package apigen

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"golang.org/x/mod/modfile"
	"golang.org/x/mod/semver"
)

// Translation metadata was introduced in this release. Consumers of older
// runtimes must upgrade or use an explicitly supported local replacement.
const i18nMinimumVersion = "v0.26.0-preview"

func checkI18nRuntime(spec *Spec, moduleData []byte, directory string) error {
	needed := false
	for _, e := range spec.Errors {
		needed = needed || e.Translation != nil
	}
	if !needed {
		return nil
	}
	mf, err := modfile.Parse("go.mod", moduleData, nil)
	if err != nil {
		return err
	}
	version := ""
	for _, r := range mf.Require {
		if r.Mod.Path == frameworkModule {
			version = r.Mod.Version
		}
	}
	for _, r := range mf.Replace {
		if r.Old.Path != frameworkModule || r.Old.Version != "" && r.Old.Version != version {
			continue
		}
		if r.New.Version != "" {
			version = r.New.Version
			continue
		}
		root := r.New.Path
		if !filepath.IsAbs(root) {
			root = filepath.Join(directory, root)
		}
		data, e := os.ReadFile(filepath.Join(root, "errors", "localization.go"))
		if e == nil && strings.Contains(string(data), "type Translation struct") {
			return nil
		}
		return fmt.Errorf("translation metadata requires a local framework with errors.Translation support")
	}
	if semver.Compare(version, i18nMinimumVersion) < 0 {
		return fmt.Errorf("translation metadata requires %s or newer; use --framework-dir for unpublished source", i18nMinimumVersion)
	}
	return nil
}