|
| 1 | +package eval |
| 2 | + |
| 3 | +import ( |
| 4 | + "errors" |
| 5 | + "fmt" |
| 6 | + "math" |
| 7 | + |
| 8 | + "github.com/diegoholiveira/jsonlogic/v3" |
| 9 | + log "github.com/sirupsen/logrus" |
| 10 | + "github.com/spaolacci/murmur3" |
| 11 | +) |
| 12 | + |
| 13 | +func init() { |
| 14 | + jsonlogic.AddOperator("fractionalEvaluation", fractionalEvaluation) |
| 15 | +} |
| 16 | + |
| 17 | +type fractionalEvaluationDistribution struct { |
| 18 | + variant string |
| 19 | + percentage int |
| 20 | +} |
| 21 | + |
| 22 | +func fractionalEvaluation(values, data interface{}) interface{} { |
| 23 | + valueToDistribute, feDistributions, err := parseFractionalEvaluationData(values, data) |
| 24 | + if err != nil { |
| 25 | + log.Errorf("parseFractionalEvaluationData: %v", err) |
| 26 | + return nil |
| 27 | + } |
| 28 | + |
| 29 | + return distributeValue(valueToDistribute, feDistributions) |
| 30 | +} |
| 31 | + |
| 32 | +func parseFractionalEvaluationData(values, data interface{}) (string, []fractionalEvaluationDistribution, error) { |
| 33 | + valuesArray, ok := values.([]interface{}) |
| 34 | + if !ok { |
| 35 | + return "", nil, errors.New("fractional evaluation data is not an array") |
| 36 | + } |
| 37 | + if len(valuesArray) < 2 { |
| 38 | + return "", nil, errors.New("fractional evaluation data has length under 2") |
| 39 | + } |
| 40 | + |
| 41 | + bucketBy, ok := valuesArray[0].(string) |
| 42 | + if !ok { |
| 43 | + return "", nil, errors.New("first element of fractional evaluation data isn't of type string") |
| 44 | + } |
| 45 | + |
| 46 | + dataMap, ok := data.(map[string]interface{}) |
| 47 | + if !ok { |
| 48 | + return "", nil, errors.New("data isn't of type map[string]interface{}") |
| 49 | + } |
| 50 | + |
| 51 | + v, ok := dataMap[bucketBy] |
| 52 | + if !ok { |
| 53 | + return "", nil, fmt.Errorf("%s isn't a found var in data", bucketBy) |
| 54 | + } |
| 55 | + |
| 56 | + valueToDistribute, ok := v.(string) |
| 57 | + if !ok { |
| 58 | + return "", nil, fmt.Errorf("var %s isn't of type string", bucketBy) |
| 59 | + } |
| 60 | + |
| 61 | + feDistributions, err := parseFractionalEvaluationDistributions(valuesArray) |
| 62 | + if err != nil { |
| 63 | + return "", nil, err |
| 64 | + } |
| 65 | + |
| 66 | + return valueToDistribute, feDistributions, nil |
| 67 | +} |
| 68 | + |
| 69 | +func parseFractionalEvaluationDistributions(values []interface{}) ([]fractionalEvaluationDistribution, error) { |
| 70 | + sumOfPercentages := 0 |
| 71 | + var feDistributions []fractionalEvaluationDistribution |
| 72 | + for i := 1; i < len(values); i++ { |
| 73 | + distributionArray, ok := values[i].([]interface{}) |
| 74 | + if !ok { |
| 75 | + return nil, errors.New("distribution elements aren't of type []interface{}") |
| 76 | + } |
| 77 | + |
| 78 | + if len(distributionArray) != 2 { |
| 79 | + return nil, errors.New("distribution element isn't length 2") |
| 80 | + } |
| 81 | + |
| 82 | + variant, ok := distributionArray[0].(string) |
| 83 | + if !ok { |
| 84 | + return nil, errors.New("first element of distribution element isn't string") |
| 85 | + } |
| 86 | + |
| 87 | + percentage, ok := distributionArray[1].(float64) |
| 88 | + if !ok { |
| 89 | + return nil, errors.New("second element of distribution element isn't float") |
| 90 | + } |
| 91 | + |
| 92 | + sumOfPercentages += int(percentage) |
| 93 | + |
| 94 | + feDistributions = append(feDistributions, fractionalEvaluationDistribution{ |
| 95 | + variant: variant, |
| 96 | + percentage: int(percentage), |
| 97 | + }) |
| 98 | + } |
| 99 | + |
| 100 | + if sumOfPercentages != 100 { |
| 101 | + return nil, fmt.Errorf("percentages must sum to 100, got %d", sumOfPercentages) |
| 102 | + } |
| 103 | + |
| 104 | + return feDistributions, nil |
| 105 | +} |
| 106 | + |
| 107 | +func distributeValue(value string, feDistribution []fractionalEvaluationDistribution) string { |
| 108 | + hashValue := murmur3.Sum64([]byte(value)) |
| 109 | + |
| 110 | + hashRatio := float64(hashValue) / math.Pow(2, 64) // divide the hash value by the largest possible value, integer 2^64 |
| 111 | + |
| 112 | + bucket := int(hashRatio * 100) // integer in range [0, 99] |
| 113 | + |
| 114 | + rangeEnd := 0 |
| 115 | + for _, dist := range feDistribution { |
| 116 | + rangeEnd += dist.percentage |
| 117 | + if bucket < rangeEnd { |
| 118 | + return dist.variant |
| 119 | + } |
| 120 | + } |
| 121 | + |
| 122 | + return "" |
| 123 | +} |
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