package io.gitlab.jfronny.muscript.compiler;

import io.gitlab.jfronny.muscript.compiler.expr.*;
import io.gitlab.jfronny.muscript.compiler.expr.bool.*;
import io.gitlab.jfronny.muscript.compiler.expr.common.Equal;
import io.gitlab.jfronny.muscript.compiler.expr.dynamic.*;
import io.gitlab.jfronny.muscript.compiler.expr.number.compare.Greater;
import io.gitlab.jfronny.muscript.compiler.expr.number.compare.Less;
import io.gitlab.jfronny.muscript.compiler.expr.number.math.*;
import io.gitlab.jfronny.muscript.compiler.expr.string.Concatenate;
import io.gitlab.jfronny.muscript.compiler.expr.unresolved.UnresolvedConditional;
import io.gitlab.jfronny.muscript.error.*;

import java.util.ArrayList;
import java.util.List;

public class Parser {
    private final Lexer lexer;

    private final TokenData previous = new TokenData();
    private final TokenData current = new TokenData();

    public static Expr<?> parse(String source) {
        return new Parser(new Lexer(source)).parse().optimize();
    }

    public Parser(Lexer lexer) {
        this.lexer = lexer;
    }

    public Expr<?> parse() {
        advance();
        return expression();
    }

    // Expressions
    private Expr<?> expression() {
        try {
            return conditional();
        } catch (RuntimeException e) {
            if (e instanceof ParseException) throw e;
            else if (e instanceof LocationalException le) {
                throw new ParseException(le.asPrintable(lexer.source));
            } else throw error(e.getMessage());
        }
    }

    private Expr<?> conditional() {
        Expr<?> expr = and();

        if (match(Token.QuestionMark)) {
            int character = previous.start;
            Expr<?> trueExpr = expression();
            consume(Token.Colon, "Expected ':' after first part of condition.");
            Expr<?> falseExpr = expression();
            expr = new UnresolvedConditional(character, asBool(expr), trueExpr, falseExpr);
        }

        return expr;
    }

    private Expr<?> and() {
        Expr<?> expr = or();

        while (match(Token.And)) {
            int character = previous.start;
            Expr<?> right = or();
            expr = new And(character, asBool(expr), asBool(right));
        }

        return expr;
    }

    private Expr<?> or() {
        Expr<?> expr = equality();

        while (match(Token.Or)) {
            int character = previous.start;
            Expr<?> right = equality();
            expr = new Or(character, asBool(expr), asBool(right));
        }

        return expr;
    }

    private Expr<?> equality() {
        Expr<?> expr = concat();

        while (match(Token.EqualEqual, Token.BangEqual)) {
            Token op = previous.token;
            int character = previous.start;
            Expr<?> right = concat();
            BoolExpr e = new Equal(character, expr, right);
            if (op == Token.BangEqual) e = new Not(character, e);
            expr = e;
        }

        return expr;
    }

    private Expr<?> concat() {
        Expr<?> expr = comparison();

        while (match(Token.Concat)) {
            int character = previous.start;
            Expr<?> right = comparison();
            expr = new Concatenate(character, asString(expr), asString(right));
        }

        return expr;
    }

    private Expr<?> comparison() {
        Expr<?> expr = term();

        while (match(Token.Greater, Token.GreaterEqual, Token.Less, Token.LessEqual)) {
            Token op = previous.token;
            int character = previous.start;
            NumberExpr right = asNumber(term());
            expr = switch (op) {
                case Greater -> new Greater(character, asNumber(expr), right);
                case GreaterEqual -> new Not(character, new Less(character, asNumber(expr), right));
                case Less -> new Less(character, asNumber(expr), right);
                case LessEqual -> new Not(character, new Greater(character, asNumber(expr), right));
                default -> throw new IllegalStateException();
            };
        }

        return expr;
    }

    private Expr<?> term() {
        Expr<?> expr = factor();

        while (match(Token.Plus, Token.Minus)) {
            Token op = previous.token;
            int character = previous.start;
            NumberExpr right = asNumber(factor());
            expr = switch (op) {
                case Plus -> new Plus(character, asNumber(expr), right);
                case Minus -> new Minus(character, asNumber(expr), right);
                default -> throw new IllegalStateException();
            };
        }

        return expr;
    }

    private Expr<?> factor() {
        Expr<?> expr = exp();

        while (match(Token.Star, Token.Slash, Token.Percentage)) {
            Token op = previous.token;
            int character = previous.start;
            NumberExpr right = asNumber(exp());
            expr = switch (op) {
                case Star -> new Multiply(character, asNumber(expr), right);
                case Slash -> new Divide(character, asNumber(expr), right);
                case Percentage -> new Modulo(character, asNumber(expr), right);
                default -> throw new IllegalStateException();
            };
        }

        return expr;
    }

    private Expr<?> exp() {
        Expr<?> expr = unary();

        while (match(Token.UpArrow)) {
            int character = previous.start;
            NumberExpr right = asNumber(unary());
            expr = new Power(character, asNumber(expr), right);
        }

        return expr;
    }

    private Expr<?> unary() {
        if (match(Token.Bang, Token.Minus)) {
            Token op = previous.token;
            int character = previous.start;
            Expr<?> right = unary();
            return switch (op) {
                case Bang -> new Not(character, asBool(right));
                case Minus -> new Invert(character, asNumber(right));
                default -> throw new IllegalStateException();
            };
        }

        return call();
    }

    private Expr<?> call() {
        Expr<?> expr = primary();

        while (match(Token.LeftParen, Token.Dot, Token.LeftBracket)) {
            int character = previous.start;
            expr = switch (previous.token) {
                case LeftParen -> finishCall(character, expr);
                case Dot -> {
                    TokenData name = consume(Token.Identifier, "Expected field name after '.'.");
                    yield new Get(character, asDynamic(expr), Expr.literal(name.start, name.lexeme));
                }
                case LeftBracket -> {
                    expr = new Get(character, asDynamic(expr), expression());
                    consume(Token.RightBracket, "Expected closing bracket");
                    yield expr;
                }
                default -> throw new IllegalStateException();
            };
        }

        return expr;
    }

    private Expr<?> finishCall(int character, Expr<?> callee) {
        List<DynamicExpr> args = new ArrayList<>(2);

        if (!check(Token.RightParen)) {
            do {
                args.add(asDynamic(expression()));
            } while (match(Token.Comma));
        }

        consume(Token.RightParen, "Expected ')' after function arguments.");
        return new Call(character, asDynamic(callee), args);
    }

    private Expr<?> primary() {
        if (match(Token.Null)) return Expr.literalNull(previous.start);
        if (match(Token.String)) return Expr.literal(previous.start, previous.lexeme);
        if (match(Token.True, Token.False)) return Expr.literal(previous.start, previous.lexeme.equals("true"));
        if (match(Token.Number)) return Expr.literal(previous.start, Double.parseDouble(previous.lexeme));
        if (match(Token.Identifier)) return new Variable(previous.start, previous.lexeme);

        if (match(Token.LeftParen)) {
            Expr<?> expr = expression();
            consume(Token.RightParen, "Expected ')' after expression.");
            return expr;
        }

        throw error("Expected expression.");
    }

    // Type conversion
    private BoolExpr asBool(Expr<?> expression) {
        try {
            return expression.asBoolExpr();
        } catch (TypeMismatchException e) {
            throw new ParseException(LocationalError.create(lexer.source, expression.character, e.getMessage()));
        }
    }

    private NumberExpr asNumber(Expr<?> expression) {
        try {
            return expression.asNumberExpr();
        } catch (TypeMismatchException e) {
            throw new ParseException(LocationalError.create(lexer.source, expression.character, e.getMessage()));
        }
    }

    private StringExpr asString(Expr<?> expression) {
        try {
            return expression.asStringExpr();
        } catch (TypeMismatchException e) {
            throw new ParseException(LocationalError.create(lexer.source, expression.character, e.getMessage()));
        }
    }

    private DynamicExpr asDynamic(Expr<?> expression) {
        try {
            return expression.asDynamicExpr();
        } catch (TypeMismatchException e) {
            throw new ParseException(LocationalError.create(lexer.source, expression.character, e.getMessage()));
        }
    }

    // Helpers
    private ParseException error(String message) {
        return new ParseException(LocationalError.create(lexer.source, current.current - 1, message));
    }

    private TokenData consume(Token token, String message) {
        if (check(token)) return advance();
        throw error(message);
    }

    private boolean match(Token... tokens) {
        for (Token token : tokens) {
            if (check(token)) {
                advance();
                return true;
            }
        }

        return false;
    }

    private boolean check(Token token) {
        if (isAtEnd()) return false;
        return current.token == token;
    }

    private TokenData advance() {
        previous.set(current);

        lexer.next();
        current.set(lexer.token, lexer.lexeme, lexer.start, lexer.current, lexer.ch);

        if (current.token == Token.Error) {
            throw error(current.lexeme);
        }

        return previous;
    }

    private boolean isAtEnd() {
        return current.token == Token.EOF;
    }

    // Token data
    private static class TokenData {
        public Token token;
        public String lexeme;
        public int start, current;
        public char ch;

        public void set(Token token, String lexeme, int start, int current, char ch) {
            this.token = token;
            this.lexeme = lexeme;
            this.start = start;
            this.current = current;
            this.ch = ch;
        }

        public void set(TokenData data) {
            set(data.token, data.lexeme, data.start, data.current, data.ch);
        }

        @Override
        public String toString() {
            return String.format("%s '%s'", token, lexeme);
        }
    }

    // Parse Exception
    public static class ParseException extends RuntimeException {
        public final LocationalError error;

        public ParseException(LocationalError error) {
            super(error.toString());
            this.error = error;
        }
    }
}