package com.annimon.everlastingsummer;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;

/**
 * @author aNNiMON
 */
public final class Lexer {
    
    public static List<Token> tokenize(String input) {
        return new Lexer().process(input).getTokens();
    }
    
    private static final String OPERATOR_CHARS = "=+-()[]!$:";
    private static final TokenType[] OPERATOR_TYPES = new TokenType[] {
        TokenType.EQ,
        TokenType.PLUS, TokenType.MINUS, 
        TokenType.LPAREN, TokenType.RPAREN, TokenType.LBRACKET, TokenType.RBRACKET,
        TokenType.EXCL, TokenType.COMMAND, TokenType.COLON,
    };

    private static final Map<String, TokenType> KEYWORDS;
    static {
        KEYWORDS = new HashMap<String, TokenType>();
        KEYWORDS.put("play", TokenType.PLAY);
        KEYWORDS.put("stop", TokenType.STOP);
        KEYWORDS.put("music", TokenType.MUSIC);
        KEYWORDS.put("ambience", TokenType.AMBIENCE);
        KEYWORDS.put("sound", TokenType.SOUND);
        KEYWORDS.put("sound_loop", TokenType.SOUNDLOOP);
        KEYWORDS.put("fadein", TokenType.FADEIN);
        KEYWORDS.put("fadeout", TokenType.FADEOUT);
        
        KEYWORDS.put("scene", TokenType.SCENE);
        KEYWORDS.put("anim", TokenType.ANIM);
        KEYWORDS.put("bg", TokenType.BG);
        KEYWORDS.put("cg", TokenType.CG);
        KEYWORDS.put("at", TokenType.AT);
        KEYWORDS.put("window", TokenType.WINDOW);
        KEYWORDS.put("hide", TokenType.HIDE);
        KEYWORDS.put("show", TokenType.SHOW);
        KEYWORDS.put("with", TokenType.WITH);
        
        KEYWORDS.put("return", TokenType.RETURN);
        KEYWORDS.put("menu", TokenType.MENU);
        KEYWORDS.put("endmenu", TokenType.ENDMENU);
        KEYWORDS.put("jump", TokenType.JUMP);
        KEYWORDS.put("label", TokenType.LABEL);
        
        KEYWORDS.put("if", TokenType.IF);
        KEYWORDS.put("else", TokenType.ELSE);
        KEYWORDS.put("endif", TokenType.ENDIF);
        
        KEYWORDS.put("renpy.pause", TokenType.RENPY_PAUSE);
        KEYWORDS.put("persistent.sprite_time", TokenType.PERSISTENT_SPRITE_TIME);
        KEYWORDS.put("prolog_time", TokenType.PROLOG_TIME);
        KEYWORDS.put("day_time", TokenType.DAY_TIME);
        KEYWORDS.put("sunset_time", TokenType.SUNSET_TIME);
        KEYWORDS.put("night_time", TokenType.NIGHT_TIME);
    }
    
    private final List<Token> tokens;
    private final StringBuilder buffer;
    
    private TokenizeState state;
    private int pos;

    private enum TokenizeState {
        DEFAULT, NUMBER, OPERATOR, WORD, TEXT, COMMENT
    }
    
    private Lexer() {
        tokens = new ArrayList<Token>();
        buffer = new StringBuilder();
        state = TokenizeState.DEFAULT;
    }
    
    public List<Token> getTokens() {
        return tokens;
    }
    
    public Lexer process(String input) {
        final int length = input.length();
        for (pos = 0; pos < length; pos++) {
            tokenize(input.charAt(pos));
        }
        tokenize('\0');// EOF
        addToken(TokenType.EOF, false);
        input = null;
        return this;
    }
    
    private void tokenize(char ch) {
        switch (state) {
            case DEFAULT: tokenizeDefault(ch); break;
            case WORD: tokenizeWord(ch); break;
            case NUMBER: tokenizeNumber(ch); break;
            case OPERATOR: tokenizeOperator(ch); break;
            case TEXT: tokenizeText(ch); break;
            case COMMENT: tokenizeComment(ch); break;
        }
    }
    
    private void tokenizeDefault(char ch) {
        if (Character.isLetter(ch)) {
            // Слово (ключевое слово или команда)
            buffer.append(ch);
            state = TokenizeState.WORD;
        } else if (Character.isDigit(ch)) {
            // Число
            buffer.append(ch);
            state = TokenizeState.NUMBER;
        } else if (ch == '"') {
            // Текст в "кавычках"
            state = TokenizeState.TEXT;
        } else if (ch == '#') {
            clearBuffer();
            state = TokenizeState.COMMENT;
        } else {
            // Операторы и спецсимволы
            tokenizeOperator(ch);
        }
    }
    
    private void tokenizeWord(char ch) {
        if (Character.isLetterOrDigit(ch) || (ch == '_') || (ch == '.')) {
            buffer.append(ch);
        } else {
            final String word = buffer.toString().toLowerCase(Locale.ENGLISH);
            addToken(KEYWORDS.containsKey(word) ? KEYWORDS.get(word) : TokenType.WORD);
        }
    }
    
    private void tokenizeNumber(char ch) {
        // Целое или вещественное число.
        if (ch == '.') {
            // Пропускаем десятичные точки, если они уже были в числе.
            if (buffer.indexOf(".") == -1) buffer.append(ch);
        } else if (Character.isDigit(ch)) {
            buffer.append(ch);
        } else {
            addToken(TokenType.NUMBER);
        }
    }
    
    private void tokenizeOperator(char ch) {
        final int index = OPERATOR_CHARS.indexOf(ch);
        if (index != -1) {
            addToken(OPERATOR_TYPES[index], false);
        }
    }
    
    private void tokenizeText(char ch) {
        if (ch == '"') {
            final int len = buffer.length();
            // Добавляем токен, если не было экранирования символа кавычки.
            if (len == 0 ||
                    ( (len > 0) && (buffer.charAt(len - 1) != '\\') )) {
                addToken(TokenType.TEXT, false);
                return;
            }
            // Экранируем символ кавычки.
            if (len > 0) {
                buffer.setCharAt(len - 1, '\"');
                return;
            }
        }
        buffer.append(ch);
    }
    
    private void tokenizeComment(char ch) {
        if (ch == '\n' || ch == '\r') {
            state = TokenizeState.DEFAULT;
        }
    }
    
    private void addToken(TokenType type) {
        addToken(type, true);
    }
    
    private void addToken(TokenType type, boolean reprocessLastChar) {
        tokens.add(new Token(buffer.toString(), type));
        clearBuffer();
        if (reprocessLastChar) pos--;
        state = TokenizeState.DEFAULT;
    }

    private void clearBuffer() {
        buffer.setLength(0);
    }
}