realpath: implement it

common/realpath/args.v

@@ -0,0 +1,133 @@
+module realpath
+
+import common
+
+pub fn parse_args(args []string) Settings {
+	mut s := Settings{}
+	mut operands := []string{}
+
+	for i := 0; i < args.len; i++ {
+		a := args[i]
+		if a == '--' {
+			operands << args[i + 1..]
+			break
+		}
+		if a == '--help' {
+			print_help()
+			exit(0)
+		}
+		if a == '--version' {
+			println('realpath (V coreutils) ${common.version}')
+			exit(0)
+		}
+		if !a.starts_with('-') || a == '-' {
+			operands << a
+			continue
+		}
+
+		if a.starts_with('--') {
+			name := a.all_before('=')
+			val := a.all_after('=')
+			has_val := a.contains('=')
+			match name {
+				'--canonicalize-existing' {
+					s.must_exist = true
+				}
+				'--canonicalize-missing' {
+					s.allow_missing = true
+				}
+				'--no-symlinks' {
+					s.no_symlinks = true
+				}
+				'--zero' {
+					s.zero_terminated = true
+				}
+				'--quiet' {
+					s.quiet = true
+				}
+				'--relative-to' {
+					v, next := take_value(args, i, val, has_val, name)
+					i = next
+					s.relative_to = v
+				}
+				'--relative-base' {
+					v, next := take_value(args, i, val, has_val, name)
+					i = next
+					s.relative_base = v
+				}
+				'--logical' {
+					s.no_symlinks = true
+				}
+				'--physical' {}
+				else {
+					common.exit_with_error_message('realpath', "unrecognized option '${a}'")
+				}
+			}
+			continue
+		}
+
+		mut j := 1
+		for j < a.len {
+			c := a[j]
+			match c {
+				`e` {
+					s.must_exist = true
+				}
+				`m` {
+					s.allow_missing = true
+				}
+				`s` {
+					s.no_symlinks = true
+				}
+				`z` {
+					s.zero_terminated = true
+				}
+				`q` {
+					s.quiet = true
+				}
+				`L` {
+					s.no_symlinks = true
+				}
+				`P` {}
+				`-` {
+					j++
+					continue
+				}
+				else {
+					common.exit_with_error_message('realpath', "invalid option -- '${c.ascii_str()}'")
+				}
+			}
+			j++
+		}
+	}
+
+	s.operands = operands
+	return s
+}
+
+fn take_value(args []string, i int, inline_val string, has_val bool, name string) (string, int) {
+	if has_val {
+		return inline_val, i
+	}
+	if i + 1 >= args.len {
+		common.exit_with_error_message('realpath', "option '${name}' requires an argument")
+	}
+	return args[i + 1], i + 1
+}
+
+fn print_help() {
+	println('Usage: realpath [OPTION]... FILE...')
+	println('Print the resolved absolute file name; all but the last component must exist')
+	println('')
+	println('  -e, --canonicalize-existing  all components of the path must exist')
+	println('  -m, --canonicalize-missing   no path components need exist')
+	println('  -L, --logical                resolve .. components before symlinks')
+	println('  -P, --physical               resolve symlinks as encountered (default)')
+	println('  -q, --quiet                  suppress most error messages')
+	println('      --relative-to=DIR        print the resolved path relative to DIR')
+	println('      --relative-base=DIR      print absolute paths unless paths below DIR')
+	println('  -s, --strip, --no-symlinks   do not expand symlinks')
+	println('  -z, --zero                   end each output line with NUL, not newline')
+	println('      --help        display this help and exit')
+	println('      --version     output version information and exit')
+}