package buildcpu

import (
	"os"
	"path/filepath"
	"reflect"
	"runtime"
	"testing"
)

// The node's share as a quota, the threads one step is given across every build slot of the node, and the words the
// composer hands, in one table (ADR 0553, issue 1806).
func TestShareQuotaAndThreads(t *testing.T) {
	for _, c := range []struct {
		name                  string
		percent, cores, slots int
		quota, threads        int
	}{
		{"shanks: half of 24 across 9 slots", 50, 24, 9, 1200, 1},
		{"shanks: half of 24 across 4 slots", 50, 24, 4, 1200, 3},
		{"ace: three quarters of 24 across 6 slots", 75, 24, 6, 1800, 3},
		{"g14: half of 16 across 1 slot", 50, 16, 1, 800, 8},
		{"one processor at least", 10, 2, 4, 100, 1},
		{"no slots counts as one", 100, 4, 0, 400, 4},
		{"a share out of range is the default", 0, 8, 1, 0, 4},
	} {
		if c.quota != 0 {
			if q := Quota(c.percent, c.cores); q != c.quota {
				t.Errorf("%s: Quota = %d, want %d", c.name, q, c.quota)
			}
		}
		if th := Threads(c.percent, c.cores, c.slots); th != c.threads {
			t.Errorf("%s: Threads = %d, want %d", c.name, th, c.threads)
		}
	}
	words := map[string]string{ShareWord: "75", SlotsWord: "6"}
	l := FromWords(func(k string) string { return words[k] }, 2)
	if l.Percent != 75 || l.From != ShareWord || l.Slots != 6 || l.SlotsFrom != SlotsWord || l.Threads != Threads(75, runtime.NumCPU(), 6) {
		t.Errorf("from the words: %+v", l)
	}
	// Told nothing (or nonsense), a module assumes every build seat beside it at its own capacity, at the default share.
	words = map[string]string{ShareWord: "250", SlotsWord: "many"}
	if l := FromWords(func(k string) string { return words[k] }, 3); l.Percent != DefaultPercent || l.Slots != 3*BuildSeats || l.From != "default" {
		t.Errorf("without usable words: %+v", l)
	}
	if got := Env(0); !reflect.DeepEqual(got, []string{"GOMAXPROCS=1", "UV_THREADPOOL_SIZE=1"}) {
		t.Errorf("Env = %q", got)
	}
}

// What the kernel holds a process to is read from its unit's and its slice's cgroup and its stat file, not assumed.
func TestReadInForce(t *testing.T) {
	dir := t.TempDir()
	cg := filepath.Join(dir, "cg")
	slice := filepath.Join(cg, "meshyield.slice")
	unit := filepath.Join(slice, "mesh-build-go-runtime.service")
	if err := os.MkdirAll(unit, 0o755); err != nil {
		t.Fatal(err)
	}
	for at, files := range map[string]map[string]string{
		slice: {"cpu.idle": "1\n", "cpu.weight": "0\n", "cpu.max": "1200000 100000\n", "io.weight": "default 1\n"},
		unit:  {"cpu.idle": "0\n", "cpu.weight": "100\n", "cpu.max": "max 100000\n", "io.weight": "default 100\n"},
	} {
		for name, v := range files {
			if err := os.WriteFile(filepath.Join(at, name), []byte(v), 0o644); err != nil {
				t.Fatal(err)
			}
		}
	}
	self := filepath.Join(dir, "cgroup")
	stat := filepath.Join(dir, "stat")
	_ = os.WriteFile(self, []byte("0::/meshyield.slice/mesh-build-go-runtime.service\n"), 0o644)
	// A command with a space and a parenthesis in it, then nice 19 in field 19.
	_ = os.WriteFile(stat, []byte("42 (mesh (build) go) S 1 42 42 0 -1 4194560 1 0 0 0 0 0 0 0 39 19 8 0 1 2 3\n"), 0o644)
	cgroupRoot, procSelfCgroup, procSelfStat = cg, self, stat
	t.Cleanup(func() {
		cgroupRoot, procSelfCgroup, procSelfStat = "/sys/fs/cgroup", "/proc/self/cgroup", "/proc/self/stat"
	})

	got := ReadInForce()
	want := InForce{Nice: 19, Cgroup: "/meshyield.slice/mesh-build-go-runtime.service",
		Unit: Group{Path: "/meshyield.slice/mesh-build-go-runtime.service", CPUIdle: "0", CPUWeight: "100",
			CPUMax: "max 100000", IOWeight: "default 100"},
		Slice: Group{Path: "/meshyield.slice", CPUIdle: "1", CPUWeight: "0", CPUMax: "1200000 100000",
			IOWeight: "default 1"},
		Quota: 1200}
	if !reflect.DeepEqual(got, want) {
		t.Fatalf("ReadInForce = %+v\nwant %+v", got, want)
	}
}