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53 lines
1.5 KiB
Go
53 lines
1.5 KiB
Go
package Z
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import (
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"fmt"
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"strings"
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"github.com/rwxrob/fn/filt"
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)
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// UsageGroup uses Bonzai usage notation, a basic form of regular
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// expressions, to describe the arguments allowed where each argument is
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// a literal string (avoid spaces). The arguments are joined with bars
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// (|) and wrapped with parentheses producing a regex group. The min
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// and max are then applied by adding the following regex decorations
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// after the final parenthesis:
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//
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// - min=1 max=1 (exactly one)
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// ? - min=0 max=0 (none or many)
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// + - min=1 max=0 (one or more)
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// {min,} - min>0 max=0 (min, no max)
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// {min,max} - min>0 max>0 (min and max)
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// {,max} - min=0 max>0 (max, no min)
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//
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// An empty args slice returns an empty string. If only one arg, then
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// that arg is simply returned and min and max are ignored. Arguments
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// that are empty strings are ignored. No transformation is done to the
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// string itself (such as removing white space).
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func UsageGroup(args []string, min, max int) string {
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args = filt.NotEmpty(args)
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switch len(args) {
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case 0:
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return ""
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case 1:
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return args[0]
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default:
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var dec string
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switch {
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case min == 1 && max == 1:
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case min == 0 && max == 0:
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dec = "?"
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case min == 1 && max == 0:
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dec = "+"
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case min > 1 && max == 0:
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dec = fmt.Sprintf("{%v,}", min)
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case min > 0 && max > 0:
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dec = fmt.Sprintf("{%v,%v}", min, max)
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case min == 0 && max > 1:
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dec = fmt.Sprintf("{,%v}", max)
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}
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return "(" + strings.Join(args, "|") + ")" + dec
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}
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}
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