package api

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"io"
	"os"
	"time"
)

const (
	DefaultContentType  = "application/json"
	DefaultAccept       = DefaultContentType
	DefaultCacheControl = "no-cache"
)

type ClientOptions struct {
	Url          string `json:"url"`
	RedirectUrl  string `json:"redirect_url"`

	AuthCode string `json:"auth_code"`

	ClientId     string `json:"client_id"`
	ClientSecret string `json:"client_secret"`

	AccessToken  string `json:"access_token"`

	ExpirationAt time.Time `json:"expiration_at,omitempty"`
	RefreshToken string `json:"refresh_token"`
}

type Client struct {
	options *ClientOptions
	BaseUrl *url.URL
	secretStoreFilePath string
	Debug bool `json`
}

type requestOptions struct {
	HttpMethod string
	Body       interface{}
	Headers    map[string]string
	Abs  bool
}

type OauthTokenResponse struct {
	TokenType    string `json:"token_type"`
	ExpiresIn    int    `json:"expires_in"`
	AccessToken  string `json:"access_token"`
	RefreshToken string `json:"refresh_token"`
}

type TokenPair struct {
	Access, Refresh string
}

func NewApi(secretPath string) (*Client, error) {
	ret := &Client{
		secretStoreFilePath: secretPath,
	}
	options, err := ret.readSecret()
	if err != nil {
		return nil, err
	}
	fmt.Println("opts:", options)

	if options.Url == "" || options.RedirectUrl == "" {
		return nil, errors.New("AmoCrm: Invalid options: Url")
	}
	resolvedUrl, err := url.Parse(options.Url)
	if err != nil {
		return nil, err
	}

	ret.BaseUrl = resolvedUrl

	if err != nil {
		return nil, err
	}
	ret.options = options

	var (
		//pair *TokenPair
		exchangeErr error
		exchanged bool
	)
	if ret.options.AccessToken == "" && ret.options.RefreshToken == "" {
		if ret.options.ClientSecret == "" ||
				ret.options.ClientId == "" ||
				ret.options.AuthCode == "" {
					return nil, errors.New("AmoCrm: invalid options: ExchangeAuth")
		}
		_, exchangeErr = ret.ExchangeAuth()
		exchanged = true
	}

	if (!exchanged || exchangeErr != nil) && options.RefreshToken != "" {
		// Refreshing token before the work.
		// Should think of how often should refresh
		// the token. (see the ExpiresIn)
		_, err = ret.RefreshToken()
		if err != nil {
			return nil, err
		}
	}

	return &Client{
		options: options,
		BaseUrl: resolvedUrl,
	}, nil
}

func (api *Client) readSecret() (*ClientOptions, error) {
	f, err := os.Open(api.secretStoreFilePath)
	if err != nil {
		return nil, err
	}

	bts, err := io.ReadAll(f)
	if err != nil {
		return nil, err
	}


	ret := ClientOptions{}
	err = json.Unmarshal(bts, &ret)
	if err != nil {
		return nil, err
	}

	return &ret, nil
}

func (api *Client) writeSecret() error {
	bts, err := json.MarshalIndent(api.options, "", "\t")
	if err != nil {
		return err
	}

	err = os.WriteFile(api.secretStoreFilePath, bts, 0644)
	if err != nil {
		return err
	}
	return err
}

func (api *Client) rdoRequest(resourceUrl string, requestParams requestOptions, result interface{}) error {
	var (
		requestUrl *url.URL
		err error
	)

	if !requestParams.Abs {
		resolvedUrl, err := url.Parse(resourceUrl)
		if err != nil {
			return err
		}

		requestUrl = api.BaseUrl.ResolveReference(resolvedUrl)
	} else {
		requestUrl, err = url.Parse(resourceUrl)
		if err != nil {
			return err
		}
	}

	requestBody := new(bytes.Buffer)
	if requestParams.Body != nil {
		encoder := json.NewEncoder(requestBody)
		if err := encoder.Encode(requestParams.Body); err != nil {
			return err
		}
	}

	request, err := http.NewRequest(requestParams.HttpMethod, requestUrl.String(), requestBody)
	if err != nil {
		return err
	}

	if requestParams.Headers != nil {
		for k, v := range requestParams.Headers {
			request.Header.Set(k, v)
		}
	}

	response, err := http.DefaultClient.Do(request)
	if api.Debug {
		fmt.Printf("\nAmo request: %+v\nAmo repsonse: %+v\n", request, response)
	}
	if response == nil {
		return NoInternetErr
	}
	if err != nil {
		return errors.New(fmt.Sprintf(
			"Request error: %s %d %s %s",
			err.Error(),
			response.StatusCode,
			requestParams.HttpMethod,
			resourceUrl,
		))
	}
	defer response.Body.Close()
	if response.StatusCode == 204 {
		return NoContentErr
	}

	if response.StatusCode >= 400 {
		if response.StatusCode == 401 {
			return NoAuthErr
		}

		bodyBytes, _ := ioutil.ReadAll(response.Body)
		return errors.New(fmt.Sprintf(
			"%s %d %s %s",
			string(bodyBytes),
			response.StatusCode,
			requestParams.HttpMethod,
			resourceUrl,
		))
	}

	if result != nil {
		decoder := json.NewDecoder(response.Body)
		err = decoder.Decode(result)
		if err != nil {
			return err
		}
	}

	return nil
}
func (api *Client) doRequest(
	resourceUrl string, requestParams requestOptions, result any,
) error {
	var err error
	err = api.rdoRequest(resourceUrl, requestParams, result)
	if err == NoAuthErr && api.options.RefreshToken != "" {
		_, err = api.RefreshToken()
		if err != nil {
			return nil
		}
		return api.rdoRequest(resourceUrl, requestParams, result)
	} else if err != nil {
		return err
	}

	return nil
}

func (api *Client) ExchangeAuth() (*TokenPair, error) {
	result := &OauthTokenResponse{}
	request := map[string] string {
		"client_id": api.options.ClientId,
		"client_secret": api.options.ClientSecret,
		"grant_type": "authorization_code",
		"code": api.options.AuthCode,
		"redirect_uri": api.options.RedirectUrl,
	}

	err := api.rdoRequest("/oauth2/access_token", requestOptions{
		HttpMethod: http.MethodPost,
		Body:       request,
		Headers:    getHeaders(""),
	}, result)
	if err != nil {
		return nil, err
	}

	ret := &TokenPair{
		Access: result.AccessToken,
		Refresh: result.RefreshToken,
	}

	api.options.AccessToken = result.AccessToken
	api.options.RefreshToken = result.RefreshToken
	now := time.Now()
	api.options.ExpirationAt = now.Add(
		time.Second*time.Duration(result.ExpiresIn),
	)
	err = api.writeSecret()
	if err != nil {
		return nil, err
	}
	return ret, nil
}

func (api *Client) RefreshTokenIfExpired() error {
	if api.options.RefreshToken == "" {
		return nil
	}

	now := time.Now()
	if now.After(api.options.ExpirationAt) || now.Equal(api.options.ExpirationAt){
		_, err := api.RefreshToken()
		if err != nil {
			return err
		}
	}
	return nil
}

func (api *Client) RefreshToken() (*OauthTokenResponse, error) {
	result := new(OauthTokenResponse)
	request := map[string]string{
		"client_id":     api.options.ClientId,
		"client_secret": api.options.ClientSecret,
		"grant_type":    "refresh_token",
		"refresh_token": api.options.RefreshToken,
		"redirect_uri":  api.options.RedirectUrl,
	}

	err := api.rdoRequest("/oauth2/access_token", requestOptions{
		HttpMethod: http.MethodPost,
		Body:       request,
		Headers:    getHeaders(""),
	}, result)
	if err != nil {
		return nil, err
	}

	api.options.AccessToken = result.AccessToken
	api.options.RefreshToken = result.RefreshToken
	now := time.Now()
	api.options.ExpirationAt = now.Add(
		time.Second*time.Duration(result.ExpiresIn),
	)
	err = api.writeSecret()
	if err != nil {
		return nil, err
	}

	return result, nil
}

func (api *Client) Get(resource string, result interface{}, abs ...bool) error {
	var a bool
	if len(abs) > 0 {
		a = abs[0]
	} 
	return api.doRequest(resource, requestOptions{
		HttpMethod: http.MethodGet,
		Body:       nil,
		Headers:    getHeaders(api.options.AccessToken),
		Abs: a,
	}, result)
}

func (api *Client) Post(resource string, request interface{}, result interface{}) error {
	return api.doRequest(resource, requestOptions{
		HttpMethod: http.MethodPost,
		Body:       request,
		Headers:    getHeaders(api.options.AccessToken),
	}, result)
}

func (api *Client) Patch(resource string, request interface{}, result interface{}) error {
	return api.doRequest(resource, requestOptions{
		HttpMethod: http.MethodPatch,
		Body:       request,
		Headers:    getHeaders(api.options.AccessToken),
	}, result)
}

func getHeaders(token string) map[string]string {
	headers := map[string]string{
		"Accept":        DefaultAccept,
		"Cache-Control": DefaultCacheControl,
		"Content-Type":  DefaultContentType,
	}

	if len(token) > 0 {
		headers["Authorization"] = fmt.Sprintf("Bearer %s", token)
	}

	return headers
}