82 lines
2 KiB
Go
82 lines
2 KiB
Go
package flags
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import (
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"bytes"
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"fmt"
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"reflect"
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"strings"
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"text/tabwriter"
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"github.com/brtholomy/um/go/cmd"
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)
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type HelpError struct {
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sub cmd.Subcommand
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summary string
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message string
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}
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func (h HelpError) Error() string {
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return h.message
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}
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// TODO: is this odd? Constructing an error at the callsite and passing it down and back up?
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// but how else should I fill out its fields to be reused later?
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func NewHelpError(sub cmd.Subcommand, summary string) HelpError {
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return HelpError{sub, summary, ""}
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}
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func (h HelpError) HelpRequired(long string) error {
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h.message = fmt.Sprintf("um %s: %s is required", h.sub, long)
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return h
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}
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func (h HelpError) HelpInvalidArg(arg string) error {
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h.message = fmt.Sprintf("um %s: invalid argument: %s", h.sub, arg)
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return h
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}
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func (h HelpError) HelpMissingAssignment(arg string) error {
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h.message = fmt.Sprintf("um %s: %s needs a value assignment", h.sub, arg)
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return h
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}
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// assemble --help string by reflecting over fields of provided opts struct
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func (h HelpError) Help(opts any) error {
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v := reflect.ValueOf(opts)
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if v.Kind() == reflect.Ptr {
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v = v.Elem()
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}
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t := v.Type()
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buf := &bytes.Buffer{}
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w := tabwriter.NewWriter(buf, 0, 0, 3, ' ', 0)
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positional := ""
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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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positional += fmt.Sprintf(" [%s]", strings.ToLower(field.Name))
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fmt.Fprintf(w, "[%v]\tstring\t%v\n", strings.ToLower(field.Name), value.FieldByName("Help"))
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case String, Bool:
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if field.Name != "Help" {
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positional += fmt.Sprintf(" [%s]", value.FieldByName("Long"))
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}
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fmt.Fprintf(w, "%v | %v\t%v\t%v\n",
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value.FieldByName("Long"),
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value.FieldByName("Short"),
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value.FieldByName("Val").Type(),
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value.FieldByName("Help"),
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)
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}
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}
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if _, err := buf.WriteString(fmt.Sprintf("um %s%s\n\n%s\n\n", h.sub, positional, h.summary)); err != nil {
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return err
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}
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w.Flush()
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h.message = buf.String()
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return h
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}
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