1 files changed, 164 insertions, 0 deletions
diff --git a/nix2/nix.go b/nix2/nix.go
new file mode 100644
index 0000000..7a86934
--- /dev/null
+++ b/nix2/nix.go
@@ -0,0 +1,164 @@
+package nix2
+
+import (
+	"bytes"
+	"path/filepath"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+
+	"github.com/hashicorp/nomad/helper/pluginutils/hclutils"
+)
+
+const (
+	closureNix = `
+{ path }:
+let
+  nixpkgs = builtins.getFlake "github:nixos/nixpkgs/nixos-22.05";
+  inherit (nixpkgs.legacyPackages.x86_64-linux) buildPackages;
+in buildPackages.closureInfo { rootPaths = builtins.storePath path; }
+`
+)
+
+func prepareNixPackages(taskDir string, packages []string) (hclutils.MapStrStr, error) {
+	mounts := make(hclutils.MapStrStr)
+
+	profileLink := filepath.Join(taskDir, "current-profile")
+	profile, err := nixBuildProfile(packages, profileLink)
+	if err != nil {
+		return nil, fmt.Errorf("Build of the flakes failed: %v", err)
+	}
+
+	closureLink := filepath.Join(taskDir, "current-closure")
+	closure, err := nixBuildClosure(profileLink, closureLink)
+	if err != nil {
+		return nil, fmt.Errorf("Build of the flakes failed: %v", err)
+	}
+
+	mounts[profile] = profile
+
+	if entries, err := os.ReadDir(profile); err != nil {
+		return nil, fmt.Errorf("Couldn't read profile directory: %w", err)
+	} else {
+		for _, entry := range entries {
+			if name := entry.Name(); name != "etc" {
+				mounts[filepath.Join(profile, name)] = "/" + name
+				continue
+			}
+
+			etcEntries, err := os.ReadDir(filepath.Join(profile, "etc"))
+			if err != nil {
+				return nil, fmt.Errorf("Couldn't read profile's /etc directory: %w", err)
+			}
+
+			for _, etcEntry := range etcEntries {
+				etcName := etcEntry.Name()
+				mounts[filepath.Join(profile, "etc", etcName)] = "/etc/" + etcName
+			}
+		}
+	}
+
+	mounts[filepath.Join(closure, "registration")] = "/registration"
+
+	requisites, err := nixRequisites(closure)
+	if err != nil {
+		return nil, fmt.Errorf("Couldn't determine flake requisites: %v", err)
+	}
+
+	for _, requisite := range requisites {
+		mounts[requisite] = requisite
+	}
+
+	return mounts, nil
+}
+
+func nixBuildProfile(flakes []string, link string) (string, error) {
+	cmd := exec.Command("nix", append(
+		[]string{
+			"--extra-experimental-features", "nix-command",
+			"--extra-experimental-features", "flakes",
+			"profile",
+			"install",
+			"--no-write-lock-file",
+			"--profile",
+			link},
+		flakes...)...)
+	stderr := &bytes.Buffer{}
+	cmd.Stderr = stderr
+
+	if err := cmd.Run(); err != nil {
+		return "", fmt.Errorf("%v failed: %s. Err: %v", cmd.Args, stderr.String(), err)
+	}
+
+	if target, err := os.Readlink(link); err == nil {
+		return os.Readlink(filepath.Join(filepath.Dir(link), target))
+	} else {
+		return "", err
+	}
+}
+
+func nixBuildClosure(profile string, link string) (string, error) {
+	cmd := exec.Command(
+		"nix",
+		"--extra-experimental-features", "nix-command",
+		"--extra-experimental-features", "flakes",
+		"build",
+		"--out-link", link,
+		"--expr", closureNix,
+		"--impure",
+		"--no-write-lock-file",
+		"--argstr", "path", profile)
+
+	stderr := &bytes.Buffer{}
+	cmd.Stderr = stderr
+
+	if err := cmd.Run(); err != nil {
+		return "", fmt.Errorf("%v failed: %s. Err: %v", cmd.Args, stderr.String(), err)
+	}
+
+	return os.Readlink(link)
+}
+
+type nixPathInfo struct {
+	Path             string   `json:"path"`
+	NarHash          string   `json:"narHash"`
+	NarSize          uint64   `json:"narSize"`
+	References       []string `json:"references"`
+	Deriver          string   `json:"deriver"`
+	RegistrationTime uint64   `json:"registrationTime"`
+	Signatures       []string `json:"signatures"`
+}
+
+func nixRequisites(path string) ([]string, error) {
+	cmd := exec.Command(
+		"nix",
+		"--extra-experimental-features", "nix-command",
+		"--extra-experimental-features", "flakes",
+		"path-info",
+		"--json",
+		"--recursive",
+		path)
+
+	stdout := &bytes.Buffer{}
+	cmd.Stdout = stdout
+
+	stderr := &bytes.Buffer{}
+	cmd.Stderr = stderr
+
+	if err := cmd.Run(); err != nil {
+		return nil, fmt.Errorf("%v failed: %s. Err: %v", cmd.Args, stderr.String(), err)
+	}
+
+	result := []*nixPathInfo{}
+	if err := json.Unmarshal(stdout.Bytes(), &result); err != nil {
+		return nil, err
+	}
+
+	requisites := []string{}
+	for _, result := range result {
+		requisites = append(requisites, result.Path)
+	}
+
+	return requisites, nil
+}