//! Duplicate detection: an imported item duplicates an existing one (or an earlier one in the
//! same import) when (title, username, primary URL host) match, case-insensitively.

use std::collections::HashSet;

use kv_model::Item;

pub const IMPORTED_SUFFIX: &str = " (imported)";

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DuplicatePolicy {
    /// Leave the existing item alone and drop the imported one.
    Skip,
    /// Import it anyway, with `" (imported)"` appended to the title.
    AddSuffix,
}

pub type Key = (String, String, String);

/// Host of the first URL, lowercased, without a leading `www.`. Empty when there is no usable URL.
pub fn primary_host(item: &Item) -> String {
    let Some(raw) = item.urls.first().map(|u| u.trim()) else { return String::new() };
    let parsed = url::Url::parse(raw).ok().filter(|u| u.host_str().is_some()).or_else(|| {
        // Bare "example.com/login" from CSVs.
        url::Url::parse(&format!("https://{raw}")).ok()
    });
    let host = parsed.and_then(|u| u.host_str().map(str::to_lowercase)).unwrap_or_else(|| raw.to_lowercase());
    host.strip_prefix("www.").map(str::to_string).unwrap_or(host)
}

pub fn key(item: &Item) -> Key {
    (item.title.trim().to_lowercase(), item.username.as_deref().unwrap_or("").trim().to_lowercase(), primary_host(item))
}

pub struct Plan {
    /// Items to store, in input order.
    pub to_add: Vec<Item>,
    /// Indices into the input of the duplicates (skipped or renamed).
    pub duplicates: Vec<usize>,
    pub skipped: u32,
    pub renamed: u32,
}

/// Decides what to store. `existing` are the keys of the items already in the vault.
pub fn plan(items: Vec<Item>, existing: impl IntoIterator<Item = Key>, policy: DuplicatePolicy) -> Plan {
    let mut seen: HashSet<Key> = existing.into_iter().collect();
    let mut out = Plan { to_add: Vec::with_capacity(items.len()), duplicates: vec![], skipped: 0, renamed: 0 };
    for (idx, mut item) in items.into_iter().enumerate() {
        let k = key(&item);
        if !seen.contains(&k) {
            seen.insert(k);
            out.to_add.push(item);
            continue;
        }
        out.duplicates.push(idx);
        match policy {
            DuplicatePolicy::Skip => out.skipped += 1,
            DuplicatePolicy::AddSuffix => {
                item.title.push_str(IMPORTED_SUFFIX);
                // Importing the same file twice still yields only one "(imported)" copy per key.
                while !seen.insert(key(&item)) {
                    item.title.push_str(IMPORTED_SUFFIX);
                }
                out.renamed += 1;
                out.to_add.push(item);
            }
        }
    }
    out
}

#[cfg(test)]
mod tests {
    use super::*;

    fn login(title: &str, user: &str, url: &str) -> Item {
        let mut i = Item::new_login(title, 0);
        i.username = Some(user.into());
        if !url.is_empty() {
            i.urls = vec![url.into()];
        }
        i
    }

    #[test]
    fn host_normalization() {
        assert_eq!(primary_host(&login("a", "b", "https://WWW.Example.com/login?x=1")), "example.com");
        assert_eq!(primary_host(&login("a", "b", "example.com/login")), "example.com");
        assert_eq!(primary_host(&login("a", "b", "")), "");
    }

    #[test]
    fn skip_and_suffix() {
        let existing = [key(&login("GitHub", "me", "https://github.com"))];
        let items = vec![
            login("github", "ME", "https://github.com/login"),
            login("GitHub", "other", "https://github.com"),
            login("Mail", "me", "https://mail.example"),
            login("Mail", "me", "https://mail.example/inbox"),
        ];
        let p = plan(items.clone(), existing.clone(), DuplicatePolicy::Skip);
        assert_eq!((p.to_add.len(), p.skipped, p.renamed), (2, 2, 0));
        assert_eq!(p.duplicates, vec![0, 3]);

        let p = plan(items, existing, DuplicatePolicy::AddSuffix);
        assert_eq!((p.to_add.len(), p.skipped, p.renamed), (4, 0, 2));
        assert_eq!(p.to_add[0].title, "github (imported)");
        assert_eq!(p.to_add[3].title, "Mail (imported)");
    }
}