Command Manager

The Command Manager is the core abstraction for managing command versions in CMDR. It provides a layered architecture with different providers for different concerns.

Overview

Command managers follow a chain-of-responsibility pattern where each manager wraps another, adding specific functionality:

DownloadManager → BinaryManager → DatabaseManager

Each layer delegates to the next while adding its own behavior.

CommandManager Interface

The core interface defines operations for managing commands¹:

type CommandManager interface {
    Close() error
    Provider() CommandProvider
    Query() (CommandQuery, error)
    Define(name, version, location string) (Command, error)
    Undefine(name, version string) error
    Activate(name, version string) error
    Deactivate(name string) error
}

Manager Implementations

DatabaseManager

Source: core/manager/database.go

Provider: CommandProviderDatabase

Responsibilities:

• Persist command metadata in BoltDB via Storm ORM
• Query commands by name, version, location, activation status
• Wrap BinaryManager for actual file operations

Key Operations:

// Define a command - saves to database and delegates to BinaryManager
func (m *DatabaseManager) Define(name, version, location string) (Command, error)

// Query commands with flexible filtering
func (m *DatabaseManager) Query() (CommandQuery, error)

// Activate - deactivates others, updates DB, delegates to BinaryManager
func (m *DatabaseManager) Activate(name, version string) error

Implementation Details:

• Uses version matching to support both raw and semantic versions²
• Enforces single activation per command name
• Prevents deletion of activated commands³

BinaryManager

Source: core/manager/binary.go

Provider: CommandProviderBinary

Responsibilities:

• Manage physical binary files in ~/.cmdr/shims/<command>/
• Create symlinks or copies of binaries
• Handle version normalization (e.g., 1.0 → 1.0.0)
• Create activation symlinks in bin/ directory

Directory Structure:

~/.cmdr/
├── bin/
│   └── kubectl -> ../shims/kubectl/kubectl_1.28.0
└── shims/
    └── kubectl/
        ├── kubectl_1.28.0
        └── kubectl_1.29.0

Key Operations:

// Define - copy or link binary to shims directory
func (m *BinaryManager) Define(name, version, location string) (Command, error)

// Activate - create symlink in bin/ directory
func (m *BinaryManager) Activate(name, version string) error

// Deactivate - remove symlink from bin/ directory
func (m *BinaryManager) Deactivate(name string) error

Link Modes:

The manager supports two link modes⁴:

Mode	Behavior	Use Case
copy (default)	Copy binary to shims directory	Maximum compatibility
link	Create symlink to original location	Save disk space

Set via configuration:

cmdr config set -k core.link_mode -v link

DownloadManager

Source: core/manager/download.go

Provider: CommandProviderDownload

Responsibilities:

• Download binaries from URLs
• Validate downloaded files
• Apply URL rewrite rules
• Delegate to BinaryManager for storage

Key Operations:

// Define - download from URL, then delegate to BinaryManager
func (m *DownloadManager) Define(name, version, location string) (Command, error)

URL Rewriting:

Supports URL replacement patterns for proxying downloads:

// Configuration example
{
    "match": "^https://raw.githubusercontent.com/.*$",
    "template": "https://ghproxy.com/{{ .input | urlquery }}"
}

DoctorManager

Source: core/manager/doctor.go

Provider: CommandProviderDoctor

Responsibilities:

• Diagnose installation issues
• Verify directory structure
• Check database integrity
• Validate PATH configuration

Command Interface

Commands are read-only views of managed commands⁵:

type Command interface {
    GetName() string
    GetVersion() string
    GetActivated() bool
    GetLocation() string
}

CommandQuery Interface

Provides fluent API for filtering commands⁶:

type CommandQuery interface {
    WithName(name string) CommandQuery
    WithVersion(version string) CommandQuery
    WithActivated(activated bool) CommandQuery
    WithLocation(location string) CommandQuery

    All() ([]Command, error)
    One() (Command, error)
    Count() (int, error)
}

Example Usage:

// Find activated kubectl command
query, _ := manager.Query()
cmd, _ := query.WithName("kubectl").WithActivated(true).One()

// List all versions of kubectl
query, _ := manager.Query()
commands, _ := query.WithName("kubectl").All()

Factory Registration

Managers register themselves via the factory pattern⁷:

// In init() function
core.RegisterCommandManagerFactory(core.CommandProviderDatabase, func(cfg Configuration) (CommandManager, error) {
    // Create BinaryManager first
    mgr, _ := core.NewCommandManager(core.CommandProviderBinary, cfg)
    db, _ := core.GetDatabase()
    return NewDatabaseManager(db, mgr), nil
})

Version Handling

CMDR normalizes versions using semantic versioning:

• Input: 1.0, v1.0.0, 1.0.0
• Normalized: 1.0.0

This ensures consistent storage and lookup across different version formats.

---

---

1. CommandManager interface in core/command.go L36-L47 ↩

2. Version matching in core/manager/database.go L12-L18 ↩

3. Activated command protection in core/manager/database.go L104-L106 ↩

4. Link mode configuration in core/manager/binary.go L415-L425 ↩

5. Command interface in core/command.go L18-L23 ↩

6. CommandQuery interface in core/command.go L25-L34 ↩

7. Factory registration in core/manager/database.go L182-L196 ↩