Seed provenance and inventory: source links and seed lots (#50)

"German Red Garlic" now links back to the Johnny's page it came from, and pansy
knows how much is left.

Two modelling calls, both of which look like omissions unless stated.

The plant catalog stays FLAT — no species/variety hierarchy. A row in your
catalog just is the thing you plant; the built-in "Garlic" is a generic starting
point you clone. A hierarchy buys taxonomy nobody asked for and complicates
every join.

Inventory belongs to a PURCHASE, not to a variety. You might buy the same garlic
from two vendors in two years at two prices and two germination rates; quantity
columns on plants would collapse all of that into one number and lose it. So
lots get their own table, and owner_id sits on the lot rather than being
inherited from the plant — you can buy generic built-in Garlic from Johnny's and
the record is still yours alone. Lots are never shared along with a garden.

`remaining` is derived, never stored: quantity minus the summed effective count
of the active plantings attributed to the lot. The alternative — decrementing a
column when you plant — drifts the moment anything edits or removes a planting
behind its back, and once it has drifted there's no way to tell what the true
number was. Removing a plop gives the seed back with nothing having to remember
to. The usage query returns raw radius/count/spacing rather than a SUM, because
the effective-count formula lives in the service and reproducing it in SQL would
guarantee the two drift apart.

source_url is validated as http(s) with a host, on both plants and lots. It
renders as a clickable link, so that check is load-bearing rather than tidiness:
without it a stored javascript: URL becomes script execution the moment someone
clicks it. Schemeless and relative URLs are refused too — they'd resolve against
pansy's own origin, which is never what a vendor link means.

A planting's lot must be the actor's AND a lot of the plant being planted.
Attributing a garlic planting to a tomato lot would silently corrupt every
remaining count downstream, so it's refused rather than stored, and re-checked
on update in case a plant swap invalidated a previously-valid attribution.

Deleting a lot leaves its plantings alone with a null link: the plants really
were in the ground, whatever happened to the record of the packet.

Closes #50

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

internal/store/seed_lots.go

@@ -0,0 +1,184 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/domain"
+)
+
+// seedLotColumns lists seed_lots columns in the order scanSeedLot expects.
+const seedLotColumns = `id, owner_id, plant_id, vendor, source_url, sku, lot_code,
+	purchased_at, packed_for_year, quantity, unit, cost_cents, germination_pct, notes,
+	version, created_at, updated_at`
+
+func scanSeedLot(s scanner) (*domain.SeedLot, error) {
+	var l domain.SeedLot
+	if err := s.Scan(
+		&l.ID, &l.OwnerID, &l.PlantID, &l.Vendor, &l.SourceURL, &l.SKU, &l.LotCode,
+		&l.PurchasedAt, &l.PackedForYear, &l.Quantity, &l.Unit, &l.CostCents,
+		&l.GerminationPct, &l.Notes, &l.Version, &l.CreatedAt, &l.UpdatedAt,
+	); err != nil {
+		return nil, err
+	}
+	return &l, nil
+}
+
+// CreateSeedLot inserts a lot (fields already validated by the service).
+func (d *DB) CreateSeedLot(ctx context.Context, l *domain.SeedLot) (*domain.SeedLot, error) {
+	created, err := scanSeedLot(d.sql.QueryRowContext(ctx,
+		`INSERT INTO seed_lots
+		   (owner_id, plant_id, vendor, source_url, sku, lot_code, purchased_at,
+		    packed_for_year, quantity, unit, cost_cents, germination_pct, notes)
+		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+		 RETURNING `+seedLotColumns,
+		l.OwnerID, l.PlantID, l.Vendor, l.SourceURL, l.SKU, l.LotCode, l.PurchasedAt,
+		l.PackedForYear, l.Quantity, l.Unit, l.CostCents, l.GerminationPct, l.Notes,
+	))
+	if err != nil {
+		return nil, fmt.Errorf("store: insert seed lot: %w", err)
+	}
+	return created, nil
+}
+
+// GetSeedLot returns a lot by id, or domain.ErrNotFound. Ownership is the
+// service's check, not this one's.
+func (d *DB) GetSeedLot(ctx context.Context, id int64) (*domain.SeedLot, error) {
+	l, err := scanSeedLot(d.sql.QueryRowContext(ctx,
+		`SELECT `+seedLotColumns+` FROM seed_lots WHERE id = ?`, id))
+	if errors.Is(err, sql.ErrNoRows) {
+		return nil, domain.ErrNotFound
+	}
+	if err != nil {
+		return nil, fmt.Errorf("store: get seed lot: %w", err)
+	}
+	return l, nil
+}
+
+// ListSeedLotsForOwner returns every lot the actor owns, newest purchase first
+// (undated lots last), then by id. Optionally narrowed to one plant. Always a
+// non-nil slice.
+func (d *DB) ListSeedLotsForOwner(ctx context.Context, ownerID int64, plantID *int64) ([]domain.SeedLot, error) {
+	query := `SELECT ` + seedLotColumns + ` FROM seed_lots WHERE owner_id = ?`
+	args := []any{ownerID}
+	if plantID != nil {
+		query += ` AND plant_id = ?`
+		args = append(args, *plantID)
+	}
+	// NULL purchased_at sorts last: an undated lot is the least useful to see first.
+	query += ` ORDER BY purchased_at IS NULL, purchased_at DESC, id DESC`
+
+	rows, err := d.sql.QueryContext(ctx, query, args...)
+	if err != nil {
+		return nil, fmt.Errorf("store: list seed lots: %w", err)
+	}
+	defer rows.Close()
+
+	lots := []domain.SeedLot{}
+	for rows.Next() {
+		l, err := scanSeedLot(rows)
+		if err != nil {
+			return nil, fmt.Errorf("store: scan seed lot: %w", err)
+		}
+		lots = append(lots, *l)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, fmt.Errorf("store: iterate seed lots: %w", err)
+	}
+	return lots, nil
+}
+
+// UpdateSeedLot applies a version-guarded update of every mutable column (the
+// service merges partial patches onto the current row first). Same contract as
+// the other mutable resources: the updated row, or (current, ErrVersionConflict).
+// plant_id and owner_id are immutable — re-pointing a purchase at a different
+// variety or user would rewrite history rather than correct it.
+func (d *DB) UpdateSeedLot(ctx context.Context, l *domain.SeedLot) (*domain.SeedLot, error) {
+	updated, err := scanSeedLot(d.sql.QueryRowContext(ctx,
+		`UPDATE seed_lots
+		    SET vendor = ?, source_url = ?, sku = ?, lot_code = ?, purchased_at = ?,
+		        packed_for_year = ?, quantity = ?, unit = ?, cost_cents = ?,
+		        germination_pct = ?, notes = ?,
+		        version = version + 1,
+		        updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+		  WHERE id = ? AND version = ?
+		  RETURNING `+seedLotColumns,
+		l.Vendor, l.SourceURL, l.SKU, l.LotCode, l.PurchasedAt, l.PackedForYear,
+		l.Quantity, l.Unit, l.CostCents, l.GerminationPct, l.Notes,
+		l.ID, l.Version,
+	))
+	if errors.Is(err, sql.ErrNoRows) {
+		current, gerr := d.GetSeedLot(ctx, l.ID)
+		if gerr != nil {
+			return nil, gerr
+		}
+		return current, domain.ErrVersionConflict
+	}
+	if err != nil {
+		return nil, fmt.Errorf("store: update seed lot: %w", err)
+	}
+	return updated, nil
+}
+
+// DeleteSeedLot removes a lot. Plantings attributed to it survive with a NULL
+// seed_lot_id (see the migration): the plants really were in the ground,
+// whatever happened to the record of the packet.
+func (d *DB) DeleteSeedLot(ctx context.Context, id int64) error {
+	res, err := d.sql.ExecContext(ctx, `DELETE FROM seed_lots WHERE id = ?`, id)
+	if err != nil {
+		return fmt.Errorf("store: delete seed lot: %w", err)
+	}
+	n, err := res.RowsAffected()
+	if err != nil {
+		return fmt.Errorf("store: seed lot delete rows: %w", err)
+	}
+	if n == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}
+
+// SeedLotUse is one active planting attributed to a lot, carrying just enough to
+// compute its effective plant count.
+type SeedLotUse struct {
+	LotID     int64
+	RadiusCM  float64
+	Count     *int
+	SpacingCM float64
+}
+
+// SeedLotUsage returns the ACTIVE plantings attributed to any of the owner's
+// lots — the "used" half of a lot's remaining quantity.
+//
+// It returns the raw ingredients rather than a SUM, because the effective count
+// of a planting is its explicit count when it has one and the derived
+// π·r²/spacing² formula otherwise. That formula lives in the service; reproducing
+// it in SQL would guarantee the two drift apart.
+func (d *DB) SeedLotUsage(ctx context.Context, ownerID int64) ([]SeedLotUse, error) {
+	rows, err := d.sql.QueryContext(ctx,
+		`SELECT pl.seed_lot_id, pl.radius_cm, pl.count, p.spacing_cm
+		   FROM plantings pl
+		   JOIN seed_lots sl ON sl.id = pl.seed_lot_id
+		   JOIN plants p     ON p.id = pl.plant_id
+		  WHERE sl.owner_id = ? AND pl.removed_at IS NULL`,
+		ownerID)
+	if err != nil {
+		return nil, fmt.Errorf("store: seed lot usage: %w", err)
+	}
+	defer rows.Close()
+
+	uses := []SeedLotUse{}
+	for rows.Next() {
+		var u SeedLotUse
+		if err := rows.Scan(&u.LotID, &u.RadiusCM, &u.Count, &u.SpacingCM); err != nil {
+			return nil, fmt.Errorf("store: scan seed lot usage: %w", err)
+		}
+		uses = append(uses, u)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, fmt.Errorf("store: iterate seed lot usage: %w", err)
+	}
+	return uses, nil
+}