find_next_serial.rs

struct IndexGetter {
    current_serial: u32,
    tags: Vec<Tag>,
}

#[derive(Clone)]
struct Tag {
    pub serial: u32,
    pub tag: String,
}

impl IndexGetter {
    pub fn new(tags: &[Tag]) -> Self {
        Self {
            current_serial: 0,
            tags: tags.to_vec(),
        }
    }

    pub fn next_serial(&mut self, new_tag: &str) -> u32 {
        // Check if new tag matches an old tag, then use its serial
        if let Some(old_tag) = self.tags.iter().find(|x| x.tag == new_tag) {
            return old_tag.serial;
        }

        // Skip over other used serials
        let mut new_serial = self.current_serial + 1;
        for a in &self.tags {
            if new_serial == a.serial {
                new_serial += 1;
            }
        }
        self.current_serial = new_serial;

        self.current_serial
    }
}

fn main() {
    let tags = vec![
        Tag {
            serial: 2,
            tag: "TAG_A".to_string(),
        },
        Tag {
            serial: 4,
            tag: "TAG_B".to_string(),
        },
    ];
    let mut getter = IndexGetter::new(&tags);

    let new_tags = vec!["TAG_A", "TAG_C", "TAG_B", "TAG_D"];

    for new_tag in new_tags {
        println!("{}", getter.next_serial(new_tag));
    }
}