EasyDevCoreV4/EasyDevCore.Configuration/Configuration/SubstitutingConfigurationProvider.cs

using Microsoft.Extensions.Configuration;
using System.Collections.Generic;
using System.Linq;
using EasyDevCore.Common;

namespace EasyDevCore.Configuration
{
    /// <summary>
    /// Auto substitute value from variableSection into section with value have data contains {@KeyName}
    /// </summary>
    /// <seealso cref="Microsoft.Extensions.Configuration.ConfigurationProvider" />
    public class SubstitutingConfigurationProvider : ConfigurationProvider
    {
        private readonly IConfigurationRoot _configurationRoot;
        private readonly string _variablesSection;
        private Dictionary<string, string> _variables = null;

        /// <summary>
        /// Initializes a new instance of the <see cref="SubstitutingConfigurationProvider"/> class.
        /// </summary>
        /// <param name="configurationRoot">The configuration root.</param>
        /// <param name="variablesSection">The variables section.</param>
        public SubstitutingConfigurationProvider(IConfigurationRoot configurationRoot, string variablesSection)
        {
            _configurationRoot = configurationRoot;
            _variablesSection = variablesSection;
        }

        /// <summary>
        /// Attempts to find a value with the given key, returns true if one is found, false otherwise.
        /// </summary>
        /// <param name="key">The key to lookup.</param>
        /// <param name="value">The value found at key if one is found.</param>
        /// <returns>True if key has a value, false otherwise.</returns>
        public override bool TryGet(string key, out string value)
        {
            try
            {
                foreach (var provider in _configurationRoot.Providers.Reverse())
                {
                    if (provider != this)
                    {
                        if (provider.TryGet(key, out value))
                        {
                            value = SubstitutePlaceholders(value);
                            return true;
                        }
                    }
                }
            }
            catch { }
            value = null;
            return false;
        }

        /// <summary>
        /// Sets a value for a given key.
        /// </summary>
        /// <param name="key">The configuration key to set.</param>
        /// <param name="value">The value to set.</param>
        public override void Set(string key, string value)
        {
            foreach (var provider in _configurationRoot.Providers)
            {
                if (provider != this)
                {
                    provider.Set(key, value);
                }
            }
        }

        /// <summary>
        /// Loads (or reloads) the data for this provider.
        /// </summary>
        public override void Load()
        {
            if(_variables != null)
            {
                _variables.Clear();
            } 
            else
            {
                _variables = new();
            }
            _configurationRoot.GetSection(_variablesSection).GetChildren().ForEach(kp => _variables.Add(kp.Key, kp.Value ?? string.Empty));
        }

        private string SubstitutePlaceholders(string value)
        {
            if (value == null || !value.Contains("{@")) return value;

            foreach (var varriableName in _variables)
            {
                value = value.Replace($"{{@{varriableName.Key}}}", varriableName.Value);
                if(!value.Contains("{@"))
                {
                    break;
                }    
            }

            return value;
        }
    }
}