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// Google Mock - a framework for writing C++ mock classes.
//
// This file implements Matcher<const string&>, Matcher<string>, and
// utilities for defining matchers.

#include "gmock/gmock-matchers.h"

#include <string.h>
#include <iostream>
#include <sstream>
#include <string>

namespace testing {
namespace internal {

// Returns the description for a matcher defined using the MATCHER*()
// macro where the user-supplied description string is "", if
// 'negation' is false; otherwise returns the description of the
// negation of the matcher.  'param_values' contains a list of strings
// that are the print-out of the matcher's parameters.
GTEST_API_ std::string FormatMatcherDescription(bool negation,
                                                const char *matcher_name,
                                                const Strings &param_values)
{
    std::string result = ConvertIdentifierNameToWords(matcher_name);
    if (param_values.size() >= 1)
        result += " " + JoinAsTuple(param_values);
    return negation ? "not (" + result + ")" : result;
}

// FindMaxBipartiteMatching and its helper class.
//
// Uses the well-known Ford-Fulkerson max flow method to find a maximum
// bipartite matching. Flow is considered to be from left to right.
// There is an implicit source node that is connected to all of the left
// nodes, and an implicit sink node that is connected to all of the
// right nodes. All edges have unit capacity.
//
// Neither the flow graph nor the residual flow graph are represented
// explicitly. Instead, they are implied by the information in 'graph' and
// a vector<int> called 'left_' whose elements are initialized to the
// value kUnused. This represents the initial state of the algorithm,
// where the flow graph is empty, and the residual flow graph has the
// following edges:
//   - An edge from source to each left_ node
//   - An edge from each right_ node to sink
//   - An edge from each left_ node to each right_ node, if the
//     corresponding edge exists in 'graph'.
//
// When the TryAugment() method adds a flow, it sets left_[l] = r for some
// nodes l and r. This induces the following changes:
//   - The edges (source, l), (l, r), and (r, sink) are added to the
//     flow graph.
//   - The same three edges are removed from the residual flow graph.
//   - The reverse edges (l, source), (r, l), and (sink, r) are added
//     to the residual flow graph, which is a directional graph
//     representing unused flow capacity.
//
// When the method augments a flow (moving left_[l] from some r1 to some
// other r2), this can be thought of as "undoing" the above steps with
// respect to r1 and "redoing" them with respect to r2.
//
// It bears repeating that the flow graph and residual flow graph are
// never represented explicitly, but can be derived by looking at the
// information in 'graph' and in left_.
//
// As an optimization, there is a second vector<int> called right_ which
// does not provide any new information. Instead, it enables more
// efficient queries about edges entering or leaving the right-side nodes
// of the flow or residual flow graphs. The following invariants are
// maintained:
//
// left[l] == kUnused or right[left[l]] == l
// right[r] == kUnused or left[right[r]] == r
//
// . [ source ]                                        .
// .   |||                                             .
// .   |||                                             .
// .   ||\--> left[0]=1  ---\    right[0]=-1 ----\     .
// .   ||                   |                    |     .
// .   |\---> left[1]=-1    \--> right[1]=0  ---\|     .
// .   |                                        ||     .
// .   \----> left[2]=2  ------> right[2]=2  --\||     .
// .                                           |||     .
// .         elements           matchers       vvv     .
// .                                         [ sink ]  .
//
// See Also:
//   [1] Cormen, et al (2001). "Section 26.2: The Ford-Fulkerson method".
//       "Introduction to Algorithms (Second ed.)", pp. 651-664.
//   [2] "Ford-Fulkerson algorithm", Wikipedia,
//       'http://en.wikipedia.org/wiki/Ford%E2%80%93Fulkerson_algorithm'
class MaxBipartiteMatchState
{
public:
    explicit MaxBipartiteMatchState(const MatchMatrix &graph)
        : graph_(&graph)
        , left_(graph_->LhsSize(), kUnused)
        , right_(graph_->RhsSize(), kUnused)
    {
    }

    // Returns the edges of a maximal match, each in the form {left, right}.
    ElementMatcherPairs Compute()
    {
        // 'seen' is used for path finding { 0: unseen, 1: seen }.
        ::std::vector<char> seen;
        // Searches the residual flow graph for a path from each left node to
        // the sink in the residual flow graph, and if one is found, add flow
        // to the graph. It's okay to search through the left nodes once. The
        // edge from the implicit source node to each previously-visited left
        // node will have flow if that left node has any path to the sink
        // whatsoever. Subsequent augmentations can only add flow to the
        // network, and cannot take away that previous flow unit from the source.
        // Since the source-to-left edge can only carry one flow unit (or,
        // each element can be matched to only one matcher), there is no need
        // to visit the left nodes more than once looking for augmented paths.
        // The flow is known to be possible or impossible by looking at the
        // node once.
        for (size_t ilhs = 0; ilhs < graph_->LhsSize(); ++ilhs) {
            // Reset the path-marking vector and try to find a path from
            // source to sink starting at the left_[ilhs] node.
            GTEST_CHECK_(left_[ilhs] == kUnused)
                << "ilhs: " << ilhs << ", left_[ilhs]: " << left_[ilhs];
            // 'seen' initialized to 'graph_->RhsSize()' copies of 0.
            seen.assign(graph_->RhsSize(), 0);
            TryAugment(ilhs, &seen);
        }
        ElementMatcherPairs result;
        for (size_t ilhs = 0; ilhs < left_.size(); ++ilhs) {
            size_t irhs = left_[ilhs];
            if (irhs == kUnused)
                continue;
            result.push_back(ElementMatcherPair(ilhs, irhs));
        }
        return result;
    }

private:
    static const size_t kUnused = static_cast<size_t>(-1);

    // Perform a depth-first search from left node ilhs to the sink.  If a
    // path is found, flow is added to the network by linking the left and
    // right vector elements corresponding each segment of the path.
    // Returns true if a path to sink was found, which means that a unit of
    // flow was added to the network. The 'seen' vector elements correspond
    // to right nodes and are marked to eliminate cycles from the search.
    //
    // Left nodes will only be explored at most once because they
    // are accessible from at most one right node in the residual flow
    // graph.
    //
    // Note that left_[ilhs] is the only element of left_ that TryAugment will
    // potentially transition from kUnused to another value. Any other
    // left_ element holding kUnused before TryAugment will be holding it
    // when TryAugment returns.
    //
    bool TryAugment(size_t ilhs, ::std::vector<char> *seen)
    {
        for (size_t irhs = 0; irhs < graph_->RhsSize(); ++irhs) {
            if ((*seen)[irhs])
                continue;
            if (!graph_->HasEdge(ilhs, irhs))
                continue;
            // There's an available edge from ilhs to irhs.
            (*seen)[irhs] = 1;
            // Next a search is performed to determine whether
            // this edge is a dead end or leads to the sink.
            //
            // right_[irhs] == kUnused means that there is residual flow from
            // right node irhs to the sink, so we can use that to finish this
            // flow path and return success.
            //
            // Otherwise there is residual flow to some ilhs. We push flow
            // along that path and call ourselves recursively to see if this
            // ultimately leads to sink.
            if (right_[irhs] == kUnused || TryAugment(right_[irhs], seen)) {
                // Add flow from left_[ilhs] to right_[irhs].
                left_[ilhs] = irhs;
                right_[irhs] = ilhs;
                return true;
            }
        }
        return false;
    }

    const MatchMatrix *graph_; // not owned
    // Each element of the left_ vector represents a left hand side node
    // (i.e. an element) and each element of right_ is a right hand side
    // node (i.e. a matcher). The values in the left_ vector indicate
    // outflow from that node to a node on the right_ side. The values
    // in the right_ indicate inflow, and specify which left_ node is
    // feeding that right_ node, if any. For example, left_[3] == 1 means
    // there's a flow from element #3 to matcher #1. Such a flow would also
    // be redundantly represented in the right_ vector as right_[1] == 3.
    // Elements of left_ and right_ are either kUnused or mutually
    // referent. Mutually referent means that left_[right_[i]] = i and
    // right_[left_[i]] = i.
    ::std::vector<size_t> left_;
    ::std::vector<size_t> right_;
};

const size_t MaxBipartiteMatchState::kUnused;

GTEST_API_ ElementMatcherPairs FindMaxBipartiteMatching(const MatchMatrix &g)
{
    return MaxBipartiteMatchState(g).Compute();
}

static void LogElementMatcherPairVec(const ElementMatcherPairs &pairs,
                                     ::std::ostream *stream)
{
    typedef ElementMatcherPairs::const_iterator Iter;
    ::std::ostream &os = *stream;
    os << "{";
    const char *sep = "";
    for (Iter it = pairs.begin(); it != pairs.end(); ++it) {
        os << sep << "\n  ("
           << "element #" << it->first << ", "
           << "matcher #" << it->second << ")";
        sep = ",";
    }
    os << "\n}";
}

bool MatchMatrix::NextGraph()
{
    for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
        for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
            char &b = matched_[SpaceIndex(ilhs, irhs)];
            if (!b) {
                b = 1;
                return true;
            }
            b = 0;
        }
    }
    return false;
}

void MatchMatrix::Randomize()
{
    for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
        for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
            char &b = matched_[SpaceIndex(ilhs, irhs)];
            b = static_cast<char>(rand() & 1); // NOLINT
        }
    }
}

std::string MatchMatrix::DebugString() const
{
    ::std::stringstream ss;
    const char *sep = "";
    for (size_t i = 0; i < LhsSize(); ++i) {
        ss << sep;
        for (size_t j = 0; j < RhsSize(); ++j) {
            ss << HasEdge(i, j);
        }
        sep = ";";
    }
    return ss.str();
}

void UnorderedElementsAreMatcherImplBase::DescribeToImpl(
    ::std::ostream *os) const
{
    switch (match_flags()) {
    case UnorderedMatcherRequire::ExactMatch:
        if (matcher_describers_.empty()) {
            *os << "is empty";
            return;
        }
        if (matcher_describers_.size() == 1) {
            *os << "has " << Elements(1) << " and that element ";
            matcher_describers_[0]->DescribeTo(os);
            return;
        }
        *os << "has " << Elements(matcher_describers_.size())
            << " and there exists some permutation of elements such that:\n";
        break;
    case UnorderedMatcherRequire::Superset:
        *os << "a surjection from elements to requirements exists such that:\n";
        break;
    case UnorderedMatcherRequire::Subset:
        *os << "an injection from elements to requirements exists such that:\n";
        break;
    }

    const char *sep = "";
    for (size_t i = 0; i != matcher_describers_.size(); ++i) {
        *os << sep;
        if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
            *os << " - element #" << i << " ";
        } else {
            *os << " - an element ";
        }
        matcher_describers_[i]->DescribeTo(os);
        if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
            sep = ", and\n";
        } else {
            sep = "\n";
        }
    }
}

void UnorderedElementsAreMatcherImplBase::DescribeNegationToImpl(
    ::std::ostream *os) const
{
    switch (match_flags()) {
    case UnorderedMatcherRequire::ExactMatch:
        if (matcher_describers_.empty()) {
            *os << "isn't empty";
            return;
        }
        if (matcher_describers_.size() == 1) {
            *os << "doesn't have " << Elements(1) << ", or has " << Elements(1)
                << " that ";
            matcher_describers_[0]->DescribeNegationTo(os);
            return;
        }
        *os << "doesn't have " << Elements(matcher_describers_.size())
            << ", or there exists no permutation of elements such that:\n";
        break;
    case UnorderedMatcherRequire::Superset:
        *os << "no surjection from elements to requirements exists such that:\n";
        break;
    case UnorderedMatcherRequire::Subset:
        *os << "no injection from elements to requirements exists such that:\n";
        break;
    }
    const char *sep = "";
    for (size_t i = 0; i != matcher_describers_.size(); ++i) {
        *os << sep;
        if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
            *os << " - element #" << i << " ";
        } else {
            *os << " - an element ";
        }
        matcher_describers_[i]->DescribeTo(os);
        if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
            sep = ", and\n";
        } else {
            sep = "\n";
        }
    }
}

// Checks that all matchers match at least one element, and that all
// elements match at least one matcher. This enables faster matching
// and better error reporting.
// Returns false, writing an explanation to 'listener', if and only
// if the success criteria are not met.
bool UnorderedElementsAreMatcherImplBase::VerifyMatchMatrix(
    const ::std::vector<std::string> &element_printouts,
    const MatchMatrix &matrix, MatchResultListener *listener) const
{
    bool result = true;
    ::std::vector<char> element_matched(matrix.LhsSize(), 0);
    ::std::vector<char> matcher_matched(matrix.RhsSize(), 0);

    for (size_t ilhs = 0; ilhs < matrix.LhsSize(); ilhs++) {
        for (size_t irhs = 0; irhs < matrix.RhsSize(); irhs++) {
            char matched = matrix.HasEdge(ilhs, irhs);
            element_matched[ilhs] |= matched;
            matcher_matched[irhs] |= matched;
        }
    }

    if (match_flags() & UnorderedMatcherRequire::Superset) {
        const char *sep =
            "where the following matchers don't match any elements:\n";
        for (size_t mi = 0; mi < matcher_matched.size(); ++mi) {
            if (matcher_matched[mi])
                continue;
            result = false;
            if (listener->IsInterested()) {
                *listener << sep << "matcher #" << mi << ": ";
                matcher_describers_[mi]->DescribeTo(listener->stream());
                sep = ",\n";
            }
        }
    }

    if (match_flags() & UnorderedMatcherRequire::Subset) {
        const char *sep =
            "where the following elements don't match any matchers:\n";
        const char *outer_sep = "";
        if (!result) {
            outer_sep = "\nand ";
        }
        for (size_t ei = 0; ei < element_matched.size(); ++ei) {
            if (element_matched[ei])
                continue;
            result = false;
            if (listener->IsInterested()) {
                *listener << outer_sep << sep << "element #" << ei << ": "
                          << element_printouts[ei];
                sep = ",\n";
                outer_sep = "";
            }
        }
    }
    return result;
}

bool UnorderedElementsAreMatcherImplBase::FindPairing(
    const MatchMatrix &matrix, MatchResultListener *listener) const
{
    ElementMatcherPairs matches = FindMaxBipartiteMatching(matrix);

    size_t max_flow = matches.size();
    if ((match_flags() & UnorderedMatcherRequire::Superset) && max_flow < matrix.RhsSize()) {
        if (listener->IsInterested()) {
            *listener << "where no permutation of the elements can satisfy all "
                         "matchers, and the closest match is "
                      << max_flow << " of " << matrix.RhsSize()
                      << " matchers with the pairings:\n";
            LogElementMatcherPairVec(matches, listener->stream());
        }
        return false;
    }
    if ((match_flags() & UnorderedMatcherRequire::Subset) && max_flow < matrix.LhsSize()) {
        if (listener->IsInterested()) {
            *listener
                << "where not all elements can be matched, and the closest match is "
                << max_flow << " of " << matrix.RhsSize()
                << " matchers with the pairings:\n";
            LogElementMatcherPairVec(matches, listener->stream());
        }
        return false;
    }

    if (matches.size() > 1) {
        if (listener->IsInterested()) {
            const char *sep = "where:\n";
            for (size_t mi = 0; mi < matches.size(); ++mi) {
                *listener << sep << " - element #" << matches[mi].first
                          << " is matched by matcher #" << matches[mi].second;
                sep = ",\n";
            }
        }
    }
    return true;
}

} // namespace internal
} // namespace testing
