integration/luprex/cpp/core/animqueue.cpp

#include "wrap-sstream.hpp"
#include "wrap-map.hpp"
#include "util.hpp"
#include "animqueue.hpp"
#include "luastack.hpp"
#include "streambuffer.hpp"

#include <limits>
#include <cmath>
#include <cstdlib>

static const char *vtname(AnimValueType vt) {
    switch (vt) {
        case T_UNINITIALIZED: return "uninitialized";
        case T_BOOLEAN: return "boolean";
        case T_NUMBER: return "number";
        case T_STRING: return "string";
        case T_XYZ: return "xyz";
        default: return "unknown";
    }
}


uint64_t hash_encstep(uint64_t prev, std::string_view s) {
    return util::hash_string(util::HashValue(123, prev), s).first;
}

void AnimValue::set_boolean(bool b) {
    type = T_BOOLEAN;
    str.clear();
    xyz = (b ? 1.0:0.0);
}

void AnimValue::set_number(double n) {
    type = T_NUMBER;
    str.clear();
    xyz = util::DXYZ(n, 0, 0);
}

void AnimValue::set_xyz(const util::DXYZ &v) {
    type = T_XYZ;
    str.clear();
    xyz = v;
}

void AnimValue::set_string(std::string_view sv) {
    type = T_STRING;
    str = sv;
    xyz = 0.0;
}

bool AnimValue::get_boolean() const {
    if (type != T_BOOLEAN) return false;
    return (xyz.x == 1.0);
}

double AnimValue::get_number() const {
    if (type != T_NUMBER) return 0.0;
    return xyz.x;
}

const util::DXYZ &AnimValue::get_xyz() const {
    static util::DXYZ zero;
    if (type != T_XYZ) return zero;
    return xyz;
}

std::string_view AnimValue::get_string() const {
    if (type != T_STRING) return std::string_view("");
    return std::string_view(str);
}

void AnimValue::copy_value(const AnimValue &other) {
    type = other.type;
    str = other.str;
    xyz = other.xyz;
}

static void encode_value(StreamBuffer *sb, const AnimValue *v) {
    sb->write_uint8(uint8_t(v->type));
    switch(v->type) {
        case T_NUMBER: sb->write_double(v->xyz.x); break;
        case T_BOOLEAN: sb->write_bool(v->xyz.x == 1.0); break;
        case T_XYZ: sb->write_dxyz(v->xyz); break;
        case T_STRING: sb->write_string(v->str); break;
        default: assert(false);
    }
}

static void decode_value(StreamBuffer *sb, AnimValue *v) {
    AnimValueType type = AnimValueType(sb->read_uint8());
    switch (type) {
        case T_NUMBER: v->set_number(sb->read_double()); break;
        case T_BOOLEAN: v->set_boolean(sb->read_bool()); break;
        case T_XYZ: v->set_xyz(sb->read_dxyz()); break;
        case T_STRING: v->set_string(sb->read_string()); break;
        default: assert(false);
    }
}

// Parse a value.  This is meant for unit testing only.  The
// parser isn't powerful enough to express all possible values.
static void parse_value(std::string_view vstr, AnimValue *v) {
    // Try to interpret vstr as a boolean.
    bool is_true = (vstr == "true");
    bool is_false = (vstr == "false");
    if (is_true || is_false) {
        v->set_boolean(is_true);
        return;
    }
    // Try to interpret vstr as a number.
    if (sv::valid_number(vstr, true, true, true, false)) {
        v->set_number(std::atof(std::string(vstr).c_str()));
        return;
    }
    // Try to interpret vstr as a vector.
    eng::vector<eng::string> parts = util::split(eng::string(vstr), ',');
    if ((parts.size() == 3) &&
        (sv::valid_number(parts[0], true, true, true, false)) &&
        (sv::valid_number(parts[1], true, true, true, false)) &&
        (sv::valid_number(parts[2], true, true, true, false))) {
        double x = std::atof(parts[0].c_str());
        double y = std::atof(parts[1].c_str());
        double z = std::atof(parts[2].c_str());
        v->set_xyz(util::DXYZ(x,y,z));
        return;
    }
    // If it doesn't parse as any of the above, it's a string.
    v->set_string(vstr);
}


static AnimValue parse_anim_value(LuaCoreStack &LS, LuaSlot val, LuaSlot tmp) {
    AnimValue result;
    if (LS.isboolean(val)) {
        result.set_boolean(LS.ckboolean(val));
    } else if (LS.isnumber(val)) {
        result.set_number(LS.cknumber(val));
    } else if (LS.isstring(val)) {
        result.set_string(LS.ckstring(val));
    } else if (LS.istable(val)) {
        util::DXYZ xyz;
        LS.rawget(tmp, val, 1);
        if (!LS.isnumber(tmp)) return result;
        xyz.x = LS.cknumber(tmp);
        LS.rawget(tmp, val, 2);
        if (!LS.isnumber(tmp)) return result;
        xyz.y = LS.cknumber(tmp);
        LS.rawget(tmp, val, 3);
        if (!LS.isnumber(tmp)) return result;
        xyz.z = LS.cknumber(tmp);
        result.set_xyz(xyz);
    }
    return result;
}

void AnimState::set_persistent(const eng::string &name) {
    map_[name].persistent = true;
}

bool AnimState::get_boolean(const eng::string &name) {
    auto iter = map_.find(name);
    if (iter == map_.end()) return false;
    return iter->second.get_boolean();
}

double AnimState::get_number(const eng::string &name) {
    auto iter = map_.find(name);
    if (iter == map_.end()) return 0.0;
    return iter->second.get_number();
}

util::DXYZ AnimState::get_xyz(const eng::string &name) {
    static util::DXYZ zero;
    auto iter = map_.find(name);
    if (iter == map_.end()) return zero;
    return iter->second.get_xyz();
}

std::string_view AnimState::get_string(const eng::string &name) {
    auto iter = map_.find(name);
    if (iter == map_.end()) return std::string_view("");
    return iter->second.get_string();
}


void AnimState::set_boolean(const eng::string &name, bool v) {
    AnimValue &value = map_[name];
    value.set_boolean(v);
}

void AnimState::set_number(const eng::string &name, double v) {
    AnimValue &value = map_[name];
    value.set_number(v);
}

void AnimState::set_xyz(const eng::string &name, const util::DXYZ &v) {
    AnimValue &value = map_[name];
    value.set_xyz(v);
}

void AnimState::set_string(const eng::string &name, std::string_view v) {
    AnimValue &value = map_[name];
    value.set_string(v);
}

void AnimState::print_debug_string(eng::ostringstream &oss) {
    bool first = true;
    if (map_.empty()) {
        oss << "[empty]";
    }
    for (const auto &pair : map_) {
        if (!first) oss << " ";
        const eng::string &name = pair.first;
        const AnimValue &value = pair.second;
        oss << name;
        if (value.persistent) {
            oss << "=";
        } else {
            oss << ":";
        }
        switch (value.type) {
            case T_NUMBER: oss << value.xyz.x; break;
            case T_BOOLEAN: oss << ((value.xyz.x == 1.0) ? "true":"false"); break;
            case T_XYZ: oss << value.xyz; break;
            case T_STRING: oss << value.str; break;
            default: assert(false);
        }
        first = false;
    }
}

eng::string AnimState::debug_string() {
    eng::ostringstream oss;
    print_debug_string(oss);
    return oss.str();
}

eng::string AnimState::encode() const {
    StreamBuffer sb;
    for (const auto &pair : map_) {
        const eng::string &name = pair.first;
        const AnimValue &value = pair.second;
        sb.write_string(name);
        sb.write_bool(value.persistent);
        encode_value(&sb, &value);
    }
    return sb.read_entire_contents();
}

void AnimState::decode(std::string_view s) {
    map_.clear();
    StreamBuffer sb(s);
    while (!sb.empty()) {
        eng::string name = sb.read_string();
        bool persistent = sb.read_bool();
        AnimValue &value = map_[name];
        value.persistent = persistent;
        decode_value(&sb, &value);
    }
}

void AnimState::decode_persistent(std::string_view s) {
    map_.clear();
    StreamBuffer sb(s);
    AnimValue dummy;
    while (!sb.empty()) {
        eng::string name = sb.read_string();
        bool persistent = sb.read_bool();
        if (persistent) {
            AnimValue &value = map_[name];
            value.persistent = persistent;
            decode_value(&sb, &value);
        } else {
            decode_value(&sb, &dummy);
        }
    }
}

eng::string AnimState::add_default(const eng::string &name, const AnimValue &def, const AnimState *other) {
    AnimValue &value = map_[name];
    value.persistent = true;
    if (value.type == T_UNINITIALIZED) {
        if (other != nullptr) {
            auto otheriter = other->map_.find(name);
            if (otheriter != other->map_.end()) {
                if (otheriter->second.persistent && otheriter->second.type == def.type) {
                    value.copy_value(otheriter->second);
                    return "";
                }
            }
        }
        value.copy_value(def);
        return "";
    }
    if (value.type != def.type) {
        return util::ss("Animation key ", name, " must be a ", vtname(def.type));
    }
    return "";
}

eng::string AnimState::add_defaults(const AnimState *other) {
    eng::string err;
    AnimValue defval;

    defval.set_xyz(util::DXYZ(0,0,0));
    err = add_default("xyz", defval, other);
    if (!err.empty()) return err;

    defval.set_string("nowhere");
    err = add_default("plane", defval, other);
    if (!err.empty()) return err;
    
    defval.set_number(0.0);
    err = add_default("facing", defval, other);
    if (!err.empty()) return err;
    
    defval.set_string("stdbp");
    err = add_default("bp", defval, other);
    if (!err.empty()) return err;

    defval.set_string("stdmodel");
    err = add_default("model", defval, other);
    if (!err.empty()) return err;

    return "";
}


eng::string AnimState::apply_lua(LuaCoreStack &LS0, LuaSlot tab, bool setpersist) {
    LuaVar key, val, tmp;
    LuaExtStack LS(LS0.state(), key, val, tmp);
    util::DXYZ xyz;
    
    if (!LS.istable(tab)) {
        return "An animstate must be a table.";
    }
    LS.set(key, LuaNil);
    while (LS.next(tab, key, val)) {
        if (!LS.isstring(key)) {
            return "in animation key-value pairs, key must be a string.";
        }
        AnimValue parsedvalue = parse_anim_value(LS, val, tmp);
        if (parsedvalue.type == T_UNINITIALIZED) {
            return "in animation key-value pairs, val must be number, string, boolean, or xyz";
        }
        eng::string name = LS.ckstring(key);
        AnimValue &mapentry = map_[name];
        if ((mapentry.type != T_UNINITIALIZED) && (mapentry.type != parsedvalue.type)) {
            return util::ss("animation '", name, "' must be a ", vtname(mapentry.type));
        }
        mapentry.copy_value(parsedvalue);
        if (setpersist) mapentry.persistent = true;
    }
    return "";
}

void AnimState::to_lua(LuaCoreStack &LS0, LuaSlot tab, bool persistent) {
    LuaVar name, val;
    LuaExtStack LS(LS0.state(), name, val);
    LS.newtable(tab);
    for (const auto &pair : map_) {
        if (pair.second.persistent != persistent) continue;
        LS.set(name, pair.first);
        const AnimValue &value = pair.second;
        if (value.type == T_BOOLEAN) {
            LS.set(val, value.get_boolean());
        } else if (value.type == T_NUMBER) {
            LS.set(val, value.get_number());
        } else if (value.type == T_STRING) {
            LS.set(val, value.get_string());
        } else if (value.type == T_XYZ) {
            LS.newtable(val);
            LS.rawset(val, 1, value.get_xyz().x);
            LS.rawset(val, 2, value.get_xyz().y);
            LS.rawset(val, 3, value.get_xyz().z);
        }
        LS.rawset(tab, name, val);
    }
}

// The syntax used by this parser is not general enough to represent all
// possible strings.  That's OK, though, since it's just for unit testing.
void AnimState::parse(std::string_view config) {
    while (true) {
        config = sv::ltrim(config);
        if (config.empty()) break;
        eng::string name(sv::read_ascii_identifier(config));
        assert(!name.empty());
        AnimValue &value = map_[name];
        bool has_equal = sv::has_prefix(config, "=");
        bool has_colon = sv::has_prefix(config, ":");
        assert(has_equal || has_colon);
        config.remove_prefix(1);
        value.persistent = has_equal;
        eng::string vstr(sv::read_to_space(config));
        parse_value(vstr, &value);
    }
}

void AnimState::clear_and_parse(std::string_view config) {
    map_.clear();
    parse(config);
}

void AnimCoreState::decode(std::string_view s) {
    plane.clear();
    xyz = 0.0;
    StreamBuffer sb(s);
    AnimValue value;
    while (!sb.empty()) {
        eng::string name = sb.read_string();
        bool persistent = sb.read_bool();
        decode_value(&sb, &value);
        if (persistent) {
            if ((name == "xyz") && (value.type == T_XYZ)) xyz = value.xyz;
            if ((name == "plane") && (value.type == T_STRING)) plane = value.str;
        }
    }
}

int AnimQueue::get_size_limit() const {
    StreamBuffer sb(*encqueue_);
    return sb.read_uint8();
}

int AnimQueue::get_actual_size() const {
    StreamBuffer sb(*encqueue_);
    sb.read_bytes(1);
    return sb.read_uint8();
}

uint64_t AnimQueue::get_final_hash() const {
    StreamBuffer sb(*encqueue_);
    sb.read_bytes(2);
    return sb.read_uint64();
}

std::string_view AnimQueue::get_final_encstep() const {
    StreamBuffer sb(*encqueue_);
    sb.read_bytes(10);
    return sb.read_string_view();
}

void AnimQueue::update_encqueue(int limit, bool add, std::string_view add_enc, bool keepold) {
    // Make sure the size limit is reasonable.
    assert((limit >= 2) && (limit <= 250));

    // You must either add a new step or retain an old step.  The queue can't be empty.
    assert(keepold || add);

    // Find out how many old steps we'll be retaining, ignoring the size limit.
    int nretain = 0;
    if (keepold) nretain = get_actual_size();
    
    // If retaining all steps would overflow the size limit, retain fewer.
    int retain_limit = limit;
    if (add) retain_limit -= 1;
    if (nretain > retain_limit) nretain = retain_limit;

    // Calculate the new size of the queue.
    int new_size = add ? (nretain + 1) : nretain;
    
    // If we're retaining steps, extract them from the old queue.
    std::string_view retain;
    if (nretain > 0) {
        std::string_view oldqueue(*encqueue_);
        StreamBuffer sb(oldqueue);
        sb.read_bytes(2); // Skip over the header.
        int pos1 = sb.total_reads();
        for (int i = 0; i < nretain; i++) {
            sb.read_uint64();
            sb.read_string_view();
        }
        int pos2 = sb.total_reads();
        retain = oldqueue.substr(pos1, pos2 - pos1);
    }

    // If we're adding a step, calculate its hash.
    uint64_t add_hash = 0;
    if (add) {
        uint64_t prev_hash = 0;
        if (nretain > 0) prev_hash = get_final_hash();
        add_hash = hash_encstep(prev_hash, add_enc);
    }

    // Finally, encode everything into a binary blob.
    StreamBuffer result;
    result.write_uint8(limit);
    result.write_uint8(new_size);
    if (add) {
        result.write_uint64(add_hash);
        result.write_string(add_enc);
    }
    result.write_bytes(retain);

    // Replace the shared string.
    encqueue_ = std::make_shared<std::string>(result.view());
}

AnimQueue::AnimQueue() {
    update_encqueue(10, true, AnimState().encode(), false);
}

void AnimQueue::clear(const AnimState &state) {
    update_encqueue(get_size_limit(), true, state.encode(), false);
}

void AnimQueue::clear() {
    update_encqueue(get_size_limit(), true, AnimState().encode(), false);
}

void AnimQueue::set_limit(int limit) {
    update_encqueue(limit, false, "", true);
}

void AnimQueue::add(const AnimState &state) {
    update_encqueue(get_size_limit(), true, state.encode(), true);
}

void AnimQueue::serialize(StreamBuffer *sb) const {
    sb->write_string(*encqueue_);
}

void AnimQueue::deserialize(StreamBuffer *sb) {
    encqueue_ = std::make_shared<std::string>(sb->read_string_view());
}

bool AnimQueue::diff(const AnimQueue &auth, StreamBuffer *sb) const {
    // Fast check for exactly equivalent.  If equivalent, skip all the work.
    if (exactly_equal_fast(auth)) {
        assert(exactly_equal(auth));
        sb->write_bool(false);
        return false;
    }

    // TODO: maybe send less data?
    sb->write_bool(true);
    sb->write_string(*auth.encqueue_);
    return true;
}

void AnimQueue::patch(StreamBuffer *sb, DebugCollector *dbc) {
    bool changed = sb->read_bool();
    if (!changed) {
        return;
    }
    DebugLine(dbc) << "AnimQueue modified";
    encqueue_ = std::make_shared<std::string>(sb->read_string_view());
}

bool AnimQueue::exactly_equal(const AnimQueue &other) const {
    if (*encqueue_ != *other.encqueue_) return false;
    return true;
}

bool AnimQueue::exactly_equal_fast(const AnimQueue &other) const {
    if (encqueue_->size() != other.encqueue_->size()) return false;
    if (encqueue_->compare(0, 10, *other.encqueue_) != 0) return false;
    return true;
}

void AnimQueue::print_debug_string(eng::ostringstream &oss, bool full) const {
    bool first = true;
    // Break out the steps.
    eng::vector<std::string_view> encsteps;
    StreamBuffer sb(*encqueue_); 
    int size_limit = sb.read_uint8();
    int actual_size = sb.read_uint8();
    if (full) {
        oss << "limit=" << size_limit;
        first = false;
    }
    for (int i = 0; i < actual_size; i++) {
        sb.read_uint64();
        encsteps.push_back(sb.read_string_view());
    }
    assert(sb.empty());
    for (int i = encsteps.size() - 1; i >= 0; i --) {
        if (!first) oss << "; ";
        AnimState state(encsteps[i]);
        state.print_debug_string(oss);
        first = false;
    }
}

eng::string AnimQueue::steps_debug_string() const {
    eng::ostringstream oss;
    print_debug_string(oss, false);
    return oss.str();
}

eng::string AnimQueue::full_debug_string() const {
    eng::ostringstream oss;
    print_debug_string(oss, true);
    return oss.str();
}

AnimCoreState AnimQueue::get_final_core_state() const {
    std::string_view encstep = get_final_encstep();
    AnimCoreState result;
    result.decode(encstep);
    return result;
}

AnimState AnimQueue::get_final_persistent() const {
    std::string_view encstep = get_final_encstep();
    AnimState result;
    result.decode_persistent(encstep);
    return result;
}

AnimState AnimQueue::get_final_everything() const {
    std::string_view encstep = get_final_encstep();
    AnimState result;
    result.decode(encstep);
    return result;
}

LuaDefine(unittests_animqueue, "", "some unit tests") {
    // Useful objects.
    AnimQueue aq, aqs;
    StreamBuffer sb;
    AnimState astate;
    eng::string enc;
    AnimCoreState core;
    
    // Debug string of a newly initialized queue
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; [empty]");
    
    // Test AnimState simple setters.
    astate.set_string("color", "blue");
    astate.set_xyz("xyz", util::DXYZ(1,2,3));
    astate.set_number("half", 0.5);
    astate.set_boolean("nice", true);
    LuaAssertStrEq(L, astate.debug_string(), "color:blue half:0.5 nice:true xyz:1,2,3");

    // Test AnimState simple getters.
    LuaAssert(L, astate.get_string("color") == "blue");
    LuaAssert(L, astate.get_xyz("xyz") == util::DXYZ(1,2,3));
    LuaAssert(L, astate.get_number("half") == 0.5);
    LuaAssert(L, astate.get_boolean("nice") == true);

    // Test AnimState simple getters on nonexistent data.
    LuaAssert(L, astate.get_string("q") == "");
    LuaAssert(L, astate.get_xyz("q") == util::DXYZ(0,0,0));
    LuaAssert(L, astate.get_number("q") == 0.0);
    LuaAssert(L, astate.get_boolean("q") == false);

    // Test AnimState simple getters on wrong-type data.
    LuaAssert(L, astate.get_string("half") == "");
    LuaAssert(L, astate.get_xyz("half") == util::DXYZ(0,0,0));
    LuaAssert(L, astate.get_number("color") == 0.0);
    LuaAssert(L, astate.get_boolean("color") == false);

    // Test AnimState persistence manipulation.
    astate.set_persistent("color");
    astate.set_persistent("nice");
    LuaAssertStrEq(L, astate.debug_string(), "color=blue half:0.5 nice=true xyz:1,2,3");

    // Test AnimState parser.
    astate.clear_and_parse("color:green mean=true pos=3,4,5 ok:false");
    LuaAssertStrEq(L, astate.debug_string(), "color:green mean=true ok:false pos=3,4,5");

    // Test animstate encoding and decoding.
    astate.clear_and_parse("color:green mean=true pos=3,4,5 ok:false");
    enc = astate.encode();
    astate.clear();
    astate.decode(enc);
    LuaAssertStrEq(L, astate.debug_string(), "color:green mean=true ok:false pos=3,4,5");
    astate.decode_persistent(enc);
    LuaAssertStrEq(L, astate.debug_string(), "mean=true pos=3,4,5");
    
    // Test AnimCoreState.decode
    //
    astate.clear_and_parse("color=blue xyz=1,2,3 plane=banana chicken=3");
    core.decode(astate.encode());
    LuaAssert(L, core.plane == "banana");
    LuaAssert(L, core.xyz == util::DXYZ(1,2,3));

    // Verify that a newly-constructed AnimQueue is in a reasonable default state.
    //
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; [empty]");

    // Clear an AnimQueue to a specified initial state.
    //
    astate.clear_and_parse("color=blue xyz=1,2,3 plane=somewhere");
    aq.clear(astate);
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; color=blue plane=somewhere xyz=1,2,3");

    // Add animation steps to animation queue.
    // Note: each step is independent of the previous one, no composition is being done.
    //
    astate.clear_and_parse("xyz=1,2,3 plane=earth");
    aq.clear(astate);
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; plane=earth xyz=1,2,3");
    astate.clear_and_parse("xyz=4,5,6 action:jump");
    aq.add(astate);
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; plane=earth xyz=1,2,3; action:jump xyz=4,5,6");
    astate.clear_and_parse("plane=moon airline:southwest");
    aq.add(astate);
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; plane=earth xyz=1,2,3; action:jump xyz=4,5,6; airline:southwest plane=moon");
    astate.clear_and_parse("color=blue");
    aq.add(astate);    
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; plane=earth xyz=1,2,3; action:jump xyz=4,5,6; airline:southwest plane=moon; color=blue");

    // Try reducing the animation queue size limit.
    //
    aq.set_limit(2);
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=2; airline:southwest plane=moon; color=blue");

    // Test get_final_persistent, get_final_everything, get_final_core_state
    //
    astate.clear_and_parse("action:jump plane=earth xyz=1,2,3 bouncy:true");
    aq.clear(astate);
    astate = aq.get_final_persistent();
    LuaAssertStrEq(L, astate.debug_string(), "plane=earth xyz=1,2,3");
    astate = aq.get_final_everything();
    LuaAssertStrEq(L, astate.debug_string(), "action:jump bouncy:true plane=earth xyz=1,2,3");
    core = aq.get_final_core_state();
    LuaAssert(L, core.plane == "earth");
    LuaAssert(L, core.xyz == util::DXYZ(1,2,3));

    // Serialize a queue.
    //
    aq.set_limit(10);
    astate.clear_and_parse("xyz=1,2,3 plane=earth");
    aq.clear(astate);
    astate.clear_and_parse("xyz=4,5,6 action:jump");
    aq.add(astate);
    astate.clear_and_parse("plane=moon airline:southwest");
    aq.add(astate);
    astate.clear_and_parse("color=blue");
    aq.add(astate);    
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; plane=earth xyz=1,2,3; action:jump xyz=4,5,6; airline:southwest plane=moon; color=blue");
    aq.serialize(&sb);
    
    // Deserialize a queue.
    //
    aqs.set_limit(7);
    aqs.clear();
    LuaAssert(L, !aqs.exactly_equal(aq));
    aqs.deserialize(&sb);
    LuaAssert(L, aqs.exactly_equal(aq));
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; plane=earth xyz=1,2,3; action:jump xyz=4,5,6; airline:southwest plane=moon; color=blue");
    
    // Test diff and patch.
    //
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; plane=earth xyz=1,2,3; action:jump xyz=4,5,6; airline:southwest plane=moon; color=blue");
    aqs.set_limit(7);
    aqs.clear();
    sb.clear();
    aqs.diff(aq, &sb);
    //int difflen1 = sb.fill();
    LuaAssert(L, !aqs.exactly_equal(aq));
    aqs.patch(&sb, nullptr);
    LuaAssert(L, aqs.exactly_equal(aq));
    LuaAssertStrEq(L, aqs.full_debug_string(), "limit=10; plane=earth xyz=1,2,3; action:jump xyz=4,5,6; airline:southwest plane=moon; color=blue");
    
    // Test that diff and patch are more efficient when the two queues contain some shared steps.
    //
    LuaAssertStrEq(L, aq.full_debug_string(), "limit=10; plane=earth xyz=1,2,3; action:jump xyz=4,5,6; airline:southwest plane=moon; color=blue");
    astate.clear_and_parse("xyz=4,5,6 action:jump");
    aqs.clear(astate);
    astate.clear_and_parse("plane=earth xyz=1,2,3");
    aqs.add(astate);
    astate.clear_and_parse("plane=moon airline:southwest");
    aqs.add(astate);
    LuaAssertStrEq(L, aqs.full_debug_string(), "limit=10; action:jump xyz=4,5,6; plane=earth xyz=1,2,3; airline:southwest plane=moon");
    sb.clear();
    aqs.diff(aq, &sb);
    //int difflen2 = sb.fill();
    LuaAssert(L, !aqs.exactly_equal(aq));
    aqs.patch(&sb, nullptr);
    LuaAssert(L, aqs.exactly_equal(aq));
    LuaAssertStrEq(L, aqs.full_debug_string(), "limit=10; plane=earth xyz=1,2,3; action:jump xyz=4,5,6; airline:southwest plane=moon; color=blue");

    // TODO: if we make the diff routine more efficient, this should be true.
    // LuaAssert(L, difflen2 < (difflen1 / 2));

    return 0;
}