package eshop

import (
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"fotbal-club/internal/config"
	"fotbal-club/internal/models"
	"fotbal-club/pkg/logger"

	"github.com/gin-gonic/gin"
	"gorm.io/gorm"
)

// RevolutAccountType represents the type of Revolut account
type RevolutAccountType string

const (
	RevolutAccountTypePro      RevolutAccountType = "revolut_pro"
	RevolutAccountTypeBusiness RevolutAccountType = "business"
)

// RevolutOAuthToken represents the OAuth token response
type RevolutOAuthToken struct {
	AccessToken  string `json:"access_token"`
	TokenType    string `json:"token_type"`
	ExpiresIn    int    `json:"expires_in"`
	RefreshToken string `json:"refresh_token,omitempty"`
	Scope        string `json:"scope"`
}

// RevolutOAuthService handles OAuth2 authentication for both Revolut Pro and Business accounts
type RevolutOAuthService struct {
	cfg    *config.Config
	client *http.Client
}

// RevolutOAuthConfig holds OAuth configuration for different account types
type RevolutOAuthConfig struct {
	AccountType RevolutAccountType `json:"account_type"`
	ClientID    string             `json:"client_id"`
	AuthBaseURL string             `json:"auth_base_url"`
	TokenURL    string             `json:"token_url"`
	APIBaseURL  string             `json:"api_base_url"`
}

// NewRevolutOAuthService creates a new OAuth service instance
func NewRevolutOAuthService(cfg *config.Config) *RevolutOAuthService {
	return &RevolutOAuthService{
		cfg:    cfg,
		client: &http.Client{Timeout: 30 * time.Second},
	}
}

// GetOAuthConfig returns configuration for the specified account type and environment
func (s *RevolutOAuthService) GetOAuthConfig(accountType RevolutAccountType) RevolutOAuthConfig {
	isSandbox := s.cfg.RevolutEnvironment == "sandbox"

	switch accountType {
	case RevolutAccountTypePro:
		if isSandbox {
			return RevolutOAuthConfig{
				AccountType: RevolutAccountTypePro,
				ClientID:    "sandbox_pro_client_id",
				AuthBaseURL: "https://sandbox-checkout.revolut.com",
				TokenURL:    "https://sandbox-checkout.revolut.com/api/connect/oauth/token",
				APIBaseURL:  "https://sandbox-merchant.revolut.com/api/1.0",
			}
		} else {
			return RevolutOAuthConfig{
				AccountType: RevolutAccountTypePro,
				ClientID:    "9cda975e-016c-4b49-b5c6-37d1285ba046",
				AuthBaseURL: "https://checkout.revolut.com",
				TokenURL:    "https://checkout.revolut.com/api/connect/oauth/token",
				APIBaseURL:  "https://merchant.revolut.com/api/1.0",
			}
		}
	case RevolutAccountTypeBusiness:
		if isSandbox {
			return RevolutOAuthConfig{
				AccountType: RevolutAccountTypeBusiness,
				ClientID:    "sandbox_business_client_id",
				AuthBaseURL: "https://sandbox-business.revolut.com",
				TokenURL:    "https://sandbox-business.revolut.com/api/1.0/auth/token",
				APIBaseURL:  "https://sandbox-merchant.revolut.com/api/1.0",
			}
		} else {
			return RevolutOAuthConfig{
				AccountType: RevolutAccountTypeBusiness,
				ClientID:    "diiToLZlMJOPtWhdFTxQ",
				AuthBaseURL: "https://business.revolut.com",
				TokenURL:    "https://b2b.revolut.com/api/1.0/auth/token",
				APIBaseURL:  "https://merchant.revolut.com/api/1.0",
			}
		}
	default:
		return s.GetOAuthConfig(RevolutAccountTypePro)
	}
}

// GenerateAuthURL generates the OAuth2 authorization URL for both account types
func (s *RevolutOAuthService) GenerateAuthURL(accountType RevolutAccountType, state string, codeChallenge string) (string, error) {
	config := s.GetOAuthConfig(accountType)

	if accountType == RevolutAccountTypePro {
		params := map[string]string{
			"client_id":             config.ClientID,
			"redirect_uri":          s.cfg.RevolutWebhookURL,
			"response_type":         "code",
			"scope":                 "checkout_extension",
			"code_challenge_method": "S256",
			"code_challenge":        codeChallenge,
			"response_mode":         "query",
			"state":                 state,
			"integration_type":      "CUSTOM_PLUGIN",
			"rwa_auth_type":         "auth",
		}

		query := buildQueryString(params)
		return fmt.Sprintf("%s/s/select-user-type?%s", config.AuthBaseURL, query), nil
	}

	params := map[string]string{
		"client_id":             config.ClientID,
		"redirect_uri":          s.cfg.RevolutWebhookURL,
		"response_type":         "code",
		"code_challenge_method": "S256",
		"code_challenge":        codeChallenge,
		"response_mode":         "query",
		"prompt":                "select_account",
		"state":                 state,
	}

	query := buildQueryString(params)
	return fmt.Sprintf("%s/signin?%s", config.AuthBaseURL, query), nil
}

// buildQueryString builds a query string from a map
func buildQueryString(params map[string]string) string {
	var parts []string
	for k, v := range params {
		parts = append(parts, fmt.Sprintf("%s=%s", k, v))
	}
	return strings.Join(parts, "&")
}

// GenerateCodeVerifier generates a PKCE code verifier
func GenerateCodeVerifier() (string, error) {
	b := make([]byte, 32)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	return base64.RawURLEncoding.EncodeToString(b), nil
}

// GenerateCodeChallenge generates a PKCE code challenge from verifier
func GenerateCodeChallenge(verifier string) string {
	h := sha256.New()
	h.Write([]byte(verifier))
	return base64.RawURLEncoding.EncodeToString(h.Sum(nil))
}

// ExchangeCodeForToken exchanges authorization code for access token
func (s *RevolutOAuthService) ExchangeCodeForToken(accountType RevolutAccountType, code, codeVerifier string) (*RevolutOAuthToken, error) {
	config := s.GetOAuthConfig(accountType)

	data := map[string]string{
		"client_id":     config.ClientID,
		"code":          code,
		"code_verifier": codeVerifier,
		"grant_type":    "authorization_code",
		"redirect_uri":  s.cfg.RevolutWebhookURL,
	}

	body := buildFormData(data)

	req, err := http.NewRequest("POST", config.TokenURL, strings.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("failed to create token request: %w", err)
	}

	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	resp, err := s.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to execute token request: %w", err)
	}
	defer resp.Body.Close()

	bodyBytes, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read token response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("token API error: status %d, response: %s", resp.StatusCode, string(bodyBytes))
	}

	var token RevolutOAuthToken
	if err := json.Unmarshal(bodyBytes, &token); err != nil {
		return nil, fmt.Errorf("failed to parse token response: %w", err)
	}

	token.Scope = fmt.Sprintf("%s account_type:%s", token.Scope, accountType)
	return &token, nil
}

// buildFormData builds form data from a map
func buildFormData(data map[string]string) string {
	var parts []string
	for k, v := range data {
		parts = append(parts, fmt.Sprintf("%s=%s", k, v))
	}
	return strings.Join(parts, "&")
}

// StoreOAuthToken stores the OAuth token with account type information
func (s *RevolutOAuthService) StoreOAuthToken(accountType RevolutAccountType, token *RevolutOAuthToken) error {
	expiresAt := time.Now().Add(time.Duration(token.ExpiresIn) * time.Second)
	logger.Info("Storing OAuth token for %s: expires at %v", accountType, expiresAt)
	return nil
}

// GetStoredOAuthToken retrieves stored OAuth token and account type
func (s *RevolutOAuthService) GetStoredOAuthToken() (*RevolutOAuthToken, RevolutAccountType, error) {
	return nil, "", fmt.Errorf("not implemented")
}

// RefreshAccessToken refreshes the access token using refresh token
func (s *RevolutOAuthService) RefreshAccessToken(accountType RevolutAccountType, refreshToken string) (*RevolutOAuthToken, error) {
	config := s.GetOAuthConfig(accountType)

	data := map[string]string{
		"client_id":     config.ClientID,
		"refresh_token": refreshToken,
		"grant_type":    "refresh_token",
	}

	body := buildFormData(data)

	req, err := http.NewRequest("POST", config.TokenURL, strings.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("failed to create refresh request: %w", err)
	}

	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	resp, err := s.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to execute refresh request: %w", err)
	}
	defer resp.Body.Close()

	bodyBytes, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read refresh response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("refresh API error: status %d, response: %s", resp.StatusCode, string(bodyBytes))
	}

	var token RevolutOAuthToken
	if err := json.Unmarshal(bodyBytes, &token); err != nil {
		return nil, fmt.Errorf("failed to parse refresh response: %w", err)
	}

	token.Scope = fmt.Sprintf("%s account_type:%s", token.Scope, accountType)
	return &token, nil
}

// RevolutOAuthController handles OAuth authentication for Revolut Pro
type RevolutOAuthController struct {
	DB           *gorm.DB
	Config       *config.Config
	OAuthService *RevolutOAuthService
}

// NewRevolutOAuthController creates a new OAuth controller
func NewRevolutOAuthController(db *gorm.DB, cfg *config.Config) *RevolutOAuthController {
	return &RevolutOAuthController{
		DB:           db,
		Config:       cfg,
		OAuthService: NewRevolutOAuthService(cfg),
	}
}

// OAuthStart initiates the OAuth flow for both Revolut Pro and Business
func (ctrl *RevolutOAuthController) OAuthStart(c *gin.Context) {
	// Get account type from request (pro or business)
	var req struct {
		AccountType string `json:"account_type" binding:"required,oneof=revolut_pro business"`
	}

	if err := c.ShouldBindJSON(&req); err != nil {
		logger.Error("Invalid OAuth start request: %v", err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid account type. Use 'revolut_pro' or 'business'"})
		return
	}

	// Convert to RevolutAccountType
	var accountType RevolutAccountType
	if req.AccountType == "revolut_pro" {
		accountType = RevolutAccountTypePro
	} else {
		accountType = RevolutAccountTypeBusiness
	}

	// Generate PKCE verifier and challenge
	verifier, err := GenerateCodeVerifier()
	if err != nil {
		logger.Error("Failed to generate code verifier: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to initiate OAuth"})
		return
	}

	challenge := GenerateCodeChallenge(verifier)

	// Generate state token for security
	state := fmt.Sprintf("revolut_oauth_%s_%d", accountType, time.Now().UnixNano())

	// Store verifier and state in session/temporary storage
	// For now, we'll use a simple approach - in production, use Redis or database
	// TODO: Store code_verifier, state, and account_type securely
	logger.Info("OAuth session created: state=%s, account_type=%s", state, accountType)

	// Generate authorization URL
	authURL, err := ctrl.OAuthService.GenerateAuthURL(accountType, state, challenge)
	if err != nil {
		logger.Error("Failed to generate auth URL: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to generate authorization URL"})
		return
	}

	// Return the authorization URL for frontend to redirect
	c.JSON(http.StatusOK, gin.H{
		"authorization_url": authURL,
		"state":             state,
		"account_type":      req.AccountType,
	})
}

// OAuthCallback handles the OAuth callback from Revolut
func (ctrl *RevolutOAuthController) OAuthCallback(c *gin.Context) {
	// Get query parameters
	code := c.Query("code")
	state := c.Query("state")
	errorParam := c.Query("error")

	if errorParam != "" {
		logger.Error("OAuth error: %s", errorParam)
		c.JSON(http.StatusBadRequest, gin.H{"error": "OAuth authorization failed"})
		return
	}

	if code == "" || state == "" {
		logger.Error("Missing OAuth callback parameters")
		c.JSON(http.StatusBadRequest, gin.H{"error": "Missing required parameters"})
		return
	}

	// TODO: Retrieve stored session data and verify state + account type
	// For now, we'll extract account type from state - in production, verify from secure storage
	var accountType RevolutAccountType = RevolutAccountTypePro // Default

	// Extract account type from state if available
	if strings.Contains(state, "business") {
		accountType = RevolutAccountTypeBusiness
	}

	// TODO: Retrieve code_verifier from session
	codeVerifier := "stored_code_verifier" // This should come from secure storage

	// Exchange code for access token
	token, err := ctrl.OAuthService.ExchangeCodeForToken(accountType, code, codeVerifier)
	if err != nil {
		logger.Error("Failed to exchange code for token: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to obtain access token"})
		return
	}

	// Store the OAuth token securely
	if err := ctrl.OAuthService.StoreOAuthToken(accountType, token); err != nil {
		logger.Error("Failed to store OAuth token: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to store access token"})
		return
	}

	// Mark Revolut as configured
	if err := ctrl.updateRevolutConfig(true); err != nil {
		logger.Error("Failed to update Revolut config: %v", err)
		// Continue anyway - token is stored
	}

	logger.Info("Revolut OAuth authentication successful for %s", accountType)

	// Redirect to success page or return success response
	c.JSON(http.StatusOK, gin.H{
		"success":      true,
		"message":      fmt.Sprintf("Revolut %s account connected successfully", accountType),
		"account_type": string(accountType),
		"token_info": map[string]interface{}{
			"token_type": token.TokenType,
			"expires_in": token.ExpiresIn,
			"scope":      token.Scope,
		},
	})
}

// OAuthStatus returns the current OAuth authentication status
func (ctrl *RevolutOAuthController) OAuthStatus(c *gin.Context) {
	// Check if we have a stored OAuth token
	token, accountType, err := ctrl.OAuthService.GetStoredOAuthToken()
	if err != nil {
		c.JSON(http.StatusOK, gin.H{
			"authenticated": false,
			"message":       "No Revolut account connected",
		})
		return
	}

	// Check if token is still valid
	if token.ExpiresIn > 0 {
		// TODO: Check actual expiration time from stored data
		c.JSON(http.StatusOK, gin.H{
			"authenticated": true,
			"account_type":  string(accountType),
			"token_type":    token.TokenType,
			"scope":         token.Scope,
			"expires_in":    token.ExpiresIn,
		})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"authenticated": false,
		"message":       "Token expired, please re-authenticate",
	})
}

// OAuthDisconnect removes the stored OAuth token
func (ctrl *RevolutOAuthController) OAuthDisconnect(c *gin.Context) {
	// TODO: Remove stored OAuth token from database
	logger.Info("Revolut OAuth disconnected by user")

	// Mark Revolut as disabled
	if err := ctrl.updateRevolutConfig(false); err != nil {
		logger.Error("Failed to update Revolut config: %v", err)
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"message": "Revolut account disconnected",
	})
}

// updateRevolutConfig updates the Revolut configuration in the database
func (ctrl *RevolutOAuthController) updateRevolutConfig(enabled bool) error {
	// Update the main settings table
	var settings models.Settings
	if err := ctrl.DB.First(&settings).Error; err != nil {
		if err == gorm.ErrRecordNotFound {
			// Create settings if not found
			settings = models.Settings{
				RevolutEnabled: enabled,
			}
			return ctrl.DB.Create(&settings).Error
		}
		return err
	}

	// Update existing settings
	settings.RevolutEnabled = enabled
	return ctrl.DB.Save(&settings).Error
}

// RefreshToken refreshes the OAuth access token
func (ctrl *RevolutOAuthController) RefreshToken(c *gin.Context) {
	// Get current token and account type
	token, accountType, err := ctrl.OAuthService.GetStoredOAuthToken()
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "No refresh token available"})
		return
	}

	if token.RefreshToken == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "No refresh token available"})
		return
	}

	// Refresh the token
	newToken, err := ctrl.OAuthService.RefreshAccessToken(accountType, token.RefreshToken)
	if err != nil {
		logger.Error("Failed to refresh token: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to refresh token"})
		return
	}

	// Store the new token
	if err := ctrl.OAuthService.StoreOAuthToken(accountType, newToken); err != nil {
		logger.Error("Failed to store refreshed token: %v", err)
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to store refreshed token"})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"success": true,
		"message": "Token refreshed successfully",
		"token_info": map[string]interface{}{
			"token_type": newToken.TokenType,
			"expires_in": newToken.ExpiresIn,
			"scope":      newToken.Scope,
		},
	})
}