Fight Complexity with Functional Programming in Kotlin

A Metric-driven approach to reduce Cognitive Complexity in a code base, using Functional Programming, demoed hands-on, by solving a complex real-world ubiquitous design challenge - REST API Bulk Request Validation, with an extensible Framework that separates what-to-do (Validations) from how-to-do (Validation Orchestration). Let’s do a case study of a successful implementation done by our team in the world’s largest SaaS org, Salesforce, through our in-house baked FOSS library Vader.

Transcript

1. overfullstack.github.io
2. FP is cool , coz it’s complex enough to make devs feel like they are doing something smart! @GopalAkshintala - Some Manager (Not Mine!)
3. @GopalAkshintala
4. Dev Holy Wars @GopalAkshintala
5. IDE Theme Light Vs Dark @GopalAkshintala
6. Eclipse Vs Intellij @GopalAkshintala
7. OOP Vs FP ? @GopalAkshintala
8. @GopalAkshintala Immutability Referential Transparency Side-effects @ Boundaries FP Principles ………………………………………………… ………………………………………………… OOP Principles
9. Imperative Vs Declarative The Jotlin Dev @GopalAkshintala
10. Imperative Code - - - Imperative @GopalAkshintala
11. Let’s Concatenate last names in a team with a delimiter lastName1 lastName2 lastName2 @GopalAkshintala Team Building!
12. @GopalAkshintala What about Corner cases?
13. @GopalAkshintala lastName1 lastName2 lastName2
14. @GopalAkshintala
15. @GopalAkshintala Imperative Declarative
16. @GopalAkshintala Imperative Declarative
17. @GopalAkshintala Imperative Declarative
18. @GopalAkshintala Imperative Declarative
19. @GopalAkshintala Imperative Declarative
20. Declarative Imperative Code - - - Imperative Vs Declarative @GopalAkshintala
21. The Java @GopalAkshintala
22. But is FP just about Style?
23. How to Concatenate Last names in Parallel? @GopalAkshintala
24. @GopalAkshintala How to make this Parallel?
25. How-to-dos What-to-dos Looping through the list Aggregating the results Validating the names Extracting last names @GopalAkshintala
26. @GopalAkshintala Serial Parallel
27. The Context:Core Philosophy Do Things differently without doing Different things! @GopalAkshintala
28. Sequence Busted @GopalAkshintala
29. @GopalAkshintala Reading about Functors, Monads, Applicatives!
30. Either Monad Egg Validation Failure Context @GopalAkshintala Left Right
31. Source @GopalAkshintala
32. Source @GopalAkshintala
33. Source @GopalAkshintala Left State Stays Left
34. Source @GopalAkshintala f(g(h(x)))
35. Are Monads used in Enterprise Software? @GopalAkshintala
36. The Vader @GopalAkshintala
37. REST APIs @GopalAkshintala
38. REST Payload @GopalAkshintala
39. @GopalAkshintala
40. The Batch Validation Framework @GopalAkshintala
41. @GopalAkshintala
42. Framework Requirements @GopalAkshintala
43. @GopalAkshintala Validation layer Service layer DB layer Aggregated Response
44. Framework Meta Requirements @GopalAkshintala
45. @GopalAkshintala
46. One Egg One Validation Many Eggs One Validation @GopalAkshintala
47. Many Eggs Many Validations ! @GopalAkshintala
48. Chaos @GopalAkshintala
49. Chain of Responsibility @GopalAkshintala Is FP the Best Fit?
50. @GopalAkshintala 2D Problem Eggs Validations
51. Making of a Extensible Machine @GopalAkshintala Validations Configuration Orchestration (What-to-do) (How-to-do) (How-to-do)
52. Immutable Eggs @GopalAkshintala
53. Heterogeneous DataTypes in pipeline @GopalAkshintala
54. Uniform DataTypes with Monad Boxes @GopalAkshintala
55. Standardize Validations @GopalAkshintala
56. @GopalAkshintala val validate1Simple: Validator<Egg, ValidationFailure> = { if (simpleRule(it)) true.right() else NO_EGG_TO_VALIDATE_1.left() } validate1Simple fun validate1( badEggFailureBucketMap: MutableMap<Int, ValidationFailure>, eggIndex: Int, iterator: MutableIterator<Egg?>, eggToBeValidated: Egg? ): Boolean { if (!simpleRule(eggToBeValidated)) { iterator.remove() badEggFailureBucketMap[eggIndex] = ValidationFailures.NO_EGG_TO_VALIDATE_1 return false } return true }
57. @GopalAkshintala Validator typealias Validator<ValidatableT, FailureT> = suspend (ValidatableT) -> Either<FailureT, Any?>
58. Framework How-to-dos @GopalAkshintala
59. @GopalAkshintala Lift
60. @GopalAkshintala Lift
61. Framework How-to-dos @GopalAkshintala
62. Transformation map flatMap filter take… Aggregation reduce groupBy zip,unzip fold,foldRight scan,runningReduce @GopalAkshintala Dozen FP Operations for Daily Programming
63. Framework How-to-dos @GopalAkshintala
64. What about Complexity? @GopalAkshintala
65. FP is NOT Complex It fights Cognitive-Complexity @GopalAkshintala
66. Min. Cognitive-Complexity Same Time-Complexity @GopalAkshintala
67. Railway-Oriented Programming @GopalAkshintala
68. @GopalAkshintala bit.ly/imp-vs-dec bit.ly/ro-validation-kt bit.ly/fcwfp-kt-slides { }
69. @GopalAkshintala
70. @GopalAkshintala gopal.akshintala@gmail.com
71. @GopalAkshintala