feat: custom commands (#133)

* Implement custom commands

* Add User: prefix

* Reuse var

* Check if the agent is busy and if so report a warning

* Update README

* fix typo

* Implement user and project scoped custom commands

* Allow for $ARGUMENTS

* UI tweaks

* Update internal/tui/components/dialog/arguments.go

Co-authored-by: Kujtim Hoxha <kujtimii.h@gmail.com>

* Also search in $HOME/.opencode/commands

---------

Co-authored-by: Kujtim Hoxha <kujtimii.h@gmail.com>

internal/tui/components/dialog/custom_commands.go

@@ -0,0 +1,166 @@
+package dialog
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/opencode-ai/opencode/internal/config"
+	"github.com/opencode-ai/opencode/internal/tui/util"
+)
+
+// Command prefix constants
+const (
+	UserCommandPrefix    = "user:"
+	ProjectCommandPrefix = "project:"
+)
+
+// LoadCustomCommands loads custom commands from both XDG_CONFIG_HOME and project data directory
+func LoadCustomCommands() ([]Command, error) {
+	cfg := config.Get()
+	if cfg == nil {
+		return nil, fmt.Errorf("config not loaded")
+	}
+
+	var commands []Command
+
+	// Load user commands from XDG_CONFIG_HOME/opencode/commands
+	xdgConfigHome := os.Getenv("XDG_CONFIG_HOME")
+	if xdgConfigHome == "" {
+		// Default to ~/.config if XDG_CONFIG_HOME is not set
+		home, err := os.UserHomeDir()
+		if err == nil {
+			xdgConfigHome = filepath.Join(home, ".config")
+		}
+	}
+
+	if xdgConfigHome != "" {
+		userCommandsDir := filepath.Join(xdgConfigHome, "opencode", "commands")
+		userCommands, err := loadCommandsFromDir(userCommandsDir, UserCommandPrefix)
+		if err != nil {
+			// Log error but continue - we'll still try to load other commands
+			fmt.Printf("Warning: failed to load user commands from XDG_CONFIG_HOME: %v\n", err)
+		} else {
+			commands = append(commands, userCommands...)
+		}
+	}
+
+	// Load commands from $HOME/.opencode/commands
+	home, err := os.UserHomeDir()
+	if err == nil {
+		homeCommandsDir := filepath.Join(home, ".opencode", "commands")
+		homeCommands, err := loadCommandsFromDir(homeCommandsDir, UserCommandPrefix)
+		if err != nil {
+			// Log error but continue - we'll still try to load other commands
+			fmt.Printf("Warning: failed to load home commands: %v\n", err)
+		} else {
+			commands = append(commands, homeCommands...)
+		}
+	}
+
+	// Load project commands from data directory
+	projectCommandsDir := filepath.Join(cfg.Data.Directory, "commands")
+	projectCommands, err := loadCommandsFromDir(projectCommandsDir, ProjectCommandPrefix)
+	if err != nil {
+		// Log error but return what we have so far
+		fmt.Printf("Warning: failed to load project commands: %v\n", err)
+	} else {
+		commands = append(commands, projectCommands...)
+	}
+
+	return commands, nil
+}
+
+// loadCommandsFromDir loads commands from a specific directory with the given prefix
+func loadCommandsFromDir(commandsDir string, prefix string) ([]Command, error) {
+	// Check if the commands directory exists
+	if _, err := os.Stat(commandsDir); os.IsNotExist(err) {
+		// Create the commands directory if it doesn't exist
+		if err := os.MkdirAll(commandsDir, 0755); err != nil {
+			return nil, fmt.Errorf("failed to create commands directory %s: %w", commandsDir, err)
+		}
+		// Return empty list since we just created the directory
+		return []Command{}, nil
+	}
+
+	var commands []Command
+
+	// Walk through the commands directory and load all .md files
+	err := filepath.Walk(commandsDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		// Skip directories
+		if info.IsDir() {
+			return nil
+		}
+
+		// Only process markdown files
+		if !strings.HasSuffix(strings.ToLower(info.Name()), ".md") {
+			return nil
+		}
+
+		// Read the file content
+		content, err := os.ReadFile(path)
+		if err != nil {
+			return fmt.Errorf("failed to read command file %s: %w", path, err)
+		}
+
+		// Get the command ID from the file name without the .md extension
+		commandID := strings.TrimSuffix(info.Name(), filepath.Ext(info.Name()))
+
+		// Get relative path from commands directory
+		relPath, err := filepath.Rel(commandsDir, path)
+		if err != nil {
+			return fmt.Errorf("failed to get relative path for %s: %w", path, err)
+		}
+
+		// Create the command ID from the relative path
+		// Replace directory separators with colons
+		commandIDPath := strings.ReplaceAll(filepath.Dir(relPath), string(filepath.Separator), ":")
+		if commandIDPath != "." {
+			commandID = commandIDPath + ":" + commandID
+		}
+
+		// Create a command
+		command := Command{
+			ID:          prefix + commandID,
+			Title:       prefix + commandID,
+			Description: fmt.Sprintf("Custom command from %s", relPath),
+			Handler: func(cmd Command) tea.Cmd {
+				commandContent := string(content)
+
+				// Check if the command contains $ARGUMENTS placeholder
+				if strings.Contains(commandContent, "$ARGUMENTS") {
+					// Show arguments dialog
+					return util.CmdHandler(ShowArgumentsDialogMsg{
+						CommandID: cmd.ID,
+						Content:   commandContent,
+					})
+				}
+
+				// No arguments needed, run command directly
+				return util.CmdHandler(CommandRunCustomMsg{
+					Content: commandContent,
+				})
+			},
+		}
+
+		commands = append(commands, command)
+		return nil
+	})
+
+	if err != nil {
+		return nil, fmt.Errorf("failed to load custom commands from %s: %w", commandsDir, err)
+	}
+
+	return commands, nil
+}
+
+// CommandRunCustomMsg is sent when a custom command is executed
+type CommandRunCustomMsg struct {
+	Content string
+}