package github

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"math/rand"
	"net/http"
	"regexp"
	"sort"
	"strings"
	"time"

	"github.com/pkg/errors"

	"github.com/MichaelMure/git-bug/bridge/core"
	"github.com/MichaelMure/git-bug/bridge/core/auth"
	"github.com/MichaelMure/git-bug/cache"
	"github.com/MichaelMure/git-bug/input"
	"github.com/MichaelMure/git-bug/repository"
)

var (
	ErrBadProjectURL = errors.New("bad project url")
)

func (g *Github) ValidParams() map[string]interface{} {
	return map[string]interface{}{
		"URL":        nil,
		"Login":      nil,
		"CredPrefix": nil,
		"TokenRaw":   nil,
		"Owner":      nil,
		"Project":    nil,
	}
}

func (g *Github) Configure(repo *cache.RepoCache, params core.BridgeParams) (core.Configuration, error) {
	var err error
	var owner string
	var project string

	// getting owner and project name
	switch {
	case params.Owner != "" && params.Project != "":
		// first try to use params if both or project and owner are provided
		owner = params.Owner
		project = params.Project
	case params.URL != "":
		// try to parse params URL and extract owner and project
		owner, project, err = splitURL(params.URL)
		if err != nil {
			return nil, err
		}
	default:
		// terminal prompt
		owner, project, err = promptURL(repo)
		if err != nil {
			return nil, err
		}
	}

	// validate project owner
	ok, err := validateUsername(owner)
	if err != nil {
		return nil, err
	}
	if !ok {
		return nil, fmt.Errorf("invalid parameter owner: %v", owner)
	}

	var login string
	var cred auth.Credential

	switch {
	case params.CredPrefix != "":
		cred, err = auth.LoadWithPrefix(repo, params.CredPrefix)
		if err != nil {
			return nil, err
		}
		l, ok := cred.GetMetadata(auth.MetaKeyLogin)
		if !ok {
			return nil, fmt.Errorf("credential doesn't have a login")
		}
		login = l
	case params.TokenRaw != "":
		token := auth.NewToken(target, params.TokenRaw)
		login, err = getLoginFromToken(token)
		if err != nil {
			return nil, err
		}
		token.SetMetadata(auth.MetaKeyLogin, login)
		cred = token
	default:
		login = params.Login
		if login == "" {
			login, err = input.Prompt("Github login", "login", input.Required, usernameValidator)
			if err != nil {
				return nil, err
			}
		}
		cred, err = promptTokenOptions(repo, login, owner, project)
		if err != nil {
			return nil, err
		}
	}

	token, ok := cred.(*auth.Token)
	if !ok {
		return nil, fmt.Errorf("the Github bridge only handle token credentials")
	}

	// verify access to the repository with token
	ok, err = validateProject(owner, project, token)
	if err != nil {
		return nil, err
	}
	if !ok {
		return nil, fmt.Errorf("project doesn't exist or authentication token has an incorrect scope")
	}

	conf := make(core.Configuration)
	conf[core.ConfigKeyTarget] = target
	conf[confKeyOwner] = owner
	conf[confKeyProject] = project

	err = g.ValidateConfig(conf)
	if err != nil {
		return nil, err
	}

	// don't forget to store the now known valid token
	if !auth.IdExist(repo, cred.ID()) {
		err = auth.Store(repo, cred)
		if err != nil {
			return nil, err
		}
	}

	return conf, core.FinishConfig(repo, metaKeyGithubLogin, login)
}

func (Github) ValidateConfig(conf core.Configuration) error {
	if v, ok := conf[core.ConfigKeyTarget]; !ok {
		return fmt.Errorf("missing %s key", core.ConfigKeyTarget)
	} else if v != target {
		return fmt.Errorf("unexpected target name: %v", v)
	}

	if _, ok := conf[confKeyOwner]; !ok {
		return fmt.Errorf("missing %s key", confKeyOwner)
	}

	if _, ok := conf[confKeyProject]; !ok {
		return fmt.Errorf("missing %s key", confKeyProject)
	}

	return nil
}

func usernameValidator(_ string, value string) (string, error) {
	ok, err := validateUsername(value)
	if err != nil {
		return "", err
	}
	if !ok {
		return "invalid login", nil
	}
	return "", nil
}

func requestToken(note, login, password string, scope string) (*http.Response, error) {
	return requestTokenWith2FA(note, login, password, "", scope)
}

func requestTokenWith2FA(note, login, password, otpCode string, scope string) (*http.Response, error) {
	url := fmt.Sprintf("%s/authorizations", githubV3Url)
	params := struct {
		Scopes      []string `json:"scopes"`
		Note        string   `json:"note"`
		Fingerprint string   `json:"fingerprint"`
	}{
		Scopes:      []string{scope},
		Note:        note,
		Fingerprint: randomFingerprint(),
	}

	data, err := json.Marshal(params)
	if err != nil {
		return nil, err
	}

	req, err := http.NewRequest("POST", url, bytes.NewBuffer(data))
	if err != nil {
		return nil, err
	}

	req.SetBasicAuth(login, password)
	req.Header.Set("Content-Type", "application/json")

	if otpCode != "" {
		req.Header.Set("X-GitHub-OTP", otpCode)
	}

	client := &http.Client{
		Timeout: defaultTimeout,
	}

	return client.Do(req)
}

func decodeBody(body io.ReadCloser) (string, error) {
	data, _ := ioutil.ReadAll(body)

	aux := struct {
		Token string `json:"token"`
	}{}

	err := json.Unmarshal(data, &aux)
	if err != nil {
		return "", err
	}

	if aux.Token == "" {
		return "", fmt.Errorf("no token found in response: %s", string(data))
	}

	return aux.Token, nil
}

func randomFingerprint() string {
	// Doesn't have to be crypto secure, it's just to avoid token collision
	rand.Seed(time.Now().UnixNano())
	var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
	b := make([]rune, 32)
	for i := range b {
		b[i] = letterRunes[rand.Intn(len(letterRunes))]
	}
	return string(b)
}

func promptTokenOptions(repo repository.RepoConfig, login, owner, project string) (auth.Credential, error) {
	creds, err := auth.List(repo,
		auth.WithTarget(target),
		auth.WithKind(auth.KindToken),
		auth.WithMeta(auth.MetaKeyLogin, login),
	)
	if err != nil {
		return nil, err
	}

	cred, err := input.PromptCredentialWithInteractive(target, "token", creds)
	switch err {
	case nil:
		return cred, nil
	case input.ErrDirectPrompt:
		return promptToken()
	case input.ErrInteractiveCreation:
		value, err := loginAndRequestToken(login, owner, project)
		if err != nil {
			return nil, err
		}
		token := auth.NewToken(target, value)
		token.SetMetadata(auth.MetaKeyLogin, login)
		return token, nil
	default:
		return nil, err
	}
}

func promptToken() (*auth.Token, error) {
	fmt.Println("You can generate a new token by visiting https://github.com/settings/tokens.")
	fmt.Println("Choose 'Generate new token' and set the necessary access scope for your repository.")
	fmt.Println()
	fmt.Println("The access scope depend on the type of repository.")
	fmt.Println("Public:")
	fmt.Println("  - 'public_repo': to be able to read public repositories")
	fmt.Println("Private:")
	fmt.Println("  - 'repo'       : to be able to read private repositories")
	fmt.Println()

	re, err := regexp.Compile(`^[a-zA-Z0-9]{40}$`)
	if err != nil {
		panic("regexp compile:" + err.Error())
	}

	var login string

	validator := func(name string, value string) (complaint string, err error) {
		if !re.MatchString(value) {
			return "token has incorrect format", nil
		}
		login, err = getLoginFromToken(auth.NewToken(target, value))
		if err != nil {
			return fmt.Sprintf("token is invalid: %v", err), nil
		}
		return "", nil
	}

	rawToken, err := input.Prompt("Enter token", "token", input.Required, validator)
	if err != nil {
		return nil, err
	}

	token := auth.NewToken(target, rawToken)
	token.SetMetadata(auth.MetaKeyLogin, login)

	return token, nil
}

func loginAndRequestToken(login, owner, project string) (string, error) {
	fmt.Println("git-bug will now generate an access token in your Github profile. Your credential are not stored and are only used to generate the token. The token is stored in the global git config.")
	fmt.Println()
	fmt.Println("The access scope depend on the type of repository.")
	fmt.Println("Public:")
	fmt.Println("  - 'public_repo': to be able to read public repositories")
	fmt.Println("Private:")
	fmt.Println("  - 'repo'       : to be able to read private repositories")
	fmt.Println()

	// prompt project visibility to know the token scope needed for the repository
	i, err := input.PromptChoice("repository visibility", []string{"public", "private"})
	if err != nil {
		return "", err
	}
	isPublic := i == 0

	password, err := input.PromptPassword("Password", "password", input.Required)
	if err != nil {
		return "", err
	}

	var scope string
	if isPublic {
		// public_repo is requested to be able to read public repositories
		scope = "public_repo"
	} else {
		// 'repo' is request to be able to read private repositories
		// /!\ token will have read/write rights on every private repository you have access to
		scope = "repo"
	}

	// Attempt to authenticate and create a token

	note := fmt.Sprintf("git-bug - %s/%s", owner, project)

	resp, err := requestToken(note, login, password, scope)
	if err != nil {
		return "", err
	}

	defer resp.Body.Close()

	// Handle 2FA is needed
	OTPHeader := resp.Header.Get("X-GitHub-OTP")
	if resp.StatusCode == http.StatusUnauthorized && OTPHeader != "" {
		otpCode, err := input.PromptPassword("Two-factor authentication code", "code", input.Required)
		if err != nil {
			return "", err
		}

		resp, err = requestTokenWith2FA(note, login, password, otpCode, scope)
		if err != nil {
			return "", err
		}

		defer resp.Body.Close()
	}

	if resp.StatusCode == http.StatusCreated {
		return decodeBody(resp.Body)
	}

	b, _ := ioutil.ReadAll(resp.Body)
	return "", fmt.Errorf("error creating token %v: %v", resp.StatusCode, string(b))
}

func promptURL(repo repository.RepoCommon) (string, string, error) {
	validRemotes, err := getValidGithubRemoteURLs(repo)
	if err != nil {
		return "", "", err
	}

	validator := func(name, value string) (string, error) {
		_, _, err := splitURL(value)
		if err != nil {
			return err.Error(), nil
		}
		return "", nil
	}

	url, err := input.PromptURLWithRemote("Github project URL", "URL", validRemotes, input.Required, validator)
	if err != nil {
		return "", "", err
	}

	return splitURL(url)
}

// splitURL extract the owner and project from a github repository URL. It will remove the
// '.git' extension from the URL before parsing it.
// Note that Github removes the '.git' extension from projects names at their creation
func splitURL(url string) (owner string, project string, err error) {
	cleanURL := strings.TrimSuffix(url, ".git")

	re := regexp.MustCompile(`github\.com[/:]([a-zA-Z0-9\-_]+)/([a-zA-Z0-9\-_.]+)`)

	res := re.FindStringSubmatch(cleanURL)
	if res == nil {
		return "", "", ErrBadProjectURL
	}

	owner = res[1]
	project = res[2]
	return
}

func getValidGithubRemoteURLs(repo repository.RepoCommon) ([]string, error) {
	remotes, err := repo.GetRemotes()
	if err != nil {
		return nil, err
	}

	urls := make([]string, 0, len(remotes))
	for _, url := range remotes {
		// split url can work again with shortURL
		owner, project, err := splitURL(url)
		if err == nil {
			shortURL := fmt.Sprintf("%s/%s/%s", "github.com", owner, project)
			urls = append(urls, shortURL)
		}
	}

	sort.Strings(urls)

	return urls, nil
}

func validateUsername(username string) (bool, error) {
	url := fmt.Sprintf("%s/users/%s", githubV3Url, username)

	client := &http.Client{
		Timeout: defaultTimeout,
	}

	resp, err := client.Get(url)
	if err != nil {
		return false, err
	}

	err = resp.Body.Close()
	if err != nil {
		return false, err
	}

	return resp.StatusCode == http.StatusOK, nil
}

func validateProject(owner, project string, token *auth.Token) (bool, error) {
	url := fmt.Sprintf("%s/repos/%s/%s", githubV3Url, owner, project)

	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return false, err
	}

	// need the token for private repositories
	req.Header.Set("Authorization", fmt.Sprintf("token %s", token.Value))

	client := &http.Client{
		Timeout: defaultTimeout,
	}

	resp, err := client.Do(req)
	if err != nil {
		return false, err
	}

	err = resp.Body.Close()
	if err != nil {
		return false, err
	}

	return resp.StatusCode == http.StatusOK, nil
}

func getLoginFromToken(token *auth.Token) (string, error) {
	ctx, cancel := context.WithTimeout(context.Background(), defaultTimeout)
	defer cancel()

	client := buildClient(token)

	var q loginQuery

	err := client.Query(ctx, &q, nil)
	if err != nil {
		return "", err
	}
	if q.Viewer.Login == "" {
		return "", fmt.Errorf("github say username is empty")
	}

	return q.Viewer.Login, nil
}