package storage

import (
	"context"
	"errors"
	"fmt"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"

	"github.com/denisovdennis/autohero/internal/model"
)

// ErrInventoryFull is returned when the backpack already holds MaxInventorySlots items.
var ErrInventoryFull = errors.New("inventory full")

// GearStore handles all gear CRUD operations against PostgreSQL.
type GearStore struct {
	pool *pgxpool.Pool
}

type gearOverrideRow struct {
	FormID        *string
	Name          *string
	Subtype       *string
	Rarity        *string
	Ilvl          *int
	BasePrimary   *int
	PrimaryStat   *int
	StatType      *string
	SpeedModifier *float64
	CritChance    *float64
	AgilityBonus  *int
	SetName       *string
	SpecialEffect *string
}

// NewGearStore creates a new GearStore backed by the given connection pool.
func NewGearStore(pool *pgxpool.Pool) *GearStore {
	return &GearStore{pool: pool}
}

func overrideRowFromItem(item *model.GearItem) gearOverrideRow {
	if item == nil {
		return gearOverrideRow{}
	}
	return gearOverrideRow{
		FormID:        &item.FormID,
		Name:          &item.Name,
		Subtype:       &item.Subtype,
		Rarity:        ptrString(string(item.Rarity)),
		Ilvl:          &item.Ilvl,
		BasePrimary:   &item.BasePrimary,
		PrimaryStat:   &item.PrimaryStat,
		StatType:      &item.StatType,
		SpeedModifier: &item.SpeedModifier,
		CritChance:    &item.CritChance,
		AgilityBonus:  &item.AgilityBonus,
		SetName:       &item.SetName,
		SpecialEffect: &item.SpecialEffect,
	}
}

func (s *GearStore) resolveArchetypeID(ctx context.Context, item *model.GearItem) (int64, error) {
	if item == nil {
		return 0, fmt.Errorf("nil gear item")
	}
	var id int64
	err := s.pool.QueryRow(ctx, `
		SELECT id FROM gear
		WHERE slot = $1 AND name = $2 AND form_id = $3 AND subtype = $4
		ORDER BY id ASC LIMIT 1
	`, string(item.Slot), item.Name, item.FormID, item.Subtype).Scan(&id)
	if err == nil {
		return id, nil
	}
	if !errors.Is(err, pgx.ErrNoRows) {
		return 0, fmt.Errorf("resolve archetype: %w", err)
	}
	err = s.pool.QueryRow(ctx, `
		SELECT id FROM gear
		WHERE slot = $1 AND name = $2
		ORDER BY id ASC LIMIT 1
	`, string(item.Slot), item.Name).Scan(&id)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return 0, fmt.Errorf("gear archetype not found for %s/%s", item.Name, item.Subtype)
		}
		return 0, fmt.Errorf("resolve archetype fallback: %w", err)
	}
	return id, nil
}

// CreateItem inserts a new gear item into the database and populates item.ID.
func (s *GearStore) CreateItem(ctx context.Context, item *model.GearItem) error {
	err := s.pool.QueryRow(ctx, `
		INSERT INTO gear (slot, form_id, name, subtype, rarity, ilvl, base_primary, primary_stat,
		                   stat_type, speed_modifier, crit_chance, agility_bonus, set_name, special_effect)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14)
		RETURNING id
	`,
		string(item.Slot), item.FormID, item.Name, item.Subtype,
		string(item.Rarity), item.Ilvl, item.BasePrimary, item.PrimaryStat,
		item.StatType, item.SpeedModifier, item.CritChance, item.AgilityBonus,
		item.SetName, item.SpecialEffect,
	).Scan(&item.ID)
	if err != nil {
		return fmt.Errorf("create gear item: %w", err)
	}
	return nil
}

// UpdateItem updates an existing row in `gear` by id (all columns except created_at).
func (s *GearStore) UpdateItem(ctx context.Context, item *model.GearItem) error {
	if item == nil || item.ID <= 0 {
		return fmt.Errorf("invalid gear id")
	}
	cmd, err := s.pool.Exec(ctx, `
		UPDATE gear SET
			slot = $2, form_id = $3, name = $4, subtype = $5, rarity = $6, ilvl = $7,
			base_primary = $8, primary_stat = $9, stat_type = $10,
			speed_modifier = $11, crit_chance = $12, agility_bonus = $13, set_name = $14, special_effect = $15
		WHERE id = $1
	`,
		item.ID, string(item.Slot), item.FormID, item.Name, item.Subtype,
		string(item.Rarity), item.Ilvl, item.BasePrimary, item.PrimaryStat,
		item.StatType, item.SpeedModifier, item.CritChance, item.AgilityBonus,
		item.SetName, item.SpecialEffect,
	)
	if err != nil {
		return fmt.Errorf("update gear: %w", err)
	}
	if cmd.RowsAffected() == 0 {
		return fmt.Errorf("gear not found: %d", item.ID)
	}
	return nil
}

// GetItem loads a single gear item by ID. Returns (nil, nil) if not found.
func (s *GearStore) GetItem(ctx context.Context, id int64) (*model.GearItem, error) {
	var item model.GearItem
	var slot, rarity string
	err := s.pool.QueryRow(ctx, `
		SELECT id, slot, form_id, name, subtype, rarity, ilvl,
		       base_primary, primary_stat, stat_type,
		       speed_modifier, crit_chance, agility_bonus,
		       set_name, special_effect
		FROM gear WHERE id = $1
	`, id).Scan(
		&item.ID, &slot, &item.FormID, &item.Name, &item.Subtype,
		&rarity, &item.Ilvl,
		&item.BasePrimary, &item.PrimaryStat, &item.StatType,
		&item.SpeedModifier, &item.CritChance, &item.AgilityBonus,
		&item.SetName, &item.SpecialEffect,
	)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, nil
		}
		return nil, fmt.Errorf("get gear item: %w", err)
	}
	item.Slot = model.EquipmentSlot(slot)
	item.Rarity = model.Rarity(rarity)
	return &item, nil
}

// GetHeroGear returns all equipped gear for a hero, keyed by slot.
func (s *GearStore) GetHeroGear(ctx context.Context, heroID int64) (map[model.EquipmentSlot]*model.GearItem, error) {
	rows, err := s.pool.Query(ctx, `
		SELECT hg.item_id, hg.slot,
		       COALESCE(hg.form_id, g.form_id),
		       COALESCE(hg.name, g.name),
		       COALESCE(hg.subtype, g.subtype),
		       COALESCE(hg.rarity, g.rarity),
		       COALESCE(hg.ilvl, g.ilvl),
		       COALESCE(hg.base_primary, g.base_primary),
		       COALESCE(hg.primary_stat, g.primary_stat),
		       COALESCE(hg.stat_type, g.stat_type),
		       COALESCE(hg.speed_modifier, g.speed_modifier),
		       COALESCE(hg.crit_chance, g.crit_chance),
		       COALESCE(hg.agility_bonus, g.agility_bonus),
		       COALESCE(hg.set_name, g.set_name),
		       COALESCE(hg.special_effect, g.special_effect)
		FROM hero_gear hg
		JOIN gear g ON hg.gear_id = g.id
		WHERE hg.hero_id = $1
	`, heroID)
	if err != nil {
		return nil, fmt.Errorf("get hero gear: %w", err)
	}
	defer rows.Close()

	gear := make(map[model.EquipmentSlot]*model.GearItem)
	for rows.Next() {
		var item model.GearItem
		var slot, rarity string
		if err := rows.Scan(
			&item.ID, &slot, &item.FormID, &item.Name, &item.Subtype,
			&rarity, &item.Ilvl,
			&item.BasePrimary, &item.PrimaryStat, &item.StatType,
			&item.SpeedModifier, &item.CritChance, &item.AgilityBonus,
			&item.SetName, &item.SpecialEffect,
		); err != nil {
			return nil, fmt.Errorf("scan gear item: %w", err)
		}
		item.Slot = model.EquipmentSlot(slot)
		item.Rarity = model.Rarity(rarity)
		gear[item.Slot] = &item
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("hero gear rows: %w", err)
	}
	return gear, nil
}

// EquipItem equips a newly created item (not yet in inventory) into the given slot.
// Any previously equipped item is moved to the backpack.
// Returns ErrInventoryFull if the previous item cannot be stashed.
func (s *GearStore) EquipItem(ctx context.Context, heroID int64, item *model.GearItem) error {
	if item == nil {
		return fmt.Errorf("nil gear item")
	}
	gearID, err := s.resolveArchetypeID(ctx, item)
	if err != nil {
		return err
	}
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return fmt.Errorf("equip gear item begin: %w", err)
	}
	defer tx.Rollback(ctx)

	var (
		prevGearID    int64
		prevItemID    int64
		prevOverrides gearOverrideRow
	)
	err = tx.QueryRow(ctx, `
		SELECT gear_id, item_id, form_id, name, subtype, rarity, ilvl, base_primary, primary_stat,
		       stat_type, speed_modifier, crit_chance, agility_bonus, set_name, special_effect
		FROM hero_gear
		WHERE hero_id = $1 AND slot = $2
	`, heroID, string(item.Slot)).Scan(
		&prevGearID, &prevItemID,
		&prevOverrides.FormID, &prevOverrides.Name, &prevOverrides.Subtype, &prevOverrides.Rarity,
		&prevOverrides.Ilvl, &prevOverrides.BasePrimary, &prevOverrides.PrimaryStat,
		&prevOverrides.StatType, &prevOverrides.SpeedModifier, &prevOverrides.CritChance, &prevOverrides.AgilityBonus,
		&prevOverrides.SetName, &prevOverrides.SpecialEffect,
	)
	hasPrev := true
	if errors.Is(err, pgx.ErrNoRows) {
		hasPrev = false
		err = nil
	} else if err != nil {
		return fmt.Errorf("equip read previous: %w", err)
	}
	if hasPrev {
		count, err := inventoryCountTx(ctx, tx, heroID)
		if err != nil {
			return err
		}
		if count >= model.MaxInventorySlots {
			return ErrInventoryFull
		}
	}

	overrides := overrideRowFromItem(item)
	err = tx.QueryRow(ctx, `
		INSERT INTO hero_gear (
			hero_id, slot, gear_id, item_id,
			form_id, name, subtype, rarity, ilvl, base_primary, primary_stat, stat_type,
			speed_modifier, crit_chance, agility_bonus, set_name, special_effect
		) VALUES (
			$1, $2, $3, nextval('public.hero_item_id_seq'),
			$4, $5, $6, $7, $8, $9, $10, $11,
			$12, $13, $14, $15, $16
		)
		ON CONFLICT (hero_id, slot) DO UPDATE SET
			gear_id = EXCLUDED.gear_id,
			item_id = EXCLUDED.item_id,
			form_id = EXCLUDED.form_id,
			name = EXCLUDED.name,
			subtype = EXCLUDED.subtype,
			rarity = EXCLUDED.rarity,
			ilvl = EXCLUDED.ilvl,
			base_primary = EXCLUDED.base_primary,
			primary_stat = EXCLUDED.primary_stat,
			stat_type = EXCLUDED.stat_type,
			speed_modifier = EXCLUDED.speed_modifier,
			crit_chance = EXCLUDED.crit_chance,
			agility_bonus = EXCLUDED.agility_bonus,
			set_name = EXCLUDED.set_name,
			special_effect = EXCLUDED.special_effect
		RETURNING item_id
	`, heroID, string(item.Slot), gearID,
		overrides.FormID, overrides.Name, overrides.Subtype, overrides.Rarity, overrides.Ilvl,
		overrides.BasePrimary, overrides.PrimaryStat, overrides.StatType,
		overrides.SpeedModifier, overrides.CritChance, overrides.AgilityBonus,
		overrides.SetName, overrides.SpecialEffect,
	).Scan(&item.ID)
	if err != nil {
		return fmt.Errorf("equip gear item: %w", err)
	}

	if hasPrev && prevItemID != item.ID {
		if err := addToInventoryTx(ctx, tx, heroID, prevGearID, prevItemID, prevOverrides); err != nil {
			return err
		}
	}
	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("equip gear item commit: %w", err)
	}
	return nil
}

// EquipInventoryItem equips an existing inventory item by item_id.
func (s *GearStore) EquipInventoryItem(ctx context.Context, heroID, itemID int64) error {
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return fmt.Errorf("equip inventory item begin: %w", err)
	}
	defer tx.Rollback(ctx)

	var (
		gearID     int64
		slot       string
		overrides  gearOverrideRow
		prevGearID int64
		prevItemID int64
		prevOv     gearOverrideRow
	)
	err = tx.QueryRow(ctx, `
		SELECT hi.gear_id, g.slot,
		       hi.form_id, hi.name, hi.subtype, hi.rarity, hi.ilvl, hi.base_primary, hi.primary_stat,
		       hi.stat_type, hi.speed_modifier, hi.crit_chance, hi.agility_bonus, hi.set_name, hi.special_effect
		FROM hero_inventory hi
		JOIN gear g ON hi.gear_id = g.id
		WHERE hi.hero_id = $1 AND hi.item_id = $2
	`, heroID, itemID).Scan(
		&gearID, &slot,
		&overrides.FormID, &overrides.Name, &overrides.Subtype, &overrides.Rarity,
		&overrides.Ilvl, &overrides.BasePrimary, &overrides.PrimaryStat,
		&overrides.StatType, &overrides.SpeedModifier, &overrides.CritChance, &overrides.AgilityBonus,
		&overrides.SetName, &overrides.SpecialEffect,
	)
	if errors.Is(err, pgx.ErrNoRows) {
		return fmt.Errorf("inventory item not found")
	}
	if err != nil {
		return fmt.Errorf("equip inventory read item: %w", err)
	}

	if err := compactInventoryAfterRemovingItem(ctx, tx, heroID, itemID); err != nil {
		return err
	}

	err = tx.QueryRow(ctx, `
		SELECT gear_id, item_id, form_id, name, subtype, rarity, ilvl, base_primary, primary_stat,
		       stat_type, speed_modifier, crit_chance, agility_bonus, set_name, special_effect
		FROM hero_gear
		WHERE hero_id = $1 AND slot = $2
	`, heroID, slot).Scan(
		&prevGearID, &prevItemID,
		&prevOv.FormID, &prevOv.Name, &prevOv.Subtype, &prevOv.Rarity,
		&prevOv.Ilvl, &prevOv.BasePrimary, &prevOv.PrimaryStat,
		&prevOv.StatType, &prevOv.SpeedModifier, &prevOv.CritChance, &prevOv.AgilityBonus,
		&prevOv.SetName, &prevOv.SpecialEffect,
	)
	hasPrev := true
	if errors.Is(err, pgx.ErrNoRows) {
		hasPrev = false
		err = nil
	} else if err != nil {
		return fmt.Errorf("equip inventory read previous: %w", err)
	}
	if hasPrev && prevItemID != itemID {
		count, err := inventoryCountTx(ctx, tx, heroID)
		if err != nil {
			return err
		}
		if count >= model.MaxInventorySlots {
			return ErrInventoryFull
		}
	}

	if _, err := tx.Exec(ctx, `
		INSERT INTO hero_gear (
			hero_id, slot, gear_id, item_id,
			form_id, name, subtype, rarity, ilvl, base_primary, primary_stat, stat_type,
			speed_modifier, crit_chance, agility_bonus, set_name, special_effect
		) VALUES (
			$1, $2, $3, $4,
			$5, $6, $7, $8, $9, $10, $11, $12,
			$13, $14, $15, $16, $17
		)
		ON CONFLICT (hero_id, slot) DO UPDATE SET
			gear_id = EXCLUDED.gear_id,
			item_id = EXCLUDED.item_id,
			form_id = EXCLUDED.form_id,
			name = EXCLUDED.name,
			subtype = EXCLUDED.subtype,
			rarity = EXCLUDED.rarity,
			ilvl = EXCLUDED.ilvl,
			base_primary = EXCLUDED.base_primary,
			primary_stat = EXCLUDED.primary_stat,
			stat_type = EXCLUDED.stat_type,
			speed_modifier = EXCLUDED.speed_modifier,
			crit_chance = EXCLUDED.crit_chance,
			agility_bonus = EXCLUDED.agility_bonus,
			set_name = EXCLUDED.set_name,
			special_effect = EXCLUDED.special_effect
	`, heroID, slot, gearID, itemID,
		overrides.FormID, overrides.Name, overrides.Subtype, overrides.Rarity, overrides.Ilvl,
		overrides.BasePrimary, overrides.PrimaryStat, overrides.StatType,
		overrides.SpeedModifier, overrides.CritChance, overrides.AgilityBonus,
		overrides.SetName, overrides.SpecialEffect,
	); err != nil {
		return fmt.Errorf("equip inventory upsert: %w", err)
	}

	if hasPrev && prevItemID != itemID {
		if err := addToInventoryTx(ctx, tx, heroID, prevGearID, prevItemID, prevOv); err != nil {
			return err
		}
	}
	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("equip inventory commit: %w", err)
	}
	return nil
}

func inventoryCountTx(ctx context.Context, tx pgx.Tx, heroID int64) (int, error) {
	var n int
	if err := tx.QueryRow(ctx, `
		SELECT COUNT(*) FROM hero_inventory WHERE hero_id = $1
	`, heroID).Scan(&n); err != nil {
		return 0, fmt.Errorf("inventory count: %w", err)
	}
	return n, nil
}

func addToInventoryTx(ctx context.Context, tx pgx.Tx, heroID, gearID, itemID int64, overrides gearOverrideRow) error {
	n, err := inventoryCountTx(ctx, tx, heroID)
	if err != nil {
		return err
	}
	if n >= model.MaxInventorySlots {
		return ErrInventoryFull
	}
	if _, err := tx.Exec(ctx, `
		INSERT INTO hero_inventory (
			hero_id, slot_index, gear_id, item_id,
			form_id, name, subtype, rarity, ilvl, base_primary, primary_stat, stat_type,
			speed_modifier, crit_chance, agility_bonus, set_name, special_effect
		) VALUES (
			$1, $2, $3, $4,
			$5, $6, $7, $8, $9, $10, $11, $12,
			$13, $14, $15, $16, $17
		)
	`, heroID, n, gearID, itemID,
		overrides.FormID, overrides.Name, overrides.Subtype, overrides.Rarity, overrides.Ilvl,
		overrides.BasePrimary, overrides.PrimaryStat, overrides.StatType,
		overrides.SpeedModifier, overrides.CritChance, overrides.AgilityBonus,
		overrides.SetName, overrides.SpecialEffect,
	); err != nil {
		return fmt.Errorf("add to inventory: %w", err)
	}
	return nil
}

// compactInventoryAfterRemovingItem deletes one backpack row if present; if a row
// was removed, rewrites hero_inventory with contiguous slot_index.
func compactInventoryAfterRemovingItem(ctx context.Context, tx pgx.Tx, heroID, itemID int64) error {
	cmd, err := tx.Exec(ctx, `
		DELETE FROM hero_inventory WHERE hero_id = $1 AND item_id = $2
	`, heroID, itemID)
	if err != nil {
		return fmt.Errorf("remove item from inventory: %w", err)
	}
	if cmd.RowsAffected() == 0 {
		return nil
	}
	rows, err := tx.Query(ctx, `
		SELECT gear_id, item_id, form_id, name, subtype, rarity, ilvl, base_primary, primary_stat,
		       stat_type, speed_modifier, crit_chance, agility_bonus, set_name, special_effect
		FROM hero_inventory
		WHERE hero_id = $1
		ORDER BY slot_index ASC
	`, heroID)
	if err != nil {
		return fmt.Errorf("list inventory after remove: %w", err)
	}
	defer rows.Close()

	type invRow struct {
		gearID    int64
		itemID    int64
		overrides gearOverrideRow
	}
	var items []invRow
	for rows.Next() {
		var row invRow
		if err := rows.Scan(
			&row.gearID, &row.itemID,
			&row.overrides.FormID, &row.overrides.Name, &row.overrides.Subtype, &row.overrides.Rarity,
			&row.overrides.Ilvl, &row.overrides.BasePrimary, &row.overrides.PrimaryStat,
			&row.overrides.StatType, &row.overrides.SpeedModifier, &row.overrides.CritChance, &row.overrides.AgilityBonus,
			&row.overrides.SetName, &row.overrides.SpecialEffect,
		); err != nil {
			return fmt.Errorf("scan inventory row: %w", err)
		}
		items = append(items, row)
	}
	if err := rows.Err(); err != nil {
		return fmt.Errorf("inventory rows: %w", err)
	}

	if _, err := tx.Exec(ctx, `DELETE FROM hero_inventory WHERE hero_id = $1`, heroID); err != nil {
		return fmt.Errorf("clear inventory for compact: %w", err)
	}
	for i, row := range items {
		if _, err := tx.Exec(ctx, `
			INSERT INTO hero_inventory (
				hero_id, slot_index, gear_id, item_id,
				form_id, name, subtype, rarity, ilvl, base_primary, primary_stat, stat_type,
				speed_modifier, crit_chance, agility_bonus, set_name, special_effect
			) VALUES (
				$1, $2, $3, $4,
				$5, $6, $7, $8, $9, $10, $11, $12,
				$13, $14, $15, $16, $17
			)
		`, heroID, i, row.gearID, row.itemID,
			row.overrides.FormID, row.overrides.Name, row.overrides.Subtype, row.overrides.Rarity, row.overrides.Ilvl,
			row.overrides.BasePrimary, row.overrides.PrimaryStat, row.overrides.StatType,
			row.overrides.SpeedModifier, row.overrides.CritChance, row.overrides.AgilityBonus,
			row.overrides.SetName, row.overrides.SpecialEffect,
		); err != nil {
			return fmt.Errorf("reinsert inventory slot %d: %w", i, err)
		}
	}
	return nil
}

// WipeAllGearForHero removes every equipped and backpack item for the hero.
func (s *GearStore) WipeAllGearForHero(ctx context.Context, heroID int64) error {
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return fmt.Errorf("wipe gear begin: %w", err)
	}
	defer tx.Rollback(ctx)

	if _, err := tx.Exec(ctx, `DELETE FROM hero_gear WHERE hero_id = $1`, heroID); err != nil {
		return fmt.Errorf("wipe hero_gear: %w", err)
	}
	if _, err := tx.Exec(ctx, `DELETE FROM hero_inventory WHERE hero_id = $1`, heroID); err != nil {
		return fmt.Errorf("wipe hero_inventory: %w", err)
	}
	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("wipe gear commit: %w", err)
	}
	return nil
}

// DeleteGearItem removes a gear archetype row by id. Prefer DeleteHeroItem for owned gear.
func (s *GearStore) DeleteGearItem(ctx context.Context, id int64) error {
	cmd, err := s.pool.Exec(ctx, `DELETE FROM gear WHERE id = $1`, id)
	if err != nil {
		return fmt.Errorf("delete gear item: %w", err)
	}
	if cmd.RowsAffected() == 0 {
		return fmt.Errorf("delete gear item: no row for id %d", id)
	}
	return nil
}

// DeleteHeroItem removes an equipped or inventory item by item_id.
func (s *GearStore) DeleteHeroItem(ctx context.Context, heroID, itemID int64) error {
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return fmt.Errorf("delete hero item begin: %w", err)
	}
	defer tx.Rollback(ctx)

	var exists bool
	if err := tx.QueryRow(ctx, `
		SELECT EXISTS (
			SELECT 1 FROM hero_inventory WHERE hero_id = $1 AND item_id = $2
		)
	`, heroID, itemID).Scan(&exists); err != nil {
		return fmt.Errorf("delete hero item lookup: %w", err)
	}
	if exists {
		if err := compactInventoryAfterRemovingItem(ctx, tx, heroID, itemID); err != nil {
			return err
		}
		if err := tx.Commit(ctx); err != nil {
			return fmt.Errorf("delete hero item commit: %w", err)
		}
		return nil
	}

	cmd, err := tx.Exec(ctx, `
		DELETE FROM hero_gear WHERE hero_id = $1 AND item_id = $2
	`, heroID, itemID)
	if err != nil {
		return fmt.Errorf("delete hero gear item: %w", err)
	}
	if cmd.RowsAffected() == 0 {
		return fmt.Errorf("delete hero item: no row for id %d", itemID)
	}
	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("delete hero item commit: %w", err)
	}
	return nil
}

// UnequipSlot moves equipped gear from the given slot into the hero's backpack.
// Returns ErrInventoryFull if there is no free slot (equipped row is left unchanged).
// If the slot is empty, returns nil (idempotent).
func (s *GearStore) UnequipSlot(ctx context.Context, heroID int64, slot model.EquipmentSlot) error {
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return fmt.Errorf("unequip begin: %w", err)
	}
	defer tx.Rollback(ctx)

	var (
		gearID    int64
		itemID    int64
		overrides gearOverrideRow
	)
	err = tx.QueryRow(ctx, `
		SELECT gear_id, item_id, form_id, name, subtype, rarity, ilvl, base_primary, primary_stat,
		       stat_type, speed_modifier, crit_chance, agility_bonus, set_name, special_effect
		FROM hero_gear WHERE hero_id = $1 AND slot = $2
	`, heroID, string(slot)).Scan(
		&gearID, &itemID,
		&overrides.FormID, &overrides.Name, &overrides.Subtype, &overrides.Rarity,
		&overrides.Ilvl, &overrides.BasePrimary, &overrides.PrimaryStat,
		&overrides.StatType, &overrides.SpeedModifier, &overrides.CritChance, &overrides.AgilityBonus,
		&overrides.SetName, &overrides.SpecialEffect,
	)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil
	}
	if err != nil {
		return fmt.Errorf("unequip read slot: %w", err)
	}

	if err := addToInventoryTx(ctx, tx, heroID, gearID, itemID, overrides); err != nil {
		return err
	}

	if _, err := tx.Exec(ctx, `
		DELETE FROM hero_gear WHERE hero_id = $1 AND slot = $2
	`, heroID, string(slot)); err != nil {
		return fmt.Errorf("unequip delete hero_gear: %w", err)
	}

	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("unequip commit: %w", err)
	}
	return nil
}

// GetHeroInventory loads unequipped gear ordered by slot_index.
func (s *GearStore) GetHeroInventory(ctx context.Context, heroID int64) ([]*model.GearItem, error) {
	rows, err := s.pool.Query(ctx, `
		SELECT hi.item_id, g.slot,
		       COALESCE(hi.form_id, g.form_id),
		       COALESCE(hi.name, g.name),
		       COALESCE(hi.subtype, g.subtype),
		       COALESCE(hi.rarity, g.rarity),
		       COALESCE(hi.ilvl, g.ilvl),
		       COALESCE(hi.base_primary, g.base_primary),
		       COALESCE(hi.primary_stat, g.primary_stat),
		       COALESCE(hi.stat_type, g.stat_type),
		       COALESCE(hi.speed_modifier, g.speed_modifier),
		       COALESCE(hi.crit_chance, g.crit_chance),
		       COALESCE(hi.agility_bonus, g.agility_bonus),
		       COALESCE(hi.set_name, g.set_name),
		       COALESCE(hi.special_effect, g.special_effect)
		FROM hero_inventory hi
		JOIN gear g ON hi.gear_id = g.id
		WHERE hi.hero_id = $1
		ORDER BY hi.slot_index ASC
	`, heroID)
	if err != nil {
		return nil, fmt.Errorf("get hero inventory: %w", err)
	}
	defer rows.Close()

	var out []*model.GearItem
	for rows.Next() {
		var item model.GearItem
		var slot, rarity string
		if err := rows.Scan(
			&item.ID, &slot, &item.FormID, &item.Name, &item.Subtype,
			&rarity, &item.Ilvl,
			&item.BasePrimary, &item.PrimaryStat, &item.StatType,
			&item.SpeedModifier, &item.CritChance, &item.AgilityBonus,
			&item.SetName, &item.SpecialEffect,
		); err != nil {
			return nil, fmt.Errorf("scan inventory gear: %w", err)
		}
		item.Slot = model.EquipmentSlot(slot)
		item.Rarity = model.Rarity(rarity)
		out = append(out, &item)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("hero inventory rows: %w", err)
	}
	return out, nil
}

// AddToInventory inserts gear into the next free backpack slot. Fails if inventory is full.
func (s *GearStore) AddToInventory(ctx context.Context, heroID int64, item *model.GearItem) error {
	if item == nil {
		return fmt.Errorf("nil gear item")
	}
	var n int
	if err := s.pool.QueryRow(ctx, `
		SELECT COUNT(*) FROM hero_inventory WHERE hero_id = $1
	`, heroID).Scan(&n); err != nil {
		return fmt.Errorf("inventory count: %w", err)
	}
	if n >= model.MaxInventorySlots {
		return ErrInventoryFull
	}
	gearID, err := s.resolveArchetypeID(ctx, item)
	if err != nil {
		return err
	}
	overrides := overrideRowFromItem(item)
	err = s.pool.QueryRow(ctx, `
		INSERT INTO hero_inventory (
			hero_id, slot_index, gear_id, item_id,
			form_id, name, subtype, rarity, ilvl, base_primary, primary_stat, stat_type,
			speed_modifier, crit_chance, agility_bonus, set_name, special_effect
		) VALUES (
			$1, $2, $3, nextval('public.hero_item_id_seq'),
			$4, $5, $6, $7, $8, $9, $10, $11,
			$12, $13, $14, $15, $16
		)
		RETURNING item_id
	`, heroID, n, gearID,
		overrides.FormID, overrides.Name, overrides.Subtype, overrides.Rarity, overrides.Ilvl,
		overrides.BasePrimary, overrides.PrimaryStat, overrides.StatType,
		overrides.SpeedModifier, overrides.CritChance, overrides.AgilityBonus,
		overrides.SetName, overrides.SpecialEffect,
	).Scan(&item.ID)
	if err != nil {
		return fmt.Errorf("add to inventory: %w", err)
	}
	return nil
}

// ReplaceHeroInventory deletes all backpack rows for the hero and re-inserts from the slice.
// Used when persisting offline-simulated heroes with in-memory-only gear rows (id may be 0).
func (s *GearStore) ReplaceHeroInventory(ctx context.Context, heroID int64, items []*model.GearItem) error {
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return fmt.Errorf("replace inventory begin: %w", err)
	}
	defer tx.Rollback(ctx)

	if _, err := tx.Exec(ctx, `DELETE FROM hero_inventory WHERE hero_id = $1`, heroID); err != nil {
		return fmt.Errorf("replace inventory delete: %w", err)
	}
	for i, item := range items {
		if item == nil || i >= model.MaxInventorySlots {
			continue
		}
		gearID, err := s.resolveArchetypeID(ctx, item)
		if err != nil {
			return err
		}
		overrides := overrideRowFromItem(item)
		if item.ID == 0 {
			err := tx.QueryRow(ctx, `
				INSERT INTO hero_inventory (
					hero_id, slot_index, gear_id, item_id,
					form_id, name, subtype, rarity, ilvl, base_primary, primary_stat, stat_type,
					speed_modifier, crit_chance, agility_bonus, set_name, special_effect
				) VALUES (
					$1, $2, $3, nextval('public.hero_item_id_seq'),
					$4, $5, $6, $7, $8, $9, $10, $11,
					$12, $13, $14, $15, $16
				)
				RETURNING item_id
			`, heroID, i, gearID,
				overrides.FormID, overrides.Name, overrides.Subtype, overrides.Rarity, overrides.Ilvl,
				overrides.BasePrimary, overrides.PrimaryStat, overrides.StatType,
				overrides.SpeedModifier, overrides.CritChance, overrides.AgilityBonus,
				overrides.SetName, overrides.SpecialEffect,
			).Scan(&item.ID)
			if err != nil {
				return fmt.Errorf("replace inventory insert: %w", err)
			}
			continue
		}
		if _, err := tx.Exec(ctx, `
			INSERT INTO hero_inventory (
				hero_id, slot_index, gear_id, item_id,
				form_id, name, subtype, rarity, ilvl, base_primary, primary_stat, stat_type,
				speed_modifier, crit_chance, agility_bonus, set_name, special_effect
			) VALUES (
				$1, $2, $3, $4,
				$5, $6, $7, $8, $9, $10, $11, $12,
				$13, $14, $15, $16, $17
			)
		`, heroID, i, gearID, item.ID,
			overrides.FormID, overrides.Name, overrides.Subtype, overrides.Rarity, overrides.Ilvl,
			overrides.BasePrimary, overrides.PrimaryStat, overrides.StatType,
			overrides.SpeedModifier, overrides.CritChance, overrides.AgilityBonus,
			overrides.SetName, overrides.SpecialEffect,
		); err != nil {
			return fmt.Errorf("replace inventory insert: %w", err)
		}
	}
	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("replace inventory commit: %w", err)
	}
	return nil
}

func ptrString(v string) *string {
	return &v
}