url'
import difference from 'lodash/difference.js'
import uriTemplate from 'uri-templates'
import namespace from '../namespace.js'
import parseDateTime from '../parseDateTime.js'
import RdfUtils from './RdfUtils.js'

const defaultColumnNames = new Set(['_column', '_sourceColumn', '_row', '_sourceRow', '_name'])

class TableSchema {
  constructor (dataset, { root, baseIRI, factory, timezone } = {}) {
    this.factory = factory
    this.ns = namespace(this.factory)
    this.dataset = dataset
    this.root = root || RdfUtils.findNode(this.dataset, null, this.ns.tableSchema)
    this.baseIRI = baseIRI
    this.timezone = timezone

    this.aboutUrl = () => {
      return this.factory.blankNode()
    }

    this.parsedColumns = []
    this.allColumns = null

    if (this.dataset) {
      this.aboutUrl = this.parseAboutUrl() || this.aboutUrl
      this.propertyUrl = this.parsePropertyUrl()
      this.parseColumns()
    }
  }

  parseAboutUrl () {
    const aboutUrl = RdfUtils.findValue(this.dataset, this.root, this.ns.aboutUrl)

    if (!aboutUrl) {
      return
    }

    const aboutUrlTemplate = uriTemplate(aboutUrl)

    return row => {
      // eslint-disable-next-line
      return this.factory.namedNode(url.resolve(this.baseIRI, aboutUrlTemplate.fill(row))) // eslint-disable-line node/no-deprecated-api
    }
  }

  parsePropertyUrl () {
    const url = RdfUtils.findValue(this.dataset, this.root, this.ns.propertyUrl)

    if (!url) {
      return
    }

    return uriTemplate(url)
  }

  parseColumns () {
    const columnNode = RdfUtils.findNode(this.dataset, this.root, this.ns.column)

    this.parsedColumns = RdfUtils.parseArray(this.dataset, columnNode).map(node => {
      const titles = RdfUtils.findValues(this.dataset, node, this.ns.title)
      const name = RdfUtils.findValue(this.dataset, node, this.ns.name) || titles[0]
      const aboutUrl = RdfUtils.findValue(this.dataset, node, this.ns.aboutUrl)
      const language = RdfUtils.findValue(this.dataset, node, this.ns.lang)
      const nullValue = RdfUtils.findValue(this.dataset, node, this.ns.null) || ''
      const defaultValue = RdfUtils.findValue(this.dataset, node, this.ns.default)
      const propertyUrl = RdfUtils.findValue(this.dataset, node, this.ns.propertyUrl)
      const suppressOutput = RdfUtils.findValue(this.dataset, node, this.ns.suppressOutput)
      const virtual = RdfUtils.findValue(this.dataset, node, this.ns.virtual)
      const valueUrl = RdfUtils.findValue(this.dataset, node, this.ns.valueUrl)

      return {
        aboutUrl: aboutUrl && uriTemplate(aboutUrl),
        datatype: this.parseDatatype(node),
        language: language && uriTemplate(language),
        name,
        nullValue,
        defaultValue,
        propertyUrl: (propertyUrl && uriTemplate(propertyUrl)) || this.propertyUrl || this.defaultPropertyUrl(name),
        suppressOutput: suppressOutput === 'true',
        titles,
        virtual,
        valueUrl: valueUrl && uriTemplate(valueUrl)
      }
    })
  }

  parseDatatype (node) {
    const datatype = RdfUtils.findNode(this.dataset, node, this.ns.datatype)

    if (!datatype) {
      return this.defaultDatatype()
    }

    if (datatype.termType === 'NamedNode') {
      return { base: datatype.value }
    }

    const base = RdfUtils.findValue(this.dataset, datatype, this.ns.base)
    const format = RdfUtils.findValue(this.dataset, datatype, this.ns.format)

    return {
      base: this.factory.namedNode('http://www.w3.org/2001/XMLSchema#' + (base || 'string')),
      format
    }
  }

  columns ({ contentLine, row }) {
    try {
      if (!this.allColumns) {
        this.createAllColumns(row)
      }

      return this.allColumns.map(column => {
        const cellData = { ...row, _name: column.name }

        return {
          subject: this.subject(column, cellData),
          property: this.property(column, cellData),
          value: this.value(column, cellData)
        }
      }).filter(column => {
        return column.value !== undefined
      })
    } catch (cause) {
      const err = new Error(`could not parse content line ${contentLine}`)

      err.stack += `\nCaused by: ${cause.stack}`

      throw err
    }
  }

  subject (column, row) {
    if (!column.aboutUrl) {
      return null
    }

    // eslint-disable-next-line
    return this.factory.namedNode(url.resolve(this.baseIRI, column.aboutUrl.fill(row))) // eslint-disable-line node/no-deprecated-api
  }

  value (column, row) {
    if (column.suppressOutput) {
      return undefined
    }

    if (column.valueUrl) {
      return this.factory.namedNode(column.valueUrl.fill(row))
    }

    let value = column.titles.reduce((value, title) => {
      return value || row[title]
    }, '')

    if (value === '') {
      value = column.defaultValue
    }

    if (typeof value === 'undefined' || value === column.nullValue) {
      return undefined
    }

    if (column.datatype.base.value === this.ns.dateTime.value) {
      return this.factory.literal(parseDateTime(value, column.datatype.format, this.timezone).toISO(), this.ns.dateTime)
    }

    if (column.datatype.base.value === this.ns.date.value) {
      return this.factory.literal(parseDateTime(value, column.datatype.format, this.timezone).toFormat('yyyy-MM-dd'), this.ns.date)
    }

    if (column.datatype.base) {
      const language = column.language && column.language.fill(row).toLowerCase()

      return this.factory.literal(value, language || this.factory.namedNode(column.datatype.base))
    }
  }

  property (column, row) {
    return this.factory.namedNode(column.propertyUrl.fill(row))
  }

  createAllColumns (row) {
    const titles = this.parsedColumns.reduce((titles, column) => {
      return titles.concat(column.titles)
    }, [])

    const undefinedColumns = difference(Object.keys(row), titles).reduce((titles, title) => {
      if (defaultColumnNames.has(title)) {
        return titles
      }

      return [...titles, {
        name: title,
        titles: [title],
        propertyUrl: this.propertyUrl || this.defaultPropertyUrl(title),
        datatype: this.defaultDatatype()
      }]
    }, [])

    this.allColumns = this.parsedColumns.concat(undefinedColumns)
  }

  defaultPropertyUrl (name) {
    return {
      fill: () => {
        return this.baseIRI + '#' + encodeURI(name)
      }
    }
  }

  defaultDatatype () {
    return { base: this.ns.string.value }
  }
}

export default TableSchema