basic delta implementation

src/utils/Delta.js

@@ -0,0 +1,177 @@
+import * as object from 'lib0/object'
+import * as array from 'lib0/array'
+
+/**
+ * @typedef {InsertOp|RetainOp|DeleteOp} DeltaOp
+ */
+
+/**
+ * @typedef {{ [key: string]: any }} FormattingAttributes
+ */
+
+/**
+ * @typedef {Object} Attribution
+ * @property {boolean} [Attribution.isDeleted]
+ * @property {boolean} [Attribution.isAdded]
+ * @property {string} [Attribution.creator]
+ * @property {number} [Attribution.timestamp]
+ */
+
+export class InsertOp {
+  /**
+   * @param {string} insert
+   * @param {FormattingAttributes|null} attributes
+   * @param {Attribution|null} attribution
+   */
+  constructor (insert, attributes, attribution) {
+    this.insert = insert
+    this.attributes = attributes
+    this.attribution = attribution
+  }
+  toJSON () {
+    return object.assign({ insert: this.insert }, this.attributes ? { attributes: this.attributes } : {}, this.attribution ? { attribution: this.attribution } : {})
+  }
+}
+
+class DeleteOp {
+  /**
+   * @param {number} len
+   */
+  constructor (len) {
+    this.delete = len
+  }
+  toJSON () {
+    return { delete: this.delete }
+  }
+}
+
+class RetainOp {
+  /**
+   * @param {number} retain
+   * @param {FormattingAttributes|null} attributes
+   * @param {Attribution|null} attribution
+   */
+  constructor (retain, attributes, attribution) {
+    this.retain = retain
+    this.attributes = attributes
+    this.attribution = attribution
+  }
+  toJSON () {
+    return object.assign({ retain: this.retain }, this.attributes ? { attributes: this.attributes } : {}, this.attribution ? { attribution: this.attribution } : {})
+  }
+}
+
+export class Delta {
+  constructor () {
+    /**
+     * @type {Array<DeltaOp>}
+     */
+    this.ops = []
+  }
+  toJSON () {
+    return { ops: this.ops.map(o => o.toJSON()) }
+  }
+}
+
+/**
+ * Helper function to merge attribution and attributes. The latter input "wins".
+ *
+ * @template {{ [key: string]: any }} T
+ * @param {T | null} a
+ * @param {T | null} b
+ */
+const mergeAttrs = (a, b) => a == null ? b : (b == null ? a : object.assign({}, a, b))
+
+export class DeltaBuilder extends Delta {
+  constructor () {
+    super()
+    /**
+     * @private
+     * @type {FormattingAttributes?}
+     */
+    this._useAttributes = null
+    /**
+     * @private
+     * @type {Attribution?}
+     */
+    this._useAttribution = null
+    /**
+     * @private
+     * @type {DeltaOp?}
+     */
+    this._lastOp = null
+  }
+
+  /**
+   * @param {FormattingAttributes} attributes
+   * @return {this}
+   */
+  useAttributes (attributes) {
+    if (this._useAttributes === attributes) return this
+    this._useAttributes = object.assign({}, attributes)
+    if (this._lastOp?.constructor !== DeleteOp) this._lastOp = null
+    return this
+  }
+
+  /**
+   * @param {Attribution} attribution
+   */
+  useAttribution (attribution) {
+    if (this._useAttribution === attribution) return this
+    this._useAttribution = object.assign({}, attribution)
+    if (this._lastOp?.constructor !== DeleteOp) this._lastOp = null
+    return this
+  }
+
+  /**
+   * @param {string} insert
+   * @param {FormattingAttributes?} attributes
+   * @param {Attribution?} attribution
+   * @return {this}
+   */
+  insert (insert, attributes = null, attribution = null) {
+    if (attributes === null && attribution === null && this._lastOp instanceof InsertOp) {
+      this._lastOp.insert += insert
+    } else {
+      this.ops.push(this._lastOp = new InsertOp(insert, mergeAttrs(this.useAttributes, attributes), mergeAttrs(this._useAttribution, attribution)))
+    }
+    return this
+  }
+
+  /**
+   * @param {number} retain
+   * @param {FormattingAttributes?} attributes
+   * @param {Attribution?} attribution
+   * @return {this}
+   */
+  retain (retain, attributes = null, attribution = null) {
+    if (attributes === null && attribution === null && this._lastOp instanceof RetainOp) {
+      this._lastOp.retain += retain
+    } else {
+      this.ops.push(this._lastOp = new RetainOp(retain, mergeAttrs(this.useAttributes, attributes), mergeAttrs(this._useAttribution, attribution)))
+    }
+    return this
+  }
+
+  /**
+   * @param {number} len
+   * @return {this}
+   */
+  delete (len) {
+    if (this._lastOp instanceof DeleteOp) {
+      this._lastOp.delete += len
+    } else {
+      this.ops.push(this._lastOp = new DeleteOp(len))
+    }
+    return this
+  }
+
+  /**
+   * @return {Delta}
+   */
+  done () {
+    return this
+  }
+}
+
+export const create = () => new DeltaBuilder()

tests/delta.tests.js

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+import * as t from 'lib0/testing'
+import * as delta from '../src/utils/Delta.js'
+
+/**
+ * @param {t.TestCase} _tc
+ */
+export const testDelta = _tc => {
+  const d = delta.create().insert('hello').insert(' ').useAttributes({ bold: true }).insert('world').useAttribution({ creator: 'tester' }).insert('!').done()
+  t.compare(d.toJSON().ops, [{ insert: 'hello' }, { insert: ' world', attributes: { bold: true } }, { insert: '!', attributes: { bold: true }, attribution: { creator: 'tester' } }])
+}
+