using Microsoft.EntityFrameworkCore;
using Novelly.Api.Common;
using Novelly.Api.Data;
using Novelly.Api.Projects;
using Novelly.Api.Tags;

namespace Novelly.Api.Chapters;

public class ChapterService(INovelDbContext db, TagService tags)
{
    public async Task<IReadOnlyList<ChapterSummaryDto>> ListAsync(Guid projectId, CancellationToken ct = default)
    {
        var chapters = await db.Chapters
            .Include(c => c.PovCharacter)
            .Include(c => c.Beats)
            .Include(c => c.Scenes)
            .Include(c => c.Tags)
            .Where(c => c.ProjectId == projectId)
            .OrderBy(c => c.Number)
            .ToListAsync(ct);

        return [.. chapters.Select(c => c.ToSummaryDto())];
    }

    public async Task<ChapterDto> GetAsync(Guid id, CancellationToken ct = default) =>
        (await FindAsync(id, ct)).ToDto();

    public async Task<ChapterDto> CreateAsync(Guid projectId, CreateChapterRequest request, CancellationToken ct = default)
    {
        if (!await db.Projects.AnyAsync(p => p.Id == projectId, ct))
        {
            throw new NotFoundException(nameof(Project), projectId);
        }

        var chapter = new Chapter
        {
            ProjectId = projectId,
            Title = request.Title,
            Number = request.Number ?? await NextChapterNumberAsync(projectId, ct),
            Summary = request.Summary,
            PovCharacterId = request.PovCharacterId,
            Setting = request.Setting,
            Notes = request.Notes,
            Status = request.Status,
            TargetWordCount = request.TargetWordCount
        };

        if (request.Tags is { } names)
        {
            chapter.Tags = await tags.ResolveAsync(projectId, names, ct);
        }

        db.Chapters.Add(chapter);
        await db.SaveChangesAsync(ct);
        return (await FindAsync(chapter.Id, ct)).ToDto();
    }

    public async Task<ChapterDto> UpdateAsync(Guid id, UpdateChapterRequest request, CancellationToken ct = default)
    {
        var chapter = await FindAsync(id, ct);

        chapter.Title = Patch.Apply(chapter.Title, request.Title) ?? chapter.Title;
        chapter.Number = request.Number ?? chapter.Number;
        chapter.Summary = Patch.Apply(chapter.Summary, request.Summary);
        chapter.PovCharacterId = request.PovCharacterId ?? chapter.PovCharacterId;
        chapter.Setting = Patch.Apply(chapter.Setting, request.Setting);
        chapter.Notes = Patch.Apply(chapter.Notes, request.Notes);
        chapter.Status = request.Status ?? chapter.Status;
        chapter.TargetWordCount = request.TargetWordCount ?? chapter.TargetWordCount;
        chapter.UpdatedAt = DateTimeOffset.UtcNow;

        if (request.Tags is { } names)
        {
            chapter.Tags = await tags.ResolveAsync(chapter.ProjectId, names, ct);
        }

        await db.SaveChangesAsync(ct);
        return (await FindAsync(id, ct)).ToDto();
    }

    public async Task DeleteAsync(Guid id, CancellationToken ct = default)
    {
        var chapter = await FindAsync(id, ct);
        db.Chapters.Remove(chapter);
        await db.SaveChangesAsync(ct);
    }

    private async Task<int> NextChapterNumberAsync(Guid projectId, CancellationToken ct)
    {
        var max = await db.Chapters
            .Where(c => c.ProjectId == projectId)
            .MaxAsync(c => (int?)c.Number, ct);

        return (max ?? 0) + 1;
    }

    private async Task<Chapter> FindAsync(Guid id, CancellationToken ct) =>
        await db.Chapters
            .Include(c => c.PovCharacter)
            .Include(c => c.Beats).ThenInclude(b => b.Character)
            .Include(c => c.Beats).ThenInclude(b => b.Scene)
            .Include(c => c.Beats).ThenInclude(b => b.Tags)
            .Include(c => c.Scenes).ThenInclude(s => s.PovCharacter)
            .Include(c => c.Tags)
            .FirstOrDefaultAsync(c => c.Id == id, ct)
        ?? throw new NotFoundException(nameof(Chapter), id);
}