feat: Update README and add YAML config support with header modifications

Author: presbrey

README.md

@@ -13,13 +13,15 @@ A lightweight (1 file), dynamic reverse proxy server with live configuration rel
 
 ## Features
 
-- Live configuration reloading
-- Support for both local and remote proxy targets
-- Configurable logging options
-- HTTP/HTTPS support
-- Path-based routing
-- Automatic configuration file watching
-- Verbose logging options for debugging
+- Live configuration reloading with file watching
+- Support for HTTP/HTTPS proxy targets
+- Static file and directory serving
+- Request/Response header modification
+- Configurable timeouts and retries
+- Comprehensive logging options
+- Graceful shutdown support
+- Health check endpoint
+- Environment variable configuration
 
 ## Installation
 
@@ -35,51 +37,139 @@ cd lightymux
 go build
 ```
 
-## Usage
+## Configuration
 
-Basic usage:
+### Environment Variables
 
-```bash
-./lightymux [flags] <config_file>
+- `HTTP_ADDR`: HTTP listen address (default: "")
+- `READ_TIMEOUT`: Read timeout duration (default: 30s)
+- `WRITE_TIMEOUT`: Write timeout duration (default: 30s)
+- `IDLE_TIMEOUT`: Idle timeout duration (default: 60s)
+- `PROXY_TIMEOUT`: Proxy timeout duration (default: 60s)
+- `VERBOSE`: Enable verbose logging (default: false)
+- `LOG_REQUESTS`: Log incoming requests (default: false)
+- `LOG_RESPONSES`: Log outgoing responses (default: false)
+- `LOG_ERRORS`: Log proxy errors (default: true)
+- `LOG_FILE`: Log to file instead of stderr
+- `HEALTH_CHECK`: Health check endpoint path (default: "/health")
+- `RETRY_ATTEMPTS`: Number of retry attempts (default: 3)
+
+### Configuration File Format
+
+The configuration file uses YAML format. Each route is defined by its path and target configuration:
+
+```yaml
+/api:
+  target: http://api.example.com
+  rules:
+    - request:
+        headers:
+          X-API-Key: secret-key
+    - response:
+        headers:
+          Access-Control-Allow-Origin: "*"
+
+/static:
+  target: /var/www/static
+
+/files:
+  target: /path/to/files
 ```
 
-### Command Line Flags
+Routes can be configured for:
+- Remote HTTP/HTTPS endpoints
+- Local directories (static file serving)
+- Single files
+
+#### Header Modification
+
+You can modify request and response headers for each route using three operations:
+
+- `header-add`: Add values to existing headers (supports multiple values)
+- `header-set`: Set headers to specific values, replacing any existing ones
+- `header-del`: Remove headers completely
+
+Example:
+
+```yaml
+/api:
+  target: http://api.example.com
+  rules:
+    - request:
+        headers:
+          header-add:
+            Accept: ["application/json", "text/plain"]
+            X-Custom: ["value1", "value2"]
+          header-set:
+            Authorization: "Bearer token123"
+            Content-Type: "application/json"
+          header-del:
+            - "X-Old-Header"
+            - "X-Deprecated"
+    - response:
+        headers:
+          header-add:
+            Access-Control-Allow-Methods: ["GET", "POST", "OPTIONS"]
+          header-set:
+            Access-Control-Allow-Origin: "*"
+            Cache-Control: "max-age=3600"
+          header-del:
+            - "X-Internal-Header"
+```
 
-- `-http`: HTTP listen address (e.g., ":8080")
-- `-verbose`: Enable verbose logging
-- `-log-requests`: Log incoming requests
-- `-log-responses`: Log outgoing responses
-- `-log-errors`: Log proxy errors (default: true)
-- `-log-file`: Log to file instead of stderr
+In this example:
+- Request modifications:
+  - Adds multiple values to `Accept` and `X-Custom` headers
+  - Sets `Authorization` and `Content-Type` headers to specific values
+  - Removes `X-Old-Header` and `X-Deprecated` headers
+- Response modifications:
+  - Adds multiple CORS methods
+  - Sets CORS origin and caching headers
+  - Removes an internal header
 
-### Configuration File Format
+## Usage
 
-The configuration file uses a simple space-separated format where each line contains a path and target:
+Basic usage:
 
+```bash
+lightymux [config_file]
 ```
-/path target_url_or_path
-/api http://api.example.com
-/static /var/www/static
+
+Example with environment variables:
+
+```bash
+HTTP_ADDR=:8080 VERBOSE=true LOG_REQUESTS=true lightymux config.yaml
 ```
 
 The configuration file is watched for changes and automatically reloaded when modified.
 
 ## Example
 
-1. Create a configuration file `proxy.conf`:
-```
-/api http://localhost:3000
-/static http://localhost:8080
+1. Create a configuration file `config.yaml`:
+```yaml
+/api:
+  target: http://localhost:3000
+  rules:
+    - response:
+        headers:
+          Access-Control-Allow-Origin: "*"
+
+/static:
+  target: /var/www/static
+
+/docs:
+  target: http://localhost:8080
 ```
 
 2. Start the proxy:
 ```bash
-./lightymux -http :8000 proxy.conf
+lightymux config.yaml
 ```
 
-3. The proxy will now forward requests:
-   - `/api/*` → `http://localhost:3000/*`
-   - `/static/*` → `http://localhost:8080/*`
+3. The proxy will now:
+   - Forward `/api/*` to `http://localhost:3000/*` with CORS headers
+   - Serve static files from `/var/www/static` at `/static/*`
+   - Forward `/docs/*` to `http://localhost:8080/*`
 
 ## License
 

go.mod

@@ -7,4 +7,5 @@ require github.com/fsnotify/fsnotify v1.8.0
 require (
 	github.com/caarlos0/env/v11 v11.3.1
 	golang.org/x/sys v0.13.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1
 )

go.sum

@@ -4,3 +4,7 @@ github.com/fsnotify/fsnotify v1.8.0 h1:dAwr6QBTBZIkG8roQaJjGof0pp0EeF+tNV7YBP3F/
 github.com/fsnotify/fsnotify v1.8.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
 golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
 golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=