initial boilerplate
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@@ -0,0 +1,287 @@
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package db
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import (
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"context"
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"fmt"
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"time"
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"github.com/google/uuid"
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"github.com/jackc/pgx/v5/pgxpool"
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)
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// Queries holds the database connection pool.
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// All database operations are methods on this type.
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// This pattern (a "repository") keeps SQL out of your handlers.
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type Queries struct {
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pool *pgxpool.Pool
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}
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func New(pool *pgxpool.Pool) *Queries {
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return &Queries{pool: pool}
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}
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// ---- Receipts ----
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type CreateReceiptParams struct {
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StoreName string
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ReceiptDate time.Time
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ImagePath string
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City string
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Country string
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}
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type Receipt struct {
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ID uuid.UUID
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StoreName string
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ReceiptDate time.Time
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ImagePath string
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City string
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Country string
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SubmittedAt time.Time
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}
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func (q *Queries) CreateReceipt(ctx context.Context, p CreateReceiptParams) (Receipt, error) {
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var r Receipt
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err := q.pool.QueryRow(ctx, `
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INSERT INTO receipts (store_name, receipt_date, image_path, city, country)
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VALUES ($1, $2, $3, $4, $5)
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RETURNING id, store_name, receipt_date, image_path, city, country, submitted_at
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`, p.StoreName, p.ReceiptDate, p.ImagePath, p.City, p.Country,
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).Scan(&r.ID, &r.StoreName, &r.ReceiptDate, &r.ImagePath, &r.City, &r.Country, &r.SubmittedAt)
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if err != nil {
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return Receipt{}, fmt.Errorf("create receipt: %w", err)
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}
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return r, nil
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}
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func (q *Queries) GetReceiptByID(ctx context.Context, id uuid.UUID) (Receipt, error) {
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var r Receipt
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err := q.pool.QueryRow(ctx, `
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SELECT id, store_name, receipt_date, image_path, city, country, submitted_at
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FROM receipts WHERE id = $1
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`, id).Scan(&r.ID, &r.StoreName, &r.ReceiptDate, &r.ImagePath, &r.City, &r.Country, &r.SubmittedAt)
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if err != nil {
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return Receipt{}, fmt.Errorf("get receipt: %w", err)
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}
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return r, nil
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}
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// ---- Line Items ----
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type CreateLineItemParams struct {
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ReceiptID uuid.UUID
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RawName string
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CanonicalName string // may be empty if not matched yet
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PriceCents int
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Quantity float64
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}
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func (q *Queries) CreateLineItem(ctx context.Context, p CreateLineItemParams) error {
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var canonical *string
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if p.CanonicalName != "" {
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canonical = &p.CanonicalName
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}
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_, err := q.pool.Exec(ctx, `
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INSERT INTO line_items (receipt_id, raw_name, canonical_name, price_cents, quantity)
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VALUES ($1, $2, $3, $4, $5)
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`, p.ReceiptID, p.RawName, canonical, p.PriceCents, p.Quantity)
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if err != nil {
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return fmt.Errorf("create line item: %w", err)
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}
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return nil
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}
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// ---- Canonical Items ----
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type CanonicalItem struct {
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Name string
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DisplayName string
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Category string
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Unit string
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Aliases []string
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}
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func (q *Queries) ListCanonicalItems(ctx context.Context) ([]CanonicalItem, error) {
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rows, err := q.pool.Query(ctx, `
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SELECT name, display_name, category, unit, aliases
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FROM canonical_items
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ORDER BY category, display_name
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`)
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if err != nil {
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return nil, fmt.Errorf("list canonical items: %w", err)
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}
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defer rows.Close()
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var items []CanonicalItem
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for rows.Next() {
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var item CanonicalItem
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if err := rows.Scan(&item.Name, &item.DisplayName, &item.Category, &item.Unit, &item.Aliases); err != nil {
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return nil, err
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}
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items = append(items, item)
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}
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return items, rows.Err()
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}
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// ---- Price History ----
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type PricePoint struct {
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YearMonth time.Time
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AvgPriceCents int
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SampleCount int
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}
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// GetPriceHistory returns monthly average prices for a canonical item.
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func (q *Queries) GetPriceHistory(ctx context.Context, canonicalName string) ([]PricePoint, error) {
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rows, err := q.pool.Query(ctx, `
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SELECT year_month, avg_price_cents, sample_count
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FROM price_snapshots
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WHERE canonical_name = $1
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ORDER BY year_month ASC
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`, canonicalName)
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if err != nil {
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return nil, fmt.Errorf("get price history: %w", err)
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}
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defer rows.Close()
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var points []PricePoint
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for rows.Next() {
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var p PricePoint
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if err := rows.Scan(&p.YearMonth, &p.AvgPriceCents, &p.SampleCount); err != nil {
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return nil, err
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}
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points = append(points, p)
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}
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return points, rows.Err()
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}
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// TopMover represents the biggest price change over a period.
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type TopMover struct {
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CanonicalName string
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DisplayName string
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Category string
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PriceThen int
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PriceNow int
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PctChange float64
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}
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// GetTopMovers finds items with the largest price change over the last N months.
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func (q *Queries) GetTopMovers(ctx context.Context, months int, limit int) ([]TopMover, error) {
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rows, err := q.pool.Query(ctx, `
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WITH
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-- Most recent snapshot per item
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latest AS (
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SELECT DISTINCT ON (canonical_name)
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canonical_name, avg_price_cents AS price_now, year_month
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FROM price_snapshots
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ORDER BY canonical_name, year_month DESC
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),
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-- Snapshot closest to N months ago
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old AS (
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SELECT DISTINCT ON (ps.canonical_name)
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ps.canonical_name, ps.avg_price_cents AS price_then
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FROM price_snapshots ps
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WHERE ps.year_month <= (now() - ($1 || ' months')::interval)::date
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ORDER BY ps.canonical_name, ps.year_month DESC
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)
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SELECT
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l.canonical_name,
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ci.display_name,
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ci.category,
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o.price_then,
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l.price_now,
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ROUND(((l.price_now - o.price_then)::numeric / o.price_then) * 100, 1) AS pct_change
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FROM latest l
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JOIN old o ON l.canonical_name = o.canonical_name
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JOIN canonical_items ci ON l.canonical_name = ci.name
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ORDER BY ABS(pct_change) DESC
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LIMIT $2
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`, months, limit)
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if err != nil {
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return nil, fmt.Errorf("get top movers: %w", err)
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}
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defer rows.Close()
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var movers []TopMover
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for rows.Next() {
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var m TopMover
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if err := rows.Scan(&m.CanonicalName, &m.DisplayName, &m.Category,
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&m.PriceThen, &m.PriceNow, &m.PctChange); err != nil {
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return nil, err
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}
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movers = append(movers, m)
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}
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return movers, rows.Err()
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}
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// InflationSummary returns the overall purchasing power change since a base year.
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type InflationSummary struct {
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BaseYear int
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CurrentYear int
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BasketThen int // average cents across tracked items at base year
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BasketNow int // average cents across tracked items now
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PurchasingPower float64 // e.g. 0.58 means $1 in baseYear = $0.58 today
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TotalPctChange float64 // e.g. 72.4 means prices are 72.4% higher
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}
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func (q *Queries) GetInflationSummary(ctx context.Context, baseYear int) (InflationSummary, error) {
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var s InflationSummary
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err := q.pool.QueryRow(ctx, `
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WITH
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base AS (
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SELECT AVG(avg_price_cents)::int AS avg_price
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FROM price_snapshots
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WHERE EXTRACT(YEAR FROM year_month) = $1
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),
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current AS (
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SELECT AVG(avg_price_cents)::int AS avg_price
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FROM price_snapshots
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WHERE year_month >= date_trunc('year', now()) - interval '1 year'
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)
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SELECT
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$1,
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EXTRACT(YEAR FROM now())::int,
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base.avg_price,
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current.avg_price,
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ROUND((base.avg_price::numeric / current.avg_price) * 100, 1),
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ROUND(((current.avg_price - base.avg_price)::numeric / base.avg_price) * 100, 1)
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FROM base, current
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`, baseYear).Scan(
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&s.BaseYear, &s.CurrentYear,
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&s.BasketThen, &s.BasketNow,
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&s.PurchasingPower, &s.TotalPctChange,
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)
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if err != nil {
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return InflationSummary{}, fmt.Errorf("get inflation summary: %w", err)
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}
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return s, nil
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}
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// RebuildSnapshots re-aggregates all line_items into price_snapshots.
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// Run this as a nightly cron job or after a batch of new submissions.
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func (q *Queries) RebuildSnapshots(ctx context.Context) error {
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_, err := q.pool.Exec(ctx, `
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INSERT INTO price_snapshots (canonical_name, year_month, avg_price_cents, sample_count)
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SELECT
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canonical_name,
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date_trunc('month', r.receipt_date)::date AS year_month,
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ROUND(AVG(li.unit_price_cents))::int AS avg_price_cents,
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COUNT(*) AS sample_count
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FROM line_items li
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JOIN receipts r ON li.receipt_id = r.id
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WHERE li.canonical_name IS NOT NULL
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GROUP BY canonical_name, year_month
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ON CONFLICT (canonical_name, year_month)
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DO UPDATE SET
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avg_price_cents = EXCLUDED.avg_price_cents,
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sample_count = EXCLUDED.sample_count
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`)
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if err != nil {
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return fmt.Errorf("rebuild snapshots: %w", err)
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}
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return nil
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}
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