ln.build/ln.build/commands/CommandEnvironment.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Linq;
using ln.json;
using ln.logging;

namespace ln.build.commands
{
    public class CommandEnvironment : IDictionary<string,string>
    {
        public CommandEnvironment Parent { get; }

        public string WorkingDirectory { get; set; } = Path.GetFullPath(".");

        static string[] DefaultVariables = { "PATH", "HOME", "USERNAME" };
        public Logger Logger { get; set; }
        Dictionary<string,string> variables = new Dictionary<string, string>();

        public ICollection<string> Keys => ((IDictionary<string, string>)variables).Keys;
        public ICollection<string> Values => ((IDictionary<string, string>)variables).Values;
        public int Count => ((ICollection<KeyValuePair<string, string>>)variables).Count;
        public bool IsReadOnly => ((ICollection<KeyValuePair<string, string>>)variables).IsReadOnly;
        public string this[string key] { get => Get(key); set => Set(key,value); }

        public CommandEnvironment(CommandEnvironment parent) : this(parent.Logger) { Parent = parent; WorkingDirectory = parent.WorkingDirectory; }
        public CommandEnvironment(CommandEnvironment parent, Logger logger) : this(logger) { Parent = parent; WorkingDirectory = parent.WorkingDirectory; }
        public CommandEnvironment() : this(Logger.Default)
        { }
        public CommandEnvironment(Logger logger)
        { 
            Logger = logger;

            foreach (string defName in DefaultVariables)
                Set(defName, Environment.GetEnvironmentVariable(defName));
        }
        public CommandEnvironment(IEnumerable<KeyValuePair<string,string>> setup) : this(Logger.Default, setup) { }
        public CommandEnvironment(Logger logger, IEnumerable<KeyValuePair<string,string>> setup) : this(logger)
        {
            foreach (KeyValuePair<string,string> kvp in setup)
                variables.Add(kvp.Key,kvp.Value);
        }


        public string Get(string varName) => Get(varName, null);
        public string Get(string varName,string defValue)
        {
            if (!variables.TryGetValue(varName,out string value))
            {
                if (Parent != null)
                    value = Parent.Get(varName, defValue);
                else
                    value = defValue;
            }
            return value;
        }
        public CommandEnvironment Set(string varName,string value)
        {
            if (value != null)
                variables[varName] = value;
            else
                variables.Remove(varName);

            return this;
        }
        public void Extend(string varName,string value) => Extend(varName, value, ':');
        public void Extend(string varName, string value, char seperator)
        {
            string currentValue = Get(varName, "");
            if (string.Empty.Equals(currentValue))
            {
                currentValue = value;
            } else {
                currentValue = string.Format("{0}{1}{2}",currentValue, seperator, value);
            }
            Set(varName, currentValue);
        }

        public bool Contains(string varName) => variables.ContainsKey(varName);
        public bool Contains(params string[] varNames)
        {
            foreach (string varName in varNames)
            {
                if (!variables.ContainsKey(varName))
                    return false;
            }
            return true;
        }

        public void Add(string key, string value)
        {
            ((IDictionary<string, string>)variables).Add(key, value);
        }

        public bool ContainsKey(string key)
        {
            return ((IDictionary<string, string>)variables).ContainsKey(key);
        }

        public bool Remove(string key)
        {
            return ((IDictionary<string, string>)variables).Remove(key);
        }

        public bool TryGetValue(string key, [MaybeNullWhen(false)] out string value)
        {
            return ((IDictionary<string, string>)variables).TryGetValue(key, out value);
        }

        public void Add(KeyValuePair<string, string> item)
        {
            ((ICollection<KeyValuePair<string, string>>)variables).Add(item);
        }

        public void Clear()
        {
            ((ICollection<KeyValuePair<string, string>>)variables).Clear();
        }

        public bool Contains(KeyValuePair<string, string> item)
        {
            return ((ICollection<KeyValuePair<string, string>>)variables).Contains(item);
        }

        public void CopyTo(KeyValuePair<string, string>[] array, int arrayIndex)
        {
            ((ICollection<KeyValuePair<string, string>>)variables).CopyTo(array, arrayIndex);
        }

        public bool Remove(KeyValuePair<string, string> item)
        {
            return ((ICollection<KeyValuePair<string, string>>)variables).Remove(item);
        }

        public IEnumerator<KeyValuePair<string, string>> GetEnumerator()
        {
            if (Parent != null)
            {
                return Keys.Concat(Parent.Keys).Distinct().Select((k)=>new KeyValuePair<string, string>(k,Get(k))).GetEnumerator();
            } else 
            {
                return ((IEnumerable<KeyValuePair<string, string>>)variables).GetEnumerator();
            }
        }


        public void Apply(JSONObject jsonEnvironment)
        {
            foreach (string key in jsonEnvironment?.Keys ?? new string[0])
            {
                Set(key, jsonEnvironment[key].ToNative().ToString());
            }
        }


        IEnumerator IEnumerable.GetEnumerator()
        {
            return ((IEnumerable)variables).GetEnumerator();
        }
    }
}