Move compiler-related components to internal package

Refactored the structure by relocating `compiler` elements into an `internal` package. Made `visitor` struct and methods exported for broader access. Added new utility methods in `Emitter` and `RegisterAllocator` to optimize functionality.

pkg/compiler/compiler.go

@@ -4,6 +4,8 @@ import (
 	"errors"
 	goruntime "runtime"
 
+	"github.com/MontFerret/ferret/pkg/compiler/internal"
+
 	"github.com/MontFerret/ferret/pkg/stdlib"
 	"github.com/MontFerret/ferret/pkg/vm"
 
@@ -35,7 +37,7 @@ func New(setters ...Option) *Compiler {
 
 func (c *Compiler) Compile(query string) (program *vm.Program, err error) {
 	if query == "" {
-		return nil, ErrEmptyQuery
+		return nil, internal.ErrEmptyQuery
 	}
 
 	defer func() {
@@ -62,24 +64,20 @@ func (c *Compiler) Compile(query string) (program *vm.Program, err error) {
 	p := parser.New(query)
 	p.AddErrorListener(newErrorListener())
 
-	l := newVisitor(query)
+	l := internal.NewVisitor(query)
 
 	p.Visit(l)
 
-	if l.err != nil {
-		return nil, l.err
+	if l.Err != nil {
+		return nil, l.Err
 	}
 
 	program = &vm.Program{}
-	program.Bytecode = l.emitter.instructions
-	program.Constants = l.symbols.constants
-	program.CatchTable = l.catchTable
-	program.Registers = int(l.registers.nextRegister)
-	program.Params = make([]string, 0, len(l.symbols.params))
-
-	for _, param := range l.symbols.params {
-		program.Params = append(program.Params, param)
-	}
+	program.Bytecode = l.Emitter.Bytecode()
+	program.Constants = l.Symbols.Constants()
+	program.CatchTable = l.CatchTable
+	program.Registers = l.Registers.Size()
+	program.Params = l.Symbols.Params()
 
 	return program, err
 }

pkg/compiler/internal/allocator.go

@@ -1,4 +1,4 @@
-package compiler
+package internal
 
 import (
 	"github.com/MontFerret/ferret/pkg/vm"
@@ -45,6 +45,10 @@ func NewRegisterAllocator() *RegisterAllocator {
 	}
 }
 
+func (ra *RegisterAllocator) Size() int {
+	return int(ra.nextRegister)
+}
+
 // Allocate assigns a register based on variable type
 func (ra *RegisterAllocator) Allocate(regType RegisterType) vm.Operand {
 	// Try to find a free register first

pkg/compiler/internal/emitter.go

@@ -1,4 +1,4 @@
-package compiler
+package internal
 
 import (
 	"github.com/MontFerret/ferret/pkg/vm"
@@ -14,6 +14,10 @@ func NewEmitter() *Emitter {
 	}
 }
 
+func (e *Emitter) Bytecode() []vm.Instruction {
+	return e.instructions
+}
+
 func (e *Emitter) Size() int {
 	return len(e.instructions)
 }

pkg/compiler/internal/errors.go

@@ -1,4 +1,4 @@
-package compiler
+package internal
 
 import "github.com/pkg/errors"
 

pkg/compiler/internal/helpers.go

@@ -1,4 +1,4 @@
-package compiler
+package internal
 
 import (
 	"strings"

pkg/compiler/internal/loops.go

@@ -1,4 +1,4 @@
-package compiler
+package internal
 
 import (
 	"github.com/MontFerret/ferret/pkg/vm"

pkg/compiler/internal/symbols.go

@@ -1,4 +1,4 @@
-package compiler
+package internal
 
 import (
 	"strconv"
@@ -36,6 +36,20 @@ func NewSymbolTable(registers *RegisterAllocator) *SymbolTable {
 	}
 }
 
+func (st *SymbolTable) Params() []string {
+	params := make([]string, 0, len(st.params))
+
+	for _, name := range st.params {
+		params = append(params, name)
+	}
+
+	return params
+}
+
+func (st *SymbolTable) Constants() []runtime.Value {
+	return st.constants
+}
+
 func (st *SymbolTable) Scope() int {
 	return st.scope
 }

pkg/compiler/internal/symbols_test.go

@@ -1,4 +1,4 @@
-package compiler_test
+package internal_test
 
 import "testing"