package wshub

import (
	"encoding/binary"
	"math"
	"testing"
)

// fillRing writes n samples at the given rate starting at t0.
func fillRing(rb *sigRing, t0 float64, rate float64, n int) {
	ts := make([]float64, n)
	vs := make([]float64, n)
	for i := range ts {
		ts[i] = t0 + float64(i)/rate
		vs[i] = math.Sin(float64(i))
	}
	rb.write(ts, vs)
}

func TestRingGrowPreservesSamples(t *testing.T) {
	rb := newSigRing(100)
	// Overflow the ring so the retained window starts mid-buffer.
	fillRing(rb, 0, 1000, 250)

	beforeT, beforeV := rb.slice(-1e9, 1e9)
	if len(beforeT) != 100 {
		t.Fatalf("pre-grow fill = %d, want 100", len(beforeT))
	}
	if !rb.grow(1000) {
		t.Fatal("grow(1000) returned false")
	}
	if rb.capacity() != 1000 {
		t.Fatalf("capacity = %d, want 1000", rb.capacity())
	}
	afterT, afterV := rb.slice(-1e9, 1e9)
	if len(afterT) != len(beforeT) {
		t.Fatalf("post-grow fill = %d, want %d", len(afterT), len(beforeT))
	}
	for i := range beforeT {
		if afterT[i] != beforeT[i] || afterV[i] != beforeV[i] {
			t.Fatalf("sample %d changed across grow", i)
		}
	}

	// Further writes must keep landing in order rather than wrapping early.
	fillRing(rb, 1.0, 1000, 500)
	if n, _ := rb.stats(); n != 600 {
		t.Fatalf("fill after grow = %d, want 600", n)
	}

	// Shrinking is refused.
	if rb.grow(10) {
		t.Fatal("grow(10) shrank the ring")
	}
}

func TestRingStatsMeasuresRate(t *testing.T) {
	rb := newSigRing(10000)
	fillRing(rb, 0, 1000, 1000) // 1 kHz
	n, span := rb.stats()
	if n != 1000 {
		t.Fatalf("count = %d, want 1000", n)
	}
	rate := float64(n) / span
	if math.Abs(rate-1001) > 5 { // n samples span (n-1) intervals
		t.Fatalf("rate = %v, want ~1000", rate)
	}
}

// A long trigger window must grow the rings to hold it: a fixed sample-count
// ring covers a fraction of a second at a high rate, which is what made 60 s
// captures come back with only their tail populated.
func TestRetuneRingsCoversTriggerWindow(t *testing.T) {
	h := NewHub()
	rb := newSigRing(6000) // 6 s at 1 kHz — far short of a 60 s window
	fillRing(rb, 0, 1000, 6000)
	h.rings["s1:sig"] = rb

	h.trigger.SetConfig(trigConfig{signalKey: "s1:sig", edge: "rising",
		windowSec: 60, prePercent: 20, mode: "normal"})

	h.retuneRings(1000)

	// 60 s at 1 kHz is 60 k samples: growing to the budget holds them verbatim.
	if got := rb.capacity(); got < 60000 {
		t.Fatalf("capacity = %d, want >= 60000 to hold a 60 s window", got)
	}
	if got := rb.bucketSize(); got != 1 {
		t.Fatalf("bucket = %d, want 1: the window fits at full rate", got)
	}
}

// Past the budget the window is kept by reducing resolution, not by dropping
// its head — the whole point of the min/max buckets.
func TestRetuneRingsBucketsWhenTheWindowExceedsTheBudget(t *testing.T) {
	h := NewHub()
	rb := newSigRing(1000)
	fillRing(rb, 0, 1e6, 100_000) // 1 MSps
	h.rings["s1:sig"] = rb

	h.trigger.SetConfig(trigConfig{signalKey: "s1:sig", windowSec: 60, mode: "normal"})
	h.retuneRings(1000)

	if got := rb.capacity(); got != defaultRingPts {
		t.Fatalf("capacity = %d, want the budget %d", got, defaultRingPts)
	}
	// 60 s at 1 MSps is 60 M samples in a 10 M-point buffer, so each stored
	// pair must cover at least 12 source samples.
	bucket := rb.bucketSize()
	if bucket < 12 {
		t.Fatalf("bucket = %d, too fine to fit 60 M samples in %d points", bucket, rb.capacity())
	}
	if covered := float64(rb.capacity()) / 2 * float64(bucket) / 1e6; covered < 60 {
		t.Fatalf("buffer covers %.1f s, want the whole 60 s window", covered)
	}
}

// A raised budget buys resolution back: the same window is held verbatim.
func TestRetuneRingsHonoursRaisedBudget(t *testing.T) {
	h := NewHub()
	h.SetRingBudget(80_000_000)
	rb := newSigRing(1000)
	fillRing(rb, 0, 1e6, 100_000) // 1 MSps
	h.rings["s1:sig"] = rb

	h.trigger.SetConfig(trigConfig{signalKey: "s1:sig", windowSec: 60, mode: "normal"})
	h.retuneRings(1000)

	if got := rb.bucketSize(); got != 1 {
		t.Fatalf("bucket = %d, want 1: 60 M samples fit in an 80 M-point buffer", got)
	}
}

func TestSetRingBudgetBounds(t *testing.T) {
	h := NewHub()
	h.SetRingBudget(0)
	if got := h.ringBudget(); got != defaultRingPts {
		t.Fatalf("ringBudget after 0 = %d, want the default %d", got, defaultRingPts)
	}
	// Never below the depth a freshly configured ring already has, or the
	// budget would ask for a shrink the ring refuses anyway.
	h.SetRingBudget(10)
	if got := h.ringBudget(); got != ringCapInitial {
		t.Fatalf("ringBudget after 10 = %d, want the floor %d", got, ringCapInitial)
	}
}

func TestRetuneRingsIsThrottled(t *testing.T) {
	h := NewHub()
	h.SetRingBudget(250_000)
	rb := newSigRing(250_000)
	fillRing(rb, 0, 1e6, 100_000)
	h.rings["s1:sig"] = rb
	h.trigger.SetConfig(trigConfig{signalKey: "s1:sig", windowSec: 10, mode: "normal"})

	h.retuneRings(100)
	first := rb.bucketSize()
	if first <= 1 {
		t.Fatalf("bucket = %d, expected a reduction for 10 s at 1 MSps in 250 k points", first)
	}
	// Same second: the sweep must not run again even though a bigger window
	// is now configured.
	h.trigger.SetConfig(trigConfig{signalKey: "s1:sig", windowSec: 600, mode: "normal"})
	h.retuneRings(100.5)
	if rb.bucketSize() != first {
		t.Fatalf("sweep ran inside the throttle window")
	}
	h.retuneRings(200)
	if rb.bucketSize() <= first {
		t.Fatalf("sweep did not run after the throttle window elapsed")
	}
}

// With no trigger armed and no client saying otherwise, the rings are sized for
// the default live window — live mode needs the buffers just as much as a
// capture does.
func TestRetuneRingsSizesForTheLiveWindow(t *testing.T) {
	h := NewHub()
	rb := newSigRing(1000)
	fillRing(rb, 0, 1e6, 100_000) // 1 MSps: 10 s does not fit in 1000 points
	h.rings["s1:sig"] = rb
	// No signal configured → trigger inactive, so the live window governs.
	h.trigger.SetConfig(trigConfig{windowSec: 600, mode: "normal"})

	h.retuneRings(100)

	if got := rb.capacity(); got != defaultRingPts {
		t.Fatalf("capacity = %d, want the budget %d", got, defaultRingPts)
	}
	// defaultLiveWindowSec at 1 MSps is exactly the budget, so no reduction.
	if got := rb.bucketSize(); got != 1 {
		t.Fatalf("bucket = %d, want 1 for the default live window", got)
	}
}

func TestRingBucketForCoversTheWindow(t *testing.T) {
	cases := []struct {
		rate, window float64
		capacity     int
		want         int
	}{
		{1000, 10, 1_000_000, 1},    // 10 k samples in 1 M points: verbatim
		{1e6, 10, 10_000_000, 1},    // exactly the budget: still verbatim
		{1e6, 60, 10_000_000, 15},   // 60 M samples, 1.25x headroom
		{1e6, 600, 10_000_000, 150}, // 600 s still fits, at 1/150 resolution
		{0, 10, 1_000_000, 1},       // no rate measured yet
		{1000, 0, 1_000_000, 1},     // no window
	}
	for _, c := range cases {
		if got := ringBucketFor(c.rate, c.window, c.capacity); got != c.want {
			t.Errorf("ringBucketFor(%v, %v, %d) = %d, want %d",
				c.rate, c.window, c.capacity, got, c.want)
		}
	}
}

// decodeCapture pulls the per-signal point counts out of a v2 capture frame.
func decodeCapture(t *testing.T, buf []byte) map[string]int {
	t.Helper()
	if buf[0] != 2 {
		t.Fatalf("frame version = %d, want 2", buf[0])
	}
	off := 1 + 8 + 8 + 8
	nSig := int(binary.LittleEndian.Uint32(buf[off:]))
	off += 4
	out := make(map[string]int, nSig)
	for i := 0; i < nSig; i++ {
		kl := int(binary.LittleEndian.Uint16(buf[off:]))
		off += 2
		key := string(buf[off : off+kl])
		off += kl
		n := int(binary.LittleEndian.Uint32(buf[off:]))
		off += 4
		off += n * 16
		out[key] = n
	}
	if off != len(buf) {
		t.Fatalf("decoded %d of %d bytes", off, len(buf))
	}
	return out
}

// A 60 s window at a high rate is hundreds of megabytes raw; the capture frame
// must be decimated so it can actually reach a client.
func TestBuildTriggerCaptureDecimates(t *testing.T) {
	h := NewHub()
	rb := newSigRing(200000)
	fillRing(rb, 0, 100000, 200000) // 2 s at 100 kSps
	h.rings["s1:sig"] = rb

	buf := h.buildTriggerCapture(1.0, 1.0, 1.0)
	if buf == nil {
		t.Fatal("no capture frame built")
	}
	counts := decodeCapture(t, buf)
	n := counts["s1:sig"]
	if n != trigCapturePts {
		t.Fatalf("captured %d points, want the %d-point cap", n, trigCapturePts)
	}
}

// Short captures must stay full resolution — decimation only kicks in above
// the cap.
func TestBuildTriggerCaptureKeepsSmallWindowsIntact(t *testing.T) {
	h := NewHub()
	rb := newSigRing(10000)
	fillRing(rb, 0, 1000, 10000) // 10 s at 1 kHz
	h.rings["s1:sig"] = rb

	buf := h.buildTriggerCapture(1.0, 0.5, 0.5)
	if buf == nil {
		t.Fatal("no capture frame built")
	}
	counts := decodeCapture(t, buf)
	if n := counts["s1:sig"]; n < 990 || n > 1010 {
		t.Fatalf("captured %d points, want ~1000 undecimated", n)
	}
}