package handlers

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"

	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"

	"git.threesix.ai/jordan/slate-v3-1770514618/pkg/auth"
	"git.threesix.ai/jordan/slate-v3-1770514618/pkg/httperror"
	"git.threesix.ai/jordan/slate-v3-1770514618/pkg/httpresponse"
	"git.threesix.ai/jordan/slate-v3-1770514618/services/preferences-api/internal/domain"
	"git.threesix.ai/jordan/slate-v3-1770514618/services/preferences-api/internal/service"
)

// Preferences handles HTTP requests for user preferences.
type Preferences struct {
	svc *service.PreferencesService
}

// NewPreferences creates a new Preferences handler.
func NewPreferences(svc *service.PreferencesService) *Preferences {
	return &Preferences{svc: svc}
}

// UpdatePreferencesRequest is the request body for updating preferences.
type UpdatePreferencesRequest struct {
	Preferences *PreferencesPayload `json:"preferences" validate:"required"`
}

// PreferencesPayload represents the preferences object in the request.
type PreferencesPayload struct {
	Theme         *string                      `json:"theme,omitempty"`
	Language      *string                      `json:"language,omitempty"`
	Notifications *NotificationSettingsPayload `json:"notifications,omitempty"`
}

// NotificationSettingsPayload represents notification settings in the request.
type NotificationSettingsPayload struct {
	Email  *bool   `json:"email,omitempty"`
	Push   *bool   `json:"push,omitempty"`
	Digest *string `json:"digest,omitempty"`
}

// PreferencesResponse is the response for preferences.
type PreferencesResponse struct {
	UserID      string                      `json:"user_id"`
	Preferences PreferencesDataResponse     `json:"preferences"`
	UpdatedAt   string                      `json:"updated_at"`
}

// PreferencesDataResponse holds the preference values in the response.
type PreferencesDataResponse struct {
	Theme         string                        `json:"theme"`
	Language      string                        `json:"language"`
	Notifications NotificationSettingsResponse  `json:"notifications"`
}

// NotificationSettingsResponse holds notification settings in the response.
type NotificationSettingsResponse struct {
	Email  bool   `json:"email"`
	Push   bool   `json:"push"`
	Digest string `json:"digest"`
}

func toPreferencesResponse(p *domain.Preferences) PreferencesResponse {
	return PreferencesResponse{
		UserID: p.UserID.String(),
		Preferences: PreferencesDataResponse{
			Theme:    p.Theme,
			Language: p.Language,
			Notifications: NotificationSettingsResponse{
				Email:  p.Notifications.Email,
				Push:   p.Notifications.Push,
				Digest: p.Notifications.Digest,
			},
		},
		UpdatedAt: p.UpdatedAt.Format("2006-01-02T15:04:05Z"),
	}
}

// Get returns preferences for a user.
func (h *Preferences) Get(w http.ResponseWriter, r *http.Request) error {
	userID := chi.URLParam(r, "user_id")
	if _, err := uuid.Parse(userID); err != nil {
		return httperror.BadRequest("invalid user_id format")
	}

	if err := authorizeAccess(r, userID); err != nil {
		return err
	}

	prefs, err := h.svc.Get(r.Context(), domain.UserID(userID))
	if err != nil {
		return mapDomainError(err)
	}

	httpresponse.OK(w, r, toPreferencesResponse(prefs))
	return nil
}

// Update creates or updates preferences for a user.
func (h *Preferences) Update(w http.ResponseWriter, r *http.Request) error {
	userID := chi.URLParam(r, "user_id")
	if _, err := uuid.Parse(userID); err != nil {
		return httperror.BadRequest("invalid user_id format")
	}

	if err := authorizeAccess(r, userID); err != nil {
		return err
	}

	// Decode to raw map for manual key validation
	var raw map[string]json.RawMessage
	if err := httpresponse.DecodeJSON(r, &raw); err != nil {
		if errors.Is(err, httpresponse.ErrEmptyBody) {
			return httperror.BadRequest("request body is required")
		}
		return httperror.BadRequest("invalid request body")
	}

	prefsRaw, ok := raw["preferences"]
	if !ok || string(prefsRaw) == "null" {
		return httperror.BadRequest("preferences field is required")
	}

	// Check for unknown top-level keys in request body
	for key := range raw {
		if key != "preferences" {
			return httperror.BadRequest(fmt.Sprintf("unknown field: %s", key))
		}
	}

	// Parse preferences object and check for unknown keys
	var prefsMap map[string]json.RawMessage
	if err := json.Unmarshal(prefsRaw, &prefsMap); err != nil {
		return httperror.BadRequest("preferences must be a JSON object")
	}

	allowedKeys := map[string]bool{"theme": true, "language": true, "notifications": true}
	for key := range prefsMap {
		if !allowedKeys[key] {
			return httperror.BadRequest(fmt.Sprintf("unknown preference key: %s", key))
		}
	}

	// Parse the preferences payload
	var payload PreferencesPayload
	if err := json.Unmarshal(prefsRaw, &payload); err != nil {
		return httperror.BadRequest("invalid preferences format")
	}

	update := toDomainUpdate(&payload)

	prefs, err := h.svc.Upsert(r.Context(), domain.UserID(userID), update)
	if err != nil {
		return mapDomainError(err)
	}

	httpresponse.OK(w, r, toPreferencesResponse(prefs))
	return nil
}

func toDomainUpdate(p *PreferencesPayload) *domain.PreferencesUpdate {
	update := &domain.PreferencesUpdate{
		Theme:    p.Theme,
		Language: p.Language,
	}
	if p.Notifications != nil {
		update.Notifications = &domain.NotificationSettingsUpdate{
			Email:  p.Notifications.Email,
			Push:   p.Notifications.Push,
			Digest: p.Notifications.Digest,
		}
	}
	return update
}

// authorizeAccess checks that the authenticated user can access the given user_id.
func authorizeAccess(r *http.Request, targetUserID string) error {
	user := auth.GetUser(r.Context())
	if user == nil {
		// No auth context — when auth is disabled, allow access
		return nil
	}
	if user.ID == targetUserID || user.HasRole("admin") {
		return nil
	}
	return httperror.Forbidden("access denied")
}

func mapDomainError(err error) error {
	switch {
	case errors.Is(err, domain.ErrPreferencesNotFound):
		return httperror.NotFound("preferences not found")
	case errors.Is(err, domain.ErrInvalidTheme):
		return httperror.BadRequest("invalid theme: must be one of light, dark, system")
	case errors.Is(err, domain.ErrInvalidLanguage):
		return httperror.BadRequest("invalid language: must be a 2-letter lowercase ISO 639-1 code")
	case errors.Is(err, domain.ErrInvalidDigest):
		return httperror.BadRequest("invalid digest: must be one of daily, weekly, never")
	case errors.Is(err, domain.ErrInvalidPreferences):
		return httperror.BadRequest("invalid preferences")
	default:
		return err
	}
}