New static configuration loading system.

Co-authored-by: Mathieu Lonjaret <mathieu.lonjaret@gmail.com>

pkg/cli/commands.go

@@ -0,0 +1,115 @@
+// Package cli provides tools to create commands that support advanced configuration features,
+// sub-commands, and allowing configuration from command-line flags, configuration files, and environment variables.
+package cli
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// Command structure contains program/command information (command name and description).
+type Command struct {
+	Name          string
+	Description   string
+	Configuration interface{}
+	Resources     []ResourceLoader
+	Run           func([]string) error
+	Hidden        bool
+	subCommands   []*Command
+}
+
+// AddCommand Adds a sub command.
+func (c *Command) AddCommand(cmd *Command) error {
+	if c == nil || cmd == nil {
+		return nil
+	}
+
+	if c.Name == cmd.Name {
+		return fmt.Errorf("child command cannot have the same name as their parent: %s", cmd.Name)
+	}
+
+	c.subCommands = append(c.subCommands, cmd)
+	return nil
+}
+
+// Execute Executes a command.
+func Execute(cmd *Command) error {
+	return execute(cmd, os.Args, true)
+}
+
+func execute(cmd *Command, args []string, root bool) error {
+	if len(args) == 1 {
+		if err := run(cmd, args); err != nil {
+			return fmt.Errorf("command %s error: %v", args[0], err)
+		}
+		return nil
+	}
+
+	if root && cmd.Name != args[1] && !contains(cmd.subCommands, args[1]) {
+		if err := run(cmd, args[1:]); err != nil {
+			return fmt.Errorf("command %s error: %v", filepath.Base(args[0]), err)
+		}
+		return nil
+	}
+
+	if len(args) >= 2 && cmd.Name == args[1] {
+		if err := run(cmd, args[2:]); err != nil {
+			return fmt.Errorf("command %s error: %v", cmd.Name, err)
+		}
+		return nil
+	}
+
+	if len(cmd.subCommands) == 0 {
+		if err := run(cmd, args[1:]); err != nil {
+			return fmt.Errorf("command %s error: %v", cmd.Name, err)
+		}
+		return nil
+	}
+
+	for _, subCmd := range cmd.subCommands {
+		if len(args) >= 2 && subCmd.Name == args[1] {
+			return execute(subCmd, args[1:], false)
+		}
+	}
+
+	return fmt.Errorf("command not found: %v", args)
+}
+
+func run(cmd *Command, args []string) error {
+	if isHelp(args) {
+		return PrintHelp(os.Stdout, cmd)
+	}
+
+	if cmd.Run == nil {
+		_ = PrintHelp(os.Stdout, cmd)
+		return errors.New("command not found")
+	}
+
+	if cmd.Configuration == nil {
+		return cmd.Run(args)
+	}
+
+	for _, resource := range cmd.Resources {
+		done, err := resource.Load(args, cmd)
+		if err != nil {
+			return err
+		}
+		if done {
+			break
+		}
+	}
+
+	return cmd.Run(args)
+}
+
+func contains(cmds []*Command, name string) bool {
+	for _, cmd := range cmds {
+		if cmd.Name == name {
+			return true
+		}
+	}
+
+	return false
+}