package logic

import (
	"context"
	"time"

	"spark-server/internal/module/moment/entity"
)

type visCtx struct {
	viewer    int64
	selfAlbum bool
	friends   map[int64]bool
	blocked   map[int64]bool
	hideHim   map[int64]bool
	hideMe    map[int64]bool
	settings  map[int64]*entity.Settings
	audience  map[int64][]int64
	now       time.Time
}

func (v *visCtx) canSee(p *entity.Post) bool {
	if p == nil || p.Status != entity.StatusNormal {
		return false
	}
	if p.UserID == v.viewer {
		return true
	}
	if !v.friends[p.UserID] || v.blocked[p.UserID] || v.hideHim[p.UserID] || v.hideMe[p.UserID] {
		return false
	}
	if !v.selfAlbum {
		days := entity.VisibleAll
		if s := v.settings[p.UserID]; s != nil {
			days = s.VisibleDays
		}
		if !withinDays(p.CreatedAtMS, days, v.now) {
			return false
		}
	}
	return visibilityOK(p, v.viewer, v.audience[p.ID])
}

func visibilityOK(p *entity.Post, viewer int64, peers []int64) bool {
	switch p.Visibility {
	case entity.VisibilityFriends:
		return true
	case entity.VisibilityPrivate:
		return false
	case entity.VisibilityInclude:
		return containsID(peers, viewer)
	case entity.VisibilityExclude:
		return !containsID(peers, viewer)
	default:
		return false
	}
}

func withinDays(createdMS int64, days entity.VisibleDays, now time.Time) bool {
	if days <= 0 || createdMS <= 0 {
		return true
	}
	return createdMS >= now.AddDate(0, 0, -int(days)).UnixMilli()
}

func containsID(ids []int64, want int64) bool {
	for _, id := range ids {
		if id == want {
			return true
		}
	}
	return false
}

func (s *Service) visFor(ctx context.Context, viewer int64, posts []*entity.Post, selfAlbum bool) (*visCtx, error) {
	authors := uniqueAuthors(posts)
	v := &visCtx{
		viewer: viewer, selfAlbum: selfAlbum, friends: map[int64]bool{}, blocked: map[int64]bool{},
		hideHim: map[int64]bool{}, hideMe: map[int64]bool{}, now: time.Now(),
	}
	friendIDs, err := s.friends.ListFriendIDs(ctx, viewer)
	if err != nil {
		return nil, err
	}
	for _, id := range friendIDs {
		v.friends[id] = true
	}
	blocked, err := s.friends.ListBlockedPeerIDs(ctx, viewer)
	if err != nil {
		return nil, err
	}
	for _, id := range blocked {
		v.blocked[id] = true
	}
	if err := s.fillHides(ctx, viewer, v); err != nil {
		return nil, err
	}
	v.settings, err = s.repo.ListSettings(ctx, authors)
	if err != nil {
		return nil, err
	}
	needAud := make([]int64, 0)
	for _, p := range posts {
		if p != nil && p.Visibility.NeedsAudience() {
			needAud = append(needAud, p.ID)
		}
	}
	v.audience, err = s.repo.ListAudience(ctx, needAud)
	return v, err
}

func (s *Service) fillHides(ctx context.Context, viewer int64, v *visCtx) error {
	him, err := s.repo.HideHimIDs(ctx, viewer)
	if err != nil {
		return err
	}
	for _, id := range him {
		v.hideHim[id] = true
	}
	me, err := s.repo.HideMeFromIDs(ctx, viewer)
	if err != nil {
		return err
	}
	for _, id := range me {
		v.hideMe[id] = true
	}
	return nil
}

func uniqueAuthors(posts []*entity.Post) []int64 {
	seen := make(map[int64]struct{})
	out := make([]int64, 0)
	for _, p := range posts {
		if p == nil || p.UserID <= 0 {
			continue
		}
		if _, ok := seen[p.UserID]; ok {
			continue
		}
		seen[p.UserID] = struct{}{}
		out = append(out, p.UserID)
	}
	return out
}

func idSet(ids []int64) map[int64]bool {
	out := make(map[int64]bool, len(ids))
	for _, id := range ids {
		out[id] = true
	}
	return out
}