feat(utils): slice

Signed-off-by: Lexus Drumgold <[email protected]>

src/types/__tests__/state.spec-d.ts

@@ -3,6 +3,7 @@
  * @module esast-util-attach-comments/types/tests/unit-d/State
  */
 
+import type { Optional } from '@flex-development/tutils'
 import type { Comment } from 'estree'
 import type TestSubject from '../state'
 
@@ -16,4 +17,10 @@ describe('unit-d:types/State', () => {
   it('should match [index: number]', () => {
     expectTypeOf<TestSubject>().toHaveProperty('index').toEqualTypeOf<number>()
   })
+
+  it('should match [leave?: boolean]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('leave')
+      .toEqualTypeOf<Optional<boolean>>()
+  })
 })

src/types/state.ts

@@ -22,6 +22,11 @@ type State = {
    * Index of current comment.
    */
   index: number
+
+  /**
+   * Visiting nodes on exit?
+   */
+  leave?: boolean
 }
 
 export type { State as default }

src/utils/__tests__/compare.spec.ts

@@ -8,7 +8,15 @@ import testSubject from '../compare'
 
 describe('unit:utils/compare', () => {
   it('should return Number.NaN if comparison cannot be made', () => {
-    expect(testSubject({}, {}, true)).to.be.NaN
+    // Arrange
+    const cases: Parameters<typeof testSubject>[] = [
+      [],
+      [{}, null],
+      [null, {}, true]
+    ]
+
+    // Act + Expect
+    cases.forEach(params => expect(testSubject(...params)).to.be.NaN)
   })
 
   describe('position', () => {

src/utils/__tests__/slice.spec.ts

@@ -0,0 +1,61 @@
+/**
+ * @file Unit Tests - slice
+ * @module esast-util-attach-comments/utils/tests/unit/slice
+ */
+
+import type { State } from '#src/types'
+import type { NewExpression } from 'estree'
+import testSubject from '../slice'
+
+describe('unit:utils/slice', () => {
+  let node: NewExpression
+  let state: State
+
+  beforeAll(() => {
+    state = {
+      comments: [
+        {
+          position: {
+            end: { column: 33, line: 11, offset: 411 },
+            start: { column: 18, line: 11, offset: 396 }
+          },
+          type: 'Block',
+          value: ' @__PURE__ '
+        },
+        {
+          position: {
+            end: { column: 27, line: 14, offset: 535 },
+            start: { column: 12, line: 14, offset: 520 }
+          },
+          type: 'Block',
+          value: ' @__PURE__ '
+        }
+      ],
+      index: 0
+    }
+
+    node = {
+      arguments: [],
+      callee: {
+        name: 'Set',
+        position: {
+          end: { column: 41, line: 11, offset: 419 },
+          start: { column: 38, line: 11, offset: 416 }
+        },
+        type: 'Identifier'
+      },
+      position: {
+        end: { column: 43, line: 11, offset: 421 },
+        start: { column: 34, line: 11, offset: 412 }
+      },
+      type: 'NewExpression'
+    }
+  })
+
+  it('should return slice from state.comments', () => {
+    expect(testSubject(state, node))
+      .to.be.an('array')
+      .of.length(1)
+      .with.deep.ordered.members([state.comments[0]])
+  })
+})

src/utils/compare.ts

@@ -3,6 +3,7 @@
  * @module esast-util-attach-comments/utils/compare
  */
 
+import type { Nilable } from '@flex-development/tutils'
 import type { Comment, Node } from 'estree'
 
 declare module 'estree' {
@@ -28,15 +29,15 @@ type Field = 'end' | 'start'
  *
  * @this {void}
  *
- * @param {Pick<Comment, 'position'>} comment - Comment node
- * @param {Pick<Comment | Node, 'position'>} node - Node to check
+ * @param {Nilable<Pick<Comment, 'position'>>?} [comment] - Comment node
+ * @param {Nilable<Pick<Comment | Node, 'position'>>?} [node] - Node to check
  * @param {boolean?} [end] - Use `end` position of `node` in comparsion?
  * @return {number} Comparison result
  */
 function compare(
   this: void,
-  comment: Pick<Comment, 'position'>,
-  node: Pick<Comment | Node, 'position'>,
+  comment?: Nilable<Pick<Comment, 'position'>>,
+  node?: Nilable<Pick<Comment | Node, 'position'>>,
   end?: boolean
 ): number {
   /**
@@ -47,7 +48,7 @@ function compare(
   const field: Field = end ? 'end' : 'start'
 
   // compare positions
-  if (comment.position?.start && node.position?.[field]) {
+  if (comment?.position?.start && node?.position?.[field]) {
     return (
       comment.position.start.line - node.position[field].line ||
       comment.position.start.column - node.position[field].column

src/utils/index.ts

@@ -5,3 +5,4 @@
 
 export { default as compare } from './compare'
 export { default as keycheck } from './keycheck'
+export { default as slice } from './slice'

src/utils/slice.ts

@@ -0,0 +1,42 @@
+/**
+ * @file Utilities - slice
+ * @module esast-util-attach-comments/utils/slice
+ */
+
+import type { State } from '#src/types'
+import type { Comment, Node } from 'estree'
+import compare from './compare'
+
+/**
+ * Get a comments slice.
+ *
+ * @see {@linkcode Comment}
+ * @see {@linkcode Node}
+ * @see {@linkcode State}
+ *
+ * @internal
+ *
+ * @this {void}
+ *
+ * @param {State} state - Visitor state
+ * @param {Node} node - Node being visited
+ * @return {Comment[]} Slice from `state.comments`
+ */
+function slice(this: void, state: State, node: Node): Comment[] {
+  /**
+   * Slice result.
+   *
+   * @const {Comment[]} result
+   */
+  const result: Comment[] = []
+
+  // get slice
+  while (
+    state.comments[state.index] &&
+    compare(state.comments[state.index], node, state.leave) < 1
+  ) result.push(state.comments[state.index++]!)
+
+  return result
+}
+
+export default slice