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/*
    This file is part of solidity.

    solidity is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    solidity 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
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with solidity.  If not, see <http://www.gnu.org/licenses/>.
*/
/**
 * @file KnownState.h
 * @author Christian <c@ethdev.com>
 * @date 2015
 * Contains knowledge about the state of the virtual machine at a specific instruction.
 */

#pragma once

#include <vector>
#include <map>
#include <set>
#include <tuple>
#include <memory>
#include <ostream>
#pragma warning(push)
#pragma GCC diagnostic push
#pragma clang diagnostic ignored "-Wredeclared-class-member"
#include <boost/bimap.hpp>
#pragma warning(pop)
#pragma GCC diagnostic pop
#include <libdevcore/CommonIO.h>
#include <libdevcore/Exceptions.h>
#include <libevmasm/ExpressionClasses.h>
#include <libevmasm/SemanticInformation.h>

namespace dev
{
namespace eth
{

class AssemblyItem;
using AssemblyItems = std::vector<AssemblyItem>;

/**
 * Class to infer and store knowledge about the state of the virtual machine at a specific
 * instruction.
 *
 * The general workings are that for each assembly item that is fed, an equivalence class is
 * derived from the operation and the equivalence class of its arguments. DUPi, SWAPi and some
 * arithmetic instructions are used to infer equivalences while these classes are determined.
 */
class KnownState
{
public:
    using Id = ExpressionClasses::Id;
    struct StoreOperation
    {
        enum Target { Invalid, Memory, Storage };
        StoreOperation(): target(Invalid), sequenceNumber(-1) {}
        StoreOperation(
            Target _target,
            Id _slot,
            unsigned _sequenceNumber,
            Id _expression
        ): target(_target), slot(_slot), sequenceNumber(_sequenceNumber), expression(_expression) {}
        bool isValid() const { return target != Invalid; }
        Target target;
        Id slot;
        unsigned sequenceNumber;
        Id expression;
    };

    explicit KnownState(
        std::shared_ptr<ExpressionClasses> _expressionClasses = std::make_shared<ExpressionClasses>()
    ): m_expressionClasses(_expressionClasses)
    {
    }

    /// Streams debugging information to @a _out.
    std::ostream& stream(std::ostream& _out) const;

    /// Feeds the item into the system for analysis.
    /// @returns a possible store operation
    StoreOperation feedItem(AssemblyItem const& _item, bool _copyItem = false);

    /// Resets any knowledge about storage.
    void resetStorage() { m_storageContent.clear(); }
    /// Resets any knowledge about storage.
    void resetMemory() { m_memoryContent.clear(); }
    /// Resets any knowledge about the current stack.
    void resetStack() { m_stackElements.clear(); m_stackHeight = 0; }
    /// Resets any knowledge.
    void reset() { resetStorage(); resetMemory(); resetStack(); }

    unsigned sequenceNumber() const { return m_sequenceNumber; }

    /// Replaces the state by the intersection with _other, i.e. only equal knowledge is retained.
    /// If the stack heighht is different, the smaller one is used and the stack is compared
    /// relatively.
    /// @param _combineSequenceNumbers if true, sets the sequence number to the maximum of both
    void reduceToCommonKnowledge(KnownState const& _other, bool _combineSequenceNumbers);

    /// @returns a shared pointer to a copy of this state.
    std::shared_ptr<KnownState> copy() const { return std::make_shared<KnownState>(*this); }

    /// @returns true if the knowledge about the state of both objects is (known to be) equal.
    bool operator==(KnownState const& _other) const;

    /// Retrieves the current equivalence class fo the given stack element (or generates a new
    /// one if it does not exist yet).
    Id stackElement(int _stackHeight, SourceLocation const& _location);
    /// @returns the stackElement relative to the current stack height.
    Id relativeStackElement(int _stackOffset, SourceLocation const& _location = SourceLocation());

    /// @returns its set of tags if the given expression class is a known tag union; returns a set
    /// containing the tag if it is a PushTag expression and the empty set otherwise.
    std::set<u256> tagsInExpression(Id _expressionId);
    /// During analysis, different tags on the stack are partially treated as the same class.
    /// This removes such classes not to confuse later analyzers.
    void clearTagUnions();

    int stackHeight() const { return m_stackHeight; }
    std::map<int, Id> const& stackElements() const { return m_stackElements; }
    ExpressionClasses& expressionClasses() const { return *m_expressionClasses; }

    std::map<Id, Id> const& storageContent() const { return m_storageContent; }

private:
    /// Assigns a new equivalence class to the next sequence number of the given stack element.
    void setStackElement(int _stackHeight, Id _class);
    /// Swaps the given stack elements in their next sequence number.
    void swapStackElements(int _stackHeightA, int _stackHeightB, SourceLocation const& _location);

    /// Increments the sequence number, deletes all storage information that might be overwritten
    /// and stores the new value at the given slot.
    /// @returns the store operation, which might be invalid if storage was not modified
    StoreOperation storeInStorage(Id _slot, Id _value, SourceLocation const& _location);
    /// Retrieves the current value at the given slot in storage or creates a new special sload class.
    Id loadFromStorage(Id _slot, SourceLocation const& _location);
    /// Increments the sequence number, deletes all memory information that might be overwritten
    /// and stores the new value at the given slot.
    /// @returns the store operation, which might be invalid if memory was not modified
    StoreOperation storeInMemory(Id _slot, Id _value, SourceLocation const& _location);
    /// Retrieves the current value at the given slot in memory or creates a new special mload class.
    Id loadFromMemory(Id _slot, SourceLocation const& _location);
    /// Finds or creates a new expression that applies the Keccak-256 hash function to the contents in memory.
    Id applyKeccak256(Id _start, Id _length, SourceLocation const& _location);

    /// @returns a new or already used Id representing the given set of tags.
    Id tagUnion(std::set<u256> _tags);

    /// Current stack height, can be negative.
    int m_stackHeight = 0;
    /// Current stack layout, mapping stack height -> equivalence class
    std::map<int, Id> m_stackElements;
    /// Current sequence number, this is incremented with each modification to storage or memory.
    unsigned m_sequenceNumber = 1;
    /// Knowledge about storage content.
    std::map<Id, Id> m_storageContent;
    /// Knowledge about memory content. Keys are memory addresses, note that the values overlap
    /// and are not contained here if they are not completely known.
    std::map<Id, Id> m_memoryContent;
    /// Keeps record of all Keccak-256 hashes that are computed.
    std::map<std::vector<Id>, Id> m_knownKeccak256Hashes;
    /// Structure containing the classes of equivalent expressions.
    std::shared_ptr<ExpressionClasses> m_expressionClasses;
    /// Container for unions of tags stored on the stack.
    boost::bimap<Id, std::set<u256>> m_tagUnions;
};

}
}