cmd/app: high-level app configuration syntax

This replaces the nixos module.

Signed-off-by: Ophestra <cat@gensokyo.uk>

4 files changed, 424 insertions, 0 deletions

diff --git a/cmd/app/app.go b/cmd/app/app.go
new file mode 100644
index 00000000..74ff9ad4
--- /dev/null
+++ b/cmd/app/app.go
@@ -0,0 +1,262 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+
+	"hakurei.app/check"
+	"hakurei.app/fhs"
+	"hakurei.app/hst"
+)
+
+// parsePair parses a NUL-delimited quoted paths pair.
+func parsePair(s string) (source, target *check.Absolute, err error) {
+	var p string
+	if p, err = strconv.Unquote(s); err != nil {
+		return
+	}
+	_source, _target, ok := strings.Cut(p, "\x00")
+	if source, err = check.NewAbs(_source); err != nil {
+		return
+	}
+	if !ok {
+		return
+	}
+	target, err = check.NewAbs(_target)
+	return
+}
+
+// parse decodes a high-level configuration stream and returns its
+// corresponding [hst.Config].
+func parse(id string, base *check.Absolute, r io.Reader) (*hst.Config, error) {
+	shell := fhs.AbsRoot.Append("bin", "zsh")
+	home := hst.AbsPrivateTmp.Append("home")
+
+	c := hst.Config{
+		ID:          id,
+		Enablements: new(hst.Enablements),
+
+		SessionBus: &hst.BusConfig{
+			Own: []string{
+				id + ".*",
+				"org.mpris.MediaPlayer2." + id + ".*",
+			},
+			Filter: true,
+		},
+		SystemBus: &hst.BusConfig{Filter: true},
+
+		Container: &hst.ContainerConfig{
+			Env: make(map[string]string),
+			Filesystem: []hst.FilesystemConfigJSON{
+				{FilesystemConfig: &hst.FSOverlay{
+					Target: fhs.AbsRoot,
+					Lower: []*check.Absolute{
+						base.Append("template", "initial"),
+						base.Append("template", "upper"),
+					},
+				}},
+				{FilesystemConfig: &hst.FSBind{
+					Target: home,
+					Source: base.Append("state", id),
+					Write:  true,
+					Ensure: true,
+				}},
+
+				{FilesystemConfig: &hst.FSEphemeral{
+					Target: fhs.AbsVar.Append("tmp"),
+					Write:  true,
+					Perm:   01777,
+				}},
+
+				{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("block")}},
+				{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("bus")}},
+				{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("class")}},
+				{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("dev")}},
+				{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("devices")}},
+			},
+
+			Username: "chronos",
+			Shell:    shell,
+			Home:     home,
+			Path:     shell,
+			Args:     []string{"zsh", "-c"},
+		},
+	}
+
+	s := bufio.NewScanner(r)
+	scanOnce := func() error {
+		if s.Scan() {
+			return nil
+		}
+		if err := s.Err(); err != nil {
+			return err
+		}
+		return io.ErrUnexpectedEOF
+	}
+
+	if err := scanOnce(); err != nil {
+		return nil, err
+	}
+	if v, err := strconv.Atoi(s.Text()); err != nil {
+		return nil, err
+	} else {
+		c.Identity = v
+	}
+
+	if err := scanOnce(); err != nil {
+		return nil, err
+	}
+	c.Container.Args = append(c.Container.Args, s.Text())
+
+	var flagGPU, flagSystemBus bool
+	flags := map[string]*bool{
+		"gpu":        &flagGPU,
+		"system_bus": &flagSystemBus,
+	}
+
+	for s.Scan() {
+		key, value, ok := strings.Cut(s.Text(), " ")
+		if key != "" && key[0] == ';' {
+			continue
+		}
+
+		if !ok {
+			if key == "" {
+				continue
+			}
+
+			var p *bool
+			if p, ok = flags[key]; ok {
+				*p = true
+				continue
+			}
+
+			switch key {
+			case "wayland":
+				*c.Enablements |= hst.EWayland
+			case "x11":
+				*c.Enablements |= hst.EX11
+			case "dbus":
+				*c.Enablements |= hst.EDBus
+			case "pipewire":
+				*c.Enablements |= hst.EPipeWire
+
+			case "multiarch":
+				c.Container.Flags |= hst.FMultiarch
+			case "devel":
+				c.Container.Flags |= hst.FDevel
+			case "userns":
+				c.Container.Flags |= hst.FUserns
+			case "net":
+				c.Container.Flags |= hst.FHostNet
+			case "abstract":
+				c.Container.Flags |= hst.FHostAbstract
+			case "tty":
+				c.Container.Flags |= hst.FTty
+			case "mapuid":
+				c.Container.Flags |= hst.FMapRealUID
+			case "device":
+				c.Container.Flags |= hst.FDevice
+
+			case "share_runtime":
+				c.Container.Flags |= hst.FShareRuntime
+			case "share_tmpdir":
+				c.Container.Flags |= hst.FShareTmpdir
+
+			default:
+				return nil, fmt.Errorf("invalid flag %q", key)
+			}
+
+			continue
+		}
+
+		switch key {
+		case "group":
+			c.Groups = append(c.Groups, value)
+			continue
+
+		case "env":
+			if key, value, ok = strings.Cut(value, "="); !ok {
+				return nil, fmt.Errorf("invalid environment %q", key)
+			}
+			c.Container.Env[key] = value
+			continue
+
+		case "ro":
+			source, target, err := parsePair(value)
+			if err != nil {
+				return nil, err
+			}
+			c.Container.Filesystem = append(c.Container.Filesystem,
+				hst.FilesystemConfigJSON{FilesystemConfig: &hst.FSBind{
+					Target: target,
+					Source: source,
+				}},
+			)
+			continue
+
+		case "rw":
+			source, target, err := parsePair(value)
+			if err != nil {
+				return nil, err
+			}
+			c.Container.Filesystem = append(c.Container.Filesystem,
+				hst.FilesystemConfigJSON{FilesystemConfig: &hst.FSBind{
+					Target: target,
+					Source: source,
+					Write:  true,
+				}},
+			)
+			continue
+
+		case "own":
+			c.SessionBus.Own = append(c.SessionBus.Own, value)
+			continue
+		case "own_system":
+			c.SystemBus.Own = append(c.SystemBus.Own, value)
+			continue
+
+		case "talk":
+			c.SessionBus.Talk = append(c.SessionBus.Talk, value)
+			continue
+		case "talk_system":
+			c.SystemBus.Talk = append(c.SystemBus.Talk, value)
+			continue
+
+		default:
+			return nil, fmt.Errorf("invalid key %q", key)
+		}
+	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+
+	if flagGPU {
+		c.Container.Filesystem = append(c.Container.Filesystem, []hst.FilesystemConfigJSON{
+			{FilesystemConfig: &hst.FSBind{
+				Source:   fhs.AbsDev.Append("dri"),
+				Device:   true,
+				Optional: true,
+			}},
+		}...)
+	}
+
+	if !flagSystemBus {
+		c.SystemBus = nil
+	}
+
+	if c.Container.Flags&hst.FShareTmpdir == 0 {
+		c.Container.Filesystem = append(c.Container.Filesystem,
+			hst.FilesystemConfigJSON{FilesystemConfig: &hst.FSEphemeral{
+				Target: fhs.AbsTmp,
+				Write:  true,
+				Perm:   01777,
+			}},
+		)
+	}
+
+	return &c, nil
+}
diff --git a/cmd/app/app_test.go b/cmd/app/app_test.go
new file mode 100644
index 00000000..df17f781
--- /dev/null
+++ b/cmd/app/app_test.go
@@ -0,0 +1,152 @@
+package main
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+
+	"hakurei.app/check"
+	"hakurei.app/fhs"
+	"hakurei.app/hst"
+)
+
+func TestParse(t *testing.T) {
+	t.Parallel()
+
+	base := fhs.AbsProc.Append("nonexistent")
+	testCases := []struct {
+		name string
+		data string
+		want *hst.Config
+		err  error
+	}{
+		{"com.discordapp.Discord", `8
+exec Discord --ozone-platform-hint=wayland
+
+gpu
+wayland
+dbus
+system_bus
+pipewire
+userns
+net
+mapuid
+
+share_runtime
+share_tmpdir
+
+group media_rw
+env ELECTRON_TRASH=gio
+rw "/sdcard"
+; remove before reusing
+ro "/bin\x00/.hakurei/bin"
+
+talk org.kde.StatusNotifierWatcher
+talk com.canonical.AppMenu.Registrar
+talk com.canonical.indicator.application
+talk com.canonical.Unity
+`, &hst.Config{
+			Identity:    8,
+			ID:          "com.discordapp.Discord",
+			Enablements: new(hst.EWayland | hst.EDBus | hst.EPipeWire),
+			Groups:      []string{"media_rw"},
+
+			SessionBus: &hst.BusConfig{
+				Talk: []string{
+					"org.kde.StatusNotifierWatcher",
+					"com.canonical.AppMenu.Registrar",
+					"com.canonical.indicator.application",
+					"com.canonical.Unity",
+				},
+				Own: []string{
+					"com.discordapp.Discord.*",
+					"org.mpris.MediaPlayer2.com.discordapp.Discord.*",
+				},
+				Filter: true,
+			},
+			SystemBus: &hst.BusConfig{Filter: true},
+
+			Container: &hst.ContainerConfig{
+				Env: map[string]string{
+					"ELECTRON_TRASH": "gio",
+				},
+				Filesystem: []hst.FilesystemConfigJSON{
+					{FilesystemConfig: &hst.FSOverlay{
+						Target: fhs.AbsRoot,
+						Lower: []*check.Absolute{
+							base.Append("template", "initial"),
+							base.Append("template", "upper"),
+						},
+					}},
+					{FilesystemConfig: &hst.FSBind{
+						Target: hst.AbsPrivateTmp.Append("home"),
+						Source: base.Append("state", "com.discordapp.Discord"),
+						Write:  true,
+						Ensure: true,
+					}},
+
+					{FilesystemConfig: &hst.FSEphemeral{
+						Target: fhs.AbsVar.Append("tmp"),
+						Write:  true,
+						Perm:   01777,
+					}},
+
+					{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("block")}},
+					{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("bus")}},
+					{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("class")}},
+					{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("dev")}},
+					{FilesystemConfig: &hst.FSBind{Source: fhs.AbsSys.Append("devices")}},
+
+					{FilesystemConfig: &hst.FSBind{
+						Source: check.MustAbs("/sdcard"),
+						Write:  true,
+					}},
+					{FilesystemConfig: &hst.FSBind{
+						Target: check.MustAbs("/.hakurei/bin"),
+						Source: check.MustAbs("/bin"),
+					}},
+
+					{FilesystemConfig: &hst.FSBind{
+						Source:   fhs.AbsDev.Append("dri"),
+						Device:   true,
+						Optional: true,
+					}},
+				},
+
+				Username: "chronos",
+				Shell:    fhs.AbsRoot.Append("bin", "zsh"),
+				Home:     hst.AbsPrivateTmp.Append("home"),
+				Path:     fhs.AbsRoot.Append("bin", "zsh"),
+				Args: []string{
+					"zsh", "-c",
+					"exec Discord --ozone-platform-hint=wayland",
+				},
+
+				Flags: hst.FUserns | hst.FHostNet | hst.FMapRealUID |
+					hst.FShareRuntime | hst.FShareTmpdir,
+			},
+		}, nil},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			got, err := parse(
+				tc.name,
+				base,
+				strings.NewReader(tc.data),
+			)
+
+			if !reflect.DeepEqual(err, tc.err) {
+				t.Errorf("parse: error = %v, want %v", err, tc.err)
+			}
+			if err != nil {
+				return
+			}
+
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("parse: %#v, want %#v", got, tc.want)
+			}
+		})
+	}
+}
diff --git a/hst/container.go b/hst/container.go
index 15a5d221..f985f393 100644
--- a/hst/container.go
+++ b/hst/container.go
@@ -2,6 +2,7 @@ package hst
 
 import (
 	"encoding/json"
+	"fmt"
 	"strings"
 	"syscall"
 	"time"
@@ -161,6 +162,10 @@ type ContainerConfig struct {
 	Flags Flags `json:"-"`
 }
 
+func (c *ContainerConfig) GoString() string {
+	return fmt.Sprintf("&%#v", *c)
+}
+
 // ContainerConfigF is [ContainerConfig] stripped of its methods.
 //
 // The [ContainerConfig.Flags] field does not survive a [json] round trip.
diff --git a/hst/dbus.go b/hst/dbus.go
index 5c4620cc..7b8a3585 100644
--- a/hst/dbus.go
+++ b/hst/dbus.go
@@ -1,6 +1,7 @@
 package hst
 
 import (
+	"fmt"
 	"strconv"
 	"strings"
 )
@@ -61,6 +62,10 @@ type BusConfig struct {
 	Filter bool `json:"filter"`
 }
 
+func (c *BusConfig) GoString() string {
+	return fmt.Sprintf("&%#v", *c)
+}
+
 // Interfaces iterates over all interface strings specified in [BusConfig].
 func (c *BusConfig) Interfaces(yield func(string) bool) {
 	if c == nil {