Generate the week's Supply run from its plan

Add internal/shopping with Generate(weekStart), one entry point for the
first generation and every regeneration. It builds one group per plan
day (dinner_id, date, position by date) and one item per ingredient of
the dinner's recipe, in ingredient order, reusing the values recipe
grounding stored: a fetched recipe's normalized name with qty and unit
joined for display, or a manual recipe's line as typed with no qty. A
day whose dinner has no recipe or no ingredients gets no group and is
reported in Skipped. Regenerating keeps the id and needed flag of each
item whose (dinner_id, name) is unchanged, matching repeated names in
order; new items are needed and items no longer planned are removed. It
is deterministic and makes no model call. A frozen list is refused.

Migration 0016 makes shopping_lists.title nullable (never empty) so a
list exists untitled until the AI titles it, and adds shopping_groups.date.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/shopping/shopping.go

@@ -0,0 +1,376 @@
+// Package shopping keeps the household's Supply runs: each week's
+// shopping list, generated from the week's plan and grouped by dinner, and
+// the Supply archive they are frozen into.
+//
+// Generate makes a week's Supply run from its plan, and remakes it after
+// the plan changes. It is deterministic and runs no model: an item is one
+// ingredient of the dinner's recipe exactly as recipe grounding stored it
+// (see Generate).
+package shopping
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+	"strings"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/dinners"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/household"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
+)
+
+// List statuses (the shopping_lists.status column).
+const (
+	StatusCurrent  = "current"
+	StatusArchived = "archived"
+)
+
+// Reasons a plan day has no group on its Supply run.
+const (
+	// SkipNoRecipe: the day's dinner has no recipe, as while its grounding
+	// is pending or after it failed.
+	SkipNoRecipe = "no_recipe"
+	// SkipNoIngredients: the day's dinner's recipe lists no ingredients.
+	SkipNoIngredients = "no_ingredients"
+)
+
+// ErrPlanNotFound is a generation for a week with no plan.
+var ErrPlanNotFound = errors.New("the week has no plan")
+
+// ErrFrozen is a generation for a week whose Supply run is frozen into the
+// Supply archive, which is read-only.
+var ErrFrozen = errors.New("the week's Supply run is in the Supply archive and can no longer change")
+
+// Service generates Supply runs.
+type Service struct {
+	st *store.Store
+}
+
+// NewService returns a service over st.
+func NewService(st *store.Store) (*Service, error) {
+	if st == nil {
+		return nil, errors.New("shopping: nil store")
+	}
+	return &Service{st: st}, nil
+}
+
+// List is a Supply run.
+type List struct {
+	ID string `json:"id"`
+	// WeekStart is the Monday of the list's week, YYYY-MM-DD.
+	WeekStart string `json:"week_start"`
+	PlanID    string `json:"plan_id"`
+	// Title is the AI-written post title; nil until it is written, when
+	// the week label stands in for it.
+	Title  *string `json:"title"`
+	Status string  `json:"status"`
+	Groups []Group `json:"groups"`
+}
+
+// Group is the items of one plan day's dinner.
+type Group struct {
+	ID         string `json:"id"`
+	DinnerID   string `json:"dinner_id"`
+	DinnerName string `json:"dinner_name"`
+	// Date is the plan day, household-local YYYY-MM-DD.
+	Date     string `json:"date"`
+	Position int    `json:"position"`
+	Items    []Item `json:"items"`
+}
+
+// Item is one ingredient to buy.
+type Item struct {
+	ID   string `json:"id"`
+	Name string `json:"name"`
+	// Qty is the quantity as shown, such as "2 cups" or "500 g"; nil when
+	// the recipe gives none.
+	Qty *string `json:"qty"`
+	// Needed is false once the household marks the item "have it".
+	Needed   bool `json:"needed"`
+	Position int  `json:"position"`
+}
+
+// SkippedDay is a plan day with no group on the list, and why.
+type SkippedDay struct {
+	Date       string `json:"date"`
+	DinnerID   string `json:"dinner_id"`
+	DinnerName string `json:"dinner_name"`
+	// Reason is SkipNoRecipe or SkipNoIngredients.
+	Reason string `json:"reason"`
+}
+
+// Generated is the outcome of Generate.
+type Generated struct {
+	List List `json:"list"`
+	// Skipped are the plan days whose dinner has no ingredients to shop
+	// for, by date.
+	Skipped []SkippedDay `json:"skipped"`
+}
+
+// Generate makes the Supply run of the week starting weekStart from the
+// week's plan, creating it untitled the first time and remaking it after
+// that, in one transaction.
+//
+// The list has one group per plan day with a dinner, by date, holding one
+// item per ingredient of the dinner's recipe, by the ingredient's
+// position. A fetched recipe's ingredients are normalized when it is
+// grounded (normalize_recipe): the item is the ingredient's name, and its
+// quantity is qty and unit joined by a space ("2 cups"), either alone when
+// the other is missing, or nil when both are. A recipe entered by hand is
+// stored as typed, unnormalized: each item is its line as typed, with no
+// quantity. A day whose dinner has no recipe or whose recipe has no
+// ingredients gets no group and is reported in Skipped.
+//
+// Remaking keeps what the household marked: an item is the same item as
+// before when its dinner and name are the same, wherever the dinner and
+// the ingredient now are, so it keeps its id and needed flag. When a
+// dinner lists a name more than once, its first such item matches the
+// first one before, the second the second, and so on. Any other item is
+// new and needed; an item no longer on the plan is removed, and with it a
+// group no longer on the plan.
+//
+// A week with no plan is ErrPlanNotFound; a list frozen into the Supply
+// archive is ErrFrozen. A fetched recipe's ingredient without a name is an
+// error: grounding always names one.
+func (s *Service) Generate(ctx context.Context, weekStart store.LocalDate) (Generated, error) {
+	if _, err := household.WeekDays(weekStart); err != nil {
+		return Generated{}, fmt.Errorf("shopping: generate: %w", err)
+	}
+	var out Generated
+	err := s.st.WithTx(ctx, func(tx *sql.Tx) error {
+		q := db.New(tx)
+		plan, err := q.GetWeekPlan(ctx, weekStart.String())
+		if errors.Is(err, sql.ErrNoRows) {
+			return ErrPlanNotFound
+		}
+		if err != nil {
+			return fmt.Errorf("shopping: read plan: %w", err)
+		}
+		want, skipped, err := wanted(ctx, q, plan.ID)
+		if err != nil {
+			return err
+		}
+		now := store.Now().String()
+		list, err := q.GetShoppingList(ctx, weekStart.String())
+		if err != nil && !errors.Is(err, sql.ErrNoRows) {
+			return fmt.Errorf("shopping: read list: %w", err)
+		}
+		switch {
+		case err != nil: // no list yet
+			list = db.ShoppingList{ID: store.NewID(), WeekStart: weekStart.String(), PlanID: plan.ID, Status: StatusCurrent}
+			err = q.CreateShoppingList(ctx, db.CreateShoppingListParams{
+				ID: list.ID, WeekStart: list.WeekStart, PlanID: list.PlanID, CreatedAt: now, UpdatedAt: now,
+			})
+		case list.FrozenAt.Valid || list.Status == StatusArchived:
+			return ErrFrozen
+		default:
+			list.PlanID = plan.ID
+			err = q.RegenerateShoppingList(ctx, db.RegenerateShoppingListParams{PlanID: plan.ID, UpdatedAt: now, ID: list.ID})
+		}
+		if err != nil {
+			return fmt.Errorf("shopping: store list: %w", err)
+		}
+		groups, err := reconcile(ctx, q, list.ID, want, now)
+		if err != nil {
+			return err
+		}
+		out = Generated{
+			List: List{
+				ID:        list.ID,
+				WeekStart: list.WeekStart,
+				PlanID:    list.PlanID,
+				Title:     nullString(list.Title),
+				Status:    list.Status,
+				Groups:    groups,
+			},
+			Skipped: skipped,
+		}
+		return nil
+	})
+	if err != nil {
+		return Generated{}, err
+	}
+	return out, nil
+}
+
+// wantGroup is a group the plan asks for, before it is stored.
+type wantGroup struct {
+	date, dinnerID, dinnerName string
+	items                      []wantItem
+}
+
+type wantItem struct {
+	name string
+	qty  sql.NullString
+}
+
+// wanted reads plan planID's days and their dinners' ingredients: the
+// groups the list must have, by date, and the days that get none.
+func wanted(ctx context.Context, q *db.Queries, planID string) ([]wantGroup, []SkippedDay, error) {
+	days, err := q.ListPlanDays(ctx, planID)
+	if err != nil {
+		return nil, nil, fmt.Errorf("shopping: read plan days: %w", err)
+	}
+	var (
+		groups  []wantGroup
+		skipped []SkippedDay
+	)
+	for _, day := range days {
+		d := day.Dinner
+		skip := SkippedDay{Date: day.Date, DinnerID: d.ID, DinnerName: d.Name}
+		if !d.RecipeID.Valid {
+			skip.Reason = SkipNoRecipe
+			skipped = append(skipped, skip)
+			continue
+		}
+		recipe, err := q.GetRecipe(ctx, d.RecipeID.String)
+		if err != nil {
+			return nil, nil, fmt.Errorf("shopping: read recipe %s of dinner %s: %w", d.RecipeID.String, d.ID, err)
+		}
+		ings, err := q.ListRecipeIngredients(ctx, recipe.ID)
+		if err != nil {
+			return nil, nil, fmt.Errorf("shopping: read ingredients of recipe %s: %w", recipe.ID, err)
+		}
+		if len(ings) == 0 {
+			skip.Reason = SkipNoIngredients
+			skipped = append(skipped, skip)
+			continue
+		}
+		manual := dinners.IsManualRecipe(recipe.SourceUrl)
+		g := wantGroup{date: day.Date, dinnerID: d.ID, dinnerName: d.Name}
+		for _, ing := range ings {
+			it, err := item(ing, manual)
+			if err != nil {
+				return nil, nil, fmt.Errorf("shopping: recipe %s: %w", recipe.ID, err)
+			}
+			g.items = append(g.items, it)
+		}
+		groups = append(groups, g)
+	}
+	return groups, skipped, nil
+}
+
+// item is the item for ingredient ing of a recipe entered by hand
+// (manual) or fetched.
+func item(ing db.RecipeIngredient, manual bool) (wantItem, error) {
+	if manual {
+		return wantItem{name: ing.RawText}, nil
+	}
+	if !ing.Name.Valid || ing.Name.String == "" {
+		return wantItem{}, fmt.Errorf("ingredient %d (%q) has no normalized name", ing.Position+1, ing.RawText)
+	}
+	var parts []string
+	for _, p := range []sql.NullString{ing.Qty, ing.Unit} {
+		if p.Valid && p.String != "" {
+			parts = append(parts, p.String)
+		}
+	}
+	qty := strings.Join(parts, " ")
+	return wantItem{name: ing.Name.String, qty: sql.NullString{String: qty, Valid: qty != ""}}, nil
+}
+
+// itemKey is what makes an item the same item across a remake.
+type itemKey struct {
+	dinnerID, name string
+}
+
+// groupKey is what makes a group the same group across a remake.
+type groupKey struct {
+	date, dinnerID string
+}
+
+// reconcile makes the groups and items of list listID those of want, as
+// Generate says, and returns them.
+func reconcile(ctx context.Context, q *db.Queries, listID string, want []wantGroup, now string) ([]Group, error) {
+	oldGroups, err := q.ListShoppingGroups(ctx, listID)
+	if err != nil {
+		return nil, fmt.Errorf("shopping: read groups: %w", err)
+	}
+	oldItems, err := q.ListShoppingItems(ctx, listID)
+	if err != nil {
+		return nil, fmt.Errorf("shopping: read items: %w", err)
+	}
+	groupsByKey := make(map[groupKey]db.ShoppingGroup, len(oldGroups))
+	for _, g := range oldGroups {
+		groupsByKey[groupKey{g.Date, g.DinnerID}] = g
+	}
+	// itemsByKey holds each key's items in list order, so the nth item a
+	// dinner lists under a name matches its nth one before.
+	itemsByKey := make(map[itemKey][]db.ShoppingItem)
+	for _, r := range oldItems {
+		k := itemKey{r.DinnerID, r.ShoppingItem.Name}
+		itemsByKey[k] = append(itemsByKey[k], r.ShoppingItem)
+	}
+	kept := make(map[string]bool) // ids of the groups and items kept
+
+	groups := make([]Group, 0, len(want))
+	for gi, w := range want {
+		g := Group{DinnerID: w.dinnerID, DinnerName: w.dinnerName, Date: w.date, Position: gi}
+		if old, ok := groupsByKey[groupKey{w.date, w.dinnerID}]; ok {
+			g.ID = old.ID
+			kept[old.ID] = true
+			if err := q.MoveShoppingGroup(ctx, db.MoveShoppingGroupParams{Position: int64(gi), UpdatedAt: now, ID: g.ID}); err != nil {
+				return nil, fmt.Errorf("shopping: move group %s: %w", g.ID, err)
+			}
+		} else {
+			g.ID = store.NewID()
+			if err := q.CreateShoppingGroup(ctx, db.CreateShoppingGroupParams{
+				ID: g.ID, ListID: listID, DinnerID: w.dinnerID, Date: w.date, Position: int64(gi),
+				CreatedAt: now, UpdatedAt: now,
+			}); err != nil {
+				return nil, fmt.Errorf("shopping: store group of %s: %w", w.date, err)
+			}
+		}
+		for ii, wi := range w.items {
+			it := Item{Name: wi.name, Qty: nullString(wi.qty), Needed: true, Position: ii}
+			k := itemKey{w.dinnerID, wi.name}
+			if same := itemsByKey[k]; len(same) > 0 {
+				old := same[0]
+				itemsByKey[k] = same[1:]
+				it.ID, it.Needed = old.ID, old.Needed == 1
+				kept[old.ID] = true
+				if err := q.MoveShoppingItem(ctx, db.MoveShoppingItemParams{
+					GroupID: g.ID, Qty: wi.qty, Position: int64(ii), UpdatedAt: now, ID: it.ID,
+				}); err != nil {
+					return nil, fmt.Errorf("shopping: move item %s: %w", it.ID, err)
+				}
+			} else {
+				it.ID = store.NewID()
+				if err := q.CreateShoppingItem(ctx, db.CreateShoppingItemParams{
+					ID: it.ID, GroupID: g.ID, Name: wi.name, Qty: wi.qty, Position: int64(ii),
+					CreatedAt: now, UpdatedAt: now,
+				}); err != nil {
+					return nil, fmt.Errorf("shopping: store item %q of %s: %w", wi.name, w.date, err)
+				}
+			}
+			g.Items = append(g.Items, it)
+		}
+		groups = append(groups, g)
+	}
+
+	// Items first: a group is removed only once it is empty.
+	for _, r := range oldItems {
+		if !kept[r.ShoppingItem.ID] {
+			if err := q.DeleteShoppingItem(ctx, r.ShoppingItem.ID); err != nil {
+				return nil, fmt.Errorf("shopping: remove item %s: %w", r.ShoppingItem.ID, err)
+			}
+		}
+	}
+	for _, g := range oldGroups {
+		if !kept[g.ID] {
+			if err := q.DeleteShoppingGroup(ctx, g.ID); err != nil {
+				return nil, fmt.Errorf("shopping: remove group %s: %w", g.ID, err)
+			}
+		}
+	}
+	return groups, nil
+}
+
+func nullString(s sql.NullString) *string {
+	if !s.Valid {
+		return nil
+	}
+	return &s.String
+}