package core

import (
	"git.akyoto.dev/cli/q/src/build/ast"
	"git.akyoto.dev/cli/q/src/build/errors"
	"git.akyoto.dev/cli/q/src/build/scope"
	"git.akyoto.dev/cli/q/src/build/token"
)

// CompileDefinition compiles a variable definition.
func (f *Function) CompileDefinition(node *ast.Define) error {
	name := node.Name.Text(f.File.Bytes)

	if f.identifierExists(name) {
		return errors.New(&errors.VariableAlreadyExists{Name: name}, f.File, node.Name.Position)
	}

	uses := token.Count(f.Body, f.File.Bytes, token.Identifier, name) - 1

	if uses == 0 {
		return errors.New(&errors.UnusedVariable{Name: name}, f.File, node.Name.Position)
	}

	register := f.CurrentScope().MustFindFree(f.cpu.General)
	f.CurrentScope().Reserve(register)
	err := f.ExpressionToRegister(node.Value, register)

	f.AddVariable(&scope.Variable{
		Name:     name,
		Register: register,
		Alive:    uses,
	})

	return err
}