package items

import (
	"context"
	"database/sql"
	"errors"

	"github.com/uptrace/bun"
)

// BunRepository is the Postgres implementation of Repository. It is the
// only file in the package that speaks Bun/SQL.
type BunRepository struct {
	db *bun.DB
}

// NewBunRepository wraps a *bun.DB opened by internal/database.
func NewBunRepository(db *bun.DB) *BunRepository {
	return &BunRepository{db: db}
}

// List returns items newest-first, honoring the (already normalized) filter.
// An empty result set encodes as [] on the wire, not null.
func (r *BunRepository) List(ctx context.Context, f Filter) ([]Item, error) {
	var out []Item
	q := r.db.NewSelect().Model(&out)
	if f.Status != "" {
		q = q.Where("i.status = ?", f.Status)
	}
	if err := q.
		Order("i.created_at DESC", "i.id DESC").
		Limit(f.Limit).
		Offset(f.Offset).
		Scan(ctx); err != nil {
		return nil, err
	}
	if out == nil {
		out = []Item{}
	}
	return out, nil
}

// Get fetches a single item by id, mapping missing rows to ErrNotFound.
func (r *BunRepository) Get(ctx context.Context, id int64) (Item, error) {
	var item Item
	err := r.db.NewSelect().Model(&item).Where("i.id = ?", id).Scan(ctx)
	if errors.Is(err, sql.ErrNoRows) {
		return Item{}, ErrNotFound
	}
	return item, err
}

// Create inserts item and reads back the generated columns.
func (r *BunRepository) Create(ctx context.Context, item *Item) error {
	return r.db.NewInsert().Model(item).Returning("*").Scan(ctx, item)
}

// Update persists item (matched by primary key); ErrNotFound when the row
// is gone.
func (r *BunRepository) Update(ctx context.Context, item *Item) error {
	res, err := r.db.NewUpdate().Model(item).WherePK().Exec(ctx)
	if err != nil {
		return err
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return ErrNotFound
	}
	return nil
}

// Delete removes an item by id; ErrNotFound when the row is gone.
func (r *BunRepository) Delete(ctx context.Context, id int64) error {
	res, err := r.db.NewDelete().Model((*Item)(nil)).Where("i.id = ?", id).Exec(ctx)
	if err != nil {
		return err
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return ErrNotFound
	}
	return nil
}