package auth

import (
	"sync"

	"forge.cadoles.com/Cadoles/guesstimate/internal/model"
	"github.com/antonmedv/expr"
	"github.com/antonmedv/expr/vm"
	"github.com/pkg/errors"
)

var (
	ErrUnexpectedRuleResult = errors.New("unexpected rule result")
)

type Service struct {
	rules []*vm.Program
	mutex sync.RWMutex
}

func (s *Service) LoadRules(rawRules ...string) error {
	rules := make([]*vm.Program, 0, len(rawRules))

	for _, rr := range rawRules {
		r, err := expr.Compile(rr)
		if err != nil {
			return errors.WithStack(err)
		}

		rules = append(rules, r)
	}

	s.mutex.Lock()
	s.rules = rules
	s.mutex.Unlock()

	return nil
}

func (s *Service) Authorize(user *model.User) (bool, error) {
	s.mutex.RLock()
	defer s.mutex.RUnlock()

	env := map[string]interface{}{
		"user": user,
	}

	for _, r := range s.rules {
		result, err := expr.Run(r, env)
		if err != nil {
			return false, errors.WithStack(err)
		}

		authorized, ok := result.(bool)
		if !ok {
			return false, errors.WithStack(ErrUnexpectedRuleResult)
		}

		if !authorized {
			return false, nil
		}
	}

	return true, nil
}

func NewService() *Service {
	return &Service{
		rules: make([]*vm.Program, 0),
	}
}