feat(event): add guardrail evaluation

go.mod

@@ -4,7 +4,7 @@ go 1.25.2
 
 require (
 	github.com/hashicorp/hcl/v2 v2.24.0
-	github.com/infracost/proto v1.19.0
+	github.com/infracost/proto v1.23.0
 	github.com/stretchr/testify v1.11.1
 	github.com/zclconf/go-cty v1.17.0
 )

go.sum

@@ -22,11 +22,8 @@ github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/hashicorp/hcl/v2 v2.24.0 h1:2QJdZ454DSsYGoaE6QheQZjtKZSUs9Nh2izTWiwQxvE=
 github.com/hashicorp/hcl/v2 v2.24.0/go.mod h1:oGoO1FIQYfn/AgyOhlg9qLC6/nOJPX3qGbkZpYAcqfM=
-github.com/infracost/proto v1.17.0 h1:9OBYvA+/gfVDOzi0go4gTY2pOnTgqvov1OnwRBMDopA=
-github.com/infracost/proto v1.17.0/go.mod h1:BO6ew0skDYqM8lxl3rKKMA7WRM7VG1dIUKErbTdfGPk=
-github.com/infracost/proto v1.17.1-0.20260225103127-e390beafddfe/go.mod h1:BO6ew0skDYqM8lxl3rKKMA7WRM7VG1dIUKErbTdfGPk=
-github.com/infracost/proto v1.19.0 h1:vLeQnM53e5A/+4zpU3d+ZXf55mPJLKzJUqLFMT9W5D8=
-github.com/infracost/proto v1.19.0/go.mod h1:BO6ew0skDYqM8lxl3rKKMA7WRM7VG1dIUKErbTdfGPk=
+github.com/infracost/proto v1.23.0 h1:zbjCxNdA+YKZlXzvVVN3drfJpDLFdLnctuDpDtmQ7r8=
+github.com/infracost/proto v1.23.0/go.mod h1:BO6ew0skDYqM8lxl3rKKMA7WRM7VG1dIUKErbTdfGPk=
 github.com/mitchellh/go-wordwrap v1.0.1 h1:TLuKupo69TCn6TQSyGxwI1EblZZEsQ0vMlAFQflz0v0=
 github.com/mitchellh/go-wordwrap v1.0.1/go.mod h1:R62XHJLzvMFRBbcrT7m7WgmE1eOyTSsCt+hzestvNj0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=

pkg/event/guardrails.go

@@ -0,0 +1,160 @@
+package event
+
+import (
+	"github.com/infracost/go-proto/pkg/rat"
+	"github.com/infracost/proto/gen/go/infracost/parser/event"
+)
+
+// GuardrailResult is the result of evaluating a single applicable guardrail.
+// It is serialized as JSON and sent back to the dashboard API via the addRun
+// GraphQL mutation. Every applicable guardrail produces a result, whether or
+// not it triggered.
+type GuardrailResult struct {
+	GuardrailID            string   `json:"guardrailId"`
+	Triggered              bool     `json:"triggered"`
+	PRComment              bool     `json:"prComment"`
+	BlockPR                bool     `json:"blockPr"`
+	TriggeringProjectNames []string `json:"triggeringProjectNames"`
+	Increase               *rat.Rat `json:"increase"`
+	PercentIncrease        *rat.Rat `json:"percentIncrease"`
+	TotalMonthlyCost       *rat.Rat `json:"totalMonthlyCost"`
+}
+
+// ProjectCostInfo holds the cost data for a single project, used as input
+// to guardrail evaluation.
+type ProjectCostInfo struct {
+	ProjectName          string
+	TotalMonthlyCost     *rat.Rat
+	PastTotalMonthlyCost *rat.Rat
+}
+
+// Guardrails wraps a list of guardrail proto configurations for evaluation.
+type Guardrails []*event.Guardrail
+
+// Evaluate checks guardrails against the provided run-level and project-level
+// costs and returns a result for each applicable guardrail.
+func (gs Guardrails) Evaluate(
+	totalMonthlyCost *rat.Rat,
+	pastTotalMonthlyCost *rat.Rat,
+	projects []ProjectCostInfo,
+) []GuardrailResult {
+	var results []GuardrailResult
+
+	for _, g := range gs {
+		result := GuardrailResult{
+			GuardrailID:            g.GetId(),
+			PRComment:              g.GetPrComment(),
+			BlockPR:                g.GetBlockPr(),
+			TriggeringProjectNames: []string{},
+		}
+
+		if !hasThresholds(g) {
+			results = append(results, result)
+			continue
+		}
+
+		switch g.GetScope() {
+		case event.Guardrail_REPO:
+			increase := calcIncrease(totalMonthlyCost, pastTotalMonthlyCost)
+			result.Increase = increase.increase
+			result.PercentIncrease = increase.percentIncrease
+			result.TotalMonthlyCost = totalMonthlyCost
+			result.Triggered = thresholdExceeded(g, totalMonthlyCost, pastTotalMonthlyCost)
+
+		case event.Guardrail_PROJECT:
+			projectFilter := StringFilterFromProto(g.GetProjectFilter())
+
+			var triggeringNames []string
+			var maxIncrease costIncrease
+
+			for _, p := range projects {
+				if !projectFilter.Matches(p.ProjectName) {
+					continue
+				}
+
+				inc := calcIncrease(p.TotalMonthlyCost, p.PastTotalMonthlyCost)
+				if thresholdExceeded(g, p.TotalMonthlyCost, p.PastTotalMonthlyCost) {
+					triggeringNames = append(triggeringNames, p.ProjectName)
+				}
+
+				if maxIncrease.increase == nil || inc.increase.GreaterThan(maxIncrease.increase) {
+					maxIncrease = inc
+				}
+			}
+
+			if maxIncrease.increase != nil {
+				result.Increase = maxIncrease.increase
+				result.PercentIncrease = maxIncrease.percentIncrease
+			} else {
+				result.Increase = rat.Zero
+				result.PercentIncrease = rat.Zero
+			}
+			result.TotalMonthlyCost = totalMonthlyCost
+			result.Triggered = len(triggeringNames) > 0
+			result.TriggeringProjectNames = triggeringNames
+		}
+
+		results = append(results, result)
+	}
+
+	return results
+}
+
+func hasThresholds(g *event.Guardrail) bool {
+	return g.IncreaseThreshold != nil || g.IncreasePercentThreshold != nil || g.TotalThreshold != nil
+}
+
+func thresholdExceeded(g *event.Guardrail, totalMonthlyCost, pastTotalMonthlyCost *rat.Rat) bool {
+	increase := calcIncrease(totalMonthlyCost, pastTotalMonthlyCost)
+
+	// Never trigger on cost decreases or no change.
+	if !increase.increase.GreaterThanZero() {
+		return false
+	}
+
+	// All configured thresholds must be exceeded (AND logic).
+	if g.IncreaseThreshold != nil {
+		if !increase.increase.GreaterThan(rat.FromProto(g.IncreaseThreshold)) {
+			return false
+		}
+	}
+
+	if g.IncreasePercentThreshold != nil {
+		if !increase.percentIncrease.GreaterThan(rat.FromProto(g.IncreasePercentThreshold)) {
+			return false
+		}
+	}
+
+	// Total threshold uses crossing logic: only triggers when crossing from
+	// at-or-below to above the threshold.
+	if g.TotalThreshold != nil {
+		threshold := rat.FromProto(g.TotalThreshold)
+		if !pastTotalMonthlyCost.LessThanOrEqual(threshold) || !totalMonthlyCost.GreaterThan(threshold) {
+			return false
+		}
+	}
+
+	return true
+}
+
+type costIncrease struct {
+	increase        *rat.Rat
+	percentIncrease *rat.Rat
+}
+
+func calcIncrease(totalMonthlyCost, pastTotalMonthlyCost *rat.Rat) costIncrease {
+	increase := totalMonthlyCost.Sub(pastTotalMonthlyCost)
+
+	var percentIncrease *rat.Rat
+	if pastTotalMonthlyCost.IsZero() {
+		percentIncrease = rat.Zero
+	} else {
+		// (total / past - 1) * 100, rounded to 0 decimal places
+		percentIncrease = totalMonthlyCost.Div(pastTotalMonthlyCost).Sub(rat.New(1)).Mul(rat.New(100)).Round(0)
+	}
+
+	return costIncrease{
+		increase:        increase,
+		percentIncrease: percentIncrease,
+	}
+}