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/expression"
	"git.akyoto.dev/cli/q/src/build/token"
)

// Compare evaluates a boolean expression.
func (f *Function) Compare(comparison *expression.Expression) error {
	left := comparison.Children[0]
	right := comparison.Children[1]

	if left.IsLeaf() && left.Token.Kind == token.Identifier {
		name := left.Token.Text()
		variable := f.Variable(name)

		if variable == nil {
			return errors.New(&errors.UnknownIdentifier{Name: name}, f.File, left.Token.Position)
		}

		defer f.useVariable(variable)
		return f.Execute(comparison.Token, variable.Register, right)
	}

	if ast.IsFunctionCall(left) && right.IsLeaf() {
		err := f.CompileCall(left)

		if err != nil {
			return err
		}

		return f.Execute(comparison.Token, f.cpu.Output[0], right)
	}

	tmp := f.Scope().MustFindFree(f.cpu.General)
	err := f.ExpressionToRegister(left, tmp)

	if err != nil {
		return err
	}

	defer f.Scope().Free(tmp)
	return f.Execute(comparison.Token, tmp, right)
}