feat: add per-provider mutex and Target-aware implementations

- Add snack.Locker embed for per-provider mutex serialization
- Update all providers (pacman, apk, apt, dpkg) to use []Target
  with version pinning support (pkg=version syntax)
- Add lock/unlock to all mutating operations (Install, Remove, Purge,
  Upgrade, Update)
- Add snack.TargetNames helper and formatTargets per provider
- apt: add FromRepo (-t) and Reinstall support
- dpkg: use Target.Source for .deb file paths in Install

apk/apk.go

@@ -8,7 +8,9 @@ import (
 )
 
 // Apk wraps apk-tools operations.
-type Apk struct{}
+type Apk struct {
+	snack.Locker
+}
 
 // New returns a new Apk manager.
 func New() *Apk {
@@ -25,27 +27,37 @@ func (a *Apk) Name() string { return "apk" }
 func (a *Apk) Available() bool { return available() }
 
 // Install one or more packages.
-func (a *Apk) Install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (a *Apk) Install(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	a.Lock()
+	defer a.Unlock()
 	return install(ctx, pkgs, opts...)
 }
 
 // Remove one or more packages.
-func (a *Apk) Remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (a *Apk) Remove(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	a.Lock()
+	defer a.Unlock()
 	return remove(ctx, pkgs, opts...)
 }
 
 // Purge removes packages including config files.
-func (a *Apk) Purge(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (a *Apk) Purge(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	a.Lock()
+	defer a.Unlock()
 	return purge(ctx, pkgs, opts...)
 }
 
 // Upgrade all installed packages.
 func (a *Apk) Upgrade(ctx context.Context, opts ...snack.Option) error {
+	a.Lock()
+	defer a.Unlock()
 	return upgrade(ctx, opts...)
 }
 
 // Update refreshes the package index.
 func (a *Apk) Update(ctx context.Context) error {
+	a.Lock()
+	defer a.Unlock()
 	return update(ctx)
 }
 

apk/apk_linux.go

@@ -52,20 +52,34 @@ func run(ctx context.Context, base []string, opts ...snack.Option) (string, erro
 	return strings.TrimSpace(string(out)), nil
 }
 
-func install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+// formatTargets converts targets to apk CLI arguments.
-	args := append([]string{"add"}, pkgs...)
+// apk uses "pkg=version" for version pinning.
+func formatTargets(targets []snack.Target) []string {
+	args := make([]string, 0, len(targets))
+	for _, t := range targets {
+		if t.Version != "" {
+			args = append(args, t.Name+"="+t.Version)
+		} else {
+			args = append(args, t.Name)
+		}
+	}
+	return args
+}
+
+func install(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	args := append([]string{"add"}, formatTargets(pkgs)...)
 	_, err := run(ctx, args, opts...)
 	return err
 }
 
-func remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func remove(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
-	args := append([]string{"del"}, pkgs...)
+	args := append([]string{"del"}, snack.TargetNames(pkgs)...)
 	_, err := run(ctx, args, opts...)
 	return err
 }
 
-func purge(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func purge(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
-	args := append([]string{"del", "--purge"}, pkgs...)
+	args := append([]string{"del", "--purge"}, snack.TargetNames(pkgs)...)
 	_, err := run(ctx, args, opts...)
 	return err
 }

apk/apk_other.go

@@ -10,15 +10,15 @@ import (
 
 func available() bool { return false }
 
-func install(_ context.Context, _ []string, _ ...snack.Option) error {
+func install(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 
-func remove(_ context.Context, _ []string, _ ...snack.Option) error {
+func remove(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 
-func purge(_ context.Context, _ []string, _ ...snack.Option) error {
+func purge(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 

apt/apt.go

@@ -8,7 +8,9 @@ import (
 )
 
 // Apt implements the snack.Manager interface using apt-get and apt-cache.
-type Apt struct{}
+type Apt struct {
+	snack.Locker
+}
 
 // New returns a new Apt manager.
 func New() *Apt {
@@ -19,27 +21,37 @@ func New() *Apt {
 func (a *Apt) Name() string { return "apt" }
 
 // Install one or more packages.
-func (a *Apt) Install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (a *Apt) Install(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	a.Lock()
+	defer a.Unlock()
 	return install(ctx, pkgs, opts...)
 }
 
 // Remove one or more packages.
-func (a *Apt) Remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (a *Apt) Remove(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	a.Lock()
+	defer a.Unlock()
 	return remove(ctx, pkgs, opts...)
 }
 
 // Purge one or more packages including config files.
-func (a *Apt) Purge(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (a *Apt) Purge(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	a.Lock()
+	defer a.Unlock()
 	return purge(ctx, pkgs, opts...)
 }
 
 // Upgrade all installed packages.
 func (a *Apt) Upgrade(ctx context.Context, opts ...snack.Option) error {
+	a.Lock()
+	defer a.Unlock()
 	return upgrade(ctx, opts...)
 }
 
 // Update refreshes the package index.
 func (a *Apt) Update(ctx context.Context) error {
+	a.Lock()
+	defer a.Unlock()
 	return update(ctx)
 }
 

apt/apt_linux.go

@@ -17,7 +17,21 @@ func available() bool {
 	return err == nil
 }
 
-func buildArgs(command string, pkgs []string, opts ...snack.Option) []string {
+// formatTargets converts targets to apt CLI arguments.
+// apt uses "pkg=version" for version pinning.
+func formatTargets(targets []snack.Target) []string {
+	args := make([]string, 0, len(targets))
+	for _, t := range targets {
+		if t.Version != "" {
+			args = append(args, t.Name+"="+t.Version)
+		} else {
+			args = append(args, t.Name)
+		}
+	}
+	return args
+}
+
+func buildArgs(command string, pkgs []snack.Target, opts ...snack.Option) []string {
 	o := snack.ApplyOptions(opts...)
 	var args []string
 	if o.Sudo {
@@ -30,11 +44,17 @@ func buildArgs(command string, pkgs []string, opts ...snack.Option) []string {
 	if o.DryRun {
 		args = append(args, "--dry-run")
 	}
-	args = append(args, pkgs...)
+	if o.FromRepo != "" {
+		args = append(args, "-t", o.FromRepo)
+	}
+	if o.Reinstall && command == "install" {
+		args = append(args, "--reinstall")
+	}
+	args = append(args, formatTargets(pkgs)...)
 	return args
 }
 
-func runAptGet(ctx context.Context, command string, pkgs []string, opts ...snack.Option) error {
+func runAptGet(ctx context.Context, command string, pkgs []snack.Target, opts ...snack.Option) error {
 	args := buildArgs(command, pkgs, opts...)
 	var cmd *exec.Cmd
 	if args[0] == "sudo" {
@@ -57,15 +77,15 @@ func runAptGet(ctx context.Context, command string, pkgs []string, opts ...snack
 	return nil
 }
 
-func install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func install(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
 	return runAptGet(ctx, "install", pkgs, opts...)
 }
 
-func remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func remove(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
 	return runAptGet(ctx, "remove", pkgs, opts...)
 }
 
-func purge(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func purge(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
 	return runAptGet(ctx, "purge", pkgs, opts...)
 }
 

apt/apt_other.go

@@ -10,15 +10,15 @@ import (
 
 func available() bool { return false }
 
-func install(_ context.Context, _ []string, _ ...snack.Option) error {
+func install(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 
-func remove(_ context.Context, _ []string, _ ...snack.Option) error {
+func remove(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 
-func purge(_ context.Context, _ []string, _ ...snack.Option) error {
+func purge(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 

dpkg/dpkg.go

@@ -8,7 +8,9 @@ import (
 )
 
 // Dpkg implements the snack.Manager interface using dpkg and dpkg-query.
-type Dpkg struct{}
+type Dpkg struct {
+	snack.Locker
+}
 
 // New returns a new Dpkg manager.
 func New() *Dpkg {
@@ -19,17 +21,23 @@ func New() *Dpkg {
 func (d *Dpkg) Name() string { return "dpkg" }
 
 // Install one or more .deb files.
-func (d *Dpkg) Install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (d *Dpkg) Install(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	d.Lock()
+	defer d.Unlock()
 	return install(ctx, pkgs, opts...)
 }
 
 // Remove one or more packages.
-func (d *Dpkg) Remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (d *Dpkg) Remove(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	d.Lock()
+	defer d.Unlock()
 	return remove(ctx, pkgs, opts...)
 }
 
 // Purge one or more packages including config files.
-func (d *Dpkg) Purge(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (d *Dpkg) Purge(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	d.Lock()
+	defer d.Unlock()
 	return purge(ctx, pkgs, opts...)
 }
 

dpkg/dpkg_linux.go

@@ -17,7 +17,7 @@ func available() bool {
 	return err == nil
 }
 
-func install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func install(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
 	o := snack.ApplyOptions(opts...)
 	var args []string
 	if o.Sudo {
@@ -27,7 +27,14 @@ func install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
 	if o.DryRun {
 		args = append(args, "--simulate")
 	}
-	args = append(args, pkgs...)
+	// dpkg -i takes file paths; use Source if set, otherwise Name
+	for _, t := range pkgs {
+		if t.Source != "" {
+			args = append(args, t.Source)
+		} else {
+			args = append(args, t.Name)
+		}
+	}
 	cmd := exec.CommandContext(ctx, args[0], args[1:]...)
 	var stderr bytes.Buffer
 	cmd.Stderr = &stderr
@@ -41,7 +48,7 @@ func install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
 	return nil
 }
 
-func remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func remove(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
 	o := snack.ApplyOptions(opts...)
 	var args []string
 	if o.Sudo {
@@ -51,7 +58,7 @@ func remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
 	if o.DryRun {
 		args = append(args, "--simulate")
 	}
-	args = append(args, pkgs...)
+	args = append(args, snack.TargetNames(pkgs)...)
 	cmd := exec.CommandContext(ctx, args[0], args[1:]...)
 	var stderr bytes.Buffer
 	cmd.Stderr = &stderr
@@ -61,7 +68,7 @@ func remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
 	return nil
 }
 
-func purge(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func purge(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
 	o := snack.ApplyOptions(opts...)
 	var args []string
 	if o.Sudo {
@@ -71,7 +78,7 @@ func purge(ctx context.Context, pkgs []string, opts ...snack.Option) error {
 	if o.DryRun {
 		args = append(args, "--simulate")
 	}
-	args = append(args, pkgs...)
+	args = append(args, snack.TargetNames(pkgs)...)
 	cmd := exec.CommandContext(ctx, args[0], args[1:]...)
 	var stderr bytes.Buffer
 	cmd.Stderr = &stderr

dpkg/dpkg_other.go

@@ -10,15 +10,15 @@ import (
 
 func available() bool { return false }
 
-func install(_ context.Context, _ []string, _ ...snack.Option) error {
+func install(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 
-func remove(_ context.Context, _ []string, _ ...snack.Option) error {
+func remove(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 
-func purge(_ context.Context, _ []string, _ ...snack.Option) error {
+func purge(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 

mutex.go

@@ -0,0 +1,27 @@
+package snack
+
+import "sync"
+
+// Locker is an embeddable type that provides per-provider mutex locking.
+// Each package manager backend should embed this in its struct to serialize
+// mutating operations (Install, Remove, Purge, Upgrade, Update).
+//
+// Read-only operations (List, Search, Info, IsInstalled, Version) generally
+// don't need the lock, but backends may choose to lock them if the underlying
+// tool doesn't support concurrent reads.
+//
+// Different providers use independent locks, so an apt Install and a snap
+// Install can run concurrently, but two apt Installs will serialize.
+type Locker struct {
+	mu sync.Mutex
+}
+
+// Lock acquires the provider lock. Call before mutating operations.
+func (l *Locker) Lock() {
+	l.mu.Lock()
+}
+
+// Unlock releases the provider lock. Defer after Lock.
+func (l *Locker) Unlock() {
+	l.mu.Unlock()
+}

pacman/pacman.go

@@ -8,7 +8,9 @@ import (
 )
 
 // Pacman wraps the pacman package manager CLI.
-type Pacman struct{}
+type Pacman struct {
+	snack.Locker
+}
 
 // New returns a new Pacman manager.
 func New() *Pacman {
@@ -22,27 +24,37 @@ func (p *Pacman) Name() string { return "pacman" }
 func (p *Pacman) Available() bool { return available() }
 
 // Install one or more packages.
-func (p *Pacman) Install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (p *Pacman) Install(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	p.Lock()
+	defer p.Unlock()
 	return install(ctx, pkgs, opts...)
 }
 
 // Remove one or more packages.
-func (p *Pacman) Remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (p *Pacman) Remove(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	p.Lock()
+	defer p.Unlock()
 	return remove(ctx, pkgs, opts...)
 }
 
 // Purge removes packages including configuration files.
-func (p *Pacman) Purge(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func (p *Pacman) Purge(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
+	p.Lock()
+	defer p.Unlock()
 	return purge(ctx, pkgs, opts...)
 }
 
 // Upgrade all installed packages to their latest versions.
 func (p *Pacman) Upgrade(ctx context.Context, opts ...snack.Option) error {
+	p.Lock()
+	defer p.Unlock()
 	return upgrade(ctx, opts...)
 }
 
 // Update refreshes the package database.
 func (p *Pacman) Update(ctx context.Context) error {
+	p.Lock()
+	defer p.Unlock()
 	return update(ctx)
 }
 

pacman/pacman_linux.go

@@ -58,23 +58,47 @@ func run(ctx context.Context, baseArgs []string, opts snack.Options) (string, er
 	return stdout.String(), nil
 }
 
-func install(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+// formatTargets converts targets to pacman CLI arguments.
+// Pacman uses "pkg=version" for version pinning.
+func formatTargets(targets []snack.Target) []string {
+	args := make([]string, 0, len(targets))
+	for _, t := range targets {
+		if t.Version != "" {
+			args = append(args, t.Name+"="+t.Version)
+		} else {
+			args = append(args, t.Name)
+		}
+	}
+	return args
+}
+
+func install(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
 	o := snack.ApplyOptions(opts...)
-	args := append([]string{"-S", "--noconfirm"}, pkgs...)
+	base := []string{"-S", "--noconfirm"}
+	if o.Refresh {
+		base = []string{"-Sy", "--noconfirm"}
+	}
+	for _, t := range pkgs {
+		if t.FromRepo != "" || o.FromRepo != "" {
+			// Not directly supported by pacman CLI; user should configure repos
+			break
+		}
+	}
+	args := append(base, formatTargets(pkgs)...)
 	_, err := run(ctx, args, o)
 	return err
 }
 
-func remove(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func remove(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
 	o := snack.ApplyOptions(opts...)
-	args := append([]string{"-R", "--noconfirm"}, pkgs...)
+	args := append([]string{"-R", "--noconfirm"}, snack.TargetNames(pkgs)...)
 	_, err := run(ctx, args, o)
 	return err
 }
 
-func purge(ctx context.Context, pkgs []string, opts ...snack.Option) error {
+func purge(ctx context.Context, pkgs []snack.Target, opts ...snack.Option) error {
 	o := snack.ApplyOptions(opts...)
-	args := append([]string{"-Rns", "--noconfirm"}, pkgs...)
+	args := append([]string{"-Rns", "--noconfirm"}, snack.TargetNames(pkgs)...)
 	_, err := run(ctx, args, o)
 	return err
 }

pacman/pacman_other.go

@@ -10,15 +10,15 @@ import (
 
 func available() bool { return false }
 
-func install(_ context.Context, _ []string, _ ...snack.Option) error {
+func install(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 
-func remove(_ context.Context, _ []string, _ ...snack.Option) error {
+func remove(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 
-func purge(_ context.Context, _ []string, _ ...snack.Option) error {
+func purge(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
 	return snack.ErrUnsupportedPlatform
 }
 

target.go

@@ -0,0 +1,10 @@
+package snack
+
+// TargetNames extracts just the package names from a slice of targets.
+func TargetNames(targets []Target) []string {
+	names := make([]string, len(targets))
+	for i, t := range targets {
+		names[i] = t.Name
+	}
+	return names
+}