Initial commit

server/internal/domain/eta.go

@@ -0,0 +1,48 @@
+package domain
+
+import (
+	"errors"
+	"math"
+	"time"
+)
+
+type ETAInput struct {
+	PeopleAhead       int
+	IntervalPerNumber time.Duration
+	Running           bool
+}
+
+type ETAResult struct {
+	Available       bool   `json:"available"`
+	EstimateMinutes int    `json:"estimate_minutes,omitempty"`
+	MinMinutes      int    `json:"min_minutes,omitempty"`
+	MaxMinutes      int    `json:"max_minutes,omitempty"`
+	Reason          string `json:"reason,omitempty"`
+}
+
+func CalculateETA(input ETAInput) (ETAResult, error) {
+	if !input.Running {
+		return ETAResult{Available: false, Reason: "queue_not_running"}, nil
+	}
+	if input.PeopleAhead < 0 {
+		return ETAResult{}, errors.New("people ahead cannot be negative")
+	}
+	if input.IntervalPerNumber <= 0 {
+		return ETAResult{Available: false, Reason: "missing_interval_configuration"}, nil
+	}
+	rawMinutes := float64(input.PeopleAhead+1) * input.IntervalPerNumber.Minutes()
+	estimate := roundUpFive(rawMinutes)
+	return ETAResult{
+		Available:       true,
+		EstimateMinutes: estimate,
+		MinMinutes:      estimate,
+		MaxMinutes:      estimate,
+	}, nil
+}
+
+func roundUpFive(value float64) int {
+	if value <= 0 {
+		return 0
+	}
+	return int(math.Ceil(value/5) * 5)
+}