using System.Net.Http.Headers;
using System.Text.Json;
using JobTrackerApi.Models;
using Microsoft.Extensions.Caching.Memory;

namespace JobTrackerApi.Services;

public interface IJobDiscoverySearchService
{
    Task<IReadOnlyList<DiscoveredJob>> SearchAsync(string? query, string? location, CancellationToken cancellationToken);
}

public sealed class NavJobDiscoverySearchService(
    IHttpClientFactory clients,
    IConfiguration configuration,
    IMemoryCache cache,
    TimeProvider timeProvider) : IJobDiscoverySearchService
{
    private const string BaseUrl = "https://pam-stilling-feed.nav.no";

    public async Task<IReadOnlyList<DiscoveredJob>> SearchAsync(string? query, string? location, CancellationToken cancellationToken)
    {
        var retrievedAt = timeProvider.GetUtcNow();
        var token = await GetTokenAsync(cancellationToken);
        var client = clients.CreateClient();
        var entries = new Dictionary<string, DiscoveredJob>(StringComparer.OrdinalIgnoreCase);
        var next = "/api/v1/feed";
        for (var page = 0; page < 20 && !string.IsNullOrWhiteSpace(next); page++)
        {
            using var request = new HttpRequestMessage(HttpMethod.Get, BaseUrl + next);
            request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
            request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
            if (page == 0) request.Headers.IfModifiedSince = timeProvider.GetUtcNow().AddDays(-14);
            using var response = await client.SendAsync(request, cancellationToken);
            response.EnsureSuccessStatusCode();
            using var json = JsonDocument.Parse(await response.Content.ReadAsStreamAsync(cancellationToken));
            next = json.RootElement.TryGetProperty("next_url", out var nextElement) ? nextElement.GetString() ?? "" : "";
            foreach (var item in json.RootElement.GetProperty("items").EnumerateArray())
            {
                var feed = item.GetProperty("_feed_entry");
                var jobId = feed.GetProperty("uuid").GetString();
                if (string.IsNullOrWhiteSpace(jobId)) continue;
                var status = feed.TryGetProperty("status", out var statusElement) ? statusElement.GetString() : null;
                if (!string.Equals(status, "ACTIVE", StringComparison.OrdinalIgnoreCase)) { entries.Remove(jobId); continue; }
                entries[jobId] = new DiscoveredJob(jobId,
                    feed.TryGetProperty("title", out var title) ? title.GetString() ?? "" : "",
                    feed.TryGetProperty("businessName", out var company) ? company.GetString() : null,
                    feed.TryGetProperty("municipal", out var municipal) ? municipal.GetString() : null,
                    item.TryGetProperty("date_modified", out var modified) && modified.TryGetDateTimeOffset(out var date) ? date : null,
                    feed.TryGetProperty("applicationDue", out var due) && due.TryGetDateTimeOffset(out var deadline) ? deadline : null,
                    $"https://arbeidsplassen.nav.no/stillinger/stilling/{jobId}", "nav", "NAV Arbeidsplassen", "searched", retrievedAt, "NO");
            }
        }

        var term = (query ?? "").Trim();
        var place = (location ?? "").Trim();
        return entries.Values.Where(job => Contains(job.Title, term) || Contains(job.Company, term))
            .Where(job => Contains(job.Location, place)).OrderByDescending(job => job.ModifiedAt).Take(100).ToList();
    }

    private async Task<string> GetTokenAsync(CancellationToken cancellationToken)
    {
        var configured = configuration["NavJobs:Token"]?.Trim();
        if (!string.IsNullOrWhiteSpace(configured)) return configured;

        return await cache.GetOrCreateAsync("nav-jobs-public-token", async entry =>
        {
            entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(30);
            var text = await clients.CreateClient().GetStringAsync(BaseUrl + "/api/publicToken", cancellationToken);
            var start = text.IndexOf("eyJ", StringComparison.Ordinal);
            if (start < 0) throw new InvalidOperationException("NAV public token was not returned.");
            var token = text[start..].Trim();
            var end = token.IndexOfAny(['\r', '\n', ' ', '\t']);
            return end < 0 ? token : token[..end];
        }) ?? throw new InvalidOperationException("NAV public token was not returned.");
    }

    private static bool Contains(string? value, string filter) =>
        filter.Length == 0 || (value?.Contains(filter, StringComparison.OrdinalIgnoreCase) ?? false);
}