import mem:*
import str:*
import vec:*
import util:*
import tree:*
import ast:*
import binding:*

adt type {
    _unknown,
    _void,
    _template_placeholder,
    _ptr: *binding<type>,
    _ref: *binding<type>,
    _obj: *tree<ast>,
    // triple<pair<param_types, return_type>, is_variadic, is raw>
    _fun: triple<pair<vec<*binding<type>>, *binding<type>>, bool, bool>,
    _bool,
    _char,
    _uchar,
    _short,
    _ushort,
    _int,
    _uint,
    _long,
    _ulong,
    _float,
    _double
}

fun unify(t1: *binding<type>, t2: *binding<type>) {
    println("attempting to unify " + to_string(t1->bound_to) + " and " + to_string(t2->bound_to))
    if (is_unknown(t1->bound_to)) {
        t1->set(t2->bound_to)
    } else if (is_unknown(t2->bound_to)) {
        t2->set(t1->bound_to)
    } else {
        if (shallow_equality(t1->bound_to, t2->bound_to)) {
            if (is_fun(t1->bound_to)) {
                unify(t1->bound_to->_fun.first.second, t2->bound_to->_fun.first.second)
                for (var i = 0; i < t1->bound_to->_fun.first.first.size; i++;)
                    unify(t1->bound_to->_fun.first.first[i], t2->bound_to->_fun.first.first[i])
            } else if (is_ptr(t1->bound_to)) {
                unify(t1->bound_to->_ptr, t2->bound_to->_ptr)
            } else if (is_obj(t1->bound_to)) {
                for (var i = 0; i < t1->bound_to->_obj->data._binding.second.size; i++;) {
                    unify(t1->bound_to->_obj->data._binding.second[i], t2->bound_to->_obj->data._binding.second[i])
                }
            }
        } else {
            error("Doesn't typecheck! Attempted to unify " + to_string(t1->bound_to) + " and " + to_string(t2->bound_to))
        }
    }
}
fun shallow_equality(a: *type, b: *type):bool {
    if (is_ptr(a) != is_ptr(b))
        return false
    if (is_ptr(a) && is_ptr(b))
        return true
    match(*a) {
        type::_fun(x) {
            return is_fun(b) && a->_fun.third == b->_fun.third
        }
        type::_obj(x) {
            return is_obj(b) && (get_ast_binding(x) == get_ast_binding(b->_obj) || ((!ast_bound(x) || !ast_bound(b->_obj))
                                                                                    && x->data._binding.second.size == b->_obj->data._binding.second.size
                                                                                    && x->data._binding.first == b->_obj->data._binding.first))
        }
    }
    return *a == *b
}

fun inst_temp_type(t: *binding<type>, replacements: ref map<*binding<type>, *binding<type>>): *binding<type> {
    match (*t->bound_to) {
        type::_unknown() error("Unknown in temp type")
        type::_obj(o) {
            var binding_types = o->data._binding.second.map(fun(b: *binding<type>): *binding<type> return inst_temp_type(b, replacements);)
            for (var i = 0; i < o->data._binding.second.size; i++;) {
                if (o->data._binding.second[i] != binding_types[i])
                    return binding_p(type::_obj(_binding(o->data._binding.first, binding_types, o->data._binding.third)))
            }
        }
        type::_ptr(p) {
            var cp = inst_temp_type(p, replacements)
            if (cp == p)
                return t
            else
                return binding_p(type::_ptr(cp))
        }
        type::_ref(r) {
            var cr = inst_temp_type(r, replacements)
            if (cr == r)
                return t
            else
                return binding_p(type::_ref(cr))
        }
        type::_fun(b) {
            // triple<pair<param_types, return_type>, is_variadic, is raw>
            var rt = inst_temp_type(b.first.second, replacements)
            var pts = b.first.first.map(fun(pt: *binding<type>): *binding<type> return inst_temp_type(pt, replacements);)
            if (rt != b.first.second)
                return binding_p(type::_fun(make_triple(make_pair(pts, rt), b.second, b.third)))
            for (var i = 0; i < pts.size; i++;)
                if (pts[i] != b.first.first[i])
                    return binding_p(type::_fun(make_triple(make_pair(pts, rt), b.second, b.third)))
            return t
        }
        type::_template_placeholder()  return replacements[t]
    }
    return t
}

fun equality(a: *type, b: *type, count_unknown_as_equal: bool): bool {
    /*println("equality of  " + to_string(a) + " and " + to_string(b))*/
    if (count_unknown_as_equal && (is_unknown(a) || is_unknown(b)))
        return true
    match(*a) {
        type::_obj(x) {
            if (!is_obj(b))
                return false
            if (get_ast_binding(x) == get_ast_binding(b->_obj))
                return true
            if (!count_unknown_as_equal || (ast_bound(x) && ast_bound(b->_obj)) || x->data._binding.first != b->_obj->data._binding.first ||  x->data._binding.second.size != b->_obj->data._binding.second.size)
                return false
            for (var i = 0; i < x->data._binding.second.size; i++;) {
                if (!equality(x->data._binding.second[i]->bound_to, b->_obj->data._binding.second[i]->bound_to, count_unknown_as_equal))
                    return false
            }
            return true
        }
        type::_ptr(p) {
            if (!is_ptr(b))
                return false
            return equality(p->bound_to, b->_ptr->bound_to, count_unknown_as_equal)
        }
        type::_ref(r) {
            if (!is_ref(b))
                return false
            return equality(r->bound_to, b->_ref->bound_to, count_unknown_as_equal)
        }
        type::_fun(i) {
            if ( !(is_fun(b) && a->_fun.second == b->_fun.second && a->_fun.third == b->_fun.third) )
                return false
            if ( !equality(a->_fun.first.second->bound_to, b->_fun.first.second->bound_to, count_unknown_as_equal) )
                return false
            if ( !(a->_fun.first.first.size == b->_fun.first.first.size) )
                return false
            for (var i = 0; i < a->_fun.first.first.size; i++;)
                if ( !equality(a->_fun.first.first[i]->bound_to, b->_fun.first.first[i]->bound_to, count_unknown_as_equal) )
                    return false
            return true
        }
    }
    return *a == *b
}
fun to_string(it: *type): str {
    match (*it) {
        type::_unknown()               return str("_unknown")
        type::_void()                  return str("_void")
        type::_ptr(p)                  return "*"   + to_string(p->bound_to)
        type::_ref(r)                  return "ref" + to_string(r->bound_to)
        type::_obj(b) {
            return "_obj(" + to_string(b->data) + ")"
        }
        type::_fun(b) {
            // triple<pair<param_types, return_type>, is_variadic, is raw>
            var to_ret = str()
            if (b.second)
                to_ret += "_run("
            else
                to_ret += "_fun("
            to_ret += str(", ").join(b.first.first.map(fun(pt: *binding<type>): str return to_string(pt->bound_to);))
            if (b.third)
                to_ret += " ..."
            return to_ret + "): " + to_string(b.first.second->bound_to)
        }
        type::_template_placeholder()  return str("_template_placeholder")
        type::_bool()                  return str("_bool")
        type::_char()                  return str("_char")
        type::_uchar()                 return str("_uchar")
        type::_short()                 return str("_short")
        type::_ushort()                return str("_ushort")
        type::_int()                   return str("_int")
        type::_uint()                  return str("_uint")
        type::_long()                  return str("_long")
        type::_ulong()                 return str("_ulong")
        type::_float()                 return str("_float")
        type::_double()                return str("_double")
    }
    return str("impossible type")
}
fun is_unknown(x: *type): bool {
    match (*x) {
        type::_unknown() return true
    }
    return false
}
fun is_void(x: *type): bool {
    match (*x) {
        type::_void() return true
    }
    return false
}
fun is_ptr(x: *type): bool {
    match (*x) {
        type::_ptr(p) return true
    }
    return false
}
fun is_ref(x: *type): bool {
    match (*x) {
        type::_ref(r) return true
    }
    return false
}
fun is_obj(x: *type): bool {
    match (*x) {
        type::_obj() return true
    }
    return false
}
fun is_fun(x: *type): bool {
    match (*x) {
        type::_fun(b) return true
    }
    return false
}
fun is_template_placeholder(x: *type): bool {
    match (*x) {
        type::_template_placeholder() return true
    }
    return false
}
fun is_bool(x: *type): bool {
    match (*x) {
        type::_bool() return true
    }
    return false
}
fun is_char(x: *type): bool {
    match (*x) {
        type::_char() return true
    }
    return false
}
fun is_uchar(x: *type): bool {
    match (*x) {
        type::_uchar() return true
    }
    return false
}
fun is_short(x: *type): bool {
    match (*x) {
        type::_short() return true
    }
    return false
}
fun is_ushort(x: *type): bool {
    match (*x) {
        type::_ushort() return true
    }
    return false
}
fun is_int(x: *type): bool {
    match (*x) {
        type::_int() return true
    }
    return false
}
fun is_uint(x: *type): bool {
    match (*x) {
        type::_uint() return true
    }
    return false
}
fun is_long(x: *type): bool {
    match (*x) {
        type::_long() return true
    }
    return false
}
fun is_ulong(x: *type): bool {
    match (*x) {
        type::_ulong() return true
    }
    return false
}
fun is_float(x: *type): bool {
    match (*x) {
        type::_float() return true
    }
    return false
}
fun is_double(x: *type): bool {
    match (*x) {
        type::_double() return true
    }
    return false
}
fun is_signed(x: *type): bool {
    match (*x) {
        type::_char()      return true
        type::_int()       return true
        type::_long()      return true
        type::_short()     return true
        type::_float()     return true
        type::_double()    return true

        type::_uchar()     return false
        type::_ushort()    return false
        type::_uint()      return false
        type::_ulong()     return false
    }
    return false
}