fn isWhitespace(c: u8) bool {
    return c == ' ' or c == '\t' or c == '\n' or c == '\r';
}
pub const Cmdline = struct {
    ptr: []const u8,
    pub fn init(ptr: []const u8) Cmdline {
        return Cmdline{
            .ptr = ptr,
        };
    }
    fn _parseArg(self: *const Cmdline, key: []const u8, buf: []u8) ?usize {
        var state: union(enum) {
            search_key,
            compare_key: usize,
            copy_value: usize,
            skip_arg
        } = .search_key;
        var i: usize = 0;
        while (i < self.ptr.len) {
            const c = self.ptr[i];
            switch (state) {
                .search_key => {
                    if (isWhitespace(c)) {
                        i = i + 1;
                        continue;
                    }
                    state = .{ .compare_key = 0};
                },
                .compare_key => |key_index| {
                    if (key_index < key.len) {
                        if (c == key[key_index]) {
                            state = .{ .compare_key = key_index + 1 };
                        } else {
                            state = .skip_arg;
                        }
                    } else {
                        if (c == '=') {
                            state = .{ .copy_value = 0 };
                        } else if (isWhitespace(c)) {
                            return 0;
                        } else {
                            state = .skip_arg;
                        }
                    }
                    i = i + 1;
                },
                .skip_arg => {
                    if (isWhitespace(c)) {
                        state = .search_key;
                    }
                    i = i + 1;
                },
                .copy_value => |buf_index| {
                    if (isWhitespace(c) or buf_index >= buf.len) {
                        return buf_index;
                    }
                    buf[buf_index] = c;
                    state = .{ .copy_value = buf_index + 1 };
                    i = i + 1;
                },
            }
        }
        switch (state) {
            .copy_value => |buf_index| return buf_index,
            else => return null
        }
    }
    pub fn parseArg(self: *const Cmdline, key: []const u8, buf: []u8) ?usize {
        return self._parseArg(key, buf);
    }
    pub fn parseArgBool(self: *const Cmdline, key: []const u8) bool {
        const result = self._parseArg(key, &[_]u8{});
        if (result) {
            return true;
        } else {
            return false;
        }
    }
};