package server

import (
	"context"

	"github.com/google/uuid"
	"go.uber.org/zap"

	"scrabble/backend/internal/account"
	"scrabble/backend/internal/ads"
	"scrabble/backend/internal/notify"
)

// bannerDTO is the advertising-banner block attached to an eligible viewer's
// profile: the campaigns to rotate (each already resolved to the viewer's bot
// language) and the global display timings the client rotator reads. It is
// absent for a viewer who should see no banner.
type bannerDTO struct {
	Campaigns []bannerCampaignDTO `json:"campaigns"`
	Timings   bannerTimingsDTO    `json:"timings"`
}

// bannerCampaignDTO is one campaign in the rotation feed: its GCD-reduced show
// weight (for the client's smooth weighted round-robin) and its messages, in
// display order, already resolved to one language.
type bannerCampaignDTO struct {
	Weight   int      `json:"weight"`
	Messages []string `json:"messages"`
}

// bannerTimingsDTO mirrors ads.Timings on the wire.
type bannerTimingsDTO struct {
	HoldMs         int `json:"hold_ms"`
	EdgePauseMs    int `json:"edge_pause_ms"`
	ScrollPxPerSec int `json:"scroll_px_per_sec"`
	FadeOutMs      int `json:"fade_out_ms"`
	GapMs          int `json:"gap_ms"`
	FadeInMs       int `json:"fade_in_ms"`
}

// profileResponse builds the account's profile DTO with the advertising-banner block attached when
// the viewer is eligible. Every endpoint returning the caller's own profile (get, update, link)
// uses it, so the banner never drops off the client's profile after a non-get profile change (e.g.
// a language switch).
func (s *Server) profileResponse(ctx context.Context, acc account.Account) profileResponse {
	r := profileResponseFor(acc)
	r.Banner = s.bannerFor(ctx, acc)
	return r
}

// bannerFor builds the advertising-banner block for the account's profile, or
// nil when the ads service is not configured or the viewer is not eligible to
// see a banner. The message language follows the account's bot (service)
// language, falling back to its interface language and then English. A failure
// reading roles or campaigns is logged and treated as "no banner" so the profile
// response still succeeds.
func (s *Server) bannerFor(ctx context.Context, acc account.Account) *bannerDTO {
	if s.ads == nil {
		return nil
	}
	hasNoBanner, err := s.accounts.HasRole(ctx, acc.ID, account.RoleNoBanner)
	if err != nil {
		s.log.Warn("banner: role check failed", zap.String("account", acc.ID.String()), zap.Error(err))
		return nil
	}
	if !ads.Eligible(acc.PaidAccount, acc.HintBalance, hasNoBanner) {
		return nil
	}
	set, timings, err := s.ads.ActiveSet(ctx, bannerLang(acc))
	if err != nil {
		s.log.Warn("banner: active set failed", zap.String("account", acc.ID.String()), zap.Error(err))
		return nil
	}
	campaigns := make([]bannerCampaignDTO, 0, len(set))
	for _, c := range set {
		campaigns = append(campaigns, bannerCampaignDTO{Weight: c.Weight, Messages: c.Messages})
	}
	return &bannerDTO{
		Campaigns: campaigns,
		Timings: bannerTimingsDTO{
			HoldMs:         timings.HoldMs,
			EdgePauseMs:    timings.EdgePauseMs,
			ScrollPxPerSec: timings.ScrollPxPerSec,
			FadeOutMs:      timings.FadeOutMs,
			GapMs:          timings.GapMs,
			FadeInMs:       timings.FadeInMs,
		},
	}
}

// bannerLang resolves the message language for a viewer: their interface language
// (Russian, or English by default).
func bannerLang(acc account.Account) string {
	if acc.PreferredLanguage == "ru" {
		return "ru"
	}
	return "en"
}

// publishBannerChange emits the in-app "banner eligibility may have changed"
// re-poll signal to the account, so an open client re-fetches profile.get and
// shows or hides the banner without a reload. Best-effort (notify.Nop when no
// notifier is wired).
func (s *Server) publishBannerChange(id uuid.UUID) {
	s.notifier.Publish(notify.BannerChanged(id))
}