Feature 10: Recipe grounding and photos (#78)

Co-authored-by: dev_agent <dev_agent@cubecraftlabs.com>

internal/recipes/rank.go

@@ -0,0 +1,155 @@
+package recipes
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sort"
+	"sync"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/harness"
+)
+
+// RankDepth is how many of the top search candidates Rank fetches and
+// extracts.
+const RankDepth = 5
+
+var (
+	// ErrNoIngredients rejects a candidate whose recipe lists no
+	// ingredients.
+	ErrNoIngredients = errors.New("recipes: recipe has no ingredients")
+	// ErrNoImage rejects a candidate whose recipe has no image.
+	ErrNoImage = errors.New("recipes: recipe has no image")
+	// ErrNoUsableRecipe is returned when Rank ranks no candidate; it is
+	// joined with each candidate's reason.
+	ErrNoUsableRecipe = errors.New("recipes: no candidate holds a usable recipe")
+	// ErrCandidatesUnranked is returned, alongside the ranked candidates,
+	// when Rank ranks some candidates but not all; it is joined with each
+	// unranked candidate's reason.
+	ErrCandidatesUnranked = errors.New("recipes: some candidates were not ranked")
+)
+
+// PageFetcher fetches a candidate's page; *Fetcher satisfies it.
+type PageFetcher interface {
+	Fetch(ctx context.Context, rawURL string) (Page, error)
+}
+
+// Ranked is a candidate whose page held a usable recipe, with its score.
+type Ranked struct {
+	Candidate Candidate
+	Recipe    Recipe
+	// Score is the token similarity of the recipe's title to the dish name
+	// (0 to 1, harness.Similarity) plus a quarter for each of ingredients,
+	// image, steps and total minutes present (0 to 1).
+	Score float64
+}
+
+// Rank fetches and extracts the first RankDepth candidates concurrently and
+// returns those whose recipe is usable — it has ingredients and an image,
+// and any total time it gives is positive — highest Score first; equal
+// scores keep search order.
+//
+// Every candidate that is not ranked — its fetch failed, its page holds no
+// valid recipe, or the recipe is not usable — is reported, never dropped
+// silently: when some are ranked the error is
+// ErrCandidatesUnranked, returned together with the ranked ones; when none
+// are it is ErrNoUsableRecipe with no results. Either is joined with each
+// unranked candidate's URL and reason. A cancelled ctx returns only its
+// error.
+func Rank(ctx context.Context, f PageFetcher, dish string, cands []Candidate) ([]Ranked, error) {
+	return rank(ctx, dish, cands, func(ctx context.Context, c Candidate) (Recipe, error) {
+		return fetchRecipe(ctx, f, c.URL)
+	})
+}
+
+// rank is Rank with each candidate's recipe got by load rather than always
+// fetched.
+func rank(ctx context.Context, dish string, cands []Candidate, load func(context.Context, Candidate) (Recipe, error)) ([]Ranked, error) {
+	if len(cands) > RankDepth {
+		cands = cands[:RankDepth]
+	}
+	type outcome struct {
+		ranked Ranked
+		err    error
+	}
+	outcomes := make([]outcome, len(cands))
+	var wg sync.WaitGroup
+	for i, c := range cands {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			r, err := rankOne(ctx, load, dish, c)
+			outcomes[i] = outcome{r, err}
+		}()
+	}
+	wg.Wait()
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+
+	var ranked []Ranked
+	var reasons []error
+	for i, o := range outcomes {
+		if o.err != nil {
+			reasons = append(reasons, fmt.Errorf("%s: %w", cands[i].URL, o.err))
+			continue
+		}
+		ranked = append(ranked, o.ranked)
+	}
+	if len(ranked) == 0 {
+		return nil, errors.Join(append([]error{ErrNoUsableRecipe}, reasons...)...)
+	}
+	sort.SliceStable(ranked, func(a, b int) bool { return ranked[a].Score > ranked[b].Score })
+	if len(reasons) > 0 {
+		return ranked, errors.Join(append([]error{ErrCandidatesUnranked}, reasons...)...)
+	}
+	return ranked, nil
+}
+
+// rankOne loads and scores one candidate's recipe, or says why it is
+// rejected.
+func rankOne(ctx context.Context, load func(context.Context, Candidate) (Recipe, error), dish string, c Candidate) (Ranked, error) {
+	r, err := load(ctx, c)
+	if err != nil {
+		return Ranked{}, err
+	}
+	if err := usable(r); err != nil {
+		return Ranked{}, err
+	}
+	return Ranked{Candidate: c, Recipe: r, Score: harness.Similarity(r.Title, dish) + completeness(r)}, nil
+}
+
+// fetchRecipe fetches the page at rawURL and extracts its recipe.
+func fetchRecipe(ctx context.Context, f PageFetcher, rawURL string) (Recipe, error) {
+	page, err := f.Fetch(ctx, rawURL)
+	if err != nil {
+		return Recipe{}, err
+	}
+	return Extract(page.Body, page.URL)
+}
+
+// usable says why r cannot ground a dish: it has no ingredients or no
+// image, or a total time that is not positive.
+func usable(r Recipe) error {
+	switch {
+	case len(r.Ingredients) == 0:
+		return ErrNoIngredients
+	case r.ImageURL == "":
+		return ErrNoImage
+	case r.TotalMinutes != nil && *r.TotalMinutes <= 0:
+		return ErrTotalTimeNotPositive
+	}
+	return nil
+}
+
+// completeness is a quarter for each of ingredients, image, steps and total
+// minutes the recipe has.
+func completeness(r Recipe) float64 {
+	score := 0.0
+	for _, present := range []bool{len(r.Ingredients) > 0, r.ImageURL != "", len(r.Steps) > 0, r.TotalMinutes != nil} {
+		if present {
+			score += 0.25
+		}
+	}
+	return score
+}