package lua

import (
	"encoding/json"
	"os/exec"
	"strings"
	"testing"
)

// runBillingPage executes the billing page's mount script under node against a
// DOM stub, drives the period selector, and returns what ended up on screen.
//
// It asserts against RENDERED output rather than the plugin's internal
// helpers. Reaching into the IIFE for daysInWindow/rescale needs a test-only
// hook in the plugin, and the first version of this file took a long detour
// through such a hook: the harness's fake `Date` broke toISOString(), the
// plugin script aborted before assigning the hook, and every assertion
// compared "" against a real value. The rendered tables are the contract that
// actually matters, they need no hook, and they cannot pass if the rescale is
// wrong — which is exactly the bug class under test.
func runBillingPage(t *testing.T, todayISO, period, captureID string) string {
	t.Helper()
	node, err := exec.LookPath("node")
	if err != nil {
		t.Skipf("node not available (%v)", err)
	}
	page, _ := billingUI(t)
	js := strings.Join(extractScripts(page), "\n")
	if !strings.Contains(js, "__billing_setPeriod") {
		t.Fatal("billing page exposes no period selector")
	}

	harness := `
global.window = global;
global.__written = [];
global.__errors = [];
var __realErr = console.error;
console.error = function () {
  global.__errors.push("console.error: " + Array.prototype.map.call(arguments, function (a) {
    return (a && a.message) ? a.message : String(a);
  }).join(" "));
  __realErr.apply(console, arguments);
};
process.on("uncaughtException", function (e) { global.__errors.push("uncaught: " + String(e && e.message || e)); });
process.on("unhandledRejection", function (e) { global.__errors.push("unhandled: " + String(e && e.message || e)); });

// Pin "now" for the window under test.
//
// Two earlier attempts were wrong here, and both looked like product bugs:
// replacing the Date constructor wholesale breaks toISOString/UTC; and
// subclassing (setting __FakeDate.prototype = __RealDate.prototype while
// returning __RealDate instances) leaves instances WITHOUT a working
// getUTCDay, so the week window came out NaN and every rendered day became
// "Invalid time value". A Proxy over the real constructor intercepts only the
// zero-argument call and leaves instances — and therefore every prototype
// method — completely untouched.
var __NOW_MS = new Date("` + todayISO + `T12:34:56Z").getTime();
var __RealDate = global.Date;
var __PatchedDate = new Proxy(__RealDate, {
  construct: function (target, args) {
    // Reflect.construct, not a hand-spelled argument list: writing
    // new target(a, b, c, d, e, f, g) passes seven explicit undefineds for a
    // one-argument call, which Date reads as year..millisecond fields and turns
    // into an Invalid Date. The symptom was a week window rendering
    // "Invalid time value" for every day — a harness fault indistinguishable
    // from a product bug.
    if (args.length === 0) return Reflect.construct(target, [__NOW_MS]);
    return Reflect.construct(target, args);
  },
  apply: function () { return new __RealDate(__NOW_MS); }
});
__PatchedDate.now = function () { return __NOW_MS; };
__PatchedDate.UTC = __RealDate.UTC;
__PatchedDate.parse = __RealDate.parse;
__PatchedDate.prototype = __RealDate.prototype;
global.Date = __PatchedDate;

global.document = {
  getElementById: function (id) {
    if (!global.__els) global.__els = {};
    if (!global.__els[id]) global.__els[id] = {
      style: {}, dataset: {}, classList: { add: function(){}, remove: function(){} },
      options: [{value:"day"},{value:"week"},{value:"month"},{value:"all"}],
      set innerHTML(v) { if (v && String(v).trim()) global.__written.push(id); this.__h = v; },
      get innerHTML() { return this.__h || ""; },
      set textContent(v) { if (v !== undefined && String(v).trim()) global.__written.push(id); this.__t = v; },
      get textContent() { return this.__t || ""; },
      set innerText(v) { if (v !== undefined && String(v).trim()) global.__written.push(id); this.__i = v; },
      get innerText() { return this.__i || ""; },
      appendChild: function(){}, querySelector: function(){ return null; },
      querySelectorAll: function(){ return []; }, addEventListener: function(){}
    };
    return global.__els[id];
  },
  createElement: function () { return { style: {}, dataset: {}, appendChild: function(){}, setAttribute: function(){} }; },
  addEventListener: function () {},
};

// Fixture days carry deliberately distinctive costs so a fold over the wrong
// subset still produces a number, and only a mismatch shows it. 2026-01-05/06/07
// are Monday/Tuesday/Wednesday; 2025-12-01 is far outside any window here.
global.__st = {
  currency: "USD",
  total: { cost: 999, requests: 999, prompt_tokens: 999999 },
  by_source: { LIFETIMESRC: { cost: 999, requests: 999 } },
  by_model: { LIFETIMEMODEL: { cost: 999, requests: 999 } },
  by_key: { LIFETIMEKEY: { cost: 999, requests: 999 } },
  by_day: {
    "2026-01-05": { cost: 10, requests: 1, prompt_tokens: 100, completion_tokens: 10, failures: 0 },
    "2026-01-06": { cost: 20, requests: 2, prompt_tokens: 200, completion_tokens: 20, failures: 1 },
    "2026-01-07": { cost: 30, requests: 3, prompt_tokens: 300, completion_tokens: 30, failures: 0 },
    "2025-12-01": { cost: 777, requests: 77, prompt_tokens: 7700 }
  },
  by_day_src: {
    "2026-01-05": { srcA: { cost: 10, requests: 1 } },
    "2026-01-06": { srcA: { cost: 20, requests: 2 }, srcB: { cost: 5, requests: 1 } },
    "2026-01-07": { srcA: { cost: 30, requests: 3 } },
    "2025-12-01": { srcOLD: { cost: 777, requests: 77 } }
  },
  by_day_model: {
    "2026-01-05": { mA: { cost: 10, requests: 1 } },
    "2026-01-06": { mA: { cost: 20, requests: 2 } },
    "2026-01-07": { mA: { cost: 30, requests: 3 } }
  },
  by_day_key: {
    "2026-01-05": { kA: { cost: 10, requests: 1 } },
    "2026-01-06": { kA: { cost: 20, requests: 2 } },
    "2026-01-07": { kA: { cost: 30, requests: 3 } }
  },
  degraded_reqs: 4242, unpriced_reqs: 77
};
global.fetch = function () {
  return Promise.resolve({ ok: true, json: function () {
    return Promise.resolve({ plugin: "billing", state: global.__st });
  }});
};
global.pluginAPI = { onTabShown: function () {}, lang: "en" };
`
	script := harness + "\n" + js + "\n" +
		"__billing_setPeriod(" + jsonStr(period) + ");\n" +
		// Let the period-triggered refresh() settle before reading the DOM.
		"setTimeout(function () {\n" +
		"  var el = document.getElementById(" + jsonStr(captureID) + ");\n" +
		"  console.log('__CAPTURE__' + JSON.stringify({\n" +
		"    html: el ? String(el.innerHTML) : '(missing)',\n" +
		"    kpis: String(document.getElementById('billing-kpis').innerHTML),\n" +
		"    sel: String(document.getElementById('billing-period').value),\n" +
		"    errors: global.__errors\n" +
		"  }));\n" +
		"}, 60);\n"

	cmd := exec.Command(node, "-e", script)
	out, err := cmd.CombinedOutput()
	if err != nil {
		t.Fatalf("node execution failed: %v\n%s", err, out)
	}
	o := string(out)
	idx := strings.Index(o, "__CAPTURE__")
	if idx < 0 {
		t.Fatalf("no capture in node output (the plugin script aborted?):\n%s", o)
	}
	raw := strings.TrimSpace(o[idx+len("__CAPTURE__"):])
	if nl := strings.IndexAny(raw, "\r\n"); nl >= 0 {
		raw = raw[:nl]
	}
	var got struct {
		HTML   string   `json:"html"`
		KPIs   string   `json:"kpis"`
		Sel    string   `json:"sel"`
		Errors []string `json:"errors"`
	}
	if err := json.Unmarshal([]byte(raw), &got); err != nil {
		t.Fatalf("capture is not JSON: %v\n%s", err, raw)
	}
	if len(got.Errors) > 0 {
		t.Fatalf("billing script reported errors: %v", got.Errors)
	}
	if got.Sel != period {
		t.Errorf("selector shows %q after setting %q — the change handler did not take", got.Sel, period)
	}
	return got.HTML + "\n@@KPI@@\n" + got.KPIs
}

func jsonStr(s string) string {
	b, _ := json.Marshal(s)
	return string(b)
}

// TestBillingPeriodDayShowsOnlyThatDay checks the one-day window end to end:
// the tables must carry that day's rows and drop every other day, and the
// lifetime sentinel (999 / LIFETIMESRC) must appear nowhere.
func TestBillingPeriodDayShowsOnlyThatDay(t *testing.T) {
	got := runBillingPage(t, "2026-01-07", "day", "billing-by-source")
	if strings.Contains(got, "LIFETIME") || strings.Contains(got, "999") {
		t.Errorf("a one-day view still shows lifetime figures:\n%s", got)
	}
	if strings.Contains(got, "srcB") {
		t.Errorf("a one-day view shows srcB, which only had traffic on 01-06:\n%s", got)
	}
	if strings.Contains(got, "srcOLD") {
		t.Errorf("a one-day view shows a day from 2025-12:\n%s", got)
	}
	if !strings.Contains(got, "srcA") {
		t.Errorf("a one-day view lost the only source that had traffic that day:\n%s", got)
	}
	// The KPI total must be that day's cost (30), not the week (60) and not
	// the lifetime sentinel (999).
	if !strings.Contains(got, "30") {
		t.Errorf("KPI does not show the day's cost 30:\n%s", got)
	}
}

// TestBillingPeriodWeekSumsThreeDays is the arithmetic: Mon+Wed rows and a
// total of 60. A window that started on Sunday or ended early still renders
// tables, so only the number distinguishes it.
func TestBillingPeriodWeekSumsThreeDays(t *testing.T) {
	// 2026-01-07 is a Wednesday: the ISO week holds 01-05, 01-06, 01-07.
	got := runBillingPage(t, "2026-01-07", "week", "billing-by-source")
	if strings.Contains(got, "srcOLD") || strings.Contains(got, "LIFETIME") {
		t.Errorf("weekly view leaks out-of-window or lifetime rows:\n%s", got)
	}
	// srcA = 10+20+30 = 60, srcB = 5 (only 01-06, but inside the week).
	if !strings.Contains(got, "60") {
		t.Errorf("weekly total should be 60, got:\n%s", got)
	}
	if !strings.Contains(got, "srcB") {
		t.Errorf("weekly view dropped srcB, whose only day (01-06) is in the window:\n%s", got)
	}
}

// TestBillingPeriodSundayReachesBackToMonday pins the ISO-week Monday rule
// from the other side. On Sunday 2026-01-11 the week that already ended is
// Mon 05..Sun 11, so all three fixture days are in it; a start-on-Sunday bug
// would still include 01-07 and pass, so this case is paired with the
// weekday case above rather than relied on alone.
func TestBillingPeriodSundayReachesBackToMonday(t *testing.T) {
	got := runBillingPage(t, "2026-01-11", "week", "billing-by-source")
	if !strings.Contains(got, "60") {
		t.Errorf("Sunday's week view should still total 60:\n%s", got)
	}
	// And the Monday view must NOT include Sunday's (nonexistent) traffic.
	gotMon := runBillingPage(t, "2026-01-05", "day", "billing-by-source")
	if strings.Contains(gotMon, "30") {
		t.Errorf("Monday's single day view shows Wednesday's cost 30:\n%s", gotMon)
	}
	if !strings.Contains(gotMon, "10") {
		t.Errorf("Monday's day view lost Monday's own cost 10:\n%s", gotMon)
	}
}

// TestBillingPeriodKpiTotalMatchesWindowDays pins the KPI total itself.
//
// The dimension-table tests above cannot catch a broken window or a broken
// fold: by_source is computed from the per-day DIMENSION map, independently of
// the total. Mutation verification proved it — disabling the total fold, and
// shifting the ISO-week start to Sunday, both left every earlier test green.
// The total is derived from by_day, so it is the one value that moves when
// either the window membership or the accumulation is wrong.
func TestBillingPeriodKpiTotalMatchesWindowDays(t *testing.T) {
	kpis := func(t *testing.T, today, period string) string {
		t.Helper()
		return runBillingPage(t, today, period, "billing-by-source")
	}
	// 2026-01-07 is a Wednesday; fixture days are 05(10) 06(20) 07(30).
	// KPI renders through fmtInt, so 30 -> "30", 60 -> "60".
	if got := kpis(t, "2026-01-07", "day"); !strings.Contains(got, "30") {
		t.Errorf("day KPI should show that day's cost 30:\n%s", got)
	}
	if got := kpis(t, "2026-01-07", "week"); !strings.Contains(got, "60") {
		t.Errorf("week KPI should total 10+20+30 = 60:\n%s", got)
	}
	// Sunday 2026-01-11: the ISO week Mon 05..Sun 11 still holds all three days.
	if got := kpis(t, "2026-01-11", "week"); !strings.Contains(got, "60") {
		t.Errorf("Sunday's week KPI should still total 60:\n%s", got)
	}
	// The Monday rule from the negative side. A window that started on SUNDAY
	// would cover Sun 11..Sat 17 and contain none of the fixture days, giving
	// a total of 0 — so this case is what makes the +6 shift observable. The
	// positive case alone cannot distinguish it: shifting the start one day
	// later still happens to contain 01-07.
	if got := kpis(t, "2026-01-11", "day"); !strings.Contains(got, "0") {
		t.Errorf("Sunday's single-day window has no fixture traffic and must total 0:\n%s", got)
	}
	// Monday 2026-01-12 begins a new week; it contains no fixture days.
	if got := kpis(t, "2026-01-12", "week"); !strings.Contains(got, "0") {
		t.Errorf("an empty week should report 0, not stale data:\n%s", got)
	}
	// ...whereas the Monday-to-Sunday week that just ended does.
	if got := kpis(t, "2026-01-12", "day"); !strings.Contains(got, "0") {
		t.Errorf("Monday the 12th has no fixture traffic and must total 0:\n%s", got)
	}
}

// TestBillingPeriodDimensionFoldSumsAcrossDays covers the per-dimension
// accumulation. Asserting "60 appears somewhere" was NOT enough: mutation
// verification showed a fold that keeps only the last day still passed,
// because 60 also appears in the KPI total and in a token column. The
// assertion must therefore pin srcA's own cost cell, not the page's text.
func TestBillingPeriodDimensionFoldSumsAcrossDays(t *testing.T) {
	got := runBillingPage(t, "2026-01-07", "week", "billing-by-source")
	// srcA exists on all three days at 10/20/30. Summed = 60; last-only = 30.
	if !strings.Contains(got, "USD 60.0000") {
		t.Errorf("weekly by-source did not sum srcA across days (want USD 60.0000, "+
			"last-day-only would be USD 30.0000):\n%s", got)
	}
	// srcB exists only on 01-06 at 5, inside the window, so it must survive at
	// exactly its own value.
	if !strings.Contains(got, "USD 5.0000") {
		t.Errorf("weekly by-source lost or altered srcB (want USD 5.0000):\n%s", got)
	}
	// srcA's summed cost must also differ from its last-day value in the
	// rendered table, so an overwrite cannot masquerade as a sum.
	if strings.Count(got, "USD 60.0000") < 2 {
		t.Errorf("expected the summed 60 in both the table and the KPI:\n%s", got)
	}
}

// state untouched, including the lifetime sentinel and the lifetime-only
// degraded counter. Without this control, a rescale that silently degraded
// into "always empty" would pass the narrow-window tests.
// TestBillingPeriodAllStaysLifetime is the control: "all" must keep the stored
// state untouched. Without it, a rescale that silently degraded into "always
// empty" would pass every narrow-window test above.
func TestBillingPeriodAllStaysLifetime(t *testing.T) {
	got := runBillingPage(t, "2026-01-07", "all", "billing-by-source")
	if !strings.Contains(got, "LIFETIMESRC") && !strings.Contains(got, "999") {
		t.Errorf("the all-time view dropped the lifetime figures:\n%s", got)
	}
	// 4242 is the lifetime degraded_reqs; it has no day-keyed tally, so it
	// must remain visible when the window is "all". The KPI goes through
	// fmtInt, so it renders grouped ("4,242") — assert the rendered form.
	if !strings.Contains(got, "4,242") {
		t.Errorf("the all-time view should still show the lifetime degraded count:\n%s", got)
	}
}

// TestBillingPeriodHidesLifetimeOnlyCounters is the mismatch the period view
// exists to remove: degraded/unpriced have no day-keyed tally, so printing
// the lifetime number next to a per-window cost is misleading. They must be
// hidden, not merely relabelled.
func TestBillingPeriodHidesLifetimeOnlyCounters(t *testing.T) {
	got := runBillingPage(t, "2026-01-07", "day", "billing-by-source")
	if strings.Contains(got, "4,242") || strings.Contains(got, "Degraded") {
		t.Errorf("a one-day view still shows the lifetime degraded counter:\n%s", got)
	}
	// ...while "all" does show it (covered above), so this is not just a
	// dictionary that lost the words.
	if !strings.Contains(runBillingPage(t, "2026-01-07", "all", "billing-by-source"), "4,242") {
		t.Error("the all-time view lost the degraded counter — the hide is not period-scoped")
	}
}