#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
#include <sstream>

#include "utils.h"
#include "Board.h"
#include "Move.h"
#include "search.h"
#include "uci.h"

static const std::string usage{"usage: pgn2fen [--scored] [<input>]"};

// Convert PGN (Portable Game Notation) input stream to single FENs
// streamed to stdout
void pgn2fen(std::istream& input, const bool only_scored) {

    // Instantiate Boards, the start of every game as well as the current state
    // of the Board while processing a PGN game
    Board startpos, pos;

    // Read input line by line
    std::string line;
    while (std::getline(input, line)) {
        // Skip empty and metadata lines (every PGN game starts with "<nr>.")
        if (line.empty() || line.front() == '[') {
            continue;
        }

        // Reset position to the start position, every game starts here!
        pos = startpos;

        // Read game content (assuming one line is the entire game)
        std::istringstream game(line);
        std::string count, san, token, eval;
        while (game >> count >> san >> token) {
            // Consume/Parse PGN comments
            if (only_scored) {
                // consume the comment and search for an evaluation
                bool has_score = false;
                while (game >> token) {
                    // Search for evaluation token (position score _after_ the move)
                    if (token == "[%eval") {
                        game >> eval;
                        eval.pop_back();    // delete trailing ']'
                        has_score = true;
                        // Consume the remainder of the comment (ignore it)
                        std::getline(game, token, '}');
                        break;
                    } else if (token == "}") {
                        break;
                    }
                }
                // In case of not finding an evaluation, skip the game (_not_ an error)
                if (!has_score) {
                    break;
                }
            } else {
                // Consume the remainder of the comment (ignore it)
                std::getline(game, token, '}');
            }

            // Perform move
            bool parseError = false;
            Move move = UCI::parseSAN(san, pos, parseError);
            if (parseError) {
                std::cerr << "[ Error ] Parsing '" << san << "' at position '"
                    << pos.fen() << "' failed." << std::endl;
            }
            move = pos.isLegal(move); // validate legality and extend move info
            if (move) {
                pos.make(move);
            } else {
                std::cerr << "[ Error ] Encountered illegal move '" << san
                    << " (" << move
                    << ") ' at position '" << pos.fen() << "'." << std::endl;
                break;
            }

            // Write positions
            if (only_scored) {
                // Ingore "check mate in" scores (not relevant for eval training)
                // Do this after "make move" in situations where the check mate
                // was overlooked, leading to new positions
                if (eval.length() && eval[0] == '#') {
                    continue;
                }
                // Otherwise, classic eval score to be parsed in centipawns
                std::cout << pos.fen() << "; " << eval << '\n';
            } else {
                // Write only the position FEN
                std::cout << pos.fen() << '\n';
            }
        }
    }
}


int main(int argn, char* argv[]) {
    // Setup control variables
    bool only_scored = false;
    std::string file = "";

    // Parse command arguments
    switch (argn) {
        case 1:
            break;
        case 2:
            if (std::string("--scored") == argv[1]) {
                only_scored = true;
            } else {
                file = argv[1];
            }
            break;
        case 3:
            if (std::string("--scored") != argv[1]) {
                std::cout << usage << std::endl;
                return 1;
            }
            only_scored = true;
            file = argv[2];
            break;
        default:
            std::cout << usage << std::endl;
            return 1;
    }

    // Invoke converter ether with file input or stdin
    if (file == "") {
        pgn2fen(std::cin, only_scored);
    } else {
        // Open input file
        std::ifstream input(file);
        if (!input) {
            std::cerr << "Error opening '" << file << "'" << std::endl;
            return 1;
        }

        pgn2fen(input, only_scored);
    }

    return 0;
}