//-----------------------------------------------------------------------
// <copyright file="Regorus.cs" company="Microsoft">
//    Copyright (c)2012 Microsoft. All rights reserved.
// </copyright>
// <summary>
//    Contains code for the Regorus Policy Engine base class for C# and
// .NET4.0 bindings. Currently this base class is not thread-safe. Make 
// sure we use it in a signle-threaded environment or add additional 
// protection when using it. 
// </summary>
//-----------------------------------------------------------------------


using System;
using System.Text;
using System.IO;
using System.Threading;

namespace Microsoft.WindowsAzure.Regorus.IaaS
{

    public class RegorusPolicyEngine : ICloneable, IDisposable
    {
        unsafe private RegorusFFI.RegorusEngine* E;

        public RegorusPolicyEngine()
        {
            unsafe
            {
                E = RegorusFFI.API.regorus_engine_new();
            }
        }


        public void Dispose()
        {
            unsafe
            {
                if (E != null)
                {
                    RegorusFFI.API.regorus_engine_drop(E);
                    // to avoid Dispose() being called multiple times by mistake.
                    E = null;
                }

            }

        }

        public object Clone()
        {
            var clone = (RegorusPolicyEngine)this.MemberwiseClone();
            unsafe
            {
                clone.E = RegorusFFI.API.regorus_engine_clone(E);
            }
            return clone;

        }

        byte[] NullTerminatedUTF8Bytes(string s)
        {
            return Encoding.UTF8.GetBytes(s + char.MinValue);
        }

        public void AddPolicy(string path, string rego)
        {
            var pathBytes = NullTerminatedUTF8Bytes(path);
            var regoBytes = NullTerminatedUTF8Bytes(rego);

            unsafe
            {
                fixed (byte* pathPtr = pathBytes)
                {
                    fixed (byte* regoPtr = regoBytes)
                    {
                        CheckAndDropResult(RegorusFFI.API.regorus_engine_add_policy(E, pathPtr, regoPtr));
                    }
                }
            }
        }

        public void AddPolicyFromFile(string path)
        {
            var pathBytes = NullTerminatedUTF8Bytes(path);

            unsafe
            {
                fixed (byte* pathPtr = pathBytes)
                {
                    CheckAndDropResult(RegorusFFI.API.regorus_engine_add_policy_from_file(E, pathPtr));
                }
            }
        }

        public void AddPolicyFromPath(string path)
        {
            if (!Directory.Exists(path))
            {
                return;
            }

            string[] regoFiles = Directory.GetFiles(path, "*.rego", SearchOption.AllDirectories);
            foreach (string file in regoFiles)
            {
                AddPolicyFromFile(file);
            }
        }

        public void AddDataJson(string data)
        {
            var dataBytes = NullTerminatedUTF8Bytes(data);

            unsafe
            {
                fixed (byte* dataPtr = dataBytes)
                {
                    CheckAndDropResult(RegorusFFI.API.regorus_engine_add_data_json(E, dataPtr));
                }
            }
        }

        public void AddDataFromJsonFile(string path)
        {
            var pathBytes = NullTerminatedUTF8Bytes(path);

            unsafe
            {
                fixed (byte* pathPtr = pathBytes)
                {
                    CheckAndDropResult(RegorusFFI.API.regorus_engine_add_data_from_json_file(E, pathPtr));

                }
            }
        }

        public void SetInputJson(string input)
        {
            var inputBytes = NullTerminatedUTF8Bytes(input);

            unsafe
            {
                fixed (byte* inputPtr = inputBytes)
                {
                    CheckAndDropResult(RegorusFFI.API.regorus_engine_set_input_json(E, inputPtr));
                }
            }
        }

        public void SetInputFromJsonFile(string path)
        {
            var pathBytes = NullTerminatedUTF8Bytes(path);

            unsafe
            {
                fixed (byte* pathPtr = pathBytes)
                {
                    CheckAndDropResult(RegorusFFI.API.regorus_engine_set_input_from_json_file(E, pathPtr));
                }
            }
        }

        public string EvalQuery(string query)
        {
            var queryBytes = NullTerminatedUTF8Bytes(query);

            var resultJson = "";
            unsafe
            {
                fixed (byte* queryPtr = queryBytes)
                {
                    var result = RegorusFFI.API.regorus_engine_eval_query(E, queryPtr);
                    if (result.status == RegorusFFI.RegorusStatus.RegorusStatusOk)
                    {
                        if (result.output != null)
                        {
                            resultJson = System.Runtime.InteropServices.Marshal.PtrToStringAnsi((IntPtr)result.output);
                        }
                        RegorusFFI.API.regorus_result_drop(result);
                    }
                    else
                    {
                        CheckAndDropResult(result);
                    }
                }
            }
            if (resultJson != null)
            {
                return resultJson;
            }
            else
            {
                return "";
            }
        }

        void CheckAndDropResult(RegorusFFI.RegorusResult result)
        {
            if (result.status != RegorusFFI.RegorusStatus.RegorusStatusOk)
            {
                unsafe
                {
                    var message = System.Runtime.InteropServices.Marshal.PtrToStringAnsi((IntPtr)result.error_message);
                    var ex = new Exception(message);
                    RegorusFFI.API.regorus_result_drop(result);
                    throw ex;
                }
            }
            RegorusFFI.API.regorus_result_drop(result);
        }

    }
}