refactor: extract core logic to a plain Go package

commands/exec.go

@@ -0,0 +1,131 @@
+package commands
+
+import (
+	"bytes"
+	"errors"
+	"html/template"
+	"path/filepath"
+	"strings"
+
+	"github.com/jimeh/evm/manager"
+	"github.com/spf13/cobra"
+)
+
+func NewExec(mgr *manager.Manager) (*cobra.Command, error) {
+	cmd := &cobra.Command{
+		Use: "exec <binary> [args]...",
+		Short: "Execute named binary from current " +
+			"Emacs version",
+		Args:                  cobra.MinimumNArgs(1),
+		SilenceUsage:          true,
+		DisableFlagParsing:    true,
+		DisableFlagsInUseLine: true,
+		Hidden:                true,
+		ValidArgsFunction:     execValidArgs(mgr),
+		RunE:                  execRunE(mgr),
+	}
+
+	return cmd, nil
+}
+
+func execRunE(mgr *manager.Manager) runEFunc {
+	return func(cmd *cobra.Command, args []string) error {
+		ctx := cmd.Context()
+
+		program := args[0]
+		args = args[1:]
+
+		err := mgr.Exec(ctx, program, args)
+		if err != nil {
+			if errors.Is(err, manager.ErrBinNotFound) {
+				var versions []*manager.Version
+				versions, err = mgr.FindBin(ctx, program)
+				if err != nil {
+					return err
+				}
+
+				return newExecOtherVersionsError(&execOtherVersionsData{
+					Name:        program,
+					Current:     mgr.CurrentVersion(),
+					AvailableIn: versions,
+				})
+			}
+
+			if errors.Is(err, manager.ErrNoCurrentVersion) {
+				return newExecNoCurrentVersionError()
+			}
+
+			return err
+		}
+
+		return nil
+	}
+}
+
+func execValidArgs(mgr *manager.Manager) validArgsFunc {
+	return func(
+		cmd *cobra.Command,
+		args []string,
+		toComplete string,
+	) ([]string, cobra.ShellCompDirective) {
+		var r []string
+
+		if len(args) > 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+
+		version, err := mgr.Get(cmd.Context(), mgr.CurrentVersion())
+		if err != nil {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+
+		for _, bin := range version.Binaries {
+			base := filepath.Base(bin)
+			if toComplete == "" || strings.HasPrefix(base, toComplete) {
+				r = append(r, base)
+			}
+		}
+
+		return r, cobra.ShellCompDirectiveNoFileComp
+	}
+}
+
+func newExecNoCurrentVersionError() error {
+	return errors.New(`No current Emacs version is set.
+
+List all installed versions with: evm list
+Change version with: evm use <version>`,
+	)
+}
+
+type execOtherVersionsData struct {
+	Name        string
+	Current     string
+	AvailableIn []*manager.Version
+}
+
+func newExecOtherVersionsError(data *execOtherVersionsData) error {
+	var buf bytes.Buffer
+	err := execOtherVersionsTemplate.Execute(&buf, data)
+	if err != nil {
+		return err
+	}
+
+	return errors.New(buf.String())
+}
+
+var execOtherVersionsTemplate = template.Must(template.New("other").Parse(
+	`{{ if gt (len .AvailableIn) 0 -}}
+Executable "{{.Name}}" is not available in the current Emacs version ({{.Current}}).
+
+"{{.Name}}" is available in the following Emacs versions:
+{{- range .AvailableIn }}
+  - {{ .Version }}
+{{- end -}}
+{{ else -}}
+Executable "{{.Name}}" is not available in any installed Emacs version.
+{{- end }}
+
+Change version with: evm use <version>
+List all installed versions with: evm list`,
+))