package http

import (
	"errors"
	"strconv"
	"strings"
	"time"

	"github.com/gofiber/fiber/v3"

	appu "knowfoolery/backend/services/user-service/internal/application/user"
	domain "knowfoolery/backend/services/user-service/internal/domain/user"
	sharederrors "knowfoolery/backend/shared/domain/errors"
	"knowfoolery/backend/shared/infra/auth/zitadel"
	"knowfoolery/backend/shared/infra/observability/logging"
	sharedmetrics "knowfoolery/backend/shared/infra/observability/metrics"
	"knowfoolery/backend/shared/infra/utils/httputil"
	"knowfoolery/backend/shared/infra/utils/validation"
)

// Handler implements user service HTTP endpoint handlers.
type Handler struct {
	service           *appu.Service
	validator         *validation.Validator
	logger            *logging.Logger
	metrics           *sharedmetrics.Metrics
	adminDefaultLimit int
	adminMaxLimit     int
}

// NewHandler creates a new HTTP handler set.
func NewHandler(
	service *appu.Service,
	validator *validation.Validator,
	logger *logging.Logger,
	metrics *sharedmetrics.Metrics,
	adminDefaultLimit int,
	adminMaxLimit int,
) *Handler {
	if adminDefaultLimit <= 0 {
		adminDefaultLimit = 50
	}
	if adminMaxLimit <= 0 {
		adminMaxLimit = 200
	}
	return &Handler{
		service:           service,
		validator:         validator,
		logger:            logger,
		metrics:           metrics,
		adminDefaultLimit: adminDefaultLimit,
		adminMaxLimit:     adminMaxLimit,
	}
}

// RegisterUser handles POST /users/register.
func (h *Handler) RegisterUser(c fiber.Ctx) error {
	var req RegisterUserRequest
	if err := c.Bind().Body(&req); err != nil {
		return httputil.SendError(c, sharederrors.Wrap(sharederrors.CodeInvalidInput, "invalid request body", err))
	}
	if err := h.validator.Validate(req); err != nil {
		return httputil.SendError(c, err)
	}

	claims := authClaimsFromContext(c)
	if claims.UserID == "" || claims.Email == "" {
		return httputil.SendError(c, domain.ErrUnauthorized)
	}

	u, err := h.service.Register(c.Context(), appu.RegisterInput{
		ActorZitadelUserID: claims.UserID,
		ActorEmail:         claims.Email,
		DisplayName:        req.DisplayName,
		ConsentVersion:     req.ConsentVersion,
		ConsentSource:      req.ConsentSource,
	})
	if err != nil {
		return h.sendMappedError(c, err)
	}
	h.recordRequestMetric("POST", "/users/register", fiber.StatusOK)
	return httputil.OK(c, toUserResponse(u))
}

// GetUser handles GET /users/:id.
func (h *Handler) GetUser(c fiber.Ctx) error {
	id := c.Params("id")
	claims := authClaimsFromContext(c)
	if !isSelfOrAdmin(claims, id) {
		return httputil.SendError(c, domain.ErrForbidden)
	}

	u, err := h.service.GetProfile(c.Context(), id)
	if err != nil {
		return h.sendMappedError(c, err)
	}
	h.recordRequestMetric("GET", "/users/{id}", fiber.StatusOK)
	return httputil.OK(c, toUserResponse(u))
}

// UpdateUser handles PUT /users/:id.
func (h *Handler) UpdateUser(c fiber.Ctx) error {
	id := c.Params("id")
	claims := authClaimsFromContext(c)
	if !isSelfOrAdmin(claims, id) {
		return httputil.SendError(c, domain.ErrForbidden)
	}

	var req UpdateUserRequest
	if err := c.Bind().Body(&req); err != nil {
		return httputil.SendError(c, sharederrors.Wrap(sharederrors.CodeInvalidInput, "invalid request body", err))
	}
	if err := h.validator.Validate(req); err != nil {
		return httputil.SendError(c, err)
	}

	u, err := h.service.UpdateProfile(c.Context(), id, appu.UpdateProfileInput{
		DisplayName:    req.DisplayName,
		ConsentVersion: req.ConsentVersion,
		ConsentSource:  req.ConsentSource,
	})
	if err != nil {
		return h.sendMappedError(c, err)
	}
	h.recordRequestMetric("PUT", "/users/{id}", fiber.StatusOK)
	return httputil.OK(c, toUserResponse(u))
}

// DeleteUser handles DELETE /users/:id.
func (h *Handler) DeleteUser(c fiber.Ctx) error {
	id := c.Params("id")
	claims := authClaimsFromContext(c)
	if !isSelfOrAdmin(claims, id) {
		return httputil.SendError(c, domain.ErrForbidden)
	}

	if err := h.service.DeleteUser(c.Context(), id, claims.UserID); err != nil {
		return h.sendMappedError(c, err)
	}
	h.recordRequestMetric("DELETE", "/users/{id}", fiber.StatusNoContent)
	return httputil.NoContent(c)
}

// VerifyEmail handles POST /users/verify-email.
func (h *Handler) VerifyEmail(c fiber.Ctx) error {
	claims := authClaimsFromContext(c)
	if claims.UserID == "" {
		return httputil.SendError(c, domain.ErrUnauthorized)
	}

	u, err := h.service.VerifyEmail(c.Context(), claims.UserID)
	if err != nil {
		return h.sendMappedError(c, err)
	}
	h.recordRequestMetric("POST", "/users/verify-email", fiber.StatusOK)
	return httputil.OK(c, toUserResponse(u))
}

// AdminListUsers handles GET /admin/users.
func (h *Handler) AdminListUsers(c fiber.Ctx) error {
	claims := authClaimsFromContext(c)
	if !claims.IsAdmin {
		return httputil.SendError(c, domain.ErrForbidden)
	}

	page := atoiWithDefault(c.Query("page"), 1)
	pageSize := atoiWithDefault(c.Query("page_size"), h.adminDefaultLimit)
	if pageSize > h.adminMaxLimit {
		pageSize = h.adminMaxLimit
	}
	if pageSize < 1 {
		pageSize = h.adminDefaultLimit
	}

	createdAfter, err := parseTimeQuery(c.Query("created_after"))
	if err != nil {
		return httputil.SendError(
			c,
			sharederrors.Wrap(
				sharederrors.CodeValidationFailed,
				"created_after must be RFC3339",
				err,
			),
		)
	}
	createdBefore, err := parseTimeQuery(c.Query("created_before"))
	if err != nil {
		return httputil.SendError(
			c,
			sharederrors.Wrap(
				sharederrors.CodeValidationFailed,
				"created_before must be RFC3339",
				err,
			),
		)
	}

	users, total, normalized, err := h.service.AdminListUsers(c.Context(), appu.ListUsersInput{
		Page:           page,
		PageSize:       pageSize,
		Email:          c.Query("email"),
		DisplayName:    c.Query("display_name"),
		CreatedAfter:   createdAfter,
		CreatedBefore:  createdBefore,
		IncludeDeleted: strings.EqualFold(c.Query("include_deleted"), "true"),
	})
	if err != nil {
		return h.sendMappedError(c, err)
	}

	resp := make([]UserResponse, 0, len(users))
	for _, u := range users {
		resp = append(resp, toUserResponse(u))
	}

	h.recordRequestMetric("GET", "/admin/users", fiber.StatusOK)
	return httputil.Paginated(c, resp, normalized.Page, normalized.PageSize, total)
}

// AdminExportUser handles POST /admin/users/:id/export.
func (h *Handler) AdminExportUser(c fiber.Ctx) error {
	claims := authClaimsFromContext(c)
	if !claims.IsAdmin {
		return httputil.SendError(c, domain.ErrForbidden)
	}

	bundle, err := h.service.AdminExportUser(c.Context(), c.Params("id"), claims.UserID)
	if err != nil {
		return h.sendMappedError(c, err)
	}
	h.recordRequestMetric("POST", "/admin/users/{id}/export", fiber.StatusOK)
	return httputil.OK(c, bundle)
}

func (h *Handler) sendMappedError(c fiber.Ctx, err error) error {
	var domainErr *sharederrors.DomainError
	if errors.As(err, &domainErr) {
		return httputil.SendError(c, domainErr)
	}
	if h.logger != nil {
		h.logger.WithError(err).Error("user-service internal error")
	}
	return httputil.SendError(c, sharederrors.Wrap(sharederrors.CodeInternal, "internal error", err))
}

func (h *Handler) recordRequestMetric(method, endpoint string, status int) {
	if h.metrics == nil {
		return
	}
	h.metrics.HTTPRequestsTotal.WithLabelValues(method, endpoint, strconv.Itoa(status), "user-service").Inc()
}

type authClaims struct {
	UserID        string
	Email         string
	Roles         []string
	EmailVerified bool
	IsAdmin       bool
}

func authClaimsFromContext(c fiber.Ctx) authClaims {
	roles := zitadel.GetUserRoles(c)
	claims := authClaims{
		UserID:        zitadel.GetUserID(c),
		Email:         zitadel.GetUserEmail(c),
		Roles:         roles,
		EmailVerified: claimBool(c.Locals("email_verified")),
	}
	for _, role := range roles {
		if role == "admin" {
			claims.IsAdmin = true
			break
		}
	}
	return claims
}

func isSelfOrAdmin(claims authClaims, userID string) bool {
	if claims.UserID == "" {
		return false
	}
	if claims.IsAdmin {
		return true
	}
	return claims.UserID == userID
}

func claimBool(v interface{}) bool {
	if b, ok := v.(bool); ok {
		return b
	}
	return false
}

func atoiWithDefault(v string, d int) int {
	if strings.TrimSpace(v) == "" {
		return d
	}
	n, err := strconv.Atoi(v)
	if err != nil {
		return d
	}
	return n
}

func parseTimeQuery(v string) (*time.Time, error) {
	if strings.TrimSpace(v) == "" {
		return nil, nil
	}
	t, err := time.Parse(time.RFC3339, v)
	if err != nil {
		return nil, err
	}
	return &t, nil
}