package buildstep

import (
	"context"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"testing"

	"git.novox.be/novox/mesh-sdk/go/forgekey"
)

// pairs says whether argv holds the words of want one after another.
func holds(argv []string, want ...string) bool {
	for i := 0; i+len(want) <= len(argv); i++ {
		match := true
		for j, w := range want {
			if argv[i+j] != w {
				match = false
				break
			}
		}
		if match {
			return true
		}
	}
	return false
}

func fixedSystem(t *testing.T) {
	t.Helper()
	before := systemArgs
	systemArgs = func() []string { return []string{"--ro-bind", "/usr", "/usr", "--symlink", "usr/bin", "/bin"} }
	t.Cleanup(func() { systemArgs = before })
}

// A run step's command runs in bubblewrap (novox/hq ADR 0448; issue 1309): no network, no namespace shared, an
// environment of exactly what the step is given, the workspace the one tree it writes, the toolchain read-only, and
// nothing else of the machine's: not the account's home, not the forge key or a bus login, not the runtime directory,
// and no name service.
func TestARunStepRunsShutOffInBubblewrap(t *testing.T) {
	fixedSystem(t)
	iso := Isolation{Workspace: "/work/ab12/tree", ReadOnly: []string{"/usr/lib/go"}, Writable: []string{"/work/ab12/out"},
		Env: []string{"GOFLAGS=-mod=mod", "PATH=/usr/bin"}, Hosts: "/work/ab12/hosts"}
	argv, err := iso.Command("go", "test", "./...")
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range [][]string{
		{"--unshare-all"}, {"--die-with-parent"}, {"--new-session"}, {"--clearenv"},
		{"--proc", "/proc"}, {"--dev", "/dev"}, {"--tmpfs", "/tmp"},
		{"--ro-bind", "/usr", "/usr"}, {"--symlink", "usr/bin", "/bin"},
		{"--ro-bind", "/usr/lib/go", "/usr/lib/go"},
		{"--bind", "/work/ab12/tree", "/work/ab12/tree"}, {"--bind", "/work/ab12/out", "/work/ab12/out"},
		{"--ro-bind", "/work/ab12/hosts", "/etc/hosts"},
		{"--setenv", "GOFLAGS", "-mod=mod"}, {"--setenv", "PATH", "/usr/bin"}, {"--setenv", "HOME", "/tmp/home"},
		{"--chdir", "/work/ab12/tree"},
		{"--", "go", "test", "./..."},
	} {
		if !holds(argv, want...) {
			t.Errorf("the command has no %v: %v", want, argv)
		}
	}
	if holds(argv, "--share-net") || strings.Contains(strings.Join(argv, " "), "resolv.conf") || strings.Contains(strings.Join(argv, " "), "/run") {
		t.Errorf("the command reaches the network, the name service or the runtime directory: %v", argv)
	}
	// The workspace is mounted after /tmp's tmpfs, so a workspace under /tmp is not hidden by it.
	if strings.Index(strings.Join(argv, "\x00"), "--tmpfs\x00/tmp") > strings.Index(strings.Join(argv, "\x00"), "--bind\x00/work/ab12/tree") {
		t.Errorf("the tmpfs of /tmp comes after the workspace: %v", argv)
	}
	// A HOME the step is given is its own.
	iso.Env = append(iso.Env, "HOME=/work/ab12/home")
	argv, _ = iso.Command("true")
	if holds(argv, "--setenv", "HOME", "/tmp/home") || !holds(argv, "--setenv", "HOME", "/work/ab12/home") {
		t.Errorf("the step's own HOME was replaced: %v", argv)
	}
}

func TestAnIsolationNamesNoPathItCannotPin(t *testing.T) {
	for _, iso := range []Isolation{
		{Workspace: ""},
		{Workspace: "tree"},
		{Workspace: "/"},
		{Workspace: "/w", ReadOnly: []string{"relative"}},
		{Workspace: "/w", Writable: []string{"/"}},
		{Workspace: "/w", Caches: []string{"/a/../b"}},
		{Workspace: "/w", Env: []string{"NOEQUALS"}},
	} {
		if _, err := iso.Command("true"); err == nil {
			t.Errorf("%+v was accepted", iso)
		}
	}
}

// Isolated runs every command through bwrap, with the step's environment inside and a hosts file that names only the
// loopback, removed after.
func TestIsolatedRunsEachCommandThroughBubblewrap(t *testing.T) {
	fixedSystem(t)
	var ran []string
	var hosts string
	inner := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
		ran = append([]string{name}, args...)
		for i, a := range args {
			if a == "/etc/hosts" && i > 0 {
				hosts = args[i-1]
			}
		}
		return forgekey.Ran{Stdout: "ok"}
	}
	r := Isolated(inner, Isolation{Workspace: "/w"})(context.Background(), []string{"A=1"}, "go", "build")
	if r.Stdout != "ok" || ran[0] != Bubblewrap || !holds(ran, "--setenv", "A", "1") || !holds(ran, "--", "go", "build") {
		t.Fatalf("ran %v: %+v", ran, r)
	}
	if hosts == "" {
		t.Fatalf("no hosts file was bound: %v", ran)
	}

	// 1921/S2: with a cache layer, what one command wrote into the caches is kept for the ask's later commands, the
	// shared cache stays unchanged, two commands at once write into layers of their own (overlayfs refuses an upper
	// layer two mounts share), and a command's own layer is gone when it ends.
	root := t.TempDir()
	shared := filepath.Join(root, "gobuild")
	if err := os.MkdirAll(shared, 0o700); err != nil {
		t.Fatal(err)
	}
	layer := filepath.Join(root, "ws", "cachelayer")
	var mu sync.Mutex
	uppers := map[string]bool{}
	gate := make(chan struct{})
	var started sync.WaitGroup
	started.Add(2)
	writer := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
		up := overlayOf(args, shared)
		mu.Lock()
		uppers[up] = true
		mu.Unlock()
		started.Done()
		<-gate // both commands are running before either ends
		os.MkdirAll(filepath.Join(up, "ab"), 0o700)
		os.WriteFile(filepath.Join(up, "ab", args[len(args)-1]+"-d"), []byte("compiled"), 0o600)
		return forgekey.Ran{}
	}
	run := Isolated(writer, Isolation{Workspace: filepath.Join(root, "ws"), Caches: []string{shared}, CacheLayer: layer})
	var wg sync.WaitGroup
	for _, pkg := range []string{"one", "two"} {
		wg.Add(1)
		go func() { defer wg.Done(); run(context.Background(), nil, "go", "build", pkg) }()
	}
	started.Wait()
	close(gate)
	wg.Wait()
	if len(uppers) != 2 {
		t.Fatalf("two commands at once wrote into %d layers, want 2 of their own: %v", len(uppers), uppers)
	}
	for _, pkg := range []string{"one", "two"} {
		if b, err := os.ReadFile(filepath.Join(keptLayer(layer, 0), "ab", pkg+"-d")); err != nil || string(b) != "compiled" {
			t.Errorf("what the build of %s compiled is not kept for the ask: %q %v", pkg, b, err)
		}
	}
	for up := range uppers {
		if _, err := os.Stat(up); !os.IsNotExist(err) {
			t.Errorf("the command's own layer %s outlived it: %v", up, err)
		}
	}
	if entries, _ := os.ReadDir(shared); len(entries) != 0 {
		t.Errorf("the shared cache was written: %v", entries)
	}
}