using Core.Models;
using Core.Services;

namespace WebApp.Services;

/// <summary>
/// Creates or updates #Student:{id} notes when imported fields actually change.
/// </summary>
public class StudentNotesImportSaveService : IStudentNotesImportSaveService
{
    private readonly INotesService _notesService;
    private readonly INoteNamingService _noteNamingService;
    private readonly ILogger<StudentNotesImportSaveService> _logger;

    public StudentNotesImportSaveService(
        INotesService notesService,
        INoteNamingService noteNamingService,
        ILogger<StudentNotesImportSaveService> logger)
    {
        _notesService = notesService;
        _noteNamingService = noteNamingService;
        _logger = logger;
    }

    /// <inheritdoc />
    public async Task<StudentNotesImportSaveResult> SaveAsync(
        StudentNotesImportResult parseResult,
        CancellationToken cancellationToken = default)
    {
        var result = new StudentNotesImportSaveResult();
        var existingNotes = await _notesService.GetStudentNotesAsync(
            parseResult.Matches.Select(m => m.Student.Id));
        var actions = StudentNotesImportPlan.Create(parseResult, existingNotes.Keys.ToHashSet());
        result.StudentsUnchanged = parseResult.Matches.Count - actions.Count;

        foreach (var action in actions)
        {
            cancellationToken.ThrowIfCancellationRequested();
            if (action.Kind == StudentNotePersistKind.Update
                && existingNotes.TryGetValue(action.StudentId, out var existing))
            {
                existing.Content = action.Markdown;
                await _notesService.UpdateNoteAsync(existing);
                result.NotesUpdated++;
                continue;
            }

            await _notesService.CreateNoteAsync(new Core.Entities.Note
            {
                Title = _noteNamingService.GetStudentNoteTitle(action.StudentId),
                Content = action.Markdown
            });
            result.NotesCreated++;
        }

        _logger.LogInformation(
            "Student notes import saved. Created={Created}, Updated={Updated}, Unchanged={Unchanged}",
            result.NotesCreated,
            result.NotesUpdated,
            result.StudentsUnchanged);

        return result;
    }
}