using Data.SeaHavenIndustries;
using Data.SeaHavenIndustries.Enums;
using Microsoft.EntityFrameworkCore;
using SeaHaven.DataServices.Dto;
using SeaHaven.DataServices.Interfaces;

namespace SeaHaven.DataServices.Implementation;

public sealed class TeamPermissionOverrideDataService : ITeamPermissionOverrideDataService
{
    private readonly ApplicationDbContext _context;

    public TeamPermissionOverrideDataService(ApplicationDbContext context)
    {
        _context = context;
    }

    public async Task<TeamPermissionUserData?> GetUserAsync(
        string userId,
        CancellationToken cancellationToken)
    {
        var userExists = await _context.Users
            .AsNoTracking()
            .AnyAsync(user => user.Id == userId, cancellationToken);

        if (!userExists)
            return null;

        var roleName = await (
            from userRole in _context.UserRoles.AsNoTracking()
            join role in _context.Roles.AsNoTracking()
                on userRole.RoleId equals role.Id
            where userRole.UserId == userId
            select role.Name)
            .FirstOrDefaultAsync(cancellationToken);

        var overrides = await _context.UserPermissionOverrides
            .AsNoTracking()
            .Where(permission => permission.UserId == userId)
            .ToDictionaryAsync(
                permission => permission.PermissionKey,
                permission => permission.State,
                StringComparer.OrdinalIgnoreCase,
                cancellationToken);

        return new TeamPermissionUserData
        {
            UserId = userId,
            RoleName = roleName,
            Overrides = overrides
        };
    }

    public Task SetOverrideAsync(
        string userId,
        string permissionKey,
        UserPermissionState state,
        CancellationToken cancellationToken)
    {
        return SetOverrideCoreAsync(userId, permissionKey, state, cancellationToken);
    }

    public async Task SetOverridesAsync(
        string userId,
        IReadOnlyDictionary<string, UserPermissionState> overrides,
        CancellationToken cancellationToken)
    {
        foreach (var pair in overrides)
            await SetOverrideCoreAsync(userId, pair.Key, pair.Value, cancellationToken);
    }

    private async Task SetOverrideCoreAsync(
        string userId,
        string permissionKey,
        UserPermissionState state,
        CancellationToken cancellationToken)
    {
        var existing = await _context.UserPermissionOverrides
            .SingleOrDefaultAsync(
                permission => permission.UserId == userId
                    && permission.PermissionKey == permissionKey,
                cancellationToken);

        if (existing is not null)
        {
            existing.State = state;
            await _context.SaveChangesAsync(cancellationToken);
            return;
        }

        var addition = new UserPermissionOverride
        {
            UserId = userId,
            PermissionKey = permissionKey,
            State = state
        };
        await _context.UserPermissionOverrides.AddAsync(addition, cancellationToken);

        try
        {
            await _context.SaveChangesAsync(cancellationToken);
        }
        catch (DbUpdateException)
        {
            // A concurrent write (create or PUT) inserted the same composite key
            // between our existence check and this save. Converge on the caller's intent.
            _context.Entry(addition).State = EntityState.Detached;
            var winner = await _context.UserPermissionOverrides
                .SingleAsync(
                    permission => permission.UserId == userId
                        && permission.PermissionKey == permissionKey,
                    cancellationToken);
            winner.State = state;
            await _context.SaveChangesAsync(cancellationToken);
        }
    }

    public async Task ClearOverridesAsync(string userId, CancellationToken cancellationToken)
    {
        await _context.UserPermissionOverrides
            .Where(item => item.UserId == userId)
            .ExecuteDeleteAsync(cancellationToken);
    }
}