package epic

import (
	"context"
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"os"
	"strings"
	"testing"
	"time"

	"gogs.netdome.biz/paul/cheapo/internal/game"
)

// serveFixture spins up an httptest server returning the given JSON file and
// an Epic client pointed at it.
func serveFixture(t *testing.T, path string) *Client {
	t.Helper()
	raw, err := os.ReadFile(path)
	if err != nil {
		t.Fatalf("read fixture: %v", err)
	}
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.Write(raw)
	}))
	t.Cleanup(srv.Close)

	c := NewClient()
	c.BaseURL = srv.URL
	return c
}

func findGame(t *testing.T, games []game.Game, titlePrefix string) *game.Game {
	t.Helper()
	for i := range games {
		if len(games[i].Title) >= len(titlePrefix) && games[i].Title[:len(titlePrefix)] == titlePrefix {
			return &games[i]
		}
	}
	t.Fatalf("game %q not found in %d games", titlePrefix, len(games))
	return nil
}

// QUIRK — Epic's free indicator lives in the ELEMENT price, not the offer.
// The API duplicates discount info in two places, and they disagree:
//
//   - offer.promotions.promotionalOffers[].discountSetting.discountPrice
//     is NULL (→ 0 in Go) even for offers that are NOT free. Naively
//     treating 0 as "free" marked Castlevania (real price 7,99 €) as free —
//     exactly what the store does NOT show.
//   - The element's price.totalPrice.discountPrice is the actual current
//     price in cents and is the field the storefront itself renders.
//
// This test pins: free ⟺ element price == 0, judged against the live
// fixture (Oct 2026: only "Sorry We're Closed" is free; Castlevania must
// not appear despite discountSetting.discountPrice being null).
func TestLiveFixture_FreeIsDeterminedByElementPriceNotOfferDiscount(t *testing.T) {
	c := serveFixture(t, "testdata/promotions_live.json")
	games, err := c.GetFreeGames(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if len(games) != 1 {
		t.Fatalf("want exactly 1 free game (Sorry We're Closed), got %d: %+v", len(games), titles(games))
	}
	if got, want := normTitle(games[0].Title), "Sorry We're Closed"; got != want {
		t.Fatalf("free game = %q, want %q", got, want)
	}
	// Castlevania: element price 7,99 € → must NOT be in the free list.
	for _, g := range games {
		if strings.HasPrefix(normTitle(g.Title), "Castlevania") {
			t.Errorf("Castlevania must not be free (current price 7,99 €)")
		}
	}
}

// QUIRK — discountPercentage is meaningless for free offers. A genuinely
// free element (price 0) can carry a promotionalOffers percentage of e.g.
// 20 — nonsense as a "discount", just leftover campaign metadata. The old
// filter (percentage != 100 → not free) would have dropped real free games.
// Pinned: an element with price 0 and percentage 20 is reported FREE, and
// without a DiscountPct (percent labels are only for real deals).
func TestFreeOfferWithMisleadingPercentageIsStillFree(t *testing.T) {
	fixture := map[string]any{
		"data": map[string]any{
			"Catalog": map[string]any{
				"searchStore": map[string]any{
					"elements": []map[string]any{
						quirkElement("Free Game", "0", 0, 20), // price 0, offer percentage 20
						quirkElement("Paid Game", "19,99 €", 1999, 0),
					},
				},
			},
		},
	}
	c := serveJSON(t, fixture)
	games, err := c.GetFreeGames(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if len(games) != 1 || games[0].Title != "Free Game" {
		t.Fatalf("want only 'Free Game', got %v", titles(games))
	}
	if games[0].DiscountPct != 0 {
		t.Errorf("free game must not carry DiscountPct, got %d", games[0].DiscountPct)
	}
}

// QUIRK — discountPercentage is inconsistent for deals too. Live example
// (Oct 2026): Castlevania carries percentage 40 while the store page shows
// −60 %. The real discount must be computed from the prices:
// (originalPriceCents − discountPriceCents) / originalPriceCents. Pinned
// with the live fixture: Castlevania 19,99 € → 7,99 € = −60 %, Eternal
// Threads 17,99 € → 3,59 € = −80 %.
func TestLiveFixture_DealsComputePercentFromPrices(t *testing.T) {
	c := serveFixture(t, "testdata/promotions_live.json")
	deals, err := c.GetDeals(context.Background())
	if err != nil {
		t.Fatal(err)
	}

	cv := findGame(t, deals, "Castlevania")
	_ = cv
	if normPrice(cv.FinalPriceFmt) != "7,99 €" {
		t.Errorf("Castlevania final price = %q, want 7,99 € (from fmtPrice.discountPrice)", cv.FinalPriceFmt)
	}
	if normPrice(cv.PriceFmt) != "19,99 €" {
		t.Errorf("Castlevania original price = %q, want 19,99 €", cv.PriceFmt)
	}
	// 1999 cents → 799 cents = −60 % (store value), NOT the API's misleading 40.
	if cv.DiscountPct != 60 {
		t.Errorf("Castlevania discount = %d %%, want 60 (computed 1999→799)", cv.DiscountPct)
	}

	et := findGame(t, deals, "Eternal Threads")
	if normPrice(et.FinalPriceFmt) != "3,59 €" || et.DiscountPct != 80 {
		t.Errorf("Eternal Threads = %q −%d %%, want 3,59 € −80 %%", et.FinalPriceFmt, et.DiscountPct)
	}
}

// QUIRK — because discountSetting is unreliable (see above), a buggy filter
// can classify the same element as free AND as deal, or drop it from both.
// The lists are disjoint by construction (element price 0 = free, else
// deal); this test guards that invariant against future filter changes.
// The live fixture guarantees there ARE deals to check (Oct 2026: Eternal
// Threads, Castlevania, Monument Valley as discounts).
func TestLiveFixture_FreeAndDealsAreDisjoint(t *testing.T) {
	c := serveFixture(t, "testdata/promotions_live.json")
	free, err := c.GetFreeGames(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	deals, err := c.GetDeals(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	freeIDs := map[string]bool{}
	for _, g := range free {
		freeIDs[g.ID] = true
	}
	for _, g := range deals {
		if freeIDs[g.ID] {
			t.Errorf("game %q appears both free and as deal", g.Title)
		}
	}
	if len(deals) == 0 {
		t.Error("live fixture should contain deals (Eternal Threads, Castlevania, …)")
	}
}

// QUIRK — some elements come with an active promotion window but WITHOUT a
// price object at all. In Go, decoding that yields discountPrice == 0, which
// naively reads as "free". But an element without price info is simply not
// classifiable — the storefront never renders it as free either. Pinned:
// missing price data must be skipped, never reported as free.
func TestOfferWithoutPriceFieldsIsSkipped(t *testing.T) {
	fixture := map[string]any{
		"data": map[string]any{
			"Catalog": map[string]any{
				"searchStore": map[string]any{
					"elements": []map[string]any{
						// No top-level "price" at all → discountPrice 0 would
						// naively look free; the store's real semantics here
						// (live element without price) are not free.
						quirkElement("Mystery Game", "", -1, 0),
					},
				},
			},
		},
	}
	c := serveJSON(t, fixture)
	games, err := c.GetFreeGames(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if len(games) != 0 {
		t.Fatalf("element without price must be skipped, got %v", titles(games))
	}
}

// QUIRK — Epic announces future giveaways in a SEPARATE array
// (upcomingPromotionalOffers), not in promotionalOffers. The two arrays use
// the same offer shape but only upcoming ones may have a future startDate.
// Also pinned: sorting by start date (soonest first) and kind = "upcoming"
// — even when the element is currently free in another window (an element
// can be free now AND have an upcoming window; both listings are valid).
func TestUpcomingGamesFromUpcomingWindows(t *testing.T) {
	c := serveFixture(t, "testdata/promotions_live.json")
	games, err := c.GetUpcomingGames(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if len(games) == 0 {
		t.Fatal("live fixture has upcoming offers (Flotsam, Idle Champions, …)")
	}
	for i := 1; i < len(games); i++ {
		if games[i].StartDate.Before(games[i-1].StartDate) {
			t.Fatalf("upcoming games not sorted by start date: %+v", titles(games))
		}
	}
	fl := findGame(t, games, "Flotsam")
	if fl.Kind != "upcoming" {
		t.Errorf("Flotsam kind = %q, want upcoming", fl.Kind)
	}
	if fl.StartDate.Before(time.Now()) {
		t.Errorf("upcoming game start date in the past: %v", fl.StartDate)
	}
}

// QUIRK — the same element can appear with MULTIPLE promotion windows (an
// extended giveaway appends a second window with a later endDate). Without
// dedup the game shows up twice in the list. Pinned: one entry per element
// ID, carrying the LATEST end date.
func TestDedupWindowsKeepsLatestEndDate(t *testing.T) {
	c := serveFixture(t, "testdata/promotions_live.json")
	games, err := c.GetFreeGames(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	seen := map[string]int{}
	for _, g := range games {
		seen[g.ID]++
	}
	for id, n := range seen {
		if n > 1 {
			t.Errorf("game %s appears %d times, want 1 (dedup by ID)", id, n)
		}
	}
}

// --- helpers ---

// QUIRK — Epic titles contain NBSP (\u00a0) instead of regular spaces
// (e.g. "Sorry We're Closed" with a non-breaking space after "Sorry").
// Comparisons against plain-space literals silently fail; all title/price
// comparisons in tests normalize NBSP first. This test file pins that the
// fixtures really contain NBSP — if Epic ever switches to plain spaces,
// normTitle stays harmless.
func normTitle(s string) string {
	return strings.ReplaceAll(s, "\u00a0", " ")
}

// normPrice normalizes price strings for comparisons (NBSP → space).
func normPrice(s string) string { return normTitle(s) }

func titles(games []game.Game) []string {
	var s []string
	for _, g := range games {
		s = append(s, g.Title)
	}
	return s
}

// serveJSON serves an arbitrary object as JSON.
func serveJSON(t *testing.T, v any) *Client {
	t.Helper()
	raw, err := json.Marshal(v)
	if err != nil {
		t.Fatal(err)
	}
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.Write(raw)
	}))
	t.Cleanup(srv.Close)
	c := NewClient()
	c.BaseURL = srv.URL
	return c
}

// quirkElement builds one element with controlled price/discount fields to
// pin the API quirks. fmtPrice "": omit the price object entirely (original
// cents < 0); discountPrice cents < 0: omit discountSetting.discountPrice.
func quirkElement(title, fmtOriginal string, originalCents, offerPercentage int) map[string]any {
	el := map[string]any{
		"id":    "quirk-" + title,
		"title": title,
		"catalogNs": map[string]any{
			"mappings": []map[string]any{{"pageSlug": title}},
		},
		"seller": map[string]any{"displayName": "Quirk Seller"},
		"promotions": map[string]any{
			"promotionalOffers": []map[string]any{
				{
					"promotionalOffers": []map[string]any{
						{
							"startDate": "2026-10-01T00:00:00.000Z",
							"endDate":   "2027-01-01T00:00:00.000Z",
							"discountSetting": map[string]any{
								// Omit discountPrice entirely (null case).
								"discountPercentage": offerPercentage,
							},
						},
					},
				},
			},
		},
	}
	if originalCents >= 0 {
		el["price"] = map[string]any{
			"totalPrice": map[string]any{
				"discountPrice": originalCents, // current price == list price here (not discounted)
				"originalPrice": originalCents,
				"fmtPrice": map[string]any{
					"originalPrice": fmtOriginal,
					"discountPrice": fmtOriginal,
				},
			},
		}
	}
	return el
}