package main

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

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

const linux = "python3"

func streamResponse(w http.ResponseWriter, messages <-chan string) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	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 {
		fmt.Fprintf(w, "%s\n", msg)
		flusher.Flush()
	}
}

func downloadPackages(w http.ResponseWriter, fromLanguage, toLanguage string) {
	messages := make(chan string)
	defer close(messages)

	go streamResponse(w, messages)

	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
	}

	messages <- "Download started..."

	ticker := time.NewTicker(2 * time.Second)
	go func() {
		for range ticker.C {
			messages <- ". . ."
		}
	}()

	scanner := bufio.NewScanner(output)
	firstOutputReceived := false
	for scanner.Scan() {
		if !firstOutputReceived {
			ticker.Stop()
			firstOutputReceived = true
		}
		messages <- scanner.Text()
	}

	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) {
	messages := make(chan string)
	defer close(messages)

	go streamResponse(w, messages)

	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
	}

	scanner := bufio.NewScanner(output)
	for scanner.Scan() {
		// Directly send the translated text as a message
		messages <- scanner.Text()
	}

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

func CheckLanguagesInstalled(fromCode, toCode string) (bool, error) {
	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)

	_, err = os.Stat(targetDir)
	if err != nil {
		if os.IsNotExist(err) {
			return false, nil
		}
		return false, fmt.Errorf("error checking for language directory: %w", err)
	}

	return true, nil
}

func handleRequest(w http.ResponseWriter, r *http.Request) {
	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(io.NopCloser(io.Reader(r.Body)))
	if err != nil {
		http.Error(w, "Error reading request body: "+err.Error(), http.StatusInternalServerError)
		return
	}
	defer r.Body.Close()

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

	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
	}

	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
	}

	var wg sync.WaitGroup
	wg.Add(1)

	go func() {
		defer wg.Done()
		if installed {
			executeTranslator(w, msg.Message, msg.From, msg.To)
		} else {
			downloadPackages(w, msg.From, msg.To)
		}
	}()

	wg.Wait()
}

func main() {
	http.HandleFunc("/", handleRequest)

	port := "53184"
	address := fmt.Sprintf("0.0.0.0:%s", port)

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