package githubclient

import (
	"context"
	"fmt"
	"net/http"
	"regexp"
	"time"

	"go.uber.org/multierr"
	"golang.org/x/oauth2"

	"github.com/bradleyfalzon/ghinstallation/v2"
)

type Config struct {
	// HTTPS Github Repository URL
	Repository string

	// For Github App authentication
	PrivateKey     []byte // PEM encoded private key. If empty, use oauth.
	AppID          int64
	InstallationID int64 // Optional. See documentation

	AccessToken string // optional personal access token
}

var (
	errEmptyRepositoryError   = fmt.Errorf("Repository must be provided")
	errInvalidRepositoryError = fmt.Errorf("Invalid repository URL")
	errEmptyKeyError          = fmt.Errorf("PrivateKey or AccessToken must be set")
	errEmptyAppIDError        = fmt.Errorf("AppID must be greater than zero")
)

// Ensure the repository will work with the GithubOwner and GithubRepo methods
var reValidRepository = regexp.MustCompile("^https://github.com/[^/]+/[^/]+([.]git)?$")

var (
	// used to remove everything from the Repository url, except the owner.
	reGithubOwner = regexp.MustCompile(`^https://github.com/|/[^/]*$`)
	// used to remove everything from the Repository url, except the repo name.
	reGithubRepo = regexp.MustCompile(`^.*/|[.]git$`)
)

// Owner uses the Repository url to find the owner.
func (c *Config) Owner() string {
	return reGithubOwner.ReplaceAllString(c.Repository, "")
}

// Repo uses the Repository url to find the repository name.
func (c *Config) Repo() string {
	return reGithubRepo.ReplaceAllString(c.Repository, "")
}

// Validate returns an error if the configuration is missing required fields.
func (c *Config) Validate() error {
	var errs []error
	if c.AccessToken != "" { // if the access token is set dont worry about the rest
		return nil
	}
	if c.PrivateKey == nil && c.AccessToken == "" {
		errs = append(errs, errEmptyKeyError)
	}
	if c.AppID <= 0 {
		errs = append(errs, errEmptyAppIDError)
	}
	if c.Repository == "" {
		errs = append(errs, errEmptyRepositoryError)
	}
	if !reValidRepository.MatchString(c.Repository) {
		errs = append(errs, errInvalidRepositoryError)
	}
	return multierr.Combine(errs...)
}

func (c *Config) HTTPClient() (*http.Client, error) {
	if err := c.Validate(); err != nil {
		return nil, err
	}

	if c.AccessToken != "" {
		return oauth2.NewClient(context.Background(), oauth2.StaticTokenSource(
			&oauth2.Token{AccessToken: c.AccessToken},
		)), nil
	}

	transport := http.DefaultTransport
	const timeout = 5 * time.Minute

	if c.InstallationID == 0 {
		// Create an AppsService API compatible http client.
		tr, err := ghinstallation.NewAppsTransport(transport, c.AppID, c.PrivateKey)
		if err != nil {
			return nil, err
		}
		return &http.Client{
			Transport: tr,
			Timeout:   timeout,
		}, nil
	}
	tr, err := ghinstallation.New(transport, c.AppID, c.InstallationID, c.PrivateKey)
	if err != nil {
		return nil, err
	}
	return &http.Client{
		Transport: tr,
		Timeout:   timeout,
	}, nil
}