package services

import (
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"

	"nearle/models"
)

/*
The nutrition panel on the product screen.

The fixture is the catalogue-intelligence service's own record for Cadbury
5 Star, read from mcp.nearle.ai.in on 29 Sep 2026 — including the awkward parts:
a null `added_sugar_g`, a `dietary_fiber_g` of exactly 0, and an
`extended_nutrients` map carrying its own unit.
*/
const fiveStarJSON = `{
  "data_status": "verified",
  "serving_size_label": "1 mini (11 g)",
  "serving_size_g": 11,
  "calories_kcal": 525.0, "protein_g": 6.8, "carbohydrates_g": 62.6,
  "total_sugar_g": 58.8, "added_sugar_g": null, "dietary_fiber_g": 0.0,
  "total_fat_g": 27.9, "saturated_fat_g": 18.7, "trans_fat_g": null,
  "cholesterol_mg": null, "sodium_mg": 107,
  "extended_nutrients": {"Salt": {"unit": "g", "value": 0.268}}
}`

// The answer for a product the service knows nothing about — which is most of
// them, including the Patanjali ghee this work started from.
const unavailableJSON = `{
  "data_status": "unavailable", "serving_size_label": null,
  "calories_kcal": null, "protein_g": null, "sodium_mg": null,
  "extended_nutrients": null
}`

func panelOf(t *testing.T, raw string) *models.NutritionPanel {
	t.Helper()
	var source NutritionSource
	if err := json.Unmarshal([]byte(raw), &source); err != nil {
		t.Fatalf("fixture: %v", err)
	}
	return source.Panel()
}

func TestARealRecordBecomesTheAppsPanel(t *testing.T) {
	panel := panelOf(t, fiveStarJSON)
	if !panel.HasValues() {
		t.Fatal("no panel from a verified record")
	}
	if panel.Per != "100g" {
		// The service's top-level figures are per 100g — its own insights say
		// "6.8 g per 100 g" and the console prints the same basis.
		t.Errorf("per = %q, want 100g", panel.Per)
	}
	if panel.Servingsize != "1 mini (11 g)" {
		t.Errorf("servingsize = %q", panel.Servingsize)
	}

	want := map[string][2]any{
		"Energy":        {525.0, "kcal"},
		"Protein":       {6.8, "g"},
		"Carbohydrate":  {62.6, "g"},
		"Total Sugars":  {58.8, "g"},
		"Dietary Fibre": {0.0, "g"},
		"Total Fat":     {27.9, "g"},
		"Saturated Fat": {18.7, "g"},
		"Sodium":        {107.0, "mg"},
		"Salt":          {0.268, "g"},
	}
	got := map[string][2]any{}
	for _, item := range panel.Items {
		got[item.Name] = [2]any{item.Value, item.Unit}
	}
	for name, expected := range want {
		if got[name] != expected {
			t.Errorf("%s = %v, want %v", name, got[name], expected)
		}
	}
	if len(panel.Items) != len(want) {
		t.Errorf("got %d rows, want %d: %+v", len(panel.Items), len(want), panel.Items)
	}
}

func TestAFieldTheServiceDidNotStateIsNotARow(t *testing.T) {
	// `added_sugar_g` is null on this record. A table of dashes is worse than a
	// shorter table, and a 0 would claim the product has no added sugar.
	for _, item := range panelOf(t, fiveStarJSON).Items {
		if item.Name == "Added Sugars" || item.Name == "Trans Fat" || item.Name == "Cholesterol" {
			t.Errorf("invented a row the service left null: %+v", item)
		}
	}
}

func TestAGenuineZeroIsKept(t *testing.T) {
	// `dietary_fiber_g` is 0.0, not null. "No fibre" is a fact the label states
	// and dropping it would lose it — the opposite of the null case above.
	var found bool
	for _, item := range panelOf(t, fiveStarJSON).Items {
		if item.Name == "Dietary Fibre" {
			found = true
			if item.Value != 0 {
				t.Errorf("got %v, want 0", item.Value)
			}
		}
	}
	if !found {
		t.Error("a stated zero was dropped")
	}
}

func TestAnUnavailableProductGetsNoPanel(t *testing.T) {
	// The common case today: the service knows the product and has nothing. An
	// empty panel on the screen reads as "this food has no nutrition".
	if panel := panelOf(t, unavailableJSON); panel != nil {
		t.Fatalf("made a panel out of nulls: %+v", panel)
	}
}

func TestTheRowOrderIsStable(t *testing.T) {
	// `extended_nutrients` is a map, and Go map order is randomised. A panel
	// that reshuffles between two requests for the same product looks broken.
	first := panelOf(t, fiveStarJSON)
	for i := 0; i < 20; i++ {
		next := panelOf(t, fiveStarJSON)
		for j := range first.Items {
			if next.Items[j].Name != first.Items[j].Name {
				t.Fatalf("row %d moved: %s then %s", j, first.Items[j].Name, next.Items[j].Name)
			}
		}
	}
}

/* ── The client ──────────────────────────────────────────────────────────── */

func TestTheBrandSpellingIsResolvedBeforeTheLookup(t *testing.T) {
	// Ours is `patanjali`, theirs is `Patanjali`. A wrong spelling returns a
	// well-formed record with every figure null — indistinguishable from an
	// unscored product — so this failing is silent and total.
	var asked string
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/brands" {
			_, _ = w.Write([]byte(`{"brands":["Patanjali","Coca-Cola","Brooke Bond"]}`))
			return
		}
		asked = r.URL.Path
		_, _ = w.Write([]byte(fiveStarJSON))
	}))
	defer server.Close()

	service := NewNutritionService(server.URL)
	if found := service.ForProduct("patanjali", "patanjali_cow_ghee_500ml"); !found.Panel.HasValues() {
		t.Fatal("no panel")
	}
	if asked != "/nutrition/Patanjali/patanjali_cow_ghee_500ml" {
		t.Fatalf("asked for %q", asked)
	}
}

func TestAnUnderscoreIsNotGuessedAt(t *testing.T) {
	// It becomes a hyphen for Coca-Cola and a space for Brooke Bond. Which one
	// cannot be derived, so the list is matched rather than transformed.
	var asked string
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/brands" {
			_, _ = w.Write([]byte(`{"brands":["Coca-Cola","Brooke Bond"]}`))
			return
		}
		asked = r.URL.Path
		_, _ = w.Write([]byte(fiveStarJSON))
	}))
	defer server.Close()

	NewNutritionService(server.URL).ForProduct("brooke_bond", "bb_tea_250g")
	if asked != "/nutrition/Brooke Bond/bb_tea_250g" {
		t.Fatalf("asked for %q", asked)
	}
}

func TestAnUnknownBrandStillGetsATry(t *testing.T) {
	// A brand they have not listed yet is attempted with our spelling rather
	// than dropped — the list is their vocabulary, not a gate.
	var asked string
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/brands" {
			_, _ = w.Write([]byte(`{"brands":["Amul"]}`))
			return
		}
		asked = r.URL.Path
		w.WriteHeader(http.StatusNotFound)
	}))
	defer server.Close()

	NewNutritionService(server.URL).ForProduct("newbrand", "nb_thing_1kg")
	if asked != "/nutrition/newbrand/nb_thing_1kg" {
		t.Fatalf("asked for %q", asked)
	}
}

func TestAProductScreenSurvivesTheServiceBeingDown(t *testing.T) {
	// The whole reason this returns a panel and never an error. A shopper
	// tapped a product; they are owed the screen with or without nutrition.
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusInternalServerError)
	}))
	server.Close() // refused connections, not merely 500s

	if found := NewNutritionService(server.URL).ForProduct("cadbury", "x"); found.Panel != nil {
		t.Fatalf("got a panel from a dead service: %+v", found.Panel)
	}
}

func TestAMalformedResponseIsNotAPanel(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/brands" {
			_, _ = w.Write([]byte(`{"brands":[]}`))
			return
		}
		_, _ = w.Write([]byte(`{"calories_kcal":`))
	}))
	defer server.Close()

	if found := NewNutritionService(server.URL).ForProduct("cadbury", "x"); found.Panel != nil {
		t.Fatalf("read a panel out of broken JSON: %+v", found.Panel)
	}
}

func TestTheSameProductIsNotFetchedTwice(t *testing.T) {
	// This runs on a screen a shopper is waiting on, once per member of a
	// variant group. Nutrition for a packaged product does not change during a
	// trading day.
	var hits int
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/brands" {
			_, _ = w.Write([]byte(`{"brands":["Cadbury"]}`))
			return
		}
		hits++
		_, _ = w.Write([]byte(fiveStarJSON))
	}))
	defer server.Close()

	service := NewNutritionService(server.URL)
	for i := 0; i < 5; i++ {
		service.ForProduct("cadbury", "cadbury_5_star_200g")
	}
	if hits != 1 {
		t.Fatalf("fetched %d times, want 1", hits)
	}
}

func TestAMissIsCachedToo(t *testing.T) {
	// Most products are unscored. Re-asking on every tap would mean the least
	// useful answer costing the most requests.
	var hits int
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/brands" {
			_, _ = w.Write([]byte(`{"brands":["Patanjali"]}`))
			return
		}
		hits++
		_, _ = w.Write([]byte(unavailableJSON))
	}))
	defer server.Close()

	service := NewNutritionService(server.URL)
	for i := 0; i < 4; i++ {
		service.ForProduct("patanjali", "patanjali_cow_ghee_500ml")
	}
	if hits != 1 {
		t.Fatalf("fetched %d times, want 1", hits)
	}
}

func TestAProductWithNoJoinKeyIsNotLookedUp(t *testing.T) {
	// Sheet-imported products have no image_id. There is nothing to look up,
	// which is different from something that failed to be found.
	server := httptest.NewServer(http.HandlerFunc(func(_ http.ResponseWriter, _ *http.Request) {
		t.Error("called the service for a product with no image_id")
	}))
	defer server.Close()

	service := NewNutritionService(server.URL)
	service.ForProduct("cadbury", "")
	service.ForProduct("", "some_image_id")
}

func TestNoServiceConfiguredIsNotACrash(t *testing.T) {
	// Nil is a working configuration: a deployment without the service serves
	// every product screen, without a panel.
	if NewNutritionService("") != nil {
		t.Fatal("built a client with no base URL")
	}
	rows := []models.Products{{Productid: 1, Productbrand: "cadbury", Imageid: "x"}}
	decorateNutrition(nil, rows) // must not panic
	if rows[0].Nutrition != nil {
		t.Fatal("invented a panel with no service")
	}
}

func TestEverySiblingInAVariantGroupIsDecorated(t *testing.T) {
	// A shopper switching from 500ml to 1L must not watch the panel vanish.
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/brands" {
			_, _ = w.Write([]byte(`{"brands":["Cadbury"]}`))
			return
		}
		_, _ = w.Write([]byte(fiveStarJSON))
	}))
	defer server.Close()

	rows := []models.Products{
		{Productid: 1, Productbrand: "cadbury", Imageid: "a"},
		{Productid: 2, Productbrand: "cadbury", Imageid: "b"},
		{Productid: 3, Productbrand: "cadbury", Imageid: ""},
	}
	decorateNutrition(NewNutritionService(server.URL), rows)

	if !rows[0].Nutrition.HasValues() || !rows[1].Nutrition.HasValues() {
		t.Fatal("a sibling lost its panel")
	}
	if rows[2].Nutrition != nil {
		t.Fatal("invented a panel for a product with no join key")
	}
}

func TestTheWireNamesAreTheOnesTheAppAskedFor(t *testing.T) {
	// An API is a promise to a client already written against it. `servingsize`
	// is not how the rest of this codebase would spell it, and it is what was
	// asked for, which outranks house style.
	rows := []models.Products{{Productid: 7093}}
	rows[0].Nutrition = panelOf(t, fiveStarJSON)

	encoded, err := json.Marshal(rows[0])
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	var out map[string]any
	if err := json.Unmarshal(encoded, &out); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}

	nutrition, ok := out["nutrition"].(map[string]any)
	if !ok {
		t.Fatalf("no `nutrition` key: %s", encoded)
	}
	for _, key := range []string{"per", "servingsize", "items"} {
		if _, ok := nutrition[key]; !ok {
			t.Errorf("missing %q", key)
		}
	}
	item := nutrition["items"].([]any)[0].(map[string]any)
	for _, key := range []string{"name", "value", "unit"} {
		if _, ok := item[key]; !ok {
			t.Errorf("item missing %q", key)
		}
	}
}

func TestAProductWithNoNutritionHasNoKeyAtAll(t *testing.T) {
	// Not `"nutrition": null`. Most products have none, and a null on every row
	// is payload spent saying nothing.
	encoded, _ := json.Marshal(models.Products{Productid: 1})
	var out map[string]any
	_ = json.Unmarshal(encoded, &out)
	if _, present := out["nutrition"]; present {
		t.Fatalf("an absent panel was sent as a key: %s", encoded)
	}
}

/* ── Not caching an answer we do not trust ───────────────────────────────── */

func TestAnUnresolvedBrandIsNotCachedAsAMiss(t *testing.T) {
	// The failure this prevents, measured 30 Sep 2026:
	// `/nutrition/Balaji/balaji_..._135g` returns a 65.3 score and 545 kcal;
	// `/nutrition/balaji/...` — our own spelling — returns a well-formed record
	// with every field null. So a lookup made before the brand list arrived
	// does not mean "no nutrition", it means we asked the wrong question.
	//
	// Cached, one slow moment on /brands would silently remove nutrition from
	// every product of every brand for six hours.
	var brandsUp bool
	var productHits int
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/brands" {
			if !brandsUp {
				w.WriteHeader(http.StatusGatewayTimeout)
				return
			}
			_, _ = w.Write([]byte(`{"brands":["Balaji"]}`))
			return
		}
		productHits++
		if strings.Contains(r.URL.Path, "/Balaji/") {
			_, _ = w.Write([]byte(balajiJSON))
			return
		}
		// What the service actually answers for the wrong spelling.
		_, _ = w.Write([]byte(unavailableJSON))
	}))
	defer server.Close()

	service := NewNutritionService(server.URL)

	// Brand list down: the answer is a miss, and must not stick.
	if found := service.ForProduct("balaji", "balaji_wafers_135g"); found.Panel != nil {
		t.Fatal("got a panel from the wrong spelling")
	}

	// Brand list back: the same product must be asked again, correctly.
	brandsUp = true
	found := service.ForProduct("balaji", "balaji_wafers_135g")
	if !found.Panel.HasValues() {
		t.Fatal("the miss was cached — a slow /brands has cost six hours of nutrition")
	}
	if found.Health == nil || found.Health.Score != 65 {
		t.Fatalf("score lost: %+v", found.Health)
	}
	if productHits < 2 {
		t.Fatalf("the product was only asked for %d time(s)", productHits)
	}
}

func TestAResolvedMissIsStillCached(t *testing.T) {
	// The other half: when the brand IS theirs and they simply have nothing,
	// that is a real answer and re-asking on every tap wastes the most
	// requests on the least useful result.
	var productHits int
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/brands" {
			_, _ = w.Write([]byte(`{"brands":["Patanjali"]}`))
			return
		}
		productHits++
		_, _ = w.Write([]byte(unavailableJSON))
	}))
	defer server.Close()

	service := NewNutritionService(server.URL)
	for i := 0; i < 4; i++ {
		service.ForProduct("patanjali", "patanjali_cow_ghee_500ml")
	}
	if productHits != 1 {
		t.Fatalf("asked %d times for a product the service has answered about", productHits)
	}
}