using System.Net.Http.Headers;
using System.Text;
using System.Text.Json;
using Api.Requests;
using Api.Responses;
using Api.Services.Contracts;
using Api.Settings;
using Microsoft.Extensions.Options;

namespace Api.Services;

public sealed class RagApiClient : IRagApiClient
{
    private readonly HttpClient _http;
    private readonly RagApiSettings _settings;
    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web);

    public RagApiClient(HttpClient http, IOptions<RagApiSettings> options)
    {
        _http = http;
        _settings = options.Value;
        _http.BaseAddress = new Uri(_settings.BaseUrl.TrimEnd('/') + "/");
        if (!string.IsNullOrWhiteSpace(_settings.InternalApiKey))
        {
            _http.DefaultRequestHeaders.Add("X-Internal-Api-Key", _settings.InternalApiKey);
        }
    }

    public async Task<RagIndexResponse> IndexCvPdfAsync(IFormFile file, CancellationToken ct)
    {
        using var content = new MultipartFormDataContent();
        await using var stream = file.OpenReadStream();
        using var fileContent = new StreamContent(stream);
        fileContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
        content.Add(fileContent, "file", file.FileName);
        content.Add(new StringContent("cv"), "documentType");
        content.Add(new StringContent(file.FileName), "title");
        using var response = await _http.PostAsync("api/rag/documents", content, ct);
        return await ReadJsonAsync<RagIndexResponse>(response, ct);
    }

    public async Task<RagIndexResponse> IndexJobTextAsync(string text, string? url, string? title, CancellationToken ct)
    {
        using var content = new MultipartFormDataContent
        {
            { new StringContent(text), "text" },
            { new StringContent("job"), "documentType" },
            { new StringContent(title ?? "Job description"), "title" }
        };
        if (!string.IsNullOrWhiteSpace(url)) content.Add(new StringContent(url), "sourceUrl");
        using var response = await _http.PostAsync("api/rag/documents", content, ct);
        return await ReadJsonAsync<RagIndexResponse>(response, ct);
    }

    public async Task<RagDocumentDetails?> GetDocumentAsync(string documentId, CancellationToken ct)
    {
        using var response = await _http.GetAsync($"api/rag/documents/{Uri.EscapeDataString(documentId)}", ct);
        if (response.StatusCode == System.Net.HttpStatusCode.NotFound) return null;
        return await ReadJsonAsync<RagDocumentDetails>(response, ct);
    }

    public async Task<RagSearchResponse> SearchAsync(RagSearchRequest request, CancellationToken ct)
    {
        using var response = await _http.PostAsync(
            "api/rag/search",
            new StringContent(JsonSerializer.Serialize(request, JsonOptions), Encoding.UTF8, "application/json"),
            ct);
        return await ReadJsonAsync<RagSearchResponse>(response, ct);
    }

    private static async Task<T> ReadJsonAsync<T>(HttpResponseMessage response, CancellationToken ct)
    {
        var json = await response.Content.ReadAsStringAsync(ct);
        if (!response.IsSuccessStatusCode)
        {
            throw new InvalidOperationException($"RAG API failed: {(int)response.StatusCode} {json}");
        }
        return JsonSerializer.Deserialize<T>(json, JsonOptions) ?? throw new InvalidOperationException("RAG API returned invalid JSON.");
    }
}