package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"strings"
	"os/exec"
	"path/filepath"
	"encoding/base64"

	"golang.org/x/oauth2/google"
	"google.golang.org/api/gmail/v1"
	"google.golang.org/api/option"
)

const CREDENTIALS_DIR = "creds"
const TOKEN_FILE = "token.json"
const CREDENTIALS_FILE = "credentials.json"
const USER = "me"
const EMAILADDR = "downloader.kasernen@gmail.com"

func getEmail(service *gmail.Service, msgID string) *gmail.Message {
	r, err := service.Users.Messages.Get(USER, msgID).Format("FULL").Do()
	if err != nil {
		log.Fatalf("Error when getting mail content: %v", err)
	}
	if r == nil {
		log.Fatalf("Response when getting mail was nil")
	}
	return r
}

func getEmailPlaintext (mail *gmail.Message) (fromAddr string, bodyStr string) {
	part := mail.Payload.Parts[0].Body.Data
	body, err := base64.StdEncoding.DecodeString(part)
	if err != nil {
		log.Fatalf("Error in message body decoding: %v", err)
	}

	for _, header := range mail.Payload.Headers {
		if header.Name == "From" {
			_, addrPart, _ := strings.Cut(header.Value, "<")
			fromAddr, _, _ = strings.Cut(addrPart, ">")
		}
	}

	return fromAddr, string(body)
}

func main() {
	ctx := context.Background()
	creds_file := filepath.Join(CREDENTIALS_DIR, CREDENTIALS_FILE)
	creds_b, err := os.ReadFile(creds_file)
	if err != nil {
		log.Fatalf("Unable to read client secret file: %v", err)
	}

	config, err := google.ConfigFromJSON(creds_b, gmail.GmailModifyScope)
	if err != nil {
		log.Fatalf("Unable to parse client secret file to config: %v", err)
	}
	client := getClient(config)

	service, err := gmail.NewService(ctx, option.WithHTTPClient(client))
	if err != nil {
		log.Fatalf("Unable to retrieve Gmail client: %v", err)
	}

	user := "me"
	r, err := service.Users.Messages.List(user).LabelIds("INBOX").Do()
	if err != nil {
		log.Fatalf("Unable to retrieve messages: %v", err)
	}
	if len(r.Messages) == 0 {
		fmt.Println("No messages found")
		return
	}

	fmt.Println("Messages:")
	for _, msg := range r.Messages {
		fmt.Printf("- %s\n", msg.Id)
		mail := getEmail(service, msg.Id)
		fromAddr, msgBody := getEmailPlaintext(mail)
		fmt.Printf("From: %s\n", fromAddr)
		fmt.Printf("Link: %s", msgBody)

		cmd := exec.Command("yt-dlp", msgBody)
		err = cmd.Run()
		if err != nil {
			log.Fatalf("Video download failed: %v", err)
		}

		var modifications gmail.ModifyMessageRequest
		modifications.AddLabelIds = []string{"Label_6181251506395195727"}
		modifications.RemoveLabelIds = []string{"INBOX"}
		_, err = service.Users.Messages.Modify(USER, msg.Id, &modifications).Do()
		if err != nil {
			log.Fatalf("Unable to move email request from inbox: %v", err)
		}

		var message gmail.Message
		messageStr := fmt.Sprintf(
			"From: %s\r\n" +
			"To: %s\r\n" +
			"Subject: Request received\r\n\r\n" +
			"Message body",
			EMAILADDR,
			fromAddr)
		message.Raw = base64.URLEncoding.EncodeToString([]byte(messageStr))
		_, err = service.Users.Messages.Send(USER, &message).Do()
		if err != nil {
			log.Fatalf("Unable to send email: %v", err)
		}
		fmt.Printf("Download completed, confirmation sent to: %s\n", fromAddr)
		fmt.Println()
	}
}