//! Deck synergy scoring and card suggestions.
//!
//! Given a deck, suggests cards from the whole reference database that fit its
//! strategy, with an explainable score broken into four families — **Tribal**
//! (shared creature types), **Mechanic** (shared non-evergreen keywords),
//! **Archetype** (amplifying strategy overlap via oracle-text patterns), and
//! **Mana base** (colors the deck casts but can't produce) — plus Scryfall's
//! own `edhrec_rank` as a popularity tiebreaker.
//!
//! Everything is derived from data already ingested from Scryfall's bulk files
//! (there is no runtime network access or external synergy database). Two
//! choices keep this aging well as new sets are printed:
//!
//! - **Keywords use a denylist, not an allowlist.** Scryfall's keyword array
//!   (in [`card_keywords`]) mixes true keywords (Flying) with ability words
//!   that name archetypes (Landfall, Magecraft, Convoke...). Rather than
//!   curating which keywords are archetypes — a list that must chase every new
//!   mechanic — we exclude a small stable set of generic evergreen keywords
//!   ([`EVERGREEN_KEYWORDS`]) and treat every *other* keyword the deck leans on
//!   as a synergy signal. New mechanics are covered automatically the moment
//!   their cards are ingested.
//! - **The one curated list ([`ARCHETYPES`]) matches payoffs, not actions, and
//!   only covers amplifying strategies** that were never given a keyword
//!   (Sacrifice, Tokens, Graveyard...). Matching reward phrasing ("whenever you
//!   gain life") rather than commonplace action phrasing ("gain life") keeps it
//!   discriminating; scoping it to amplifying archetypes (not universal
//!   goodstuff like removal/ramp) keeps suggestions synergistic rather than
//!   generic. These are old, stable strategies, so this list needs review
//!   roughly never.
//!
//! [`card_keywords`]: crate::db

use std::collections::{HashMap, HashSet};

use rusqlite::params;
use rusqlite::types::Value;
use serde::{Deserialize, Serialize};

use crate::db::REF_DB;
use crate::error::{CoreError, Result};
use crate::model::{CardRef, ColorSet, Legalities, WUBRG};
use crate::Catalog;

/// Curated, evergreen amplifying archetypes with no official keyword, detected
/// by payoff/enabler phrasing in oracle text. Bit position = array index,
/// packed into the `oracle_cards.themes` column at ingest. Deliberately narrow
/// and payoff-focused (see module docs): substring matching over rules text is
/// inherently fuzzy — false positives/negatives are expected and acceptable;
/// this is one signal among four, not truth.
pub const ARCHETYPES: [(&str, &[&str]); 12] = [
    ("Sacrifice", &["sacrifice a creature", "sacrifice another creature", "whenever a creature you control dies", "whenever another creature you control dies", "sacrifice a permanent"]),
    ("Graveyard", &["return target creature card from your graveyard", "from your graveyard to the battlefield", "cards in your graveyard", "creature card from your graveyard"]),
    ("Tokens", &["create a", "create two", "create three", "create x", "for each creature token", "for each token you control"]),
    ("+1/+1 Counters", &["+1/+1 counter"]),
    ("Artifacts", &["whenever an artifact", "for each artifact you control", "artifacts you control", "an artifact enters"]),
    ("Enchantments", &["whenever an enchantment", "for each enchantment you control", "enchantments you control", "an enchantment enters"]),
    ("Spellslinger", &["whenever you cast an instant or sorcery", "whenever you cast a noncreature spell", "for each instant and sorcery", "instant and sorcery cards"]),
    ("Lifegain", &["whenever you gain life", "if you gained life", "life you gained this turn", "for each 1 life"]),
    ("Extra Combat", &["additional combat phase", "an additional combat"]),
    ("Voltron", &["equipped creature", "enchanted creature you control", "whenever equipped creature", "aura you control"]),
    ("Mill", &["puts the top", "mills", "milled", "into their graveyard from the top of their library"]),
    ("Blink", &["exile it, then return it to the battlefield", "exile target creature you control, then return", "exile any number of target creatures you control"]),
];

/// Generic evergreen keywords that do NOT indicate a build-around strategy;
/// every keyword in Scryfall's array that is NOT on this list is treated as a
/// synergy signal (see module docs). Stable — the evergreen set changes rarely
/// and deliberately.
pub const EVERGREEN_KEYWORDS: [&str; 20] = [
    "Flying", "Trample", "Deathtouch", "Vigilance", "Haste", "Lifelink",
    "Menace", "Reach", "Defender", "First strike", "Double strike",
    "Hexproof", "Indestructible", "Flash", "Ward", "Protection", "Shroud",
    "Fear", "Intimidate", "Skulk",
];

/// Pack the [`ARCHETYPES`] bits a card's oracle text matches. Called at ingest
/// (keyword synergy is queried live from `card_keywords`, not baked in here, so
/// new mechanics need no re-ingest schema change).
pub fn compute_themes(oracle_text: &str) -> i64 {
    let lower = oracle_text.to_lowercase();
    let mut mask = 0i64;
    for (i, (_, phrases)) in ARCHETYPES.iter().enumerate() {
        if phrases.iter().any(|p| lower.contains(p)) {
            mask |= 1 << i;
        }
    }
    mask
}

/// One scored reason a card was suggested (e.g. `Tribal` / "Shares creature
/// type: Elf (9 in deck)").
#[derive(Debug, Clone, Serialize)]
pub struct SynergyReason {
    pub category: String,
    /// The specific thing matched — "Dragon", "Flying", "Landfall". Carried
    /// separately from `detail` so the UI can filter on it: knowing a
    /// suggestion is an Archetype hit is rarely enough, since a deck usually
    /// has several and you want one of them.
    pub subject: String,
    pub detail: String,
}

/// A suggested card with its synergy score and the reasons behind it. Unlike
/// [`crate::model::LibraryCard`]/[`crate::model::DeckEntry`], the `card` is
/// nested rather than `#[serde(flatten)]`-ed: this is a single-purpose result
/// carrying a paragraph of reasons, not a general card row reused everywhere,
/// so nesting reads cleaner.
#[derive(Debug, Clone, Serialize)]
pub struct CardSuggestion {
    pub card: CardRef,
    pub quantity_owned: i64,
    /// Copies other decks' main boards already use. Never this deck's: cards
    /// already in it aren't suggested. Lets the UI tell a spare copy from one
    /// you'd have to pull out of another deck.
    pub quantity_assigned: i64,
    pub score: f64,
    pub reasons: Vec<SynergyReason>,
    /// Scryfall's EDHREC popularity rank (lower = more common in Commander);
    /// a sort tiebreaker, not a scored category. `None` when unranked.
    pub edhrec_rank: Option<i64>,
}

// Scoring weights, ordered by reliability x synergy strength. Mana is lowest
// because it's utility/fixing, not amplifying synergy, but is kept because it
// was explicitly requested. Coarse on purpose: many candidates tie exactly,
// which lets `edhrec_rank` float the played staples of a strategy to the top.
const TRIBAL_POINTS: f64 = 4.0;
const MECHANIC_POINTS: f64 = 3.0;
const ARCHETYPE_POINTS: f64 = 2.0;
const MANA_POINTS: f64 = 1.0;
const TRIBAL_CAP: usize = 2;
const MECHANIC_CAP: usize = 2;
const ARCHETYPE_CAP: usize = 3;

/// `edhrec_rank` cutoff below which a card counts as "widely played" — kept
/// in sync with the frontend's "Popular" badge threshold (`SuggestionsModal.tsx`).
/// Used by `unusual` mode to both exclude staples from the candidate pool and
/// to invert the popularity tiebreak toward the least-played matches.
const UNUSUAL_RANK_THRESHOLD: i64 = 2000;

/// How [`Catalog::suggest_cards`] picks its candidate pool.
#[derive(Debug, Clone, Copy, Default, Deserialize)]
#[serde(default)]
pub struct SuggestOptions {
    /// Favor cards that fit but aren't widely played — see
    /// [`UNUSUAL_RANK_THRESHOLD`].
    pub unusual: bool,
    /// Only cards you own at least one copy of: build from the collection
    /// rather than a shopping list.
    pub owned_only: bool,
}

/// A candidate row pulled from the reference db before scoring.
struct Candidate {
    card: CardRef,
    themes: i64,
    edhrec_rank: Option<i64>,
    quantity_owned: i64,
}

impl Catalog {
    /// Suggest up to `limit` cards (skipping the first `offset`, for a
    /// "suggest more" continuation) that synergize with `deck_id`, scored and
    /// explained across the four synergy families. Pulls from the whole
    /// reference db (ownership is flagged via `quantity_owned`, and filtered
    /// only on request — see [`SuggestOptions`]),
    /// excludes cards already on any board of the deck, and hard-filters to the
    /// deck's (or commander's) color identity.
    ///
    /// Recomputes target signals and rescoring from scratch each call — cheap
    /// enough for an on-demand action, not a hot path — so `offset` is only a
    /// stable continuation as long as the deck's own contents haven't changed
    /// between calls (adding a suggested card mid-session removes it from the
    /// candidate pool and can shift later pages by one; acceptable for this
    /// feature's scope).
    ///
    /// When `opts.unusual` is set, candidates ranked below
    /// [`UNUSUAL_RANK_THRESHOLD`] (Scryfall's own popularity signal) or
    /// entirely unranked are favored instead of the usual "float the staples"
    /// behavior, surfacing underappreciated cards that still fit the deck's
    /// strategy. `opts.owned_only` narrows the pool to cards you own.
    pub fn suggest_cards(
        &self,
        deck_id: i64,
        limit: usize,
        offset: usize,
        opts: SuggestOptions,
    ) -> Result<Vec<CardSuggestion>> {
        let SuggestOptions { unusual, owned_only } = opts;
        // The `themes`/`edhrec_rank` columns only exist in a reference.db built
        // after this feature shipped; an older ingest lacks them. Detect that
        // and return a clear, actionable message instead of a raw "no such
        // column" error (reference.db is rebuilt, not migrated, on ingest).
        let has_synergy_columns: bool = self.conn.query_row(
            &format!("SELECT COUNT(*) FROM pragma_table_info('oracle_cards', '{REF_DB}') WHERE name = 'themes'"),
            [],
            |r| r.get::<_, i64>(0),
        )? > 0;
        if !has_synergy_columns {
            return Err(CoreError::Other(
                "Card suggestions need updated card data — click \"Update card data\" to enable them.".into(),
            ));
        }

        let Some(deck) = self.get_deck(deck_id)? else {
            return Ok(vec![]);
        };
        let contents: Vec<_> = self
            .deck_contents(deck_id)?
            .into_iter()
            .filter(|e| !e.is_maybeboard)
            .collect();
        if contents.is_empty() {
            return Ok(vec![]);
        }

        let commander_oid = deck.commander_oracle_id.clone();

        // Color identity for the hard filter: the commander's, or (no
        // commander) the union of every deck card's identity — otherwise a
        // mono-color deck would be offered all five colors.
        let identity_mask: u8 = match &commander_oid {
            Some(cmd) => contents
                .iter()
                .find(|e| &e.card.oracle_id == cmd)
                .map(|e| e.card.color_identity.0)
                .unwrap_or(0),
            None => contents.iter().fold(0u8, |m, e| m | e.card.color_identity.0),
        };

        // --- Tribal targets: dominant creature subtypes ---
        let creature_count = contents
            .iter()
            .filter(|e| e.card.type_line.contains("Creature"))
            .count();
        let tribal_threshold = std::cmp::max(3, ((creature_count as f64) * 0.15).ceil() as i64);
        let tribal_counts = self.deck_attr_counts(
            deck_id,
            "card_subtypes",
            "subtype",
            /* creatures_only = */ true,
        )?;
        let commander_subtypes = match &commander_oid {
            Some(cmd) => self.creature_subtypes_of(cmd)?,
            None => HashSet::new(),
        };
        let mut tribal_targets: HashSet<String> = tribal_counts
            .iter()
            .filter(|(_, &n)| n >= tribal_threshold)
            .map(|(s, _)| s.clone())
            .collect();
        tribal_targets.extend(commander_subtypes.iter().cloned());

        // --- Mechanic targets: non-evergreen keywords ---
        let keyword_counts = self.deck_attr_counts(deck_id, "card_keywords", "keyword", false)?;
        let commander_keywords = match &commander_oid {
            Some(cmd) => self.keywords_of(cmd)?,
            None => HashSet::new(),
        };
        let mut mechanic_targets: HashSet<String> = keyword_counts
            .iter()
            .filter(|(k, &n)| n >= 3 && !is_evergreen(k))
            .map(|(k, _)| k.clone())
            .collect();
        for k in &commander_keywords {
            if !is_evergreen(k) {
                mechanic_targets.insert(k.clone());
            }
        }

        // --- Archetype targets: theme bits on >=2 cards, or the commander's ---
        let mut theme_counts = [0i64; ARCHETYPES.len()];
        let mut archetype_mask = 0i64;
        {
            let mut stmt = self.conn.prepare(&format!(
                "SELECT oc.themes, dc.is_commander
                 FROM deck_cards dc
                 JOIN {REF_DB}.oracle_cards oc ON oc.oracle_id = dc.oracle_id
                 WHERE dc.deck_id = ?1 AND dc.is_maybeboard = 0"
            ))?;
            let rows = stmt
                .query_map(params![deck_id], |r| Ok((r.get::<_, i64>(0)?, r.get::<_, i64>(1)? != 0)))?;
            for row in rows {
                let (themes, is_cmd) = row?;
                for (i, c) in theme_counts.iter_mut().enumerate() {
                    if themes & (1 << i) != 0 {
                        *c += 1;
                    }
                }
                if is_cmd {
                    archetype_mask |= themes;
                }
            }
        }
        for (i, &c) in theme_counts.iter().enumerate() {
            if c >= 2 {
                archetype_mask |= 1 << i;
            }
        }

        // --- Mana-base targets: colors cast but not produced ---
        let mut production = [0i64; 5];
        let mut consumption = [0i64; 5];
        for e in contents.iter().filter(|e| !e.is_commander) {
            let q = e.quantity;
            for (i, (bit, _)) in WUBRG.iter().enumerate() {
                if e.card.produced_mana.0 & *bit != 0 {
                    production[i] += q;
                }
            }
            if !e.card.type_line.contains("Land") {
                for (i, (bit, _)) in WUBRG.iter().enumerate() {
                    if e.card.colors.0 & *bit != 0 {
                        consumption[i] += q;
                    }
                }
            }
        }
        let mut mana_mask = 0u8;
        for (i, (bit, _)) in WUBRG.iter().enumerate() {
            if consumption[i] > 0 && production[i] == 0 {
                mana_mask |= *bit;
            }
        }

        if tribal_targets.is_empty()
            && mechanic_targets.is_empty()
            && archetype_mask == 0
            && mana_mask == 0
        {
            return Ok(vec![]);
        }

        // --- Candidate query (dynamic, mirroring filters.rs::search_library) ---
        let mut sql = format!(
            "SELECT oc.oracle_id, oc.name, oc.mana_value, oc.colors, oc.color_identity, oc.type_line,
                    {image}, {back}, oc.produced_mana, oc.produces_colorless, oc.legalities, {price},
                    oc.themes, oc.edhrec_rank, COALESCE(lc.quantity_owned, 0), {horizontal}
             FROM {REF_DB}.oracle_cards oc
             LEFT JOIN library_cards lc ON lc.oracle_id = oc.oracle_id
             WHERE oc.oracle_id NOT IN (SELECT oracle_id FROM deck_cards WHERE deck_id = ?)
               AND (oc.color_identity & ?) = 0
               AND (",
            image = self.image_expr("image_uri"),
            back = self.image_expr("back_image_uri"),
            price = crate::db::price_subquery(),
            horizontal = self.horizontal_col(),
        );
        let mut vals: Vec<Value> = vec![
            Value::Integer(deck_id),
            Value::Integer((!identity_mask & 0b11111) as i64),
        ];
        let mut branches: Vec<String> = Vec::new();
        if !tribal_targets.is_empty() {
            let ph = placeholders(tribal_targets.len());
            branches.push(format!(
                "EXISTS (SELECT 1 FROM {REF_DB}.card_subtypes cs WHERE cs.oracle_id = oc.oracle_id AND cs.subtype IN ({ph}))"
            ));
            vals.extend(tribal_targets.iter().map(|s| Value::Text(s.clone())));
        }
        if !mechanic_targets.is_empty() {
            let ph = placeholders(mechanic_targets.len());
            branches.push(format!(
                "EXISTS (SELECT 1 FROM {REF_DB}.card_keywords ck WHERE ck.oracle_id = oc.oracle_id AND ck.keyword IN ({ph}))"
            ));
            vals.extend(mechanic_targets.iter().map(|k| Value::Text(k.clone())));
        }
        if archetype_mask != 0 {
            branches.push("(oc.themes & ?) != 0".into());
            vals.push(Value::Integer(archetype_mask));
        }
        if mana_mask != 0 {
            branches.push("(oc.produced_mana & ?) != 0".into());
            vals.push(Value::Integer(mana_mask as i64));
        }
        sql.push_str(&branches.join(" OR "));
        sql.push(')');
        if unusual {
            sql.push_str(" AND (oc.edhrec_rank IS NULL OR oc.edhrec_rank >= ?)");
            vals.push(Value::Integer(UNUSUAL_RANK_THRESHOLD));
        }
        if owned_only {
            // Filtered before scoring and paging, so "Suggest more" keeps
            // finding owned cards instead of pages thinning out to nothing.
            sql.push_str(" AND COALESCE(lc.quantity_owned, 0) > 0");
        }

        let candidates: Vec<Candidate> = {
            let mut stmt = self.conn.prepare(&sql)?;
            let rows = stmt.query_map(rusqlite::params_from_iter(vals), |r| {
                Ok(Candidate {
                    card: CardRef {
                        oracle_id: r.get(0)?,
                        name: r.get(1)?,
                        mana_value: r.get(2)?,
                        colors: ColorSet(r.get::<_, i64>(3)? as u8),
                        color_identity: ColorSet(r.get::<_, i64>(4)? as u8),
                        type_line: r.get(5)?,
                        image_uri: r.get::<_, Option<String>>(6)?.unwrap_or_default(),
                        back_image_uri: r.get::<_, Option<String>>(7)?.unwrap_or_default(),
                        produced_mana: ColorSet(r.get::<_, i64>(8)? as u8),
                        produces_colorless: r.get::<_, i64>(9)? != 0,
                        legalities: Legalities(r.get::<_, i64>(10)?),
                        price_usd: r.get::<_, Option<f64>>(11)?.unwrap_or_default(),
                        horizontal: r.get::<_, i64>(15)? != 0,
                    },
                    themes: r.get(12)?,
                    edhrec_rank: r.get(13)?,
                    quantity_owned: r.get(14)?,
                })
            })?;
            rows.collect::<std::result::Result<Vec<_>, _>>()?
        };

        // Batch-load each candidate's subtypes/keywords (avoids per-card N+1).
        let cand_ids: Vec<String> = candidates.iter().map(|c| c.card.oracle_id.clone()).collect();
        let sub_map = self.batch_attr(&cand_ids, "card_subtypes", "subtype")?;
        let kw_map = self.batch_attr(&cand_ids, "card_keywords", "keyword")?;
        let assigned = self.assigned_totals_by_oracle()?;
        let empty: Vec<String> = Vec::new();

        let mut out: Vec<CardSuggestion> = Vec::new();
        for cand in candidates {
            let oid = &cand.card.oracle_id;
            let mut score = 0.0;
            let mut reasons = Vec::new();

            // Tribal
            let mut tribal_hits: Vec<&String> = sub_map
                .get(oid)
                .unwrap_or(&empty)
                .iter()
                .filter(|s| tribal_targets.contains(*s))
                .collect();
            tribal_hits.sort();
            for s in tribal_hits.into_iter().take(TRIBAL_CAP) {
                score += TRIBAL_POINTS;
                let detail = if commander_subtypes.contains(s) {
                    format!("Matches your commander's type: {s}")
                } else {
                    let n = tribal_counts.get(s).copied().unwrap_or(0);
                    format!("Shares creature type: {s} ({n} in deck)")
                };
                reasons.push(SynergyReason {
                    category: "Tribal".into(),
                    subject: s.clone(),
                    detail,
                });
            }

            // Mechanic
            let mut mech_hits: Vec<&String> = kw_map
                .get(oid)
                .unwrap_or(&empty)
                .iter()
                .filter(|k| mechanic_targets.contains(*k))
                .collect();
            mech_hits.sort();
            for k in mech_hits.into_iter().take(MECHANIC_CAP) {
                score += MECHANIC_POINTS;
                let detail = if commander_keywords.contains(k) {
                    format!("Matches your commander's keyword: {k}")
                } else {
                    let n = keyword_counts.get(k).copied().unwrap_or(0);
                    format!("Shares keyword: {k} ({n} in deck)")
                };
                reasons.push(SynergyReason {
                    category: "Mechanic".into(),
                    subject: k.clone(),
                    detail,
                });
            }

            // Archetype
            let matched = cand.themes & archetype_mask;
            let mut arche = 0;
            for (i, (name, _)) in ARCHETYPES.iter().enumerate() {
                if arche >= ARCHETYPE_CAP {
                    break;
                }
                if matched & (1 << i) != 0 {
                    score += ARCHETYPE_POINTS;
                    reasons.push(SynergyReason {
                        category: "Archetype".into(),
                        subject: (*name).to_string(),
                        detail: format!("{name} payoff/enabler"),
                    });
                    arche += 1;
                }
            }

            // Mana base
            let mana_hit = cand.card.produced_mana.0 & mana_mask;
            if mana_hit != 0 {
                score += MANA_POINTS;
                let letters: String = WUBRG
                    .iter()
                    .filter(|(bit, _)| mana_hit & bit != 0)
                    .map(|(_, c)| format!("{{{c}}}"))
                    .collect();
                reasons.push(SynergyReason {
                    category: "Mana base".into(),
                    subject: letters.clone(),
                    detail: format!("Produces {letters}, which your deck can't currently make"),
                });
            }

            if score <= 0.0 {
                continue;
            }
            out.push(CardSuggestion {
                quantity_assigned: assigned.get(oid).copied().unwrap_or(0),
                card: cand.card,
                quantity_owned: cand.quantity_owned,
                score,
                reasons,
                edhrec_rank: cand.edhrec_rank,
            });
        }

        out.sort_by(|a, b| {
            b.score
                .partial_cmp(&a.score)
                .unwrap_or(std::cmp::Ordering::Equal)
                .then_with(|| rank_key(a.edhrec_rank, unusual).cmp(&rank_key(b.edhrec_rank, unusual)))
                .then_with(|| a.card.name.to_lowercase().cmp(&b.card.name.to_lowercase()))
        });
        let out = out.into_iter().skip(offset).take(limit).collect();
        Ok(out)
    }

    /// Count, per attribute value, how many of a deck's non-maybeboard cards
    /// have it. `table`/`column` are fixed call-site literals (safe to
    /// interpolate). `creatures_only` restricts to cards whose type line is a
    /// creature (for tribal subtypes — keeps land/artifact subtypes out).
    fn deck_attr_counts(
        &self,
        deck_id: i64,
        table: &str,
        column: &str,
        creatures_only: bool,
    ) -> Result<HashMap<String, i64>> {
        let creature_filter = if creatures_only {
            "AND oc.type_line LIKE '%Creature%'"
        } else {
            ""
        };
        let mut stmt = self.conn.prepare(&format!(
            "SELECT x.{column}, COUNT(DISTINCT dc.oracle_id) AS n
             FROM deck_cards dc
             JOIN {REF_DB}.oracle_cards oc ON oc.oracle_id = dc.oracle_id
             JOIN {REF_DB}.{table} x ON x.oracle_id = dc.oracle_id
             WHERE dc.deck_id = ?1 AND dc.is_maybeboard = 0 {creature_filter}
             GROUP BY x.{column}"
        ))?;
        let rows = stmt.query_map(params![deck_id], |r| Ok((r.get::<_, String>(0)?, r.get::<_, i64>(1)?)))?;
        let mut map = HashMap::new();
        for row in rows {
            let (k, n) = row?;
            map.insert(k, n);
        }
        Ok(map)
    }

    fn creature_subtypes_of(&self, oracle_id: &str) -> Result<HashSet<String>> {
        let mut stmt = self.conn.prepare(&format!(
            "SELECT cs.subtype FROM {REF_DB}.card_subtypes cs
             JOIN {REF_DB}.oracle_cards oc ON oc.oracle_id = cs.oracle_id
             WHERE cs.oracle_id = ?1 AND oc.type_line LIKE '%Creature%'"
        ))?;
        let rows = stmt.query_map(params![oracle_id], |r| r.get::<_, String>(0))?;
        Ok(rows.collect::<std::result::Result<HashSet<_>, _>>()?)
    }

    fn keywords_of(&self, oracle_id: &str) -> Result<HashSet<String>> {
        let mut stmt = self
            .conn
            .prepare(&format!("SELECT keyword FROM {REF_DB}.card_keywords WHERE oracle_id = ?1"))?;
        let rows = stmt.query_map(params![oracle_id], |r| r.get::<_, String>(0))?;
        Ok(rows.collect::<std::result::Result<HashSet<_>, _>>()?)
    }

    /// Load an attribute (`subtype`/`keyword`) for many oracle_ids at once,
    /// chunked under SQLite's bound-variable limit.
    fn batch_attr(
        &self,
        ids: &[String],
        table: &str,
        column: &str,
    ) -> Result<HashMap<String, Vec<String>>> {
        let mut map: HashMap<String, Vec<String>> = HashMap::new();
        for chunk in ids.chunks(900) {
            let ph = placeholders(chunk.len());
            let mut stmt = self.conn.prepare(&format!(
                "SELECT oracle_id, {column} FROM {REF_DB}.{table} WHERE oracle_id IN ({ph})"
            ))?;
            let vals: Vec<Value> = chunk.iter().map(|s| Value::Text(s.clone())).collect();
            let rows = stmt.query_map(rusqlite::params_from_iter(vals), |r| {
                Ok((r.get::<_, String>(0)?, r.get::<_, String>(1)?))
            })?;
            for row in rows {
                let (oid, v) = row?;
                map.entry(oid).or_default().push(v);
            }
        }
        Ok(map)
    }
}

fn is_evergreen(keyword: &str) -> bool {
    EVERGREEN_KEYWORDS.iter().any(|e| e.eq_ignore_ascii_case(keyword))
}

fn placeholders(n: usize) -> String {
    std::iter::repeat("?").take(n).collect::<Vec<_>>().join(",")
}

/// Sort key for the edhrec_rank tiebreak. Normally pushes unranked cards
/// (`None`) to the end, so within a tied score the played staples float up.
/// In `unusual` mode this is inverted — unranked cards sort first, followed
/// by the highest (least popular) ranks — so the least-played matches float
/// up instead, which is the entire point of that mode.
fn rank_key(rank: Option<i64>, unusual: bool) -> i64 {
    if unusual {
        rank.map(|r| -r).unwrap_or(i64::MIN)
    } else {
        rank.unwrap_or(i64::MAX)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::model::ColorSet;
    use crate::test_support;

    /// Raw-insert an extra reference card (the shared fixture doesn't cover
    /// themes/edhrec_rank/produced_mana). Mirrors library.rs's raw-SQL test
    /// style; keeps `test_support` untouched.
    #[allow(clippy::too_many_arguments)]
    fn add_ref_card(
        cat: &Catalog,
        oid: &str,
        name: &str,
        type_line: &str,
        identity: &str,
        produced: &str,
        subtypes: &[&str],
        keywords: &[&str],
        themes: i64,
        rank: Option<i64>,
    ) {
        let conn = cat.connection();
        conn.execute(
            "INSERT INTO ref.oracle_cards
             (oracle_id,name,name_lower,type_line,colors,color_identity,produced_mana,themes,edhrec_rank)
             VALUES (?1,?2,?3,?4,?5,?6,?7,?8,?9)",
            params![
                oid,
                name,
                name.to_lowercase(),
                type_line,
                ColorSet::parse(identity).0 as i64,
                ColorSet::parse(identity).0 as i64,
                ColorSet::parse(produced).0 as i64,
                themes,
                rank,
            ],
        )
        .unwrap();
        conn.execute(
            "INSERT INTO ref.printings(scryfall_id,oracle_id,image_uri) VALUES (?1,?2,?3)",
            params![format!("p-{oid}"), oid, format!("http://img/{oid}")],
        )
        .unwrap();
        for s in subtypes {
            conn.execute(
                "INSERT INTO ref.card_subtypes(oracle_id,subtype) VALUES (?1,?2)",
                params![oid, s],
            )
            .unwrap();
        }
        for k in keywords {
            conn.execute(
                "INSERT INTO ref.card_keywords(oracle_id,keyword) VALUES (?1,?2)",
                params![oid, k],
            )
            .unwrap();
        }
    }

    #[test]
    fn compute_themes_matches_payoff_phrasing_not_actions() {
        // Sacrifice payoff phrasing sets its bit.
        let m = compute_themes("Whenever a creature you control dies, draw a card.");
        assert_ne!(m & 1, 0); // Sacrifice is bit 0
                              // Plain "gain life" must NOT trip the Lifegain bit (payoff phrasing only).
        let lifegain_bit = 1 << ARCHETYPES.iter().position(|(n, _)| *n == "Lifegain").unwrap();
        assert_eq!(compute_themes("You gain 3 life.") & lifegain_bit, 0);
        assert_ne!(compute_themes("Whenever you gain life, put a +1/+1 counter.") & lifegain_bit, 0);
        // Vanilla text sets nothing.
        assert_eq!(compute_themes("Flying, vigilance"), 0);
    }

    #[test]
    fn tribal_suggestion_with_reasons_excludes_deck_cards_and_breaks_ties_by_rank() {
        let fx = test_support::make();
        let cat = &fx.catalog;
        // Three Elf creatures in the deck (fixture has two Elves; add a third).
        add_ref_card(cat, "elf-c", "Elf Cleric", "Creature — Elf Cleric", "G", "", &["Elf"], &[], 0, None);
        // Two unowned Elf candidates with different popularity.
        add_ref_card(cat, "elf-lord", "Elf Lord", "Creature — Elf", "G", "", &["Elf"], &[], 0, Some(5));
        add_ref_card(cat, "elf-rare", "Obscure Elf", "Creature — Elf", "G", "", &["Elf"], &[], 0, Some(9000));

        let d = cat.create_deck("Elfball", None).unwrap();
        cat.set_deck_card(d.id, "llanowar-elves", 1, false, false).unwrap();
        cat.set_deck_card(d.id, "deathrite-shaman", 1, false, false).unwrap();
        cat.set_deck_card(d.id, "elf-c", 1, false, false).unwrap();

        let out = cat.suggest_cards(d.id, 50, 0, SuggestOptions::default()).unwrap();
        let ids: Vec<&str> = out.iter().map(|s| s.card.oracle_id.as_str()).collect();

        // Both Elf candidates appear with a Tribal reason mentioning Elf.
        assert!(ids.contains(&"elf-lord"));
        assert!(ids.contains(&"elf-rare"));
        let lord = out.iter().find(|s| s.card.oracle_id == "elf-lord").unwrap();
        assert!(lord.reasons.iter().any(|r| r.category == "Tribal" && r.detail.contains("Elf")));
        // Cards already in the deck are never suggested.
        assert!(!ids.contains(&"llanowar-elves"));
        assert!(!ids.contains(&"deathrite-shaman"));
        // Equal score → the lower edhrec_rank sorts first.
        let li = ids.iter().position(|x| *x == "elf-lord").unwrap();
        let ri = ids.iter().position(|x| *x == "elf-rare").unwrap();
        assert!(li < ri);

        // `unusual` mode excludes the widely-played candidate entirely and
        // keeps the obscure one.
        add_ref_card(cat, "elf-unranked", "Unranked Elf", "Creature — Elf", "G", "", &["Elf"], &[], 0, None);
        let out = cat.suggest_cards(d.id, 50, 0, SuggestOptions { unusual: true, ..Default::default() }).unwrap();
        let ids: Vec<&str> = out.iter().map(|s| s.card.oracle_id.as_str()).collect();
        assert!(!ids.contains(&"elf-lord"), "rank 5 is well below the unusual threshold");
        assert!(ids.contains(&"elf-rare"));
        assert!(ids.contains(&"elf-unranked"));
        // Equal score → the tiebreak flips toward the least popular first.
        let ui = ids.iter().position(|x| *x == "elf-unranked").unwrap();
        let ri = ids.iter().position(|x| *x == "elf-rare").unwrap();
        assert!(ui < ri, "unranked should float above a merely-obscure ranked card");
    }

    #[test]
    fn small_tribal_splash_does_not_trigger_tribe() {
        let fx = test_support::make();
        let cat = &fx.catalog;
        // A deck with just the two fixture Elves plus many non-Elf creatures,
        // so Elf (2) is below the proportional threshold.
        let d = cat.create_deck("Goodstuff", None).unwrap();
        cat.set_deck_card(d.id, "llanowar-elves", 1, false, false).unwrap();
        cat.set_deck_card(d.id, "deathrite-shaman", 1, false, false).unwrap();
        for i in 0..10 {
            let oid = format!("beast-{i}");
            add_ref_card(cat, &oid, &format!("Beast {i}"), "Creature", "G", "", &[], &[], 0, None);
            cat.set_deck_card(d.id, &oid, 1, false, false).unwrap();
        }
        // An Elf candidate whose only possible signal is tribal.
        add_ref_card(cat, "lone-elf", "Lone Elf", "Creature — Elf", "G", "", &["Elf"], &[], 0, None);

        let out = cat.suggest_cards(d.id, 50, 0, SuggestOptions::default()).unwrap();
        assert!(!out.iter().any(|s| s.card.oracle_id == "lone-elf"));
    }

    #[test]
    fn mechanic_uses_denylist_evergreen_excluded_others_included() {
        let fx = test_support::make();
        let cat = &fx.catalog;
        let d = cat.create_deck("Landfall", None).unwrap();
        // Three deck creatures with both Landfall (mechanic) and Flying (evergreen).
        for i in 0..3 {
            let oid = format!("land-guy-{i}");
            add_ref_card(cat, &oid, &format!("Land Guy {i}"), "Creature — Elemental", "G", "", &[], &["Landfall", "Flying"], 0, None);
            cat.set_deck_card(d.id, &oid, 1, false, false).unwrap();
        }
        add_ref_card(cat, "landfall-payoff", "Landfall Payoff", "Creature — Elemental", "G", "", &[], &["Landfall"], 0, None);
        add_ref_card(cat, "just-a-flyer", "Just A Flyer", "Creature — Bird", "G", "", &[], &["Flying"], 0, None);

        let out = cat.suggest_cards(d.id, 50, 0, SuggestOptions::default()).unwrap();
        let payoff = out.iter().find(|s| s.card.oracle_id == "landfall-payoff");
        assert!(payoff.is_some(), "non-evergreen keyword should drive suggestions");
        assert!(payoff.unwrap().reasons.iter().any(|r| r.category == "Mechanic" && r.detail.contains("Landfall")));
        // Flying alone (evergreen) is not a synergy signal.
        assert!(!out.iter().any(|s| s.card.oracle_id == "just-a-flyer"));
    }

    #[test]
    fn commander_type_is_always_a_target_and_off_color_is_excluded() {
        let fx = test_support::make();
        let cat = &fx.catalog;
        // Mono-green Elf commander, single card in the deck.
        let d = cat.create_deck("Commander Elf", Some("llanowar-elves")).unwrap();
        cat.set_deck_card(d.id, "llanowar-elves", 1, true, false).unwrap();
        cat.set_deck_commander(d.id, Some("llanowar-elves")).unwrap();

        add_ref_card(cat, "green-elf", "Green Elf", "Creature — Elf", "G", "", &["Elf"], &[], 0, None);
        add_ref_card(cat, "black-elf", "Black Elf", "Creature — Elf", "B", "", &["Elf"], &[], 0, None);

        let out = cat.suggest_cards(d.id, 50, 0, SuggestOptions::default()).unwrap();
        let green = out.iter().find(|s| s.card.oracle_id == "green-elf");
        assert!(green.is_some(), "commander's own type should be a tribal target");
        assert!(green.unwrap().reasons.iter().any(|r| r.detail.contains("commander's type")));
        // Off-color-identity candidate is hard-excluded.
        assert!(!out.iter().any(|s| s.card.oracle_id == "black-elf"));
    }

    #[test]
    fn mana_base_fit_flags_a_missing_color() {
        let fx = test_support::make();
        let cat = &fx.catalog;
        // Deathrite Shaman casts B and G but the deck produces neither.
        let d = cat.create_deck("BG", None).unwrap();
        cat.set_deck_card(d.id, "deathrite-shaman", 1, false, false).unwrap();
        add_ref_card(cat, "swamp-dork", "Swamp Dork", "Creature — Elf", "B", "B", &["Elf"], &[], 0, None);

        let out = cat.suggest_cards(d.id, 50, 0, SuggestOptions::default()).unwrap();
        let dork = out.iter().find(|s| s.card.oracle_id == "swamp-dork").unwrap();
        assert!(dork.reasons.iter().any(|r| r.category == "Mana base" && r.detail.contains("{B}")));
    }

    #[test]
    fn empty_deck_returns_no_suggestions() {
        let fx = test_support::make();
        let cat = &fx.catalog;
        let d = cat.create_deck("Empty", None).unwrap();
        assert!(cat.suggest_cards(d.id, 50, 0, SuggestOptions::default()).unwrap().is_empty());
    }

    #[test]
    fn owned_only_keeps_your_cards_and_reports_copies_other_decks_use() {
        let fx = test_support::make();
        let cat = &fx.catalog;
        add_ref_card(cat, "elf-c", "Elf Cleric", "Creature — Elf Cleric", "G", "", &["Elf"], &[], 0, None);
        add_ref_card(cat, "owned-elf", "Owned Elf", "Creature — Elf", "G", "", &["Elf"], &[], 0, None);
        add_ref_card(cat, "shop-elf", "Shop Elf", "Creature — Elf", "G", "", &["Elf"], &[], 0, None);
        let d = cat.create_deck("Elfball", None).unwrap();
        for oid in ["llanowar-elves", "deathrite-shaman", "elf-c"] {
            cat.set_deck_card(d.id, oid, 1, false, false).unwrap();
        }
        cat.add_owned("owned-elf", 2).unwrap();
        let other = cat.create_deck("Other", None).unwrap();
        cat.set_deck_card(other.id, "owned-elf", 1, false, false).unwrap();

        let all = cat.suggest_cards(d.id, 50, 0, SuggestOptions::default()).unwrap();
        assert!(all.iter().any(|s| s.card.oracle_id == "shop-elf"));

        let owned = cat
            .suggest_cards(d.id, 50, 0, SuggestOptions { owned_only: true, ..Default::default() })
            .unwrap();
        let ids: Vec<&str> = owned.iter().map(|s| s.card.oracle_id.as_str()).collect();
        assert_eq!(ids, vec!["owned-elf"]);
        assert_eq!(owned[0].quantity_owned, 2);
        assert_eq!(owned[0].quantity_assigned, 1, "one copy is already in the other deck");
    }

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

    #[test]
    fn a_reason_names_the_specific_thing_it_matched() {
        // The subject is what the UI filters on, so it must be the bare
        // "Dragon"/"Landfall" rather than the sentence shown to the user —
        // otherwise picking one archetype would mean matching prose.
        let r = SynergyReason {
            category: "Archetype".into(),
            subject: "Landfall".into(),
            detail: "Landfall payoff/enabler".into(),
        };
        assert_eq!(r.subject, "Landfall");
        assert!(r.detail.contains(&r.subject), "detail should still read naturally");
    }
}
}