using AutoMapper;
using Mws.Application.Common;
using Mws.Domain.Tasks;
using TaskPriority = Mws.Domain.Tasks.TaskPriority;
using TaskStatus = Mws.Domain.Tasks.TaskStatus;

namespace Mws.Application.Tasks;

public class TaskService(IUnitOfWork uow, IMapper mapper) : ITaskService
{
    public async Task<List<TaskDto>> GetTasksAsync(Guid userId, Guid projectId, TaskStatus? status, TaskPriority? priority, Guid? assigneeId, CancellationToken ct = default)
    {
        await EnsureMemberAccessAsync(userId, projectId, ct);

        var tasks = await uow.Tasks.GetForProjectAsync(projectId, status, priority, assigneeId, ct);
        return mapper.Map<List<TaskDto>>(tasks);
    }

    public async Task<TaskDto> GetAsync(Guid userId, Guid taskId, CancellationToken ct = default)
    {
        var task = await GetTaskForUserAsync(userId, taskId, ct);
        return await GetDtoAsync(task.Id, ct);
    }

    public async Task<TaskDto> CreateAsync(Guid userId, Guid projectId, CreateTaskRequest request, CancellationToken ct = default)
    {
        await EnsureMemberAccessAsync(userId, projectId, ct);

        if (string.IsNullOrWhiteSpace(request.Title))
        {
            throw new BadRequestException("Task title is required");
        }

        if (request.AssigneeId.HasValue && !await IsMemberAsync(request.AssigneeId.Value, projectId, ct))
        {
            throw new BadRequestException("Assignee must be a member of the project");
        }

        var now = DateTime.UtcNow;
        var task = new TaskItem
        {
            Id = Guid.NewGuid(),
            ProjectId = projectId,
            Title = request.Title.Trim(),
            Description = request.Description,
            Status = request.Status ?? TaskStatus.Todo,
            Priority = request.Priority ?? TaskPriority.Medium,
            AssigneeId = request.AssigneeId,
            DueDate = request.DueDate,
            CreatedBy = userId,
            CreatedAt = now,
            UpdatedAt = now,
        };

        uow.Tasks.Add(task);
        await uow.SaveChangesAsync(ct);
        return await GetDtoAsync(task.Id, ct);
    }

    public async Task<TaskDto> UpdateAsync(Guid userId, Guid taskId, UpdateTaskRequest request, CancellationToken ct = default)
    {
        var task = await GetTaskForUserAsync(userId, taskId, ct);

        if (string.IsNullOrWhiteSpace(request.Title))
        {
            throw new BadRequestException("Task title is required");
        }

        if (request.AssigneeId.HasValue && !await IsMemberAsync(request.AssigneeId.Value, task.ProjectId, ct))
        {
            throw new BadRequestException("Assignee must be a member of the project");
        }

        task.Title = request.Title.Trim();
        task.Description = request.Description;
        task.Status = request.Status;
        task.Priority = request.Priority;
        task.AssigneeId = request.AssigneeId;
        task.DueDate = request.DueDate;
        task.UpdatedAt = DateTime.UtcNow;

        await uow.SaveChangesAsync(ct);
        return await GetDtoAsync(task.Id, ct);
    }

    public async Task DeleteAsync(Guid userId, Guid taskId, CancellationToken ct = default)
    {
        var task = await GetTaskForUserAsync(userId, taskId, ct);
        uow.Tasks.Remove(task);
        await uow.SaveChangesAsync(ct);
    }

    public async Task<List<TaskDto>> SearchAsync(Guid userId, string term, CancellationToken ct = default)
    {
        var projectIds = await uow.Projects.GetProjectIdsForUserAsync(userId, ct);
        var tasks = await uow.Tasks.SearchWithAssigneeAsync(projectIds, term, 20, ct);
        return mapper.Map<List<TaskDto>>(tasks);
    }

    private async Task<TaskDto> GetDtoAsync(Guid id, CancellationToken ct)
    {
        var task = await uow.Tasks.GetWithAssigneeAsync(id, ct)
            ?? throw new NotFoundException("Task not found");
        return mapper.Map<TaskDto>(task);
    }

    private async Task<TaskItem> GetTaskForUserAsync(Guid userId, Guid taskId, CancellationToken ct = default)
    {
        var task = await uow.Tasks.GetByIdAsync(taskId, ct)
            ?? throw new NotFoundException("Task not found");

        if (!await IsMemberAsync(userId, task.ProjectId, ct))
        {
            throw new NotFoundException("Task not found");
        }
        return task;
    }

    private async Task EnsureMemberAccessAsync(Guid userId, Guid projectId, CancellationToken ct = default)
    {
        if (!await IsMemberAsync(userId, projectId, ct))
        {
            throw new NotFoundException("Project not found");
        }
    }

    private Task<bool> IsMemberAsync(Guid userId, Guid projectId, CancellationToken ct = default) =>
        uow.Projects.IsMemberAsync(projectId, userId, ct);
}