#include "core/anime_db.h"
#include "core/anime.h"
#include "core/strings.h"
#include "core/json.h"
#include "core/filesystem.h"

#include "gui/translate/anime.h"
#include "gui/translate/anilist.h"

#include <QDate>

#include <fstream>

#include <iostream>
#include <exception>

namespace Anime {

size_t Database::GetTotalAnimeAmount() {
	size_t total = 0;

	for (const auto& [id, anime] : items)
		if (anime.IsInUserList())
			total++;

	return total;
}

size_t Database::GetListsAnimeAmount(ListStatus status) {
	if (status == ListStatus::NOT_IN_LIST)
		return 0;

	size_t total = 0;

	for (const auto& [id, anime] : items)
		if (anime.IsInUserList() && anime.GetUserStatus() == status)
			total++;

	return total;
}

size_t Database::GetTotalEpisodeAmount() {
	size_t total = 0;

	for (const auto& [id, anime] : items)
		if (anime.IsInUserList())
			total += anime.GetUserRewatchedTimes() * anime.GetEpisodes() + anime.GetUserProgress();

	return total;
}

/* Returns the total watched amount in minutes. */
size_t Database::GetTotalWatchedAmount() {
	size_t total = 0;

	for (const auto& [id, anime] : items)
		if (anime.IsInUserList())
			total += anime.GetDuration() * anime.GetUserProgress()
			         + anime.GetEpisodes() * anime.GetDuration() * anime.GetUserRewatchedTimes();

	return total;
}

/* Returns the total planned amount in minutes.
   Note that we should probably limit progress to the
   amount of episodes, as AniList will let you
   set episode counts up to 32768. But that should
   rather be handled elsewhere. */
size_t Database::GetTotalPlannedAmount() {
	size_t total = 0;

	for (const auto& [id, anime] : items)
		if (anime.IsInUserList())
			total += anime.GetDuration() * (anime.GetEpisodes() - anime.GetUserProgress());

	return total;
}

/* In Taiga this is called the mean, but "average" is
   what's primarily used in conversation, at least
   in the U.S. */
double Database::GetAverageScore() {
	double avg = 0;
	size_t amt = 0;

	for (const auto& [id, anime] : items) {
		if (anime.IsInUserList() && anime.GetUserScore()) {
			avg += anime.GetUserScore();
			amt++;
		}
	}
	return avg / amt;
}

double Database::GetScoreDeviation() {
	double squares_sum = 0, avg = GetAverageScore();
	size_t amt = 0;

	for (const auto& [id, anime] : items) {
		if (anime.IsInUserList() && anime.GetUserScore()) {
			squares_sum += std::pow(static_cast<double>(anime.GetUserScore()) - avg, 2);
			amt++;
		}
	}

	return (amt > 0) ? std::sqrt(squares_sum / amt) : 0;
}

template<typename T, typename U>
static T get_lowest_in_map(const std::unordered_map<T, U>& map) {
	if (map.size() <= 0)
		return 0;

	T id = 0;
	U ret = std::numeric_limits<U>::max();
	for (const auto& t : map) {
		if (t.second < ret) {
			ret = t.second;
			id = t.first;
		}
	}
	return id;
}

/* 
 * This fairly basic algorithm is only in effect because
 * there are some special cases, e.g. Another and Re:ZERO, where 
 * we get the wrong match, so we have to create Advanced Techniques
 * to solve this
 *
 * This algorithm:
 *   1. searches each anime item for a match to the preferred title
 *      AND all synonyms and marks those matches with
 *        `synonym.length() - (synonym.find(needle) + needle.length());`
 *      which should never be less than zero and will be zero if, and only if
 *      the titles match exactly.
 *   2. returns the id of the match that is the lowest, which will most
 *      definitely match anything that exactly matches the title of the
 *      filename
*/
int Database::GetAnimeFromTitle(const std::string& title) {
	if (title.empty())
		return 0;

	std::unordered_map<int, size_t> map;

	static const auto process_title = [&map](const Anime& anime, const std::string& title, const std::string& needle) -> bool {
		const std::string title_l = Strings::ToLower(title), needle_l = Strings::ToLower(needle);
		size_t ret = title_l.find(needle_l);
		if (ret == std::string::npos)
			return false;

		map[anime.GetId()] = title.length() - (ret + needle.length());
		return true;
	};

	for (const auto& [id, anime] : items) {
		if (process_title(anime, anime.GetUserPreferredTitle(), title))
			continue;

		for (const auto& synonym : anime.GetTitleSynonyms())
			if (process_title(anime, synonym, title))
				continue;
	}

	return get_lowest_in_map(map);
}

static bool GetListDataAsJSON(const Anime& anime, nlohmann::json& json) {
	if (!anime.IsInUserList())
		return false;

	// clang-format off
	json = {
		{"status", Translate::ToString(anime.GetUserStatus())},
		{"progress", anime.GetUserProgress()},
		{"score", anime.GetUserScore()},
		{"started", anime.GetUserDateStarted().GetAsAniListJson()},
		{"completed", anime.GetUserDateCompleted().GetAsAniListJson()},
		{"private", anime.GetUserIsPrivate()},
		{"rewatched_times", anime.GetUserRewatchedTimes()},
		{"rewatching", anime.GetUserIsRewatching()},
		{"updated", anime.GetUserTimeUpdated()},
		{"notes", anime.GetUserNotes()}
	};
	// clang-format on

	return true;
}

static bool GetAnimeAsJSON(const Anime& anime, nlohmann::json& json) {
	// clang-format off
	json = {
		{"id", anime.GetId()},
		{"title", {
			{"native", anime.GetNativeTitle()},
			{"romaji", anime.GetRomajiTitle()},
			{"english", anime.GetEnglishTitle()}
		}},
		{"synonyms", anime.GetTitleSynonyms()},
		{"episodes", anime.GetEpisodes()},
		{"airing_status", Translate::ToString(anime.GetAiringStatus())},
		{"air_date", anime.GetAirDate().GetAsAniListJson()},
		{"genres", anime.GetGenres()},
		{"producers", anime.GetProducers()},
		{"format", Translate::ToString(anime.GetFormat())},
		{"season", Translate::ToString(anime.GetSeason())},
		{"audience_score", anime.GetAudienceScore()},
		{"synopsis", anime.GetSynopsis()},
		{"duration", anime.GetDuration()},
		{"poster_url", anime.GetPosterUrl()}
	};
	// clang-format on

	nlohmann::json user;
	if (GetListDataAsJSON(anime, user))
		json.push_back({"list_data", user});

	return true;
}

bool Database::GetDatabaseAsJSON(nlohmann::json& json) {
	for (const auto& [id, anime] : items) {
		nlohmann::json anime_json = {};
		GetAnimeAsJSON(anime, anime_json);
		json.push_back(anime_json);
	}

	return true;
}

bool Database::SaveDatabaseToDisk() {
	std::filesystem::path db_path = Filesystem::GetAnimeDBPath();
	Filesystem::CreateDirectories(db_path);

	std::ofstream db_file(db_path);
	if (!db_file)
		return false;

	nlohmann::json json = {};
	if (!GetDatabaseAsJSON(json))
		return false;

	db_file << std::setw(4) << json << std::endl;
	return true;
}

static bool ParseAnimeUserInfoJSON(const nlohmann::json& json, Anime& anime) {
	if (!anime.IsInUserList())
		anime.AddToUserList();

	anime.SetUserStatus(Translate::ToListStatus(JSON::GetString<std::string>(json, "/status"_json_pointer, "")));
	anime.SetUserProgress(JSON::GetNumber(json, "/progress"_json_pointer, 0));
	anime.SetUserScore(JSON::GetNumber(json, "/score"_json_pointer, 0));
	anime.SetUserDateStarted(Date(JSON::GetValue(json, "/started"_json_pointer)));
	anime.SetUserDateCompleted(Date(JSON::GetValue(json, "/completed"_json_pointer)));
	anime.SetUserIsPrivate(JSON::GetBoolean(json, "/private"_json_pointer, false));
	anime.SetUserRewatchedTimes(JSON::GetNumber(json, "/rewatched_times"_json_pointer, 0));
	anime.SetUserIsRewatching(JSON::GetBoolean(json, "/rewatching"_json_pointer, false));
	anime.SetUserTimeUpdated(JSON::GetNumber(json, "/updated"_json_pointer, 0));
	anime.SetUserNotes(JSON::GetString<std::string>(json, "/notes"_json_pointer, ""));

	return true;
}

static bool ParseAnimeInfoJSON(const nlohmann::json& json, Database& database) {
	int id = JSON::GetNumber(json, "/id"_json_pointer, 0);
	if (!id)
		return false;

	Anime& anime = database.items[id];

	anime.SetId(id);
	anime.SetNativeTitle(JSON::GetString<std::string>(json, "/title/native"_json_pointer, ""));
	anime.SetRomajiTitle(JSON::GetString<std::string>(json, "/title/romaji"_json_pointer, ""));
	anime.SetEnglishTitle(JSON::GetString<std::string>(json, "/title/english"_json_pointer, ""));
	anime.SetTitleSynonyms(JSON::GetArray<std::vector<std::string>>(json, "/synonyms"_json_pointer, {}));
	anime.SetEpisodes(JSON::GetNumber(json, "/episodes"_json_pointer, 0));
	anime.SetAiringStatus(Translate::ToSeriesStatus(JSON::GetString<std::string>(json, "/airing_status"_json_pointer, "")));
	anime.SetAirDate(Date(JSON::GetValue(json, "/air_date"_json_pointer)));
	anime.SetGenres(JSON::GetArray<std::vector<std::string>>(json, "/genres"_json_pointer, {}));
	anime.SetProducers(JSON::GetArray<std::vector<std::string>>(json, "/producers"_json_pointer, {}));
	anime.SetFormat(Translate::ToSeriesFormat(JSON::GetString<std::string>(json, "/format"_json_pointer, "")));
	anime.SetSeason(Translate::ToSeriesSeason(JSON::GetString<std::string>(json, "/season"_json_pointer, "")));
	anime.SetAudienceScore(JSON::GetNumber(json, "/audience_score"_json_pointer, 0));
	anime.SetSynopsis(JSON::GetString<std::string>(json, "/synopsis"_json_pointer, ""));
	anime.SetDuration(JSON::GetNumber(json, "/duration"_json_pointer, 0));
	anime.SetPosterUrl(JSON::GetString<std::string>(json, "/poster_url"_json_pointer, ""));

	if (json.contains("/list_data"_json_pointer) && json.at("/list_data"_json_pointer).is_object())
		ParseAnimeUserInfoJSON(json.at("/list_data"_json_pointer), anime);

	return true;
}

bool Database::ParseDatabaseJSON(const nlohmann::json& json) {
	for (const auto& anime_json : json)
		ParseAnimeInfoJSON(anime_json, *this);

	return true;
}

bool Database::LoadDatabaseFromDisk() {
	std::filesystem::path db_path = Filesystem::GetAnimeDBPath();
	Filesystem::CreateDirectories(db_path);

	std::ifstream db_file(db_path);
	if (!db_file)
		return false;

	/* When parsing, do NOT throw exceptions */
	nlohmann::json json;
	try {
		json = json.parse(db_file);
	} catch (std::exception const& ex) {
		std::cerr << "[anime/db] Failed to parse JSON! " << ex.what() << std::endl;
		return false;
	}

	if (!ParseDatabaseJSON(json)) /* How */
		return false;

	return true;
}

Database db;

} // namespace Anime