Add round and suffix based value formatter for the Y-axis label representation

Signed-off-by: Xabier Larrakoetxea <slok69@gmail.com>

widgets/linechart/value_formatter.go

@@ -20,6 +20,7 @@ package linechart
 import (
 	"fmt"
 	"math"
+	"strings"
 	"time"
 )
 
@@ -42,33 +43,34 @@ func durationSingleUnitPrettyFormat(d time.Duration, decimals int) string {
 		return fmt.Sprintf(dFmt, d.Nanoseconds())
 	// Microseconds.
 	case d.Seconds()*1000*1000 < 1000:
-		dFmt := prefix + decimalFormat(decimals, "µs")
+		dFmt := prefix + suffixDecimalFormat(decimals, "µs")
 		return fmt.Sprintf(dFmt, d.Seconds()*1000*1000)
 	// Milliseconds.
 	case d.Seconds()*1000 < 1000:
-		dFmt := prefix + decimalFormat(decimals, "ms")
+		dFmt := prefix + suffixDecimalFormat(decimals, "ms")
 		return fmt.Sprintf(dFmt, d.Seconds()*1000)
 	// Seconds.
 	case d.Seconds() < 60:
-		dFmt := prefix + decimalFormat(decimals, "s")
+		dFmt := prefix + suffixDecimalFormat(decimals, "s")
 		return fmt.Sprintf(dFmt, d.Seconds())
 	// Minutes.
 	case d.Minutes() < 60:
-		dFmt := prefix + decimalFormat(decimals, "m")
+		dFmt := prefix + suffixDecimalFormat(decimals, "m")
 		return fmt.Sprintf(dFmt, d.Minutes())
 	// Hours.
 	case d.Hours() < 24:
-		dFmt := prefix + decimalFormat(decimals, "h")
+		dFmt := prefix + suffixDecimalFormat(decimals, "h")
 		return fmt.Sprintf(dFmt, d.Hours())
 	// Days.
 	default:
-		dFmt := prefix + decimalFormat(decimals, "d")
+		dFmt := prefix + suffixDecimalFormat(decimals, "d")
 		return fmt.Sprintf(dFmt, d.Hours()/24)
 	}
 }
 
-func decimalFormat(decimals int, unit string) string {
+func suffixDecimalFormat(decimals int, suffix string) string {
-	return fmt.Sprintf("%%.%df%s", decimals, unit)
+	suffix = strings.ReplaceAll(suffix, "%", "%%") // safe `%` character for fmt.
+	return fmt.Sprintf("%%.%df%s", decimals, suffix)
 }
 
 // ValueFormatterSingleUnitDuration is a factory to create a custom duration
@@ -103,3 +105,42 @@ func ValueFormatterSingleUnitSeconds(seconds float64) string {
 	f := ValueFormatterSingleUnitDuration(time.Second, 0)
 	return f(seconds)
 }
+
+// ValueFormatterRound is a formatter that will receive a float64
+// value and will round to the nearest value without decimals.
+func ValueFormatterRound(value float64) string {
+	f := ValueFormatterRoundWithSuffix("")
+	return f(value)
+}
+
+// ValueFormatterRoundWithSuffix is a factory that returns a formatter
+// that will receive a float64 value and will round to the nearest value
+// without decimals adding a suffix to the final value string representation.
+func ValueFormatterRoundWithSuffix(suffix string) ValueFormatter {
+	return valueFormatterSuffixWithTransformer(0, suffix, math.Round)
+}
+
+// ValueFormatterSuffix is a factory that returns a formatter
+// that will receive a float64 value and return a string representation with
+// the desired number of decimal truncated and a suffix.
+func ValueFormatterSuffix(decimals int, suffix string) ValueFormatter {
+	return valueFormatterSuffixWithTransformer(decimals, suffix, nil)
+}
+
+// valueFormatterSuffixWithTransformer is a factory that returns a formatter
+// that will apply a tranform function to the received value before
+// returning the decimal with suffix representation.
+func valueFormatterSuffixWithTransformer(decimals int, suffix string, transformFunc func(float64) float64) ValueFormatter {
+	dFmt := suffixDecimalFormat(decimals, suffix)
+	return func(value float64) string {
+		if math.IsNaN(value) {
+			return ""
+		}
+
+		if transformFunc != nil {
+			value = transformFunc(value)
+		}
+
+		return fmt.Sprintf(dFmt, value)
+	}
+}

widgets/linechart/value_formatter_test.go

@@ -143,6 +143,90 @@ func TestFormatters(t *testing.T) {
 			formatter: ValueFormatterSingleUnitDuration(time.Nanosecond, 8),
 			want:      "",
 		},
+		{
+			desc:      "Round formatter handles NaN values",
+			value:     math.NaN(),
+			formatter: ValueFormatterRound,
+			want:      "",
+		},
+		{
+			desc:      "Round formatter handles 0 values",
+			value:     0,
+			formatter: ValueFormatterRound,
+			want:      "0",
+		},
+		{
+			desc:      "Round formatter handles > x.5 values",
+			value:     96.7,
+			formatter: ValueFormatterRound,
+			want:      "97",
+		},
+		{
+			desc:      "Round formatter handles < x.5 values",
+			value:     1621.2,
+			formatter: ValueFormatterRound,
+			want:      "1621",
+		},
+		{
+			desc:      "Round formatter handles x.5 values",
+			value:     6.5,
+			formatter: ValueFormatterRound,
+			want:      "7",
+		},
+		{
+			desc:      "Round formatter handles minus > x.5 values",
+			value:     -96.7,
+			formatter: ValueFormatterRound,
+			want:      "-97",
+		},
+		{
+			desc:      "Round formatter handles minus < x.5 values",
+			value:     -1621.2,
+			formatter: ValueFormatterRound,
+			want:      "-1621",
+		},
+		{
+			desc:      "Round formatter handles minus x.5 values",
+			value:     -6.5,
+			formatter: ValueFormatterRound,
+			want:      "-7",
+		},
+		{
+			desc:      "Round formatter handles values with suffix",
+			value:     96.7,
+			formatter: ValueFormatterRoundWithSuffix("km"),
+			want:      "97km",
+		},
+		{
+			desc:      "Suffix formatter handles values with decimals",
+			value:     11234567890.71234567890,
+			formatter: ValueFormatterSuffix(4, " reqps"),
+			want:      "11234567890.7123 reqps",
+		},
+		{
+			desc:      "Suffix formatter handles NaN values",
+			value:     math.NaN(),
+			formatter: ValueFormatterSuffix(2, "test"),
+			want:      "",
+		},
+		{
+			desc:      "Suffix formatter handles 0 values",
+			value:     0,
+			formatter: ValueFormatterSuffix(2, "test"),
+			want:      "0.00test",
+		},
+		{
+			desc:      "Suffix formatters handles correctly percent suffix",
+			value:     96.78,
+			formatter: ValueFormatterSuffix(2, "%"),
+			want:      "96.78%",
+		},
+		{
+			desc:      "Round formatter handles values with percent suffix",
+			value:     96.7,
+			formatter: ValueFormatterRoundWithSuffix("%"),
+			want:      "97%",
+		},
 	}
 
 	for _, tc := range tests {