// Package store is the read-only data access layer for the OpenGoods API.
// It only issues SELECT queries; all writes happen in the Python ingestion path.
package store

import (
	"context"
	"encoding/json"
	"errors"
	"strconv"
	"strings"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

// ErrNotFound is returned when a requested row does not exist.
var ErrNotFound = errors.New("not found")

// Store wraps a PostgreSQL connection pool.
type Store struct {
	pool *pgxpool.Pool
}

// New constructs a Store from an existing pgx pool.
func New(pool *pgxpool.Pool) *Store {
	return &Store{pool: pool}
}

// Ping verifies database connectivity.
func (s *Store) Ping(ctx context.Context) error {
	return s.pool.Ping(ctx)
}

// PublicStats summarizes the public catalog for the homepage.
type PublicStats struct {
	Total     int     `json:"total"`
	Qualified int     `json:"qualified"`
	MinScore  float64 `json:"min_score"`
}

// Stats returns active-product totals and the number of qualified records whose
// quality_score meets minScore.
func (s *Store) Stats(ctx context.Context, minScore float64) (PublicStats, error) {
	st := PublicStats{MinScore: minScore}
	err := s.pool.QueryRow(ctx, `
SELECT count(*) FILTER (WHERE status = 'active'),
       count(*) FILTER (WHERE status = 'active' AND quality_score >= $1)
FROM product`, minScore).Scan(&st.Total, &st.Qualified)
	return st, err
}

// Barcode is one GS1 trade item number attached to a product.
type Barcode struct {
	GTIN      string  `json:"gtin"`
	GTINType  string  `json:"gtin_type"`
	PackLevel string  `json:"pack_level"`
	Region    *string `json:"region"`
	IsPrimary bool    `json:"is_primary"`
}

// ProductSpec is one labeled spec line for a non-food product, rendered from
// the product's attributes JSONB against its archive kind's field template.
type ProductSpec struct {
	Key   string `json:"key"`
	Label string `json:"label"`
	Value string `json:"value"`
	Unit  string `json:"unit,omitempty"`
}

// Product is the full public view of a product.
type Product struct {
	ID              string         `json:"id"`
	GTIN            *string        `json:"gtin"`
	Name            string         `json:"name"`
	Brand           *string        `json:"brand"`
	CategoryPath    *string        `json:"category_path"`
	GPCBrickCode    *string        `json:"gpc_brick_code"`
	ArchiveKind     string         `json:"archive_kind"`
	NetContentValue *float64       `json:"net_content_value"`
	NetContentUnit  *string        `json:"net_content_unit"`
	CountryOfOrigin *string        `json:"country_of_origin"`
	QualityScore    float64        `json:"quality_score"`
	Barcodes        []Barcode      `json:"barcodes"`
	Specs           []ProductSpec  `json:"specs,omitempty"`
	Nutriments      map[string]any `json:"nutriments,omitempty"`
	NutritionBasis  *string        `json:"nutrition_basis,omitempty"`
	NutriScore      *string        `json:"nutri_score,omitempty"`
	Ingredients     *string        `json:"ingredients_text,omitempty"`
	Allergens       []string       `json:"allergens,omitempty"`
	Additives       []string       `json:"additives,omitempty"`
}

// ProductBarcodes returns every barcode attached to a product, primary first.
func (s *Store) ProductBarcodes(ctx context.Context, productID string) ([]Barcode, error) {
	rows, err := s.pool.Query(ctx,
		`SELECT gtin, gtin_type, pack_level, region, is_primary
		 FROM product_barcode WHERE product_id = $1
		 ORDER BY is_primary DESC, gtin`, productID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []Barcode{}
	for rows.Next() {
		var b Barcode
		if err := rows.Scan(&b.GTIN, &b.GTINType, &b.PackLevel, &b.Region, &b.IsPrimary); err != nil {
			return nil, err
		}
		out = append(out, b)
	}
	return out, rows.Err()
}

// ProductSummary is a lightweight row used in search/listing responses.
type ProductSummary struct {
	ID           string   `json:"id"`
	GTIN         *string  `json:"gtin"`
	Name         string   `json:"name"`
	Brand        *string  `json:"brand"`
	CategoryPath *string  `json:"category_path"`
	Country      *string  `json:"country_of_origin"`
	QualityScore float64  `json:"quality_score"`
	Score        *float64 `json:"score,omitempty"`
}

// SearchFilters bundles the optional filters accepted by SearchProducts.
type SearchFilters struct {
	Query    string // fuzzy name / barcode query
	Category string // ltree path; matches the subtree
	Brand    string // fuzzy brand name
	Country  string // country_of_origin prefix (case-insensitive)
}

const productSelect = `
SELECT p.id, p.gtin, p.name, b.name, c.path::text, p.gpc_brick_code,
       COALESCE(c.archive_kind, 'generic'), p.attributes,
       p.net_content_value, p.net_content_unit, p.country_of_origin, p.quality_score,
       f.nutriments, f.nutrition_basis, f.nutri_score, f.ingredients_text,
       f.allergens, f.additives
FROM product p
LEFT JOIN brand b ON b.id = p.brand_id
LEFT JOIN category c ON c.id = p.category_id
LEFT JOIN food_detail f ON f.product_id = p.id
`

func scanProduct(row pgx.Row) (*Product, []byte, error) {
	var p Product
	var attributes []byte
	err := row.Scan(
		&p.ID, &p.GTIN, &p.Name, &p.Brand, &p.CategoryPath, &p.GPCBrickCode,
		&p.ArchiveKind, &attributes,
		&p.NetContentValue, &p.NetContentUnit, &p.CountryOfOrigin, &p.QualityScore,
		&p.Nutriments, &p.NutritionBasis, &p.NutriScore, &p.Ingredients,
		&p.Allergens, &p.Additives,
	)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, nil, ErrNotFound
	}
	if err != nil {
		return nil, nil, err
	}
	return &p, attributes, nil
}

// buildSpecs renders the labeled, ordered spec list for a non-food product from
// its attributes JSONB against its archive kind's field template.
func (s *Store) buildSpecs(ctx context.Context, kind string, attributes []byte) ([]ProductSpec, error) {
	if kind == "" || kind == "food" || len(attributes) == 0 {
		return nil, nil
	}
	attrs := map[string]any{}
	if err := json.Unmarshal(attributes, &attrs); err != nil || len(attrs) == 0 {
		return nil, nil
	}
	rows, err := s.pool.Query(ctx,
		"SELECT field_key, label_zh, COALESCE(unit, '') FROM kind_field WHERE kind = $1 ORDER BY sort_order, field_key", kind)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	specs := []ProductSpec{}
	for rows.Next() {
		var key, label, unit string
		if err := rows.Scan(&key, &label, &unit); err != nil {
			return nil, err
		}
		v, ok := attrs[key]
		if !ok || v == nil {
			continue
		}
		val := stringifyAttr(v)
		if val == "" {
			continue
		}
		specs = append(specs, ProductSpec{Key: key, Label: label, Value: val, Unit: unit})
	}
	return specs, rows.Err()
}

// stringifyAttr renders a JSON attribute value as display text.
func stringifyAttr(v any) string {
	switch t := v.(type) {
	case string:
		return t
	case float64:
		return strconv.FormatFloat(t, 'f', -1, 64)
	case bool:
		if t {
			return "是"
		}
		return "否"
	case []any:
		parts := make([]string, 0, len(t))
		for _, e := range t {
			parts = append(parts, stringifyAttr(e))
		}
		return strings.Join(parts, "、")
	default:
		return ""
	}
}

// ProductByGTIN looks up an active product by any of its barcodes.
func (s *Store) ProductByGTIN(ctx context.Context, gtin string) (*Product, error) {
	row := s.pool.QueryRow(ctx, productSelect+`
 WHERE p.status = 'active'
   AND (p.gtin = $1 OR EXISTS (
         SELECT 1 FROM product_barcode pb
         WHERE pb.product_id = p.id AND pb.gtin = $1))
 LIMIT 1`, gtin)
	p, attrs, err := scanProduct(row)
	if err != nil {
		return nil, err
	}
	if p.Barcodes, err = s.ProductBarcodes(ctx, p.ID); err != nil {
		return nil, err
	}
	if p.Specs, err = s.buildSpecs(ctx, p.ArchiveKind, attrs); err != nil {
		return nil, err
	}
	return p, nil
}

// ProductByID looks up a product by its UUID.
func (s *Store) ProductByID(ctx context.Context, id string) (*Product, error) {
	row := s.pool.QueryRow(ctx, productSelect+" WHERE p.id = $1", id)
	p, attrs, err := scanProduct(row)
	if err != nil {
		return nil, err
	}
	if p.Barcodes, err = s.ProductBarcodes(ctx, p.ID); err != nil {
		return nil, err
	}
	if p.Specs, err = s.buildSpecs(ctx, p.ArchiveKind, attrs); err != nil {
		return nil, err
	}
	return p, nil
}

// fuzzyThreshold is the minimum word_similarity for a name to be considered a
// fuzzy match. ~0.42 tolerates common typos (e.g. "choclate"→"Chocolate")
// without returning unrelated products.
const fuzzyThreshold = "0.42"

// SearchProducts runs a trigram-fuzzy name search with optional category /
// brand / country filters. When a query is present, matching is inclusive
// (substring OR trigram-similar OR barcode), and results are ranked by name
// similarity blended with quality_score so the best, most-complete records
// surface first. Without a query, results are ordered by quality_score.
func (s *Store) SearchProducts(ctx context.Context, f SearchFilters, limit, offset int) ([]ProductSummary, int, error) {
	args := []any{}
	where := "WHERE p.status = 'active'"

	qIdx := 0
	if f.Query != "" {
		args = append(args, f.Query)
		qIdx = len(args)
		q := "$" + strconv.Itoa(qIdx)
		where += ` AND (p.name ILIKE '%' || ` + q + ` || '%'
			OR word_similarity(` + q + `, p.name) >= ` + fuzzyThreshold + `
			OR EXISTS (SELECT 1 FROM product_barcode pb
			           WHERE pb.product_id = p.id AND pb.gtin ILIKE '%' || ` + q + ` || '%'))`
	}
	if f.Category != "" {
		args = append(args, f.Category)
		where += " AND c.path <@ $" + strconv.Itoa(len(args)) + "::ltree"
	}
	if f.Brand != "" {
		args = append(args, f.Brand)
		where += " AND b.name ILIKE '%' || $" + strconv.Itoa(len(args)) + " || '%'"
	}
	if f.Country != "" {
		args = append(args, f.Country)
		where += " AND p.country_of_origin ILIKE $" + strconv.Itoa(len(args)) + " || '%'"
	}

	from := `FROM product p
LEFT JOIN brand b ON b.id = p.brand_id
LEFT JOIN category c ON c.id = p.category_id `

	var total int
	if err := s.pool.QueryRow(ctx, "SELECT count(*) "+from+where, args...).Scan(&total); err != nil {
		return nil, 0, err
	}

	// Ranking: when querying, similarity drives order, multiplied by a
	// quality factor floored at 0.5 so low-quality records aren't zeroed out.
	scoreExpr := "NULL::real"
	orderBy := "p.quality_score DESC, p.name"
	if f.Query != "" {
		q := "$" + strconv.Itoa(qIdx)
		scoreExpr = "word_similarity(" + q + ", p.name)"
		orderBy = scoreExpr + " * (0.5 + p.quality_score) DESC, p.quality_score DESC, p.name"
	}

	args = append(args, limit, offset)
	listSQL := "SELECT p.id, p.gtin, p.name, b.name, c.path::text, p.country_of_origin, p.quality_score, " +
		scoreExpr + " AS score " + from + where +
		" ORDER BY " + orderBy +
		" LIMIT $" + strconv.Itoa(len(args)-1) + " OFFSET $" + strconv.Itoa(len(args))

	rows, err := s.pool.Query(ctx, listSQL, args...)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	out := []ProductSummary{}
	for rows.Next() {
		var ps ProductSummary
		if err := rows.Scan(&ps.ID, &ps.GTIN, &ps.Name, &ps.Brand, &ps.CategoryPath,
			&ps.Country, &ps.QualityScore, &ps.Score); err != nil {
			return nil, 0, err
		}
		out = append(out, ps)
	}
	return out, total, rows.Err()
}

// Nutriments returns just the nutrition payload for a product.
type Nutriments struct {
	ProductID  string         `json:"product_id"`
	Basis      *string        `json:"basis"`
	NutriScore *string        `json:"nutri_score"`
	Values     map[string]any `json:"values"`
}

// Nutriments fetches the nutrition facts of a product.
func (s *Store) Nutriments(ctx context.Context, id string) (*Nutriments, error) {
	var n Nutriments
	n.ProductID = id
	err := s.pool.QueryRow(ctx,
		"SELECT nutriments, nutrition_basis, nutri_score FROM food_detail WHERE product_id = $1", id,
	).Scan(&n.Values, &n.Basis, &n.NutriScore)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	return &n, nil
}

// MSRP is an official suggested retail price snapshot (never a purchase link).
type MSRP struct {
	Amount        float64 `json:"amount"`
	Currency      string  `json:"currency"`
	Region        string  `json:"region"`
	EffectiveDate *string `json:"effective_date"`
	SourceURL     *string `json:"source_url"`
	Note          *string `json:"note"`
}

// ListMSRP returns all MSRP snapshots for a product.
func (s *Store) ListMSRP(ctx context.Context, id string) ([]MSRP, error) {
	rows, err := s.pool.Query(ctx,
		`SELECT amount, currency, region, effective_date::text, source_url, note
		 FROM product_msrp WHERE product_id = $1 ORDER BY effective_date DESC NULLS LAST`, id)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []MSRP{}
	for rows.Next() {
		var m MSRP
		if err := rows.Scan(&m.Amount, &m.Currency, &m.Region, &m.EffectiveDate, &m.SourceURL, &m.Note); err != nil {
			return nil, err
		}
		out = append(out, m)
	}
	return out, rows.Err()
}

// Brand is a public brand entry.
type Brand struct {
	ID   string `json:"id"`
	Name string `json:"name"`
}

// ListBrands returns brands ordered by name.
func (s *Store) ListBrands(ctx context.Context, limit, offset int) ([]Brand, int, error) {
	var total int
	if err := s.pool.QueryRow(ctx, "SELECT count(*) FROM brand").Scan(&total); err != nil {
		return nil, 0, err
	}
	rows, err := s.pool.Query(ctx, "SELECT id, name FROM brand ORDER BY name LIMIT $1 OFFSET $2", limit, offset)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()
	out := []Brand{}
	for rows.Next() {
		var b Brand
		if err := rows.Scan(&b.ID, &b.Name); err != nil {
			return nil, 0, err
		}
		out = append(out, b)
	}
	return out, total, rows.Err()
}

// Category is a node in the self-built category tree.
type Category struct {
	ID           string  `json:"id"`
	NameZH       string  `json:"name_zh"`
	NameEN       *string `json:"name_en"`
	Path         string  `json:"path"`
	GPCBrickCode *string `json:"gpc_brick_code"`
	Level        int     `json:"level"`
}

// ListCategories returns the full category tree ordered by path.
func (s *Store) ListCategories(ctx context.Context) ([]Category, error) {
	rows, err := s.pool.Query(ctx,
		"SELECT id, name_zh, name_en, path::text, gpc_brick_code, level FROM category ORDER BY path")
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []Category{}
	for rows.Next() {
		var c Category
		if err := rows.Scan(&c.ID, &c.NameZH, &c.NameEN, &c.Path, &c.GPCBrickCode, &c.Level); err != nil {
			return nil, err
		}
		out = append(out, c)
	}
	return out, rows.Err()
}

// APIKey is the minimal metadata the public API needs to authorize a caller.
type APIKey struct {
	ID              string
	Name            string
	RateLimitPerMin int
	QuotaTotal      int64
}

// APIKeyByHash returns the active (non-revoked) key matching a SHA-256 hash,
// or ErrNotFound if no such active key exists.
func (s *Store) APIKeyByHash(ctx context.Context, hash string) (*APIKey, error) {
	var k APIKey
	err := s.pool.QueryRow(ctx,
		`SELECT id, name, rate_limit_per_min, quota_total
		 FROM api_key WHERE key_hash = $1 AND revoked_at IS NULL`, hash,
	).Scan(&k.ID, &k.Name, &k.RateLimitPerMin, &k.QuotaTotal)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	return &k, nil
}

// Source describes a data source with its license and trust weight.
type Source struct {
	ID          string  `json:"id"`
	Name        string  `json:"name"`
	Homepage    *string `json:"homepage"`
	License     *string `json:"license"`
	TrustWeight float64 `json:"trust_weight"`
}

// SourceByID fetches a single data source.
func (s *Store) SourceByID(ctx context.Context, id string) (*Source, error) {
	var src Source
	err := s.pool.QueryRow(ctx,
		"SELECT id, name, homepage, license, trust_weight FROM source WHERE id = $1", id,
	).Scan(&src.ID, &src.Name, &src.Homepage, &src.License, &src.TrustWeight)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	return &src, nil
}