using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using Sprache;
using System.Globalization;
using XNeedle.Parser.Elements;
using Part = XNeedle.Parser.Elements.Part;
using NullPart = XNeedle.Parser.Elements.NullPart;
using XNeedle.Transformation;
using Rule = XNeedle.Transformation.Rule;
using System.Data;
using System.ComponentModel.DataAnnotations;
using System.Text;

namespace XNeedle.Parser
{
        public class XnParser
    {
        static readonly ParameterExpression CtxParam = Expression.Parameter(typeof(Context), "ctx");

        static Parser<ExpressionType> Operator(string op, ExpressionType opType)
        {
            return Parse.String(op).Token().Return(opType);
        }
        
        //static MethodInfo ConcatMethod = typeof(string).GetMethod("Concat", new[] { typeof(string), typeof(string) }); 
        static readonly Parser<ExpressionType> Add = Operator("+", ExpressionType.AddChecked);
        static readonly Parser<ExpressionType> Subtract = Operator("-", ExpressionType.SubtractChecked);
        static readonly Parser<ExpressionType> Multiply = Operator("*", ExpressionType.MultiplyChecked);
        static readonly Parser<ExpressionType> Divide = Operator("/", ExpressionType.Divide);
        static readonly Parser<ExpressionType> Modulo = Operator("%", ExpressionType.Modulo);
        static readonly Parser<ExpressionType> Power = Operator("^", ExpressionType.Power);

        static Parser<Expression> Function(Context ctx)
        {
            return
            from name in Parse.Letter.AtLeastOnce().Text()
            from lparen in Parse.Char('(')
            from expr in Parse.Ref(() => Expr(ctx)).DelimitedBy(Parse.Char(',').Token()).Optional()
            from rparen in Parse.Char(')')
            select CallFunction(ctx, name, expr.GetOrElse(new Expression[0]).ToArray());
        }

        static Expression CallFunction(Context ctx, string name, Expression[] parameters)
        {
            var mathMethodInfo = typeof(Math).GetTypeInfo().GetMethod(name, parameters.Select(e => e.Type).ToArray());
            if (mathMethodInfo != null)
            {
                return Expression.Call(mathMethodInfo, parameters);
            }
            var ctxMethodInfo = typeof(ContextFunctions).GetTypeInfo().GetMethod(name, parameters.Select(e => e.Type).Prepend(typeof(Context)).ToArray());
            if (ctxMethodInfo != null)
            {
                return Expression.Call(ctxMethodInfo, parameters.Prepend(CtxParam).ToArray());
            }

            throw new ParseException(string.Format("Function '{0}({1})' does not exist.", name,
                                                        string.Join(",", parameters.Select(e => e.Type.Name))));
        }

        static readonly Parser<Expression> NumberConstant =
                Parse.Decimal
                .Select(x => Expression.Constant(double.Parse(x)))
                .Named("number");

        private static readonly Parser<Expression> StringConstant =
            from open in Parse.Char('"')
            from value in Parse.CharExcept('"').Many().Text()
            from close in Parse.Char('"')
            select Expression.Constant(new string(value));

        static Parser<Expression> Factor(Context ctx)
        {
            return (from lparen in Parse.Char('(')
                from expr in Parse.Ref(() => Expr(ctx))
                from rparen in Parse.Char(')')
                select expr).Named("expression")
                .XOr(NumberConstant)
                .XOr(StringConstant)
                .XOr(Function(ctx));
        }

        static Parser<Expression> Operand(Context ctx)
        {
            return ((from sign in Parse.Char('-')
                from factor in Factor(ctx)
                select Expression.Negate(factor)
                ).XOr(Factor(ctx))).Token();
        }
        static Parser<Expression> InnerTerm(Context ctx)
        {
            return Parse.ChainRightOperator(Power, Operand(ctx), Expression.MakeBinary);
        }

        static Parser<Expression> Term(Context ctx)
        {
            return Parse.ChainOperator(Multiply.Or(Divide).Or(Modulo), InnerTerm(ctx), Expression.MakeBinary);
        }

        static Parser<Expression> ConcatExpr(Context ctx)
        {
            var concatMethod = typeof(string).GetMethod("Concat", new[] { typeof(string), typeof(string) }); 
            return
                from left in StringConstant.Or(Function(ctx))
                from op in Parse.String("..").Token()
                from right in StringConstant.Or(Function(ctx))
                select Expression.Add(left, right, concatMethod);
        }

        static Parser<Expression> ArithExpr(Context ctx)
        {
            return Parse.ChainOperator(Add.Or(Subtract), Term(ctx), Expression.MakeBinary);
        }

        static Parser<Expression> Expr(Context ctx)
        {
            return ConcatExpr(ctx).Or(ArithExpr(ctx));
        }

        static Parser<ExpressionPart> ExprPart(Context ctx)
        {
            return Expr(ctx).Select(body =>
            {
                Expression stringBody = body.Type == typeof(string)
                    ? body
                    : Expression.Call(body, typeof(object).GetMethod("ToString", Type.EmptyTypes)!);
                return new ExpressionPart { Expr = Expression.Lambda<Func<Context, string>>(stringBody, CtxParam) };
            });
        }

        static readonly Parser<string> XPath =
            from path in Parse.LetterOrDigit
                                .XOr(Parse.Char('/'))
                                .XOr(Parse.Char(' '))
                                .XOr(Parse.Char('['))
                                .XOr(Parse.Char(']'))
                                .XOr(Parse.Char('='))
                                .XOr(Parse.Char('.'))
                                .XOr(Parse.Char('_'))
                                .XOr(Parse.Char('*'))
                                .XOr(Parse.Char('@'))
                                .XOr(Parse.Char('#'))
                                .XOr(Parse.Char('('))
                                .XOr(Parse.Char(')'))
                                .XOr(Parse.Char('\''))
                                .Many()
            select new string(path.ToArray());

        static Parser<T> Selector<T>(Parser<T> selection)
        {
            return from open in Parse.String("$(\"").Token()
                from s in selection
                from close in Parse.String("\")").Token()
                select s;
        }

        public static readonly Parser<string> XPathSelector = Selector(XPath);

        public static readonly Parser<string> Identifier =
                from first in Parse.Letter.Once()
                from rest in Parse.LetterOrDigit.XOr(Parse.Char('-')).XOr(Parse.Char('_')).Many()
                select new string(first.Concat(rest).ToArray());

        private static readonly Parser<string> StringObject =
            from open in Parse.Char('"')
            from value in Parse.CharExcept('"').Many().Text()
            from close in Parse.Char('"')
            select new string(value);

        private static readonly Parser<string> NumberObject =
            Parse.DecimalInvariant
                .Select(s => double.Parse(s, CultureInfo.InvariantCulture))
                .Select(v => v.ToString());

        public static readonly Parser<string> Argument =
            from argument in StringObject.Or(NumberObject)
            select argument;

        public static readonly Parser<Call> CallObject =
            from identifier in Identifier
            from open in Parse.Char('(')
            from arguments in Argument.DelimitedBy(Parse.Char(',').Token())
            from close in Parse.Char(')')
            select new Call{Identifier = new string(identifier.ToArray()), Arguments = arguments};

        /*public static readonly Parser<Expression> ExpressionObject =
            from expression in CallObject
        */
        
        public static CommentParser Comment = new CommentParser { Single = "#", NewLine = Environment.NewLine };

         public static readonly Parser<Part> BangObject = 
            from bang in Parse.Char('!')
            from name in Parse.AnyChar.Until(Parse.Char('('))
            from arguments in Argument.DelimitedBy(Parse.Char(',').Token())
            from bclose in Parse.Char(')')
            let ctx = new Context{XPathSelector = "//*."}            
            from ws1 in Parse.WhiteSpace.Many().Optional()
            from open in Parse.Char('{')
            from ws2 in Parse.WhiteSpace.Many().Optional()
            from expressions in (
                from expr in Parse.Ref(() => BangObject)
                    .Or(Parse.Ref(() => RuleObject))
                    .Or(ExprPart(ctx).Select(e => (Part)e))
                from semi in Parse.Char(';').Token()
                select expr
            ).Many()
            from ws3 in Parse.WhiteSpace.Many().Optional()
            from close in Parse.Char('}')
            select new Bang{Name = new string([.. name]), Arguments = arguments, Body = expressions};

        public static readonly Parser<Part> RuleObject =
            from selector in Selector(XPath).Token()
            let ctx = new Context{XPathSelector = selector}
            from ws1 in Parse.WhiteSpace.Many().Optional()
            from open in Parse.Char('{')
            from ws2 in Parse.WhiteSpace.Many().Optional()
            from expressions in (
                from expr in Parse.Ref(() => BangObject)
                    .Or(Parse.Ref(() => RuleObject))
                    .Or(ExprPart(ctx).Select(e => (Part)e))
                from semi in Parse.Char(';').Token()
                select expr
            ).Many()
            from ws3 in Parse.WhiteSpace.Many().Optional()
            from close in Parse.Char('}')
            select new Rule{XPathSelector = selector, Body = expressions};

        public static readonly Parser<IEnumerable<Part>> Rules =
            (from rule in RuleObject.Token()
             from semi in Parse.Char(';').Token()
             select rule)
            .Many()
            .End();

        static public string StripComments(string source)
        {
            var result = new StringBuilder();
            foreach (var line in source.Split('\n'))
            {
                bool inSingle = false, inDouble = false;
                int commentIdx = -1;
                for (int i = 0; i < line.Length; i++)
                {
                    char c = line[i];
                    if (c == '\'' && !inDouble) inSingle = !inSingle;
                    else if (c == '"' && !inSingle) inDouble = !inDouble;
                    else if (c == '#' && !inSingle && !inDouble)
                    {
                        commentIdx = i;
                        break;
                    }
                }
                result.Append(commentIdx >= 0 ? line[..commentIdx] : line);
                result.Append('\n');
            }
            return result.ToString();
        }
    }
}