Permify / permify

import (

	"context"

	"fmt"

	"sort"

	"sync"

	"sync/atomic"

	"github.com/pkg/errors"

	"golang.org/x/sync/errgroup"

	"golang.org/x/sync/semaphore"

	"github.com/Permify/permify/internal/invoke"

	"github.com/Permify/permify/internal/storage/memory/utils"

	base "github.com/Permify/permify/pkg/pb/base/v1"

)

// BulkCheckerType defines the type of bulk checking operation.

// This enum determines how requests are sorted and processed.

type BulkCheckerType string

const (

	// BulkCheckerTypeSubject indicates that requests should be sorted and processed by subject ID

	BulkCheckerTypeSubject BulkCheckerType = "subject"

	// BulkCheckerTypeEntity indicates that requests should be sorted and processed by entity ID

	BulkCheckerTypeEntity BulkCheckerType = "entity"

)

// BulkCheckerRequest represents a permission check request with optional pre-computed result.

// This struct encapsulates both the permission check request and an optional pre-determined result,

// allowing for optimization when results are already known (e.g., from caching).

type BulkCheckerRequest struct {

	// Request contains the actual permission check request

	Request *base.PermissionCheckRequest

	// Result holds a pre-computed result if available, otherwise CHECK_RESULT_UNSPECIFIED

	Result base.CheckResult

}

// BulkCheckerConfig holds configuration parameters for the BulkChecker.

// This struct allows for fine-tuning the behavior and performance characteristics

// of the bulk permission checking system.

type BulkCheckerConfig struct {

	// ConcurrencyLimit defines the maximum number of concurrent permission checks

	// that can be processed simultaneously. Higher values increase throughput

	// but may consume more system resources.

	ConcurrencyLimit int

	// BufferSize defines the size of the internal request buffer.

	// This should be set based on expected request volume to avoid blocking.

	BufferSize int

}

// DefaultBulkCheckerConfig returns a sensible default configuration

// that balances performance and resource usage for most use cases.

func DefaultBulkCheckerConfig() BulkCheckerConfig {

	return BulkCheckerConfig{

		ConcurrencyLimit: 10,   // Moderate concurrency for most workloads

		BufferSize:       1000, // Buffer for 1000 requests

	}

}

// BulkChecker handles concurrent permission checks with ordered result processing.

// This struct implements a high-performance bulk permission checking system that:

// - Collects permission check requests asynchronously

// - Processes them concurrently with controlled parallelism

// - Maintains strict ordering of results based on request sorting

// - Provides efficient resource management and error handling

type BulkChecker struct {

	// typ determines the sorting strategy and processing behavior

	typ BulkCheckerType

	// checker is the underlying permission checking engine

	checker invoke.Check

	// config holds the operational configuration

	config BulkCheckerConfig

	// ctx provides context for cancellation and timeout management

	ctx context.Context

	// cancel allows for graceful shutdown of all operations

	cancel context.CancelFunc

	// Request handling components

	// requestChan is the input channel for receiving permission check requests

	requestChan chan BulkCheckerRequest

	// requests stores all collected requests before processing

	requests []BulkCheckerRequest

	// requestsMu provides thread-safe access to the requests slice

	requestsMu sync.RWMutex

	// Execution state management

	// executionState tracks the progress and results of request processing

	executionState *executionState

	// collectionDone signals when request collection has completed

	collectionDone chan struct{}

	// Callback for processing results

	// callback is invoked for each successful permission check with the entity/subject ID and continuous token

	callback func(entityID, continuousToken string)

}

// executionState manages the execution of requests and maintains processing order.

// This struct ensures that results are processed in the correct sequence

// even when requests complete out of order due to concurrent processing.

type executionState struct {

	// mu protects access to the execution state

	mu sync.Mutex

	// results stores the results of all requests in their original order

	results []base.CheckResult

	// processedIndex tracks the next result to be processed in order

	processedIndex int

	// successCount tracks the number of successful permission checks

	successCount int64

	// limit defines the maximum number of successful results to process

	limit int64

}

// NewBulkChecker creates a new BulkChecker instance with comprehensive validation and error handling.

// This constructor ensures that all dependencies are properly initialized and validates

// configuration parameters to prevent runtime errors.

//

// Parameters:

//   - ctx: Context for managing the lifecycle of the BulkChecker

//   - checker: The permission checking engine to use for actual permission checks

//   - typ: The type of bulk checking operation (entity or subject)

//   - callback: Function called for each successful permission check

//   - config: Configuration parameters for tuning performance and behavior

//

// Returns:

//   - *BulkChecker: The initialized BulkChecker instance

//   - error: Any error that occurred during initialization

func NewBulkChecker(ctx context.Context, checker invoke.Check, typ BulkCheckerType, callback func(entityID, ct string), config BulkCheckerConfig) (*BulkChecker, error) {

	// Validate all required parameters

	if ctx == nil {

		return nil, fmt.Errorf("context cannot be nil")

	}

	if checker == nil {

		return nil, fmt.Errorf("checker cannot be nil")

	}

	if callback == nil {

		return nil, fmt.Errorf("callback cannot be nil")

	}

	// Apply default values for invalid configuration

	if config.ConcurrencyLimit <= 0 {

		config.ConcurrencyLimit = DefaultBulkCheckerConfig().ConcurrencyLimit

	}

	if config.BufferSize <= 0 {

		config.BufferSize = DefaultBulkCheckerConfig().BufferSize

	}

	// Create a cancellable context for the BulkChecker

	ctx, cancel := context.WithCancel(ctx)

	// Initialize the BulkChecker with all components

	bc := &BulkChecker{

		typ:            typ,

		checker:        checker,

		config:         config,

		ctx:            ctx,

		cancel:         cancel,

		requestChan:    make(chan BulkCheckerRequest, config.BufferSize),

		requests:       make([]BulkCheckerRequest, 0, config.BufferSize),

		callback:       callback,

		collectionDone: make(chan struct{}),

	}

	// Start the background request collection goroutine

	go bc.collectRequests()

	return bc, nil

}

// collectRequests safely collects requests until the channel is closed.

// This method runs in a separate goroutine and continuously processes

// incoming requests until either the channel is closed or the context is cancelled.

// It ensures thread-safe addition of requests to the internal collection.

func (bc *BulkChecker) collectRequests() {

	// Signal completion when this goroutine exits

	defer close(bc.collectionDone)

	for {

		select {

		case req, ok := <-bc.requestChan:

			if !ok {

				// Channel closed, stop collecting

				return

			}

			bc.addRequest(req)

		case <-bc.ctx.Done():

			// Context cancelled, stop collecting

			return

		}

	}

}

// addRequest safely adds a request to the internal list.

// This method uses a mutex to ensure thread-safe access to the requests slice,

// preventing race conditions when multiple goroutines are adding requests.

func (bc *BulkChecker) addRequest(req BulkCheckerRequest) {

	bc.requestsMu.Lock()

	defer bc.requestsMu.Unlock()

	bc.requests = append(bc.requests, req)

}

// StopCollectingRequests safely stops request collection and waits for completion.

// This method closes the input channel and waits for the collection goroutine

// to finish processing any remaining requests. This ensures that no requests

// are lost during shutdown.

func (bc *BulkChecker) StopCollectingRequests() {

	close(bc.requestChan)

	<-bc.collectionDone // Wait for collection to complete

}

// getSortedRequests returns a sorted copy of requests based on the checker type.

// This method creates a copy of the requests to avoid modifying the original

// collection and sorts them according to the BulkCheckerType (entity ID or subject ID).

// The sorting ensures consistent and predictable result ordering.

func (bc *BulkChecker) getSortedRequests() []BulkCheckerRequest {

	bc.requestsMu.RLock()

	defer bc.requestsMu.RUnlock()

	// Create a copy to avoid modifying the original

	requests := make([]BulkCheckerRequest, len(bc.requests))

	copy(requests, bc.requests)

	// Sort the copy based on the checker type

	bc.sortRequests(requests)

	return requests

}

// sortRequests sorts requests based on the checker type.

// This method implements different sorting strategies:

// - For entity-based checks: sorts by entity ID

// - For subject-based checks: sorts by subject ID

// The sorting ensures that results are processed in a consistent order.

func (bc *BulkChecker) sortRequests(requests []BulkCheckerRequest) {

	switch bc.typ {

	case BulkCheckerTypeEntity:

		sort.Slice(requests, func(i, j int) bool {

			return requests[i].Request.GetEntity().GetId() < requests[j].Request.GetEntity().GetId()

		})

	case BulkCheckerTypeSubject:

		sort.Slice(requests, func(i, j int) bool {

			return requests[i].Request.GetSubject().GetId() < requests[j].Request.GetSubject().GetId()

		})

	}

}

// ExecuteRequests processes requests concurrently with comprehensive error handling and resource management.

// This method is the main entry point for bulk permission checking. It:

// 1. Stops collecting new requests

// 2. Sorts all collected requests

// 3. Processes them concurrently with controlled parallelism

// 4. Maintains strict ordering of results

// 5. Handles errors gracefully and manages resources properly

//

// Parameters:

//   - size: The maximum number of successful results to process

//

// Returns:

//   - error: Any error that occurred during processing (context cancellation is not considered an error)

func (bc *BulkChecker) ExecuteRequests(size uint32) error {

	if size == 0 {

		return fmt.Errorf("size must be greater than 0")

	}

	// Stop collecting new requests and wait for collection to complete

	bc.StopCollectingRequests()

	// Get sorted requests for processing

	requests := bc.getSortedRequests()

	if len(requests) == 0 {

		return nil // No requests to process

	}

	// Initialize execution state for tracking progress

	bc.executionState = &executionState{

		results: make([]base.CheckResult, len(requests)),

		limit:   int64(size),

	}

	// Create execution context with cancellation for graceful shutdown

	execCtx, execCancel := context.WithCancel(bc.ctx)

	defer execCancel()

	// Create semaphore to control concurrency

	sem := semaphore.NewWeighted(int64(bc.config.ConcurrencyLimit))

	// Create error group for managing goroutines and error propagation

	g, ctx := errgroup.WithContext(execCtx)

	// Process requests concurrently

	for i, req := range requests {

		// Check if we've reached the success limit

		if atomic.LoadInt64(&bc.executionState.successCount) >= int64(size) {

			break

		}

		index := i

		request := req

		// Launch goroutine for each request

		g.Go(func() error {

			return bc.processRequest(ctx, sem, index, request)

		})

	}

	// Wait for all goroutines to complete and handle any errors

	if err := g.Wait(); err != nil {

		if isContextError(err) {

			return nil // Context cancellation is not an error

		}

	}

	return nil

}

// processRequest handles a single request with comprehensive error handling.

// This method is executed in a separate goroutine for each request and:

// 1. Acquires a semaphore slot to control concurrency

// 2. Performs the permission check or uses pre-computed result

// 3. Processes the result in the correct order

// 4. Handles context cancellation and other errors gracefully

//

// Parameters:

//   - ctx: Context for cancellation and timeout

//   - sem: Semaphore for concurrency control

//   - index: The index of this request in the sorted list

//   - req: The permission check request to process

//

// Returns:

//   - error: Any error that occurred during processing

func (bc *BulkChecker) processRequest(ctx context.Context, sem *semaphore.Weighted, index int, req BulkCheckerRequest) error {

	// Check context before acquiring semaphore

	if err := ctx.Err(); err != nil {

		return nil

	}

	// Acquire semaphore slot to control concurrency

	if err := sem.Acquire(ctx, 1); err != nil {

		if isContextError(err) {

			return nil

		}

	}

	defer sem.Release(1)

	// Determine the result for this request

	result, err := bc.getRequestResult(ctx, req)

	if err != nil {

		if isContextError(err) {

			return nil

		}

	}

	// Process the result in the correct order

	return bc.processResult(index, result)

}

// getRequestResult determines the result for a request.

// This method either uses a pre-computed result if available,

// or performs the actual permission check using the underlying checker.

//

// Parameters:

//   - ctx: Context for the permission check

//   - req: The request to get the result for

//

// Returns:

//   - base.CheckResult: The result of the permission check

//   - error: Any error that occurred during the check

func (bc *BulkChecker) getRequestResult(ctx context.Context, req BulkCheckerRequest) (base.CheckResult, error) {

	// Use pre-computed result if available

	if req.Result != base.CheckResult_CHECK_RESULT_UNSPECIFIED {

		return req.Result, nil

	}

	// Perform the actual permission check

	response, err := bc.checker.Check(ctx, req.Request)

	if err != nil {

		return base.CheckResult_CHECK_RESULT_UNSPECIFIED, err

	}

	return response.GetCan(), nil

}

// processResult processes a single result with thread-safe state updates.

// This method ensures that results are processed in the correct order

// even when requests complete out of order due to concurrent processing.

// It maintains the execution state and calls the callback for successful results.

//

// Parameters:

//   - index: The index of the result in the sorted list

//   - result: The result of the permission check

//

// Returns:

//   - error: Any error that occurred during processing

func (bc *BulkChecker) processResult(index int, result base.CheckResult) error {

	bc.executionState.mu.Lock()

	defer bc.executionState.mu.Unlock()

	// Store the result at the correct index

	bc.executionState.results[index] = result

	// Process results in order, starting from the current processed index

	for bc.executionState.processedIndex < len(bc.executionState.results) {

		currentResult := bc.executionState.results[bc.executionState.processedIndex]

		if currentResult == base.CheckResult_CHECK_RESULT_UNSPECIFIED {

			break // Wait for this result to be computed

		}

		// Process successful results

		if currentResult == base.CheckResult_CHECK_RESULT_ALLOWED {

			// Check if we've reached the success limit

			if atomic.LoadInt64(&bc.executionState.successCount) >= bc.executionState.limit {

				return nil

			}

			// Increment success count and call callback

			atomic.AddInt64(&bc.executionState.successCount, 1)

			bc.callbackWithToken(bc.executionState.processedIndex)

		}

		// Move to the next result

		bc.executionState.processedIndex++

	}

	return nil

}

// callbackWithToken calls the callback with the appropriate entity/subject ID and continuous token.

// This method retrieves the correct request from the sorted list and generates

// the appropriate continuous token for pagination support.

//

// Parameters:

//   - index: The index of the result in the sorted list

func (bc *BulkChecker) callbackWithToken(index int) {

	requests := bc.getSortedRequests()

	// Validate index bounds

	if index >= len(requests) {

		return

	}

	var id string

	var ct string

	// Extract ID and generate continuous token based on checker type

	switch bc.typ {

	case BulkCheckerTypeEntity:

		id = requests[index].Request.GetEntity().GetId()

		if index+1 < len(requests) {

			ct = utils.NewContinuousToken(requests[index+1].Request.GetEntity().GetId()).Encode().String()

		}

	case BulkCheckerTypeSubject:

		id = requests[index].Request.GetSubject().GetId()

		if index+1 < len(requests) {

			ct = utils.NewContinuousToken(requests[index+1].Request.GetSubject().GetId()).Encode().String()

		}

	}

	// Call the user-provided callback

	bc.callback(id, ct)

}

// Close properly cleans up resources and cancels all operations.

// This method should be called when the BulkChecker is no longer needed

// to ensure proper resource cleanup and prevent goroutine leaks.

//

// Returns:

//   - error: Any error that occurred during cleanup

func (bc *BulkChecker) Close() error {

	bc.cancel()

	return nil

}

// BulkEntityPublisher handles entity-based permission check publishing.

// This struct provides a convenient interface for publishing entity permission

// check requests to a BulkChecker instance.

type BulkEntityPublisher struct {

	// bulkChecker is the target BulkChecker for publishing requests

	bulkChecker *BulkChecker

	// request contains the base lookup request parameters

	request *base.PermissionLookupEntityRequest

}

// NewBulkEntityPublisher creates a new BulkEntityPublisher instance.

// This constructor initializes a publisher for entity-based permission checks.

//

// Parameters:

//   - ctx: Context for the publisher (currently unused but kept for API consistency)

//   - request: The base lookup request containing common parameters

//   - bulkChecker: The BulkChecker instance to publish to

//

// Returns:

//   - *BulkEntityPublisher: The initialized publisher instance

func NewBulkEntityPublisher(ctx context.Context, request *base.PermissionLookupEntityRequest, bulkChecker *BulkChecker) *BulkEntityPublisher {

	return &BulkEntityPublisher{

		bulkChecker: bulkChecker,

		request:     request,

	}

}

// Publish sends an entity permission check request to the bulk checker.

// This method creates a permission check request from the provided parameters

// and sends it to the BulkChecker for processing. It handles context cancellation

// gracefully by dropping requests when the context is done.

//

// Parameters:

//   - entity: The entity to check permissions for

//   - metadata: Metadata for the permission check request

//   - context: Additional context for the permission check

//   - result: Optional pre-computed result

func (p *BulkEntityPublisher) Publish(entity *base.Entity, metadata *base.PermissionCheckRequestMetadata, context *base.Context, result base.CheckResult) {

	select {

	case p.bulkChecker.requestChan <- BulkCheckerRequest{

		Request: &base.PermissionCheckRequest{

			TenantId:   p.request.GetTenantId(),

			Metadata:   metadata,

			Entity:     entity,

			Permission: p.request.GetPermission(),

			Subject:    p.request.GetSubject(),

			Context:    context,

		},

		Result: result,

	}:

	case <-p.bulkChecker.ctx.Done():

		// Context cancelled, drop the request

	}

}

// BulkSubjectPublisher handles subject-based permission check publishing.

// This struct provides a convenient interface for publishing subject permission

// check requests to a BulkChecker instance.

type BulkSubjectPublisher struct {

	// bulkChecker is the target BulkChecker for publishing requests

	bulkChecker *BulkChecker

	// request contains the base lookup request parameters

	request *base.PermissionLookupSubjectRequest

}

// NewBulkSubjectPublisher creates a new BulkSubjectPublisher instance.

// This constructor initializes a publisher for subject-based permission checks.

//

// Parameters:

//   - ctx: Context for the publisher (currently unused but kept for API consistency)

//   - request: The base lookup request containing common parameters

//   - bulkChecker: The BulkChecker instance to publish to

//

// Returns:

//   - *BulkSubjectPublisher: The initialized publisher instance

func NewBulkSubjectPublisher(ctx context.Context, request *base.PermissionLookupSubjectRequest, bulkChecker *BulkChecker) *BulkSubjectPublisher {

	return &BulkSubjectPublisher{

		bulkChecker: bulkChecker,

		request:     request,

	}

}

// Publish sends a subject permission check request to the bulk checker.

// This method creates a permission check request from the provided parameters

// and sends it to the BulkChecker for processing. It handles context cancellation

// gracefully by dropping requests when the context is done.

//

// Parameters:

//   - subject: The subject to check permissions for

//   - metadata: Metadata for the permission check request

//   - context: Additional context for the permission check

//   - result: Optional pre-computed result

	}

}

// isContextError checks if an error is related to context cancellation or timeout.

// This helper function centralizes the logic for identifying context-related errors

// that should not be treated as actual errors in the bulk processing system.

//

// Parameters:

//   - err: The error to check

//

// Returns:

//   - bool: True if the error is context-related, false otherwise

func isContextError(err error) bool {

	return errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded)

}

// IsContextRelatedError is a legacy function maintained for backward compatibility.

// This function provides the same functionality as isContextError but with

// the original signature to maintain compatibility with existing code.

//

// Parameters:

//   - ctx: Context (unused, kept for compatibility)

//   - err: The error to check

//

// Returns:

//   - bool: True if the error is context-related, false otherwise

func IsContextRelatedError(ctx context.Context, err error) bool {

	return isContextError(err)

}