using System.Net;
using System.Net.Http;
using System.Net.Http.Json;
using System.Text.Json;
using EnvelopeGenerator.Application.Common.Dto;

namespace EnvelopeGenerator.Server.Client.Services;

public class DocumentService(IHttpClientFactory httpClientFactory)
{
    private static readonly JsonSerializerOptions _jsonOptions = new(JsonSerializerDefaults.Web);

    private static HttpRequestException CreateHttpException(string messagePrefix, HttpStatusCode statusCode, string? reasonPhrase)
    {
        var statusCodeInt = (int)statusCode;
        return new HttpRequestException(
            $"{messagePrefix}. Status: {statusCodeInt} ({reasonPhrase ?? "Unknown error"})",
            null,
            statusCode);
    }

    /// <summary>
    /// Fetches the PDF bytes for the given envelope key from the API.
    /// Throws HttpRequestException on failure with appropriate status code.
    /// </summary>
    /// <exception cref="HttpRequestException">Thrown when the API request fails.</exception>
    public async Task<byte[]?> GetDocumentAsync(string envelopeKey, CancellationToken cancel = default)
    {
        using var http = httpClientFactory.CreateClient("EnvelopeGenerator.Server");
        var response = await http.GetAsync($"/api/Document/{Uri.EscapeDataString(envelopeKey)}", cancel);

        if (!response.IsSuccessStatusCode)
            throw CreateHttpException("Failed to load document", response.StatusCode, response.ReasonPhrase);

        var bytes = await response.Content.ReadAsByteArrayAsync(cancel);
        return bytes;
    }

    /// <summary>
    /// Fetches sender document details (including signature elements) by envelope id.
    /// Uses GET /api/Document/details?EnvelopeId={envelopeId}.
    /// </summary>
    public async Task<DocumentDto?> GetSenderDocumentDetailsByEnvelopeIdAsync(int envelopeId, CancellationToken cancel = default)
    {
        using var http = httpClientFactory.CreateClient("EnvelopeGenerator.Server");
        var detailsResponse = await http.GetAsync($"/api/Document/details?EnvelopeId={envelopeId}", cancel);

        if (detailsResponse.StatusCode == HttpStatusCode.NotFound)
        {
            var fallbackBytes = await TryGetSenderDocumentBytesByEnvelopeIdAsync(http, envelopeId, cancel);
            if (fallbackBytes is null)
                return null;

            return new DocumentDto(fallbackBytes, new DocumentDetailsDto
            {
                EnvelopeId = envelopeId,
                AddedWhen = DateTime.UtcNow,
                Elements = []
            });
        }

        if (!detailsResponse.IsSuccessStatusCode)
            throw CreateHttpException("Failed to load sender document details", detailsResponse.StatusCode, detailsResponse.ReasonPhrase);

        var details = await detailsResponse.Content.ReadFromJsonAsync<DocumentDetailsDto>(_jsonOptions, cancel)
            ?? throw new HttpRequestException("Failed to deserialize sender document details response.");

        var byteData = await TryGetSenderDocumentBytesByEnvelopeIdAsync(http, envelopeId, cancel);
        if (byteData is null)
            byteData = [];

        return new DocumentDto(byteData, details);
    }

    /// <summary>
    /// Fetches sender document bytes by envelope id.
    /// Uses GET /api/Document?EnvelopeId={envelopeId}.
    /// </summary>
    public async Task<byte[]?> GetSenderDocumentBytesByEnvelopeIdAsync(int envelopeId, CancellationToken cancel = default)
    {
        using var http = httpClientFactory.CreateClient("EnvelopeGenerator.Server");
        var response = await http.GetAsync($"/api/Document?EnvelopeId={envelopeId}", cancel);

        if (response.StatusCode == HttpStatusCode.NotFound)
            return null;

        if (!response.IsSuccessStatusCode)
            throw CreateHttpException("Failed to load sender document bytes", response.StatusCode, response.ReasonPhrase);

        return await response.Content.ReadAsByteArrayAsync(cancel);
    }

    private static async Task<byte[]?> TryGetSenderDocumentBytesByEnvelopeIdAsync(HttpClient http, int envelopeId, CancellationToken cancel)
    {
        var bytesResponse = await http.GetAsync($"/api/Document?EnvelopeId={envelopeId}", cancel);
        if (bytesResponse.StatusCode == HttpStatusCode.NotFound)
            return null;

        if (!bytesResponse.IsSuccessStatusCode)
            throw CreateHttpException("Failed to load sender document bytes", bytesResponse.StatusCode, bytesResponse.ReasonPhrase);

        return await bytesResponse.Content.ReadAsByteArrayAsync(cancel);
    }
}