using System.ComponentModel.DataAnnotations;
using Jiaowu.Api.Domain.Academic;
using Jiaowu.Api.Domain.Identity;
using Jiaowu.Api.Infrastructure.Persistence;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;

namespace Jiaowu.Api.Controllers;

[ApiController]
[Authorize(Roles = ReadRoles)]
[Route("api/course-groups")]
public sealed class CourseGroupsController(AppDbContext db) : ControllerBase
{
    private const string ReadRoles =
        SystemRoles.SuperAdmin + "," +
        SystemRoles.AcademicAdmin + "," +
        SystemRoles.CollegeAdmin;
    private const string ManageRoles =
        SystemRoles.SuperAdmin + "," +
        SystemRoles.AcademicAdmin;

    [HttpGet]
    public async Task<ActionResult> GetAll(CancellationToken cancellationToken)
    {
        var groups = await db.CourseGroups.AsNoTracking()
            .OrderBy(x => x.Code)
            .Select(x => new
            {
                x.Id,
                x.Code,
                x.Name,
                x.Description,
                CourseCount = x.Courses.Count,
                Courses = x.Courses.OrderBy(item => item.Course!.Code).Select(item => new
                {
                    item.Id,
                    item.CourseId,
                    CourseCode = item.Course!.Code,
                    CourseName = item.Course.Name,
                    item.Course.Credits,
                    item.Course.TotalHours,
                    item.Course.Nature
                })
            })
            .ToListAsync(cancellationToken);
        return Ok(groups);
    }

    [HttpPost]
    [Authorize(Roles = ManageRoles)]
    public async Task<ActionResult> Create(
        CourseGroupRequest request,
        CancellationToken cancellationToken)
    {
        var group = new CourseGroup
        {
            Code = request.Code.Trim(),
            Name = request.Name.Trim(),
            Description = Normalize(request.Description)
        };
        db.CourseGroups.Add(group);
        return await SaveCreatedAsync(group.Id, cancellationToken);
    }

    [HttpPut("{id:guid}")]
    [Authorize(Roles = ManageRoles)]
    public async Task<ActionResult> Update(
        Guid id,
        CourseGroupRequest request,
        CancellationToken cancellationToken)
    {
        var group = await db.CourseGroups.FirstOrDefaultAsync(x => x.Id == id, cancellationToken);
        if (group is null) return NotFound();
        group.Code = request.Code.Trim();
        group.Name = request.Name.Trim();
        group.Description = Normalize(request.Description);
        return await SaveNoContentAsync(cancellationToken);
    }

    [HttpDelete("{id:guid}")]
    [Authorize(Roles = ManageRoles)]
    public async Task<ActionResult> Delete(Guid id, CancellationToken cancellationToken)
    {
        var group = await db.CourseGroups.FirstOrDefaultAsync(x => x.Id == id, cancellationToken);
        if (group is null) return NotFound();
        db.CourseGroups.Remove(group);
        return await SaveNoContentAsync(cancellationToken);
    }

    [HttpPost("{id:guid}/courses")]
    [Authorize(Roles = ManageRoles)]
    public async Task<ActionResult> AddCourse(
        Guid id,
        CourseGroupCourseRequest request,
        CancellationToken cancellationToken)
    {
        if (!await db.CourseGroups.AnyAsync(x => x.Id == id, cancellationToken)) return NotFound();
        if (!await db.Courses.AnyAsync(x => x.Id == request.CourseId && x.IsEnabled, cancellationToken))
            return ValidationProblem("所选课程不存在或已停用。");
        db.CourseGroupCourses.Add(new CourseGroupCourse { CourseGroupId = id, CourseId = request.CourseId });
        return await SaveCreatedAsync(id, cancellationToken);
    }

    [HttpDelete("{id:guid}/courses/{courseId:guid}")]
    [Authorize(Roles = ManageRoles)]
    public async Task<ActionResult> RemoveCourse(
        Guid id,
        Guid courseId,
        CancellationToken cancellationToken)
    {
        var item = await db.CourseGroupCourses.FirstOrDefaultAsync(
            x => x.CourseGroupId == id && x.CourseId == courseId,
            cancellationToken);
        if (item is null) return NotFound();
        db.CourseGroupCourses.Remove(item);
        return await SaveNoContentAsync(cancellationToken);
    }

    private async Task<ActionResult> SaveCreatedAsync(Guid id, CancellationToken cancellationToken)
    {
        try
        {
            await db.SaveChangesAsync(cancellationToken);
            return Created(string.Empty, new { id });
        }
        catch (DbUpdateException)
        {
            return ConflictProblem("课程组编码或组内课程重复。");
        }
    }

    private async Task<ActionResult> SaveNoContentAsync(CancellationToken cancellationToken)
    {
        try
        {
            await db.SaveChangesAsync(cancellationToken);
            return NoContent();
        }
        catch (DbUpdateException)
        {
            return ConflictProblem("课程组编码或组内课程重复。");
        }
    }

    private ActionResult ConflictProblem(string detail) => Conflict(new ProblemDetails
    {
        Title = "无法完成操作", Detail = detail, Status = StatusCodes.Status409Conflict
    });

    private static string? Normalize(string? value) =>
        string.IsNullOrWhiteSpace(value) ? null : value.Trim();
}

public sealed record CourseGroupRequest(
    [Required, MaxLength(30)] string Code,
    [Required, MaxLength(100)] string Name,
    [MaxLength(500)] string? Description);

public sealed record CourseGroupCourseRequest(Guid CourseId);