package web

import (
	"context"
	"errors"
	"strings"
	"testing"
	"time"

	"gitea.mynodes.xyz/ilker/llmgw/internal/promq"
)

func ts(name string, vals ...float64) promq.Series {
	s := promq.Series{Name: name}
	base := time.Unix(1700000000, 0)
	for i, v := range vals {
		s.Points = append(s.Points, promq.Point{At: base.Add(time.Duration(i) * time.Minute), Value: v})
	}
	return s
}

func TestEveryLineGetsItsOwnColourAndALegend(t *testing.T) {
	c := LineChart([]promq.Series{ts("a", 1, 2), ts("b", 2, 1), ts("c", 3, 3)}, "", 4)

	if len(c.Legend) != 3 {
		t.Fatalf("expected a legend entry per line, got %+v", c.Legend)
	}
	seen := map[string]bool{}
	for _, e := range c.Legend {
		if seen[e.Colour] {
			// Two lines in one colour is two lines nobody can tell apart.
			t.Errorf("colour %s used twice", e.Colour)
		}
		seen[e.Colour] = true
	}
}

func TestATailIsFoldedRatherThanGivenNewColours(t *testing.T) {
	in := []promq.Series{
		ts("big", 10, 10), ts("m2", 5, 5), ts("m3", 4, 4),
		ts("m4", 1, 1), ts("m5", 2, 2), ts("m6", 3, 3),
	}
	c := LineChart(in, "", 4)

	// The palette has four colours and a fifth line does not get a generated
	// hue. The tail is summed so the chart still adds up.
	if len(c.Legend) != 4 {
		t.Fatalf("expected four lines, got %d: %+v", len(c.Legend), c.Legend)
	}
	last := c.Legend[3]
	if last.Name != "other" {
		t.Errorf("the tail should be named, got %q", last.Name)
	}
	// m4+m5+m6 at the same instant is 6, not any one of them.
	if last.Last != "6" {
		t.Errorf("the tail should be summed, got %q", last.Last)
	}
}

func TestTheTailIsSummedByTimestampNotByPosition(t *testing.T) {
	// Two tail series sampled at different times. Added by index their points
	// would slide sideways onto each other's clock.
	a := promq.Series{Name: "a", Points: []promq.Point{{At: time.Unix(100, 0), Value: 1}}}
	b := promq.Series{Name: "b", Points: []promq.Point{{At: time.Unix(200, 0), Value: 2}}}
	big := ts("big", 9, 9, 9)

	c := LineChart([]promq.Series{big, ts("x", 8, 8), ts("y", 7, 7), a, b}, "", 4)
	if c.Legend[3].Name != "other" || c.Legend[3].Last != "2" {
		t.Errorf("expected the latest tail point alone, got %+v", c.Legend[3])
	}
}

func TestAFlatZeroIsDrawnRatherThanLeftBlank(t *testing.T) {
	c := LineChart([]promq.Series{ts("idle", 0, 0, 0)}, "", 4)

	// Nothing happening is a real answer, and a line along the bottom says so
	// where an empty frame reads as a broken chart.
	if c.Empty {
		t.Fatal("a quiet series is not an absent one")
	}
	if !strings.Contains(string(c.SVG), "polyline") {
		t.Error("the line should be drawn")
	}
}

func TestNothingToDrawSaysSoInsteadOfDrawingAFrame(t *testing.T) {
	if got := LineChart(nil, "", 4); !got.Empty {
		t.Error("no series is empty")
	}
	// One instant is not a line: drawn, it is a dot in the corner.
	one := promq.Series{Name: "a", Points: []promq.Point{{At: time.Unix(1, 0), Value: 5}}}
	if got := LineChart([]promq.Series{one}, "", 4); !got.Empty {
		t.Error("a single sample is not a line")
	}
}

func TestTheAxisTopsOutAtANumberAPersonWouldChoose(t *testing.T) {
	c := LineChart([]promq.Series{ts("a", 0.1, 0.8347)}, "", 4)
	// 0.8347 as the top makes every gridline unreadable, and the shape of the
	// data is what the chart is for.
	if c.Peak != "1" {
		t.Errorf("expected a rounded ceiling, got %q", c.Peak)
	}
}

func TestPercentagesAndSecondsReadAsThemselves(t *testing.T) {
	if got := formatValue(0.42, "%"); got != "42%" {
		t.Errorf("percent: %q", got)
	}
	if got := formatValue(0.035, "s"); got != "35ms" {
		t.Errorf("sub-second latency should read in ms, got %q", got)
	}
	if got := formatValue(12.5, "s"); got != "12.5s" {
		t.Errorf("seconds: %q", got)
	}
}

func TestAValueAboveTheCeilingIsClampedNotDrawnOffTheChart(t *testing.T) {
	// Only reachable if a series changes between the bounds pass and drawing,
	// but an SVG point outside the viewBox is a line that leaves the frame.
	if got := clamp01(1.4); got != 1 {
		t.Errorf("expected clamping, got %v", got)
	}
	if got := clamp01(-2); got != 0 {
		t.Errorf("expected clamping, got %v", got)
	}
}

// fakeHistory stands in for a metrics store.
type fakeHistory struct {
	byExpr map[string][]promq.Series
	err    error
	asked  []string
}

func (f *fakeHistory) RangeQuery(_ context.Context, expr, _ string,
	_, _ time.Duration,
) ([]promq.Series, error) {
	f.asked = append(f.asked, expr)
	return f.byExpr[expr], f.err
}

func TestTheFleetPanelsAreEachQueried(t *testing.T) {
	h := &fakeHistory{byExpr: map[string][]promq.Series{
		"llmgw_pool_saturation":         {ts("qwen", 0.1, 0.4)},
		"llmgw_endpoint_waiting":        {ts("r1", 0, 2)},
		"llmgw_endpoint_kv_cache_usage": {ts("r1", 0.1, 0.2)},
		"llmgw_model_replicas_ready":    {ts("qwen", 3, 3)},
	}}
	got := LoadFleetCharts(context.Background(), h, time.Hour, nil)

	if len(h.asked) != 4 {
		t.Fatalf("expected one query per panel, got %v", h.asked)
	}
	for name, c := range map[string]TimeSeries{
		"saturation": got.Saturation, "queue": got.Queue,
		"kv": got.KV, "ready": got.Ready,
	} {
		if c.Empty {
			t.Errorf("%s came back empty", name)
		}
	}
}

func TestOneFailedQueryFailsThemAll(t *testing.T) {
	h := &fakeHistory{err: errors.New("reaching Prometheus: refused")}
	got := LoadFleetCharts(context.Background(), h, time.Hour, nil)

	// Three charts drawn and one blank invites reading the blank one as
	// "nothing is happening there". Either the store answered or it did not.
	if got.Err == "" {
		t.Fatal("the failure should be reported")
	}
	if !strings.Contains(got.Err, "refused") {
		t.Errorf("the reason should survive: %q", got.Err)
	}
}

func TestWithNoMetricsStoreThereAreNoPanels(t *testing.T) {
	// A deployment with no Prometheus leaves them off rather than showing
	// empty frames where charts should be.
	if got := LoadFleetCharts(context.Background(), nil, time.Hour, nil); got != nil {
		t.Errorf("expected nothing, got %+v", got)
	}
}

func TestAUsageLegendGivesTotalsNotTheLastSlice(t *testing.T) {
	// A counter's latest slice is usually quiet; "0" beside a line that
	// carried hundreds read as a broken chart.
	c := LineChartTotals([]promq.Series{ts("ml", 5, 7, 0), ts("vision", 1, 2, 0)}, "", 4)
	got := map[string]string{}
	for _, l := range c.Legend {
		got[l.Name] = l.Last
	}
	if got["ml"] != "12" || got["vision"] != "3" {
		t.Errorf("legend = %v, expected the totals", got)
	}
}

func TestChartAxesReadAsSizesAndSmallPercents(t *testing.T) {
	// compact's suffixes are for counts: on bytes they read as "20.0BB".
	if got := formatValue(20e9, "bytes"); got != "18.6GiB" {
		t.Errorf("20e9 bytes = %q", got)
	}
	// A quiet machine is not 0%, 0%, 0% up its axis.
	if got := formatValue(0.005, "%"); got != "0.5%" {
		t.Errorf("0.005 = %q", got)
	}
	if got := formatValue(0.62, "%"); got != "62%" {
		t.Errorf("0.62 = %q", got)
	}
	if got := windowWord(time.Hour); got != "hour" {
		t.Errorf("an hour reads %q", got)
	}
}