tdapi.go

/*
Copyright 2021 Bill Nixon

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package tdapi

import (
	"bufio"
	"bytes"
	"context"
	"crypto/rand"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"net/url"
	"os"
	"strings"

	"golang.org/x/oauth2"
)

const (
	// baseURL     = "https://api.todoist.com"
	// apiBase     = "/rest/v2"
	apiBase     = "https://api.todoist.com/rest/v2"
	authBase    = "https://todoist.com/oauth"
	authURL     = authBase + "/authorize"
	tokenURL    = authBase + "/access_token"
	redirectURL = "https://example.com/redirect"
)

// init sets default logging flags
func init() {
	// log with date, time, file name, and line number
	log.SetFlags(log.Lshortfile)
}

// Get executes the Todoist REST  API call, returning the response body.
// Query parmeters can be included to specify and control the amount of data returned in a response.
// See https://developer.todoist.com/rest/v2/#overview
func (c *TodoistClient) Get(urlString string, query url.Values) (body []byte, err error) {
	// parse the URL string
	// url, err := url.Parse(c.BaseURL + apiBase + urlString)
	url, err := url.Parse(apiBase + urlString)
	if err != nil {
		return body, err
	}

	// add the query parameters to the URL
	url.RawQuery = query.Encode()

	fmt.Println("DEBUG:", url.String())

	// execute the request
	resp, err := c.httpClient.Get(url.String())
	if err != nil {
		return body, err
	}
	defer resp.Body.Close()

	// read the body
	body, err = ioutil.ReadAll(resp.Body)
	if err != nil {
		return body, err
	}

	// check if an error occured and return a APIErrorResponse
	if codeIsError(resp.StatusCode) {
		resError := APIErrorResponse{}

		resError.Err = string(body)

		return nil, &resError
	}

	return body, err
}

// Put executes the Todist REST API call, returning the response body.
//
// Query parmeters can be included to specify and control the amount of data returned in a response.
//
// Exact query parameters varies from one API operation to another.
//
// More information can be found at https://docs.microsoft.com/en-us/graph/query-parameters
func (c *TodoistClient) Put(urlString string, query url.Values, data io.Reader) (body []byte, err error) {
	// parse the URL string
	url, err := url.Parse(apiBase + urlString)
	if err != nil {
		return body, err
	}

	// add the query parameters to the URL
	url.RawQuery = query.Encode()

	// fmt.Println("DEBUG:", url.String())

	req, err := http.NewRequest(http.MethodPut, url.String(), data)
	if err != nil {
		return body, err
	}

	// execute the request
	resp, err := c.httpClient.Do(req)
	if err != nil {
		// handle error
		return body, err
	}
	defer resp.Body.Close()

	// read the body
	body, err = ioutil.ReadAll(resp.Body)
	if err != nil {
		return body, err
	}

	// check if an error occured and return a APIErrorResponse
	if codeIsError(resp.StatusCode) {
		resError := APIErrorResponse{}

		err = json.Unmarshal(body, &resError)
		if err != nil {
			return nil, err
		}

		return nil, &resError
	}

	return body, err
}

// TodoistClient is a client connection to the Todoist REST API. See https://developer.todoist.com/rest/v2/#overview
type TodoistClient struct {
	httpClient *http.Client
	// BaseURL    string
}

// New creates an initialized TodoistClient using the token from tokenFileName.
//
// If tokenFileName doesn't exist, then a token is requested and saved in the file.
//
// The current approach assumes the client runs on a host without a
// browser. The user is instructed to vist a URL to login and authorize the
// client. Once the login is successful, the user must copy the response
// URL and provide to the client program.
//
// The token is requested for offline access, which should include a refresh
// token to allow access for a long period of time.
//
// clientID and clientSecret must be an application registered with the Todoist App Console
func New(tokenFileName string, id string, secret string, scopes []string) *TodoistClient {
	// default Context that is never canceled, has no values, and has no deadline
	ctx := context.Background()

	// scopes = append(scopes, "offline_access")

	// OAuth2 configuration object
	conf := &oauth2.Config{
		ClientID:     id,
		ClientSecret: secret,
		Scopes:       scopes,
		Endpoint: oauth2.Endpoint{
			AuthURL:  authURL,
			TokenURL: tokenURL,
		},
		RedirectURL: redirectURL,
	}

	client := &TodoistClient{}

	// try to get a token from the file
	token, _ := readTokenFromFile(tokenFileName)

	// if token couldn't be retrived, then get a new token
	if token == nil {
		// generate random state to detect Cross-Site Request Forgery
		state := randomBytesBase64(32)

		// get authentication URL for offline access
		authURL := conf.AuthCodeURL(state, oauth2.AccessTypeOffline)

		// instruct the user to vist the authentication URL
		fmt.Println("Visit the following URL in a browser to authenticate this application")
		fmt.Println("After authentication, copy the response URL from the browser")
		fmt.Println(authURL)

		// read the response URL
		fmt.Println("Enter the response URL:")
		responseString, err := bufio.NewReader(os.Stdin).ReadString('\n')
		if err != nil {
			log.Fatal(err)
		}
		responseString = strings.TrimSpace(responseString)

		// parse the response URL
		responseURL, err := url.Parse(responseString)
		if err != nil {
			log.Fatal(err)
		}
		// get and compare state to prevent Cross-Site Request Forgery
		responseState := responseURL.Query().Get("state")
		if responseState != state {
			log.Fatalln("state mismatch, potenial Cross-Site Request Forgery (CSRF)")
		}

		// get authorization code
		code := responseURL.Query().Get("code")

		// exchange authorize code for token
		token, err = conf.Exchange(ctx, code)
		if err != nil {
			log.Fatal(err)
		}

		// save the token to a file
		writeTokenToFile(tokenFileName, token)
	}

	// create HTTP client using the provided token
	client.httpClient = conf.Client(ctx, token)
	// client.BaseURL = baseURL

	return client
}

// randomBytesBase64 returns n bytes encoded in URL friendly base64.
func randomBytesBase64(n int) string {
	// buffer to store n bytes
	b := make([]byte, n)

	// get b random bytes
	_, err := rand.Read(b)
	if err != nil {
		log.Fatal(err)
	}

	// convert to URL friendly base64
	return base64.URLEncoding.EncodeToString(b)
}

// readTokenFromFile reads the json encoded token from a file.
func readTokenFromFile(filename string) (*oauth2.Token, error) {
	// open file
	file, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	// read json encoded token
	token := &oauth2.Token{}
	err = json.NewDecoder(file).Decode(token)

	return token, err
}

// writeTokenToFile writes a josn encoded token to a file.
//
// If file already exists, it is replaced.
func writeTokenToFile(fileName string, token *oauth2.Token) {
	// create file
	file, err := os.Create(fileName)
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	// write access token string
	json.NewEncoder(file).Encode(token)

	return
}

func PrettyPrintJson(src []byte) {
	var out bytes.Buffer
	json.Indent(&out, src, "", " ")
	fmt.Println("=== BEGIN ===")
	fmt.Println(out.String())
	fmt.Println("=== END ===")
}

// VarToJsonString converts any varaible (interface{}) to an indented JSON string.
//
// Only public (capitalized) fields will be visible.
func VarToJsonString(v interface{}) string {
	var buffer bytes.Buffer

	// using Encoder rather than MarshalIndent to not escape HTML
	encoder := json.NewEncoder(&buffer)
	encoder.SetEscapeHTML(false)
	encoder.SetIndent("", "  ")

	err := encoder.Encode(v)
	if err != nil {
		return "ERROR"
	}

	return string(buffer.Bytes())
}

// WriteContent writes the []byte content to a file
func WriteContentToFile(content []byte, fileName string) (err error) {
	// create file
	var file *os.File
	file, err = os.Create(fileName)
	if err != nil {
		return err
	}
	defer file.Close()

	// write content
	_, err = file.Write(content)
	if err != nil {
		return err
	}

	return nil
}