62 lines
1.3 KiB
Go
62 lines
1.3 KiB
Go
package flags
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import (
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"fmt"
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"os"
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"reflect"
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"strings"
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"text/tabwriter"
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)
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type Arg struct {
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Val string
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Help string
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}
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// type constraint
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type Val interface {
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string | bool
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}
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// with generic Val field, instantiate like Flag[string]
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type Flag[V Val] struct {
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Long string
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Short string
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Val V
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Help string
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}
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func HasDashPrefix(s string) bool {
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return strings.HasPrefix(s, "-")
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}
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func MissingValueArg(args []string, i int) bool {
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return i+1 == len(args) || HasDashPrefix(args[i+1])
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}
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func HelpMissingVal(flag string) {
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fmt.Printf("%s needs a value assignment\n", flag)
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}
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// print out help string by reflecting over fields of provided opts struct
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func Help(subcmd string, opts any) {
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v := reflect.ValueOf(opts)
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t := v.Type()
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fmt.Printf("um %s usage:\n", subcmd)
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w := tabwriter.NewWriter(os.Stdout, 0, 0, 3, ' ', 0)
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for i := 0; i < v.NumField(); i++ {
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field := t.Field(i)
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value := v.Field(i)
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switch value.Interface().(type) {
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case Arg:
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fmt.Fprintf(w, "[%v]\tstring\t%v\n", strings.ToLower(field.Name), value.FieldByName("Help"))
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case Flag[string]:
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fmt.Fprintf(w, "%v | %v\tstring\t%v\n", value.FieldByName("Long"), value.FieldByName("Short"), value.FieldByName("Help"))
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case Flag[bool]:
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fmt.Fprintf(w, "%v | %v\tbool\t%v\n", value.FieldByName("Long"), value.FieldByName("Short"), value.FieldByName("Help"))
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}
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}
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w.Flush()
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}
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