add support for env variables to the DSL

interpreter/server_interpreter.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"go/format"
 	"masonry/lang"
+	"strconv"
 	"strings"
 
 	"golang.org/x/text/cases"
@@ -69,6 +70,8 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"os"
+	"strconv"
 	"sync"
 	"time"
 	"github.com/google/uuid"
@@ -362,25 +365,95 @@ func (si *ServerInterpreter) generateMainFunction() string {
 		}
 	}
 
-	// Server configuration
-	host := "localhost"
-	port := 8080
+	// Generate server configuration code that handles env vars and defaults at runtime
+	code.WriteString("\n\t// Server configuration\n")
+	code.WriteString(si.generateServerConfigCode())
 
-	if si.server != nil {
-		for _, setting := range si.server.Settings {
-			if setting.Host != nil {
-				host = *setting.Host
-			}
-			if setting.Port != nil {
-				port = *setting.Port
-			}
-		}
-	}
-
-	code.WriteString(fmt.Sprintf("\n\taddr := \"%s:%d\"\n", host, port))
+	code.WriteString("\n\taddr := fmt.Sprintf(\"%s:%d\", host, port)\n")
 	code.WriteString("\tfmt.Printf(\"Server starting on %s\\n\", addr)\n")
 	code.WriteString("\tlog.Fatal(http.ListenAndServe(addr, r))\n")
 	code.WriteString("}\n")
 
 	return code.String()
 }
+
+// generateServerConfigCode generates Go code that handles server configuration at runtime
+func (si *ServerInterpreter) generateServerConfigCode() string {
+	var code strings.Builder
+
+	// Default values
+	hostDefault := "localhost"
+	portDefault := 8080
+	var hostConfigValueCode, portConfigValueCode string
+
+	if si.server != nil {
+		for _, setting := range si.server.Settings {
+			if setting.Host != nil {
+				if setting.Host.EnvVar != nil && setting.Host.EnvVar.Default != nil {
+					hostDefault = *setting.Host.EnvVar.Default
+				}
+				hostConfigValueCode = si.generateConfigValueCode("host", setting.Host)
+			}
+			if setting.Port != nil {
+				if setting.Port.EnvVar != nil && setting.Port.EnvVar.Default != nil {
+					if defInt, err := strconv.Atoi(*setting.Port.EnvVar.Default); err == nil {
+						portDefault = defInt
+					}
+				}
+				portConfigValueCode = si.generateIntValueCode("port", setting.Port)
+			}
+		}
+	}
+	code.WriteString(fmt.Sprintf("\thost := \"%s\"\n", hostDefault))
+	code.WriteString(fmt.Sprintf("\tport := %d\n\n", portDefault))
+	code.WriteString(hostConfigValueCode)
+	code.WriteString(portConfigValueCode)
+
+	return code.String()
+}
+
+// generateConfigValueCode generates Go code to resolve a ConfigValue at runtime
+func (si *ServerInterpreter) generateConfigValueCode(varName string, configValue *lang.ConfigValue) string {
+	var code strings.Builder
+
+	if configValue.Literal != nil {
+		// Simple literal assignment
+		code.WriteString(fmt.Sprintf("\t%s = %q\n", varName, *configValue.Literal))
+	} else if configValue.EnvVar != nil {
+		// Environment variable with optional default
+		code.WriteString(fmt.Sprintf("\tif envVal := os.Getenv(%q); envVal != \"\" {\n", configValue.EnvVar.Name))
+		code.WriteString(fmt.Sprintf("\t\t%s = envVal\n", varName))
+
+		if configValue.EnvVar.Default != nil {
+			code.WriteString("\t} else {\n")
+			code.WriteString(fmt.Sprintf("\t\t%s = %q\n", varName, *configValue.EnvVar.Default))
+		}
+		code.WriteString("\t}\n")
+	}
+
+	return code.String()
+}
+
+// generateIntValueCode generates Go code to resolve an IntValue at runtime
+func (si *ServerInterpreter) generateIntValueCode(varName string, intValue *lang.IntValue) string {
+	var code strings.Builder
+
+	if intValue.Literal != nil {
+		// Simple literal assignment
+		code.WriteString(fmt.Sprintf("\t%s = %d\n", varName, *intValue.Literal))
+	} else if intValue.EnvVar != nil {
+		// Environment variable with optional default
+		code.WriteString(fmt.Sprintf("\tif envVal := os.Getenv(%q); envVal != \"\" {\n", intValue.EnvVar.Name))
+		code.WriteString(fmt.Sprintf("\t\tif val, err := strconv.Atoi(envVal); err == nil {\n"))
+		code.WriteString(fmt.Sprintf("\t\t\t%s = val\n", varName))
+		code.WriteString("\t\t}\n")
+
+		if intValue.EnvVar.Default != nil {
+			code.WriteString("\t} else {\n")
+			code.WriteString(fmt.Sprintf("\t\t%s = %s\n", varName, *intValue.EnvVar.Default))
+		}
+		code.WriteString("\t}\n")
+	}
+
+	return code.String()
+}