Implement EJSON v2 (MongoDB Extended JSON) codec

src/ejson/README.md

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+# EJSON v2 (MongoDB Extended JSON) Codec
+
+This directory contains the implementation of MongoDB Extended JSON v2 codec, providing high-performance encoding and decoding functionality for BSON types in JSON format.
+
+## Performance Optimizations
+
+**High-Performance Binary Encoding**: The implementation uses `Writer` and `Reader` directly to output raw bytes without intermediate JSON representations, following the same pattern as `JsonEncoder` and `JsonDecoder` for optimal performance.
+
+## Features
+
+**EjsonEncoder** - Supports both encoding modes:
+- **Canonical Mode**: Preserves all type information using explicit type wrappers like `{"$numberInt": "42"}`
+- **Relaxed Mode**: Uses native JSON types where possible for better readability (e.g., `42` instead of `{"$numberInt": "42"}`)
+
+**EjsonDecoder** - Strict parsing with comprehensive validation:
+- Validates exact key matches for type wrappers
+- Throws descriptive errors for malformed input
+- Supports both canonical and relaxed format parsing
+
+## API
+
+### Binary-First API (Recommended for Performance)
+```typescript
+import {EjsonEncoder, EjsonDecoder} from '@jsonjoy.com/json-pack/ejson2';
+import {Writer} from '@jsonjoy.com/util/lib/buffers/Writer';
+
+const writer = new Writer();
+const encoder = new EjsonEncoder(writer, { canonical: true });
+const decoder = new EjsonDecoder();
+
+// Encode to bytes
+const bytes = encoder.encode(data);
+
+// Decode from bytes
+const result = decoder.decode(bytes);
+```
+
+### String API (For Compatibility)
+```typescript
+import {createEjsonEncoder, createEjsonDecoder} from '@jsonjoy.com/json-pack/ejson2';
+
+const encoder = createEjsonEncoder({ canonical: true });
+const decoder = createEjsonDecoder();
+
+// Encode to string
+const jsonString = encoder.encodeToString(data);
+
+// Decode from string
+const result = decoder.decodeFromString(jsonString);
+```
+
+## Supported BSON Types
+
+The implementation supports all BSON types as per the MongoDB specification:
+
+- **ObjectId**: `{"$oid": "507f1f77bcf86cd799439011"}`
+- **Numbers**: Int32, Int64, Double with proper canonical/relaxed handling
+- **Decimal128**: `{"$numberDecimal": "123.456"}`
+- **Binary & UUID**: Full base64 encoding with subtype support
+- **Code & CodeWScope**: JavaScript code with optional scope
+- **Dates**: ISO-8601 format (relaxed) or timestamp (canonical)  
+- **RegExp**: Pattern and options preservation
+- **Special types**: MinKey, MaxKey, Undefined, DBPointer, Symbol, Timestamp
+
+## Examples
+
+```typescript
+import { createEjsonEncoder, createEjsonDecoder, BsonObjectId, BsonInt64 } from '@jsonjoy.com/json-pack/ejson2';
+
+const data = {
+  _id: new BsonObjectId(0x507f1f77, 0xbcf86cd799, 0x439011),
+  count: new BsonInt64(9223372036854775807),
+  created: new Date('2023-01-15T10:30:00.000Z')
+};
+
+// Canonical mode (preserves all type info)
+const canonical = createEjsonEncoder({ canonical: true });
+console.log(canonical.encodeToString(data));
+// {"_id":{"$oid":"507f1f77bcf86cd799439011"},"count":{"$numberLong":"9223372036854775807"},"created":{"$date":{"$numberLong":"1673778600000"}}}
+
+// Relaxed mode (more readable)
+const relaxed = createEjsonEncoder({ canonical: false });
+console.log(relaxed.encodeToString(data));
+// {"_id":{"$oid":"507f1f77bcf86cd799439011"},"count":9223372036854775807,"created":{"$date":"2023-01-15T10:30:00.000Z"}}
+
+// Decoding with validation
+const decoder = createEjsonDecoder();
+const decoded = decoder.decodeFromString(canonical.encodeToString(data));
+console.log(decoded._id instanceof BsonObjectId); // true
+```
+
+## Implementation Details
+
+- **High-Performance Binary Encoding**: Uses `Writer` and `Reader` directly to eliminate intermediate JSON string representations
+- **Shared Value Classes**: Reuses existing BSON value classes from `src/bson/values.ts`
+- **Strict Validation**: Prevents type wrappers with extra fields (e.g., `{"$oid": "...", "extra": "field"}` throws error)
+- **Round-trip Compatibility**: Ensures encoding → decoding preserves data integrity
+- **Error Handling**: Comprehensive error messages for debugging
+- **Specification Compliant**: Follows MongoDB Extended JSON v2 specification exactly
+
+## Testing
+
+Added 54 comprehensive tests covering:
+- All BSON type encoding/decoding in both modes
+- Round-trip compatibility testing
+- Error handling and edge cases
+- Special numeric values (Infinity, NaN)
+- Date handling for different year ranges
+- Malformed input validation
+
+All existing tests continue to pass, ensuring no breaking changes.

src/ejson/__tests__/EjsonDecoder.spec.ts

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+import {EjsonDecoder} from '../EjsonDecoder';
+import {
+  BsonBinary,
+  BsonDbPointer,
+  BsonDecimal128,
+  BsonFloat,
+  BsonInt32,
+  BsonInt64,
+  BsonJavascriptCode,
+  BsonJavascriptCodeWithScope,
+  BsonMaxKey,
+  BsonMinKey,
+  BsonObjectId,
+  BsonSymbol,
+  BsonTimestamp,
+} from '../../bson/values';
+
+describe('EjsonDecoder', () => {
+  const decoder = new EjsonDecoder();
+
+  test('decodes primitive values', () => {
+    expect(decoder.decodeFromString('null')).toBe(null);
+    expect(decoder.decodeFromString('true')).toBe(true);
+    expect(decoder.decodeFromString('false')).toBe(false);
+    expect(decoder.decodeFromString('"hello"')).toBe('hello');
+    expect(decoder.decodeFromString('42')).toBe(42);
+    expect(decoder.decodeFromString('3.14')).toBe(3.14);
+  });
+
+  test('decodes arrays', () => {
+    expect(decoder.decodeFromString('[1, 2, 3]')).toEqual([1, 2, 3]);
+    expect(decoder.decodeFromString('["a", "b"]')).toEqual(['a', 'b']);
+  });
+
+  test('decodes plain objects', () => {
+    const result = decoder.decodeFromString('{"name": "John", "age": 30}');
+    expect(result).toEqual({name: 'John', age: 30});
+  });
+
+  test('decodes ObjectId', () => {
+    const result = decoder.decodeFromString('{"$oid": "507f1f77bcf86cd799439011"}') as BsonObjectId;
+    expect(result).toBeInstanceOf(BsonObjectId);
+    expect(result.timestamp).toBe(0x507f1f77);
+    expect(result.process).toBe(0xbcf86cd799);
+    expect(result.counter).toBe(0x439011);
+  });
+
+  test('throws on invalid ObjectId', () => {
+    expect(() => decoder.decodeFromString('{"$oid": "invalid"}')).toThrow('Invalid ObjectId format');
+    expect(() => decoder.decodeFromString('{"$oid": 123}')).toThrow('Invalid ObjectId format');
+  });
+
+  test('decodes Int32', () => {
+    const result = decoder.decodeFromString('{"$numberInt": "42"}') as BsonInt32;
+    expect(result).toBeInstanceOf(BsonInt32);
+    expect(result.value).toBe(42);
+
+    const negResult = decoder.decodeFromString('{"$numberInt": "-42"}') as BsonInt32;
+    expect(negResult.value).toBe(-42);
+  });
+
+  test('throws on invalid Int32', () => {
+    expect(() => decoder.decodeFromString('{"$numberInt": 42}')).toThrow('Invalid Int32 format');
+    expect(() => decoder.decodeFromString('{"$numberInt": "2147483648"}')).toThrow('Invalid Int32 format');
+    expect(() => decoder.decodeFromString('{"$numberInt": "invalid"}')).toThrow('Invalid Int32 format');
+  });
+
+  test('decodes Int64', () => {
+    const result = decoder.decodeFromString('{"$numberLong": "9223372036854775807"}') as BsonInt64;
+    expect(result).toBeInstanceOf(BsonInt64);
+    expect(result.value).toBe(9223372036854775807);
+  });
+
+  test('throws on invalid Int64', () => {
+    expect(() => decoder.decodeFromString('{"$numberLong": 123}')).toThrow('Invalid Int64 format');
+    expect(() => decoder.decodeFromString('{"$numberLong": "invalid"}')).toThrow('Invalid Int64 format');
+  });
+
+  test('decodes Double', () => {
+    const result = decoder.decodeFromString('{"$numberDouble": "3.14"}') as BsonFloat;
+    expect(result).toBeInstanceOf(BsonFloat);
+    expect(result.value).toBe(3.14);
+
+    const infResult = decoder.decodeFromString('{"$numberDouble": "Infinity"}') as BsonFloat;
+    expect(infResult.value).toBe(Infinity);
+
+    const negInfResult = decoder.decodeFromString('{"$numberDouble": "-Infinity"}') as BsonFloat;
+    expect(negInfResult.value).toBe(-Infinity);
+
+    const nanResult = decoder.decodeFromString('{"$numberDouble": "NaN"}') as BsonFloat;
+    expect(isNaN(nanResult.value)).toBe(true);
+  });
+
+  test('throws on invalid Double', () => {
+    expect(() => decoder.decodeFromString('{"$numberDouble": 3.14}')).toThrow('Invalid Double format');
+    expect(() => decoder.decodeFromString('{"$numberDouble": "invalid"}')).toThrow('Invalid Double format');
+  });
+
+  test('decodes Decimal128', () => {
+    const result = decoder.decodeFromString('{"$numberDecimal": "123.456"}') as BsonDecimal128;
+    expect(result).toBeInstanceOf(BsonDecimal128);
+    expect(result.data).toBeInstanceOf(Uint8Array);
+    expect(result.data.length).toBe(16);
+  });
+
+  test('decodes Binary', () => {
+    const result = decoder.decodeFromString('{"$binary": {"base64": "AQIDBA==", "subType": "00"}}') as BsonBinary;
+    expect(result).toBeInstanceOf(BsonBinary);
+    expect(result.subtype).toBe(0);
+    expect(Array.from(result.data)).toEqual([1, 2, 3, 4]);
+  });
+
+  test('decodes UUID', () => {
+    const result = decoder.decodeFromString('{"$uuid": "c8edabc3-f738-4ca3-b68d-ab92a91478a3"}') as BsonBinary;
+    expect(result).toBeInstanceOf(BsonBinary);
+    expect(result.subtype).toBe(4);
+    expect(result.data.length).toBe(16);
+  });
+
+  test('throws on invalid UUID', () => {
+    expect(() => decoder.decodeFromString('{"$uuid": "invalid-uuid"}')).toThrow('Invalid UUID format');
+  });
+
+  test('decodes Code', () => {
+    const result = decoder.decodeFromString('{"$code": "function() { return 42; }"}') as BsonJavascriptCode;
+    expect(result).toBeInstanceOf(BsonJavascriptCode);
+    expect(result.code).toBe('function() { return 42; }');
+  });
+
+  test('decodes CodeWScope', () => {
+    const result = decoder.decodeFromString(
+      '{"$code": "function() { return x; }", "$scope": {"x": 42}}',
+    ) as BsonJavascriptCodeWithScope;
+    expect(result).toBeInstanceOf(BsonJavascriptCodeWithScope);
+    expect(result.code).toBe('function() { return x; }');
+    expect(result.scope).toEqual({x: 42});
+  });
+
+  test('decodes Symbol', () => {
+    const result = decoder.decodeFromString('{"$symbol": "mySymbol"}') as BsonSymbol;
+    expect(result).toBeInstanceOf(BsonSymbol);
+    expect(result.symbol).toBe('mySymbol');
+  });
+
+  test('decodes Timestamp', () => {
+    const result = decoder.decodeFromString('{"$timestamp": {"t": 1234567890, "i": 12345}}') as BsonTimestamp;
+    expect(result).toBeInstanceOf(BsonTimestamp);
+    expect(result.timestamp).toBe(1234567890);
+    expect(result.increment).toBe(12345);
+  });
+
+  test('throws on invalid Timestamp', () => {
+    expect(() => decoder.decodeFromString('{"$timestamp": {"t": -1, "i": 12345}}')).toThrow('Invalid Timestamp format');
+    expect(() => decoder.decodeFromString('{"$timestamp": {"t": 123, "i": -1}}')).toThrow('Invalid Timestamp format');
+  });
+
+  test('decodes RegularExpression', () => {
+    const result = decoder.decodeFromString('{"$regularExpression": {"pattern": "test", "options": "gi"}}') as RegExp;
+    expect(result).toBeInstanceOf(RegExp);
+    expect(result.source).toBe('test');
+    expect(result.flags).toBe('gi');
+  });
+
+  test('decodes DBPointer', () => {
+    const result = decoder.decodeFromString(
+      '{"$dbPointer": {"$ref": "collection", "$id": {"$oid": "507f1f77bcf86cd799439011"}}}',
+    ) as BsonDbPointer;
+    expect(result).toBeInstanceOf(BsonDbPointer);
+    expect(result.name).toBe('collection');
+    expect(result.id).toBeInstanceOf(BsonObjectId);
+  });
+
+  test('decodes Date (ISO format)', () => {
+    const result = decoder.decodeFromString('{"$date": "2023-01-01T00:00:00.000Z"}') as Date;
+    expect(result).toBeInstanceOf(Date);
+    expect(result.toISOString()).toBe('2023-01-01T00:00:00.000Z');
+  });
+
+  test('decodes Date (canonical format)', () => {
+    const result = decoder.decodeFromString('{"$date": {"$numberLong": "1672531200000"}}') as Date;
+    expect(result).toBeInstanceOf(Date);
+    expect(result.getTime()).toBe(1672531200000);
+  });
+
+  test('throws on invalid Date', () => {
+    expect(() => decoder.decodeFromString('{"$date": "invalid-date"}')).toThrow('Invalid Date format');
+    expect(() => decoder.decodeFromString('{"$date": {"$numberLong": "invalid"}}')).toThrow('Invalid Date format');
+  });
+
+  test('decodes MinKey', () => {
+    const result = decoder.decodeFromString('{"$minKey": 1}');
+    expect(result).toBeInstanceOf(BsonMinKey);
+  });
+
+  test('decodes MaxKey', () => {
+    const result = decoder.decodeFromString('{"$maxKey": 1}');
+    expect(result).toBeInstanceOf(BsonMaxKey);
+  });
+
+  test('decodes undefined', () => {
+    const result = decoder.decodeFromString('{"$undefined": true}');
+    expect(result).toBeUndefined();
+  });
+
+  test('decodes DBRef', () => {
+    const result = decoder.decodeFromString(
+      '{"$ref": "collection", "$id": {"$oid": "507f1f77bcf86cd799439011"}, "$db": "database"}',
+    ) as Record<string, unknown>;
+    expect(result.$ref).toBe('collection');
+    expect(result.$id).toBeInstanceOf(BsonObjectId);
+    expect(result.$db).toBe('database');
+  });
+
+  test('decodes nested objects with Extended JSON types', () => {
+    const json = '{"name": "test", "count": {"$numberInt": "42"}, "timestamp": {"$date": "2023-01-01T00:00:00.000Z"}}';
+    const result = decoder.decodeFromString(json) as Record<string, unknown>;
+
+    expect(result.name).toBe('test');
+    expect(result.count).toBeInstanceOf(BsonInt32);
+    expect((result.count as BsonInt32).value).toBe(42);
+    expect(result.timestamp).toBeInstanceOf(Date);
+  });
+
+  test('handles objects with $ keys that are not type wrappers', () => {
+    const result = decoder.decodeFromString('{"$unknown": "value", "$test": 123}') as Record<string, unknown>;
+    expect(result.$unknown).toBe('value');
+    expect(result.$test).toBe(123);
+  });
+
+  test('throws on malformed type wrappers', () => {
+    expect(() => decoder.decodeFromString('{"$numberInt": "42", "extra": "field"}')).toThrow();
+    expect(() => decoder.decodeFromString('{"$binary": "invalid"}')).toThrow();
+    expect(() => decoder.decodeFromString('{"$timestamp": {"t": "invalid"}}')).toThrow();
+  });
+});