runtime_low_level.go

/**
# Copyright (c) 2024, HCUOpt CORPORATION.  All rights reserved.
**/

package oci

import (
	"dcu-container-toolkit/internal/logger"
	"dcu-container-toolkit/internal/lookup"
	"fmt"
)

// NewLowLevelRuntime creates a Runtime that wraps a low-level runtime executable.
// The executable specified is taken from the list of supplied candidates, with the first match
// present in the PATH being selected. A logger is also specified.
func NewLowLevelRuntime(logger logger.Interface, candidates []string) (Runtime, error) {
	runtimePath, err := findRuntime(logger, candidates)
	if err != nil {
		return nil, fmt.Errorf("error locating runtime: %v", err)
	}

	logger.Infof("using low-level runtime %v", runtimePath)
	return NewRuntimeForPath(logger, runtimePath)
}

// findRuntime checks elements in a list of supplied candidates for a matching executable in the PATH.
// The absolute path to the first match is returned.
func findRuntime(logger logger.Interface, candidates []string) (string, error) {
	if len(candidates) == 0 {
		return "", fmt.Errorf("at least one runtime candidate must be specified")
	}

	locator := lookup.NewExecutableLocator(logger, "/")
	for _, candidate := range candidates {
		logger.Debugf("Looking for runtime library '%v'", candidate)
		targets, err := locator.Locate(candidate)
		if err == nil && len(targets) > 0 {
			logger.Debugf("Found runtime binary '%v'", targets)
			return targets[0], nil
		}
		logger.Debugf("Runtime binary '%v' not found: %v (targets=%v)", candidate, err, targets)
	}

	return "", fmt.Errorf("no runtime binary found from candidate list: %v", candidates)
}