////////////////////////////////////////////////////////////////////
//
// This file contains the code to compare the contents of tables.
// The top level functions in this file are:
//
//  World::diff_lua_tables
//  World::diff_tangible_databases
//
// This file also contains all the support code needed to implement
// this stuff.
//
////////////////////////////////////////////////////////////////////

#include "luastack.hpp"
#include "streambuffer.hpp"
#include "world.hpp"

// Given a table and an tnmap, return the table number of the table.
// Returns zero if the table doesn't have a table number.
//
static int get_table_number(LuaStack &MLS, LuaSlot mval, LuaSlot mtnmap) {
    lua_State *L = MLS.state();
    lua_pushvalue(L, mval.index());
    lua_rawget(L, mtnmap.index());
    int result = 0;
    if (lua_type(L, -1) == LUA_TNUMBER) {
        result = lua_tointeger(L, -1);
    }
    lua_pop(L, 1);
    return result;
}


static bool equivalent_values(LuaStack &MLS, LuaSlot mval, LuaSlot mtnmap,
                              LuaStack &SLS, LuaSlot sval, LuaSlot stnmap) {
    switch (MLS.xtype(mval)) {
    case LUA_TBOOLEAN: {
        if (SLS.type(sval) != LUA_TBOOLEAN) return false;
        return MLS.ckboolean(mval) == SLS.ckboolean(sval);
    }
    case LUA_TNUMBER: {
        if (SLS.type(sval) != LUA_TNUMBER) return false;
        return MLS.cknumber(mval) == SLS.cknumber(sval);
    }
    case LUA_TSTRING: {
        // This could be faster if I used lua_tolstring directly.
        if (SLS.type(sval) != LUA_TSTRING) return false;
        return MLS.ckstring(mval) == SLS.ckstring(sval);
    }
    case LUA_TFUNCTION: {
        // Cannot really compare.  Just return true if the types match.
        return SLS.type(sval) == MLS.type(mval);
    }
    case LUA_TT_GENERAL: {
        if (SLS.xtype(sval) != LUA_TT_GENERAL) return false;
        int midx = get_table_number(MLS, mval, mtnmap);
        if (midx == 0) return false;
        int sidx = get_table_number(SLS, sval, stnmap);
        if (sidx == 0) return false;
        return midx == sidx;
    }
    case LUA_TT_CLASS: {
        if (SLS.xtype(sval) != LUA_TT_CLASS) return false;
        return MLS.classname(mval) == SLS.classname(sval);
    }
    case LUA_TT_TANGIBLE: {
        if (SLS.xtype(sval) != LUA_TT_TANGIBLE) return false;
        return World::tangible_id(MLS, mval) == World::tangible_id(SLS, sval);
    }
    case LUA_TT_GLOBALENV: {
        return (SLS.xtype(sval) == LUA_TT_GLOBALENV);
    }
    default:
        // We're forcing anything else to go to NIL,
        // and once it's NIL, we consider it 'equal'.
        return SLS.type(sval) == LUA_TNIL;
    }
}

static void transmit_value(LuaStack &MLS, LuaSlot mval, LuaSlot mtnmap, StreamBuffer *sb) {
    switch (MLS.xtype(mval)) {
    case LUA_TBOOLEAN: {
        sb->write_uint8(LUA_TBOOLEAN);
        sb->write_bool(MLS.ckboolean(mval));
        return;
    }
    case LUA_TNUMBER: {
        sb->write_uint8(LUA_TNUMBER);
        sb->write_double(MLS.cknumber(mval));
        return;
    }
    case LUA_TSTRING: {
        sb->write_uint8(LUA_TSTRING);
        sb->write_string(MLS.ckstring(mval));
        return;
    }
    case LUA_TT_GENERAL: {
        sb->write_uint8(LUA_TT_GENERAL);
        sb->write_uint32(get_table_number(MLS, mval, mtnmap));
        return;
    }
    case LUA_TT_CLASS: {
        sb->write_uint8(LUA_TT_CLASS);
        sb->write_string(MLS.classname(mval));
        return;
    }
    case LUA_TT_TANGIBLE: {
        sb->write_uint8(LUA_TT_TANGIBLE);
        sb->write_int64(World::tangible_id(MLS, mval));
        return;
    }
    case LUA_TT_GLOBALENV: {
        sb->write_uint8(LUA_TT_GLOBALENV);
        return;
    }
    default:
        sb->write_uint8(LUA_TNIL);
        return;
    }
}

static void transmit_value_debug_string(StreamBuffer *sb, std::ostringstream &oss) {
    int kind = sb->read_uint8();
    switch (kind) {
    case LUA_TBOOLEAN: {
        bool b = sb->read_bool();
        oss << (b ? "true":"false");
        return;
    }
    case LUA_TNUMBER: {
        oss << sb->read_double();
        return;
    }
    case LUA_TSTRING: {
        oss << sb->read_string();
        return;
    }
    case LUA_TT_GENERAL: {
        oss << "table " << sb->read_int32();
        return;
    }
    case LUA_TT_CLASS: {
        oss << "class " << sb->read_string();
        return;
    }
    case LUA_TT_TANGIBLE: {
        oss << "tan " << sb->read_int64();
        return;
    }
    case LUA_TT_GLOBALENV: {
        oss << "globals";
        return;
    }
    case LUA_TNIL: {
        oss << "nil";
        return;
    }
    default:
        assert(false); // Should not get here.
    }
}

static bool compare_tables(lua_State *synch, lua_State *master, bool cmeta, StreamBuffer *sb) {
    LuaArg mtnmap, mtab, stnmap, stab;
    LuaVar skey, mkey, sval, mval, mnil;
    LuaStack SLS(synch, stnmap, stab, skey, sval);
    LuaStack MLS(master, mtnmap, mtab, mkey, mval, mnil);
    MLS.set(mnil, LuaNil);
    int nupdates = 0;

    sb->write_int32(0);
    int wc = sb->total_writes();

    MLS.set(mkey, LuaNil);
    while (MLS.next(mtab, mkey, mval)) {
        if (!MLS.issortablekey(mkey)) continue;
        MLS.movesortablekey(mkey, SLS, skey);
        SLS.rawget(sval, stab, skey);
        if (!equivalent_values(MLS, mval, mtnmap, SLS, sval, stnmap)) {
            transmit_value(MLS, mkey, mtnmap, sb);
            transmit_value(MLS, mval, mtnmap, sb);
            nupdates += 1;
        }
    }

    SLS.set(skey, LuaNil);
    while (SLS.next(stab, skey, sval)) {
        if (!SLS.issortablekey(skey)) continue;
        SLS.movesortablekey(skey, MLS, mkey);
        MLS.rawget(mval, mtab, mkey);
        if (MLS.isnil(mval)) {
            transmit_value(MLS, mkey, mtnmap, sb);
            transmit_value(MLS, mval, mtnmap, sb);
            nupdates += 1;
        }
    }

    if (cmeta) {
        SLS.getmetatable(sval, stab);
        MLS.getmetatable(mval, mtab);
        if (!equivalent_values(MLS, mval, mtnmap, SLS, sval, stnmap)) {
            transmit_value(MLS, mnil, mtnmap, sb);
            transmit_value(MLS, mval, mtnmap, sb);
            nupdates += 1;
        }
    }

    sb->overwrite_int32(wc, nupdates);

    SLS.result();
    MLS.result();
    return (nupdates > 0);
}

static std::string compare_tables_debug_string(StreamBuffer *sb) {
    std::vector<std::string> sorted;
    std::ostringstream oss;
    int ndiffs = sb->read_int32();
    for (int i = 0; i < ndiffs; i++) {
        transmit_value_debug_string(sb, oss);
        oss << "=";
        transmit_value_debug_string(sb, oss);
        sorted.push_back(oss.str());
        oss.str("");
    }
    std::sort(sorted.begin(), sorted.end());
    for (const std::string &s : sorted) {
        oss << s << ";";
    }
    return oss.str();
}

void World::diff_lua_tables(lua_State *master, StreamBuffer *sb) {
    lua_State *synch = state();
    LuaVar sntmap, mntmap, stnmap, mtnmap;
    LuaStack SLS(synch, sntmap, stnmap);
    LuaStack MLS(master, mntmap, mtnmap);
    SLS.rawget(sntmap, LuaRegistry, "ntmap");
    MLS.rawget(mntmap, LuaRegistry, "ntmap");
    SLS.rawget(stnmap, LuaRegistry, "tnmap");
    MLS.rawget(mtnmap, LuaRegistry, "tnmap");
    int m_ntables = MLS.rawlen(mntmap);
    int s_ntables = SLS.rawlen(sntmap);
    assert(m_ntables == s_ntables);
    
    sb->write_int32(0);
    int write_count_after = sb->total_writes();
    int nmodified = 0;
    int s_top = lua_gettop(synch);
    int m_top = lua_gettop(master);
    for (int id = 1; id <= m_ntables; id++) {
        lua_pushvalue(master, mtnmap.index());
        lua_rawgeti(master, mtnmap.index(), id);
        if (lua_type(master, -1) == LUA_TTABLE) {
            lua_pushvalue(synch, stnmap.index());
            lua_rawgeti(synch, sntmap.index(), id);
            int tw = sb->total_writes();
            sb->write_int32(id);
            nmodified += 1;
            if (!compare_tables(synch, master, true, sb)) {
                sb->unwrite_to(tw);
                nmodified -= 1;
            }
            assert(lua_gettop(synch) == s_top);
            assert(lua_gettop(master) == m_top);
        } else {
            lua_pop(master, 2);
        }
    }
    sb->overwrite_int32(write_count_after, nmodified);
}


void World::diff_tangible_databases(const IdVector &basis, lua_State *master, StreamBuffer *sb) {
    lua_State *synch = state();
    LuaVar stnmap, mtnmap, stangibles, mtangibles;
    LuaStack SLS(synch, stnmap, stangibles);
    LuaStack MLS(master, mtnmap, mtangibles);
    SLS.rawget(stnmap, LuaRegistry, "tnmap");
    MLS.rawget(mtnmap, LuaRegistry, "tnmap");
    SLS.rawget(stangibles, LuaRegistry, "tangibles");
    MLS.rawget(mtangibles, LuaRegistry, "tangibles");
    
    sb->write_int32(0);
    int write_count_after = sb->total_writes();
    int nmodified = 0;
    int s_top = lua_gettop(synch);
    int m_top = lua_gettop(master);
    for (int64_t id : basis) {
        lua_pushvalue(master, mtnmap.index());
        lua_rawgeti(master, mtangibles.index(), id);
        lua_pushvalue(synch, stnmap.index());
        lua_rawgeti(synch, stangibles.index(), id);
        int tw = sb->total_writes();
        sb->write_int64(id);
        nmodified += 1;
        if (!compare_tables(synch, master, false, sb)) {
            sb->unwrite_to(tw);
            nmodified -= 1;
        }
        assert(lua_gettop(synch) == s_top);
        assert(lua_gettop(master) == m_top);
    }
    sb->overwrite_int32(write_count_after, nmodified);
}

LuaDefine(table_diffcompare, "c") {
    LuaArg mtnmap, mtab, stnmap, stab;
    LuaRet dbgstring;
    LuaVar tthread;
    LuaStack LS(L, mtnmap, mtab, stnmap, stab, dbgstring, tthread);
    // Create a temporary thread to be the 'synch model'.  We'll use the
    // existing thread as the 'master model'.
    lua_State *synch = lua_newthread(L);
    lua_replace(L, tthread.index());
    // Call tablecmp_diff.
    StreamBuffer sb;
    lua_pushvalue(L, stnmap.index());
    lua_pushvalue(L, stab.index());
    lua_xmove(L, synch, 2);
    lua_pushvalue(L, mtnmap.index());
    lua_pushvalue(L, mtab.index());
    compare_tables(synch, L, true, &sb);
    // Convert the output to a debug string.
    LS.set(dbgstring, compare_tables_debug_string(&sb));
    return LS.result();
}