#include "system/stacktrace.h"
#include "./scope.h"

static struct Expr get_scope_value_impl(struct Expr scope, struct Expr name)
{
    if (cons_p(scope)) {
        struct Expr value = assoc(name, scope.cons->car);
        return nil_p(value) ? get_scope_value_impl(scope.cons->cdr, name) : value;
    }

    return scope;
}

struct Expr get_scope_value(const struct Scope *scope, struct Expr name)
{
    return get_scope_value_impl(scope->expr, name);
}

static struct Expr set_scope_value_impl(Gc *gc, struct Expr scope, struct Expr name, struct Expr value)
{
    if (cons_p(scope)) {
        if (!nil_p(assoc(name, scope.cons->car)) || nil_p(scope.cons->cdr)) {
            return CONS(gc,
                        CONS(gc, CONS(gc, name, value), scope.cons->car),
                        scope.cons->cdr);
        } else {
            return CONS(gc,
                        scope.cons->car,
                        set_scope_value_impl(gc, scope.cons->cdr, name, value));
        }
    } else {
        return CONS(gc,
                    CONS(gc, CONS(gc, name, value), NIL(gc)),
                    scope);
    }
}

struct Scope create_scope(Gc *gc)
{
    struct Scope scope = {
        .expr = CONS(gc, NIL(gc), NIL(gc))
    };
    return scope;
}

void set_scope_value(Gc *gc, struct Scope *scope, struct Expr name, struct Expr value)
{
    scope->expr = set_scope_value_impl(gc, scope->expr, name, value);
}

void push_scope_frame(Gc *gc, struct Scope *scope, struct Expr vars, struct Expr args)
{
    trace_assert(gc);
    trace_assert(scope);

    struct Expr frame = NIL(gc);

    while(!nil_p(vars) && !nil_p(args)) {
        frame = CONS(gc,
                     CONS(gc, vars.cons->car, args.cons->car),
                     frame);
        vars = vars.cons->cdr;
        args = args.cons->cdr;
    }

    scope->expr = CONS(gc, frame, scope->expr);
}

void pop_scope_frame(Gc *gc, struct Scope *scope)
{
    trace_assert(gc);
    trace_assert(scope);

    if (!nil_p(scope->expr)) {
        scope->expr = scope->expr.cons->cdr;
    }
}