// Package project contains convenience functions for working with GCP projects, eg creation, deletion,
// updating billing accounts
package project

import (
	"fmt"
	"log"
	"math/rand"
	"regexp"
	"time"

	cb "google.golang.org/api/cloudbilling/v1"
	crm "google.golang.org/api/cloudresourcemanager/v1"
)

const (
	// ProjectIDRegexpString is the regular expression that represents valid GCP
	// Project ID strings, per https://cloud.google.com/resource-manager/docs/creating-managing-projects#before_you_begin
	ProjectIDRegexpString = `^[a-z][-a-z0-9]{5,29}[a-z0-9]$`
)

func init() {
	_, err := regexp.Compile(ProjectIDRegexpString)
	if err != nil {
		log.Fatal("project.init: failed  to compile the ProjectID regular expression")
	}
}

// CreateWithBillingAccount creates a new gcp project and associates it with the given billing
// account.
func CreateWithBillingAccount(crmSvc *crm.Service, cbSvc *cb.APIService, name, folderID, billing string) (*crm.Project, error) {
	// stay <= 30 characters for gcp naming requirements, with enough room for sufficient
	// randomness
	if len(name) > 19 {
		return nil, fmt.Errorf("len of project name cant be > 19, save room for random id generation")
	}
	projectID := fmt.Sprintf("%s-%s", name, RandAN(29-len(name)))
	project := &crm.Project{
		Name:      name,
		ProjectId: projectID,
		Parent: &crm.ResourceId{
			Id:   folderID,
			Type: "folder",
		},
	}
	createProjectOp, err := crmSvc.Projects.Create(project).Do()
	if err != nil {
		return nil, err
	}
	for {
		if createProjectOp.Done {
			break
		}
		createProjectOp, err = crmSvc.Operations.Get(createProjectOp.Name).Do()
		if err != nil {
			return nil, err
		}
		time.Sleep(5 * time.Second)
	}
	newProject, err := crmSvc.Projects.Get(projectID).Do()
	if err != nil {
		return nil, err
	}

	pbi := &cb.ProjectBillingInfo{
		BillingAccountName: fmt.Sprintf("billingAccounts/%s", billing),
	}
	_, err = cbSvc.Projects.UpdateBillingInfo(fmt.Sprintf("projects/%s", projectID), pbi).Do()
	if err != nil {
		return nil, err
	}
	return newProject, nil
}

// DeleteProject deletes a gcp project associated to the
// provided project id.
func DeleteProject(crmSvc *crm.Service, projectID string) error {
	_, err := crmSvc.Projects.Delete(projectID).Do()
	if err != nil {
		return err
	}
	return nil
}

// generates random names that conform to gcp project naming requirements
func RandAN(n int) string {
	var runes = []rune("abcdefghijklmnopqrstuvwxyz0123456789")
	genName := make([]rune, n)
	for i := range genName {
		genName[i] = runes[rand.Intn(len(runes))] // #nosec G404 - random string is cosmetic
	}
	return string(genName)
}

// IsValidProjectID checks the input string against the regular expression for
// valid GCP Project IDs
func IsValidProjectID(id string) error {
	// We can drop the error because we confirm the Regexp string compiles during
	// init, which is the only type of error regexp.MatchString can return
	ok, _ := regexp.MatchString(ProjectIDRegexpString, id)
	if !ok {
		return &IDValidationError{id}
	}
	return nil
}

// IDValidationError is a contextualized validation error for the Project ID
type IDValidationError struct {
	id string
}

// Error prints the contextualized validaton error message for the Project ID
func (e *IDValidationError) Error() string {
	return fmt.Sprintf("invalid GCP Project ID: %s", e.id)
}