feat: add shell completion for host names (#37)

- Add ValidArgsFunction to RootCmd for dynamic host completion
- Add 'sshm completion' subcommand for bash/zsh/fish/powershell
- Support prefix matching and case-insensitive filtering
- Respect --config flag for custom SSH config files
- Add comprehensive tests for completion functionality
- Document setup instructions in README

Co-authored-by: Guillaume Archambault <67098259+Gu1llaum-3@users.noreply.github.com>

README.md

@@ -275,6 +275,53 @@ sshm --version
 sshm --help
 ```
 
+### Shell Completion
+
+SSHM supports shell completion for host names, making it easy to connect to hosts without typing full names:
+
+```bash
+sshm <TAB>           # Lists all available hosts
+sshm pro<TAB>        # Completes to hosts starting with "pro" (e.g., prod-server)
+```
+
+**Setup Instructions:**
+
+**Bash:**
+```bash
+# Enable for current session
+source <(sshm completion bash)
+
+# Enable permanently (add to ~/.bashrc)
+echo 'source <(sshm completion bash)' >> ~/.bashrc
+```
+
+**Zsh:**
+```bash
+# Enable for current session
+source <(sshm completion zsh)
+
+# Enable permanently (add to ~/.zshrc)
+echo 'source <(sshm completion zsh)' >> ~/.zshrc
+```
+
+**Fish:**
+```bash
+# Enable for current session
+sshm completion fish | source
+
+# Enable permanently
+sshm completion fish > ~/.config/fish/completions/sshm.fish
+```
+
+**PowerShell:**
+```powershell
+# Enable for current session
+sshm completion powershell | Out-String | Invoke-Expression
+
+# Enable permanently (add to your PowerShell profile)
+Add-Content $PROFILE 'sshm completion powershell | Out-String | Invoke-Expression'
+```
+
 ### Direct Host Connection
 
 SSHM supports direct connection to hosts via the command line, making it easy to integrate into your existing workflow:

cmd/completion.go

@@ -0,0 +1,60 @@
+package cmd
+
+import (
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var completionCmd = &cobra.Command{
+	Use:   "completion [bash|zsh|fish|powershell]",
+	Short: "Generate shell completion script",
+	Long: `Generate shell completion script for sshm.
+
+To load completions:
+
+Bash:
+  $ source <(sshm completion bash)
+  
+  # To load completions for each session, add to your ~/.bashrc:
+  # echo 'source <(sshm completion bash)' >> ~/.bashrc
+
+Zsh:
+  $ source <(sshm completion zsh)
+  
+  # To load completions for each session, add to your ~/.zshrc:
+  # echo 'source <(sshm completion zsh)' >> ~/.zshrc
+
+Fish:
+  $ sshm completion fish | source
+  
+  # To load completions for each session:
+  $ sshm completion fish > ~/.config/fish/completions/sshm.fish
+
+PowerShell:
+  PS> sshm completion powershell | Out-String | Invoke-Expression
+  
+  # To load completions for each session, add to your PowerShell profile:
+  # Add-Content $PROFILE 'sshm completion powershell | Out-String | Invoke-Expression'
+`,
+	DisableFlagsInUseLine: true,
+	ValidArgs:             []string{"bash", "zsh", "fish", "powershell"},
+	Args:                  cobra.MatchAll(cobra.ExactArgs(1), cobra.OnlyValidArgs),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		switch args[0] {
+		case "bash":
+			return cmd.Root().GenBashCompletionV2(os.Stdout, true)
+		case "zsh":
+			return cmd.Root().GenZshCompletion(os.Stdout)
+		case "fish":
+			return cmd.Root().GenFishCompletion(os.Stdout, true)
+		case "powershell":
+			return cmd.Root().GenPowerShellCompletionWithDesc(os.Stdout)
+		}
+		return nil
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(completionCmd)
+}

cmd/completion_test.go

@@ -0,0 +1,285 @@
+package cmd
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/spf13/cobra"
+)
+
+func TestCompletionCommand(t *testing.T) {
+	if completionCmd.Use != "completion [bash|zsh|fish|powershell]" {
+		t.Errorf("Expected Use 'completion [bash|zsh|fish|powershell]', got '%s'", completionCmd.Use)
+	}
+
+	if completionCmd.Short != "Generate shell completion script" {
+		t.Errorf("Expected Short description, got '%s'", completionCmd.Short)
+	}
+}
+
+func TestCompletionCommandValidArgs(t *testing.T) {
+	expected := []string{"bash", "zsh", "fish", "powershell"}
+
+	if len(completionCmd.ValidArgs) != len(expected) {
+		t.Errorf("Expected %d valid args, got %d", len(expected), len(completionCmd.ValidArgs))
+	}
+
+	for i, arg := range expected {
+		if completionCmd.ValidArgs[i] != arg {
+			t.Errorf("Expected ValidArgs[%d] to be '%s', got '%s'", i, arg, completionCmd.ValidArgs[i])
+		}
+	}
+}
+
+func TestCompletionCommandRegistered(t *testing.T) {
+	found := false
+	for _, cmd := range RootCmd.Commands() {
+		if cmd.Name() == "completion" {
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		t.Error("Expected 'completion' command to be registered")
+	}
+}
+
+func TestCompletionBashOutput(t *testing.T) {
+	oldStdout := os.Stdout
+	r, w, _ := os.Pipe()
+	os.Stdout = w
+
+	RootCmd.SetArgs([]string{"completion", "bash"})
+	err := RootCmd.Execute()
+
+	w.Close()
+	os.Stdout = oldStdout
+
+	if err != nil {
+		t.Errorf("Expected no error for bash completion, got %v", err)
+	}
+
+	var buf bytes.Buffer
+	buf.ReadFrom(r)
+	output := buf.String()
+
+	if !strings.Contains(output, "bash completion") || !strings.Contains(output, "sshm") {
+		t.Error("Bash completion output should contain bash completion markers and sshm")
+	}
+}
+
+func TestCompletionZshOutput(t *testing.T) {
+	oldStdout := os.Stdout
+	r, w, _ := os.Pipe()
+	os.Stdout = w
+
+	RootCmd.SetArgs([]string{"completion", "zsh"})
+	err := RootCmd.Execute()
+
+	w.Close()
+	os.Stdout = oldStdout
+
+	if err != nil {
+		t.Errorf("Expected no error for zsh completion, got %v", err)
+	}
+
+	var buf bytes.Buffer
+	buf.ReadFrom(r)
+	output := buf.String()
+
+	if !strings.Contains(output, "compdef") || !strings.Contains(output, "sshm") {
+		t.Error("Zsh completion output should contain compdef and sshm")
+	}
+}
+
+func TestCompletionFishOutput(t *testing.T) {
+	oldStdout := os.Stdout
+	r, w, _ := os.Pipe()
+	os.Stdout = w
+
+	RootCmd.SetArgs([]string{"completion", "fish"})
+	err := RootCmd.Execute()
+
+	w.Close()
+	os.Stdout = oldStdout
+
+	if err != nil {
+		t.Errorf("Expected no error for fish completion, got %v", err)
+	}
+
+	var buf bytes.Buffer
+	buf.ReadFrom(r)
+	output := buf.String()
+
+	if !strings.Contains(output, "complete") || !strings.Contains(output, "sshm") {
+		t.Error("Fish completion output should contain complete command and sshm")
+	}
+}
+
+func TestCompletionPowershellOutput(t *testing.T) {
+	oldStdout := os.Stdout
+	r, w, _ := os.Pipe()
+	os.Stdout = w
+
+	RootCmd.SetArgs([]string{"completion", "powershell"})
+	err := RootCmd.Execute()
+
+	w.Close()
+	os.Stdout = oldStdout
+
+	if err != nil {
+		t.Errorf("Expected no error for powershell completion, got %v", err)
+	}
+
+	var buf bytes.Buffer
+	buf.ReadFrom(r)
+	output := buf.String()
+
+	if !strings.Contains(output, "Register-ArgumentCompleter") || !strings.Contains(output, "sshm") {
+		t.Error("PowerShell completion output should contain Register-ArgumentCompleter and sshm")
+	}
+}
+
+func TestCompletionInvalidShell(t *testing.T) {
+	RootCmd.SetArgs([]string{"completion", "invalid"})
+	err := RootCmd.Execute()
+
+	if err == nil {
+		t.Error("Expected error for invalid shell type")
+	}
+}
+
+func TestCompletionNoArgs(t *testing.T) {
+	RootCmd.SetArgs([]string{"completion"})
+	err := RootCmd.Execute()
+
+	if err == nil {
+		t.Error("Expected error when no shell type provided")
+	}
+}
+
+func TestValidArgsFunction(t *testing.T) {
+	if RootCmd.ValidArgsFunction == nil {
+		t.Fatal("Expected ValidArgsFunction to be set on RootCmd")
+	}
+}
+
+func TestValidArgsFunctionWithSSHConfig(t *testing.T) {
+	tmpDir := t.TempDir()
+	testConfigFile := filepath.Join(tmpDir, "config")
+
+	sshConfig := `Host prod-server
+    HostName 192.168.1.1
+    User admin
+
+Host dev-server
+    HostName 192.168.1.2
+    User developer
+
+Host staging-db
+    HostName 192.168.1.3
+    User dbadmin
+`
+	err := os.WriteFile(testConfigFile, []byte(sshConfig), 0600)
+	if err != nil {
+		t.Fatalf("Failed to write test config: %v", err)
+	}
+
+	originalConfigFile := configFile
+	defer func() { configFile = originalConfigFile }()
+	configFile = testConfigFile
+
+	tests := []struct {
+		name       string
+		toComplete string
+		args       []string
+		wantCount  int
+		wantHosts  []string
+	}{
+		{
+			name:       "empty prefix returns all hosts",
+			toComplete: "",
+			args:       []string{},
+			wantCount:  3,
+			wantHosts:  []string{"prod-server", "dev-server", "staging-db"},
+		},
+		{
+			name:       "prefix filters hosts",
+			toComplete: "prod",
+			args:       []string{},
+			wantCount:  1,
+			wantHosts:  []string{"prod-server"},
+		},
+		{
+			name:       "prefix case insensitive",
+			toComplete: "DEV",
+			args:       []string{},
+			wantCount:  1,
+			wantHosts:  []string{"dev-server"},
+		},
+		{
+			name:       "no match returns empty",
+			toComplete: "nonexistent",
+			args:       []string{},
+			wantCount:  0,
+			wantHosts:  []string{},
+		},
+		{
+			name:       "already has host arg returns nothing",
+			toComplete: "",
+			args:       []string{"existing-host"},
+			wantCount:  0,
+			wantHosts:  []string{},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			completions, directive := RootCmd.ValidArgsFunction(RootCmd, tt.args, tt.toComplete)
+
+			if len(completions) != tt.wantCount {
+				t.Errorf("Expected %d completions, got %d: %v", tt.wantCount, len(completions), completions)
+			}
+
+			if directive != cobra.ShellCompDirectiveNoFileComp {
+				t.Errorf("Expected ShellCompDirectiveNoFileComp, got %v", directive)
+			}
+
+			for _, wantHost := range tt.wantHosts {
+				found := false
+				for _, comp := range completions {
+					if comp == wantHost {
+						found = true
+						break
+					}
+				}
+				if !found {
+					t.Errorf("Expected completion '%s' not found in %v", wantHost, completions)
+				}
+			}
+		})
+	}
+}
+
+func TestValidArgsFunctionWithNonExistentConfig(t *testing.T) {
+	tmpDir := t.TempDir()
+	nonExistentConfig := filepath.Join(tmpDir, "nonexistent")
+
+	originalConfigFile := configFile
+	defer func() { configFile = originalConfigFile }()
+	configFile = nonExistentConfig
+
+	completions, directive := RootCmd.ValidArgsFunction(RootCmd, []string{}, "")
+
+	if directive != cobra.ShellCompDirectiveNoFileComp {
+		t.Errorf("Expected ShellCompDirectiveNoFileComp for non-existent config, got %v", directive)
+	}
+
+	if len(completions) != 0 {
+		t.Errorf("Expected empty completions for non-existent config, got %v", completions)
+	}
+}

cmd/root.go

@@ -54,6 +54,37 @@ Examples:
 	Version:       AppVersion,
 	Args:          cobra.ArbitraryArgs,
 	SilenceUsage:  true,
+	SilenceErrors: true, // We'll handle errors ourselves
+	// ValidArgsFunction provides shell completion for host names
+	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+		// Only complete the first positional argument (host name)
+		if len(args) != 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+
+		var hosts []config.SSHHost
+		var err error
+
+		if configFile != "" {
+			hosts, err = config.ParseSSHConfigFile(configFile)
+		} else {
+			hosts, err = config.ParseSSHConfig()
+		}
+
+		if err != nil {
+			return nil, cobra.ShellCompDirectiveError
+		}
+
+		var completions []string
+		toCompleteLower := strings.ToLower(toComplete)
+		for _, host := range hosts {
+			if strings.HasPrefix(strings.ToLower(host.Name), toCompleteLower) {
+				completions = append(completions, host.Name)
+			}
+		}
+
+		return completions, cobra.ShellCompDirectiveNoFileComp
+	},
 	SilenceErrors: true,
 	RunE: func(cmd *cobra.Command, args []string) error {
 		if len(args) == 0 {