package handlers

import (
	"encoding/base64"
	"fmt"
	"net/http"
	"time"

	"veza-backend-api/internal/services"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"go.uber.org/zap"
)

// WebAuthnHandler handles FIDO2/WebAuthn passkey endpoints.
// F022: ORIGIN_FEATURES_REGISTRY.md — WebAuthn/Passkeys.
type WebAuthnHandler struct {
	webauthnService *services.WebAuthnService
	logger          *zap.Logger
}

// NewWebAuthnHandler creates a new WebAuthn handler.
func NewWebAuthnHandler(webauthnService *services.WebAuthnService, logger *zap.Logger) *WebAuthnHandler {
	return &WebAuthnHandler{
		webauthnService: webauthnService,
		logger:          logger,
	}
}

// BeginRegistration starts the passkey registration ceremony.
// POST /auth/passkeys/register/begin
func (h *WebAuthnHandler) BeginRegistration(c *gin.Context) {
	userID, exists := c.Get("userID")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "authentication required"})
		return
	}
	uid, ok := userID.(uuid.UUID)
	if !ok {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid user ID"})
		return
	}

	username, _ := c.Get("username")
	usernameStr, _ := username.(string)
	if usernameStr == "" {
		usernameStr = uid.String()
	}

	ctx, cancel := WithTimeout(c.Request.Context(), 5*time.Second)
	defer cancel()

	challenge, options, err := h.webauthnService.BeginRegistration(ctx, uid, usernameStr)
	if err != nil {
		h.logger.Error("WebAuthn begin registration failed", zap.Error(err))
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to begin registration"})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"challenge": challenge.Challenge,
		"options":   options,
	})
}

// FinishRegistrationRequest represents the client's registration response.
type FinishRegistrationRequest struct {
	CredentialID    string `json:"credential_id" binding:"required"`
	PublicKey       string `json:"public_key" binding:"required"`
	AttestationType string `json:"attestation_type"`
	AAGUID          string `json:"aaguid"`
	Name            string `json:"name"`
}

// FinishRegistration completes the passkey registration.
// POST /auth/passkeys/register/finish
func (h *WebAuthnHandler) FinishRegistration(c *gin.Context) {
	userID, exists := c.Get("userID")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "authentication required"})
		return
	}
	uid, ok := userID.(uuid.UUID)
	if !ok {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid user ID"})
		return
	}

	var req FinishRegistrationRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid request body"})
		return
	}

	credentialID, err := decodeBase64URL(req.CredentialID)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid credential_id encoding"})
		return
	}
	publicKey, err := decodeBase64URL(req.PublicKey)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid public_key encoding"})
		return
	}
	var aaguid []byte
	if req.AAGUID != "" {
		aaguid, _ = decodeBase64URL(req.AAGUID)
	}

	attestation := req.AttestationType
	if attestation == "" {
		attestation = "none"
	}

	ctx, cancel := WithTimeout(c.Request.Context(), 5*time.Second)
	defer cancel()

	cred, err := h.webauthnService.FinishRegistration(ctx, uid, credentialID, publicKey, aaguid, attestation, req.Name)
	if err != nil {
		h.logger.Error("WebAuthn finish registration failed", zap.Error(err))
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusCreated, gin.H{
		"credential": cred.ToPublicInfo(),
	})
}

// ListPasskeys returns the user's registered passkeys.
// GET /auth/passkeys
func (h *WebAuthnHandler) ListPasskeys(c *gin.Context) {
	userID, exists := c.Get("userID")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "authentication required"})
		return
	}
	uid, ok := userID.(uuid.UUID)
	if !ok {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid user ID"})
		return
	}

	ctx, cancel := WithTimeout(c.Request.Context(), 5*time.Second)
	defer cancel()

	creds, err := h.webauthnService.GetUserCredentials(ctx, uid)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to list passkeys"})
		return
	}

	result := make([]interface{}, 0, len(creds))
	for _, cr := range creds {
		result = append(result, cr.ToPublicInfo())
	}

	c.JSON(http.StatusOK, gin.H{"passkeys": result})
}

// DeletePasskey removes a registered passkey.
// DELETE /auth/passkeys/:id
func (h *WebAuthnHandler) DeletePasskey(c *gin.Context) {
	userID, exists := c.Get("userID")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "authentication required"})
		return
	}
	uid, ok := userID.(uuid.UUID)
	if !ok {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid user ID"})
		return
	}

	credID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid passkey ID"})
		return
	}

	ctx, cancel := WithTimeout(c.Request.Context(), 5*time.Second)
	defer cancel()

	if err := h.webauthnService.DeleteCredential(ctx, uid, credID); err != nil {
		c.JSON(http.StatusNotFound, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"message": "passkey deleted"})
}

// RenamePasskeyRequest holds the new name for a passkey.
type RenamePasskeyRequest struct {
	Name string `json:"name" binding:"required,max=100"`
}

// RenamePasskey updates the display name of a passkey.
// PUT /auth/passkeys/:id
func (h *WebAuthnHandler) RenamePasskey(c *gin.Context) {
	userID, exists := c.Get("userID")
	if !exists {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "authentication required"})
		return
	}
	uid, ok := userID.(uuid.UUID)
	if !ok {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid user ID"})
		return
	}

	credID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid passkey ID"})
		return
	}

	var req RenamePasskeyRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid request body"})
		return
	}

	ctx, cancel := WithTimeout(c.Request.Context(), 5*time.Second)
	defer cancel()

	if err := h.webauthnService.RenameCredential(ctx, uid, credID, req.Name); err != nil {
		c.JSON(http.StatusNotFound, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"message": "passkey renamed"})
}

// decodeBase64URL decodes a base64url-encoded string (no padding).
func decodeBase64URL(s string) ([]byte, error) {
	b, err := base64.RawURLEncoding.DecodeString(s)
	if err != nil {
		return nil, fmt.Errorf("invalid base64url encoding: %w", err)
	}
	return b, nil
}