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

namespace Jiaowu.Api.Controllers;

[ApiController]
[Authorize]
[Route("api/student-status-changes")]
public sealed class StudentStatusChangesController(
    AppDbContext db,
    ICurrentUserDataScope currentUserDataScope) : ControllerBase
{
    [HttpGet]
    public async Task<ActionResult> Get(CancellationToken token)
    {
        var source = ScopedChanges().AsNoTracking();
        return Ok(await source.OrderByDescending(x => x.SubmittedAt).Select(x => new
        {
            x.Id, x.StudentId, x.Student!.StudentNumber, x.Student.Name,
            ClassName = x.Student.AdministrativeClass!.Name,
            CollegeName = x.Student.AdministrativeClass.Major!.College!.Name,
            x.Type, x.OriginalStatus, x.TargetStatus, x.Reason, x.State,
            x.ReviewComment, x.SubmittedAt, x.ReviewedAt, x.ApprovedAt
        }).ToListAsync(token));
    }

    [HttpGet("options")]
    [Authorize(Roles = SystemRoles.Student)]
    public async Task<ActionResult> GetOptions(CancellationToken token)
    {
        var userId = currentUserDataScope.Current.UserId;
        var student = await db.Students.AsNoTracking()
            .FirstOrDefaultAsync(x => x.UserId == userId, token);
        if (student is null) return ConflictProblem("当前账号未关联学生档案。");

        var types = student.Status switch
        {
            StudentStatus.Active => new[]
            {
                StudentStatusChangeType.Suspension,
                StudentStatusChangeType.Withdrawal
            },
            StudentStatus.Suspended => new[]
            {
                StudentStatusChangeType.Resumption,
                StudentStatusChangeType.Withdrawal
            },
            _ => []
        };
        var hasPending = await db.StudentStatusChanges.AnyAsync(x =>
            x.StudentId == student.Id &&
            (x.State == StudentStatusChangeState.Submitted ||
             x.State == StudentStatusChangeState.CounselorApproved ||
             x.State == StudentStatusChangeState.CollegeApproved), token);
        return Ok(new { student.Status, Types = types, HasPending = hasPending });
    }

    [HttpPost]
    [Authorize(Roles = SystemRoles.Student)]
    public async Task<ActionResult> Create(
        StudentStatusChangeRequest request,
        CancellationToken token)
    {
        var userId = currentUserDataScope.Current.UserId;
        var student = await db.Students.FirstOrDefaultAsync(x => x.UserId == userId, token);
        if (student is null) return ConflictProblem("当前账号未关联学生档案。");
        var target = request.Type switch
        {
            StudentStatusChangeType.Suspension when student.Status == StudentStatus.Active =>
                StudentStatus.Suspended,
            StudentStatusChangeType.Resumption when student.Status == StudentStatus.Suspended =>
                StudentStatus.Active,
            StudentStatusChangeType.Withdrawal when student.Status is StudentStatus.Active or StudentStatus.Suspended =>
                StudentStatus.Withdrawn,
            _ => (StudentStatus?)null
        };
        if (!target.HasValue) return ConflictProblem("当前学籍状态不能申请该类异动。");
        if (await db.StudentStatusChanges.AnyAsync(x => x.StudentId == student.Id &&
                x.State != StudentStatusChangeState.Approved &&
                x.State != StudentStatusChangeState.Rejected &&
                x.State != StudentStatusChangeState.Cancelled, token))
            return ConflictProblem("已有一项学籍异动正在审核中。");
        var change = new StudentStatusChange
        {
            StudentId = student.Id, Type = request.Type,
            OriginalStatus = student.Status, TargetStatus = target.Value,
            Reason = request.Reason.Trim()
        };
        db.StudentStatusChanges.Add(change);
        await db.SaveChangesAsync(token);
        return Created(string.Empty, new { change.Id });
    }

    [HttpPost("{id:guid}/review")]
    public async Task<ActionResult> Review(
        Guid id,
        StudentStatusReviewRequest request,
        CancellationToken token)
    {
        var change = await ScopedChanges().Include(x => x.Student)
            .FirstOrDefaultAsync(x => x.Id == id, token);
        if (change is null) return NotFound();
        var scope = currentUserDataScope.Current;
        if (!CanReviewCurrentStage(scope, change.State))
            return ConflictProblem("当前角色或审核阶段不允许执行该操作。");

        if (!request.Approved)
        {
            if (string.IsNullOrWhiteSpace(request.Comment))
                return BadRequest(new ProblemDetails
                {
                    Title = "审核意见不完整",
                    Detail = "驳回申请时必须填写审核意见。",
                    Status = StatusCodes.Status400BadRequest
                });
            change.State = StudentStatusChangeState.Rejected;
        }
        else if (scope.IsInRole(SystemRoles.Counselor) &&
                 change.State == StudentStatusChangeState.Submitted)
            change.State = StudentStatusChangeState.CounselorApproved;
        else if (scope.IsInRole(SystemRoles.CollegeAdmin) &&
                 change.State == StudentStatusChangeState.CounselorApproved)
            change.State = StudentStatusChangeState.CollegeApproved;
        else if ((scope.IsInRole(SystemRoles.AcademicAdmin) ||
                  scope.IsInRole(SystemRoles.SuperAdmin)) &&
                 change.State == StudentStatusChangeState.CollegeApproved)
        {
            change.State = StudentStatusChangeState.Approved;
            change.Student!.Status = change.TargetStatus;
            change.ApprovedAt = DateTime.UtcNow;
        }
        else return ConflictProblem("当前角色或审核阶段不允许执行该操作。");

        change.ReviewComment = request.Comment?.Trim();
        change.ReviewedAt = DateTime.UtcNow;
        await db.SaveChangesAsync(token);
        return NoContent();
    }

    [HttpPost("{id:guid}/cancel")]
    [Authorize(Roles = SystemRoles.Student)]
    public async Task<ActionResult> Cancel(Guid id, CancellationToken token)
    {
        var userId = currentUserDataScope.Current.UserId;
        var change = await db.StudentStatusChanges.FirstOrDefaultAsync(
            x => x.Id == id && x.Student!.UserId == userId, token);
        if (change is null) return NotFound();
        if (change.State != StudentStatusChangeState.Submitted)
            return ConflictProblem("只有尚未进入审核的申请可以撤回。");

        change.State = StudentStatusChangeState.Cancelled;
        change.ReviewedAt = DateTime.UtcNow;
        await db.SaveChangesAsync(token);
        return NoContent();
    }

    private IQueryable<StudentStatusChange> ScopedChanges()
    {
        var scope = currentUserDataScope.Current;
        var source = db.StudentStatusChanges.AsQueryable();
        if (scope.IsInRole(SystemRoles.Student))
            return source.Where(x => x.Student!.UserId == scope.UserId);
        if (scope.IsInRole(SystemRoles.Counselor))
            return source.Where(x =>
                x.Student!.AdministrativeClass!.CounselorUserId == scope.UserId);
        if (scope.IsInRole(SystemRoles.CollegeAdmin))
            return source.Where(x =>
                x.Student!.AdministrativeClass!.Major!.CollegeId == scope.CollegeId);
        if (scope.IsInRole(SystemRoles.AcademicAdmin) ||
            scope.IsInRole(SystemRoles.SuperAdmin)) return source;
        return source.Where(_ => false);
    }

    private static bool CanReviewCurrentStage(
        CurrentUserScope scope,
        StudentStatusChangeState state) =>
        state switch
        {
            StudentStatusChangeState.Submitted =>
                scope.IsInRole(SystemRoles.Counselor),
            StudentStatusChangeState.CounselorApproved =>
                scope.IsInRole(SystemRoles.CollegeAdmin),
            StudentStatusChangeState.CollegeApproved =>
                scope.IsInRole(SystemRoles.AcademicAdmin) ||
                scope.IsInRole(SystemRoles.SuperAdmin),
            _ => false
        };

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

public sealed record StudentStatusChangeRequest(
    StudentStatusChangeType Type,
    [Required, MinLength(10), MaxLength(1000)] string Reason);

public sealed record StudentStatusReviewRequest(
    bool Approved,
    [MaxLength(500)] string? Comment);