package auth

import (
	"bytes"
	"context"
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/99designs/keyring"
	"github.com/frenocorp/pop/internal/config"
	"github.com/manifoldco/promptui"
)

type Session struct {
	UID            string `json:"uid"`
	AccessToken    string `json:"access_token"`
	RefreshToken   string `json:"refresh_token"`
	ExpiresAt      int64  `json:"expires_at"`
	TwoFAEnabled   bool   `json:"two_factor_enabled"`
	MailPassphrase string `json:"mail_passphrase,omitempty"`
}

type SessionManager struct {
	configDir   string
	sessionFile string
	keyring     keyring.Keyring
}

func NewSessionManager() (*SessionManager, error) {
	cfg := config.NewConfigManager()
	configDir := cfg.ConfigDir()

	k, err := keyring.Open(keyring.Config{
		ServiceName: "pop-cli",
		FileDir:     filepath.Join(configDir, "keyring"),
	})
	if err != nil {
		return nil, fmt.Errorf("failed to open keyring: %w", err)
	}

	return &SessionManager{
		configDir:   configDir,
		sessionFile: filepath.Join(configDir, "session.json"),
		keyring:     k,
	}, nil
}

func (m *SessionManager) LoginWithCredentials(ctx context.Context, apiBaseURL, email, password, mailPassphrase string) error {
	if err := os.MkdirAll(m.configDir, 0700); err != nil {
		return fmt.Errorf("failed to create config dir: %w", err)
	}

	if err := os.MkdirAll(filepath.Join(m.configDir, "keyring"), 0700); err != nil {
		return fmt.Errorf("failed to create keyring dir: %w", err)
	}

	authURL := fmt.Sprintf("%s/auth", apiBaseURL)
	
	payload := map[string]string{
		"Email":    email,
		"Password": password,
	}

	jsonData, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal auth payload: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", authURL, bytes.NewBuffer(jsonData))
	if err != nil {
		return fmt.Errorf("failed to create auth request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	client := &http.Client{Timeout: 30 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("failed to connect to ProtonMail API: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("authentication failed (status %d): %s", resp.StatusCode, string(body))
	}

	var authResponse struct {
		UID            string `json:"UID"`
		AccessToken    string `json:"AccessToken"`
		RefreshToken   string `json:"RefreshToken"`
		ExpiresIn      int    `json:"ExpiresIn"`
		TwoFARequired  bool   `json:"TwoFARequired"`
	}

	if err := json.NewDecoder(resp.Body).Decode(&authResponse); err != nil {
		return fmt.Errorf("failed to parse auth response: %w", err)
	}

	session := Session{
		UID:            authResponse.UID,
		AccessToken:    authResponse.AccessToken,
		RefreshToken:   authResponse.RefreshToken,
		ExpiresAt:      time.Now().Unix() + int64(authResponse.ExpiresIn),
		TwoFAEnabled:   authResponse.TwoFARequired,
		MailPassphrase: mailPassphrase,
	}

	encryptedForFile, err := encryptSession(session)
	if err != nil {
		return fmt.Errorf("failed to encrypt session: %w", err)
	}

	if err := m.keyring.Set(keyring.Item{
		Key:  "session",
		Data: encryptedForFile,
	}); err != nil {
		return fmt.Errorf("failed to store session in keyring: %w", err)
	}

	if err := os.WriteFile(m.sessionFile, encryptedForFile, 0600); err != nil {
		return fmt.Errorf("failed to write encrypted session file: %w", err)
	}

	fmt.Println("Logged in successfully")
	return nil
}

func (m *SessionManager) LoginInteractive(ctx context.Context, apiBaseURL string) error {
	if err := os.MkdirAll(m.configDir, 0700); err != nil {
		return fmt.Errorf("failed to create config dir: %w", err)
	}

	if err := os.MkdirAll(filepath.Join(m.configDir, "keyring"), 0700); err != nil {
		return fmt.Errorf("failed to create keyring dir: %w", err)
	}

	emailPrompt := promptui.Prompt{
		Label: "ProtonMail email",
		Validate: func(input string) error {
			if !strings.Contains(input, "@") || !strings.Contains(input, ".") {
				return fmt.Errorf("invalid email format")
			}
			parts := strings.Split(input, "@")
			if len(parts) != 2 || len(parts[0]) == 0 || len(parts[1]) < 3 {
				return fmt.Errorf("invalid email format")
			}
			return nil
		},
	}
	email, err := emailPrompt.Run()
	if err != nil {
		return fmt.Errorf("failed to read email: %w", err)
	}

	passwordPrompt := promptui.Prompt{
		Label: "ProtonMail password",
		Mask:  '*',
	}
	password, err := passwordPrompt.Run()
	if err != nil {
		return fmt.Errorf("failed to read password: %w", err)
	}

	passphrasePrompt := promptui.Prompt{
		Label: "Mail passphrase",
		Mask:  '*',
	}
	mailPassphrase, err := passphrasePrompt.Run()
	if err != nil {
		return fmt.Errorf("failed to read mail passphrase: %w", err)
	}

	authURL := fmt.Sprintf("%s/auth", apiBaseURL)
	
	payload := map[string]string{
		"Email":    email,
		"Password": password,
	}

	jsonData, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal auth payload: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", authURL, bytes.NewBuffer(jsonData))
	if err != nil {
		return fmt.Errorf("failed to create auth request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	client := &http.Client{Timeout: 30 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("failed to connect to ProtonMail API: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("authentication failed (status %d): %s", resp.StatusCode, string(body))
	}

	var authResponse struct {
		UID            string `json:"UID"`
		AccessToken    string `json:"AccessToken"`
		RefreshToken   string `json:"RefreshToken"`
		ExpiresIn      int    `json:"ExpiresIn"`
		TwoFARequired  bool   `json:"TwoFARequired"`
		TwoFAChallenge struct {
			Type string `json:"Type"`
		} `json:"TwoFAChallenge"`
	}

	if err := json.NewDecoder(resp.Body).Decode(&authResponse); err != nil {
		return fmt.Errorf("failed to parse auth response: %w", err)
	}

	session := Session{
		UID:            authResponse.UID,
		AccessToken:    authResponse.AccessToken,
		RefreshToken:   authResponse.RefreshToken,
		ExpiresAt:      time.Now().Unix() + int64(authResponse.ExpiresIn),
		TwoFAEnabled:   authResponse.TwoFARequired,
		MailPassphrase: mailPassphrase,
	}

	if session.TwoFAEnabled {
		fmt.Println("\n2FA authentication required")
		
		totpPrompt := promptui.Prompt{
			Label: "Enter TOTP code",
			Validate: func(input string) error {
				if len(input) != 6 {
					return fmt.Errorf("TOTP code must be 6 digits")
				}
				return nil
			},
		}
		totpCode, err := totpPrompt.Run()
		if err != nil {
			return fmt.Errorf("failed to read TOTP code: %w", err)
		}

		totpURL := fmt.Sprintf("%s/auth/verify", apiBaseURL)
		totpPayload := map[string]string{
			"UID":  session.UID,
			"Code": totpCode,
		}
		
		totpJSON, err := json.Marshal(totpPayload)
		if err != nil {
			return fmt.Errorf("failed to marshal TOTP payload: %w", err)
		}

		totpReq, err := http.NewRequestWithContext(ctx, "POST", totpURL, bytes.NewBuffer(totpJSON))
		if err != nil {
			return fmt.Errorf("failed to create TOTP request: %w", err)
		}
		totpReq.Header.Set("Authorization", fmt.Sprintf("Bearer %s", session.AccessToken))
		totpReq.Header.Set("Content-Type", "application/json")

		totpResp, err := client.Do(totpReq)
		if err != nil {
			return fmt.Errorf("failed to verify TOTP: %w", err)
		}
		defer totpResp.Body.Close()

		if totpResp.StatusCode != http.StatusOK {
			body, _ := io.ReadAll(totpResp.Body)
			return fmt.Errorf("TOTP verification failed (status %d): %s", totpResp.StatusCode, string(body))
		}

		var finalAuth struct {
			AccessToken  string `json:"AccessToken"`
			RefreshToken string `json:"RefreshToken"`
			ExpiresIn    int    `json:"ExpiresIn"`
		}

		if err := json.NewDecoder(totpResp.Body).Decode(&finalAuth); err != nil {
			return fmt.Errorf("failed to parse TOTP response: %w", err)
		}

		session.AccessToken = finalAuth.AccessToken
		session.RefreshToken = finalAuth.RefreshToken
		session.ExpiresAt = time.Now().Unix() + int64(finalAuth.ExpiresIn)
	}

	encryptedForFile, err := encryptSession(session)
	if err != nil {
		return fmt.Errorf("failed to encrypt session: %w", err)
	}

	if err := m.keyring.Set(keyring.Item{
		Key:  "session",
		Data: encryptedForFile,
	}); err != nil {
		return fmt.Errorf("failed to store session in keyring: %w", err)
	}

	if err := os.WriteFile(m.sessionFile, encryptedForFile, 0600); err != nil {
		return fmt.Errorf("failed to write encrypted session file: %w", err)
	}

	fmt.Println("Logged in successfully")
	return nil
}

func (m *SessionManager) Logout() error {
	if err := os.Remove(m.sessionFile); err != nil {
		return fmt.Errorf("failed to remove session file: %w", err)
	}

	if err := m.keyring.Remove("session"); err != nil {
		return fmt.Errorf("failed to remove keyring entry: %w", err)
	}

	fmt.Println("Logged out successfully")
	return nil
}

func (m *SessionManager) GetSession() (*Session, error) {
	// First, try to get from keyring (encrypted storage)
	item, err := m.keyring.Get("session")
	if err == nil {
		session, err := decryptSession(item.Data)
		if err != nil {
			return nil, fmt.Errorf("failed to decrypt session from keyring: %w", err)
		}
		return &session, nil
	}

	// If not in keyring, read from encrypted file
	data, err := os.ReadFile(m.sessionFile)
	if err != nil {
		if err == os.ErrNotExist {
			return nil, fmt.Errorf("no session found: %w", err)
		}
		return nil, fmt.Errorf("failed to read session file: %w", err)
	}

	// Decrypt the session data
	session, err := decryptSession(data)
	if err != nil {
		return nil, fmt.Errorf("failed to decrypt session: %w", err)
	}

	return &session, nil
}

func (m *SessionManager) IsAuthenticated() (bool, error) {
	session, err := m.GetSession()
	if err != nil {
		return false, err
	}

	if time.Now().Unix() > session.ExpiresAt {
		return false, fmt.Errorf("session expired at %d", session.ExpiresAt)
	}

	return true, nil
}

func (m *SessionManager) RefreshToken() error {
	return m.RefreshTokenWithContext(context.Background())
}

func (m *SessionManager) RefreshTokenWithContext(ctx context.Context) error {
	session, err := m.GetSession()
	if err != nil {
		return fmt.Errorf("failed to get session: %w", err)
	}

	if session.RefreshToken == "" {
		return fmt.Errorf("no refresh token available")
	}

	apiBaseURL := "https://api.protonmail.ch"
	refreshURL := fmt.Sprintf("%s/auth/refresh", apiBaseURL)

	payload := map[string]string{
		"UID":          session.UID,
		"RefreshToken": session.RefreshToken,
	}

	jsonData, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal refresh payload: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", refreshURL, bytes.NewBuffer(jsonData))
	if err != nil {
		return fmt.Errorf("failed to create refresh request: %w", err)
	}
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", session.AccessToken))
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	client := &http.Client{Timeout: 30 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("failed to connect to ProtonMail API: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("token refresh failed (status %d): %s", resp.StatusCode, string(body))
	}

	var refreshResponse struct {
		AccessToken  string `json:"AccessToken"`
		RefreshToken string `json:"RefreshToken"`
		ExpiresIn    int    `json:"ExpiresIn"`
	}

	if err := json.NewDecoder(resp.Body).Decode(&refreshResponse); err != nil {
		return fmt.Errorf("failed to parse refresh response: %w", err)
	}

	session.AccessToken = refreshResponse.AccessToken
	session.RefreshToken = refreshResponse.RefreshToken
	session.ExpiresAt = time.Now().Unix() + int64(refreshResponse.ExpiresIn)

	encryptedForFile, err := encryptSession(*session)
	if err != nil {
		return fmt.Errorf("failed to encrypt updated session: %w", err)
	}

	if err := m.keyring.Set(keyring.Item{
		Key:  "session",
		Data: encryptedForFile,
	}); err != nil {
		return fmt.Errorf("failed to update session in keyring: %w", err)
	}

	_ = os.WriteFile(m.sessionFile, encryptedForFile, 0600)

	return nil
}

// encryptSession encrypts the session data using AES-256-GCM
func encryptSession(session Session) ([]byte, error) {
	// Generate a random 256-bit key
	key := make([]byte, 32)
	if _, err := rand.Read(key); err != nil {
		return nil, fmt.Errorf("failed to generate encryption key: %w", err)
	}

	// Generate a random 12-byte nonce
	nonce := make([]byte, 12)
	if _, err := rand.Read(nonce); err != nil {
		return nil, fmt.Errorf("failed to generate nonce: %w", err)
	}

	// Create AES-GCM cipher
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, fmt.Errorf("failed to create AES cipher: %w", err)
	}

	aead, err := cipher.NewGCM(block)
	if err != nil {
		return nil, fmt.Errorf("failed to create GCM: %w", err)
	}

	// Encrypt the session data
	sessionData, err := json.Marshal(session)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal session for encryption: %w", err)
	}

	sealedData := aead.Seal(nil, nonce, sessionData, nil)

	// Prepend key and nonce (base64 encoded for readability in file)
	header := fmt.Sprintf("%s|%s|", base64.StdEncoding.EncodeToString(key), base64.StdEncoding.EncodeToString(nonce))
	return []byte(header + string(sealedData)), nil
}

// decryptSession decrypts the session data
func decryptSession(encryptedData []byte) (Session, error) {
	// Split header and encrypted data
	parts := strings.Split(string(encryptedData), "|")
	if len(parts) != 3 {
		return Session{}, fmt.Errorf("invalid encrypted data format")
	}

	// Decode key and nonce
	key, err := base64.StdEncoding.DecodeString(parts[0])
	if err != nil {
		return Session{}, fmt.Errorf("failed to decode key: %w", err)
	}

	nonce, err := base64.StdEncoding.DecodeString(parts[1])
	if err != nil {
		return Session{}, fmt.Errorf("failed to decode nonce: %w", err)
	}

	// Decrypt
	block, err := aes.NewCipher(key)
	if err != nil {
		return Session{}, fmt.Errorf("failed to create AES cipher: %w", err)
	}

	aead, err := cipher.NewGCM(block)
	if err != nil {
		return Session{}, fmt.Errorf("failed to create GCM: %w", err)
	}

	sealedData, err := base64.StdEncoding.DecodeString(parts[2])
	if err != nil {
		return Session{}, fmt.Errorf("failed to decode sealed data: %w", err)
	}

	data, err := aead.Open(nil, nonce, sealedData, nil)
	if err != nil {
		return Session{}, fmt.Errorf("failed to decrypt session: %w", err)
	}

	var session Session
	if err := json.Unmarshal(data, &session); err != nil {
		return Session{}, fmt.Errorf("failed to unmarshal session: %w", err)
	}

	return session, nil
}