support -h

config.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"encoding/json"
+	"flag"
 	"fmt"
 	"log"
 	"net/url"
@@ -29,20 +30,29 @@ type Data struct {
 }
 
 func newConfig() (Config, error) {
-	var result Config
-	result.Data.Points = [][]float64{
-		[]float64{1, 1},
-		[]float64{2, 2},
-		[]float64{2, 2},
-	}
-	result.Data.Weight.Floor = 12
-	result.Data.Weight.Range = 20
-	result.Output = url.URL{Scheme: "file", Path: "/tmp/f"}
-	result.Data.Title = os.Getenv("TITLE")
-	result.Data.Subtitle = os.Getenv("SUBTITLE")
+	dataPoints := envOr("DATA_POINTS", `[[1, 1], [2, 2], [2, 2]]`)
+	dataLabels := envOr("DATA_LABELS", ``)
+	dataWeightFloor := envOr("DATA_WEIGHT_FLOOR", `12`)
+	dataWeightRange := envOr("DATA_WEIGHT_RANGE", `20`)
+	dataTitle := envOr("DATA_TITLE", ``)
+	dataSubtitle := envOr("DATA_SUBTITLE", ``)
+	output := envOr("OUTPUT", `file:///tmp/f`)
 
-	if js := os.Getenv("POINTS_JSON"); js == "" {
-	} else if err := json.Unmarshal([]byte(js), &result.Data.Points); err != nil {
+	fs := flag.NewFlagSet("cmd", flag.ContinueOnError)
+	fs.StringVar(&dataPoints, "data-points", dataPoints, `JSON [[x, y, z, ...]]`)
+	fs.StringVar(&dataLabels, "data-labels", dataLabels, `(optional) JSON ["foo", "bar", "baz"]`)
+	fs.StringVar(&dataWeightFloor, "data-weight-floor", dataWeightFloor, `int min point size`)
+	fs.StringVar(&dataWeightRange, "data-weight-range", dataWeightRange, `int max point scale up`)
+	fs.StringVar(&dataTitle, "data-title", dataTitle, `chart title`)
+	fs.StringVar(&dataSubtitle, "data-subtitle", dataSubtitle, `chart subtitle`)
+	fs.StringVar(&output, "output", output, `scheme://location`)
+	if err := fs.Parse(os.Args[1:]); err != nil {
+		return Config{}, err
+	}
+
+	var result Config
+
+	if err := json.Unmarshal([]byte(dataPoints), &result.Data.Points); err != nil {
 		return result, err
 	}
 
@@ -57,31 +67,28 @@ func newConfig() (Config, error) {
 			result.Data.Labels[i] = fmt.Sprintf("%c", byte(int('A')+i))
 		}
 
-		if js := os.Getenv("LABELS_JSON"); js == "" {
-		} else if err := json.Unmarshal([]byte(js), &result.Data.Labels); err != nil {
+		if dataLabels == "" {
+		} else if err := json.Unmarshal([]byte(dataLabels), &result.Data.Labels); err != nil {
 			return result, err
 		} else if len(result.Data.Labels) < len(result.Data.Points[0]) {
 			return result, fmt.Errorf("expected at least %d labels but got %d", len(result.Data.Points[0]), len(result.Data.Labels))
 		}
 	}
 
-	if js := os.Getenv("WEIGHT_RANGE"); js == "" {
-	} else if err := json.Unmarshal([]byte(js), &result.Data.Weight.Range); err != nil {
+	if err := json.Unmarshal([]byte(dataWeightRange), &result.Data.Weight.Range); err != nil {
 		return result, err
 	} else if result.Data.Weight.Range < 0 {
 		return result, fmt.Errorf("found negative weight range %d", result.Data.Weight.Range)
 	}
 
-	if js := os.Getenv("WEIGHT_FLOOR"); js == "" {
-	} else if err := json.Unmarshal([]byte(js), &result.Data.Weight.Floor); err != nil {
+	if err := json.Unmarshal([]byte(dataWeightFloor), &result.Data.Weight.Floor); err != nil {
 		return result, err
 	} else if result.Data.Weight.Floor < 0 {
 		return result, fmt.Errorf("found negative weight floor %d", result.Data.Weight.Floor)
 	}
 
-	if s := os.Getenv("OUTPUT"); s == "" {
-	} else if u, err := url.Parse(s); err != nil {
-		return result, fmt.Errorf("failed to parse $OUTPUT (%s): %w", s, err)
+	if u, err := url.Parse(output); err != nil {
+		return result, fmt.Errorf("failed to parse $OUTPUT (%s): %w", output, err)
 	} else {
 		result.Output = *u
 	}
@@ -89,6 +96,13 @@ func newConfig() (Config, error) {
 	return result, nil
 }
 
+func envOr(k, v string) string {
+	if s := os.Getenv(k); s != "" {
+		return s
+	}
+	return v
+}
+
 func (d Data) AsScatterData() (string, []float64, string, []opts.ScatterData, error) {
 	if !(2 <= len(d.Labels) && len(d.Labels) <= 3) {
 		return "", nil, "", nil, fmt.Errorf("cannot map %d dimensions to [2,3]", len(d.Labels))