/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#include "mongo/db/pipeline/variables.h"
#include "mongo/db/client.h"
#include "mongo/db/logical_clock.h"
#include "mongo/platform/basic.h"
#include "mongo/platform/random.h"
#include "mongo/util/str.h"
#include "mongo/util/time_support.h"

namespace mongo {

constexpr Variables::Id Variables::kRootId;
constexpr Variables::Id Variables::kRemoveId;

const StringMap<Variables::Id> Variables::kBuiltinVarNameToId = {
    {"ROOT", kRootId}, {"REMOVE", kRemoveId}, {"NOW", kNowId}, {"CLUSTER_TIME", kClusterTimeId}};

void Variables::uassertValidNameForUserWrite(StringData varName) {
    // System variables users allowed to write to (currently just one)
    if (varName == "CURRENT") {
        return;
    }

    uassert(16866, "empty variable names are not allowed", !varName.empty());

    const bool firstCharIsValid =
        (varName[0] >= 'a' && varName[0] <= 'z') || (varName[0] & '\x80')  // non-ascii
        ;

    uassert(16867,
            str::stream() << "'" << varName
                          << "' starts with an invalid character for a user variable name",
            firstCharIsValid);

    for (size_t i = 1; i < varName.size(); i++) {
        const bool charIsValid = (varName[i] >= 'a' && varName[i] <= 'z') ||
            (varName[i] >= 'A' && varName[i] <= 'Z') || (varName[i] >= '0' && varName[i] <= '9') ||
            (varName[i] == '_') || (varName[i] & '\x80')  // non-ascii
            ;

        uassert(16868,
                str::stream() << "'" << varName << "' contains an invalid character "
                              << "for a variable name: '"
                              << varName[i]
                              << "'",
                charIsValid);
    }
}

void Variables::uassertValidNameForUserRead(StringData varName) {
    uassert(16869, "empty variable names are not allowed", !varName.empty());

    const bool firstCharIsValid = (varName[0] >= 'a' && varName[0] <= 'z') ||
        (varName[0] >= 'A' && varName[0] <= 'Z') || (varName[0] & '\x80')  // non-ascii
        ;

    uassert(16870,
            str::stream() << "'" << varName
                          << "' starts with an invalid character for a variable name",
            firstCharIsValid);

    for (size_t i = 1; i < varName.size(); i++) {
        const bool charIsValid = (varName[i] >= 'a' && varName[i] <= 'z') ||
            (varName[i] >= 'A' && varName[i] <= 'Z') || (varName[i] >= '0' && varName[i] <= '9') ||
            (varName[i] == '_') || (varName[i] & '\x80')  // non-ascii
            ;

        uassert(16871,
                str::stream() << "'" << varName << "' contains an invalid character "
                              << "for a variable name: '"
                              << varName[i]
                              << "'",
                charIsValid);
    }
}

void Variables::setValue(Id id, const Value& value, bool isConstant) {
    uassert(17199, "can't use Variables::setValue to set a reserved builtin variable", id >= 0);

    const auto idAsSizeT = static_cast<size_t>(id);
    if (idAsSizeT >= _valueList.size()) {
        _valueList.resize(idAsSizeT + 1);
    } else {
        // If a value has already been set for 'id', and that value was marked as constant, then it
        // is illegal to modify.
        invariant(!_valueList[idAsSizeT].isConstant);
    }

    _valueList[idAsSizeT] = ValueAndState(value, isConstant);
}

void Variables::setValue(Variables::Id id, const Value& value) {
    const bool isConstant = false;
    setValue(id, value, isConstant);
}

void Variables::setConstantValue(Variables::Id id, const Value& value) {
    const bool isConstant = true;
    setValue(id, value, isConstant);
}

Value Variables::getUserDefinedValue(Variables::Id id) const {
    invariant(isUserDefinedVariable(id));

    uassert(40434,
            str::stream() << "Requesting Variables::getValue with an out of range id: " << id,
            static_cast<size_t>(id) < _valueList.size());
    return _valueList[id].value;
}

Value Variables::getValue(Id id, const Document& root) const {
    if (id < 0) {
        // This is a reserved id for a builtin variable.
        switch (id) {
            case Variables::kRootId:
                return Value(root);
            case Variables::kRemoveId:
                return Value();
            case Variables::kNowId:
            case Variables::kClusterTimeId:
                if (auto it = _runtimeConstants.find(id); it != _runtimeConstants.end()) {
                    return it->second;
                }

                uasserted(51144,
                          str::stream() << "Builtin variable '$$" << getBuiltinVariableName(id)
                                        << "' is not available");
                MONGO_UNREACHABLE;
            default:
                MONGO_UNREACHABLE;
        }
    }

    return getUserDefinedValue(id);
}

Document Variables::getDocument(Id id, const Document& root) const {
    if (id == Variables::kRootId) {
        // For the common case of ROOT, avoid round-tripping through Value.
        return root;
    }

    const Value var = getValue(id, root);
    if (var.getType() == Object)
        return var.getDocument();

    return Document();
}

RuntimeConstants Variables::getRuntimeConstants() const {
    RuntimeConstants constants;

    if (auto it = _runtimeConstants.find(kNowId); it != _runtimeConstants.end()) {
        constants.setLocalNow(it->second.getDate());
    }
    if (auto it = _runtimeConstants.find(kClusterTimeId); it != _runtimeConstants.end()) {
        constants.setClusterTime(it->second.getTimestamp());
    }

    return constants;
}

void Variables::setRuntimeConstants(const RuntimeConstants& constants) {
    _runtimeConstants[kNowId] = Value(constants.getLocalNow());
    // We use a null Timestamp to indicate that the clusterTime is not available; this can happen if
    // the logical clock is not running. We do not use boost::optional because this would allow the
    // IDL to serialize a RuntimConstants without clusterTime, which should always be an error.
    if (!constants.getClusterTime().isNull()) {
        _runtimeConstants[kClusterTimeId] = Value(constants.getClusterTime());
    }
}

void Variables::setDefaultRuntimeConstants(OperationContext* opCtx) {
    setRuntimeConstants(Variables::generateRuntimeConstants(opCtx));
}

RuntimeConstants Variables::generateRuntimeConstants(OperationContext* opCtx) {
    // On a standalone, the clock may not be running and $$CLUSTER_TIME is unavailable. If the
    // logical clock is available, set the clusterTime in the runtime constants. Otherwise, the
    // clusterTime is set to the null Timestamp.
    if (opCtx->getClient()) {
        if (auto logicalClock = LogicalClock::get(opCtx); logicalClock) {
            auto clusterTime = logicalClock->getClusterTime();
            if (clusterTime != LogicalTime::kUninitialized) {
                return {Date_t::now(), clusterTime.asTimestamp()};
            }
        }
    }
    return {Date_t::now(), Timestamp()};
}

Variables::Id VariablesParseState::defineVariable(StringData name) {
    // Caller should have validated before hand by using Variables::uassertValidNameForUserWrite.
    massert(17275,
            "Can't redefine a non-user-writable variable",
            Variables::kBuiltinVarNameToId.find(name) == Variables::kBuiltinVarNameToId.end());

    Variables::Id id = _idGenerator->generateId();
    invariant(id > _lastSeen);

    _variables[name] = _lastSeen = id;
    return id;
}

Variables::Id VariablesParseState::getVariable(StringData name) const {
    auto it = _variables.find(name);
    if (it != _variables.end()) {
        // Found a user-defined variable.
        return it->second;
    }

    it = Variables::kBuiltinVarNameToId.find(name);
    if (it != Variables::kBuiltinVarNameToId.end()) {
        // This is a builtin variable.
        return it->second;
    }

    // If we didn't find either a user-defined or builtin variable, then we reject everything other
    // than CURRENT. If this is CURRENT, then we treat it as equivalent to ROOT.
    uassert(17276, str::stream() << "Use of undefined variable: " << name, name == "CURRENT");
    return Variables::kRootId;
}

std::set<Variables::Id> VariablesParseState::getDefinedVariableIDs() const {
    std::set<Variables::Id> ids;

    for (auto&& keyId : _variables) {
        ids.insert(keyId.second);
    }

    return ids;
}
}