//! Game-independent owned-inventory query: semantic filtering, deterministic
//! ordering, and offset/limit pagination over a club's owned items.
//!
//! This layer is deliberately free of any game-specific concepts. It never sees
//! raw FIFA (or any other game's) numeric entity ids — a game adapter is
//! responsible for translating its wire query into the *semantic* values here
//! (quality tier, entity **names**, semantic offset/limit). The canonical
//! ordering is imposed by Core so pagination is correct and repeatable
//! regardless of what (if any) sort the client requests; see the module tests
//! and `docs`/vault for why the client's `sort` key is treated as UNKNOWN.
//!
//! Order of operations is load-bearing: **filter → order → paginate**. Paginating
//! before filtering is the production bug this replaces (a client that pages an
//! unfiltered/unsorted set re-reads page one forever and amplifies requests).

use serde::Deserialize;

use crate::models::card::Quality;

/// Semantic owned-inventory query. All values are game-independent: a quality
/// tier, entity **names** (not ids), and semantic offset/limit. Every filter is
/// optional; combined filters are ANDed. Absent field = no constraint.
#[derive(Debug, Default, Deserialize)]
pub struct OwnedItemQuery {
    /// Quality tier (gold/silver/bronze). Serialized lowercase.
    #[serde(default)]
    pub quality: Option<Quality>,
    /// Playing position, e.g. "ST" (matched case-insensitively).
    #[serde(default)]
    pub position: Option<String>,
    /// Nation name, e.g. "Argentina" (matched case-insensitively).
    #[serde(default)]
    pub nation: Option<String>,
    /// League name, e.g. "Premier League" (matched case-insensitively).
    #[serde(default)]
    pub league: Option<String>,
    /// Club name, e.g. "Chelsea" (matched case-insensitively).
    #[serde(default)]
    pub club: Option<String>,
    /// Number of leading items to skip after filtering + ordering.
    #[serde(default)]
    pub offset: Option<i64>,
    /// Maximum number of items to return in the page.
    #[serde(default)]
    pub limit: Option<i64>,
}

/// One owned item projected to the attributes needed for querying, plus the
/// response body to hand back verbatim once it survives the filter+page.
pub struct OwnedItemView {
    pub owned_card_id: String,
    /// Base card overall (drives quality tier).
    pub base_overall: u8,
    /// Effective overall (base + training bonus); drives ordering.
    pub effective_overall: i64,
    pub position: String,
    pub nation: String,
    pub league: String,
    pub club: String,
    pub body: serde_json::Value,
}

impl OwnedItemView {
    fn quality(&self) -> Quality {
        Quality::from_overall(self.base_overall)
    }
}

/// Result of applying a query: the requested page plus the count of items that
/// matched the filter **before** pagination (what a client needs to page).
pub struct QueryPage {
    pub items: Vec<serde_json::Value>,
    pub total: usize,
    pub offset: usize,
    pub limit: Option<usize>,
}

/// Does an item satisfy every present filter (AND semantics)?
fn matches(item: &OwnedItemView, q: &OwnedItemQuery) -> bool {
    let quality_ok = q.quality.map(|want| item.quality() == want).unwrap_or(true);
    let pos_ok = q
        .position
        .as_ref()
        .map(|p| item.position.eq_ignore_ascii_case(p))
        .unwrap_or(true);
    let nation_ok = q
        .nation
        .as_ref()
        .map(|n| item.nation.eq_ignore_ascii_case(n))
        .unwrap_or(true);
    let league_ok = q
        .league
        .as_ref()
        .map(|l| item.league.eq_ignore_ascii_case(l))
        .unwrap_or(true);
    let club_ok = q
        .club
        .as_ref()
        .map(|c| item.club.eq_ignore_ascii_case(c))
        .unwrap_or(true);
    quality_ok && pos_ok && nation_ok && league_ok && club_ok
}

/// Apply the query: filter (AND) → deterministic order → paginate.
///
/// Ordering is `(effective_overall DESC, owned_card_id ASC)` — a total order, so
/// pages never overlap or repeat. `offset`/`limit` are clamped to sane
/// non-negative values (the wire never sends negatives; clamping keeps a
/// malformed request from panicking).
pub fn apply_query(mut items: Vec<OwnedItemView>, q: &OwnedItemQuery) -> QueryPage {
    // 1. filter
    items.retain(|it| matches(it, q));
    let total = items.len();

    // 2. deterministic total order (independent of input/DB order)
    items.sort_by(|a, b| {
        b.effective_overall
            .cmp(&a.effective_overall)
            .then_with(|| a.owned_card_id.cmp(&b.owned_card_id))
    });

    // 3. paginate
    let offset = q.offset.unwrap_or(0).max(0) as usize;
    let limit = q.limit.map(|l| l.max(0) as usize);
    let page: Vec<serde_json::Value> = items
        .into_iter()
        .skip(offset)
        .take(limit.unwrap_or(usize::MAX))
        .map(|it| it.body)
        .collect();

    QueryPage {
        items: page,
        total,
        offset,
        limit,
    }
}

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

    fn view(
        id: &str,
        overall: u8,
        position: &str,
        nation: &str,
        league: &str,
        club: &str,
    ) -> OwnedItemView {
        OwnedItemView {
            owned_card_id: id.to_string(),
            base_overall: overall,
            effective_overall: overall as i64,
            position: position.to_string(),
            nation: nation.to_string(),
            league: league.to_string(),
            club: club.to_string(),
            body: json!({ "owned_card_id": id, "overall": overall }),
        }
    }

    fn ids(page: &QueryPage) -> Vec<String> {
        page.items
            .iter()
            .map(|b| b["owned_card_id"].as_str().unwrap().to_string())
            .collect()
    }

    fn fixture() -> Vec<OwnedItemView> {
        vec![
            view("a", 84, "ST", "England", "Premier League", "Northgate"),
            view("b", 86, "CDM", "Ghana", "Premier League", "Chelsea"),
            view("c", 72, "ST", "Brazil", "Brasileirao", "Santos"),
            view("d", 60, "CM", "Italy", "Serie B", "Modena"),
            view("e", 89, "LW", "Argentina", "Primera Division", "Boca"),
        ]
    }

    #[test]
    fn no_filter_returns_all_in_overall_desc_order() {
        let p = apply_query(fixture(), &OwnedItemQuery::default());
        assert_eq!(p.total, 5);
        assert_eq!(ids(&p), ["e", "b", "a", "c", "d"]); // 89,86,84,72,60
    }

    #[test]
    fn quality_gold_selects_overall_75_plus() {
        let q = OwnedItemQuery {
            quality: Some(Quality::Gold),
            ..Default::default()
        };
        let p = apply_query(fixture(), &q);
        assert_eq!(ids(&p), ["e", "b", "a"]);
    }

    #[test]
    fn filters_are_anded() {
        let q = OwnedItemQuery {
            league: Some("Premier League".into()),
            position: Some("ST".into()),
            ..Default::default()
        };
        let p = apply_query(fixture(), &q);
        assert_eq!(ids(&p), ["a"]); // only the PL ST, not the PL CDM
    }

    #[test]
    fn case_insensitive_name_match() {
        let q = OwnedItemQuery {
            club: Some("chelsea".into()),
            ..Default::default()
        };
        let p = apply_query(fixture(), &q);
        assert_eq!(ids(&p), ["b"]);
    }

    #[test]
    fn empty_when_nothing_matches() {
        let q = OwnedItemQuery {
            nation: Some("Argentina".into()),
            club: Some("Chelsea".into()),
            ..Default::default()
        };
        let p = apply_query(fixture(), &q);
        assert_eq!(p.total, 0);
        assert!(p.items.is_empty());
    }

    #[test]
    fn filter_runs_before_pagination() {
        // Gold set is [e,b,a]; page (offset 1, limit 1) over the FILTERED set is [b].
        // If pagination ran first, offset/limit would slice the full 5-item set.
        let q = OwnedItemQuery {
            quality: Some(Quality::Gold),
            offset: Some(1),
            limit: Some(1),
            ..Default::default()
        };
        let p = apply_query(fixture(), &q);
        assert_eq!(p.total, 3, "total is the filtered count, not the page size");
        assert_eq!(ids(&p), ["b"]);
    }

    #[test]
    fn pages_do_not_overlap_and_advance() {
        let page = |off| {
            apply_query(
                fixture(),
                &OwnedItemQuery {
                    offset: Some(off),
                    limit: Some(2),
                    ..Default::default()
                },
            )
        };
        let p0 = page(0);
        let p1 = page(2);
        assert_eq!(ids(&p0), ["e", "b"]);
        assert_eq!(ids(&p1), ["a", "c"]);
        // start advancing must NOT re-serve page one
        assert_ne!(ids(&p0), ids(&p1));
        assert_eq!(p0.total, 5);
        assert_eq!(p1.total, 5);
    }

    #[test]
    fn offset_past_end_is_empty_not_wrapped() {
        let q = OwnedItemQuery {
            offset: Some(100),
            limit: Some(11),
            ..Default::default()
        };
        let p = apply_query(fixture(), &q);
        assert!(p.items.is_empty());
        assert_eq!(p.total, 5);
    }

    #[test]
    fn ordering_is_stable_on_overall_ties() {
        let items = vec![
            view("z", 80, "ST", "N", "L", "C"),
            view("a", 80, "ST", "N", "L", "C"),
            view("m", 80, "ST", "N", "L", "C"),
        ];
        let p = apply_query(items, &OwnedItemQuery::default());
        assert_eq!(ids(&p), ["a", "m", "z"]); // tie broken by owned id asc
    }
}