import "github.com/trealla-prolog/go/trealla"

func main() {
	// load the interpreter and (optionally) grant access to the current directory
	pl := trealla.New(trealla.WithPreopen("."))
	// run a query; cancel context to abort it
	ctx := context.Background()
	query := pl.Query(ctx, "member(X, [1, foo(bar), c]).")

	// calling Close is not necessary if you iterate through the whole result set
	// but it doesn't hurt either
	defer query.Close()

	// iterate through answers
	for query.Next(ctx) {
		answer := query.Current()
		x := answer.Solution["X"]
		fmt.Println(x) // 1, trealla.Compound{Functor: "foo", Args: [trealla.Atom("bar")]}, "c"
	}

	// make sure to check the query for errors
	if err := query.Err(); err != nil {
		panic(err)
	}
}

pl := trealla.New()
answer, err := pl.QueryOnce(ctx, "succ(41, N).")
if err != nil {
	panic(err)
}

fmt.Println(answer.Stdout)
// Output: hello world

pl := trealla.New()
answer, err := pl.QueryOnce(ctx, "write(X)", trealla.WithBind("X", trealla.Atom("hello world")))
if err != nil {
	panic(err)
}

fmt.Println(answer.Stdout)
// Output: hello world

answer, err := pl.QueryOnce(ctx, `X = 123, Y = abc, Z = ["hello", "world"].`)
if err != nil {
	panic(err)
}

var result struct {
	X  int
	Y  string
	Hi []string `prolog:"Z"`
}
// make sure to pass a pointer to the struct!
if err := answer.Solution.Scan(&result); err != nil {
	panic(err)
}

fmt.Printf("%+v", result)
// Output: {X:123 Y:abc Hi:[hello world]}

// You can embed trealla.Functor to represent Prolog compounds using Go structs.

// kv(Flag, Value)
type pair struct {
	trealla.Functor `prolog:"-/2"` // tag is optional, but can be used to specify the functor/arity
	Flag            trealla.Atom   // 1st arg
	Value           trealla.Term   // 2nd arg
}
var result struct {
	Flags []pair // Flags variable
}

ctx := context.Background()
pl, err := trealla.New()
if err != nil {
	panic(err)
}
answer, err := pl.QueryOnce(ctx, `
	findall(Flag-Value, (member(Flag, [double_quotes, encoding, max_arity]), current_prolog_flag(Flag, Value)), Flags).
`)
if err != nil {
	panic(err)
}
if err := answer.Solution.Scan(&result); err != nil {
	panic(err)
}
fmt.Printf("%v\n", result.Flags)
// Output: [{- double_quotes chars} {- encoding 'UTF-8'} {- max_arity 255}]