290 lines
7.4 KiB
Go
290 lines
7.4 KiB
Go
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// module flag for command-line flag parsing
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//
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// - parsing flags like '--flag' or '--stuff=things' or '--things stuff'
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// - handles bool, int, float and string args
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// - is able to pring usage
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// - handled unknown arguments as error
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//
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// Usage example:
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//
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// ```v
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// module main
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//
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// import os
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// import flag
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//
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// fn main() {
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// mut fp := flag.new_flag_parser(os.args)
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// fp.application('flag_example_tool')
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// fp.version('v0.0.0')
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// fp.description('This tool is only designed to show how the flag lib is working')
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//
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// fp.skip_executable()
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//
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// an_int := fp.int('an_int', 666, 'some int to define 666 is default')
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// a_bool := fp.bool('a_bool', false, 'some \'real\' flag')
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// a_float := fp.float('a_float', 1.0, 'also floats')
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// a_string := fp.string('a_string', 'no text', 'finally, some text')
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//
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// additional_args := fp.finalize() or {
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// eprintln(err)
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// println(fp.usage())
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// return
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// }
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//
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// println('
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// an_int: $an_int
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// a_bool: $a_bool
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// a_float: $a_float
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// a_string: \'$a_string\'
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// ')
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// println(additional_args.join_lines())
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// }
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// ```
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module flag
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// data object storing informations about a defined flag
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struct Flag {
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pub:
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name string // name as it appears on command line
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usage string // help message
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val_desc string // something like '<arg>' that appears in usage
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}
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//
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struct FlagParser {
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pub mut:
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args []string // the arguments to be parsed
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flags []Flag // registered flags
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application_name string
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application_version string
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application_description string
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min_free_args int
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max_free_args int
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}
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// create a new flag set for parsing command line arguments
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// TODO use INT_MAX some how
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pub fn new_flag_parser(args []string) &FlagParser {
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return &FlagParser{args:args, max_free_args: 4048}
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}
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// change the application name to be used in 'usage' output
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pub fn (fs mut FlagParser) application(n string) {
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fs.application_name = n
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}
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// change the application version to be used in 'usage' output
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pub fn (fs mut FlagParser) version(n string) {
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fs.application_version = n
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}
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// change the application version to be used in 'usage' output
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pub fn (fs mut FlagParser) description(n string) {
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fs.application_description = n
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}
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// in most cases you do not need the first argv for flag parsing
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pub fn (fs mut FlagParser) skip_executable() {
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fs.args.delete(0)
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}
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// private helper to register a flag
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fn (fs mut FlagParser) add_flag(n, u, vd string) {
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fs.flags << Flag{
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name: n,
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usage: u
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val_desc: vd
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}
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}
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// private: general parsing a single argument
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// - search args for existance
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// if true
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// extract the defined value as string
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// else
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// return an (dummy) error -> argument is not defined
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//
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// - the name, usage are registered
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// - found arguments and corresponding values are removed from args list
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fn (fs mut FlagParser) parse_value(n string) ?string {
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c := '--$n'
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for i, a in fs.args {
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if a == c {
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if fs.args.len > i+1 && fs.args[i+1].left(2) != '--' {
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val := fs.args[i+1]
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fs.args.delete(i+1)
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fs.args.delete(i)
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return val
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} else {
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panic('Missing argument for \'$n\'')
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}
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} else if a.len > c.len && c == a.left(c.len) && a.substr(c.len, c.len+1) == '=' {
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val := a.right(c.len+1)
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fs.args.delete(i)
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return val
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}
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}
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return error('parameter \'$n\' not found')
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}
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// special parsing for bool values
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// see also: parse_value
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//
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// special: it is allowed to define bool flags without value
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// -> '--flag' is parsed as true
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// -> '--flag' is equal to '--flag=true'
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fn (fs mut FlagParser) parse_bool_value(n string) ?string {
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c := '--$n'
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for i, a in fs.args {
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if a == c {
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if fs.args.len > i+1 && (fs.args[i+1] in ['true', 'false']) {
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val := fs.args[i+1]
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fs.args.delete(i+1)
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fs.args.delete(i)
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return val
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} else {
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val := 'true'
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fs.args.delete(i)
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return val
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}
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} else if a.len > c.len && c == a.left(c.len) && a.substr(c.len, c.len+1) == '=' {
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val := a.right(c.len+1)
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fs.args.delete(i)
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return val
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}
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}
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return error('parameter \'$n\' not found')
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}
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// defining and parsing a bool flag
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// if defined
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// the value is returned (true/false)
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// else
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// the default value is returned
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//TODO error handling for invalid string to bool conversion
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pub fn (fs mut FlagParser) bool(n string, v bool, u string) bool {
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fs.add_flag(n, u, '')
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parsed := fs.parse_bool_value(n) or {
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return v
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}
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return parsed == 'true'
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}
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// defining and parsing an int flag
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// if defined
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// the value is returned (int)
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// else
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// the default value is returned
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//TODO error handling for invalid string to int conversion
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pub fn (fs mut FlagParser) int(n string, i int, u string) int {
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fs.add_flag(n, u, '<int>')
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parsed := fs.parse_value(n) or {
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return i
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}
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return parsed.int()
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}
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// defining and parsing a flaot flag
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// if defined
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// the value is returned (float)
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// else
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// the default value is returned
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//TODO error handling for invalid string to float conversion
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pub fn (fs mut FlagParser) float(n string, f f32, u string) f32 {
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fs.add_flag(n, u, '<float>')
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parsed := fs.parse_value(n) or {
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return f
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}
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return parsed.f32()
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}
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// defining and parsing a string flag
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// if defined
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// the value is returned (string)
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// else
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// the default value is returned
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pub fn (fs mut FlagParser) string(n, v, u string) string {
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fs.add_flag(n, u, '<arg>')
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parsed := fs.parse_value(n) or {
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return v
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}
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return parsed
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}
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// add an additional check for free arguments
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// this will cause an error in finalize() if free args are out of range
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// (min, ..., max)
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pub fn (fs mut FlagParser) limit_free_args(min, max int) {
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if min > max {
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panic('flag.limit_free_args expect min < max, got $min >= $max')
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}
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fs.min_free_args = min
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fs.max_free_args = max
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}
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const (
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// used for formating usage message
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SPACE = ' '
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)
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// collect all given information and
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pub fn (fs FlagParser) usage() string {
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mut use := '\n'
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use += 'usage ${fs.application_name} [options] [ARGS]\n'
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use += '\n'
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if fs.flags.len > 0 {
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use += 'options:\n'
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for f in fs.flags {
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flag_desc := ' --$f.name $f.val_desc'
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space := if flag_desc.len > SPACE.len-2 {
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'\n$SPACE'
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} else {
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SPACE.right(flag_desc.len)
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}
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use += '$flag_desc$space$f.usage\n'
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}
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}
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use += '\n'
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use += '$fs.application_name $fs.application_version\n'
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if fs.application_description != '' {
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use += '\n'
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use += 'description:\n'
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use += '$fs.application_description'
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}
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return use
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}
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// finalize argument parsing -> call after all arguments are defined
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//
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// all remaining arguments are returned in the same order they are defined on
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// commandline
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//
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// if additional flag are found (things starting with '--') an error is returned
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// error handling is up to the application developer
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pub fn (fs FlagParser) finalize() ?[]string {
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for a in fs.args {
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if a.left(2) == '--' {
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return error('Unknown argument \'${a.right(2)}\'')
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}
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}
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if fs.args.len < fs.min_free_args {
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return error('Expect at least ${fs.min_free_args} arguments')
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}
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if fs.args.len >= fs.max_free_args {
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if fs.max_free_args > 0 {
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return error('Expect at most ${fs.max_free_args} arguments')
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} else {
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return error('Expect no arguments')
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}
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}
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return fs.args
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}
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