package usecase

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"strings"
	"time"
	"unicode/utf8"

	"cmroubao/backend-api/internal/domain"
)

const (
	lifecycleCreatorSubject = "local-admin"
	maxLifecycleStepBytes   = 64
)

type LifecycleService struct {
	repository   LifecycleRepository
	clock        Clock
	ids          IDGenerator
	claimLease   time.Duration
	runningLease time.Duration
	readinessTTL time.Duration
}

type DeviceHeartbeatCommand struct {
	UserID               string
	DeviceID             string
	AppVersion           string
	AndroidVersion       string
	PDDVersion           string
	AccessibilityEnabled bool
	PDDInstalled         bool
	ClientActiveTaskID   *string
}

type DeviceHeartbeatResult struct {
	Device             domain.Device
	ActiveTaskID       *string
	ClientStateMatches bool
	ServerTime         time.Time
}

type ClaimNextCommand struct {
	UserID         string
	DeviceID       string
	IdempotencyKey string
	ClaimToken     string
}

type ClaimNextResult struct {
	Task       *domain.PurchaseTask
	Replayed   bool
	ServerTime time.Time
}

type StartTaskCommand struct {
	UserID          string
	DeviceID        string
	TaskID          string
	ClaimGeneration int64
	ClaimToken      string
	ExpectedVersion int64
	IdempotencyKey  string
}

type StartTaskResult struct {
	Task       domain.PurchaseTask
	Execution  domain.TaskExecution
	Replayed   bool
	ServerTime time.Time
}

type TaskHeartbeatCommand struct {
	UserID          string
	DeviceID        string
	TaskID          string
	ExecutionID     string
	ClaimGeneration int64
	ClaimToken      string
	Step            string
}

type TaskHeartbeatResult struct {
	Task            domain.PurchaseTask
	Execution       domain.TaskExecution
	CancelRequested bool
	ServerTime      time.Time
}

type ReferenceImageCommand struct {
	UserID          string
	DeviceID        string
	TaskID          string
	ClaimGeneration int64
	ClaimToken      string
}

type ReleaseTaskCommand struct {
	UserID          string
	DeviceID        string
	TaskID          string
	ClaimGeneration int64
	ClaimToken      string
	ExpectedVersion int64
	IdempotencyKey  string
}

type ReleaseTaskResult struct {
	Task       domain.PurchaseTask
	Replayed   bool
	ServerTime time.Time
}

type AcknowledgeCancellationCommand struct {
	UserID          string
	DeviceID        string
	TaskID          string
	ExecutionID     string
	ClaimGeneration int64
	ClaimToken      string
	ExpectedVersion int64
	IdempotencyKey  string
}

type AcknowledgeCancellationResult struct {
	Task       domain.PurchaseTask
	Replayed   bool
	ServerTime time.Time
}

func NewLifecycleService(
	repository LifecycleRepository,
	clock Clock,
	ids IDGenerator,
	claimLease time.Duration,
	runningLease time.Duration,
	readinessTTL time.Duration,
) (*LifecycleService, error) {
	if repository == nil || clock == nil || ids == nil {
		return nil, errors.New("lifecycle service dependencies are required")
	}
	if claimLease <= 0 || runningLease <= 0 || readinessTTL <= 0 {
		return nil, errors.New("lifecycle durations must be positive")
	}
	return &LifecycleService{
		repository:   repository,
		clock:        clock,
		ids:          ids,
		claimLease:   claimLease,
		runningLease: runningLease,
		readinessTTL: readinessTTL,
	}, nil
}

func (service *LifecycleService) HeartbeatDevice(
	ctx context.Context,
	command DeviceHeartbeatCommand,
) (DeviceHeartbeatResult, error) {
	command.UserID = strings.TrimSpace(command.UserID)
	command.DeviceID = strings.TrimSpace(command.DeviceID)
	fields := lifecycleIdentityFields(command.UserID, command.DeviceID)
	appVersion := strings.TrimSpace(command.AppVersion)
	androidVersion := strings.TrimSpace(command.AndroidVersion)
	pddVersion := strings.TrimSpace(command.PDDVersion)
	validateVersionField(fields, "app_version", appVersion)
	validateVersionField(fields, "android_version", androidVersion)
	validateVersionField(fields, "pdd_version", pddVersion)
	if command.ClientActiveTaskID != nil {
		value := strings.TrimSpace(*command.ClientActiveTaskID)
		command.ClientActiveTaskID = &value
		if value != "" && !isUUID(value) {
			fields["active_task_id"] = "must be a UUID or null"
		}
	}
	if len(fields) > 0 {
		return DeviceHeartbeatResult{}, invalidError(
			"DEVICE_HEARTBEAT_INVALID",
			"device heartbeat is invalid",
			fields,
		)
	}
	now := service.clock.Now().UTC()
	record, err := service.repository.RecordDeviceHeartbeat(
		ctx,
		DeviceHeartbeatUpdate{
			UserID:               command.UserID,
			DeviceID:             command.DeviceID,
			AppVersion:           appVersion,
			AndroidVersion:       androidVersion,
			PDDVersion:           pddVersion,
			AccessibilityEnabled: command.AccessibilityEnabled,
			PDDInstalled:         command.PDDInstalled,
			ReportedAt:           now,
		},
	)
	if err != nil {
		return DeviceHeartbeatResult{},
			wrapLifecycleRepositoryError(err)
	}
	return DeviceHeartbeatResult{
		Device:       record.Device,
		ActiveTaskID: record.ActiveTaskID,
		ClientStateMatches: sameOptionalID(
			command.ClientActiveTaskID,
			record.ActiveTaskID,
		),
		ServerTime: now,
	}, nil
}

func (service *LifecycleService) ClaimNext(
	ctx context.Context,
	command ClaimNextCommand,
) (ClaimNextResult, error) {
	command.UserID = strings.TrimSpace(command.UserID)
	command.DeviceID = strings.TrimSpace(command.DeviceID)
	command.IdempotencyKey = strings.TrimSpace(command.IdempotencyKey)
	fields := lifecycleWriteFields(
		command.UserID,
		command.DeviceID,
		command.IdempotencyKey,
		command.ClaimToken,
	)
	if len(fields) > 0 {
		return ClaimNextResult{}, invalidError(
			"TASK_CLAIM_INVALID",
			"task claim request is invalid",
			fields,
		)
	}
	requestHash, err := lifecycleRequestHash(struct {
		UserID         string `json:"user_id"`
		DeviceID       string `json:"device_id"`
		ClaimTokenHash string `json:"claim_token_sha256"`
	}{
		UserID:         command.UserID,
		DeviceID:       command.DeviceID,
		ClaimTokenHash: hashSecret(command.ClaimToken),
	})
	if err != nil {
		return ClaimNextResult{}, internalLifecycleFailure(err)
	}
	event, err := service.newLifecycleEvent(
		command.UserID,
		command.DeviceID,
		"",
		"TASK_CLAIMED",
		"task claimed",
	)
	if err != nil {
		return ClaimNextResult{}, err
	}
	now := service.clock.Now().UTC()
	result, err := service.repository.ClaimNext(
		ctx,
		ClaimNextRepositoryRequest{
			CreatorSubject: lifecycleCreatorSubject,
			UserID:         command.UserID,
			DeviceID:       command.DeviceID,
			IdempotencyKey: command.IdempotencyKey,
			RequestHash:    requestHash,
			ClaimTokenHash: hashSecret(command.ClaimToken),
			Now:            now,
			ExpiresAt:      now.Add(service.claimLease),
			ReadinessAfter: now.Add(-service.readinessTTL),
			Event:          event,
		},
	)
	if err != nil {
		return ClaimNextResult{}, wrapLifecycleRepositoryError(err)
	}
	return ClaimNextResult{
		Task:       result.Task,
		Replayed:   result.Replayed,
		ServerTime: now,
	}, nil
}

func (service *LifecycleService) StartTask(
	ctx context.Context,
	command StartTaskCommand,
) (StartTaskResult, error) {
	command = normalizeStartTaskCommand(command)
	fields := lifecycleTransitionFields(
		command.UserID,
		command.DeviceID,
		command.TaskID,
		command.ClaimGeneration,
		command.ClaimToken,
		command.ExpectedVersion,
		command.IdempotencyKey,
	)
	if len(fields) > 0 {
		return StartTaskResult{}, invalidError(
			"TASK_START_INVALID",
			"task start request is invalid",
			fields,
		)
	}
	executionID, err := service.ids.NewID()
	if err != nil {
		return StartTaskResult{}, internalLifecycleFailure(err)
	}
	event, err := service.newLifecycleEvent(
		command.UserID,
		command.DeviceID,
		command.TaskID,
		"TASK_STARTED",
		"task started",
	)
	if err != nil {
		return StartTaskResult{}, err
	}
	now := service.clock.Now().UTC()
	requestHash, err := lifecycleRequestHash(commandHashView{
		TaskID:          command.TaskID,
		ClaimGeneration: command.ClaimGeneration,
		ClaimTokenHash:  hashSecret(command.ClaimToken),
		ExpectedVersion: command.ExpectedVersion,
	})
	if err != nil {
		return StartTaskResult{}, internalLifecycleFailure(err)
	}
	result, err := service.repository.StartTask(
		ctx,
		StartTaskRepositoryRequest{
			UserID:          command.UserID,
			DeviceID:        command.DeviceID,
			TaskID:          command.TaskID,
			ClaimGeneration: command.ClaimGeneration,
			ClaimTokenHash:  hashSecret(command.ClaimToken),
			ExpectedVersion: command.ExpectedVersion,
			IdempotencyKey:  command.IdempotencyKey,
			RequestHash:     requestHash,
			Now:             now,
			ExpiresAt:       now.Add(service.runningLease),
			Execution: domain.TaskExecution{
				ID:              executionID,
				TaskID:          command.TaskID,
				ClaimGeneration: command.ClaimGeneration,
				UserID:          command.UserID,
				DeviceID:        command.DeviceID,
				CurrentStep:     "PREFLIGHT",
				OrderSubmitted:  false,
				StartedAt:       now,
			},
			Event: event,
		},
	)
	if err != nil {
		return StartTaskResult{}, wrapLifecycleRepositoryError(err)
	}
	return StartTaskResult{
		Task:       result.Task,
		Execution:  result.Execution,
		Replayed:   result.Replayed,
		ServerTime: now,
	}, nil
}

func (service *LifecycleService) HeartbeatTask(
	ctx context.Context,
	command TaskHeartbeatCommand,
) (TaskHeartbeatResult, error) {
	command.UserID = strings.TrimSpace(command.UserID)
	command.DeviceID = strings.TrimSpace(command.DeviceID)
	command.TaskID = strings.TrimSpace(command.TaskID)
	command.ExecutionID = strings.TrimSpace(command.ExecutionID)
	command.Step = strings.TrimSpace(command.Step)
	fields := lifecycleClaimFields(
		command.UserID,
		command.DeviceID,
		command.TaskID,
		command.ClaimGeneration,
		command.ClaimToken,
	)
	if !isUUID(command.ExecutionID) {
		fields["execution_id"] = "must be a UUID"
	}
	if !validLifecycleStep(command.Step) {
		fields["step"] = "must be 1-64 uppercase ASCII characters"
	}
	if len(fields) > 0 {
		return TaskHeartbeatResult{}, invalidError(
			"TASK_HEARTBEAT_INVALID",
			"task heartbeat is invalid",
			fields,
		)
	}
	now := service.clock.Now().UTC()
	result, err := service.repository.HeartbeatTask(
		ctx,
		TaskHeartbeatRepositoryRequest{
			UserID:          command.UserID,
			DeviceID:        command.DeviceID,
			TaskID:          command.TaskID,
			ExecutionID:     command.ExecutionID,
			ClaimGeneration: command.ClaimGeneration,
			ClaimTokenHash:  hashSecret(command.ClaimToken),
			Step:            command.Step,
			Now:             now,
			MinimumExpiry:   now.Add(service.runningLease),
		},
	)
	if err != nil {
		return TaskHeartbeatResult{},
			wrapLifecycleRepositoryError(err)
	}
	return TaskHeartbeatResult{
		Task:            result.Task,
		Execution:       result.Execution,
		CancelRequested: result.CancelRequested,
		ServerTime:      now,
	}, nil
}

func (service *LifecycleService) AuthorizeReferenceImage(
	ctx context.Context,
	command ReferenceImageCommand,
) (domain.PurchaseTask, error) {
	command.UserID = strings.TrimSpace(command.UserID)
	command.DeviceID = strings.TrimSpace(command.DeviceID)
	command.TaskID = strings.TrimSpace(command.TaskID)
	fields := lifecycleClaimFields(
		command.UserID,
		command.DeviceID,
		command.TaskID,
		command.ClaimGeneration,
		command.ClaimToken,
	)
	if len(fields) > 0 {
		return domain.PurchaseTask{}, invalidError(
			"TASK_REFERENCE_IMAGE_INVALID",
			"task reference image request is invalid",
			fields,
		)
	}
	task, err := service.repository.GetActiveClaimTask(
		ctx,
		TaskClaimRepositoryRequest{
			UserID:          command.UserID,
			DeviceID:        command.DeviceID,
			TaskID:          command.TaskID,
			ClaimGeneration: command.ClaimGeneration,
			ClaimTokenHash:  hashSecret(command.ClaimToken),
			Now:             service.clock.Now().UTC(),
		},
	)
	if err != nil {
		return domain.PurchaseTask{},
			wrapLifecycleRepositoryError(err)
	}
	return task, nil
}

func (service *LifecycleService) ReleaseTask(
	ctx context.Context,
	command ReleaseTaskCommand,
) (ReleaseTaskResult, error) {
	command.UserID = strings.TrimSpace(command.UserID)
	command.DeviceID = strings.TrimSpace(command.DeviceID)
	command.TaskID = strings.TrimSpace(command.TaskID)
	command.IdempotencyKey = strings.TrimSpace(command.IdempotencyKey)
	fields := lifecycleTransitionFields(
		command.UserID,
		command.DeviceID,
		command.TaskID,
		command.ClaimGeneration,
		command.ClaimToken,
		command.ExpectedVersion,
		command.IdempotencyKey,
	)
	if len(fields) > 0 {
		return ReleaseTaskResult{}, invalidError(
			"TASK_RELEASE_INVALID",
			"task release request is invalid",
			fields,
		)
	}
	event, err := service.newLifecycleEvent(
		command.UserID,
		command.DeviceID,
		command.TaskID,
		"TASK_RELEASED",
		"task released",
	)
	if err != nil {
		return ReleaseTaskResult{}, err
	}
	now := service.clock.Now().UTC()
	requestHash, err := lifecycleRequestHash(commandHashView{
		TaskID:          command.TaskID,
		ClaimGeneration: command.ClaimGeneration,
		ClaimTokenHash:  hashSecret(command.ClaimToken),
		ExpectedVersion: command.ExpectedVersion,
	})
	if err != nil {
		return ReleaseTaskResult{}, internalLifecycleFailure(err)
	}
	task, replayed, err := service.repository.ReleaseTask(
		ctx,
		ReleaseTaskRepositoryRequest{
			UserID:          command.UserID,
			DeviceID:        command.DeviceID,
			TaskID:          command.TaskID,
			ClaimGeneration: command.ClaimGeneration,
			ClaimTokenHash:  hashSecret(command.ClaimToken),
			ExpectedVersion: command.ExpectedVersion,
			IdempotencyKey:  command.IdempotencyKey,
			RequestHash:     requestHash,
			Now:             now,
			Event:           event,
		},
	)
	if err != nil {
		return ReleaseTaskResult{}, wrapLifecycleRepositoryError(err)
	}
	return ReleaseTaskResult{
		Task:       task,
		Replayed:   replayed,
		ServerTime: now,
	}, nil
}

func (service *LifecycleService) AcknowledgeCancellation(
	ctx context.Context,
	command AcknowledgeCancellationCommand,
) (AcknowledgeCancellationResult, error) {
	command.UserID = strings.TrimSpace(command.UserID)
	command.DeviceID = strings.TrimSpace(command.DeviceID)
	command.TaskID = strings.TrimSpace(command.TaskID)
	command.ExecutionID = strings.TrimSpace(command.ExecutionID)
	command.IdempotencyKey = strings.TrimSpace(command.IdempotencyKey)
	fields := lifecycleTransitionFields(
		command.UserID,
		command.DeviceID,
		command.TaskID,
		command.ClaimGeneration,
		command.ClaimToken,
		command.ExpectedVersion,
		command.IdempotencyKey,
	)
	if !isUUID(command.ExecutionID) {
		fields["execution_id"] = "must be a UUID"
	}
	if len(fields) > 0 {
		return AcknowledgeCancellationResult{}, invalidError(
			"TASK_CANCEL_ACK_INVALID",
			"task cancellation acknowledgement is invalid",
			fields,
		)
	}
	event, err := service.newLifecycleEvent(
		command.UserID,
		command.DeviceID,
		command.TaskID,
		"TASK_CANCELED",
		"task cancellation acknowledged",
	)
	if err != nil {
		return AcknowledgeCancellationResult{}, err
	}
	now := service.clock.Now().UTC()
	requestHash, err := lifecycleRequestHash(struct {
		commandHashView
		ExecutionID string `json:"execution_id"`
	}{
		commandHashView: commandHashView{
			TaskID:          command.TaskID,
			ClaimGeneration: command.ClaimGeneration,
			ClaimTokenHash:  hashSecret(command.ClaimToken),
			ExpectedVersion: command.ExpectedVersion,
		},
		ExecutionID: command.ExecutionID,
	})
	if err != nil {
		return AcknowledgeCancellationResult{},
			internalLifecycleFailure(err)
	}
	task, replayed, err := service.repository.AcknowledgeTaskCancellation(
		ctx,
		CancelAcknowledgementRepositoryRequest{
			UserID:          command.UserID,
			DeviceID:        command.DeviceID,
			TaskID:          command.TaskID,
			ExecutionID:     command.ExecutionID,
			ClaimGeneration: command.ClaimGeneration,
			ClaimTokenHash:  hashSecret(command.ClaimToken),
			ExpectedVersion: command.ExpectedVersion,
			IdempotencyKey:  command.IdempotencyKey,
			RequestHash:     requestHash,
			Now:             now,
			Event:           event,
		},
	)
	if err != nil {
		return AcknowledgeCancellationResult{},
			wrapLifecycleRepositoryError(err)
	}
	return AcknowledgeCancellationResult{
		Task:       task,
		Replayed:   replayed,
		ServerTime: now,
	}, nil
}

type commandHashView struct {
	TaskID          string `json:"task_id"`
	ClaimGeneration int64  `json:"claim_generation"`
	ClaimTokenHash  string `json:"claim_token_sha256"`
	ExpectedVersion int64  `json:"expected_version"`
}

func normalizeStartTaskCommand(command StartTaskCommand) StartTaskCommand {
	command.UserID = strings.TrimSpace(command.UserID)
	command.DeviceID = strings.TrimSpace(command.DeviceID)
	command.TaskID = strings.TrimSpace(command.TaskID)
	command.IdempotencyKey = strings.TrimSpace(command.IdempotencyKey)
	return command
}

func lifecycleWriteFields(
	userID string,
	deviceID string,
	idempotencyKey string,
	claimToken string,
) map[string]string {
	fields := lifecycleIdentityFields(userID, deviceID)
	validateIdempotencyField(fields, idempotencyKey)
	if !validOpaqueToken(claimToken) {
		fields["claim_token"] = "must be a 256-bit Raw URL value"
	}
	return fields
}

func lifecycleClaimFields(
	userID string,
	deviceID string,
	taskID string,
	claimGeneration int64,
	claimToken string,
) map[string]string {
	fields := lifecycleIdentityFields(userID, deviceID)
	if !isUUID(taskID) {
		fields["task_id"] = "must be a UUID"
	}
	if claimGeneration < 1 {
		fields["claim_generation"] = "must be positive"
	}
	if !validOpaqueToken(claimToken) {
		fields["claim_token"] = "must be a 256-bit Raw URL value"
	}
	return fields
}

func lifecycleTransitionFields(
	userID string,
	deviceID string,
	taskID string,
	claimGeneration int64,
	claimToken string,
	expectedVersion int64,
	idempotencyKey string,
) map[string]string {
	fields := lifecycleClaimFields(
		userID,
		deviceID,
		taskID,
		claimGeneration,
		claimToken,
	)
	if expectedVersion < 1 {
		fields["expected_version"] = "must be positive"
	}
	validateIdempotencyField(fields, idempotencyKey)
	return fields
}

func lifecycleIdentityFields(
	userID string,
	deviceID string,
) map[string]string {
	fields := make(map[string]string)
	if !isUUID(userID) {
		fields["user_id"] = "must be a UUID"
	}
	if !isUUID(deviceID) {
		fields["device_id"] = "must be a UUID"
	}
	return fields
}

func validateIdempotencyField(
	fields map[string]string,
	value string,
) {
	if value == "" ||
		len([]byte(value)) > maxIdempotencyKeyBytes ||
		!isPrintableASCII(value) {
		fields["idempotency_key"] = "invalid"
	}
}

func validateVersionField(
	fields map[string]string,
	name string,
	value string,
) {
	if value == "" {
		fields[name] = "required"
	} else if !utf8.ValidString(value) ||
		len([]byte(value)) > domain.MaxVersionBytes {
		fields[name] = "must be valid UTF-8 up to 128 bytes"
	}
}

func validLifecycleStep(value string) bool {
	if value == "" || len([]byte(value)) > maxLifecycleStepBytes {
		return false
	}
	for _, char := range value {
		if (char < 'A' || char > 'Z') &&
			(char < '0' || char > '9') &&
			char != '_' {
			return false
		}
	}
	return true
}

func lifecycleRequestHash(value any) (string, error) {
	encoded, err := json.Marshal(value)
	if err != nil {
		return "", err
	}
	sum := sha256.Sum256(encoded)
	return hex.EncodeToString(sum[:]), nil
}

func (service *LifecycleService) newLifecycleEvent(
	userID string,
	deviceID string,
	taskID string,
	eventType string,
	message string,
) (domain.TaskEvent, error) {
	id, err := service.ids.NewID()
	if err != nil {
		return domain.TaskEvent{}, internalLifecycleFailure(err)
	}
	actorUserID := userID
	actorDeviceID := deviceID
	return domain.TaskEvent{
		ID:            id,
		TaskID:        taskID,
		ActorUserID:   &actorUserID,
		ActorDeviceID: &actorDeviceID,
		Type:          eventType,
		Message:       message,
		OccurredAt:    service.clock.Now().UTC(),
	}, nil
}

func sameOptionalID(left, right *string) bool {
	if left == nil || strings.TrimSpace(*left) == "" {
		return right == nil
	}
	return right != nil && strings.TrimSpace(*left) == *right
}

func internalLifecycleFailure(err error) error {
	return newError(
		ErrorKindInternal,
		"INTERNAL_ERROR",
		"internal server error",
		err,
	)
}