using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;
using UnityEngine;
using UnityEngine.Networking;

public sealed class BriskHttpClient
{
    private readonly BriskContext _context;

    public BriskHttpClient(BriskContext context)
    {
        _context = context;
    }

    public Task<Dictionary<string, object>> GetDataAsync(string path, Dictionary<string, string> query = null, bool auth = false)
    {
        return SendForDictionaryAsync(UnityWebRequest.kHttpVerbGET, path, query, null, auth);
    }

    public Task<object> GetRawDataAsync(string path, Dictionary<string, string> query = null, bool auth = false)
    {
        return SendRawJsonAsync(UnityWebRequest.kHttpVerbGET, path, query, null, auth);
    }

    public Task<Dictionary<string, object>> PostJsonAsync(string path, object body, bool auth = false)
    {
        return SendForDictionaryAsync(UnityWebRequest.kHttpVerbPOST, path, null, body, auth);
    }

    public Task<object> PostJsonRawAsync(string path, object body, bool auth = false)
    {
        return SendRawJsonAsync(UnityWebRequest.kHttpVerbPOST, path, null, body, auth);
    }

    public Task<object> PostJsonRawAsync(string path, object body, bool auth, Dictionary<string, string> query)
    {
        return SendRawJsonAsync(UnityWebRequest.kHttpVerbPOST, path, query, body, auth);
    }

    public Task<object> SendPutJsonRawAsync(string path, object body, bool auth = false)
    {
        return SendRawJsonAsync(UnityWebRequest.kHttpVerbPUT, path, null, body, auth);
    }

    public Task<object> SendDeleteJsonRawAsync(string path, Dictionary<string, string> query = null, bool auth = false)
    {
        return SendRawJsonAsync(UnityWebRequest.kHttpVerbDELETE, path, query, null, auth);
    }

    public async Task<Dictionary<string, object>> PostMultipartAsync(string path, List<IMultipartFormSection> formSections, bool auth = false)
    {
        using (var request = UnityWebRequest.Post(BuildUrl(path, null), formSections))
        {
            if (auth)
            {
                AddAuthorizationHeader(request);
            }

            request.SetRequestHeader("Accept", "application/json");
            await SendRequestAsync(request);
            return ParseEnvelope(request) as Dictionary<string, object> ?? new Dictionary<string, object>();
        }
    }

    public async Task<BriskBinaryResponse> GetBytesAsync(string path, Dictionary<string, string> query = null, bool auth = false)
    {
        using (var request = BuildRequest(UnityWebRequest.kHttpVerbGET, path, query, null, auth))
        {
            await SendRequestAsync(request);
            EnsureSuccessOrThrow(request);
            return new BriskBinaryResponse
            {
                Bytes = request.downloadHandler != null ? request.downloadHandler.data : Array.Empty<byte>(),
                Headers = request.GetResponseHeaders() ?? new Dictionary<string, string>()
            };
        }
    }

    private async Task<Dictionary<string, object>> SendForDictionaryAsync(string method, string path, Dictionary<string, string> query, object body, bool auth)
    {
        var data = await SendRawJsonAsync(method, path, query, body, auth);
        return data as Dictionary<string, object> ?? new Dictionary<string, object>();
    }

    private async Task<object> SendRawJsonAsync(string method, string path, Dictionary<string, string> query, object body, bool auth)
    {
        using (var request = BuildRequest(method, path, query, body, auth))
        {
            await SendRequestAsync(request);
            return ParseEnvelope(request);
        }
    }

    private UnityWebRequest BuildRequest(string method, string path, Dictionary<string, string> query, object body, bool auth)
    {
        var url = BuildUrl(path, query);
        var request = new UnityWebRequest(url, method)
        {
            downloadHandler = new DownloadHandlerBuffer()
        };

        request.SetRequestHeader("Accept", "application/json");

        if (body != null)
        {
            var json = BriskJson.Serialize(body);
            var bytes = Encoding.UTF8.GetBytes(json);
            request.uploadHandler = new UploadHandlerRaw(bytes);
            request.SetRequestHeader("Content-Type", "application/json");
        }

        if (auth)
        {
            AddAuthorizationHeader(request);
        }

        return request;
    }

    private async Task SendRequestAsync(UnityWebRequest request)
    {
        try
        {
            var operation = request.SendWebRequest();
            var taskSource = new TaskCompletionSource<bool>();
            operation.completed += _ => taskSource.TrySetResult(true);
            await taskSource.Task;
        }
        catch (Exception exception)
        {
            throw new BriskNetworkException("Failed to send request.", exception);
        }

        if (request.result == UnityWebRequest.Result.ConnectionError || request.result == UnityWebRequest.Result.DataProcessingError)
        {
            throw new BriskNetworkException(request.error ?? "Network error.");
        }
    }

    private object ParseEnvelope(UnityWebRequest request)
    {
        var httpStatus = (int)request.responseCode;
        var responseText = request.downloadHandler != null ? request.downloadHandler.text : null;

        if (string.IsNullOrWhiteSpace(responseText))
        {
            if (httpStatus >= 200 && httpStatus < 300)
            {
                return new Dictionary<string, object>();
            }

            throw new BriskHttpException(httpStatus, request.error ?? "HTTP error.");
        }

        var payload = BriskJson.Deserialize(responseText) as Dictionary<string, object>;
        if (payload == null)
        {
            throw new BriskHttpException(httpStatus, "Invalid JSON response.");
        }

        var code = BriskValueReader.GetInt(payload, "code");
        var message = BriskValueReader.GetString(payload, "message") ?? request.error ?? "Request failed.";
        if (code != 0 || httpStatus < 200 || httpStatus >= 300)
        {
            throw BriskErrorClassifier.Classify(httpStatus, code, message);
        }

        if (BriskValueReader.TryGetValue(payload, "data", out var dataValue))
        {
            return dataValue;
        }

        return new Dictionary<string, object>();
    }

    private void EnsureSuccessOrThrow(UnityWebRequest request)
    {
        var httpStatus = (int)request.responseCode;
        if (httpStatus >= 200 && httpStatus < 300)
        {
            return;
        }

        throw CreateExceptionFromResponse(request);
    }

    private BriskException CreateExceptionFromResponse(UnityWebRequest request)
    {
        var httpStatus = (int)request.responseCode;
        var responseText = request.downloadHandler != null ? request.downloadHandler.text : null;
        if (!string.IsNullOrWhiteSpace(responseText))
        {
            var payload = BriskJson.Deserialize(responseText) as Dictionary<string, object>;
            if (payload != null)
            {
                var code = BriskValueReader.GetInt(payload, "code");
                var message = BriskValueReader.GetString(payload, "message") ?? request.error ?? "Request failed.";
                return BriskErrorClassifier.Classify(httpStatus, code, message);
            }
        }

        return new BriskHttpException(httpStatus, request.error ?? "HTTP error.");
    }

    private void AddAuthorizationHeader(UnityWebRequest request)
    {
        var token = _context.Session.AccessToken;
        if (string.IsNullOrWhiteSpace(token))
        {
            throw new BriskAuthExpiredException("Missing access token.");
        }

        request.SetRequestHeader("Authorization", "Bearer " + token);
    }

    private string BuildUrl(string path, Dictionary<string, string> query)
    {
        var trimmedPath = path.StartsWith("/") ? path : "/" + path;
        var url = _context.Options.BaseUrl + trimmedPath;
        if (query == null || query.Count == 0)
        {
            return url;
        }

        var builder = new StringBuilder(url);
        var first = true;
        foreach (var pair in query)
        {
            if (string.IsNullOrWhiteSpace(pair.Value))
            {
                continue;
            }

            if (first)
            {
                builder.Append('?');
            }
            else
            {
                builder.Append('&');
            }

            builder.Append(UnityWebRequest.EscapeURL(pair.Key));
            builder.Append('=');
            builder.Append(UnityWebRequest.EscapeURL(pair.Value));
            first = false;
        }

        return builder.ToString();
    }
}