package caddycmd

import (
	"fmt"
	"reflect"
	"runtime/debug"
	"strings"

	"github.com/caddyserver/caddy/v2"
)

type moduleInfo struct {
	caddyModuleID string
	goModule      *debug.Module
	err           error
}

func getModules() (standard, nonstandard, unknown []moduleInfo, err error) {
	bi, ok := debug.ReadBuildInfo()
	if !ok {
		err = fmt.Errorf("no build info")
		return
	}

	for _, modID := range caddy.Modules() {
		modInfo, err := caddy.GetModule(modID)
		if err != nil {
			// that's weird, shouldn't happen
			unknown = append(unknown, moduleInfo{caddyModuleID: modID, err: err})
			continue
		}

		// to get the Caddy plugin's version info, we need to know
		// the package that the Caddy module's value comes from; we
		// can use reflection but we need a non-pointer value (I'm
		// not sure why), and since New() should return a pointer
		// value, we need to dereference it first
		iface := any(modInfo.New())
		if rv := reflect.ValueOf(iface); rv.Kind() == reflect.Ptr {
			iface = reflect.New(reflect.TypeOf(iface).Elem()).Elem().Interface()
		}
		modPkgPath := reflect.TypeOf(iface).PkgPath()

		// now we find the Go module that the Caddy module's package
		// belongs to; we assume the Caddy module package path will
		// be prefixed by its Go module path, and we will choose the
		// longest matching prefix in case there are nested modules
		var matched *debug.Module
		for _, dep := range bi.Deps {
			if strings.HasPrefix(modPkgPath, dep.Path) {
				if matched == nil || len(dep.Path) > len(matched.Path) {
					matched = dep
				}
			}
		}

		caddyModGoMod := moduleInfo{caddyModuleID: modID, goModule: matched}

		if strings.HasPrefix(modPkgPath, caddy.ImportPath) {
			standard = append(standard, caddyModGoMod)
		} else {
			nonstandard = append(nonstandard, caddyModGoMod)
		}
	}
	return
}