package config

import (
	"math"
	"testing"

	"gopkg.in/yaml.v3"
)

func TestParseSizeUnits(t *testing.T) {
	cases := []struct {
		in   string
		want int64
	}{
		{"0", 0},
		{"512", 512},
		{"512B", 512},
		{"1K", 1 << 10},
		{"1KB", 1000}, // decimal, unlike KiB
		{"1KiB", 1 << 10},
		{"1M", 1 << 20},
		{"1MiB", 1 << 20},
		{"1G", 1 << 30},
		{"1GiB", 1 << 30},
		{"1T", 1 << 40},
		{"1TiB", 1 << 40},
		// "M" must not eat the "iB" of "MiB", and "B" must not eat the "iB"
		// of "BiB"-looking input. These are the shadowing cases the longest
		// suffix first ordering exists for.
		{"1MiB", 1 << 20},
		{"1MIB", 1 << 20},
		{"512mib", 1 << 20 * 512},
		{"  2 MiB  ", 2 << 20},
		// Fractions scale exactly for binary units.
		{"1.5GiB", 1610612736},
		{"0.5KiB", 512},
	}
	for _, tc := range cases {
		got, err := ParseSize(tc.in)
		if err != nil {
			t.Errorf("ParseSize(%q): unexpected error %v", tc.in, err)
			continue
		}
		if int64(got) != tc.want {
			t.Errorf("ParseSize(%q) = %d, want %d", tc.in, int64(got), tc.want)
		}
	}
}

func TestParseSizeRejectsJunk(t *testing.T) {
	// Every one of these must be an error rather than a plausible number:
	// a silently misread memory budget is worse than a refusal to start.
	for _, in := range []string{
		"",
		"   ",
		"MiB",
		"abc",
		"512MiBx", // trailing junk, not a truncated match
		"1.2.3",
		"12 34",
		"-1",
		"-1MiB",
		"1MiB-", // negative after the unit
		"KiB",   // a unit with no number in front
		".",     // a number with no digits
	} {
		if got, err := ParseSize(in); err == nil {
			t.Errorf("ParseSize(%q) = %d, want an error", in, int64(got))
		}
	}
}

func TestParseSizeRangeAndRounding(t *testing.T) {
	// A value that does not fit in an int64 is an error, not a wrap.
	for _, in := range []string{"8EiB", "9223372036854775807B", "99999999999999999999"} {
		if got, err := ParseSize(in); err == nil {
			t.Errorf("ParseSize(%q) = %d, want an out-of-range error", in, int64(got))
		}
	}
	// The largest representable value still parses.
	if got, err := ParseSize("8EiB"); err == nil && int64(got) <= 0 {
		t.Errorf("ParseSize(%q) = %d, want a positive value or an error", "8EiB", int64(got))
	}
	// A fractional value truncates rather than rounding up: a memory budget
	// that rounds up is a budget the process does not have.
	if got, err := ParseSize("0.1KiB"); err != nil || int64(got) != 102 {
		t.Errorf("ParseSize(%q) = %d (err %v), want 102", "0.1KiB", int64(got), err)
	}
}

// TestParseSizeAcceptsExponents pins that ParseFloat's exponent syntax is
// accepted, with or without a unit: the parser is one ParseFloat call in both
// paths, and making "1e3" work while "1e3MiB" errors would be a surprise.
func TestParseSizeAcceptsExponents(t *testing.T) {
	if got, err := ParseSize("1e3MiB"); err != nil || int64(got) != 1000*(1<<20) {
		t.Errorf("ParseSize(%q) = %d (err %v), want %d", "1e3MiB", int64(got), err, 1000*(1<<20))
	}
}

func TestSizeUnmarshalYAML(t *testing.T) {
	type doc struct {
		V Size `yaml:"v"`
	}
	cases := []struct {
		in   string
		want int64
	}{
		{"v: 512MiB\n", 512 << 20},
		{"v: \"512MiB\"\n", 512 << 20},
		// A bare integer is bytes: that is what MarshalYAML writes, so a
		// config the API rewrote must load back unchanged.
		{"v: 1073741824\n", 1 << 30},
		{"v: 0\n", 0},
	}
	for _, tc := range cases {
		var d doc
		if err := yaml.Unmarshal([]byte(tc.in), &d); err != nil {
			t.Errorf("unmarshal %q: %v", tc.in, err)
			continue
		}
		if int64(d.V) != tc.want {
			t.Errorf("unmarshal %q = %d, want %d", tc.in, int64(d.V), tc.want)
		}
	}

	var d doc
	if err := yaml.Unmarshal([]byte("v: not-a-size\n"), &d); err == nil {
		t.Error("unmarshal of junk: want an error")
	}
	// "1Gi" is the k8s spelling and is *not* in the unit table: the parser is
	// deliberately strict, so a memory budget must be written 1GiB. Kept as
	// a test rather than left implicit, because the k8s manifests sit right
	// next to this code and "1Gi" is what an operator reaches for first.
	if err := yaml.Unmarshal([]byte("v: 1Gi\n"), &d); err == nil {
		t.Error(`unmarshal of "1Gi": want an error, the unit is GiB`)
	}
}

func TestSizeMarshalYAMLRoundTrips(t *testing.T) {
	type doc struct {
		V Size `yaml:"v"`
	}
	in := doc{V: Size(1536 << 20)}
	b, err := yaml.Marshal(in)
	if err != nil {
		t.Fatal(err)
	}
	var out doc
	if err := yaml.Unmarshal(b, &out); err != nil {
		t.Fatalf("round trip: %v", err)
	}
	if out.V != in.V {
		t.Fatalf("round trip = %d, want %d", int64(out.V), int64(in.V))
	}
}

func TestSizeString(t *testing.T) {
	cases := []struct {
		in   Size
		want string
	}{
		{0, "0"},
		{512, "512B"},
		{1 << 10, "1KiB"},
		{1536, "1536B"}, // not a whole KiB, so bytes
		{1 << 20, "1MiB"},
		{1 << 30, "1GiB"},
		{3<<30 + 7, "3221225479B"}, // 3Gi + 7: no whole unit left, so bytes
	}
	for _, tc := range cases {
		if got := tc.in.String(); got != tc.want {
			t.Errorf("Size(%d).String() = %q, want %q", int64(tc.in), got, tc.want)
		}
	}
}

func TestMemoryEffectiveLimit(t *testing.T) {
	if got := (Memory{}).EffectiveLimit(); got != math.MaxInt64 {
		t.Errorf("no limit: got %d, want MaxInt64 (no ceiling)", got)
	}
	// A limit below the reserve still leaves the runtime its floor rather
	// than a death spiral.
	if got := (Memory{Limit: 128 << 20}).EffectiveLimit(); got != 64<<20 {
		t.Errorf("limit below the reserve: got %d, want the 64MiB floor", got)
	}
	if got := (Memory{Limit: 64 << 20}).EffectiveLimit(); got != 64<<20 {
		t.Errorf("limit equal to the floor: got %d, want 64MiB", got)
	}
	// The usual case: 1Gi with the default 256MiB reserve.
	if got := (Memory{Limit: 1 << 30}).EffectiveLimit(); got != (1<<30)-(256<<20) {
		t.Errorf("1Gi limit: got %d, want %d", got, (1<<30)-(256<<20))
	}
	if got := (Memory{Limit: 1 << 30, Reserve: 300 << 20}).EffectiveLimit(); got != (1<<30)-(300<<20) {
		t.Errorf("explicit reserve: got %d, want %d", got, (1<<30)-(300<<20))
	}
}

func TestMemoryEffectiveCacheBytes(t *testing.T) {
	// An explicit budget wins outright: the operator said so.
	if got := (Memory{Limit: 1 << 30, CacheMaxBytes: 100 << 20}).EffectiveCacheBytes(); got != 100<<20 {
		t.Errorf("explicit cache budget: got %d, want %d", got, 100<<20)
	}
	// Otherwise it is 60% of the effective limit, leaving the rest for the
	// GC, the live query ring and the per-query working set.
	m := Memory{Limit: 1 << 30, Reserve: 256 << 20}
	want := m.EffectiveLimit() * 3 / 5
	if got := m.EffectiveCacheBytes(); got != want {
		t.Errorf("derived cache budget: got %d, want %d", got, want)
	}
	// No memory limit at all means no byte budget either, not a made-up one.
	if got := (Memory{}).EffectiveCacheBytes(); got != 0 {
		t.Errorf("no limit: got %d, want 0 (unbounded)", got)
	}
}