@sap/cds/lib/core/entities.js

SAP Cloud Application Programming Model - CDS for Node.js

const { LinkedDefinitions, struct, type } = require ('./classes')
const _is_cached = Symbol('is cached')
const _derived = Symbol('derived')


class entity extends struct {
  is (kind) { return kind === 'entity' || kind === 'view' && !!this.query || super.is(kind) }

  /**
   * Experimental API to write:
   * ```js
   * SELECT.from(Foo.as('bar')) // ... as alternative to:
   * SELECT.from(Foo).alias('bar')
   * ```
   */
  as (alias) { return { ntt:this, ref:[this.name], as:alias } }

  get keys() {
    return this._elements ('key')
  }
  get associations() {
    return this._elements ('isAssociation')
  }
  get compositions() {
    return this._elements ('isComposition')
  }
  _elements (kind, _default = null) {
    const derived = this.own(_derived, ()=>({}))
    if (kind in derived) return derived[kind]
    const {elements} = this, dict = new LinkedDefinitions; let any = _default
    for (let e in elements) if (elements[e][kind]) (any = dict)[e] = elements[e]
    return derived[kind] = any
  }

  toJSON() {
    return this.own('query') ? {...this} : super.toJSON(this)
  }
  toString() {
    return this.name.replace(/\./g,'_')
  }
}


class Association extends type {

  is(kind) { return kind === 'Association' || super.is(kind) }

  get is2many() { return !this.is2one }
  get is2one() {
    let c = this.cardinality
    return !c || c.max === 1 || (!c.max && !c.targetMax) || c.targetMax === 1
  }

  set foreignKeys(k) { this.set('foreignKeys', k) }
  get foreignKeys() {
    const keys = this.keys; if (!keys) return this.foreignKeys = undefined
    if (!Object.keys(keys).length) return this.foreignKeys = null
    const foreignKeys = new LinkedDefinitions
    for (const k of keys) {
      const el = k.ref.reduce((target,n)=> target.elements[n], this._target)
      const as = k.as || k.ref.at(-1)
      foreignKeys[as] = Object.create (el, { name:{value:as}, notNull: {value:true} }) //, parent:{value:this} })
      // For structures, foreign keys must be provided, (autogenerated) UUIDs are skipped for validation
      // REVISIT: We should change the line above to set parent correctly, as in the commented tail part.
      // But that breaks code in _runtime which expects it to be the wrong parent.
    }
    return this.foreignKeys = foreignKeys
  }

  set keys(k) { super.keys = k }
  get keys() {
    if (this.on || this.is2many || !this._target) return this.set('_keys', undefined)
    const keys=[], tks = this._target.keys
    for (let k in tks) keys.push({ ref: [tks[k].name] })
    return this.keys = keys
  }

  /**
   * Gets the foreign key data for a given managed association from inbound data
   * converted to an object that can be used as a where clause filter to fetch
   * from the assoc's target entity. The function correctly handles renamed
   * foreign keys.
   *
   * @example
   * entity Books { //...
   *   author : Association to Authors { ID:id } // renamed foreign key
   * }
   *
   * @example
   * let { Books, Authors } = srv.entities
   * let { author } = Books.elements
   * let data = { // inbound data, e.g. from req.data
   *   title: 'Foo',
   *   author_id: 111
   * }
   * let entry = author.refIn(data)
   * //> { ref: [ {id:'Authors', where:[ {ref:['ID']}, '=', {val:111} ]} ]}
   * await SELECT.one(entry)
   * await db.exists(entry)
   */
  refIn (d) {
    if (!this.keys) throw new Error (`Can't collect filter data for unmanaged associations`)
    const value = this.dataIn(d); if (!value) return
    const where={}; for (let {ref:[r],as} of this.keys) where[r] = value[as||r]
    const q = SELECT.from (this._target, where)
    return q.SELECT.from
  }

  /**
   * Overriding implementation in base class to handle data for to-many Associations.
   */
  dataIn (d, prefix='') {
    if (this.is2many) {
      const key = this.name, _key = '_'+key; if (_key in d) return d[_key]
      const input = d[key]; if (input[_is_cached]) return input
      if (Array.isArray(input)) {
        const value = d[key].map (each => this._target.dataIn (each,'',true))
        if (!prefix && d._hull) d._hull[key] = Object.defineProperty(value, _is_cached, {value:true})
        return value
      }
    }
    else return struct.prototype.dataIn.call (this, d, prefix)
  }
}

class Composition extends Association {

  is(kind) { return kind === 'Composition' || super.is(kind) }

}

module.exports = { entity, Association, Composition }