386 lines
11 KiB
V
386 lines
11 KiB
V
module flag
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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 print 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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// data object storing information about a defined flag
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pub struct Flag {
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pub:
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name string // name as it appears on command line
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abbr byte // shortcut
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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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// and also the default value, when the flag is not given
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}
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//
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pub 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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args_description string
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}
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pub const (
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// used for formating usage message
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SPACE = ' '
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UNDERLINE = '-----------------------------------------------'
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MAX_ARGS_NUMBER = 4048
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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: MAX_ARGS_NUMBER}
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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 string, a byte, u, vd string) {
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fs.flags << Flag{
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name: n,
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abbr: a,
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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 existence
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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, ab byte) ?string {
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c := '--$n'
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for i, a in fs.args {
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if a == c || (a.len == 2 && a[1] == ab) {
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if i+1 > fs.args.len { panic('Missing argument for \'$n\'') }
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nextarg := fs.args[i+1]
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if nextarg.limit(2) == '--' { panic('Missing argument for \'$n\'') }
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val := fs.args[i+1]
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fs.args.delete(i+1)
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fs.args.delete(i)
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return val
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} else if a.len > c.len && c == a[..c.len] && a[c.len..c.len+1] == '=' {
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val := a[c.len+1..]
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fs.args.delete(i)
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return val
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}
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}
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return error('parameter \'$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, ab byte) ?string {
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c := '--$n'
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for i, a in fs.args {
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if a == c || (a.len == 2 && a[1] == ab) {
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if fs.args.len > i+1 && (fs.args[i+1] in ['true', 'false']) {
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val := fs.args[i+1]
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fs.args.delete(i+1)
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fs.args.delete(i)
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return val
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} else {
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val := 'true'
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fs.args.delete(i)
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return val
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}
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} else if a.len > c.len && c == a[..c.len] && a[c.len..c.len+1] == '=' {
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val := a[c.len+1..]
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fs.args.delete(i)
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return val
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}
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}
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return error('parameter \'$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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// version with abbreviation
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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, a byte, v bool, u string) bool {
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fs.add_flag(n, a, u, '<bool>:'+v.str())
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parsed := fs.parse_bool_value(n, a) 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 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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return fs.bool_(n, `\0`, v, u)
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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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// version with abbreviation
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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, a byte, i int, u string) int {
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fs.add_flag(n, a, u, '<int>:$i')
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parsed := fs.parse_value(n, a) or {
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return i
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}
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return parsed.int()
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}
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// defining and parsing an int flag
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// if defined
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// the value is returned (int)
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// else
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// the default value is returned
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//TODO error handling for invalid string to int conversion
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pub fn (fs mut FlagParser) int(n string, i int, u string) int {
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return fs.int_(n, `\0`, i, u)
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}
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// defining and parsing a float flag
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// if defined
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// the value is returned (float)
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// else
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// the default value is returned
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// version with abbreviation
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//TODO error handling for invalid string to float conversion
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pub fn (fs mut FlagParser) float_(n string, a byte, f f32, u string) f32 {
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fs.add_flag(n, a, u, '<float>:$f')
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parsed := fs.parse_value(n, a) 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 float 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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return fs.float_(n, `\0`, f, u)
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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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// version with abbreviation
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pub fn (fs mut FlagParser) string_(n string, a byte, v, u string) string {
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fs.add_flag(n, a, u, '<string>:$v')
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parsed := fs.parse_value(n, a) 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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// 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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return fs.string_(n, `\0`, v, u)
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}
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pub fn (fs mut FlagParser) limit_free_args_to_at_least(n int) {
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if n > MAX_ARGS_NUMBER {
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panic('flag.limit_free_args_to_at_least expect n to be smaller than $MAX_ARGS_NUMBER')
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}
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if n <= 0 {
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panic('flag.limit_free_args_to_at_least expect n to be a positive number')
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}
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fs.min_free_args = n
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}
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pub fn (fs mut FlagParser) limit_free_args_to_exactly(n int) {
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if n > MAX_ARGS_NUMBER {
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panic('flag.limit_free_args_to_exactly expect n to be smaller than $MAX_ARGS_NUMBER')
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}
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if n < 0 {
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panic('flag.limit_free_args_to_exactly expect n to be a non negative number')
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}
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fs.min_free_args = n
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fs.max_free_args = n
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}
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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 >= $max')
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}
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fs.min_free_args = min
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fs.max_free_args = max
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}
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pub fn (fs mut FlagParser) arguments_description(description string){
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fs.args_description = description
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}
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// collect all given information and
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pub fn (fs FlagParser) usage() string {
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positive_min_arg := ( fs.min_free_args > 0 )
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positive_max_arg := ( fs.max_free_args > 0 && fs.max_free_args != MAX_ARGS_NUMBER )
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no_arguments := ( fs.min_free_args == 0 && fs.max_free_args == 0 )
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mut adesc := if fs.args_description.len > 0 { fs.args_description } else { '[ARGS]' }
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if no_arguments { adesc = '' }
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mut use := ''
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use += '$fs.application_name $fs.application_version\n'
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use += '$UNDERLINE\n'
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use += 'Usage: ${fs.application_name} [options] $adesc\n'
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use += '\n'
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if fs.application_description != '' {
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use += 'Description:\n'
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use += '$fs.application_description'
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use += '\n\n'
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}
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// show a message about the [ARGS]:
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if positive_min_arg || positive_max_arg || no_arguments {
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if no_arguments {
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use += 'This application does not expect any arguments\n\n'
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goto end_of_arguments_handling
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}
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mut s:= []string
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if positive_min_arg { s << 'at least $fs.min_free_args' }
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if positive_max_arg { s << 'at most $fs.max_free_args' }
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if positive_min_arg && positive_max_arg && fs.min_free_args == fs.max_free_args {
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s = ['exactly $fs.min_free_args']
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}
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sargs := s.join(' and ')
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use += 'The arguments should be $sargs in number.\n\n'
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}
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end_of_arguments_handling:
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if fs.flags.len > 0 {
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use += 'Options:\n'
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for f in fs.flags {
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flag_desc := ' --$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[flag_desc.len..]
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}
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abbr_desc := if f.abbr == `\0` { '' } else { ' -${tos(f.abbr, 1)}\n' }
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use += '${abbr_desc}${flag_desc}${space}${f.usage}\n'
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}
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}
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return use
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}
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// finalize argument parsing -> call after all arguments are defined
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//
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// all remaining arguments are returned in the same order they are defined on
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// command line
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//
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// if additional flag are found (things starting with '--') an error is returned
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// error handling is up to the application developer
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pub fn (fs FlagParser) finalize() ?[]string {
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for a in fs.args {
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if a.len >= 2 && a[..2] == '--' {
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return error('Unknown argument \'${a[2..]}\'')
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}
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}
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if fs.args.len < fs.min_free_args && fs.min_free_args > 0 {
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return error('Expected at least ${fs.min_free_args} arguments, but given $fs.args.len')
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}
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if fs.args.len > fs.max_free_args && fs.max_free_args > 0 {
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return error('Expected at most ${fs.max_free_args} arguments, but given $fs.args.len')
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}
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if fs.args.len > 0 && fs.max_free_args == 0 && fs.min_free_args == 0 {
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return error('Expected no arguments, but given $fs.args.len')
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}
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return fs.args
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}
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