// This file is part of OpenCV project.
// It is subject to the license terms in the LICENSE file found in the top-level directory
// of this distribution and at http://opencv.org/license.html.
//
// Copyright (C) 2018 Intel Corporation


#include <vector>
#include <stack>
#include <unordered_map>

#include <ade/util/algorithm.hpp>      // any_of
#include <ade/util/zip_range.hpp>      // zip_range, indexed

#include <ade/graph.hpp>
#include <ade/passes/check_cycles.hpp>

#include "api/gcomputation_priv.hpp"
#include "api/gnode_priv.hpp"   // FIXME: why it is here?
#include "api/gproto_priv.hpp"  // FIXME: why it is here?
#include "api/gcall_priv.hpp"   // FIXME: why it is here?
#include "api/gapi_priv.hpp"    // FIXME: why it is here?
#include "api/gbackend_priv.hpp" // Backend basic API (newInstance, etc)

#include "compiler/gmodel.hpp"
#include "compiler/gmodelbuilder.hpp"
#include "compiler/gcompiler.hpp"
#include "compiler/gcompiled_priv.hpp"
#include "compiler/passes/passes.hpp"

#include "executor/gexecutor.hpp"
#include "backends/common/gbackend.hpp"

// <FIXME:>
#include "opencv2/gapi/cpu/core.hpp"    // Also directly refer to Core
#include "opencv2/gapi/cpu/imgproc.hpp" // ...and Imgproc kernel implementations
// </FIXME:>

#include "opencv2/gapi/gcompoundkernel.hpp" // compound::backend()

#include "opencv2/core/cvdef.h"
#include "logger.hpp"

namespace
{
    cv::gapi::GKernelPackage getKernelPackage(cv::GCompileArgs &args)
    {
        static auto ocv_pkg = combine(cv::gapi::core::cpu::kernels(),
                                      cv::gapi::imgproc::cpu::kernels(),
                                      cv::unite_policy::KEEP);
        auto user_pkg = cv::gimpl::getCompileArg<cv::gapi::GKernelPackage>(args);
        return combine(ocv_pkg, user_pkg.value_or(cv::gapi::GKernelPackage{}), cv::unite_policy::REPLACE);
    }

    cv::util::optional<std::string> getGraphDumpDirectory(cv::GCompileArgs& args)
    {
        auto dump_info = cv::gimpl::getCompileArg<cv::graph_dump_path>(args);
        if (!dump_info.has_value())
        {
            const char* path = std::getenv("GRAPH_DUMP_PATH");
            return path
                ? cv::util::make_optional(std::string(path))
                : cv::util::optional<std::string>();
        }
        else
        {
            return cv::util::make_optional(dump_info.value().m_dump_path);
        }
    }
} // anonymous namespace


// GCompiler implementation ////////////////////////////////////////////////////

cv::gimpl::GCompiler::GCompiler(const cv::GComputation &c,
                                GMetaArgs              &&metas,
                                GCompileArgs           &&args)
    : m_c(c), m_metas(std::move(metas)), m_args(std::move(args))
{
    using namespace std::placeholders;
    m_all_kernels       = getKernelPackage(m_args);
    auto lookup_order   = getCompileArg<gapi::GLookupOrder>(m_args).value_or(gapi::GLookupOrder());
    auto dump_path      = getGraphDumpDirectory(m_args);

    m_e.addPassStage("init");
    m_e.addPass("init", "check_cycles",  ade::passes::CheckCycles());
    m_e.addPass("init", "expand_kernels",  std::bind(passes::expandKernels, _1,
                                                     m_all_kernels)); // NB: package is copied
    m_e.addPass("init", "topo_sort",     ade::passes::TopologicalSort());
    m_e.addPass("init", "init_islands",  passes::initIslands);
    m_e.addPass("init", "check_islands", passes::checkIslands);
    // TODO:
    // - Check basic graph validity (i.e., all inputs are connected)
    // - Complex dependencies (i.e. parent-child) unrolling
    // - etc, etc, etc

    // Remove GCompoundBackend to avoid calling setupBackend() with it in the list
    m_all_kernels.remove(cv::gapi::compound::backend());
    m_e.addPass("init", "resolve_kernels", std::bind(passes::resolveKernels, _1,
                                                     std::ref(m_all_kernels), // NB: and not copied here
                                                     lookup_order));

    m_e.addPass("init", "check_islands_content", passes::checkIslandsContent);
    m_e.addPassStage("meta");
    m_e.addPass("meta", "initialize",   std::bind(passes::initMeta, _1, std::ref(m_metas)));
    m_e.addPass("meta", "propagate",    passes::inferMeta);
    m_e.addPass("meta", "finalize",     passes::storeResultingMeta);
    // moved to another stage, FIXME: two dumps?
    //    m_e.addPass("meta", "dump_dot",     passes::dumpDotStdout);

    // Special stage for backend-specific transformations
    // FIXME: document passes hierarchy and order for backend developers
    m_e.addPassStage("transform");

    m_e.addPassStage("exec");
    m_e.addPass("exec", "fuse_islands",     passes::fuseIslands);
    m_e.addPass("exec", "sync_islands",     passes::syncIslandTags);

    if (dump_path.has_value())
    {
        m_e.addPass("exec", "dump_dot", std::bind(passes::dumpGraph, _1,
                                                  dump_path.value()));
    }

    // Process backends at the last moment (after all G-API passes are added).
    ade::ExecutionEngineSetupContext ectx(m_e);
    auto backends = m_all_kernels.backends();
    for (auto &b : backends)
    {
        b.priv().addBackendPasses(ectx);
    }
}

void cv::gimpl::GCompiler::validateInputMeta()
{
    if (m_metas.size() != m_c.priv().m_ins.size())
    {
        util::throw_error(std::logic_error
                    ("COMPILE: GComputation interface / metadata mismatch! "
                     "(expected " + std::to_string(m_c.priv().m_ins.size()) + ", "
                     "got " + std::to_string(m_metas.size()) + " meta arguments)"));
    }

    const auto meta_matches = [](const GMetaArg &meta, const GProtoArg &proto) {
        switch (proto.index())
        {
        // FIXME: Auto-generate methods like this from traits:
        case GProtoArg::index_of<cv::GMat>():
            return util::holds_alternative<cv::GMatDesc>(meta);

        case GProtoArg::index_of<cv::GScalar>():
            return util::holds_alternative<cv::GScalarDesc>(meta);

        case GProtoArg::index_of<cv::detail::GArrayU>():
            return util::holds_alternative<cv::GArrayDesc>(meta);

        default:
            GAPI_Assert(false);
        }
        return false; // should never happen
    };

    for (const auto &meta_arg_idx : ade::util::indexed(ade::util::zip(m_metas, m_c.priv().m_ins)))
    {
        const auto &meta  = std::get<0>(ade::util::value(meta_arg_idx));
        const auto &proto = std::get<1>(ade::util::value(meta_arg_idx));

        if (!meta_matches(meta, proto))
        {
            const auto index  = ade::util::index(meta_arg_idx);
            util::throw_error(std::logic_error
                        ("GComputation object type / metadata descriptor mismatch "
                         "(argument " + std::to_string(index) + ")"));
            // FIXME: report what we've got and what we've expected
        }
    }
    // All checks are ok
}

void cv::gimpl::GCompiler::validateOutProtoArgs()
{
    for (const auto &out_pos : ade::util::indexed(m_c.priv().m_outs))
    {
        const auto &node = proto::origin_of(ade::util::value(out_pos)).node;
        if (node.shape() != cv::GNode::NodeShape::CALL)
        {
            auto pos = ade::util::index(out_pos);
            util::throw_error(std::logic_error
                        ("Computation output " + std::to_string(pos) +
                         " is not a result of any operation"));
        }
    }
}

cv::gimpl::GCompiler::GPtr cv::gimpl::GCompiler::generateGraph()
{
    validateInputMeta();
    validateOutProtoArgs();

    // Generate ADE graph from expression-based computation
    std::unique_ptr<ade::Graph> pG(new ade::Graph);
    ade::Graph& g = *pG;

    GModel::Graph gm(g);
    cv::gimpl::GModel::init(gm);
    cv::gimpl::GModelBuilder builder(g);
    auto proto_slots = builder.put(m_c.priv().m_ins, m_c.priv().m_outs);
    GAPI_LOG_INFO(NULL, "Generated graph: " << g.nodes().size() << " nodes" << std::endl);

    // Store Computation's protocol in metadata
    Protocol p;
    std::tie(p.inputs, p.outputs, p.in_nhs, p.out_nhs) = proto_slots;
    gm.metadata().set(p);

    return pG;
}

void cv::gimpl::GCompiler::runPasses(ade::Graph &g)
{
    m_e.runPasses(g);
    GAPI_LOG_INFO(NULL, "All compiler passes are successful");
}

void cv::gimpl::GCompiler::compileIslands(ade::Graph &g)
{
    GModel::Graph gm(g);
    std::shared_ptr<ade::Graph> gptr(gm.metadata().get<IslandModel>().model);
    GIslandModel::Graph gim(*gptr);

    // Run topological sort on GIslandModel first
    auto pass_ctx = ade::passes::PassContext{*gptr};
    ade::passes::TopologicalSort{}(pass_ctx);

    // Now compile islands
    GIslandModel::compileIslands(gim, g, m_args);
}

cv::GCompiled cv::gimpl::GCompiler::produceCompiled(GPtr &&pg)
{
    // This is the final compilation step. Here:
    // - An instance of GExecutor is created. Depening on the platform,
    //   build configuration, etc, a GExecutor may be:
    //   - a naive single-thread graph interpreter;
    //   - a std::thread-based thing
    //   - a TBB-based thing, etc.
    // - All this stuff is wrapped into a GCompiled object and returned
    //   to user.

    // Note: this happens in the last pass ("compile_islands"):
    // - Each GIsland of GIslandModel instantiates its own,
    //   backend-specific executable object
    //   - Every backend gets a subgraph to execute, and builds
    //     an execution plan for it (backend-specific execution)
    // ...before call to produceCompiled();

    const auto &outMetas = GModel::ConstGraph(*pg).metadata()
        .get<OutputMeta>().outMeta;
    std::unique_ptr<GExecutor> pE(new GExecutor(std::move(pg)));
    // FIXME: select which executor will be actually used,
    // make GExecutor abstract.

    GCompiled compiled;
    compiled.priv().setup(m_metas, outMetas, std::move(pE));
    return compiled;
}

cv::GCompiled cv::gimpl::GCompiler::compile()
{
    std::unique_ptr<ade::Graph> pG = generateGraph();
    runPasses(*pG);
    compileIslands(*pG);
    return produceCompiled(std::move(pG));
}