using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;

namespace AsbCloudInfrastructure
{

    /// <summary>
    /// stolen from https://github.com/lotosbin/BinbinPredicateBuilder
    /// </summary>
    public static class PredicateBuilder
    {
        /// <summary>
        ///     Combines the first predicate with the second using the logical "and".
        /// </summary>
        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.AndAlso);
        }

        /// <summary>
        ///     Combines the first predicate with the second using the logical "or".
        /// </summary>
        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.OrElse);
        }

        /// <summary>
        ///     Negates the predicate.
        /// </summary>
        public static Expression<Func<T, bool>> Not<T>(this Expression<Func<T, bool>> expression)
        {
            var negated = Expression.Not(expression.Body);
            return Expression.Lambda<Func<T, bool>>(negated, expression.Parameters);
        }

        private static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)
        {
            var map = first.Parameters
                .Select((f, i) => new { f, s = second.Parameters[i] })
                .ToDictionary(p => p.s, p => p.f);

            var tryReplaceParametr = (Expression node) => 
            {
                if (node is ParameterExpression parameter)
                    if (map.TryGetValue(parameter, out ParameterExpression? replacement))
                        return replacement;
                return node;
            };

            var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);
            return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
        }

        class ParameterRebinder : ExpressionVisitor
        {
            private readonly Dictionary<ParameterExpression, ParameterExpression> map;

            private ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
            {
                this.map = map;
            }

            public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map, Expression exp)
            {
                return new ParameterRebinder(map).Visit(exp);
            }

            protected override Expression VisitParameter(ParameterExpression parametr)
            {
                if (map.TryGetValue(parametr, out ParameterExpression? replacement))
                    parametr = replacement;
                return parametr;
            }
        }
    }
}