package adminstore

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

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

// ProductInput is the editable payload accepted from the admin UI.
type ProductInput struct {
	GTIN            *string        `json:"gtin"`
	Name            string         `json:"name"`
	BrandID         *string        `json:"brand_id"`
	BrandName       *string        `json:"brand_name"`
	CategoryID      *string        `json:"category_id"`
	NetContentValue *float64       `json:"net_content_value"`
	NetContentUnit  *string        `json:"net_content_unit"`
	CountryOfOrigin *string        `json:"country_of_origin"`
	Status          string         `json:"status"`
	IngredientsText *string        `json:"ingredients_text"`
	Allergens       []string       `json:"allergens"`
	Additives       []string       `json:"additives"`
	Nutriments      map[string]any `json:"nutriments"`
	NutritionBasis  *string        `json:"nutrition_basis"`
	ServingSize     *string        `json:"serving_size"`
	NutriScore      *string        `json:"nutri_score"`
}

func normBrand(name string) string { return strings.Join(strings.Fields(strings.ToLower(name)), " ") }

func (s *Store) ensureBrand(ctx context.Context, tx pgx.Tx, name string) (string, error) {
	var id string
	err := tx.QueryRow(ctx, `
INSERT INTO brand (name, normalized_name) VALUES ($1, $2)
ON CONFLICT (normalized_name) DO UPDATE SET name = brand.name
RETURNING id`, name, normBrand(name)).Scan(&id)
	return id, err
}

func (s *Store) manualSourceID(ctx context.Context, tx pgx.Tx) (string, error) {
	var id string
	err := tx.QueryRow(ctx, "SELECT id FROM source WHERE name = 'manual'").Scan(&id)
	return id, err
}

// netCanonical converts value+unit to the canonical base unit via the unit table.
func (s *Store) netCanonical(ctx context.Context, tx pgx.Tx, value *float64, unit *string) (*float64, error) {
	if value == nil || unit == nil || *unit == "" {
		return nil, nil
	}
	var factor *float64
	err := tx.QueryRow(ctx, "SELECT to_canonical_factor FROM unit WHERE code = $1", *unit).Scan(&factor)
	if errors.Is(err, pgx.ErrNoRows) || factor == nil {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	c := *value * *factor
	return &c, nil
}

// UpdateProduct applies an edit, records provenance + audit, and recomputes quality.
func (s *Store) UpdateProduct(ctx context.Context, id, actor string, in ProductInput) (*ProductDetail, error) {
	before, err := s.GetProduct(ctx, id)
	if err != nil {
		return nil, err
	}

	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback(ctx)

	// Resolve brand (create-by-name takes precedence over id).
	brandID := in.BrandID
	if in.BrandName != nil && strings.TrimSpace(*in.BrandName) != "" {
		bid, err := s.ensureBrand(ctx, tx, strings.TrimSpace(*in.BrandName))
		if err != nil {
			return nil, err
		}
		brandID = &bid
	}

	// Resolve category gpc brick code.
	var gpc *string
	if in.CategoryID != nil && *in.CategoryID != "" {
		if err := tx.QueryRow(ctx, "SELECT gpc_brick_code FROM category WHERE id = $1", *in.CategoryID).Scan(&gpc); err != nil && !errors.Is(err, pgx.ErrNoRows) {
			return nil, err
		}
	}

	canonical, err := s.netCanonical(ctx, tx, in.NetContentValue, in.NetContentUnit)
	if err != nil {
		return nil, err
	}

	status := in.Status
	if status == "" {
		status = before.Status
	}

	_, err = tx.Exec(ctx, `
UPDATE product SET gtin=$1, name=$2, brand_id=$3, category_id=$4, gpc_brick_code=$5,
   net_content_value=$6, net_content_unit=$7, net_content_canonical=$8,
   country_of_origin=$9, status=$10
WHERE id=$11`,
		in.GTIN, in.Name, brandID, in.CategoryID, gpc,
		in.NetContentValue, in.NetContentUnit, canonical,
		in.CountryOfOrigin, status, id)
	if err != nil {
		return nil, err
	}

	var nutriJSON []byte
	if in.Nutriments != nil {
		nutriJSON, _ = json.Marshal(in.Nutriments)
	}
	allergens := in.Allergens
	if allergens == nil {
		allergens = []string{}
	}
	additives := in.Additives
	if additives == nil {
		additives = []string{}
	}
	_, err = tx.Exec(ctx, `
INSERT INTO food_detail (product_id, ingredients_text, allergens, additives,
   nutriments, nutrition_basis, serving_size, nutri_score)
VALUES ($1,$2,$3,$4,$5,$6,$7,$8)
ON CONFLICT (product_id) DO UPDATE SET
   ingredients_text=EXCLUDED.ingredients_text,
   allergens=EXCLUDED.allergens,
   additives=EXCLUDED.additives,
   nutriments=EXCLUDED.nutriments,
   nutrition_basis=EXCLUDED.nutrition_basis,
   serving_size=EXCLUDED.serving_size,
   nutri_score=EXCLUDED.nutri_score`,
		id, in.IngredientsText, allergens, additives,
		nutriJSON, in.NutritionBasis, in.ServingSize, in.NutriScore)
	if err != nil {
		return nil, err
	}

	if _, err := s.recomputeQualityTx(ctx, tx, id); err != nil {
		return nil, err
	}

	if err := tx.Commit(ctx); err != nil {
		return nil, err
	}

	after, err := s.GetProduct(ctx, id)
	if err != nil {
		return nil, err
	}
	changed := diffFields(before, after)
	if len(changed) > 0 {
		if err := s.recordProvenance(ctx, id, changed); err != nil {
			return nil, err
		}
	}
	if err := s.writeAudit(ctx, actor, "update", "product", &id, changed, before, after); err != nil {
		return nil, err
	}
	return after, nil
}

func strEq(a, b *string) bool {
	if a == nil && b == nil {
		return true
	}
	if a == nil || b == nil {
		return false
	}
	return *a == *b
}

func floatEq(a, b *float64) bool {
	if a == nil && b == nil {
		return true
	}
	if a == nil || b == nil {
		return false
	}
	return *a == *b
}

func diffFields(a, b *ProductDetail) []string {
	changed := []string{}
	add := func(name string, eq bool) {
		if !eq {
			changed = append(changed, name)
		}
	}
	add("gtin", strEq(a.GTIN, b.GTIN))
	add("name", a.Name == b.Name)
	add("brand", strEq(a.BrandID, b.BrandID))
	add("category", strEq(a.CategoryID, b.CategoryID))
	add("net_content", floatEq(a.NetContentValue, b.NetContentValue) && strEq(a.NetContentUnit, b.NetContentUnit))
	add("country_of_origin", strEq(a.CountryOfOrigin, b.CountryOfOrigin))
	add("status", a.Status == b.Status)
	add("ingredients", strEq(a.IngredientsText, b.IngredientsText))
	ja, _ := json.Marshal(a.Nutriments)
	jb, _ := json.Marshal(b.Nutriments)
	add("nutriments", string(ja) == string(jb))
	add("nutrition_basis", strEq(a.NutritionBasis, b.NutritionBasis))
	add("serving_size", strEq(a.ServingSize, b.ServingSize))
	add("nutri_score", strEq(a.NutriScore, b.NutriScore))
	return changed
}

func (s *Store) recordProvenance(ctx context.Context, productID string, fields []string) error {
	var srcID string
	if err := s.pool.QueryRow(ctx, "SELECT id FROM source WHERE name = 'manual'").Scan(&srcID); err != nil {
		return err
	}
	_, err := s.pool.Exec(ctx, `
INSERT INTO product_source (product_id, source_id, url, fields, fetched_at, raw)
VALUES ($1, $2, NULL, $3, now(), NULL)`, productID, srcID, fields)
	return err
}

func (s *Store) writeAudit(ctx context.Context, actor, action, entity string, entityID *string, fields []string, before, after any) error {
	bj, _ := json.Marshal(before)
	aj, _ := json.Marshal(after)
	if fields == nil {
		fields = []string{}
	}
	_, err := s.pool.Exec(ctx, `
INSERT INTO audit_log (actor, action, entity, entity_id, fields, before, after)
VALUES ($1,$2,$3,$4,$5,$6,$7)`, actor, action, entity, entityID, fields, bj, aj)
	return err
}

// ---------- images ----------

// AddImage inserts an image URL (manual source) and recomputes quality.
func (s *Store) AddImage(ctx context.Context, productID, actor, url, kind string) (*ProductImage, error) {
	if kind == "" {
		kind = "other"
	}
	var srcID string
	if err := s.pool.QueryRow(ctx, "SELECT id FROM source WHERE name = 'manual'").Scan(&srcID); err != nil {
		return nil, err
	}
	var im ProductImage
	err := s.pool.QueryRow(ctx, `
INSERT INTO product_image (product_id, url, kind, license, source_id)
VALUES ($1,$2,$3,NULL,$4) RETURNING id, url, kind, license`,
		productID, url, kind, srcID).Scan(&im.ID, &im.URL, &im.Kind, &im.License)
	if err != nil {
		return nil, err
	}
	if _, err := s.recomputeQuality(ctx, productID); err != nil {
		return nil, err
	}
	_ = s.writeAudit(ctx, actor, "add_image", "product", &productID, []string{"image"}, nil, im)
	return &im, nil
}

// DeleteImage removes an image and recomputes quality.
func (s *Store) DeleteImage(ctx context.Context, productID, imageID, actor string) error {
	ct, err := s.pool.Exec(ctx, "DELETE FROM product_image WHERE id=$1 AND product_id=$2", imageID, productID)
	if err != nil {
		return err
	}
	if ct.RowsAffected() == 0 {
		return ErrNotFound
	}
	if _, err := s.recomputeQuality(ctx, productID); err != nil {
		return err
	}
	_ = s.writeAudit(ctx, actor, "delete_image", "product", &productID, []string{"image"}, map[string]string{"image_id": imageID}, nil)
	return nil
}

// ---------- msrp ----------

// MSRPInput is the payload for adding an MSRP snapshot.
type MSRPInput 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"`
}

// AddMSRP inserts a suggested-retail-price snapshot.
func (s *Store) AddMSRP(ctx context.Context, productID, actor string, in MSRPInput) (*MSRP, error) {
	if in.Currency == "" {
		in.Currency = "CNY"
	}
	if in.Region == "" {
		in.Region = "CN"
	}
	var srcID string
	_ = s.pool.QueryRow(ctx, "SELECT id FROM source WHERE name = 'manual'").Scan(&srcID)
	var m MSRP
	err := s.pool.QueryRow(ctx, `
INSERT INTO product_msrp (product_id, amount, currency, region, source_id, source_url, effective_date, note)
VALUES ($1,$2,$3,$4,$5,$6,$7,$8)
RETURNING id, amount, currency, region, effective_date::text, source_url, note`,
		productID, in.Amount, in.Currency, in.Region, srcID, in.SourceURL, in.EffectiveDate, in.Note).
		Scan(&m.ID, &m.Amount, &m.Currency, &m.Region, &m.EffectiveDate, &m.SourceURL, &m.Note)
	if err != nil {
		return nil, err
	}
	_ = s.writeAudit(ctx, actor, "add_msrp", "product", &productID, []string{"msrp"}, nil, m)
	return &m, nil
}

// DeleteMSRP removes an MSRP snapshot.
func (s *Store) DeleteMSRP(ctx context.Context, productID, msrpID, actor string) error {
	ct, err := s.pool.Exec(ctx, "DELETE FROM product_msrp WHERE id=$1 AND product_id=$2", msrpID, productID)
	if err != nil {
		return err
	}
	if ct.RowsAffected() == 0 {
		return ErrNotFound
	}
	_ = s.writeAudit(ctx, actor, "delete_msrp", "product", &productID, []string{"msrp"}, map[string]string{"msrp_id": msrpID}, nil)
	return nil
}

// ---------- dictionaries ----------

// Brand is a brand option for the edit form.
type Brand struct {
	ID   string `json:"id"`
	Name string `json:"name"`
}

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

// Category is a category option for the edit form.
type Category struct {
	ID     string  `json:"id"`
	NameZH string  `json:"name_zh"`
	NameEN *string `json:"name_en"`
	Path   string  `json:"path"`
	Level  int     `json:"level"`
}

// ListCategories returns the full category tree.
func (s *Store) ListCategories(ctx context.Context) ([]Category, error) {
	rows, err := s.pool.Query(ctx,
		"SELECT id, name_zh, name_en, path::text, 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.Level); err != nil {
			return nil, err
		}
		out = append(out, c)
	}
	return out, rows.Err()
}

// ---------- audit ----------

// AuditEntry is one audit-log row for the history view.
type AuditEntry struct {
	ID        string   `json:"id"`
	Actor     string   `json:"actor"`
	Action    string   `json:"action"`
	Fields    []string `json:"fields"`
	CreatedAt string   `json:"created_at"`
}

// ListAudit returns audit history for one product, newest first.
func (s *Store) ListAudit(ctx context.Context, productID string, limit int) ([]AuditEntry, error) {
	rows, err := s.pool.Query(ctx, `
SELECT id, actor, action, fields, created_at::text
FROM audit_log WHERE entity='product' AND entity_id=$1
ORDER BY created_at DESC LIMIT $2`, productID, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []AuditEntry{}
	for rows.Next() {
		var e AuditEntry
		if err := rows.Scan(&e.ID, &e.Actor, &e.Action, &e.Fields, &e.CreatedAt); err != nil {
			return nil, err
		}
		out = append(out, e)
	}
	return out, rows.Err()
}