using Microsoft.EntityFrameworkCore;
using Novelly.Api.Common;
using Novelly.Api.Common.Validation;
using Novelly.Api.Data;
using Novelly.Api.Users;

namespace Novelly.Api.Novels;

public class NovelService(
    INovelDbContext db,
    NovelAccessService access,
    INovelUserContext userContext,
    ILogger<NovelService> logger,
    IModelValidator<CreateNovelRequest> createValidator,
    IModelValidator<UpdateNovelRequest> updateValidator)
{
    public async Task<IReadOnlyList<NovelSummaryResponse>> ListAsync(CancellationToken ct = default)
    {
        logger.LogInformation("Listing novels");

        return await access.VisibleNovels()
            .OrderByDescending(p => p.UpdatedAt)
            .Select(p => new NovelSummaryResponse(
                p.Id,
                p.Title,
                p.Author,
                p.Genre,
                p.Logline,
                p.TargetWordCount,
                p.Phase,
                p.Characters.Count,
                p.Chapters.Count,
                p.Chapters.Sum(c => (int?)c.WordCount) ?? 0,
                p.UpdatedAt))
            .ToListAsync(ct);
    }

    public async Task<Novel?> GetAsync(Guid id, CancellationToken ct = default)
    {
        Guard.Default(id, nameof(id));

        logger.LogInformation("Getting novel {NovelId}", id);

        var novel = await FindAsync(id, ct);
        if (novel is null) return null;

        await access.RequireAsync(id, NovelPermission.Read, ct);
        return novel;
    }

    public async Task<Novel> CreateAsync(CreateNovelRequest request, CancellationToken ct = default)
    {
        Guard.Null(request, nameof(request));
        createValidator.Validate(request).ThrowIfInvalid(logger);
        access.RequireCanCreateNovel();

        logger.LogInformation("Creating novel {Title}", request.Title);

        var novel = new Novel
        {
            Title = request.Title,
            Author = request.Author,
            Genre = request.Genre,
            Logline = request.Logline,
            Synopsis = request.Synopsis,
            Notes = request.Notes,
            TargetWordCount = request.TargetWordCount,
            OwnerId = userContext.UserId
        };

        db.Novels.Add(novel);
        await db.SaveChangesAsync(ct);
        return novel;
    }

    public async Task<Novel?> UpdateAsync(Guid id, UpdateNovelRequest request, CancellationToken ct = default)
    {
        Guard.Default(id, nameof(id));
        Guard.Null(request, nameof(request));
        updateValidator.Validate(request).ThrowIfInvalid(logger);

        logger.LogInformation("Updating novel {NovelId}", id);

        var novel = await FindAsync(id, ct);
        if (novel is null) return null;

        await access.RequireAsync(id, NovelPermission.Write, ct);

        novel.Title = Patch.Apply(novel.Title, request.Title) ?? novel.Title;
        novel.Author = Patch.Apply(novel.Author, request.Author);
        novel.Genre = Patch.Apply(novel.Genre, request.Genre);
        novel.Logline = Patch.Apply(novel.Logline, request.Logline);
        novel.Synopsis = Patch.Apply(novel.Synopsis, request.Synopsis);
        novel.Notes = Patch.Apply(novel.Notes, request.Notes);
        novel.TargetWordCount = request.TargetWordCount ?? novel.TargetWordCount;
        novel.Phase = request.Phase ?? novel.Phase;
        novel.UpdatedAt = DateTimeOffset.UtcNow;

        await db.SaveChangesAsync(ct);
        return novel;
    }

    public async Task<bool> DeleteAsync(Guid id, CancellationToken ct = default)
    {
        Guard.Default(id, nameof(id));

        logger.LogInformation("Deleting novel {NovelId}", id);

        var novel = await FindAsync(id, ct);
        if (novel is null) return false;

        await access.RequireAsync(id, NovelPermission.DeleteContent, ct);

        db.Novels.Remove(novel);
        await db.SaveChangesAsync(ct);
        return true;
    }

    private async Task<Novel?> FindAsync(Guid id, CancellationToken ct)
    {
        logger.LogDebug("Finding novel {NovelId}", id);

        var novel = await db.Novels.FirstOrDefaultAsync(p => p.Id == id, ct);
        if (novel is null)
        {
            logger.LogWarning("Novel {NovelId} not found", id);
            return novel;
        }

        logger.LogDebug("Found novel {NovelId}", id);
        return novel;
    }
}