using System.Net.Mail;
using System.Security.Claims;
using Data.SeaHavenIndustries;
using Data.SeaHavenIndustries.Enums;
using Microsoft.AspNetCore.Identity;
using Microsoft.EntityFrameworkCore;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.Services.Constants;
using SeaHaven.Services.DTOs;
using SeaHaven.Services.Interfaces;

namespace SeaHaven.Services.Implementation;

public sealed class TeamMemberService : ITeamMemberService
{
    private const string ActiveStatus = "Active";
    private readonly UserManager<ApplicationUser> _userManager;
    private readonly RoleManager<IdentityRole> _roleManager;
    private readonly IUserServiceAreaDataService _areaDataService;
    private readonly ITeamPermissionOverrideDataService _permissionDataService;
    private readonly IUserDataService _userDataService;
    private readonly ITeamPermissionService _permissionService;

    public TeamMemberService(
        UserManager<ApplicationUser> userManager,
        RoleManager<IdentityRole> roleManager,
        IUserServiceAreaDataService areaDataService,
        ITeamPermissionOverrideDataService permissionDataService,
        IUserDataService userDataService,
        ITeamPermissionService permissionService)
    {
        _userManager = userManager;
        _roleManager = roleManager;
        _areaDataService = areaDataService;
        _permissionDataService = permissionDataService;
        _userDataService = userDataService;
        _permissionService = permissionService;
    }

    public async Task<CreateTeamMemberOutcomeDTO> CreateAsync(
        CreateTeamMemberRequestDTO request,
        ClaimsPrincipal caller,
        CancellationToken cancellationToken)
    {
        if (caller?.IsInRole("Admin") != true)
            return Failure("Forbidden");

        var validation = Validate(request, out var role, out var color, out var email, out var areas, out var overrides);
        if (validation is not null)
            return Failure(validation);

        if (await _userManager.FindByEmailAsync(email!) is not null)
            return Failure("Email is already in use.");

        var now = DateTime.UtcNow;
        var user = new ApplicationUser
        {
            UserName = email,
            Email = email,
            EmailConfirmed = false,
            FirstName = request.Name!.Trim(),
            Contact = request.Phone?.Trim(),
            PhoneNumber = request.Phone?.Trim(),
            Color = color,
            UniqueName = ActiveStatus,
            CreatedDate = now,
            PendingRegistration = true,
            PendingRegistrationCreatedDate = now
        };

        try
        {
            await _userDataService.ExecuteTransactionalAsync(
                async transactionCancellationToken =>
                {
                    var roleError = await EnsureRoleAsync(role!);
                    if (roleError is not null)
                        throw new TeamMemberCreateException(roleError);

                    IdentityResult createResult;
                    try
                    {
                        createResult = await _userManager.CreateAsync(user);
                    }
                    catch (DbUpdateException)
                    {
                        // A concurrent create won the race on the unique user-name index
                        // between the FindByEmailAsync check above and this insert. Surface
                        // the same conflict message instead of letting the database
                        // exception bubble up as a 500.
                        throw new TeamMemberCreateException("Email is already in use.");
                    }

                    if (!createResult.Succeeded)
                        throw new TeamMemberCreateException(createResult.Errors.FirstOrDefault()?.Description ?? "Unable to create team member.");

                    var addRoleResult = await _userManager.AddToRoleAsync(user, role!);
                    if (!addRoleResult.Succeeded)
                        throw new TeamMemberCreateException(addRoleResult.Errors.FirstOrDefault()?.Description ?? "Unable to assign role.");

                    await _areaDataService.ReplaceAsync(user.Id, areas!, transactionCancellationToken);
                    await _permissionDataService.SetOverridesAsync(user.Id, overrides!, transactionCancellationToken);
                },
                cancellationToken);
        }
        catch (TeamMemberCreateException exception)
        {
            return Failure(exception.Message);
        }

        return new CreateTeamMemberOutcomeDTO
        {
            Success = true,
            Member = new TeamMemberCreatedDTO
            {
                Id = user.Id,
                Name = user.FirstName!,
                Role = role!,
                Color = color!,
                Email = user.Email,
                Phone = user.PhoneNumber,
                ServiceAreas = areas!,
                PendingRegistration = true
            }
        };
    }

    public async Task<TeamMemberOperationOutcomeDTO> GetAsync(
        string userId,
        ClaimsPrincipal caller,
        CancellationToken cancellationToken)
    {
        if (caller?.IsInRole("Admin") != true)
            return OperationFailure("Forbidden");

        var user = await _userManager.FindByIdAsync(userId);
        if (user is null)
            return OperationFailure("Team member not found.");

        return await OperationSuccessAsync(user, caller, cancellationToken);
    }

    public async Task<TeamMemberOperationOutcomeDTO> UpdateAsync(
        string userId,
        UpdateTeamMemberRequestDTO request,
        ClaimsPrincipal caller,
        CancellationToken cancellationToken)
    {
        if (caller?.IsInRole("Admin") != true)
            return OperationFailure("Forbidden");

        var user = await _userManager.FindByIdAsync(userId);
        if (user is null)
            return OperationFailure("Team member not found.");

        var existingRoles = await _userManager.GetRolesAsync(user);
        var existingRole = existingRoles.FirstOrDefault();
        var candidate = new CreateTeamMemberRequestDTO
        {
            Name = request.Name,
            Role = request.Role,
            Color = request.Color,
            Email = request.Email,
            Phone = request.Phone,
            ServiceAreas = request.ServiceAreas,
            PermissionOverrides = request.PermissionOverrides
        };
        var validation = Validate(candidate, out var role, out var color, out var email, out var areas, out var overrides);
        if (validation is not null)
            return OperationFailure(validation);

        var roleChanged = !string.Equals(existingRole, role, StringComparison.OrdinalIgnoreCase);
        var isOwner = await _userDataService.IsAccountOwnerAsync(user.Id, cancellationToken);
        if (isOwner && (roleChanged || !request.IsActive))
            return OperationFailure("Forbidden");

        var duplicate = await _userManager.FindByEmailAsync(email!);
        if (duplicate is not null && !string.Equals(duplicate.Id, user.Id, StringComparison.Ordinal))
            return OperationFailure("Email is already in use.");

        var roleError = await EnsureRoleAsync(role!);
        if (roleError is not null)
            return OperationFailure(roleError);

        ApplyName(user, candidate.Name!.Trim());
        user.Contact = candidate.Phone?.Trim();
        user.PhoneNumber = candidate.Phone?.Trim();
        user.Color = color;
        user.UniqueName = request.IsActive ? ActiveStatus : "Inactive";
        user.IsDeleted = !request.IsActive;

        if (!string.Equals(user.Email, email, StringComparison.OrdinalIgnoreCase))
        {
            var emailResult = await _userManager.SetEmailAsync(user, email!);
            if (!emailResult.Succeeded)
                return OperationFailure(emailResult.Errors.FirstOrDefault()?.Description ?? "Unable to update email.");

            var userNameResult = await _userManager.SetUserNameAsync(user, email!);
            if (!userNameResult.Succeeded)
                return OperationFailure(userNameResult.Errors.FirstOrDefault()?.Description ?? "Unable to update email.");

            var securityStampResult = await _userManager.UpdateSecurityStampAsync(user);
            if (!securityStampResult.Succeeded)
                return OperationFailure(securityStampResult.Errors.FirstOrDefault()?.Description ?? "Unable to update email.");
        }

        if (roleChanged)
        {
            if (existingRoles.Count > 0)
            {
                var removeRoleResult = await _userManager.RemoveFromRolesAsync(user, existingRoles);
                if (!removeRoleResult.Succeeded)
                    return OperationFailure(removeRoleResult.Errors.FirstOrDefault()?.Description ?? "Unable to update role.");
            }

            var addRoleResult = await _userManager.AddToRoleAsync(user, role!);
            if (!addRoleResult.Succeeded)
                return OperationFailure(addRoleResult.Errors.FirstOrDefault()?.Description ?? "Unable to update role.");
        }

        await _userDataService.UpdateUserAsync(user, cancellationToken);
        await _areaDataService.ReplaceAsync(user.Id, areas!, cancellationToken);
        if (roleChanged || request.PermissionOverrides is not null)
        {
            await _permissionDataService.ClearOverridesAsync(user.Id, cancellationToken);
            if (request.PermissionOverrides is not null)
                await _permissionDataService.SetOverridesAsync(user.Id, overrides!, cancellationToken);
        }

        return await OperationSuccessAsync(user, caller, cancellationToken);
    }

    private static void ApplyName(ApplicationUser user, string fullName)
    {
        var current = $"{user.FirstName ?? ""} {user.LastName ?? ""}".Trim();
        if (string.Equals(fullName, current, StringComparison.Ordinal))
            return;

        var separator = fullName.IndexOf(' ');
        if (separator < 0)
        {
            user.FirstName = fullName;
            user.LastName = null;
            return;
        }

        user.FirstName = fullName[..separator].Trim();
        user.LastName = fullName[(separator + 1)..].Trim();
    }

    private async Task<string?> EnsureRoleAsync(string role)
    {
        if (await _roleManager.RoleExistsAsync(role))
            return null;

        var roleResult = await _roleManager.CreateAsync(new IdentityRole(role));
        return roleResult.Succeeded
            ? null
            : roleResult.Errors.FirstOrDefault()?.Description ?? "Unable to create role.";
    }

    private async Task<TeamMemberOperationOutcomeDTO> OperationSuccessAsync(
        ApplicationUser user,
        ClaimsPrincipal caller,
        CancellationToken cancellationToken)
    {
        var roles = await _userManager.GetRolesAsync(user);
        var profile = await _permissionService.GetProfileAsync(user.Id, caller, cancellationToken);
        var areas = await _areaDataService.GetForUserAsync(user.Id, cancellationToken);
        return new TeamMemberOperationOutcomeDTO
        {
            Success = true,
            Member = new TeamMemberDetailDTO
            {
                Id = user.Id,
                Name = $"{user.FirstName ?? ""} {user.LastName ?? ""}".Trim(),
                Role = TeamMemberConstants.CanonicalRole(roles.FirstOrDefault()) ?? roles.FirstOrDefault() ?? "",
                Color = user.Color ?? "",
                Email = user.Email,
                Phone = user.Contact ?? user.PhoneNumber,
                ServiceAreas = areas,
                PendingRegistration = user.PendingRegistration == true,
                Status = user.UniqueName ?? "Active",
                IsAccountOwner = user.IsAccountOwner,
                Permissions = profile?.Value?.Permissions ?? Array.Empty<TeamPermissionValueDTO>()
            }
        };
    }

    private static string? Validate(
        CreateTeamMemberRequestDTO request,
        out string? role,
        out string? color,
        out string? email,
        out IReadOnlyList<string>? areas,
        out IReadOnlyDictionary<string, UserPermissionState>? overrides)
    {
        role = TeamMemberConstants.CanonicalRole(request.Role);
        color = request.Color?.Trim();
        email = request.Email?.Trim();
        areas = NormalizeAreas(request.ServiceAreas, out var invalidArea);
        overrides = NormalizeOverrides(request.PermissionOverrides, out var invalidPermission);

        if (string.IsNullOrWhiteSpace(request.Name))
            return "Name is required.";
        if (role is null)
            return "Role must be Dispatcher, Scheduler, or Admin.";
        if (color is null || !TeamMemberConstants.Colors.Contains(color))
            return "Color must be selected from the accessible palette.";
        if (!IsValidEmail(email))
            return "A valid email is required.";
        if (invalidArea is not null)
            return $"Unknown service area: {invalidArea}.";
        if (string.Equals(role, "Dispatcher", StringComparison.Ordinal)
            && (areas is null || areas.Count == 0))
            return "At least one service area is required for a Dispatcher.";
        if (!string.Equals(role, "Dispatcher", StringComparison.Ordinal)
            && areas is { Count: > 0 })
            return "Service areas are only available for Dispatchers.";
        if (invalidPermission is not null)
            return $"Unknown permission key: {invalidPermission}.";

        return null;
    }

    private static IReadOnlyList<string> NormalizeAreas(
        IReadOnlyList<string>? values,
        out string? invalidArea)
    {
        invalidArea = null;
        var normalized = new List<string>();
        foreach (var value in values ?? Array.Empty<string>())
        {
            var canonical = TeamMemberConstants.CanonicalArea(value);
            if (canonical is null)
            {
                invalidArea = value;
                return Array.Empty<string>();
            }

            if (!normalized.Contains(canonical, StringComparer.Ordinal))
                normalized.Add(canonical);
        }

        return normalized;
    }

    private static IReadOnlyDictionary<string, UserPermissionState> NormalizeOverrides(
        IReadOnlyDictionary<string, UserPermissionState>? values,
        out string? invalidPermission)
    {
        invalidPermission = null;
        var normalized = new Dictionary<string, UserPermissionState>(StringComparer.OrdinalIgnoreCase);
        foreach (var pair in values ?? new Dictionary<string, UserPermissionState>())
        {
            var canonical = TeamPermissionKeys.All.FirstOrDefault(key =>
                string.Equals(key, pair.Key, StringComparison.OrdinalIgnoreCase));
            if (canonical is null)
            {
                invalidPermission = pair.Key;
                return new Dictionary<string, UserPermissionState>();
            }

            if (!Enum.IsDefined(pair.Value))
            {
                invalidPermission = pair.Key;
                return new Dictionary<string, UserPermissionState>();
            }

            normalized[canonical] = pair.Value;
        }

        return normalized;
    }

    private static bool IsValidEmail(string? value)
    {
        if (string.IsNullOrWhiteSpace(value))
            return false;

        try
        {
            var address = new MailAddress(value);
            return string.Equals(address.Address, value, StringComparison.OrdinalIgnoreCase);
        }
        catch (FormatException)
        {
            return false;
        }
    }

    private static CreateTeamMemberOutcomeDTO Failure(string error) =>
        new() { Success = false, Error = error };

    private sealed class TeamMemberCreateException : Exception
    {
        public TeamMemberCreateException(string error) : base(error)
        {
        }
    }

    private static TeamMemberOperationOutcomeDTO OperationFailure(string error) =>
        new() { Success = false, Error = error };
}