package version

import (
	"fmt"
	"runtime/debug"
)

// Version is stamped in at compile time by `ops/compile.sh`, via:
//
//	-ldflags "-X git.offline-twitter.com/offline-labs/gas-stack/pkg/version.Version=v0.0.4"
//
// It's empty for builds that don't go through that script-- most importantly
// `go install git.offline-twitter.com/offline-labs/gas-stack/cmd@v0.0.4`, which is the normal way
// to install `gas`.  In that case, String() recovers the version from the build info that the Go
// toolchain embeds in every binary.
var Version = ""

// String returns the version of this binary, e.g. "v0.0.4".
func String() string {
	if Version != "" {
		return Version
	}

	info, ok := debug.ReadBuildInfo()
	if !ok {
		return "unknown"
	}

	// Set by `go install module@version`, and (as of Go 1.24) by `go build` in a git checkout
	// that has the tags available.  It's "(devel)" if the toolchain couldn't work out a version.
	if info.Main.Version != "" && info.Main.Version != "(devel)" {
		return info.Main.Version
	}

	// No module version, so fall back to the commit.  This happens when building from a source
	// tree with no usable VCS metadata: a git worktree, a `.git`-less export, or `-buildvcs=false`.
	var revision, dirty string
	for _, setting := range info.Settings {
		switch setting.Key {
		case "vcs.revision":
			revision = setting.Value
		case "vcs.modified":
			if setting.Value == "true" {
				dirty = "-dirty"
			}
		}
	}
	if revision == "" {
		return "unknown"
	}
	if len(revision) > 12 {
		revision = revision[:12]
	}
	return fmt.Sprintf("devel-%s%s", revision, dirty)
}