/**
 * Comprehensive tests for BlobStorage (src/storage/blobStorage.ts)
 *
 * Tests:
 * - Content-addressable storage (SHA-256, integrity verification)
 * - Deduplication via reference counting
 * - Compression (zstd, MIME-aware auto mode)
 * - LRU caching (bounded cache still serves correct bytes)
 * - Reference counting + delete-at-zero
 * - Error handling
 * - Performance characteristics
 * - Wrapped-binary-data regressions (key-based dispatch)
 *
 * Cache-bypass pattern: the store has no cache-introspection API (the LRU is
 * an internal optimization), so tests that must force a storage read create a
 * FRESH BlobStorage over the same adapter — a cold cache by construction.
 */

import { describe, it, expect, beforeEach } from 'vitest'
import { BlobStorage, BlobStoreAdapter } from '../../../src/storage/blobStorage.js'

/**
 * Simple in-memory blob store adapter for testing
 */
class InMemoryBlobAdapter implements BlobStoreAdapter {
  private store = new Map<string, Buffer>()

  async get(key: string): Promise<Buffer | undefined> {
    return this.store.get(key)
  }

  async put(key: string, data: Buffer): Promise<void> {
    this.store.set(key, data)
  }

  async delete(key: string): Promise<void> {
    this.store.delete(key)
  }

  async list(prefix: string): Promise<string[]> {
    const keys: string[] = []
    for (const key of this.store.keys()) {
      if (key.startsWith(prefix)) {
        keys.push(key)
      }
    }
    return keys.sort()
  }
}

describe('BlobStorage', () => {
  let adapter: BlobStoreAdapter
  let blobStorage: BlobStorage

  beforeEach(() => {
    adapter = new InMemoryBlobAdapter()
    blobStorage = new BlobStorage(adapter)
  })

  describe('Content-Addressable Storage', () => {
    it('should compute SHA-256 hash of data', () => {
      const data = Buffer.from('hello world')
      const hash = BlobStorage.hash(data)

      expect(hash).toBe('b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9')
      expect(hash).toHaveLength(64)
    })

    it('should write blob and return hash', async () => {
      const data = Buffer.from('test data')
      const hash = await blobStorage.write(data)

      expect(hash).toBeTruthy()
      expect(hash).toHaveLength(64)
    })

    it('should read blob by hash', async () => {
      const data = Buffer.from('test data')
      const hash = await blobStorage.write(data)

      const retrieved = await blobStorage.read(hash)

      expect(retrieved.toString()).toBe('test data')
    })

    it('should verify data integrity on read', async () => {
      const data = Buffer.from('test data')
      const hash = await blobStorage.write(data)

      // Corrupt the blob data behind the store's back
      await adapter.put(`blob:${hash}`, Buffer.from('corrupted'))

      // A fresh instance has a cold cache, so read() must hit storage and
      // detect the corruption via hash verification.
      const coldStore = new BlobStorage(adapter)
      await expect(coldStore.read(hash)).rejects.toThrow('integrity check failed')
    })

    it('should check if blob exists', async () => {
      const data = Buffer.from('test data')
      const hash = await blobStorage.write(data)

      expect(await blobStorage.has(hash)).toBe(true)
      expect(await blobStorage.has('0'.repeat(64))).toBe(false)
    })
  })

  describe('Deduplication', () => {
    it('should deduplicate identical blobs', async () => {
      const data = Buffer.from('duplicate data')

      const hash1 = await blobStorage.write(data)
      const hash2 = await blobStorage.write(data)

      expect(hash1).toBe(hash2)

      // Exactly one stored blob + one metadata record
      expect(await adapter.list('blob:')).toHaveLength(1)
      expect(await adapter.list('blob-meta:')).toHaveLength(1)
    })

    it('should increment ref count on duplicate write', async () => {
      const data = Buffer.from('test data')

      await blobStorage.write(data)
      const hash = await blobStorage.write(data)

      const metadata = await blobStorage.getMetadata(hash)
      expect(metadata?.refCount).toBe(2)
    })

    it('should track every duplicate write in the reference count', async () => {
      const data = Buffer.from('x'.repeat(1000))

      const hash1 = await blobStorage.write(data)
      const hash2 = await blobStorage.write(data)
      const hash3 = await blobStorage.write(data)

      expect(hash2).toBe(hash1)
      expect(hash3).toBe(hash1)
      const metadata = await blobStorage.getMetadata(hash1)
      expect(metadata?.refCount).toBe(3)
    })
  })

  describe('Compression', () => {
    it('should compress large text data with zstd', async () => {
      const data = Buffer.from('a'.repeat(10000))

      const hash = await blobStorage.write(data, { compression: 'zstd' })

      const metadata = await blobStorage.getMetadata(hash)

      // zstd may not be available in test environment - falls back to 'none'
      // This is expected behavior (see BlobStorage.ensureCompressionReady fallback)
      if (metadata?.compression === 'zstd') {
        expect(metadata.compressedSize).toBeLessThan(metadata.size)
      } else {
        // Fallback to 'none' is acceptable when zstd unavailable
        expect(metadata?.compression).toBe('none')
      }
    })

    it('should decompress zstd data on read', async () => {
      const originalData = Buffer.from('test data '.repeat(100))

      const hash = await blobStorage.write(originalData, { compression: 'zstd' })

      const retrieved = await blobStorage.read(hash)

      expect(retrieved.toString()).toBe(originalData.toString())
    })

    it('should not compress small blobs', async () => {
      const data = Buffer.from('small')

      const hash = await blobStorage.write(data, { compression: 'auto' })

      const metadata = await blobStorage.getMetadata(hash)

      expect(metadata?.compression).toBe('none')
    })

    it('should skip compression for already-compressed MIME types in auto mode', async () => {
      const data = Buffer.from('x'.repeat(5000))

      const hash = await blobStorage.write(data, {
        compression: 'auto',
        mimeType: 'image/jpeg'
      })

      const metadata = await blobStorage.getMetadata(hash)
      expect(metadata?.compression).toBe('none')
    })

    it('should auto-compress large compressible payloads', async () => {
      const data = Buffer.from('x'.repeat(5000))

      const hash = await blobStorage.write(data, { compression: 'auto' })

      const metadata = await blobStorage.getMetadata(hash)

      // Should compress if zstd is available
      if (metadata?.compression === 'zstd') {
        expect(metadata.compressedSize).toBeLessThan(metadata.size)
      }
    })
  })

  describe('LRU Caching', () => {
    it('should serve identical bytes from cache and from storage', async () => {
      const data = Buffer.from('cached data')
      const hash = await blobStorage.write(data)

      // Warm read (write-through cache) and cold read (fresh instance)
      const warm = await blobStorage.read(hash)
      const cold = await new BlobStorage(adapter).read(hash)

      expect(warm.equals(data)).toBe(true)
      expect(cold.equals(data)).toBe(true)
    })

    it('should keep serving correct bytes when the cache evicts under pressure', async () => {
      const smallCache = new BlobStorage(adapter, { cacheMaxSize: 100 })

      // Write blobs that exceed cache size (forces LRU eviction)
      const blobs = [
        Buffer.from('x'.repeat(50)),
        Buffer.from('y'.repeat(50)),
        Buffer.from('z'.repeat(50))
      ]
      const hashes: string[] = []
      for (const blob of blobs) {
        hashes.push(await smallCache.write(blob))
      }

      // Every blob still reads back correctly, evicted or not
      for (let i = 0; i < blobs.length; i++) {
        const retrieved = await smallCache.read(hashes[i])
        expect(retrieved.equals(blobs[i])).toBe(true)
      }
    })
  })

  describe('Reference Counting', () => {
    it('should track reference count', async () => {
      const data = Buffer.from('test')

      const hash = await blobStorage.write(data)

      let metadata = await blobStorage.getMetadata(hash)
      expect(metadata?.refCount).toBe(1)

      // Write duplicate (increments ref count)
      await blobStorage.write(data)

      metadata = await blobStorage.getMetadata(hash)
      expect(metadata?.refCount).toBe(2)
    })

    it('should only delete when refCount reaches 0', async () => {
      const data = Buffer.from('test')

      // Write twice (refCount = 2)
      const hash = await blobStorage.write(data)
      await blobStorage.write(data)

      // Delete once (refCount = 1, blob still exists)
      await blobStorage.delete(hash)

      expect(await blobStorage.has(hash)).toBe(true)

      // Delete again (refCount = 0, blob deleted)
      await blobStorage.delete(hash)

      expect(await blobStorage.has(hash)).toBe(false)
    })
  })

  describe('Metadata', () => {
    it('should store blob metadata', async () => {
      const data = Buffer.from('test')

      const hash = await blobStorage.write(data, { compression: 'none' })

      const metadata = await blobStorage.getMetadata(hash)

      expect(metadata?.hash).toBe(hash)
      expect(metadata?.size).toBe(data.length)
      expect(metadata?.compression).toBe('none')
      expect(metadata?.createdAt).toBeGreaterThan(0)
      expect(metadata?.refCount).toBe(1)
    })

    it('should return undefined metadata for unknown hashes', async () => {
      expect(await blobStorage.getMetadata('f'.repeat(64))).toBeUndefined()
    })
  })

  describe('Error Handling', () => {
    it('should throw on reading non-existent blob', async () => {
      await expect(
        blobStorage.read('f'.repeat(64))
      ).rejects.toThrow('Blob metadata not found')
    })

    it('should throw on reading blob with missing metadata', async () => {
      const data = Buffer.from('test')
      const hash = await blobStorage.write(data)

      // Delete metadata but keep blob bytes
      await adapter.delete(`blob-meta:${hash}`)

      // A fresh instance has a cold cache, so read() must consult metadata
      const coldStore = new BlobStorage(adapter)
      await expect(coldStore.read(hash)).rejects.toThrow('metadata not found')
    })
  })

  describe('Performance', () => {
    it('should write 1000 small blobs quickly', async () => {
      const start = Date.now()

      for (let i = 0; i < 1000; i++) {
        await blobStorage.write(Buffer.from(`blob${i}`))
      }

      const elapsed = Date.now() - start

      expect(elapsed).toBeLessThan(5000)  // Should complete in < 5s
    })

    it('should read 1000 cached blobs very quickly', async () => {
      // Write and cache blobs
      const hashes: string[] = []
      for (let i = 0; i < 1000; i++) {
        const hash = await blobStorage.write(Buffer.from(`blob${i}`))
        hashes.push(hash)
      }

      // First read (populate cache)
      for (const hash of hashes) {
        await blobStorage.read(hash)
      }

      // Second read (from cache)
      const start = Date.now()
      for (const hash of hashes) {
        await blobStorage.read(hash)
      }
      const elapsed = Date.now() - start

      expect(elapsed).toBeLessThan(1000)  // Should be very fast from cache
    })
  })

  describe('Wrapped-binary regression (v5.10.0) - hash verification on unwrapped bytes', () => {
    it('should handle wrapped binary data without hash mismatch', async () => {
      // Import TestWrappingAdapter that actually wraps data like production
      const { TestWrappingAdapter } = await import('../../helpers/TestWrappingAdapter.js')
      const wrappingAdapter = new TestWrappingAdapter()
      const testBlobStorage = new BlobStorage(wrappingAdapter)

      const originalData = Buffer.from('test content for v5.10.0 regression test')

      // Write blob (TestWrappingAdapter wraps as {_binary: true, data: "base64..."})
      const hash = await testBlobStorage.write(originalData)

      // Fresh instance = cold cache: read() must fetch + unwrap from storage.
      // v5.10.0 bug: read() hashed the wrapped bytes instead of the unwrapped
      // content; the fix runs unwrapBinaryData() before hash verification.
      const retrieved = await new BlobStorage(wrappingAdapter).read(hash)

      expect(retrieved.equals(originalData)).toBe(true)
      expect(retrieved.toString()).toBe('test content for v5.10.0 regression test')
    })

    it('should handle multiple wrapped blobs without integrity errors', async () => {
      const { TestWrappingAdapter } = await import('../../helpers/TestWrappingAdapter.js')
      const wrappingAdapter = new TestWrappingAdapter()
      const testBlobStorage = new BlobStorage(wrappingAdapter)

      const testData = [
        Buffer.from('first blob'),
        Buffer.from('second blob'),
        Buffer.from('third blob with more content'),
        Buffer.from(JSON.stringify({ test: 'json data' })),
      ]

      const hashes: string[] = []

      // Write all blobs
      for (const data of testData) {
        const hash = await testBlobStorage.write(data)
        hashes.push(hash)
      }

      // Cold-cache instance forces storage reads
      const coldStore = new BlobStorage(wrappingAdapter)
      for (let i = 0; i < hashes.length; i++) {
        const retrieved = await coldStore.read(hashes[i])
        expect(retrieved.equals(testData[i])).toBe(true)
      }
    })

    it('should work even if adapter fails to unwrap (defense-in-depth)', async () => {
      // Create a buggy adapter that doesn't unwrap properly
      class BuggyAdapter implements BlobStoreAdapter {
        private storage = new Map<string, any>()

        async get(key: string): Promise<any | undefined> {
          // Simulate a bug where adapter returns wrapped data instead of Buffer
          const data = this.storage.get(key)
          if (!data) return undefined

          // Return wrapped object (bug) instead of unwrapped Buffer
          return data // {_binary: true, data: "base64..."}
        }

        async put(key: string, data: Buffer): Promise<void> {
          // Store as wrapped object (like real storage)
          this.storage.set(key, {
            _binary: true,
            data: data.toString('base64')
          })
        }

        async delete(key: string): Promise<void> {
          this.storage.delete(key)
        }

        async list(prefix: string): Promise<string[]> {
          return Array.from(this.storage.keys()).filter(k => k.startsWith(prefix))
        }
      }

      const buggyAdapter = new BuggyAdapter()
      const testBlobStorage = new BlobStorage(buggyAdapter)

      const originalData = Buffer.from('test defense-in-depth')
      const hash = await testBlobStorage.write(originalData)

      // Even with buggy adapter (and a cold cache), read() should unwrap and
      // verify correctly
      const retrieved = await new BlobStorage(buggyAdapter).read(hash)
      expect(retrieved.equals(originalData)).toBe(true)
    })
  })

  describe('Key-based dispatch regression (v6.2.0)', () => {
    it('should handle JSON-like compressed data without integrity failures', async () => {
      // THE KILLER TEST CASE: Data that looks like JSON when compressed
      // This would fail with v5.10.1 wrapBinaryData() guessing approach
      const { TestWrappingAdapter } = await import('../../helpers/TestWrappingAdapter.js')
      const wrappingAdapter = new TestWrappingAdapter()
      const testBlobStorage = new BlobStorage(wrappingAdapter)

      // Create JSON data that will be compressed
      const jsonData = { nested: { key: 'value', array: [1, 2, 3] }, repeated: 'x'.repeat(1000) }
      const originalData = Buffer.from(JSON.stringify(jsonData))

      // Write blob (compression happens, might create JSON-parseable bytes)
      const hash = await testBlobStorage.write(originalData)

      // v5.10.1 bug: If compressed bytes accidentally parse as JSON,
      // wrapBinaryData() would store parsed object instead of wrapped binary
      // On read: JSON.stringify(object) !== original compressed bytes → hash mismatch
      //
      // v6.2.0 fix: Key-based dispatch eliminates guessing
      // 'blob:hash' → Always wrapped as binary, never parsed
      const retrieved = await new BlobStorage(wrappingAdapter).read(hash)

      // Hash MUST match
      expect(BlobStorage.hash(retrieved)).toBe(hash)
      expect(retrieved.equals(originalData)).toBe(true)
    })

    it('should handle metadata keys correctly', async () => {
      // Verify that key-based dispatch correctly handles metadata keys
      // This test verifies the dispatch logic, not the full read/write cycle
      const { TestWrappingAdapter } = await import('../../helpers/TestWrappingAdapter.js')
      const wrappingAdapter = new TestWrappingAdapter()

      // Test metadata key dispatch: should parse as JSON
      const metadataObj = { hash: 'test123', size: 42, compression: 'none' as const }
      const metadataBuffer = Buffer.from(JSON.stringify(metadataObj))

      await wrappingAdapter.put('blob-meta:test123', metadataBuffer)
      const retrieved = await wrappingAdapter.get('blob-meta:test123')

      // Should be parsed as JSON object (not wrapped as binary)
      expect(retrieved).toBeDefined()
      expect(typeof retrieved).toBe('object')
      expect(retrieved.hash).toBe('test123')
      expect(retrieved.size).toBe(42)
    })

    it('should never parse blob bytes as JSON on the write path', async () => {
      // Verify that the blob bridge uses key-based dispatch,
      // NOT wrapBinaryData() guessing
      const { TestWrappingAdapter } = await import('../../helpers/TestWrappingAdapter.js')
      const wrappingAdapter = new TestWrappingAdapter()
      const testBlobStorage = new BlobStorage(wrappingAdapter)

      // Create data that would trigger wrapBinaryData() bug if used
      const problematicData = Buffer.from('[{"looks":"like","valid":"json"}]')
      const hash = await testBlobStorage.write(problematicData)

      const retrieved = await new BlobStorage(wrappingAdapter).read(hash)

      // Should retrieve exact same bytes (no JSON parsing occurred)
      expect(retrieved.equals(problematicData)).toBe(true)
      expect(BlobStorage.hash(retrieved)).toBe(hash)
    })
  })
})