db: add redis (#24730)

Author: kbkpbot

vlib/db/redis/README.md

@@ -0,0 +1,149 @@
+# Redis Client for V
+
+This module provides a Redis client implementation in V that supports the 
+Redis Serialization Protocol (RESP) with a type-safe interface for common Redis commands.
+
+## Features
+
+- **Type-Safe Commands**: Auto-detects value types at compile time
+- **Pipeline Support**: Group commands for batch execution
+- **Connection Pooling**: Efficient resource management
+- **RESP Protocol Support**: Full Redis Serialization Protocol implementation
+- **Memory Efficient**: Pre-allocated buffers for minimal allocations
+
+## Quick Start
+
+```v
+module main
+
+import db.redis
+
+fn main() {
+	// Connect to Redis
+	mut db := redis.connect(redis.Config{
+		host: 'localhost'
+		port: 6379
+	})!
+
+	// Set and get values
+	db.set('name', 'Alice')!
+	name := db.get[string]('name')!
+	println('Name: ${name}') // Output: Name: Alice
+
+	// Integer operations
+	db.set('counter', 42)!
+	db.incr('counter')!
+	counter := db.get[int]('counter')!
+	println('Counter: ${counter}') // Output: Counter: 43
+
+	// Clean up
+	db.close()!
+}
+```
+
+## Supported Commands
+
+### Key Operations
+
+```v ignore
+// Set value
+db.set('key', 'value')!
+db.set('number', 42)!
+db.set('binary', []u8{len: 4, init: 0})!
+
+// Get value
+str_value := db.get[string]('key')!
+int_value := db.get[int]('number')!
+bin_value := db.get[[]u8]('binary')!
+
+// Delete key
+db.del('key')!
+
+// Set expiration
+db.expire('key', 60)!  // 60 seconds
+```
+
+### Hash Operations
+
+```v ignore
+// Set hash fields
+db.hset('user:1', {
+    'name': 'Bob',
+    'age': 30,
+})!
+
+// Get single field
+name := db.hget[string]('user:1', 'name')!
+
+// Get all fields
+user_data := db.hgetall[string]('user:1')!
+println(user_data)  // Output: {'name': 'Bob', 'age': '30'}
+```
+
+### Pipeline Operations
+
+```v ignore
+// Start pipeline
+db.pipeline_start()
+
+// Queue commands
+db.incr('counter')
+db.set('name', 'Charlie')
+db.get[string]('name')
+
+// Execute and get responses
+responses := db.pipeline_execute()!
+for resp in responses {
+    println(resp)
+}
+```
+
+### Custom Commands
+
+```v ignore
+// Run raw commands
+resp := db.cmd('SET', 'custom', 'value')!
+result := db.cmd('GET', 'custom')!
+
+// Complex commands
+db.cmd('HSET', 'user:2', 'field1', 'value1', 'field2', '42')!
+```
+
+## Error Handling
+
+All functions return `!` types and will return detailed errors for:
+
+- Connection issues
+- Protocol violations
+- Type mismatches
+- Redis error responses
+- Timeout conditions
+
+```v ignore
+result := db.get[string]('nonexistent') or {
+    println('Key not found')
+    return
+}
+```
+
+## Connection Management
+
+```v ignore
+config := redis.Config{
+    host: 'redis.server'
+    port: 6379
+    version: 2  // RESP2 protocol
+}
+
+mut db := redis.connect(config)!
+defer {
+    db.close() or { eprintln('Error closing connection: $err') }
+}
+```
+
+## Performance Tips
+
+1. **Reuse Connections**: Maintain connections instead of creating new ones
+2. **Use Pipelines**: Batch commands for high-throughput operations
+3. **Prefer Integers**: Use numeric types for counters and metrics
+4. **Specify Types**: Always specify return types for get operations