Add helper function to format ingredient amounts

pkg/db/ingredient.go

@@ -2,6 +2,8 @@ package db
 
 import (
 	"fmt"
+	"math"
+	"strings"
 )
 
 type IngredientID uint64
@@ -83,3 +85,30 @@ func (db *DB) DeleteIngredient(i Ingredient) {
 		panic(fmt.Errorf("tried to delete ingredient with ID (%d) but it doesn't exist", i.ID))
 	}
 }
+
+func (i Ingredient) DisplayAmount() string {
+	var f float32
+	switch i.Units {
+	case COUNT:
+		f = i.Quantity
+	case GRAMS:
+		f = i.Quantity * i.Food.Mass
+	case LBS:
+		f = i.Quantity * i.Food.Mass / 454
+	case OZ:
+		f = i.Quantity * i.Food.Mass / 28
+	case ML:
+		f = i.Quantity * i.Food.Mass / i.Food.Density
+	case CUPS:
+		f = i.Quantity * i.Food.Mass / i.Food.Density / 250
+	case TSP:
+		f = i.Quantity * i.Food.Mass / i.Food.Density / 5
+	case TBSP:
+		f = i.Quantity * i.Food.Mass / i.Food.Density / 15
+	case FLOZ:
+		f = i.Quantity * i.Food.Mass / i.Food.Density / 30
+	default:
+		panic(i)
+	}
+	return strings.TrimSpace(fmt.Sprintf("%d %s", int(math.Round(float64(f))), i.Units.Abbreviation()))
+}

pkg/db/ingredient_test.go

@@ -68,3 +68,24 @@ func TestSaveAndLoadIngredient(t *testing.T) {
 	assert.NoError(err)
 	require.Len(new_recipe.Ingredients, 0)
 }
+
+func TestDisplayAmount(t *testing.T) {
+	assert := assert.New(t)
+	db := get_test_db()
+	onion := get_food(db, 28)
+
+	test_cases := []struct {
+		Ingredient
+		Expected string
+	}{
+		{Ingredient{Quantity: 1, Units: COUNT, Food: onion}, "1"},
+		{Ingredient{Quantity: 2, Units: COUNT, Food: onion}, "2"},
+		{Ingredient{Quantity: 1.818, Units: GRAMS, Food: onion}, "400 g"},
+		{Ingredient{Quantity: 9, Units: LBS, Food: onion}, "4 lbs"},
+		{Ingredient{Quantity: 2, Units: ML, Food: onion}, "440 mL"},
+	}
+
+	for _, tc := range test_cases {
+		assert.Equal(tc.Ingredient.DisplayAmount(), tc.Expected)
+	}
+}

pkg/db/units.go

@@ -3,7 +3,7 @@ package db
 type Units uint64
 
 const (
-	COUNT = Units(iota + 1)
+	COUNT = Units(iota + 1) // Start at 1 to match SQLite ID column
 	GRAMS
 	LBS
 	OZ
@@ -15,7 +15,7 @@ const (
 )
 
 var names = []string{"", "count", "grams", "pounds", "ounces", "milliliters", "cups", "teaspoons", "tablespoons", "fluid ounces"}
-var abbreviations = []string{"", "ct", "g", "lbs", "oz", "mL", "cups", "tsp", "tbsp", "fl-oz"}
+var abbreviations = []string{"", "", "g", "lbs", "oz", "mL", "cups", "tsp", "tbsp", "fl-oz"}
 
 func (u Units) Name() string {
 	return names[u]