Implement loading lua from separate files via @

processor/processor.go

@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"os"
+	"path/filepath"
 	"regexp"
 	"strings"
 
@@ -205,11 +207,62 @@ func PrependLuaAssignment(luaExpr string) string {
 	return luaExpr
 }
 
+// LoadExternalLuaFile loads Lua code from an external file
+func LoadExternalLuaFile(luaPath string, sourceDir string) (string, error) {
+	loadLuaLogger := processorLogger.WithPrefix("LoadExternalLuaFile").WithField("luaPath", luaPath).WithField("sourceDir", sourceDir)
+	loadLuaLogger.Debug("Loading external Lua file")
+
+	// Resolve path: if relative, resolve relative to sourceDir; if absolute, use as-is
+	var resolvedPath string
+	if filepath.IsAbs(luaPath) {
+		resolvedPath = luaPath
+	} else {
+		if sourceDir == "" {
+			// No source directory, use current working directory
+			cwd, err := os.Getwd()
+			if err != nil {
+				loadLuaLogger.Error("Failed to get current working directory: %v", err)
+				return "", fmt.Errorf("failed to get current working directory: %w", err)
+			}
+			resolvedPath = filepath.Join(cwd, luaPath)
+		} else {
+			resolvedPath = filepath.Join(sourceDir, luaPath)
+		}
+	}
+
+	// Normalize path
+	resolvedPath = filepath.Clean(resolvedPath)
+	loadLuaLogger.Debug("Resolved Lua file path: %q", resolvedPath)
+
+	// Read the file
+	content, err := os.ReadFile(resolvedPath)
+	if err != nil {
+		loadLuaLogger.Error("Failed to read Lua file %q: %v", resolvedPath, err)
+		return "", fmt.Errorf("failed to read Lua file %q: %w", luaPath, err)
+	}
+
+	loadLuaLogger.Debug("Successfully loaded %d bytes from Lua file %q", len(content), resolvedPath)
+	return string(content), nil
+}
+
 // BuildLuaScript prepares a Lua expression from shorthand notation
-func BuildLuaScript(luaExpr string) string {
+func BuildLuaScript(luaExpr string, sourceDir string) string {
 	buildLuaScriptLogger := processorLogger.WithPrefix("BuildLuaScript").WithField("inputLuaExpr", luaExpr)
 	buildLuaScriptLogger.Debug("Building full Lua script from expression")
 
+	// Check if this is an external Lua file reference
+	if strings.HasPrefix(luaExpr, "@") {
+		luaPath := strings.TrimPrefix(luaExpr, "@")
+		externalLua, err := LoadExternalLuaFile(luaPath, sourceDir)
+		if err != nil {
+			buildLuaScriptLogger.Error("Failed to load external Lua file: %v", err)
+			// Return error script that will fail at runtime
+			return fmt.Sprintf(`error("Failed to load external Lua file: %v")`, err)
+		}
+		luaExpr = externalLua
+		buildLuaScriptLogger.Debug("Loaded external Lua file, %d characters", len(luaExpr))
+	}
+
 	// Perform $var substitutions from globalVariables
 	luaExpr = replaceVariables(luaExpr)
 
@@ -228,10 +281,23 @@ func BuildLuaScript(luaExpr string) string {
 }
 
 // BuildJSONLuaScript prepares a Lua expression for JSON mode
-func BuildJSONLuaScript(luaExpr string) string {
+func BuildJSONLuaScript(luaExpr string, sourceDir string) string {
 	buildJSONLuaScriptLogger := processorLogger.WithPrefix("BuildJSONLuaScript").WithField("inputLuaExpr", luaExpr)
 	buildJSONLuaScriptLogger.Debug("Building full Lua script for JSON mode from expression")
 
+	// Check if this is an external Lua file reference
+	if strings.HasPrefix(luaExpr, "@") {
+		luaPath := strings.TrimPrefix(luaExpr, "@")
+		externalLua, err := LoadExternalLuaFile(luaPath, sourceDir)
+		if err != nil {
+			buildJSONLuaScriptLogger.Error("Failed to load external Lua file: %v", err)
+			// Return error script that will fail at runtime
+			return fmt.Sprintf(`error("Failed to load external Lua file: %v")`, err)
+		}
+		luaExpr = externalLua
+		buildJSONLuaScriptLogger.Debug("Loaded external Lua file, %d characters", len(luaExpr))
+	}
+
 	// Perform $var substitutions from globalVariables
 	luaExpr = replaceVariables(luaExpr)