feat: daily vani

internal/repository/vani_repo.go

@@ -0,0 +1,165 @@
+package repository
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/prabhupadasays/spsays-bff/internal/model"
+	"go.mongodb.org/mongo-driver/v2/bson"
+	"go.mongodb.org/mongo-driver/v2/mongo"
+)
+
+// VaniRepo backs "Vāṇī of the Day": the daily pick lives in Postgres
+// (vani_of_the_day) while the candidate content is sampled from Mongo (the
+// verses / prose_chapters / transcriptions collections).
+type VaniRepo struct {
+	pg    *Postgres
+	mongo *MongoDB
+}
+
+func NewVaniRepo(pg *Postgres, m *MongoDB) *VaniRepo {
+	return &VaniRepo{pg: pg, mongo: m}
+}
+
+// --- Postgres: the per-day record ---
+
+// GetForDay returns the pick stored for the given UTC day, or (nil, nil) when
+// nothing has been chosen yet.
+func (r *VaniRepo) GetForDay(ctx context.Context, day time.Time) (*model.VaniPick, error) {
+	var kind, refID string
+	var payload []byte
+	err := r.pg.Pool.QueryRow(ctx,
+		`SELECT kind, ref_id, payload FROM vani_of_the_day WHERE day = $1`, day,
+	).Scan(&kind, &refID, &payload)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("get vani for day: %w", err)
+	}
+	var p model.VaniPayload
+	if err := json.Unmarshal(payload, &p); err != nil {
+		return nil, fmt.Errorf("decode vani payload: %w", err)
+	}
+	return &model.VaniPick{Day: day, Kind: kind, RefID: refID, Payload: p}, nil
+}
+
+// RecentRefIDs returns the ref_ids chosen on or after `since` — the 90-day
+// exclusion set for the picker.
+func (r *VaniRepo) RecentRefIDs(ctx context.Context, since time.Time) ([]string, error) {
+	rows, err := r.pg.Pool.Query(ctx,
+		`SELECT ref_id FROM vani_of_the_day WHERE day >= $1`, since)
+	if err != nil {
+		return nil, fmt.Errorf("recent vani ref ids: %w", err)
+	}
+	defer rows.Close()
+	var out []string
+	for rows.Next() {
+		var id string
+		if err := rows.Scan(&id); err != nil {
+			return nil, err
+		}
+		out = append(out, id)
+	}
+	return out, rows.Err()
+}
+
+// Insert stores the day's pick, ignoring a race where another request already
+// wrote today's (ON CONFLICT (day) DO NOTHING). Callers re-read GetForDay to
+// get the authoritative row.
+func (r *VaniRepo) Insert(ctx context.Context, pick *model.VaniPick) error {
+	b, err := json.Marshal(pick.Payload)
+	if err != nil {
+		return err
+	}
+	_, err = r.pg.Pool.Exec(ctx,
+		`INSERT INTO vani_of_the_day (day, kind, ref_id, payload)
+		 VALUES ($1, $2, $3, $4::jsonb)
+		 ON CONFLICT (day) DO NOTHING`,
+		pick.Day, pick.Kind, pick.RefID, b)
+	if err != nil {
+		return fmt.Errorf("insert vani pick: %w", err)
+	}
+	return nil
+}
+
+// --- Mongo: random candidate sampling ---
+
+// excludeIDs turns hex _id strings into a $nin ObjectID array.
+func excludeIDs(hexes []string) bson.A {
+	arr := bson.A{}
+	for _, h := range hexes {
+		if oid, err := bson.ObjectIDFromHex(h); err == nil {
+			arr = append(arr, oid)
+		}
+	}
+	return arr
+}
+
+func (r *VaniRepo) sampleOne(ctx context.Context, coll string, match bson.D, out interface{}) (bool, error) {
+	cur, err := r.mongo.Collection(coll).Aggregate(ctx, mongo.Pipeline{
+		bson.D{{Key: "$match", Value: match}},
+		bson.D{{Key: "$sample", Value: bson.D{{Key: "size", Value: 1}}}},
+	})
+	if err != nil {
+		return false, fmt.Errorf("sample %s: %w", coll, err)
+	}
+	defer cur.Close(ctx)
+	if cur.Next(ctx) {
+		if err := cur.Decode(out); err != nil {
+			return false, err
+		}
+		return true, nil
+	}
+	return false, cur.Err()
+}
+
+// SampleVerse returns a random verse with a translation, excluding the given
+// _id hexes. Returns nil when nothing matches.
+func (r *VaniRepo) SampleVerse(ctx context.Context, excludeHex []string) (*VerseDoc, error) {
+	match := bson.D{
+		{Key: "_id", Value: bson.D{{Key: "$nin", Value: excludeIDs(excludeHex)}}},
+		{Key: "translation", Value: bson.D{{Key: "$exists", Value: true}, {Key: "$ne", Value: ""}}},
+	}
+	var d VerseDoc
+	ok, err := r.sampleOne(ctx, "verses", match, &d)
+	if err != nil || !ok {
+		return nil, err
+	}
+	return &d, nil
+}
+
+// SampleProse returns a random prose chapter with body text, excluding the
+// given _id hexes.
+func (r *VaniRepo) SampleProse(ctx context.Context, excludeHex []string) (*ProseChapterDoc, error) {
+	match := bson.D{
+		{Key: "_id", Value: bson.D{{Key: "$nin", Value: excludeIDs(excludeHex)}}},
+		{Key: "paragraphs.0", Value: bson.D{{Key: "$exists", Value: true}}},
+	}
+	var d ProseChapterDoc
+	ok, err := r.sampleOne(ctx, "prose_chapters", match, &d)
+	if err != nil || !ok {
+		return nil, err
+	}
+	return &d, nil
+}
+
+// SampleTranscript returns a random published transcript with content,
+// excluding the given _id hexes.
+func (r *VaniRepo) SampleTranscript(ctx context.Context, excludeHex []string) (*TranscriptionDoc, error) {
+	match := bson.D{
+		{Key: "_id", Value: bson.D{{Key: "$nin", Value: excludeIDs(excludeHex)}}},
+		{Key: "isPublished", Value: true},
+		{Key: "content.0", Value: bson.D{{Key: "$exists", Value: true}}},
+	}
+	var d TranscriptionDoc
+	ok, err := r.sampleOne(ctx, "transcriptions", match, &d)
+	if err != nil || !ok {
+		return nil, err
+	}
+	return &d, nil
+}