feat: implemented initial login command

internal/command/command.go

@@ -0,0 +1,76 @@
+package command
+
+import (
+	"fmt"
+
+	"github.com/StevanFreeborn/gator/internal/state"
+)
+
+type Command struct {
+	Name    string
+	Handler CommandHandler
+}
+
+type CommandHandler func(s *state.State) error
+
+func newCommand(name string, handler CommandHandler) *Command {
+	return &Command{
+		Name:    name,
+		Handler: handler,
+	}
+}
+
+type CommandRegistry struct {
+	commands map[string]*Command
+}
+
+func (c *CommandRegistry) register(cmd *Command) error {
+	c.commands[cmd.Name] = cmd
+	return nil
+}
+
+func NewRegistry() *CommandRegistry {
+	cr := CommandRegistry{
+		commands: map[string]*Command{},
+	}
+
+	commands := []*Command{
+		loginCommand(),
+	}
+
+	for _, cmd := range commands {
+		cr.register(cmd)
+	}
+
+	return &cr
+}
+
+func (c *CommandRegistry) RunCommand(cmdName string, s *state.State) error {
+	cmd, found := c.commands[cmdName]
+
+	if !found {
+		return fmt.Errorf("No '%s' registered", cmdName)
+	}
+
+	return cmd.Handler(s)
+}
+
+func loginCommand() *Command {
+	return newCommand("login", func(s *state.State) error {
+		if len(s.Arguments) == 0 {
+			return fmt.Errorf("Did not receive expected username argument")
+		}
+
+		username := s.Arguments[0]
+
+		err := s.Config.SetUser(username)
+
+		if err != nil {
+			return err
+		}
+
+		fmt.Printf("Current user set to '%s'\n", username)
+
+		return nil
+	})
+}