package v1

import (
	"net/http"

	"github.com/gin-gonic/gin"

	"github.com/gochat/gochat/internal/auth"
	"github.com/gochat/gochat/pkg/response"
)

// Reference: P2E §1.5 — MFA HTTP handlers
// Maps to Chatwoot enterprise TwoFactorAuthController:
// - enable → POST /api/v1/auth/mfa/enable (generates secret + QR URI)
// - verify → POST /api/v1/auth/mfa/verify (validates TOTP code, enables MFA)
// - disable → POST /api/v1/auth/mfa/disable (disables MFA after code verification)

// MFAHandler handles MFA (TOTP) HTTP endpoints.
type MFAHandler struct {
	mfaService *auth.MFAService
}

// NewMFAHandler creates a MFA handler with service dependency.
func NewMFAHandler(mfaService *auth.MFAService) *MFAHandler {
	return &MFAHandler{
		mfaService: mfaService,
	}
}

// --- Request/Response structs ---

// EnableMFARequest is the JSON body for MFA enablement initiation.
type EnableMFARequest struct {
	// No body required — user_id comes from auth context
}

// EnableMFAResponse is the JSON response for MFA enablement initiation.
type EnableMFAResponse struct {
	TOTPSecret string `json:"totp_secret"` // base32 secret for manual entry
	QRURI      string `json:"qr_uri"`      // otpauth:// URI for QR code generation
	Message    string `json:"message"`
}

// VerifyMFARequest is the JSON body for MFA TOTP verification.
type VerifyMFARequest struct {
	TOTPSecret string `json:"totp_secret" binding:"required"` // secret from enable step
	TOTPCode   string `json:"totp_code" binding:"required"`   // 6-digit code from authenticator app
}

// DisableMFARequest is the JSON body for MFA disablement.
type DisableMFARequest struct {
	TOTPCode string `json:"totp_code" binding:"required"` // current TOTP code for verification
}

// --- Handlers ---

// EnableMFA initiates MFA setup: generates a TOTP secret and QR URI.
// POST /api/v1/auth/mfa/enable
// Requires authentication — uses user_id from JWT context.
// The user must verify a TOTP code before MFA is actually activated.
func (h *MFAHandler) EnableMFA(c *gin.Context) {
	userID := c.GetUint("user_id")
	if userID == 0 {
		response.AbortWithStatusError(c, http.StatusUnauthorized, response.ErrUnauthorized, "Authentication required")
		return
	}

	// Check if MFA is already enabled
	enabled, err := h.mfaService.IsMFAEnabled(userID)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusUnprocessableEntity, response.ErrInternal, err.Error())
		return
	}
	if enabled {
		response.AbortWithStatusError(c, http.StatusConflict, response.ErrConflict, "MFA is already enabled for this user")
		return
	}

	// Generate new TOTP secret + QR URI
	secret, qrURI, err := h.mfaService.GenerateTOTPSecret(userID)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusUnprocessableEntity, response.ErrInternal, err.Error())
		return
	}

	response.OK(c, EnableMFAResponse{
		TOTPSecret: secret,
		QRURI:      qrURI,
		Message:    "Scan QR code with your authenticator app, then verify with a TOTP code",
	})
}

// VerifyMFA completes MFA setup: verifies TOTP code and enables MFA on the user.
// POST /api/v1/auth/mfa/verify
// Requires authentication — uses user_id from JWT context.
// This is the second step: user provides secret + code from authenticator app.
func (h *MFAHandler) VerifyMFA(c *gin.Context) {
	userID := c.GetUint("user_id")
	if userID == 0 {
		response.AbortWithStatusError(c, http.StatusUnauthorized, response.ErrUnauthorized, "Authentication required")
		return
	}

	var req VerifyMFARequest
	if err := c.ShouldBindJSON(&req); err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrValidation, err.Error())
		return
	}

	// Validate the TOTP code against the provided secret
	cfg := auth.DefaultTOTPConfig()
	if !auth.ValidateTOTPCode(req.TOTPSecret, req.TOTPCode, cfg) {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "Invalid TOTP code, please try again")
		return
	}

	// Enable TOTP on the user (stores secret in DB)
	if err := h.mfaService.EnableTOTP(userID, req.TOTPSecret); err != nil {
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, err.Error())
		return
	}

	response.OK(c, gin.H{
		"message":     "MFA enabled successfully",
		"mfa_enabled": true,
	})
}

// DisableMFA disables MFA after verifying the current TOTP code.
// POST /api/v1/auth/mfa/disable
// Requires authentication — uses user_id from JWT context.
func (h *MFAHandler) DisableMFA(c *gin.Context) {
	userID := c.GetUint("user_id")
	if userID == 0 {
		response.AbortWithStatusError(c, http.StatusUnauthorized, response.ErrUnauthorized, "Authentication required")
		return
	}

	var req DisableMFARequest
	if err := c.ShouldBindJSON(&req); err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrValidation, err.Error())
		return
	}

	// Disable TOTP (requires valid current code for security)
	if err := h.mfaService.DisableTOTP(userID, req.TOTPCode); err != nil {
		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, err.Error())
		return
	}

	response.OK(c, gin.H{
		"message":     "MFA disabled successfully",
		"mfa_enabled": false,
	})
}

// MFAStatus returns the current MFA status for the authenticated user.
// GET /api/v1/auth/mfa/status
func (h *MFAHandler) MFAStatus(c *gin.Context) {
	userID := c.GetUint("user_id")
	if userID == 0 {
		response.AbortWithStatusError(c, http.StatusUnauthorized, response.ErrUnauthorized, "Authentication required")
		return
	}

	enabled, err := h.mfaService.IsMFAEnabled(userID)
	if err != nil {
		response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal, err.Error())
		return
	}

	response.OK(c, gin.H{
		"mfa_enabled": enabled,
	})
}

// RegisterMFARoutes sets up MFA routes on a Gin router group.
// These routes require authentication (AuthRequired middleware).
func RegisterMFARoutes(rg *gin.RouterGroup, handler *MFAHandler) {
	mfaGroup := rg.Group("/auth/mfa")
	{
		mfaGroup.POST("/enable", handler.EnableMFA)
		mfaGroup.POST("/verify", handler.VerifyMFA)
		mfaGroup.POST("/disable", handler.DisableMFA)
		mfaGroup.GET("/status", handler.MFAStatus)
		mfaGroup.POST("/backup_codes", handler.BackupCodes)
	}
}

// BackupCodes generates one-time MFA backup codes.
// POST /api/v1/profile/mfa/backup_codes or /api/v1/auth/mfa/backup_codes
// Reference: Chatwoot MfaController#backup_codes
func (h *MFAHandler) BackupCodes(c *gin.Context) {
	userID := getUserID(c)
	if userID == 0 {
		c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "user not authenticated"})
		return
	}
	codes, err := h.mfaService.GenerateBackupCodes(userID)
	if err != nil {
		c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
		return
	}
	c.JSON(http.StatusOK, gin.H{"backup_codes": codes})
}