Merge pull request #49 from cycloidio/vs-cost-currency

cost: include currency in cost calculations
cycloidio · Jul 13, 2021 · 6fd5fc8 · 6fd5fc8
2 parents fcaedcb + 978fc15
commit 6fd5fc8
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,9 @@
 ## [Unreleased]
 
+### Added
+
+- Include currency in resource component cost estimation
+  ([Issue #48](https://github.com/cycloidio/terracost/issues/48))
 
 ## [0.3.0] _2021-06-01_
 

diff --git a/README.md b/README.md
@@ -43,7 +43,7 @@ backend := mysql.NewBackend(db)
 
 // service can be "AmazonEC2" or "AmazonRDS"
 // region is any AWS region, e.g. "us-east-1" or "eu-west-3"
-ingester := aws.NewIngester(service, region)
+ingester, err := aws.NewIngester(service, region)
 err = terracost.IngestPricing(ctx, backend, ingester)
 ```
 
@@ -67,7 +67,7 @@ go func() {
 2. Initialize an ingester capable of tracking progress (in this example the channel will receive an update every 5 seconds):
 
 ```go
-ingester := aws.NewIngester(service, region, aws.WithProgress(progressCh, 5*time.Second))
+ingester, err := aws.NewIngester(service, region, aws.WithProgress(progressCh, 5*time.Second))
 ```
 
 3. Use the ingester as in the previous section.

diff --git a/cost/component_test.go b/cost/component_test.go
@@ -18,7 +18,7 @@ func TestComponentDiff_PriorCost(t *testing.T) {
 	})
 
 	t.Run("WithValue", func(t *testing.T) {
-		cd := cost.ComponentDiff{Prior: &cost.Component{Quantity: decimal.NewFromInt(5), Rate: cost.NewMonthly(decimal.NewFromFloat(1.5))}}
+		cd := cost.ComponentDiff{Prior: &cost.Component{Quantity: decimal.NewFromInt(5), Rate: cost.NewMonthly(decimal.NewFromFloat(1.5), "USD")}}
 		actual := cd.PriorCost()
 		assert.True(t, actual.Equal(decimal.NewFromFloat(7.5)))
 	})
@@ -32,7 +32,7 @@ func TestComponentDiff_PlannedCost(t *testing.T) {
 	})
 
 	t.Run("WithValue", func(t *testing.T) {
-		cd := cost.ComponentDiff{Planned: &cost.Component{Quantity: decimal.NewFromInt(5), Rate: cost.NewMonthly(decimal.NewFromFloat(1.5))}}
+		cd := cost.ComponentDiff{Planned: &cost.Component{Quantity: decimal.NewFromInt(5), Rate: cost.NewMonthly(decimal.NewFromFloat(1.5), "USD")}}
 		actual := cd.PlannedCost()
 		assert.True(t, actual.Equal(decimal.NewFromFloat(7.5)))
 	})

diff --git a/cost/cost.go b/cost/cost.go
@@ -1,6 +1,8 @@
 package cost
 
 import (
+	"fmt"
+
 	"github.com/shopspring/decimal"
 )
 
@@ -12,19 +14,21 @@ var HoursPerMonth = decimal.NewFromInt(730)
 type Cost struct {
 	// Decimal is price per month.
 	decimal.Decimal
+	// Currency of the cost.
+	Currency string
 }
 
 // Zero is Cost with zero value.
 var Zero = Cost{}
 
-// NewMonthly returns a new Cost from price per month.
-func NewMonthly(monthly decimal.Decimal) Cost {
-	return Cost{Decimal: monthly}
+// NewMonthly returns a new Cost from price per month with currency.
+func NewMonthly(monthly decimal.Decimal, currency string) Cost {
+	return Cost{Decimal: monthly, Currency: currency}
 }
 
-// NewHourly returns a new Cost from price per hour.
-func NewHourly(hourly decimal.Decimal) Cost {
-	return Cost{Decimal: hourly.Mul(HoursPerMonth)}
+// NewHourly returns a new Cost from price per hour with currency.
+func NewHourly(hourly decimal.Decimal, currency string) Cost {
+	return Cost{Decimal: hourly.Mul(HoursPerMonth), Currency: currency}
 }
 
 // Monthly returns the cost per month.
@@ -38,11 +42,21 @@ func (c Cost) Hourly() decimal.Decimal {
 }
 
 // Add adds the values of two Cost structs.
-func (c Cost) Add(c2 Cost) Cost {
-	return Cost{Decimal: c.Decimal.Add(c2.Monthly())}
+// If the currency of both costs doesn't match, error is returned.
+func (c Cost) Add(c2 Cost) (Cost, error) {
+	// If there is no currency, use the currency of the addition
+	if c.Currency == "" {
+		c.Currency = c2.Currency
+	}
+
+	if c.Currency != c2.Currency {
+		return Zero, fmt.Errorf("currency mismatch: expected %s, got %s", c.Currency, c2.Currency)
+	}
+
+	return Cost{Decimal: c.Decimal.Add(c2.Monthly()), Currency: c.Currency}, nil
 }
 
 // MulDecimal multiplies the Cost by the given decimal.Decimal.
 func (c Cost) MulDecimal(d decimal.Decimal) Cost {
-	return Cost{Decimal: c.Decimal.Mul(d)}
+	return Cost{Decimal: c.Decimal.Mul(d), Currency: c.Currency}
 }
diff --git a/cost/cost_test.go b/cost/cost_test.go
@@ -10,36 +10,46 @@ import (
 
 func TestNewHourly(t *testing.T) {
 	val := decimal.NewFromFloat(1.23)
-	c := cost.NewHourly(val)
+	c := cost.NewHourly(val, "USD")
 	assertDecimalEqual(t, val.Mul(cost.HoursPerMonth), c.Decimal)
 }
 
 func TestNewMonthly(t *testing.T) {
 	val := decimal.NewFromFloat(1.23)
-	c := cost.NewMonthly(val)
+	c := cost.NewMonthly(val, "USD")
 	assertDecimalEqual(t, val, c.Decimal)
 }
 
 func TestCost_Hourly(t *testing.T) {
 	val := decimal.NewFromFloat(1.23)
-	c := cost.NewMonthly(val.Mul(cost.HoursPerMonth))
+	c := cost.NewMonthly(val.Mul(cost.HoursPerMonth), "USD")
 	assertDecimalEqual(t, val, c.Hourly())
 }
 
 func TestCost_Monthly(t *testing.T) {
 	val := decimal.NewFromFloat(1.23)
-	c := cost.NewHourly(val)
+	c := cost.NewHourly(val, "USD")
 	assertDecimalEqual(t, val.Mul(cost.HoursPerMonth), c.Monthly())
 }
 
 func TestCost_Add(t *testing.T) {
-	c1 := cost.NewMonthly(decimal.NewFromFloat(1.23))
-	c2 := cost.NewMonthly(decimal.NewFromFloat(3.21))
-	assertDecimalEqual(t, decimal.NewFromFloat(4.44), c1.Add(c2).Decimal)
+	t.Run("Success", func(t *testing.T) {
+		c1 := cost.NewMonthly(decimal.NewFromFloat(1.23), "USD")
+		c2 := cost.NewMonthly(decimal.NewFromFloat(3.21), "USD")
+		ac, err := c1.Add(c2)
+		assert.NoError(t, err)
+		assertDecimalEqual(t, decimal.NewFromFloat(4.44), ac.Decimal)
+	})
+	t.Run("CurrencyMismatch", func(t *testing.T) {
+		c1 := cost.NewMonthly(decimal.NewFromFloat(1.23), "USD")
+		c2 := cost.NewMonthly(decimal.NewFromFloat(3.21), "EUR")
+		_, err := c1.Add(c2)
+		assert.EqualError(t, err, "currency mismatch: expected USD, got EUR")
+	})
 }
 
 func TestCost_MulDecimal(t *testing.T) {
-	c := cost.NewMonthly(decimal.NewFromFloat(1.23))
+	c := cost.NewMonthly(decimal.NewFromFloat(1.23), "USD")
 	d := decimal.NewFromInt(3)
 	assertDecimalEqual(t, decimal.NewFromFloat(3.69), c.MulDecimal(d).Decimal)
 }

diff --git a/cost/plan.go b/cost/plan.go
@@ -18,17 +18,17 @@ func NewPlan(prior, planned *State) *Plan {
 }
 
 // PriorCost returns the total cost of the Prior State or decimal.Zero if it isn't included in the plan.
-func (p Plan) PriorCost() Cost {
+func (p Plan) PriorCost() (Cost, error) {
 	if p.Prior == nil {
-		return Zero
+		return Zero, nil
 	}
 	return p.Prior.Cost()
 }
 
 // PlannedCost returns the total cost of the Planned State or decimal.Zero if it isn't included in the plan.
-func (p Plan) PlannedCost() Cost {
+func (p Plan) PlannedCost() (Cost, error) {
 	if p.Planned == nil {
-		return Zero
+		return Zero, nil
 	}
 	return p.Planned.Cost()
 }

diff --git a/cost/plan_test.go b/cost/plan_test.go
@@ -19,7 +19,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23), "USD"),
 						},
 					},
 				},
@@ -36,7 +36,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 					Prior: &cost.Component{
 						Quantity: decimal.NewFromInt(730),
 						Unit:     "Hrs",
-						Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23)),
+						Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23), "USD"),
 					},
 				},
 			},
@@ -51,7 +51,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23), "USD"),
 						},
 					},
 				},
@@ -68,7 +68,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 					Planned: &cost.Component{
 						Quantity: decimal.NewFromInt(730),
 						Unit:     "Hrs",
-						Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23)),
+						Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23), "USD"),
 					},
 				},
 			},
@@ -83,7 +83,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(1.50)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(1.50), "USD"),
 						},
 					},
 				},
@@ -92,7 +92,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23), "USD"),
 						},
 					},
 				},
@@ -105,7 +105,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50), "USD"),
 						},
 					},
 				},
@@ -114,7 +114,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(3.21)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(3.21), "USD"),
 						},
 					},
 				},
@@ -131,12 +131,12 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 					Prior: &cost.Component{
 						Quantity: decimal.NewFromInt(730),
 						Unit:     "Hrs",
-						Rate:     cost.NewMonthly(decimal.NewFromFloat(1.50)),
+						Rate:     cost.NewMonthly(decimal.NewFromFloat(1.50), "USD"),
 					},
 					Planned: &cost.Component{
 						Quantity: decimal.NewFromInt(730),
 						Unit:     "Hrs",
-						Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50)),
+						Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50), "USD"),
 					},
 				},
 			},
@@ -148,7 +148,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 					Planned: &cost.Component{
 						Quantity: decimal.NewFromInt(730),
 						Unit:     "Hrs",
-						Rate:     cost.NewMonthly(decimal.NewFromFloat(3.21)),
+						Rate:     cost.NewMonthly(decimal.NewFromFloat(3.21), "USD"),
 					},
 				},
 			},
@@ -160,7 +160,7 @@ func TestPlan_ResourceDifferences(t *testing.T) {
 					Prior: &cost.Component{
 						Quantity: decimal.NewFromInt(730),
 						Unit:     "Hrs",
-						Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23)),
+						Rate:     cost.NewMonthly(decimal.NewFromFloat(1.23), "USD"),
 					},
 				},
 			},
@@ -177,7 +177,7 @@ func TestPlan_SkippedAddresses(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50), "USD"),
 						},
 					},
 				},
@@ -200,7 +200,7 @@ func TestPlan_SkippedAddresses(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50), "USD"),
 						},
 					},
 				},
@@ -223,7 +223,7 @@ func TestPlan_SkippedAddresses(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50), "USD"),
 						},
 					},
 				},
@@ -238,7 +238,7 @@ func TestPlan_SkippedAddresses(t *testing.T) {
 						"EC2 instance hours": {
 							Quantity: decimal.NewFromInt(730),
 							Unit:     "Hrs",
-							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50)),
+							Rate:     cost.NewMonthly(decimal.NewFromFloat(2.50), "USD"),
 						},
 					},
 				},

diff --git a/cost/resource.go b/cost/resource.go
@@ -1,5 +1,7 @@
 package cost
 
+import "fmt"
+
 // Resource represents costs of a single cloud resource. Each Resource includes a Component map, keyed
 // by the label.
 type Resource struct {
@@ -10,12 +12,17 @@ type Resource struct {
 }
 
 // Cost returns the sum of costs of every Component of this Resource.
-func (re Resource) Cost() Cost {
+// Error is returned if there is a mismatch in Component currency.
+func (re Resource) Cost() (Cost, error) {
 	var total Cost
-	for _, comp := range re.Components {
-		total = total.Add(comp.Cost())
+	var err error
+	for name, comp := range re.Components {
+		total, err = total.Add(comp.Cost())
+		if err != nil {
+			return Zero, fmt.Errorf("failed to add cost of component %s: %w", name, err)
+		}
 	}
-	return total
+	return total, nil
 }
 
 // ResourceDiff is the difference in costs between prior and planned Resource. It contains a ComponentDiff
@@ -28,21 +35,31 @@ type ResourceDiff struct {
 }
 
 // PriorCost returns the sum of costs of every Component's PriorCost.
-func (rd ResourceDiff) PriorCost() Cost {
+// Error is returned if there is a mismatch between currencies of the Components.
+func (rd ResourceDiff) PriorCost() (Cost, error) {
 	total := Zero
+	var err error
 	for _, cd := range rd.ComponentDiffs {
-		total = total.Add(cd.PriorCost())
+		total, err = total.Add(cd.PriorCost())
+		if err != nil {
+			return Zero, fmt.Errorf("failed calculating prior cost : %w", err)
+		}
 	}
-	return total
+	return total, nil
 }
 
 // PlannedCost returns the sum of costs of every Component's PlannedCost.
-func (rd ResourceDiff) PlannedCost() Cost {
+// Error is returned if there is a mismatch between currencies of the Components.
+func (rd ResourceDiff) PlannedCost() (Cost, error) {
 	total := Zero
+	var err error
 	for _, cd := range rd.ComponentDiffs {
-		total = total.Add(cd.PlannedCost())
+		total, err = total.Add(cd.PriorCost())
+		if err != nil {
+			return Zero, fmt.Errorf("failed calculating planned cost: %w", err)
+		}
 	}
-	return total
+	return total, nil
 }
 
 // Errors returns a map of Component errors keyed by the Component label.