package main

import (
	"bufio"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"time"
)

type Message struct {
	Message string `json:"message"`
	From    string `json:"from"`
	To      string `json:"to"`
}

// Note: The StreamResponse structure simplified for demonstration. Adjust according to actual requirements.
type StreamResponse struct {
	From      string `json:"from"`
	To        string `json:"to"`
	CreatedAt string `json:"createdAt"`
	Response  string `json:"response"`
}

const linux = "python3"

func createStreamResponse(fromLanguage, toLanguage, message string) string {
	response := StreamResponse{
		From:      fromLanguage,
		To:        toLanguage,
		CreatedAt: time.Now().Format(time.RFC3339),
		Response:  message,
	}
	jsonResp, err := json.Marshal(response)
	if err != nil {
		return `{"response": "Error in preparing the message."}`
	}
	return string(jsonResp)
}

func streamResponse(w http.ResponseWriter, fromLanguage, toLanguage string, messages <-chan string) {
	// Set headers for SSE
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")

	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "Streaming unsupported!", http.StatusInternalServerError)
		return
	}

	for msg := range messages {
		formattedMessage := createStreamResponse(fromLanguage, toLanguage, msg)
		fmt.Fprintf(w, "data: %s\n\n", formattedMessage)
		flusher.Flush() // Ensure client receives the update immediately
	}
}

func downloadPackages(w http.ResponseWriter, fromLanguage, toLanguage string) {

	// Create a channel to send messages from the download process
	messages := make(chan string)
	defer close(messages)

	// Use a goroutine for streaming responses so we can proceed with the download
	go streamResponse(w, fromLanguage, toLanguage, messages)

	// Start the python command in the background
	cmd := exec.Command(linux, "translator/download.py", fromLanguage, toLanguage)
	output, err := cmd.StdoutPipe()
	if err != nil {
		messages <- fmt.Sprintf("Error starting Download: %s", err.Error())
		return
	}

	err = cmd.Start()
	if err != nil {
		messages <- fmt.Sprintf("Error starting Download: %s", err.Error())
		return
	}

	// Initial message sent to the channel for streaming
	messages <- "Download started..."

	// Start a ticker to send "..." every few seconds until we get real output
	ticker := time.NewTicker(2 * time.Second)
	go func() {
		for range ticker.C {
			messages <- ". . ."
		}
	}()

	// Read the output of the python command and send it to the channel
	scanner := bufio.NewScanner(output)
	firstOutputReceived := false
	for scanner.Scan() {
		if !firstOutputReceived {
			// Stop the ticker after receiving the first real output
			ticker.Stop()
			firstOutputReceived = true
		}
		messages <- scanner.Text()
	}

	// Wait for the command to complete
	err = cmd.Wait()
	if err != nil {
		messages <- fmt.Sprintf("Error waiting for Download: %s", err.Error())
		return
	}
}

func executeTranslator(w http.ResponseWriter, message, fromLanguage, toLanguage string) {
	// Create a message channel for streaming translation results
	messages := make(chan string)
	defer close(messages)

	// A goroutine will manage sending streamed responses
	go streamResponse(w, fromLanguage, toLanguage, messages)

	// Start the python command in the background
	cmd := exec.Command(linux, "translator/translate.py", message, fromLanguage, toLanguage)
	output, err := cmd.StdoutPipe()
	if err != nil {
		messages <- fmt.Sprintf("Error starting Translation: %s", err.Error())
		return
	}

	err = cmd.Start()
	if err != nil {
		messages <- fmt.Sprintf("Error starting Translation: %s", err.Error())
		return
	}

	// Read the output of the python command and send it through the channel
	scanner := bufio.NewScanner(output)
	for scanner.Scan() {
		messages <- scanner.Text() // Sends each line of the output to the stream
	}

	// Wait for the command to complete
	err = cmd.Wait()
	if err != nil {
		messages <- fmt.Sprintf("Error waiting for Translation: %s", err.Error())
		return
	}
}

func CheckLanguagesInstalled(fromCode, toCode string) (bool, error) {
	// Construct the target directory path
	homeDir, err := os.UserHomeDir()
	if err != nil {
		return false, fmt.Errorf("unable to determine the user home directory: %w", err)
	}
	targetDir := filepath.Join(homeDir, ".local", "share", "argos-translate", "packages", fromCode+"_"+toCode)

	// Check if the directory exists
	_, err = os.Stat(targetDir)
	if err != nil {
		if os.IsNotExist(err) {
			return false, nil // Directory does not exist, indicating the language pair is not installed
		}
		return false, fmt.Errorf("error checking for language directory: %w", err)
	}

	// The directory exists, indicating the language pair is installed
	return true, nil
}
func handleRequest(w http.ResponseWriter, r *http.Request) {
	// Read the request body
	if r.Header.Get("Content-Type") != "application/json" {
		http.Error(w, "Request content type must be application/json", http.StatusBadRequest)
		return
	}
	body, err := io.ReadAll(r.Body)
	if err != nil {
		http.Error(w, "Error reading request body: "+err.Error(), http.StatusInternalServerError)
		return
	}
	defer r.Body.Close()

	// Unmarshal the JSON data
	var msg Message
	err = json.Unmarshal(body, &msg)
	if err != nil {
		http.Error(w, "Error unmarshalling JSON: "+err.Error(), http.StatusBadRequest)
		return
	}

	// Check if From and To fields are not longer than 2 letters
	if len(msg.From) > 2 || len(msg.To) > 2 {
		http.Error(w, "From and To fields should not be longer than 2 letters.", http.StatusBadRequest)
		return
	} else {
		installed, err := CheckLanguagesInstalled(msg.From, msg.To)
		if err != nil {
			if err.Error() == "file not found" {
				http.Error(w, "file not found "+err.Error(), http.StatusInternalServerError)
			} else {
				fmt.Println("An error occurred:", err)
			}
			return
		}
		if installed {
			executeTranslator(w, msg.Message, msg.From, msg.To)
		} else {
			downloadPackages(w, msg.From, msg.To)
		}
	}
}

func main() {
	// Define the HTTP handler function
	http.HandleFunc("/api", handleRequest)

	// Get the port number from the environment variable or use a default value
	port := "53184"
	if p := os.Getenv("PORT"); p != "" {
		port = p
	}

	// Start the HTTP server
	fmt.Printf("Listening on :%s...\n", port)
	err := http.ListenAndServe(":"+port, nil)
	if err != nil {
		log.Fatalf("Failed to start server: %v", err)
	}
}