/**
 * Request Coalescer
 * Batches and deduplicates operations to reduce S3 API calls
 * Automatically flushes based on size, time, or pressure
 */
import { createModuleLogger } from './logger.js';
/**
 * Coalesces multiple operations into efficient batches
 */
export class RequestCoalescer {
    constructor(processor, options) {
        this.logger = createModuleLogger('RequestCoalescer');
        // Operation queues by type
        this.writeQueue = new Map();
        this.readQueue = new Map();
        this.deleteQueue = new Map();
        // Batch configuration
        this.maxBatchSize = 100;
        this.maxBatchAge = 100; // ms - flush quickly under load
        this.minBatchSize = 10; // Don't flush until we have enough
        // Flush timers
        this.flushTimer = null;
        this.lastFlush = Date.now();
        // Statistics
        this.stats = {
            totalOperations: 0,
            coalescedOperations: 0,
            deduplicated: 0,
            batchesProcessed: 0,
            averageBatchSize: 0
        };
        this.processor = processor;
        if (options) {
            this.maxBatchSize = options.maxBatchSize || this.maxBatchSize;
            this.maxBatchAge = options.maxBatchAge || this.maxBatchAge;
            this.minBatchSize = options.minBatchSize || this.minBatchSize;
        }
    }
    /**
     * Add a write operation to be coalesced
     */
    async write(key, data) {
        return new Promise((resolve, reject) => {
            // Check if we already have a pending write for this key
            const existing = this.writeQueue.get(key);
            if (existing && existing.length > 0) {
                // Replace the data but resolve all promises
                const last = existing[existing.length - 1];
                last.data = data; // Use latest data
                // Add this promise to be resolved
                existing.push({
                    type: 'write',
                    key,
                    data,
                    resolve,
                    reject,
                    timestamp: Date.now()
                });
                this.stats.deduplicated++;
            }
            else {
                // New write operation
                this.writeQueue.set(key, [{
                        type: 'write',
                        key,
                        data,
                        resolve,
                        reject,
                        timestamp: Date.now()
                    }]);
            }
            this.stats.totalOperations++;
            this.checkFlush();
        });
    }
    /**
     * Add a read operation to be coalesced
     */
    async read(key) {
        return new Promise((resolve, reject) => {
            // Check if we already have a pending read for this key
            const existing = this.readQueue.get(key);
            if (existing && existing.length > 0) {
                // Coalesce with existing read
                existing.push({
                    type: 'read',
                    key,
                    resolve,
                    reject,
                    timestamp: Date.now()
                });
                this.stats.deduplicated++;
            }
            else {
                // New read operation
                this.readQueue.set(key, [{
                        type: 'read',
                        key,
                        resolve,
                        reject,
                        timestamp: Date.now()
                    }]);
            }
            this.stats.totalOperations++;
            this.checkFlush();
        });
    }
    /**
     * Add a delete operation to be coalesced
     */
    async delete(key) {
        return new Promise((resolve, reject) => {
            // Cancel any pending writes for this key
            if (this.writeQueue.has(key)) {
                const writes = this.writeQueue.get(key);
                writes.forEach(op => op.reject(new Error('Cancelled by delete')));
                this.writeQueue.delete(key);
                this.stats.deduplicated += writes.length;
            }
            // Cancel any pending reads for this key
            if (this.readQueue.has(key)) {
                const reads = this.readQueue.get(key);
                reads.forEach(op => op.resolve(null)); // Return null for deleted items
                this.readQueue.delete(key);
                this.stats.deduplicated += reads.length;
            }
            // Check if we already have a pending delete
            const existing = this.deleteQueue.get(key);
            if (existing && existing.length > 0) {
                // Coalesce with existing delete
                existing.push({
                    type: 'delete',
                    key,
                    resolve,
                    reject,
                    timestamp: Date.now()
                });
                this.stats.deduplicated++;
            }
            else {
                // New delete operation
                this.deleteQueue.set(key, [{
                        type: 'delete',
                        key,
                        resolve,
                        reject,
                        timestamp: Date.now()
                    }]);
            }
            this.stats.totalOperations++;
            this.checkFlush();
        });
    }
    /**
     * Check if we should flush the queues
     */
    checkFlush() {
        const totalSize = this.writeQueue.size + this.readQueue.size + this.deleteQueue.size;
        const now = Date.now();
        const age = now - this.lastFlush;
        // Immediate flush conditions
        if (totalSize >= this.maxBatchSize) {
            this.flush('size_limit');
            return;
        }
        // Age-based flush
        if (age >= this.maxBatchAge && totalSize >= this.minBatchSize) {
            this.flush('age_limit');
            return;
        }
        // Schedule a flush if not already scheduled
        if (!this.flushTimer && totalSize > 0) {
            const delay = Math.max(10, this.maxBatchAge - age);
            this.flushTimer = setTimeout(() => {
                this.flush('timer');
            }, delay);
        }
    }
    /**
     * Flush all queued operations
     */
    async flush(reason = 'manual') {
        // Clear timer
        if (this.flushTimer) {
            clearTimeout(this.flushTimer);
            this.flushTimer = null;
        }
        // Collect all operations into a single batch
        const batch = [];
        // Process deletes first (highest priority)
        this.deleteQueue.forEach((ops) => {
            // Only take the first operation per key (others are duplicates)
            if (ops.length > 0) {
                batch.push(ops[0]);
                this.stats.coalescedOperations += ops.length;
            }
        });
        // Then writes
        this.writeQueue.forEach((ops) => {
            if (ops.length > 0) {
                // Use the last write (most recent data)
                const lastWrite = ops[ops.length - 1];
                batch.push(lastWrite);
                this.stats.coalescedOperations += ops.length;
            }
        });
        // Then reads
        this.readQueue.forEach((ops) => {
            if (ops.length > 0) {
                batch.push(ops[0]);
                this.stats.coalescedOperations += ops.length;
            }
        });
        // Clear queues
        const allOps = [
            ...Array.from(this.deleteQueue.values()).flat(),
            ...Array.from(this.writeQueue.values()).flat(),
            ...Array.from(this.readQueue.values()).flat()
        ];
        this.deleteQueue.clear();
        this.writeQueue.clear();
        this.readQueue.clear();
        if (batch.length === 0) {
            return;
        }
        // Update stats
        this.stats.batchesProcessed++;
        this.stats.averageBatchSize =
            (this.stats.averageBatchSize * (this.stats.batchesProcessed - 1) + batch.length) /
                this.stats.batchesProcessed;
        this.logger.debug(`Flushing batch of ${batch.length} operations (${allOps.length} total) - reason: ${reason}`);
        // Process the batch
        try {
            await this.processor(batch);
            // Resolve all promises
            allOps.forEach(op => {
                if (op.type === 'read') {
                    // Find the result for this read
                    const result = batch.find(b => b.key === op.key && b.type === 'read');
                    op.resolve(result?.data || null);
                }
                else {
                    op.resolve(undefined);
                }
            });
        }
        catch (error) {
            // Reject all promises
            allOps.forEach(op => op.reject(error));
            this.logger.error('Batch processing failed:', error);
        }
        this.lastFlush = Date.now();
    }
    /**
     * Get current statistics
     */
    getStats() {
        return { ...this.stats };
    }
    /**
     * Get current queue sizes
     */
    getQueueSizes() {
        return {
            writes: this.writeQueue.size,
            reads: this.readQueue.size,
            deletes: this.deleteQueue.size,
            total: this.writeQueue.size + this.readQueue.size + this.deleteQueue.size
        };
    }
    /**
     * Adjust batch parameters based on load
     */
    adjustParameters(pending) {
        if (pending > 10000) {
            // Extreme load - batch aggressively
            this.maxBatchSize = 500;
            this.maxBatchAge = 50;
            this.minBatchSize = 50;
        }
        else if (pending > 1000) {
            // High load - larger batches
            this.maxBatchSize = 200;
            this.maxBatchAge = 100;
            this.minBatchSize = 20;
        }
        else if (pending > 100) {
            // Moderate load
            this.maxBatchSize = 100;
            this.maxBatchAge = 200;
            this.minBatchSize = 10;
        }
        else {
            // Low load - optimize for latency
            this.maxBatchSize = 50;
            this.maxBatchAge = 500;
            this.minBatchSize = 5;
        }
    }
    /**
     * Force immediate flush of all operations
     */
    async forceFlush() {
        await this.flush('force');
    }
}
// Global coalescer instances by storage type
const coalescers = new Map();
/**
 * Get or create a coalescer for a storage instance
 */
export function getCoalescer(storageId, processor) {
    if (!coalescers.has(storageId)) {
        coalescers.set(storageId, new RequestCoalescer(processor));
    }
    return coalescers.get(storageId);
}
/**
 * Clear all coalescers
 */
export function clearCoalescers() {
    coalescers.clear();
}
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