using eprintServer.Data;
using eprintServer.Entities;
using eprintServer.Requests;
using Microsoft.EntityFrameworkCore;

namespace eprintServer.Services;

public class ContactService
{
    private readonly DataContext _context;

    // Cache to hold the single instance ID in memory after the first load
    private static int? _uniqueContactId = null;

    public ContactService(DataContext context)
    {
        _context = context;
    }

    /// <summary>
    /// Ensures a single instance of ContactSettings exists and retrieves it,
    /// creating a default one if none is found.
    /// </summary>
    public async Task<ContactSettings> GetOrInitializeContactSettingsAsync()
    {
        ContactSettings? settings;

        // 1. Try to load by cached ID
        if (_uniqueContactId.HasValue)
        {
            settings = await _context.ContactSettings.FirstOrDefaultAsync(c => c.Id == _uniqueContactId.Value);

            if (settings != null)
            {
                return settings;
            }
        }

        // 2. If not found, perform a full search
        settings = await _context.ContactSettings.FirstOrDefaultAsync();

        if (settings == null)
        {
            // 3. Create a new instance with empty defaults and save it
            settings = new ContactSettings
            {
                Email = string.Empty,
                Phone = string.Empty,
                Address = string.Empty,
                MapUrl = string.Empty,
                WorkingHours = string.Empty,
                EmailRecipients = new List<string>()
            };
            _context.ContactSettings.Add(settings);
            await _context.SaveChangesAsync();
        }

        // 4. Cache the ID
        _uniqueContactId = settings.Id;

        return settings;
    }

    /// <summary>
    /// Updates the existing unique ContactSettings instance, 
    /// only applying updates for non-null properties in the request.
    /// </summary>
    public async Task<ContactSettings> UpdateContactInfoAsync(UpdateContactInfoRequest request)
    {
        var settings = await GetOrInitializeContactSettingsAsync();

        bool changed = false;

        // Apply conditional updates: update only if the request property is not null
        if (request.Email != null)
        {
            settings.Email = request.Email;
            changed = true;
        }
        if (request.Phone != null)
        {
            settings.Phone = request.Phone;
            changed = true;
        }
        if (request.Address != null)
        {
            settings.Address = request.Address;
            changed = true;
        }
        if (request.MapUrl != null)
        {
            settings.MapUrl = request.MapUrl;
            changed = true;
        }
        if (request.WorkingHours != null)
        {
            settings.WorkingHours = request.WorkingHours;
            changed = true;
        }

        if (changed)
        {
            settings.UpdatedAt = DateTime.UtcNow;
            _context.ContactSettings.Update(settings);
            await _context.SaveChangesAsync();
        }

        return settings;
    }
    
    /// <summary>
    /// Adds a unique email to the recipient list.
    /// </summary>
    public async Task<ContactSettings> AddEmailRecipientAsync(string email)
    {
        var settings = await GetOrInitializeContactSettingsAsync();

        // Check if email is already present (case-insensitive)
        if (!settings.EmailRecipients.Any(e => e.Equals(email, StringComparison.OrdinalIgnoreCase)))
        {
            settings.EmailRecipients.Add(email);
            settings.UpdatedAt = DateTime.UtcNow;
            _context.ContactSettings.Update(settings);
            await _context.SaveChangesAsync();
        }

        return settings;
    }

    /// <summary>
    /// Removes an email from the recipient list.
    /// </summary>
    public async Task<ContactSettings> RemoveEmailRecipientAsync(string email)
    {
        var settings = await GetOrInitializeContactSettingsAsync();
        
        // Remove the email (case-insensitive)
        int initialCount = settings.EmailRecipients.Count;
        settings.EmailRecipients.RemoveAll(e => e.Equals(email, StringComparison.OrdinalIgnoreCase));

        if (settings.EmailRecipients.Count != initialCount)
        {
            settings.UpdatedAt = DateTime.UtcNow;
            _context.ContactSettings.Update(settings);
            await _context.SaveChangesAsync();
        }

        return settings;
    }
}