using System.Net.Http.Json;
using System.Text.Json;
using System.Text.Json.Serialization;
using TrajetKmTracker.Api.Models.DTOs;
using TrajetKmTracker.Api.Services.Exceptions;

namespace TrajetKmTracker.Api.Services;

/// <summary>
/// Client typé de l'API BAN. Appelle <c>GET /search/?q={query}&amp;limit=5</c>,
/// parse la réponse GeoJSON (FeatureCollection) et mappe les features en
/// <see cref="BANAdresseDto"/>. Lève <see cref="BANIndisponibleException"/>
/// en cas d'échec ou de timeout.
/// </summary>
public class BANClient : IBANClient
{
    private const int MaxResultats = 5;

    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNameCaseInsensitive = true
    };

    private readonly HttpClient _httpClient;

    public BANClient(HttpClient httpClient)
    {
        _httpClient = httpClient;
    }

    public async Task<IReadOnlyList<BANAdresseDto>> RechercherAsync(
        string query,
        CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(query))
        {
            return Array.Empty<BANAdresseDto>();
        }

        var requestUri = $"/search/?q={Uri.EscapeDataString(query)}&limit={MaxResultats}";

        BANFeatureCollection? collection;
        try
        {
            using var response = await _httpClient.GetAsync(requestUri, cancellationToken);
            response.EnsureSuccessStatusCode();

            collection = await response.Content.ReadFromJsonAsync<BANFeatureCollection>(
                JsonOptions, cancellationToken);
        }
        catch (OperationCanceledException) when (!cancellationToken.IsCancellationRequested)
        {
            // Le timeout configuré sur le HttpClient déclenche une annulation
            // non demandée par l'appelant.
            throw new BANIndisponibleException(
                "L'appel à l'API BAN a dépassé le délai imparti (timeout).");
        }
        catch (HttpRequestException ex)
        {
            throw new BANIndisponibleException(
                "L'API BAN est indisponible ou a renvoyé une réponse en erreur.", ex);
        }
        catch (JsonException ex)
        {
            throw new BANIndisponibleException(
                "La réponse de l'API BAN n'a pas pu être interprétée.", ex);
        }

        if (collection?.Features is null || collection.Features.Count == 0)
        {
            return Array.Empty<BANAdresseDto>();
        }

        var resultats = new List<BANAdresseDto>(collection.Features.Count);
        foreach (var feature in collection.Features)
        {
            var coordinates = feature.Geometry?.Coordinates;
            if (coordinates is null || coordinates.Count < 2)
            {
                continue;
            }

            // GeoJSON : coordinates = [longitude, latitude].
            var longitude = coordinates[0];
            var latitude = coordinates[1];

            resultats.Add(new BANAdresseDto(
                Label: feature.Properties?.Label ?? string.Empty,
                Latitude: latitude,
                Longitude: longitude,
                Postcode: feature.Properties?.Postcode ?? string.Empty,
                City: feature.Properties?.City ?? string.Empty));
        }

        return resultats;
    }

    // --- Modèles internes de désérialisation de la réponse GeoJSON BAN ---

    private sealed class BANFeatureCollection
    {
        [JsonPropertyName("features")]
        public List<BANFeature>? Features { get; set; }
    }

    private sealed class BANFeature
    {
        [JsonPropertyName("properties")]
        public BANProperties? Properties { get; set; }

        [JsonPropertyName("geometry")]
        public BANGeometry? Geometry { get; set; }
    }

    private sealed class BANProperties
    {
        [JsonPropertyName("label")]
        public string? Label { get; set; }

        [JsonPropertyName("postcode")]
        public string? Postcode { get; set; }

        [JsonPropertyName("city")]
        public string? City { get; set; }
    }

    private sealed class BANGeometry
    {
        // [longitude, latitude]
        [JsonPropertyName("coordinates")]
        public List<double>? Coordinates { get; set; }
    }
}