package app

import (
	"context"
	"errors"
	"strings"
	"time"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	goredis "github.com/redis/go-redis/v9"

	"github.com/geo-platform/tenant-api/internal/shared/auth"
	"github.com/geo-platform/tenant-api/internal/shared/response"
	"github.com/geo-platform/tenant-api/internal/tenant/repository"
)

type DesktopAccountService struct {
	repo       repository.DesktopAccountRepository
	clientRepo repository.DesktopClientRepository
	redis      *goredis.Client
	now        func() time.Time
}

func NewDesktopAccountService(
	repo repository.DesktopAccountRepository,
	clientRepo repository.DesktopClientRepository,
	redis *goredis.Client,
) *DesktopAccountService {
	return &DesktopAccountService{
		repo:       repo,
		clientRepo: clientRepo,
		redis:      redis,
		now:        time.Now,
	}
}

type DesktopAccountView struct {
	ID                 string     `json:"id"`
	Platform           string     `json:"platform"`
	PlatformUID        string     `json:"platform_uid"`
	DisplayName        string     `json:"display_name"`
	AvatarURL          *string    `json:"avatar_url"`
	Health             string     `json:"health"`
	ClientID           *string    `json:"client_id"`
	AccountFingerprint *string    `json:"account_fingerprint"`
	VerifiedAt         *time.Time `json:"verified_at"`
	Tags               []string   `json:"tags"`
	SyncVersion        int64      `json:"sync_version"`
	DeletedAt          *time.Time `json:"deleted_at"`
	DeleteRequestedAt  *time.Time `json:"delete_requested_at"`
	ClientOnline       *bool      `json:"client_online"`
	ClientLastSeenAt   *time.Time `json:"client_last_seen_at"`
	ClientDeviceName   *string    `json:"client_device_name"`
}

type UpsertDesktopAccountRequest struct {
	Platform           string     `json:"platform" binding:"required"`
	PlatformUID        string     `json:"platform_uid" binding:"required"`
	AccountFingerprint *string    `json:"account_fingerprint"`
	DisplayName        string     `json:"display_name" binding:"required"`
	AvatarURL          *string    `json:"avatar_url"`
	Health             string     `json:"health" binding:"required,oneof=live expired captcha risk"`
	VerifiedAt         *time.Time `json:"verified_at"`
	Tags               []string   `json:"tags"`
	IfSyncVersion      *int64     `json:"if_sync_version"`
}

type PatchDesktopAccountRequest struct {
	DisplayName   *string    `json:"display_name"`
	Health        *string    `json:"health" binding:"omitempty,oneof=live expired captcha risk"`
	VerifiedAt    *time.Time `json:"verified_at"`
	Tags          *[]string  `json:"tags"`
	IfSyncVersion int64      `json:"if_sync_version" binding:"required"`
}

func (s *DesktopAccountService) ListByUser(ctx context.Context, client *repository.DesktopClient) ([]DesktopAccountView, error) {
	if client == nil {
		return nil, response.ErrUnauthorized(40108, "desktop_client_missing", "desktop client context is required")
	}

	rows, err := s.repo.ListByUser(ctx, client.WorkspaceID, client.UserID)
	if err != nil {
		return nil, response.ErrInternal(50081, "desktop_accounts_query_failed", "failed to list desktop accounts")
	}

	clientMap, presenceMap := s.loadClientState(ctx, client.WorkspaceID, rows)
	items := make([]DesktopAccountView, 0, len(rows))
	for _, item := range rows {
		items = append(items, s.buildDesktopAccountView(&item, clientMap, presenceMap))
	}
	return items, nil
}

func (s *DesktopAccountService) ListForActor(ctx context.Context, actor auth.Actor) ([]DesktopAccountView, error) {
	if actor.PrimaryWorkspaceID == 0 || actor.UserID == 0 {
		return nil, response.ErrUnauthorized(40132, "workspace_scope_missing", "workspace context is required")
	}

	rows, err := s.repo.ListByUser(ctx, actor.PrimaryWorkspaceID, actor.UserID)
	if err != nil {
		return nil, response.ErrInternal(50081, "desktop_accounts_query_failed", "failed to list desktop accounts")
	}

	clientMap, presenceMap := s.loadClientState(ctx, actor.PrimaryWorkspaceID, rows)
	items := make([]DesktopAccountView, 0, len(rows))
	for _, item := range rows {
		items = append(items, s.buildDesktopAccountView(&item, clientMap, presenceMap))
	}
	return items, nil
}

func (s *DesktopAccountService) Upsert(ctx context.Context, client *repository.DesktopClient, req UpsertDesktopAccountRequest) (*DesktopAccountView, error) {
	if client == nil {
		return nil, response.ErrUnauthorized(40108, "desktop_client_missing", "desktop client context is required")
	}

	if req.IfSyncVersion != nil {
		existing, err := s.repo.GetByIdentity(ctx, client.WorkspaceID, req.Platform, req.PlatformUID)
		if err != nil && !errors.Is(err, pgx.ErrNoRows) {
			return nil, response.ErrInternal(50082, "desktop_account_lookup_failed", "failed to inspect desktop account before upsert")
		}
		if existing == nil || errors.Is(err, pgx.ErrNoRows) {
			return nil, response.ErrConflict(40981, "desktop_account_sync_version_required_existing", "if_sync_version is only valid when account already exists")
		}
	}

	account, err := s.repo.Upsert(ctx, repository.UpsertDesktopAccountParams{
		DesktopID:          uuid.New(),
		TenantID:           client.TenantID,
		WorkspaceID:        client.WorkspaceID,
		UserID:             client.UserID,
		ClientID:           client.ID,
		Platform:           req.Platform,
		PlatformUID:        req.PlatformUID,
		AccountFingerprint: req.AccountFingerprint,
		DisplayName:        req.DisplayName,
		AvatarURL:          req.AvatarURL,
		Health:             req.Health,
		VerifiedAt:         req.VerifiedAt,
		Tags:               req.Tags,
		IfSyncVersion:      req.IfSyncVersion,
	})
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, response.ErrConflict(40982, "desktop_account_sync_conflict", "desktop account sync version conflict")
		}
		appErr := response.ErrInternal(50083, "desktop_account_upsert_failed", "failed to upsert desktop account")
		appErr.Cause = err
		return nil, appErr
	}

	view := s.buildDesktopAccountView(account, nil, nil)
	return &view, nil
}

func (s *DesktopAccountService) Patch(ctx context.Context, client *repository.DesktopClient, desktopID uuid.UUID, req PatchDesktopAccountRequest) (*DesktopAccountView, error) {
	if client == nil {
		return nil, response.ErrUnauthorized(40108, "desktop_client_missing", "desktop client context is required")
	}

	account, err := s.repo.Patch(ctx, repository.PatchDesktopAccountParams{
		DesktopID:     desktopID,
		WorkspaceID:   client.WorkspaceID,
		DisplayName:   req.DisplayName,
		Health:        req.Health,
		VerifiedAt:    req.VerifiedAt,
		Tags:          req.Tags,
		IfSyncVersion: req.IfSyncVersion,
	})
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, response.ErrConflict(40982, "desktop_account_sync_conflict", "desktop account sync version conflict")
		}
		return nil, response.ErrInternal(50084, "desktop_account_patch_failed", "failed to patch desktop account")
	}

	view := s.buildDesktopAccountView(account, nil, nil)
	return &view, nil
}

func (s *DesktopAccountService) Tombstone(ctx context.Context, client *repository.DesktopClient, desktopID uuid.UUID, ifSyncVersion int64) (*DesktopAccountView, error) {
	if client == nil {
		return nil, response.ErrUnauthorized(40108, "desktop_client_missing", "desktop client context is required")
	}

	account, err := s.repo.Tombstone(ctx, desktopID, client.WorkspaceID, ifSyncVersion)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, response.ErrConflict(40982, "desktop_account_sync_conflict", "desktop account sync version conflict")
		}
		return nil, response.ErrInternal(50085, "desktop_account_delete_failed", "failed to delete desktop account")
	}

	view := s.buildDesktopAccountView(account, nil, nil)
	return &view, nil
}

func (s *DesktopAccountService) RequestDelete(ctx context.Context, actor auth.Actor, desktopID uuid.UUID, undo bool) (*DesktopAccountView, error) {
	if actor.PrimaryWorkspaceID == 0 {
		return nil, response.ErrUnauthorized(40132, "workspace_scope_missing", "workspace context is required")
	}

	var (
		account *repository.DesktopAccount
		err     error
	)

	if undo {
		account, err = s.repo.ClearDeleteRequested(ctx, desktopID, actor.PrimaryWorkspaceID)
	} else {
		account, err = s.repo.MarkDeleteRequested(ctx, desktopID, actor.PrimaryWorkspaceID)
	}
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, response.ErrNotFound(40481, "desktop_account_not_found", "desktop account not found")
		}
		return nil, response.ErrInternal(50086, "desktop_account_request_delete_failed", "failed to update desktop account delete request")
	}

	view := s.buildDesktopAccountView(account, nil, nil)
	return &view, nil
}

func (s *DesktopAccountService) buildDesktopAccountView(
	account *repository.DesktopAccount,
	clientMap map[uuid.UUID]*repository.DesktopClient,
	presenceClientMap map[uuid.UUID]uuid.UUID,
) DesktopAccountView {
	var clientID *string
	var clientOnline *bool
	var clientLastSeenAt *time.Time
	var clientDeviceName *string

	resolvedClientID := account.ClientID
	if presenceClientMap != nil {
		if activeClientID, ok := presenceClientMap[account.DesktopID]; ok {
			resolvedClientID = &activeClientID
		}
	}

	if resolvedClientID != nil {
		value := resolvedClientID.String()
		clientID = &value

		online := false
		clientOnline = &online

		if clientMap != nil {
			if client, ok := clientMap[*resolvedClientID]; ok && client != nil {
				clientLastSeenAt = client.LastSeenAt
				clientDeviceName = client.DeviceName
				if presenceClientMap != nil {
					if activeClientID, ok := presenceClientMap[account.DesktopID]; ok && activeClientID == *resolvedClientID {
						online = true
					}
				}
			}
		}
	}

	return DesktopAccountView{
		ID:                 account.DesktopID.String(),
		Platform:           account.Platform,
		PlatformUID:        normalizePlatformUID(account.PlatformUID),
		DisplayName:        account.DisplayName,
		AvatarURL:          account.AvatarURL,
		Health:             account.Health,
		ClientID:           clientID,
		AccountFingerprint: account.AccountFingerprint,
		VerifiedAt:         account.VerifiedAt,
		Tags:               account.Tags,
		SyncVersion:        account.SyncVersion,
		DeletedAt:          account.DeletedAt,
		DeleteRequestedAt:  account.DeleteRequestedAt,
		ClientOnline:       clientOnline,
		ClientLastSeenAt:   clientLastSeenAt,
		ClientDeviceName:   clientDeviceName,
	}
}

func (s *DesktopAccountService) loadClientState(
	ctx context.Context,
	workspaceID int64,
	accounts []repository.DesktopAccount,
) (map[uuid.UUID]*repository.DesktopClient, map[uuid.UUID]uuid.UUID) {
	clientIDs := make([]uuid.UUID, 0, len(accounts)*2)
	accountIDs := make([]uuid.UUID, 0, len(accounts))
	seen := make(map[uuid.UUID]struct{}, len(accounts)*2)

	for _, account := range accounts {
		accountIDs = append(accountIDs, account.DesktopID)

		if account.ClientID == nil {
			continue
		}
		if _, ok := seen[*account.ClientID]; ok {
			continue
		}
		seen[*account.ClientID] = struct{}{}
		clientIDs = append(clientIDs, *account.ClientID)
	}

	presenceClientMap := loadDesktopAccountPresence(ctx, s.redis, accountIDs)
	for _, clientID := range presenceClientMap {
		if _, ok := seen[clientID]; ok {
			continue
		}
		seen[clientID] = struct{}{}
		clientIDs = append(clientIDs, clientID)
	}

	clientMap := make(map[uuid.UUID]*repository.DesktopClient, len(clientIDs))
	if s.clientRepo != nil {
		for _, clientID := range clientIDs {
			client, err := s.clientRepo.GetByID(ctx, clientID, workspaceID)
			if err != nil {
				if errors.Is(err, pgx.ErrNoRows) {
					continue
				}
				continue
			}
			clientMap[clientID] = client
		}
	}

	return clientMap, presenceClientMap
}

func resolveDesktopClientOnline(
	client *repository.DesktopClient,
	presence bool,
	presenceKnown bool,
	now time.Time,
) bool {
	if client == nil || client.RevokedAt != nil {
		return false
	}
	if presenceKnown && presence {
		return true
	}
	if client.LastSeenAt == nil {
		return false
	}
	return now.UTC().Sub(client.LastSeenAt.UTC()) <= desktopClientPresenceTTL
}

func normalizePlatformUID(value string) string {
	normalized := strings.TrimSpace(value)
	for strings.HasPrefix(strings.ToLower(normalized), "platform:") {
		normalized = strings.TrimSpace(normalized[len("platform:"):])
	}
	return normalized
}