ModelRouter/internal/lua/billing_test.go

package lua

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"testing"
)

// pluginLoaded reports whether a plugin with this name is present, ignoring any
// LoadError: a plugin that is present but broken still counts as "loaded here",
// and the caller decides whether the error matters.
func pluginLoaded(ps *Plugins, name string) bool {
	for _, p := range ps.List() {
		if fmt.Sprint(p["name"]) == name {
			return true
		}
	}
	return false
}

// The billing plugin ships with the gateway, so its arithmetic is a contract:
// a wrong price silently produces wrong money. These tests drive it through the
// real hook path and check the NUMBERS, not merely that it loads.

func billingVM(t *testing.T) (*Plugins, string) {
	t.Helper()
	dir := filepath.Join(t.TempDir(), "adapters")
	vm := NewVM(dir)
	if err := vm.Start(); err != nil {
		t.Fatalf("vm: %v", err)
	}
	t.Cleanup(vm.Stop)
	pdir := filepath.Join(t.TempDir(), "plugins")
	ps := NewPlugins(vm, pdir)
	if err := ps.SeedBundled(); err != nil {
		t.Fatalf("seed: %v", err)
	}
	if err := ps.LoadDir(); err != nil {
		t.Fatalf("load: %v", err)
	}
	return ps, pdir
}

// stateOf reads the plugin's published state as a generic map.
func stateOf(t *testing.T, ps *Plugins) map[string]interface{} {
	t.Helper()
	raw := ps.State("billing")
	if raw == nil {
		t.Fatal("billing published no state")
	}
	b, err := json.Marshal(raw)
	if err != nil {
		t.Fatal(err)
	}
	var out map[string]interface{}
	if err := json.Unmarshal(b, &out); err != nil {
		t.Fatal(err)
	}
	return out
}

func approx(t *testing.T, name string, got, want float64) {
	t.Helper()
	d := got - want
	if d < 0 {
		d = -d
	}
	if d > 1e-9 {
		t.Errorf("%s = %v, want %v (delta %v)", name, got, want, d)
	}
}

// TestBillingZeroPricesIsSafe: with no configuration the plugin must still run
// and report volume. A nil-price crash here would take out every request.
func TestBillingZeroPricesIsSafe(t *testing.T) {
	ps, _ := billingVM(t)
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "key": "***aaaaaa", "ok": true,
		"prompt_tokens": 100, "completion_tokens": 50, "time": 1750000000000,
	})
	st := stateOf(t, ps)
	total := st["total"].(map[string]interface{})
	if total["requests"].(float64) != 1 {
		t.Errorf("requests = %v, want 1", total["requests"])
	}
	approx(t, "cost with no prices", total["cost"].(float64), 0)
}

// TestBillingModelTokenPricing: the core case. prompt and completion are priced
// SEPARATELY, which is how providers publish and how the total must come out.
func TestBillingModelTokenPricing(t *testing.T) {
	ps, _ := billingVM(t)
	// Setting prices must NOT disturb the (still empty) totals, which is the
	// whole point of the prices/state split.
	if err := ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"currency": "USD",
			"models": map[string]interface{}{
				"gpt-5.4": map[string]interface{}{"prompt": 1.25e-6, "completion": 1e-5},
			},
		},
	}); err != nil {
		t.Fatal(err)
	}
	// 1000 prompt * 1.25e-6 = 0.00125 ; 500 completion * 1e-5 = 0.005
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "gpt-5.4", "source": "up", "key": "***aaaaaa", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 500, "time": 1750000000000,
	})
	st := stateOf(t, ps)
	approx(t, "total cost", st["total"].(map[string]interface{})["cost"].(float64), 0.00625)
	byModel := st["by_model"].(map[string]interface{})["gpt-5.4"].(map[string]interface{})
	approx(t, "model cost", byModel["cost"].(float64), 0.00625)
	if byModel["completion_tokens"].(float64) != 500 {
		t.Errorf("completion_tokens = %v, want 500", byModel["completion_tokens"])
	}
}

// TestBillingPerRequestAndTokenCombine: a flat fee is ADDED to the token cost,
// which is how an image model can be "tokens + fixed fee".
func TestBillingPerRequestAndTokenCombine(t *testing.T) {
	ps, _ := billingVM(t)
	if err := ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"kolors": map[string]interface{}{"prompt": 1e-6, "completion": 2e-6, "per_request": 0.04},
			},
		},
	}); err != nil {
		t.Fatal(err)
	}
	// 100*1e-6 + 50*2e-6 + 0.04 = 0.0402
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "kolors", "source": "sf", "key": "***bbbbbb", "ok": true,
		"prompt_tokens": 100, "completion_tokens": 50, "time": 1750000000000,
	})
	st := stateOf(t, ps)
	approx(t, "total", st["total"].(map[string]interface{})["cost"].(float64), 0.0402)
}

// TestBillingPrecedence: keys > models > default for token prices.
func TestBillingPrecedence(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"default": map[string]interface{}{"prompt": 9e-6, "completion": 9e-6},
			"models":  map[string]interface{}{"m": map[string]interface{}{"prompt": 2e-6, "completion": 3e-6}},
			"keys":    map[string]interface{}{"***cccccc": map[string]interface{}{"prompt": 1e-6, "completion": 1.5e-6}},
		},
	})

	// No key match -> model price.
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "key": "***other", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 1000, "time": 1750000000000,
	})
	// Key match -> key price wins.
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "key": "***cccccc", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 1000, "time": 1750000000000,
	})
	st := stateOf(t, ps)
	// 1000*2e-6 + 1000*3e-6 = 0.005 ; 1000*1e-6 + 1000*1.5e-6 = 0.0025
	approx(t, "total (model + key)", st["total"].(map[string]interface{})["cost"].(float64), 0.0075)

	// An unpriced model falls back to default.
	ps2, _ := billingVM(t)
	_ = ps2.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"default": map[string]interface{}{"prompt": 9e-6, "completion": 9e-6},
		},
	})
	ps2.Fire(StageRequestEnd, map[string]interface{}{
		"model": "unknown", "source": "s", "key": "***d", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 1000, "time": 1750000000000,
	})
	approx(t, "default fallback", stateOf(t, ps2)["total"].(map[string]interface{})["cost"].(float64), 0.018)
}

// TestBillingAggregatesEveryDimension: one request must land in all four
// rollups plus the daily bucket. A missing dimension is the kind of bug a
// dashboard hides (it just renders an empty table).
func TestBillingAggregatesEveryDimension(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"models": map[string]interface{}{"m1": map[string]interface{}{"prompt": 1e-6, "completion": 1e-6}},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m1", "source": "srcA", "key": "***key01", "ok": true,
		"prompt_tokens": 100, "completion_tokens": 100, "time": 1750000000000,
	})
	st := stateOf(t, ps)
	for _, dim := range []string{"by_source", "by_model", "by_key", "by_day"} {
		m, ok := st[dim].(map[string]interface{})
		if !ok || len(m) == 0 {
			t.Errorf("%s is empty; a dimension is missing", dim)
		}
	}
	if _, ok := st["by_source"].(map[string]interface{})["srcA"]; !ok {
		t.Error("by_source lacks srcA")
	}
	if _, ok := st["by_key"].(map[string]interface{})["***key01"]; !ok {
		t.Error("by_key lacks the gateway key")
	}
	// Milliseconds must be converted, not used as seconds: a raw 1750000000000
	// would land in a year-57000 bucket.
	days := st["by_day"].(map[string]interface{})
	found := false
	for k := range days {
		if len(k) == 10 && strings.Contains(k, "-") {
			found = true
		}
		if strings.HasPrefix(k, "5") && len(k) > 6 {
			t.Errorf("by_day key %q suggests millisecond timestamps were not converted", k)
		}
	}
	if !found {
		t.Errorf("by_day has no YYYY-MM-DD key: %v", days)
	}
}

// TestBillingFailedRequestPolicy: a failed request keeps its token cost (tokens
// really were consumed) but drops the flat per_request fee (never charged).
func TestBillingFailedRequestPolicy(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"m": map[string]interface{}{"prompt": 1e-6, "completion": 1e-6, "per_request": 0.5},
			},
		},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "key": "***e", "ok": false, "status": 500,
		"prompt_tokens": 1000, "completion_tokens": 0, "time": 1750000000000,
	})
	st := stateOf(t, ps)
	// 1000*1e-6 = 0.001, flat dropped.
	approx(t, "failed request", st["total"].(map[string]interface{})["cost"].(float64), 0.001)
	if st["total"].(map[string]interface{})["failures"].(float64) != 1 {
		t.Error("failures not counted")
	}
}

// TestBillingStateAPIReplace: the admin price update must actually change
// subsequent pricing (not just be stored).
func TestBillingStateAPIReplace(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{"m": map[string]interface{}{"prompt": 1e-6, "completion": 0}},
		},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "key": "***f", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 0, "time": 1750000000000,
	})
	approx(t, "before reprice", stateOf(t, ps)["total"].(map[string]interface{})["cost"].(float64), 0.001)

	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{"m": map[string]interface{}{"prompt": 2e-6, "completion": 0}},
		},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "key": "***f", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 0, "time": 1750000000000,
	})
	// 0.001 (old) + 0.002 (new price)
	approx(t, "after reprice", stateOf(t, ps)["total"].(map[string]interface{})["cost"].(float64), 0.003)
}

// TestBillingPluginDeclaresUI: the shipped plugin must ship its dashboard, or
// "billing is enabled" would be true while showing the user nothing.
func TestBillingPluginDeclaresUI(t *testing.T) {
	ps, _ := billingVM(t)
	for _, row := range ps.List() {
		if row["name"] != "billing" {
			continue
		}
		ui, ok := row["ui"].(map[string]interface{})
		if !ok {
			t.Fatal("billing declares no ui")
		}
		if page, _ := ui["page"].(string); page != "billing" {
			t.Errorf("ui.page = %v, want \"billing\"", ui["page"])
		}
		// ONE page, not two. The rule editor and the totals share a sidebar
		// entry because billing is one thing: prices decide the numbers and the
		// numbers are the result of the prices. Split across two pages, saving a
		// price left no on-screen way to see its effect — the loop the operator
		// actually works in was cut in half.
		pages, _ := ui["pages"].([]string)
		if len(pages) != 1 || pages[0] != "billing" {
			t.Errorf("ui.pages = %v, want exactly one page [billing]", pages)
		}
		if n, _ := ui["elements"].(int); n < 1 {
			t.Error("billing contributes no element to an existing page")
		}
		return
	}
	t.Fatal("billing plugin is not loaded")
}

// TestBillingRuleEditorLivesInsideTheBillingPage: the rule editor is a VIEW
// inside the billing page, not a second sidebar entry.
//
// This started as a separate page and was wrong: saving a price sent the
// operator to a different screen to find out whether it worked. A single page
// with a view switch keeps the loop closed, and the rule editor already refreshes
// the usage numbers on save, so the effect is visible immediately.
//
// The mount must therefore carry BOTH the usage tables and the rule editor, and
// the switch that toggles between them.
func TestBillingRuleEditorLivesInsideTheBillingPage(t *testing.T) {
	ps, _ := billingVM(t)
	var ui *UIExtension
	for _, p := range ps.plugins {
		if p.Info.Name == "billing" {
			ui = p.UI
		}
	}
	if ui == nil || ui.Page == nil {
		t.Fatal("billing plugin loaded with no page")
	}
	if ui.Page.PageID != "billing" {
		t.Errorf("page id = %q, want billing", ui.Page.PageID)
	}
	mount := ui.Page.Mount

	// Both halves on one page.
	for _, needle := range []string{`id="billing-kpis"`, `id="billing-by-source"`} {
		if !strings.Contains(mount, needle) {
			t.Errorf("the usage half is missing %s", needle)
		}
	}
	for _, needle := range []string{
		`id="br-body"`,
		"data-act='save'", "data-act='export'", "data-act='newprofile'",
		".r-url", ".r-mode",
	} {
		if !strings.Contains(mount, needle) {
			t.Errorf("the rule editor is missing %s", needle)
		}
	}
	// The switch itself, or the two halves are both on screen at once.
	for _, needle := range []string{`id="billing-view-usage"`, `id="billing-view-rules"`, `window.__billing_view(`} {
		if !strings.Contains(mount, needle) {
			t.Errorf("the view switch is missing %s", needle)
		}
	}
	// The rules view must start hidden, otherwise it renders under the usage
	// tables and the page is a wall of two editors stacked.
	if !strings.Contains(mount, `id="billing-view-rules" style="display:none;`) {
		t.Error(`the rules view does not start hidden — both halves would render at once`)
	}
	// NO DUPLICATE IDS between the switch buttons and the view containers.
	// They shipped as billing-view-<name> on BOTH the button and the pane, so
	// document.getElementById returned the 72px-wide BUTTON for the pane and
	// every measurement was of the wrong element: the table measured 0 wide and
	// the page looked broken while the layout was fine. The ids must be unique
	// and the buttons carry a distinct suffix.
	for _, id := range []string{`billing-view-usage`, `billing-view-rules`} {
		if n := strings.Count(mount, `id="`+id+`"`); n != 1 {
			t.Errorf("id %q appears %d times; getElementById would return the wrong element", id, n)
		}
		if !strings.Contains(mount, `id="`+id+`-btn"`) {
			t.Errorf("switch button for %q is missing its -btn id", id)
		}
	}
	// Both view containers must FILL the pane. The host's tab-pane is a flex
	// column, so a plain div shrinks to its content: without flex:1/width:100%
	// the rules view measured 72px wide and its table measured 0 — the page
	// rendered "nothing" while the DOM was perfectly correct. This is exactly
	// the class of bug a DOM assertion misses and a screenshot catches.
	for _, needle := range []string{
		`id="billing-view-usage" style="flex:1`,
		`id="billing-view-rules" style="display:none;flex:1`,
	} {
		if !strings.Contains(mount, needle) {
			t.Errorf("view container does not fill the pane: %q missing — "+
				"a flex item without flex:1 collapses to content width", needle)
		}
	}
}

// TestUIExtensionMergesEveryPluginPage: two plugins contributing pages must
// BOTH appear. The old merge assigned a single field, so the second plugin
// erased the first one's page from the sidebar with no error anywhere.
func TestUIExtensionMergesEveryPluginPage(t *testing.T) {
	ps, pdir := billingVM(t)
	mk := func(name, code string) {
		if err := os.WriteFile(filepath.Join(pdir, name+".lua"), []byte(code), 0644); err != nil {
			t.Fatal(err)
		}
		if err := ps.LoadSource(name, code); err != nil {
			t.Fatalf("load %s: %v", name, err)
		}
	}
	mk("other", `
local plugin = {}
plugin.name = "other"
plugin.version = "0.1"
plugin.ui = { page = { page_id = "other-page", title = "Other", order = 90,
  mount = "<div id='other-root'></div>" } }
return plugin`)
	mk("third", `
local plugin = {}
plugin.name = "third"
plugin.version = "0.1"
plugin.ui = { pages = {
  { page_id = "third-a", title = "Third A", order = 80, mount = "<div id='ta'></div>" },
  { page_id = "third-b", title = "Third B", order = 81, mount = "<div id='tb'></div>" },
} }
return plugin`)

	ui := ps.UI()
	if ui == nil {
		t.Fatal("no merged UI")
	}
	got := map[string]bool{}
	for _, pg := range ui.Pages {
		got[pg.PageID] = true
	}
	// billing contributes exactly one page (the rule editor is a view inside it),
	// so it is listed once. The multi-page merging is exercised by the three
	// plugins added here.
	for _, want := range []string{"billing", "other-page", "third-a", "third-b"} {
		if !got[want] {
			t.Errorf("merged UI lost page %q; has %v", want, got)
		}
	}
	// A duplicate page_id must not appear twice. Two plugins claiming the same
	// id collide in the DOM (getElementById returns the first, the second pane
	// is silently unreachable), so the merge keeps the first and drops the
	// later one.
	mk("collide", `
local plugin = {}
plugin.name = "collide"
plugin.version = "0.1"
plugin.ui = { pages = {
  { page_id = "third-a", title = "Impostor", order = 79, mount = "<div id='impostor'></div>" },
} }
return plugin`)
	ui = ps.UI()
	counts := map[string]int{}
	for _, pg := range ui.Pages {
		counts[pg.PageID]++
	}
	if counts["third-a"] != 1 {
		t.Errorf("page id third-a appears %d times; a duplicate id collides in the DOM", counts["third-a"])
	}
	for _, pg := range ui.Pages {
		if pg.PageID == "third-a" && pg.Title == "Impostor" {
			t.Error("the LATER plugin won the id; first writer should keep it")
		}
	}

	// Order must be honoured so the sidebar is predictable.
	//
	// The page COUNT is not asserted: it used to be 4, and it grew every time a
	// bundled plugin added a page. A hard count here reads as "the merge is
	// broken" whenever the product gains a feature, which trains the reader to
	// bump a number instead of reading the failure. What matters is that all
	// three pages this test contributed merged, and that they came out sorted.
	for _, want := range []string{"third-a", "third-b", "other-page"} {
		if !got[want] {
			t.Errorf("page %s did not merge: %v", want, got)
		}
	}
	for i := 1; i < len(ui.Pages); i++ {
		if ui.Pages[i].Order < ui.Pages[i-1].Order {
			t.Errorf("pages out of order at %d: %d before %d",
				i, ui.Pages[i-1].Order, ui.Pages[i].Order)
		}
	}
}

// TestBillingPluginLoadedByDefault: the shipped plugin must load with no
// configuration, since seeding only happens on a fresh plugin dir.
func TestBillingPluginLoadedByDefault(t *testing.T) {
	ps, pdir := billingVM(t)
	// billing must be among the bundled plugins, not the only one. The count
	// grows with every shipped plugin and asserting it makes this test a
	// changelog detector.
	if !pluginLoaded(ps, "billing") {
		var names []string
		for _, p := range ps.List() {
			names = append(names, fmt.Sprint(p["name"]))
		}
		t.Fatalf("billing is not loaded; bundled plugins are %v", names)
	}
	if _, err := os.Stat(filepath.Join(pdir, "billing.lua")); err != nil {
		t.Errorf("billing.lua was not written to the plugin dir: %v", err)
	}
}

// TestBillingCountsDegradations: the plugin must distinguish a request that had
// to drop below the top tier from one the top tier served. Without the chain
// trace these were identical in the accounts, so a quietly degraded gateway
// looked healthy while spending more per request.
func TestBillingCountsDegradations(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"hi-tier": map[string]interface{}{"prompt": 1e-5, "completion": 1e-5},
				"lo-tier": map[string]interface{}{"prompt": 1e-6, "completion": 1e-6},
			},
		},
	})

	// Request 1: degraded. tier 1 hard-failed, tier 2 served it.
	ps.Fire(StageChainStep, map[string]interface{}{
		"kind": "slot_fail", "tier": 1, "source": "t1", "model": "hi-tier",
	})
	ps.Fire(StageChainStep, map[string]interface{}{
		"kind": "selected", "tier": 2, "source": "t2", "model": "lo-tier",
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "lo-tier", "source": "t2", "key": "***d1", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 1000,
		"degraded": true, "tier_served": 2, "time": 1750000000000,
	})

	// Request 2: clean, served by the top tier.
	ps.Fire(StageChainStep, map[string]interface{}{
		"kind": "selected", "tier": 1, "source": "t1", "model": "hi-tier",
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "hi-tier", "source": "t1", "key": "***d1", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 1000,
		"degraded": false, "tier_served": 1, "time": 1750000000000,
	})

	st := stateOf(t, ps)
	if got := st["degraded_reqs"].(float64); got != 1 {
		t.Errorf("degraded_reqs = %v, want 1 (one of the two requests dropped a tier)", got)
	}
	tiers := st["by_tier_served"].(map[string]interface{})
	if tiers["2"].(float64) != 1 {
		t.Errorf("by_tier_served[2] = %v, want 1", tiers["2"])
	}
	if tiers["1"].(float64) != 1 {
		t.Errorf("by_tier_served[1] = %v, want 1", tiers["1"])
	}
	// Cost reflects the model actually served, not the one that should have been.
	// 1000*1e-6*2 = 0.002 for the degraded one, 1000*1e-5*2 = 0.02 for the clean one.
	approx(t, "total", st["total"].(map[string]interface{})["cost"].(float64), 0.022)
}

// TestBillingAggregatesSkipReasons: skip reasons are the actionable diagnostic
// ("no schedulable slot (cooling or quota exhausted)"), so they must be
// counted. The wait time is normalised, otherwise a fresh row per request would
// appear whenever the busy-wait text varies.
func TestBillingAggregatesSkipReasons(t *testing.T) {
	ps, _ := billingVM(t)
	ps.Fire(StageChainStep, map[string]interface{}{
		"kind": "tier_skip", "tier": 1, "reason": "no schedulable slot (cooling or quota exhausted)",
	})
	ps.Fire(StageChainStep, map[string]interface{}{
		"kind": "tier_busy", "tier": 2, "reason": "no free slot within 2s",
	})
	ps.Fire(StageChainStep, map[string]interface{}{
		"kind": "tier_busy", "tier": 3, "reason": "no free slot within 2.0001s",
	})
	st := stateOf(t, ps)
	reasons := st["skip_reasons"].(map[string]interface{})
	if len(reasons) != 2 {
		t.Errorf("skip_reasons = %v, want 2 (the two variable waits must collapse to one)", reasons)
	}
	busy, ok := reasons["no free slot within <wait>"]
	if !ok {
		t.Errorf("busy reason missing; got %v", reasons)
	} else if busy.(float64) != 2 {
		t.Errorf("busy count = %v, want 2 (two different wait texts, one cause)", busy)
	}
}

// ---- prompt-cache pricing -------------------------------------------------
//
// A cached prompt token is not a fresh one. Charging the full prompt rate made a
// 1M-token request of which 900k were cache reads cost 10 USD instead of ~1.9
// — an order of magnitude, on exactly the traffic the cache exists to make
// cheap. Agent traffic replays long shared prefixes constantly, so this was the
// single largest source of over-billing in the plugin.

func TestBillingCacheHitsAreDiscounted(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"m": map[string]interface{}{"prompt": 1e-5, "completion": 1e-5},
			},
		},
	})
	// 1M prompt of which 900k cached, default discount 0.1
	// 100k fresh * 1e-5 = 1.0 ; 900k cached * 1e-5 * 0.1 = 0.9
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "key": "***c", "ok": true,
		"prompt_tokens": 1000000, "completion_tokens": 0,
		"cache_hit_tokens": 900000, "time": 1750000000000,
	})
	approx(t, "cache-discounted cost", stateOf(t, ps)["total"].(map[string]interface{})["cost"].(float64), 1.9)
}

// A per-model discount overrides the global one, because the ratio is a
// per-provider fact, not a constant.
func TestBillingCacheDiscountIsPerModel(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"free-cache": map[string]interface{}{
					"prompt": 1e-5, "completion": 0, "cache_discount": 0,
				},
				"flat": map[string]interface{}{
					"prompt": 1e-5, "completion": 0, "cache_discount": 1,
				},
			},
		},
	})
	for _, m := range []string{"free-cache", "flat"} {
		ps2, _ := billingVM(t)
		_ = ps2.SetState("billing", map[string]interface{}{
			"prices": map[string]interface{}{
				"models": map[string]interface{}{
					m: map[string]interface{}{"prompt": 1e-5, "completion": 0, "cache_discount": map[bool]float64{true: 0, false: 1}[m == "free-cache"]},
				},
			},
		})
		ps2.Fire(StageRequestEnd, map[string]interface{}{
			"model": m, "source": "s", "key": "***c", "ok": true,
			"prompt_tokens": 1000000, "cache_hit_tokens": 1000000,
			"time": 1750000000000,
		})
		want := 0.0
		if m == "flat" {
			want = 10.0
		}
		approx(t, m+" (all cached)", stateOf(t, ps2)["total"].(map[string]interface{})["cost"].(float64), want)
	}
}

// A misbehaving adapter reporting more cache hits than prompt tokens must not
// produce negative fresh tokens.
func TestBillingCacheHitClampedToPrompt(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{"m": map[string]interface{}{"prompt": 1e-5, "completion": 0}},
		},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "key": "***c", "ok": true,
		"prompt_tokens": 100, "completion_tokens": 0,
		"cache_hit_tokens": 999999, // nonsense from a broken adapter
		"time":             1750000000000,
	})
	// Clamped to 100 cached, 0 fresh => 100 * 1e-5 * 0.1
	got := stateOf(t, ps)["total"].(map[string]interface{})["cost"].(float64)
	if got < 0 {
		t.Errorf("cost = %v, must never be negative", got)
	}
	approx(t, "clamped cost", got, 0.0001)
}

// ---- unpriced traffic -----------------------------------------------------

// An unpriced model silently costing 0 is the most dangerous failure a cost
// plugin has: the bill still adds up, it just quietly under-reports, and
// nothing looks broken. It must be counted and named.
func TestBillingCountsUnpricedTraffic(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"priced": map[string]interface{}{"prompt": 1e-5},
			},
		},
	})
	// 100k+100k tokens on a model with no price entry.
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "MYSTERY-MODEL", "source": "s", "key": "***u", "ok": true,
		"prompt_tokens": 100000, "completion_tokens": 100000, "time": 1750000000000,
	})
	// A priced one, to prove the counter is selective.
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "priced", "source": "s", "key": "***u", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 0, "time": 1750000000000,
	})
	st := stateOf(t, ps)
	if got := st["unpriced_reqs"].(float64); got != 1 {
		t.Errorf("unpriced_reqs = %v, want 1 (only the mystery model)", got)
	}
	models := st["unpriced_models"].(map[string]interface{})
	if models["MYSTERY-MODEL"].(float64) != 1 {
		t.Errorf("unpriced_models = %v, want MYSTERY-MODEL counted", models)
	}
	if _, present := models["priced"]; present {
		t.Error("a priced model was counted as unpriced")
	}
	// The traffic is still recorded: "unpriced" must not mean "invisible".
	if got := st["total"].(map[string]interface{})["requests"].(float64); got != 2 {
		t.Errorf("total requests = %v, want 2 (unpriced traffic is still traffic)", got)
	}
}

// A source-only or key-only price counts as priced: any dimension covering the
// request is enough.
func TestBillingAnyDimensionCountsAsPriced(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"sources": map[string]interface{}{"flat-fee": map[string]interface{}{"per_request": 0.02}},
		},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "any-model", "source": "flat-fee", "key": "***p", "ok": true,
		"prompt_tokens": 10, "completion_tokens": 0, "time": 1750000000000,
	})
	st := stateOf(t, ps)
	if got := st["unpriced_reqs"].(float64); got != 0 {
		t.Errorf("unpriced_reqs = %v, want 0 (the source price covers it)", got)
	}
	approx(t, "flat fee", st["total"].(map[string]interface{})["cost"].(float64), 0.02)
}

// ---- 峰谷 / 时段定价 ---------------------------------------------------
//
// commandcode 的 DeepSeek V4 系列就是这么定价的：非高峰 17h/天，高峰 01-04 &
// 06-10 UTC 工作日，价格恰好 2 倍。这类规则用静态价目无法表达，而算错方向是
// 静默的——不会报错，只会一直算错。
//
// 时间判据的可测性：os.date("!%H") 取 UTC 小时。测试通过选择"确定落在窗口内"
// 与"确定落在窗口外"的时段来判定，不去伪造时钟（Lua 侧没有可注入的时钟，
// 伪造反而会让测试与真实行为脱节）。

func TestBillingPeakWindowDoublesOutsidePeak(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"dsv41": map[string]interface{}{
					"prompt": 1.5e-7, "completion": 6e-7,
					"peak": map[string]interface{}{
						"multiplier": 2,
						// 全部 7 天全部 24 小时 ⇒ 永远命中
						"windows": []interface{}{
							map[string]interface{}{
								"days":  []interface{}{0, 1, 2, 3, 4, 5, 6},
								"hours": []interface{}{[]interface{}{0, 23}},
							},
						},
					},
				},
			},
		},
	})
	// 1000 prompt + 1000 completion，非高峰 0.00075 → 命中峰谷 ×2 = 0.0015
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "dsv41", "source": "commandcode", "key": "***pk", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 1000, "time": 1750000000000,
	})
	got := stateOf(t, ps)["total"].(map[string]interface{})["cost"].(float64)
	want := (1000*1.5e-7 + 1000*6e-7) * 2
	approx(t, "always-peak cost", got, want)
}

// 一个不存在的窗口（UTC 25 点不存在）⇒ 永不命中 ⇒ 静态价。
func TestBillingPeakWindowNotHit(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"dsv41": map[string]interface{}{
					"prompt": 1.5e-7, "completion": 6e-7,
					"peak": map[string]interface{}{
						"multiplier": 2,
						// 星期 = {0..6} 但小时窗写成 [99,100]：永远不可能命中
						"windows": []interface{}{
							map[string]interface{}{
								"days":  []interface{}{0, 1, 2, 3, 4, 5, 6},
								"hours": []interface{}{[]interface{}{99, 100}},
							},
						},
					},
				},
			},
		},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "dsv41", "source": "commandcode", "key": "***pk", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 1000, "time": 1750000000000,
	})
	got := stateOf(t, ps)["total"].(map[string]interface{})["cost"].(float64)
	approx(t, "never-peak cost", got, 1000*1.5e-7+1000*6e-7)
}

// 星期不匹配 ⇒ 不命中。这一条正是"用本地时区算会整体偏移"要防的东西：
// 周日按 UTC 算，用本地时区可能算成周六而错误地命中工作日窗口。
func TestBillingPeakWindowDayMismatch(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"dsv41": map[string]interface{}{
					"prompt": 1.5e-7, "completion": 6e-7,
					"peak": map[string]interface{}{
						"multiplier": 2,
						// 只在"不存在的星期 7"上开窗（os.date %w 只到 0..6）
						"windows": []interface{}{
							map[string]interface{}{
								"days":  []interface{}{7},
								"hours": []interface{}{[]interface{}{0, 23}},
							},
						},
					},
				},
			},
		},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "dsv41", "source": "commandcode", "key": "***pk", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 1000, "time": 1750000000000,
	})
	got := stateOf(t, ps)["total"].(map[string]interface{})["cost"].(float64)
	if got > (1000*1.5e-7+1000*6e-7)*1.5 {
		t.Errorf("cost = %v: a non-matching weekday must not trigger the peak multiplier", got)
	}
}

// 没有 peak 规则的条目完全不受影响（向后兼容）。
func TestBillingNoPeakRuleIsUnaffected(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"plain": map[string]interface{}{"prompt": 1e-6, "completion": 2e-6},
			},
		},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "plain", "source": "s", "key": "***n", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 1000, "time": 1750000000000,
	})
	approx(t, "no-peak cost", stateOf(t, ps)["total"].(map[string]interface{})["cost"].(float64), 1000*1e-6+1000*2e-6)
}

// 缓存读价【不】跟着峰谷翻倍：它是另一条上游费率，观测到的非峰谷价里已经含了
// 自己的折扣，跟着翻倍会把两个折扣叠在一起。
func TestBillingPeakDoesNotDoubleCacheRead(t *testing.T) {
	ps, _ := billingVM(t)
	_ = ps.SetState("billing", map[string]interface{}{
		"prices": map[string]interface{}{
			"models": map[string]interface{}{
				"dsv41": map[string]interface{}{
					"prompt": 1.5e-7, "completion": 6e-7, "cache_discount": 0.02,
					"peak": map[string]interface{}{
						"multiplier": 2,
						"windows": []interface{}{map[string]interface{}{
							"days":  []interface{}{0, 1, 2, 3, 4, 5, 6},
							"hours": []interface{}{[]interface{}{0, 23}},
						}},
					},
				},
			},
		},
	})
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "dsv41", "source": "commandcode", "key": "***c", "ok": true,
		"prompt_tokens": 1000000, "completion_tokens": 0,
		"cache_hit_tokens": 1000000, "time": 1750000000000,
	})
	// 全部缓存命中 ⇒ 只按 cache 价 = prompt * 0.02，且不翻倍
	got := stateOf(t, ps)["total"].(map[string]interface{})["cost"].(float64)
	approx(t, "cache-only cost (not doubled)", got, 1e6*1.5e-7*0.02)
}

// TestBillingTracksCacheUsage is the guard for the gap production exposed: the
// gateway had prompt_cache_hit_tokens and costFor() priced the cache leg, but no
// bucket recorded the number. On a gateway where 99.88% of prompt tokens were
// cache reads, the report showed a prompt_tokens figure with no way to tell that
// most of it was cached.
func TestBillingTracksCacheUsage(t *testing.T) {
	ps, _ := billingVM(t)

	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "key": "k", "ok": true,
		"prompt_tokens": 1000, "completion_tokens": 50,
		"cache_hit_tokens": 900, "cache_reported": true,
	})
	// A second request from a source that does not report caching at all.
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m2", "source": "s2", "ok": true,
		"prompt_tokens": 100, "completion_tokens": 10,
	})

	st := ps.State("billing").(map[string]interface{})
	total := st["total"].(map[string]interface{})
	if total["cache_hit_tokens"] != float64(900) {
		t.Errorf("total.cache_hit_tokens = %v, want 900", total["cache_hit_tokens"])
	}
	if total["cache_fresh_tokens"] != float64(200) {
		t.Errorf("total.cache_fresh_tokens = %v, want 200 (1000-900 + 100)", total["cache_fresh_tokens"])
	}
	// Only the first request reported a cache number.
	if total["cache_reported_reqs"] != float64(1) {
		t.Errorf("★ total.cache_reported_reqs = %v, want 1 — a source that never "+
			"reports cache usage must be distinguishable from one reporting zero hits",
			total["cache_reported_reqs"])
	}

	// Per-source separation.
	bySrc := st["by_source"].(map[string]interface{})
	s1 := bySrc["s"].(map[string]interface{})
	if s1["cache_hit_tokens"] != float64(900) {
		t.Errorf("by_source[s].cache_hit_tokens = %v, want 900", s1["cache_hit_tokens"])
	}
	s2 := bySrc["s2"].(map[string]interface{})
	if s2["cache_reported_reqs"] != float64(0) {
		t.Errorf("by_source[s2].cache_reported_reqs = %v, want 0", s2["cache_reported_reqs"])
	}
	if s2["cache_fresh_tokens"] != float64(100) {
		t.Errorf("by_source[s2].cache_fresh_tokens = %v, want 100", s2["cache_fresh_tokens"])
	}
}

// TestBillingCacheBucketsSurviveOlderStateFiles: a state file written before these
// fields existed must not crash the hook. `nil + number` is an error in Lua, and
// a hook that throws stops accounting for that request entirely — which is how a
// billing gap turns into a silent one.
func TestBillingCacheBucketsSurviveOlderStateFiles(t *testing.T) {
	ps, _ := billingVM(t)
	// Simulate a state restored from an older build: buckets without the new keys.
	legacy := map[string]interface{}{
		"total": map[string]interface{}{
			"cost": 1.0, "requests": float64(5), "prompt_tokens": float64(500),
			"completion_tokens": float64(50), "failures": float64(0),
		},
		"by_source": map[string]interface{}{
			"legacy": map[string]interface{}{"cost": float64(0), "requests": float64(5),
				"prompt_tokens": float64(500), "completion_tokens": float64(50), "failures": float64(0)},
		},
		"by_model": map[string]interface{}{}, "by_key": map[string]interface{}{},
		"by_day": map[string]interface{}{}, "started": float64(0),
	}
	if err := ps.SetState("billing", legacy); err != nil {
		t.Fatalf("SetState: %v", err)
	}
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "legacy", "ok": true,
		"prompt_tokens": 100, "completion_tokens": 10,
		"cache_hit_tokens": 60, "cache_reported": true,
	})
	if len(ps.HookErrors()) != 0 {
		t.Fatalf("hook error on a legacy state: %v", ps.HookErrors())
	}
	st := ps.State("billing").(map[string]interface{})
	tot := st["total"].(map[string]interface{})
	if tot["requests"] != float64(6) {
		t.Errorf("requests = %v, want 6 (5 legacy + 1 new)", tot["requests"])
	}
	if tot["cache_hit_tokens"] != float64(60) {
		t.Errorf("cache_hit_tokens = %v, want 60", tot["cache_hit_tokens"])
	}
	lg := st["by_source"].(map[string]interface{})["legacy"].(map[string]interface{})
	if lg["cache_hit_tokens"] != float64(60) {
		t.Errorf("legacy bucket cache_hit_tokens = %v, want 60", lg["cache_hit_tokens"])
	}
}

// TestBillingCacheHitClampedInStats: costFor clamps the cache leg, so the
// recorded numbers must be clamped the same way. A provider that reports more
// cache hits than prompt tokens must not produce negative fresh tokens.
func TestBillingCacheHitClampedInStats(t *testing.T) {
	ps, _ := billingVM(t)
	ps.Fire(StageRequestEnd, map[string]interface{}{
		"model": "m", "source": "s", "ok": true,
		"prompt_tokens": 100, "completion_tokens": 5,
		"cache_hit_tokens": 5000, "cache_reported": true,
	})
	st := ps.State("billing").(map[string]interface{})
	tot := st["total"].(map[string]interface{})
	if tot["cache_hit_tokens"] != float64(100) {
		t.Errorf("★ cache_hit_tokens = %v, want 100 (clamped to prompt_tokens)",
			tot["cache_hit_tokens"])
	}
	if tot["cache_fresh_tokens"] != float64(0) {
		t.Errorf("★ cache_fresh_tokens = %v, want 0, never negative",
			tot["cache_fresh_tokens"])
	}
}