// -*- c++ -*-
// Distributed under the BSD 2-Clause License.
// See accompanying file LICENSE for details.
#include "deps.h"

#include "util.h"

#include <nlohmann/json.hpp>

#include <fstream>

namespace {
/* Format example:
build/src/libctor_a-libctor_cc.o: src/libctor.cc \
 src/getoptpp/getoptpp.hpp src/ctor.h src/configure.h src/rebuild.h \
 src/A\ B\ C.h src/task.h src/build.h src/unittest.h
 */
std::vector<std::string> readDepsMake(const std::string& dep_file)
{
	auto str = readFile(dep_file);

	std::vector<std::string> output;
	std::string tmp;

	enum class State
	{
		pre_colon,
		post_colon,
		in_escape,
	} state{State::pre_colon};

	auto old_state{state};
	for(const auto& c : str)
	{
		if(c == '\r')
		{
			// just always ignore windows extra newline char
			continue;
		}

		switch(state)
		{
		case State::pre_colon:
			if(c == ':') // ignore everything until the colon
			{
				state = State::post_colon;
				continue;
			}
			continue;

		case State::post_colon:
			if(c == '\n')
			{
				// done
				if(!tmp.empty())
				{
					output.emplace_back(tmp);
				}
				return output;
			}
			if(c == '\\')
			{
				old_state = state;
				state = State::in_escape;
				continue;
			}
			if(c == '\t' || c == ' ') // new token
			{
				if(!tmp.empty())
				{
					output.emplace_back(tmp);
				}
				tmp.clear();
				continue;
			}
			break;

		case State::in_escape:
			if(c == '\n')
			{
				// linewrap
				state = old_state;
				continue;
			}
			state = old_state;
			break;
		}

		tmp += c;
	}

	if(!tmp.empty())
	{
		output.emplace_back(tmp);
	}

	return output;
}

// https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p1689r5.html
// https://devblogs.microsoft.com/cppblog/introducing-source-dependency-reporting-with-msvc-in-visual-studio-2019-version-16-7/
/* Format examples:
{
    "Version": "1.1",
    "Data": {
        "Source": "z:\\home\\deva\\docs\\c\\ctor\\src\\libctor.cc",
        "ProvidedModule": "",
        "Includes": [
            "c:\\program files (x86)\\microsoft visual studio\\2019\\buildtools\\vc\\tools\\msvc\\14.29.30133\\include\\vector",
            "c:\\program files (x86)\\microsoft visual studio\\2019\\buildtools\\vc\\tools\\msvc\\14.29.30133\\include\\yvals_core.h",
            "c:\\program files (x86)\\microsoft visual studio\\2019\\buildtools\\vc\\tools\\msvc\\14.29.30133\\include\\vcruntime.h",
.
.
.
            "z:\\home\\deva\\docs\\c\\ctor\\src\\unittest.h"
        ],
        "ImportedModules": [],
        "ImportedHeaderUnits": []
    }
}
*/
/*
{
    "Version": "1.2",
    "Data": {
        "Source": "c:\\jenkins\\workspace\\ctor-linux64\\src\\build.cc",
        "ProvidedModule": "",
        "Includes": [
            "c:\\jenkins\\workspace\\ctor-linux64\\src\\build.h",
            "c:\\program files (x86)\\microsoft visual studio\\2022\\buildtools\\vc\\tools\\msvc\\14.42.34433\\include\\string",
            "c:\\program files (x86)\\microsoft visual studio\\2022\\buildtools\\vc\\tools\\msvc\\14.42.34433\\include\\yvals_core.h",
.
.
.
            "c:\\program files (x86)\\microsoft visual studio\\2022\\buildtools\\vc\\tools\\msvc\\14.42.34433\\include\\iostream"
        ],
        "ImportedModules": [],
        "ImportedHeaderUnits": []
    }
}
*/

std::vector<std::string> readDepsJson(const std::string& dep_file)
{
	std::ifstream stream(dep_file);
	auto json = nlohmann::json::parse(stream);
	for(const auto& [key, value] : json.items())
	{
		if(key == "Data" && value.is_object())
		{
			for(const auto& [inner_key, inner_value] : value.items())
			{
				if(inner_key == "Includes" && inner_value.is_array())
				{
					std::vector<std::string> deps;
					for(const auto& dep : inner_value)
					{
						deps.emplace_back(dep);
					}
					return deps;
				}
			}
		}
	}
	return {};
}
}

std::vector<std::string> readDeps(const std::string& dep_file,
                                  ctor::toolchain toolchain)
{
	if(!std::filesystem::exists(dep_file))
	{
		return {};
	}

	switch(toolchain)
	{
	case ctor::toolchain::any:
	case ctor::toolchain::none:
		return {};

	// json based:
	case ctor::toolchain::msvc:
		return readDepsJson(dep_file);

	// makefile .d file based:
	case ctor::toolchain::gcc:
	case ctor::toolchain::clang:
		return readDepsMake(dep_file);
	}

	return {};
}