package devices

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"
	"time"

	"github.com/wangjia/pangolin/server/internal/apierr"
)

// CredentialRevoker recalls a device's data-plane credential (its dp_uuid) on the
// node side when the device is cleared. Per migration 000015 the credential is
// per-device, so revocation targets the dp_uuid. Defined consumer-side to avoid an
// import cycle; nodes.Service satisfies it (push Revoke to the holding node(s) +
// drop the connect_credentials row). Best-effort: node resync reconciles misses.
type CredentialRevoker interface {
	RevokeDevice(ctx context.Context, dpUUID string) error
}

// NoopRevoker is the default CredentialRevoker (tests / before nodes wiring).
// It records the dp_uuids passed so callers/tests can assert on it.
type NoopRevoker struct {
	Calls []string
}

// RevokeDevice implements CredentialRevoker by recording the dp_uuid.
func (n *NoopRevoker) RevokeDevice(_ context.Context, dpUUID string) error {
	n.Calls = append(n.Calls, dpUUID)
	return nil
}

// SessionPort provides per-device session reads/revocations. Satisfied by
// sessions.Store; injected to keep packages decoupled.
type SessionPort interface {
	LastLoginByDevice(ctx context.Context, userID int64) (map[int64]time.Time, error)
	RevokeByDevice(ctx context.Context, userID, deviceID int64) ([]string, error)
	HasActiveSession(ctx context.Context, userID, deviceID int64) (bool, error)
	ActiveSessionDeviceIDs(ctx context.Context, userID int64) (map[int64]bool, error)
}

// JTIRevoker drops a refresh JTI from the Redis whitelist. Satisfied by
// auth.TokenManager (so a force-logged-out device's tokens stop refreshing).
type JTIRevoker interface {
	Revoke(ctx context.Context, jti string) error
}

// Service implements the devices business logic.
type Service struct {
	store      *Store
	revoker    CredentialRevoker
	sessions   SessionPort // nil until wired (P2/P3)
	jtiRevoker JTIRevoker   // nil until wired (P3)
}

// NewService creates a Service. If revoker is nil a NoopRevoker is used so the
// module can be wired and tested before nodes is available.
func NewService(store *Store, revoker CredentialRevoker) *Service {
	if revoker == nil {
		revoker = &NoopRevoker{}
	}
	return &Service{store: store, revoker: revoker}
}

// SetSessionPort / SetJTIRevoker / SetCredentialRevoker wire collaborators after
// construction (main keeps devices, sessions, auth and nodes decoupled).
func (svc *Service) SetSessionPort(s SessionPort)        { svc.sessions = s }
func (svc *Service) SetJTIRevoker(r JTIRevoker)          { svc.jtiRevoker = r }
func (svc *Service) SetCredentialRevoker(r CredentialRevoker) {
	if r != nil {
		svc.revoker = r
	}
}

// Device is the API representation of a registered device.
type Device struct {
	UUID          string  `json:"uuid"`
	Name          string  `json:"name"`
	Platform      string  `json:"platform"`
	LastSeen      *string `json:"last_seen"`                // RFC 3339 UTC; null when never seen
	ClientVersion string  `json:"client_version,omitempty"` // 000016
	Online        bool    `json:"online"`                   // last_seen within onlineWindow (data-plane active)
	LastLogin     *string `json:"last_login"`               // most recent session created_at; null when none
}

// onlineWindow: a device is "online" if its last_seen is within this window.
// last_seen is bumped by connect、用量上报,以及 ~15s 的会话轮询(SessionActive)——
// 后者让「在线」准确反映 app 正在运行。窗口取 90s(覆盖几次丢失的 15s 轮询),
// app 一关 ~90s 内转离线。
const onlineWindow = 90 * time.Second

// staleWindow: devices not seen within this window are "stale" — excluded from the
// plan-cap count and best-effort pruned on login. Covers free-plan reinstall churn
// (each reinstall churns the device UUID, leaving zombie rows) without locking users out.
const staleWindow = 30 * 24 * time.Hour

// DeviceLimitStatus reports the device-cap state. Over is true when the account's
// active device count exceeds the plan cap; Devices lists the active set so the
// client can present "remove a device" UX.
type DeviceLimitStatus struct {
	Over       bool     `json:"over"`
	MaxDevices int      `json:"max_devices"`
	Devices    []Device `json:"devices,omitempty"`
}

func toAPIDevice(d DeviceRow) Device {
	out := Device{UUID: d.UUID, Name: d.Name, Platform: d.Platform}
	if d.LastSeen.Valid {
		s := d.LastSeen.Time.UTC().Format(time.RFC3339)
		out.LastSeen = &s
		out.Online = time.Since(d.LastSeen.Time) < onlineWindow
	}
	if d.ClientVersion.Valid {
		out.ClientVersion = d.ClientVersion.String
	}
	return out
}

// ListDevices returns the user's devices with online status (from last_seen) and
// last-login time (most recent session, when a LastLoginSource is wired).
func (svc *Service) ListDevices(ctx context.Context, userID int64) ([]Device, *apierr.Error) {
	rows, err := svc.store.ListByUser(ctx, userID)
	if err != nil {
		return nil, apierr.ErrInternal
	}
	var lastLogin map[int64]time.Time
	var activeSet map[int64]bool
	if svc.sessions != nil {
		if m, e := svc.sessions.LastLoginByDevice(ctx, userID); e == nil {
			lastLogin = m
		}
		// 有活跃会话集:online 须同时满足「last_seen 新」+「会话未撤销」,
		// 被强退的设备没有活跃会话 → 立即离线(不必等 last_seen 窗口过期)。
		if m, e := svc.sessions.ActiveSessionDeviceIDs(ctx, userID); e == nil {
			activeSet = m
		}
	}
	out := make([]Device, 0, len(rows))
	for _, r := range rows {
		d := toAPIDevice(r)
		if activeSet != nil && !activeSet[r.ID] {
			d.Online = false // 无未撤销会话 → 强制离线(activeSet 为 nil 时不干预,fail-open)
		}
		if t, ok := lastLogin[r.ID]; ok {
			s := t.UTC().Format(time.RFC3339)
			d.LastLogin = &s
		}
		out = append(out, d)
	}
	return out, nil
}

// RegisterInput carries the inputs for implicit device registration, called by
// nodes.connect when a client presents a device_id.
type RegisterInput struct {
	UserID        int64
	DeviceUUID    string
	Name          string // client-reported, may come from UA; truncated to 64 runes
	Platform      string // ios | android | windows | macos | linux
	ClientVersion string // app version, stored/refreshed on devices.client_version
	MaxDevices    int    // plan cap; 0 = no cap
}

// RegisterIfAbsent registers a device on first sight and refreshes last_seen on
// subsequent sights. The device count is checked against MaxDevices before
// inserting a brand-new device. Per-user serialization is achieved by locking
// the users row for the duration of the transaction.
// Returns the internal device id (for session binding), the API device, or an error.
func (svc *Service) RegisterIfAbsent(ctx context.Context, in RegisterInput) (int64, *Device, *apierr.Error) {
	uuid := strings.TrimSpace(in.DeviceUUID)
	if uuid == "" {
		return 0, nil, apierr.ErrBadRequest
	}
	platform, ok := normalizePlatform(in.Platform)
	if !ok {
		return 0, nil, apierr.ErrBadRequest
	}
	name := normalizeName(in.Name, platform)

	tx, err := svc.store.BeginTx(ctx)
	if err != nil {
		return 0, nil, apierr.ErrInternal
	}
	committed := false
	defer func() {
		if !committed {
			_ = tx.Rollback()
		}
	}()

	// Lock the owning user to serialize concurrent registrations.
	exists, status, err := svc.store.lockUser(ctx, tx, in.UserID)
	if err != nil {
		return 0, nil, apierr.ErrInternal
	}
	if !exists {
		return 0, nil, apierr.ErrUnauthorized
	}
	if status == "banned" {
		return 0, nil, apierr.ErrAccountBanned
	}

	// 按 (user,uuid) 查:唯一键是 UNIQUE(user_id,uuid)(migration 21),同一物理设备
	// 在别的账号名下的行与本次注册无关 —— 同机换账号各自成行,不再互相 403(F3)。
	existing, err := svc.store.findDeviceByUserUUIDTx(ctx, tx, in.UserID, uuid)
	if err != nil {
		return 0, nil, apierr.ErrInternal
	}
	if existing != nil {
		if err := svc.store.touchLastSeenTx(ctx, tx, existing.ID, in.ClientVersion); err != nil {
			return 0, nil, apierr.ErrInternal
		}
		if err := tx.Commit(); err != nil {
			return 0, nil, apierr.ErrInternal
		}
		committed = true
		d := toAPIDevice(*existing)
		return existing.ID, &d, nil
	}

	// New device: enforce the plan device cap.
	count, err := svc.store.countDevicesTx(ctx, tx, in.UserID)
	if err != nil {
		return 0, nil, apierr.ErrInternal
	}
	if in.MaxDevices > 0 && count >= in.MaxDevices {
		return 0, nil, errDeviceLimit(in.MaxDevices)
	}

	row, err := svc.store.insertDeviceTx(ctx, tx, uuid, in.UserID, name, platform, in.ClientVersion)
	if err != nil {
		return 0, nil, apierr.ErrInternal
	}
	if err := svc.store.writeAuditLogTx(ctx, tx,
		fmt.Sprintf("user:%d", in.UserID), "device.register", "device:"+uuid,
		deviceAuditMeta(name, platform)); err != nil {
		_ = err // audit failure must not abort the business transaction
	}
	if err := tx.Commit(); err != nil {
		return 0, nil, apierr.ErrInternal
	}
	committed = true

	d := toAPIDevice(*row)
	return row.ID, &d, nil
}

// DeleteDevice hard-deletes a device (transactionally, with an audit_log entry)
// and then triggers per-user credential recall on the node side.
//
//   - device not found            → 404 NOT_FOUND
//   - device owned by another user → 404 NOT_FOUND (user-scoped lookup; invisible)
func (svc *Service) DeleteDevice(ctx context.Context, userID int64, deviceUUID string) *apierr.Error {
	uuid := strings.TrimSpace(deviceUUID)
	if uuid == "" {
		return apierr.ErrBadRequest
	}

	// Resolve (non-tx) so sessions can be revoked BEFORE the delete tx: SQLite
	// (_txlock=immediate) holds a write lock for the tx, so a session write on
	// another pool connection would deadlock against it. Lookup is user-scoped
	// (UNIQUE(user_id,uuid)) — other users' rows with the same uuid are invisible,
	// so "not mine" and "not found" are both 404.
	dev, err := svc.store.FindByUserUUID(ctx, userID, uuid)
	if err != nil {
		return apierr.ErrInternal
	}
	if dev == nil {
		return apierr.ErrNotFound
	}

	// Revoke the device's sessions (drop their refresh JTIs from Redis) while the
	// rows still exist; the device delete then cascades them away.
	svc.revokeDeviceSessions(ctx, userID, dev.ID)

	tx, err := svc.store.BeginTx(ctx)
	if err != nil {
		return apierr.ErrInternal
	}
	committed := false
	defer func() {
		if !committed {
			_ = tx.Rollback()
		}
	}()

	if err := svc.store.deleteDeviceTx(ctx, tx, dev.ID); err != nil {
		return apierr.ErrInternal
	}
	if err := svc.store.writeAuditLogTx(ctx, tx,
		fmt.Sprintf("user:%d", userID), "device.delete", "device:"+uuid,
		deviceAuditMeta(dev.Name, dev.Platform)); err != nil {
		_ = err // audit failure must not abort the delete
	}
	if err := tx.Commit(); err != nil {
		return apierr.ErrInternal
	}
	committed = true

	// Recall the device's data-plane credential so a live connection is dropped
	// too. Best-effort: the device row is already gone; a transient failure is
	// reconciled by node resync, so we never fail the request. (Sessions were
	// already revoked above, before the cascade removed their rows.)
	if dev.DpUUID.Valid && dev.DpUUID.String != "" {
		if err := svc.revoker.RevokeDevice(ctx, dev.DpUUID.String); err != nil {
			_ = err
		}
	}
	return nil
}

// ForceLogout revokes a device's login sessions (kicks it offline; the device
// stays in the list). The device's data-plane credential is left intact so the
// user can simply log in again.
//
//   - device not found            → 404 NOT_FOUND
//   - device owned by another user → 404 NOT_FOUND (user-scoped lookup; invisible)
func (svc *Service) ForceLogout(ctx context.Context, userID int64, deviceUUID string) *apierr.Error {
	uuid := strings.TrimSpace(deviceUUID)
	if uuid == "" {
		return apierr.ErrBadRequest
	}
	dev, err := svc.store.FindByUserUUID(ctx, userID, uuid)
	if err != nil {
		return apierr.ErrInternal
	}
	if dev == nil {
		return apierr.ErrNotFound
	}
	svc.revokeDeviceSessions(ctx, userID, dev.ID)
	return nil
}

// RenameDevice sets a device's display name (ownership-checked). Empty name →
// 400; name is trimmed + truncated to 64 runes.
//
//   - device not found            → 404
//   - device owned by another user → 404 (user-scoped lookup; invisible)
func (svc *Service) RenameDevice(ctx context.Context, userID int64, deviceUUID, rawName string) *apierr.Error {
	uuid := strings.TrimSpace(deviceUUID)
	name := strings.TrimSpace(rawName)
	if uuid == "" || name == "" {
		return apierr.ErrBadRequest
	}
	if r := []rune(name); len(r) > 64 {
		name = string(r[:64])
	}
	dev, err := svc.store.FindByUserUUID(ctx, userID, uuid)
	if err != nil {
		return apierr.ErrInternal
	}
	if dev == nil {
		return apierr.ErrNotFound
	}
	if err := svc.store.UpdateName(ctx, dev.ID, name); err != nil {
		return apierr.ErrInternal
	}
	return nil
}

// SessionActive reports whether the device (by UUID) still has a live login session
// for the user — false after a force-logout elsewhere. The client polls this (~15s)
// and logs out on false → near-instant remote kick. Fail-open (return true) on a
// missing session port / blank or unknown / not-own device, so transient ambiguity
// never spuriously logs a user out.
func (svc *Service) SessionActive(ctx context.Context, userID int64, deviceUUID string) (bool, *apierr.Error) {
	if svc.sessions == nil || strings.TrimSpace(deviceUUID) == "" {
		return true, nil
	}
	dev, err := svc.store.FindByUserUUID(ctx, userID, deviceUUID)
	if err != nil {
		return false, apierr.ErrInternal
	}
	if dev == nil {
		// 本用户名下无此设备行 = 本设备被「移除」(DeleteDevice 删行)。已登录的客户端在
		// 登录时必然注册过自己的设备,轮询自身 device_id 却查无此行,只能是被移除 → 视为
		// 会话失效,让其登出(否则被移除的设备永远收到 active=true,不退出,只表现为数据面
		// 被断→「节点异常」)。查找按 (user,uuid) 作用域,他人账号下的同 uuid 行不可见,
		// 不存在旧「非本人设备 fail-safe」分支。
		return false, nil
	}
	active, err := svc.sessions.HasActiveSession(ctx, userID, dev.ID)
	if err != nil {
		return false, apierr.ErrInternal
	}
	// 仅活跃会话才刷 last_seen(=app 在运行且未被踢)。被强退设备的轮询不刷,
	// 否则那一刷会把它顶成「在线」直到窗口过期(本问题的根因)。
	if active {
		_ = svc.store.TouchLastSeen(ctx, dev.ID)
	}
	return active, nil
}

// revokeDeviceSessions marks all of a device's sessions revoked and drops their
// refresh JTIs from the Redis whitelist. Best-effort.
func (svc *Service) revokeDeviceSessions(ctx context.Context, userID, deviceID int64) {
	if svc.sessions == nil {
		return
	}
	jtis, err := svc.sessions.RevokeByDevice(ctx, userID, deviceID)
	if err != nil {
		return
	}
	if svc.jtiRevoker != nil {
		for _, jti := range jtis {
			_ = svc.jtiRevoker.Revoke(ctx, jti)
		}
	}
}

// SubscriptionInfo is the /v1/me subscription summary provided by this module.
type SubscriptionInfo struct {
	PlanCode  string  `json:"plan_code"`
	ExpiresAt *string `json:"expires_at"` // RFC 3339 UTC; null for free fallback
	Source    string  `json:"source"`
}

// SubscriptionSummary resolves the user's effective plan and returns the /v1/me
// subscription summary.
func (svc *Service) SubscriptionSummary(ctx context.Context, userID int64) (*SubscriptionInfo, *apierr.Error) {
	p, apiErr := svc.ResolvePlan(ctx, userID)
	if apiErr != nil {
		return nil, apiErr
	}
	info := &SubscriptionInfo{PlanCode: p.PlanCode, Source: p.Source}
	if p.ExpiresAt != nil {
		s := p.ExpiresAt.UTC().Format(time.RFC3339)
		info.ExpiresAt = &s
	}
	return info, nil
}

// ResolvePlan loads the user's status + subscriptions and resolves the effective
// plan. It is the shared entry point used by SubscriptionMiddleware and
// SubscriptionSummary.
func (svc *Service) ResolvePlan(ctx context.Context, userID int64) (Plan, *apierr.Error) {
	status, exists, err := svc.store.GetUserStatus(ctx, userID)
	if err != nil {
		return Plan{}, apierr.ErrInternal
	}
	if !exists {
		return Plan{}, apierr.ErrUnauthorized
	}
	subs, err := svc.store.GetSubscriptions(ctx, userID)
	if err != nil {
		return Plan{}, apierr.ErrInternal
	}
	free, err := svc.store.GetFreePlan(ctx)
	if err != nil {
		return Plan{}, apierr.ErrInternal
	}
	return resolveEffectivePlan(time.Now().UTC(), status, subs, free)
}

// CheckDeviceLimit prunes stale devices (best-effort churn cleanup), resolves the
// plan cap, and reports whether the account's active device count exceeds it. Used
// by the login flow (non-hard-reject gate) and the connect backstop. When over, the
// active device list is included so the client can present "remove a device" UX.
// The device is already registered by the time this runs, so "over" means
// activeCount > cap. MaxDevices==0 means uncapped (never over).
func (svc *Service) CheckDeviceLimit(ctx context.Context, userID int64) (*DeviceLimitStatus, *apierr.Error) {
	cutoff := time.Now().UTC().Add(-staleWindow)
	if _, err := svc.store.PruneStaleDevices(ctx, userID, cutoff); err != nil {
		_ = err // prune failure must never block login/connect
	}
	plan, apiErr := svc.ResolvePlan(ctx, userID)
	if apiErr != nil {
		return nil, apiErr
	}
	active, err := svc.store.CountActiveDevices(ctx, userID, cutoff)
	if err != nil {
		return nil, apierr.ErrInternal
	}
	st := &DeviceLimitStatus{MaxDevices: plan.MaxDevices}
	st.Over = plan.MaxDevices > 0 && active > plan.MaxDevices
	if st.Over {
		devs, apiErr := svc.ListDevices(ctx, userID)
		if apiErr != nil {
			return nil, apiErr
		}
		st.Devices = devs
	}
	return st, nil
}

// resolveEffectivePlan is the pure plan-resolution rule (no I/O), unit-tested
// directly:
//
//   - banned account                         → ErrAccountBanned
//   - among subscriptions with expires_at>now, pick the highest tier;
//     ties broken by the latest expiry
//   - no active subscription                 → free fallback (ExpiresAt nil)
//
// now must be in UTC. The boundary is strict: expires_at == now counts as expired.
func resolveEffectivePlan(now time.Time, status string, subs []effSub, free Plan) (Plan, *apierr.Error) {
	if status == "banned" {
		return Plan{}, apierr.ErrAccountBanned
	}

	var best *effSub
	for i := range subs {
		s := &subs[i]
		if !s.ExpiresAt.After(now) {
			continue // expired (strict UTC boundary)
		}
		if best == nil {
			best = s
			continue
		}
		bt, st := planTier(best.PlanCode), planTier(s.PlanCode)
		if st > bt || (st == bt && s.ExpiresAt.After(best.ExpiresAt)) {
			best = s
		}
	}

	if best == nil {
		return free, nil
	}

	exp := best.ExpiresAt.UTC()
	p := Plan{
		PlanCode:   best.PlanCode,
		ExpiresAt:  &exp,
		MaxDevices: best.MaxDevices,
		AdGate:     best.AdGate,
		Source:     best.Source,
	}
	if best.DailyMinutes.Valid {
		m := int(best.DailyMinutes.Int64)
		p.DailyMinutes = &m
	}
	return p, nil
}

// --------------------------------------------------------------------------
// helpers
// --------------------------------------------------------------------------

// normalizePlatform validates/canonicalizes a platform string against the
// devices.platform ENUM (ios/android/windows/macos). Note: the OpenAPI Device
// schema also lists "linux", but the DB ENUM (migration #1) does not include
// it, so "linux" is rejected until the schema is widened.
func normalizePlatform(s string) (string, bool) {
	switch strings.ToLower(strings.TrimSpace(s)) {
	case "ios":
		return "ios", true
	case "android":
		return "android", true
	case "windows":
		return "windows", true
	case "macos":
		return "macos", true
	case "linux":
		return "linux", true
	}
	return "", false
}

// normalizeName trims the client-reported name, falls back to the platform when
// empty, and truncates to the devices.name VARCHAR(64) limit (by rune).
func normalizeName(name, platform string) string {
	name = strings.TrimSpace(name)
	if name == "" {
		name = platform
	}
	r := []rune(name)
	if len(r) > 64 {
		name = string(r[:64])
	}
	return name
}

// deviceAuditMeta builds a compact JSON meta blob for audit_log.
func deviceAuditMeta(name, platform string) string {
	b, _ := json.Marshal(map[string]string{"name": name, "platform": platform})
	return string(b)
}

// errDeviceLimit builds a bilingual device-cap error that embeds the limit.
func errDeviceLimit(max int) *apierr.Error {
	return &apierr.Error{
		Code:      "DEVICE_LIMIT_EXCEEDED",
		MessageZH: fmt.Sprintf("设备数量已达上限（%d 台），请先在其他设备上退出后重试", max),
		MessageEn: fmt.Sprintf("Device limit reached (%d devices). Please remove another device and try again.", max),
	}
}