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
   

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2. FP is cool , coz
   it’s complex enough to
   make devs feel like
   they are doing
   something smart!
   @GopalAkshintala
   - Some Manager (Not Mine!)
   

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3. @GopalAkshintala
   

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4. Dev
   Holy
   Wars
   @GopalAkshintala
   

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5. IDE Theme
   Light
   Vs
   Dark
   @GopalAkshintala
   

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6. Eclipse
   Vs
   Intellij
   @GopalAkshintala
   

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7. OOP Vs FP ?
   @GopalAkshintala
   

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8. @GopalAkshintala
   Immutability
   Referential Transparency
   Side-effects @ Boundaries
   FP Principles
   …………………………………………………
   …………………………………………………
   OOP Principles
   

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9. Imperative
   Vs
   Declarative
   The Jotlin
   Dev
   @GopalAkshintala
   

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10. Imperative
    Code
    -
    -
    -
    Imperative
    @GopalAkshintala
    

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11. Let’s Concatenate
    last names in a
    team with a
    delimiter
    lastName1 lastName2 lastName2
    @GopalAkshintala
    Team Building!
    

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12. @GopalAkshintala
    What about
    Corner cases?
    

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13. @GopalAkshintala
    lastName1 lastName2 lastName2
    
    

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14. @GopalAkshintala
    

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15. @GopalAkshintala
    Imperative Declarative
    

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16. @GopalAkshintala
    Imperative Declarative
    

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17. @GopalAkshintala
    Imperative Declarative
    

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18. @GopalAkshintala
    Imperative Declarative
    

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19. @GopalAkshintala
    Imperative Declarative
    

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20. Declarative
    Imperative
    Code
    -
    -
    -
    Imperative
    Vs
    Declarative
    @GopalAkshintala
    

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21. The Java
    @GopalAkshintala
    

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22. But is FP just about
    Style?
    

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23. How to Concatenate
    Last names in
    Parallel?
    @GopalAkshintala
    

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24. @GopalAkshintala
    How to make this Parallel?
    

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25. How-to-dos What-to-dos
    Looping through
    the list
    Aggregating the
    results
    Validating the
    names
    Extracting last
    names
    @GopalAkshintala
    

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26. @GopalAkshintala
    Serial Parallel
    

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27. The
    Context:Core
    Philosophy
    Do
    Things differently
    without
    doing
    Different things!
    @GopalAkshintala
    

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28. Sequence
    Busted
    @GopalAkshintala
    

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29. @GopalAkshintala
    Reading about
    Functors, Monads, Applicatives!
    

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30. Either Monad
    Egg
    Validation Failure
    Context
    @GopalAkshintala
    Left Right
    

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31. Source @GopalAkshintala
    

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32. Source @GopalAkshintala
    

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33. Source @GopalAkshintala
    Left State
    Stays Left
    

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34. Source @GopalAkshintala
    f(g(h(x)))
    

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35. Are Monads used in
    Enterprise
    Software?
    @GopalAkshintala
    

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36. The
    Vader
    @GopalAkshintala
    

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37. REST
    APIs
    @GopalAkshintala
    

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38. REST
    Payload
    @GopalAkshintala
    

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39. @GopalAkshintala
    

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40. The
    Batch
    Validation
    Framework
    @GopalAkshintala
    

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41. @GopalAkshintala
    

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42. Framework
    Requirements
    @GopalAkshintala
    

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43. @GopalAkshintala
    Validation layer
    Service layer
    DB layer
    Aggregated Response
    

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44. Framework
    Meta
    Requirements
    @GopalAkshintala
    

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45. @GopalAkshintala
    

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46. One Egg
    One Validation
    Many Eggs
    One Validation
    @GopalAkshintala
    

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47. Many Eggs
    Many Validations
    !
    @GopalAkshintala
    

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48. Chaos
    @GopalAkshintala
    

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49. Chain of Responsibility
    @GopalAkshintala
    Is FP the Best Fit?
    

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50. @GopalAkshintala
    2D Problem
    Eggs
    Validations
    

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51. Making of a
    Extensible Machine
    @GopalAkshintala
    Validations Configuration Orchestration
    (What-to-do) (How-to-do) (How-to-do)
    

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52. Immutable
    Eggs
    @GopalAkshintala
    

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53. Heterogeneous
    DataTypes in pipeline
    @GopalAkshintala
    

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54. Uniform DataTypes
    with Monad Boxes
    @GopalAkshintala
    

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55. Standardize
    Validations
    @GopalAkshintala
    

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56. @GopalAkshintala
    val validate1Simple: Validator = {
    if (simpleRule(it)) true.right() else NO_EGG_TO_VALIDATE_1.left()
    }
    validate1Simple
    fun validate1(
    badEggFailureBucketMap: MutableMap,
    eggIndex: Int,
    iterator: MutableIterator,
    eggToBeValidated: Egg?
    ): Boolean {
    if (!simpleRule(eggToBeValidated)) {
    iterator.remove()
    badEggFailureBucketMap[eggIndex] = ValidationFailures.NO_EGG_TO_VALIDATE_1
    return false
    }
    return true
    }
    

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57. @GopalAkshintala
    Validator
    typealias Validator
    = suspend (ValidatableT) -> Either
    

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58. Framework
    How-to-dos
    @GopalAkshintala
    

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59. @GopalAkshintala
    Lift
    

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60. @GopalAkshintala
    Lift
    

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61. Framework
    How-to-dos
    @GopalAkshintala
    

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62. Transformation
    map
    flatMap
    filter
    take…
    Aggregation
    reduce
    groupBy
    zip,unzip
    fold,foldRight
    scan,runningReduce
    @GopalAkshintala
    Dozen FP Operations for
    Daily Programming
    

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63. Framework
    How-to-dos
    @GopalAkshintala
    

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64. What about
    Complexity?
    @GopalAkshintala
    

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65. FP is NOT Complex
    It fights
    Cognitive-Complexity
    @GopalAkshintala
    

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66. Min.
    Cognitive-Complexity
    Same
    Time-Complexity
    @GopalAkshintala
    

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67. Railway-Oriented
    Programming
    @GopalAkshintala
    

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68. @GopalAkshintala
    bit.ly/imp-vs-dec
    bit.ly/ro-validation-kt
    bit.ly/fcwfp-kt-slides
    { }
    

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69. @GopalAkshintala
    

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70. @GopalAkshintala
    gopal.akshintala@gmail.com
    

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71. @GopalAkshintala
    

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